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Use and validation of magnetic properties for differentiating nickel hyperaccumulators and non-nickel hyperaccumulators in ultramafic regions
Abstract
Nickel hyperaccumulators are plants that can absorb a large amount of Ni in their tissues. Nickel hyperaccumulators have a strong potential to be used as bioindicators in mineral explorations. Previous studies show that analysis of magnetic susceptibility has a potential to accelerate the screening of Ni hyperaccumulators. In this study, we investigated the use magnetic characterizations for screening directly Ni hyperaccumulators and non-Ni hyperaccumulators from ultramafic regions. For comparison, the characterization of Ni hyperaccumulators was also performed on Alyssum murale and Alyssum corsicum, which were cultivated on lateritic soils. The metals concentrations in the tissues were determined via inductively coupled plasma optical emission spectroscopy analysis, atomic absorption spectroscopy analysis, and X-ray fluorescence analysis. The magnetic characterizations were conducted by magnetic susceptibility measurement, acquisition of hysteresis curves, and analysis of the thermomagnetic properties. The results showed that the concentration of Ni in A. murale and A. corsicum were correlated to the magnetic susceptibility values. Concurrently, all samples had negative magnetic susceptibility values were non-Ni hyperaccumulators. Two new species of Ni hyperaccumulators were found in Halmahera and Sulawesi and have high potential for use in phytoremediation, phytomining or mineral exploration.
... Environmental monitoring using magnetic susceptibility measurements is one method that has been used extensively to monitor the environments of various regional objects such as lakes (Yunginger et al., 2018), rivers (Jin et al., 2019;Mariyanto et al., 2019;Sudarningsih et al., 2017;Togibasa et al., 2018), and the sea (Li et al., 2020). Objects that can be analyzed include sediments (Yunginger et al., 2018), rock (Reyes et al., 2013), soils (Kanu et al., 2014;Novala et al., 2016), and plants (Hamdan et al., , 2020. For sediments, magnetic susceptibility measurements have been carried out in environmental monitoring, such as with topsoil (Reyes et al., 2013), lake sediments (Bao et al., 2011;Yunginger et al., 2018), marine sediments, and river sediments (Mariyanto et al., 2019;Sudarningsih et al., 2017). ...
... B n is a point on the absence of anthropogenic activity (Haris et al., 2017), and it is station 1 in Fig. 1. Correlation analyses used Pearson's correlation (Hamdan et al., 2020). The turbidity of water was determined by a turbidity meter (Amtast Amt21). ...
Estuaries have very complex mechanisms because they are influenced by seawater intrusion, which causes enrichment of contaminants in the maximum turbidity area. Magnetic susceptibility measurements have been used for monitoring a wide variety of environments. However, there have been few studies of the magnetic properties of surface sediments from estuaries in volcanic environments in the tropics. This study investigates the magnetic properties and their correlations with the geochemistry of surface sediments in estuaries in volcanic areas and was conducted in the Krueng Aceh River, Indonesia. Measurements consist of magnetic susceptibility measurements, chemical analysis, and mineralogical analysis. Measurements of magnetic susceptibilities were performed using a Bartington MS2 instrument with an MS2B sensor using frequencies of 460 and 46 kHz. X-ray fluorescence (XRF) and energy-dispersive spectroscopy (EDS) were used to identify elements in the sediments. Scanning electron microscopy (SEM) analysis was used to analyze sediment grains. X-ray diffraction (XRD) analysis was used to determine mineral contents. For the first time, χLF/χFD ratios were found to be an obvious parameter for identifying areas of sediment traps and metal enrichment in the estuary turbidity maxima (ETM) zone. The magnetic properties carried by volcanic rock minerals consist of pigeonite and enstatite. These two minerals have not been previously considered as carriers of sediments with magnetic properties when monitoring heavy metal enrichment in urban rivers. These results provide an extension of the use of magnetic susceptibility measurements in environmental studies, particularly in estuary river environments in volcanic areas such as the Krueng Aceh River, Indonesia.
Lateritic soil is a prospective source of metals termed critical or strategic metals due to their use in high-technology industries. Critical metals include rare earth elements (REEs). In this study, two profiles of lateritic outcrops from the Ni-producing area of Southeast Sulawesi in Indonesia were sampled for magnetic susceptibility as well µ-XRF analyses to identify how the concentration of critical metals changed during pedogenesis. The results show that there are three different patterns from the bottom layer up. The first pattern is enrichment experienced by Sc, La, Cr, and Ti. The second pattern is depletion experienced by Ni, Nd, and Ho. The third pattern is the localization of high concentration at a certain depth, as experienced by Co, Ce, and V. The concentration of certain critical metals correlates either positively or negatively with magnetic susceptibility, inferring that magnetic susceptibility might be used as a proxy indicator for critical metal concentration in lateritic soil.
Nickel (Ni) is an indispensable component of the urease enzyme that plays a key role in urea/nitrogen metabolism in plants. Therefore, it has been designated as an essential micronutrient, the latest one included in the list of elements required in trace amount. Plants rarely face the deficiency of this micronutrient because the seed possesses a concentration that is sufficient for the entire life span of the plant. However, its absence or deficient concentration is manifested in characteristic disorders or deficiency diseases called leaf-burn disease, leaf-tip necrosis, and mouse-ear disease. Excess concentrations of Ni also inflict different physiological and metabolic alterations such as plant growth inhibition, disturbed uptake and translocation of water and mineral nutrients, and slowing of the attributes related to photosynthesis including stomatal functioning, and enzyme inhibition. Ni also generates oxidative stress and stimulates both the enzymatic and nonenzymatic antioxidant system. To cope with the stress generated by excess Ni, plants have evolved some peculiar strategies such as the prevention of influx or exclusion by the plasma membrane, chelation by phytochelatins, metalothionines, and nicotinamine. The complexed Ni is subsequently compartmentalized into the vacuole. These tolerance strategies help in the accumulation of large amount Ni by the process called hyperaccumulation and subsequently in the management of the Ni polluted soil. All these aspects are presented here comprehensively to discuss the effects of low and excess levels of Ni on the plant growth and development, and metabolism as well as the tolerance strategies in plants. In addition to this, the extent of extraction of Ni by the hyperaccumulators is also presented.
Metal hyperaccumulation is a rare and fascinating phenomenon, whereby plants actively accumulate high concentrations of metal ions in their above-ground tissues. Enhanced uptake and root-to-shoot translocation of specific metal ions coupled with an increased capacity for detoxification and sequestration of these ions are thought to constitute the physiological basis of the hyperaccumulation phenotype. Nickel hyperaccumulators were the first to be discovered and are the most numerous, accounting for some seventy-five percent of all known hyperaccumulators. However, our understanding of the molecular basis of the physiological processes underpinning Ni hyperaccumulation has lagged behind that of Zn and Cd hyperaccumulation, in large part due to a lack of genomic resources for Ni hyperaccumulators. The advent of RNA-Seq technology, which allows both transcriptome assembly and profiling of global gene expression without the need for a reference genome, has offered a new route for the analysis of Ni hyperaccumulators, and several such studies have recently been reported. Here we review the current state of our understanding of the molecular basis of Ni hyperaccumulation in plants, with an emphasis on insights gained from recent RNA-Seq experiments, highlight commonalities and differences between Ni hyperaccumulators, and suggest potential future avenues of research in this field.
Main conclusion
Fe uptake machinery of chloroplasts prefers to utilise Fe(III)–citrate over Fe–nicotianamine complexes.
Iron uptake in chloroplasts is a process of prime importance. Although a few members of their iron transport machinery were identified, the substrate preference of the system is still unknown. Intact chloroplasts of oilseed rape (Brassica napus) were purified and subjected to iron uptake studies using natural and artificial iron complexes. Fe–nicotianamine (NA) complexes were characterised by 5 K, 5 T Mössbauer spectrometry. Expression of components of the chloroplast Fe uptake machinery was also studied. Fe(III)–NA contained a minor paramagnetic Fe(II) component (ca. 9%), a paramagnetic Fe(III) component exhibiting dimeric or oligomeric structure (ca. 20%), and a Fe(III) complex, likely being a monomeric structure, which undergoes slow electronic relaxation at 5 K (ca. 61%). Fe(II)–NA contained more than one similar chemical Fe(II) environment with no sign of Fe(III) components. Chloroplasts preferred Fe(III)–citrate compared to Fe(III)–NA and Fe(II)–NA, but also to Fe(III)–EDTA and Fe(III)–o,o′EDDHA, and the Km value was lower for Fe(III)-citrate than for the Fe–NA complexes. Only the uptake of Fe(III)–citrate was light-dependent. Regarding the components of the chloroplast Fe uptake system, only genes of the reduction-based Fe uptake system showed high expression. Chloroplasts more effectively utilize Fe(III)–citrate, but hardly Fe–NA complexes in Fe uptake.
Hyperaccumulation is generally highly specific for a single element, for example nickel (Ni). The recently-discovered hyperaccumulator Glochidion cf. sericeum (Phyllanthaceae) from Malaysia is unusual in that it simultaneously accumulates nickel and cobalt (Co) with up to 1500 μg g-1 foliar of both elements. We set out to determine whether distribution and associated ligands for Ni and Co complexation differ in this species. We postulated that Co hyperaccumulation coincides with Ni hyperaccumulation operating on similar physiological pathways. However, the ostensibly lower tolerance for Co at the cellular level results in the exudation of Co on the leaf surface in the form of lesions. The formation of such lesions is akin to phytotoxicity responses described for manganese (Mn). Hence, in contrast to Ni, which is stored principally inside the foliar epidermal cells, the accumulation response to Co consists of an extracellular mechanism. The chemical speciation of Ni and Co, in terms of the coordinating ligands involved and principal oxidation state, is similar and associated with carboxylic acids (citrate for Ni and tartrate or malate for Co) and the hydrated metal ion. Some oxidation to Co3+, presumably on the surface of leaves after exudation, was observed.
Ultramafic soils are typically enriched in nickel (Ni), chromium (Cr), and cobalt (Co) and deficient in essential nutrients, making them unattractive for traditional agriculture. Implementing agromining systems in ultramafic agricultural soils represent an ecological option for the sustainable management and re-valorisation of these low-productivity landscapes. These novel agroecosystems cultivate Ni-hyperaccumulating plants which are able to bioaccumulate this metal in their aerial plant parts; harvested biomass can be incinerated to produce Ni-enriched ash or “bio-ore” from which Ni metal, Ni ecocatalysts or pure Ni salts can be recovered. Nickel hyperaccumulation has been documented in ~450 species, and in temperate latitudes these mainly belong to the family Brassicaceae and particularly to the genus Odontarrhena (syn. Alyssum pro parte). Agromining allows for sustainable metal recovery without causing the environmental impacts associated with conventional mining activities, and at the same time, can improve soil fertility and quality and provide essential ecosystem services. Parallel reductions in Ni phytotoxicity over time would also permit cultivation of conventional agricultural crops. Field studies in Europe have been restricted to Mediterranean areas and these only evaluated the Ni-hyperaccumulator Odontarrhena muralis s.l. Two recent EU projects (Agronickel and LIFE-Agromine) have established a network of agromining field sites in ultramafic regions with different edapho-climatic characteristics across Albania, Austria, Greece and Spain. Soil and crop management practices are being developed so as to optimize the Ni agromining process; field studies are evaluating the potential benefits of fertilization regimes, crop selection and cropping patterns, and bioaugmentation with plant-associated microorganisms. Hydrometallurgical processes are being up-scaled to produce nickel compounds and energy from hyperaccumulator biomass. Exploratory techno-economic assessment of Ni metal recovery by pyrometallurgical conversion of O. muralis s.l. shows promising results under the condition that heat released during incineration can be valorized in the vicinity of the processing facility.
Three tetrahedral coordination compounds formed from Ni(II), Cu(II), and Zn(II) transition-metal ions with ON-donor, (2-aminophenol) ligand (L), were synthesized and characterized by Fourier-transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, elemental analysis, and magnetic susceptibility measurements. The magnetic properties revealed that the NiL2 and CuL2 complexes were paramagnetic while the ZnL2 complex was diamagnetic. Also, photodegradation of methylene blue as model organic pollutant by the synthesized complexes was studied based on an oxidation process under visible-light irradiation. The results showed that the photocatalytic activity of the Cu complex was greater compared with the Ni and Zn complexes, with degradation efficiency of 100, 85, and 60 %, respectively, after 30 min of irradiation in this condition. Thus, the Cu (bis-chelate) complex is more efficient, produces higher yield, is easily produced, and represents a more stable heterogeneous photocatalyst for degradation of organic dyes such as methylene blue.
Lake Limboto is one of the major lakes in Sulawesi, Indonesia. It is currently undergoing serious degradation due to population pressure. As more residential areas have been established around the lake, the sedimentation rate has increased because of the contribution of anthropogenic particles. In this study, the lithogenic and anthropogenic components in surface sediments from 17 points in the lake were studied and identified using a combination of magnetic and geochemical analyses. The results showed that although the magnetic susceptibility values in R (residential) and NR (non-residential) areas were relatively similar, the values of saturation isothermal remanent magnetization (SIRM) as well as those of SIRM/χLF differed significantly, implying that the magnetic characteristics of the lithogenic component (in the NR area) differ from those of the anthropogenic component (in the R area). The discrepancy between the anthropogenic and lithogenic contributions was further supported by trace metals and rare earth element (REE) contents. Sediment samples in the R area contained higher levels of Mn, La, Pr, and Gd, while in the NR area they contained higher levels of Fe, Sc, Nd, and Ce. The magnetic susceptibility also correlated strongly with Fe, Cu, Zn, and Mn contents in the NR area. A similar correlation was not observed in the R area. The results above imply that a combination of magnetic and geochemical analyses can successfully differentiate lithogenic and anthropogenic components or contributions in lake sediments.
Background Hyperaccumulator plants are unusual plants that accumulate particular metals or metalloids, such as nickel, zinc, cadmium and arsenic, in their living tissues to concentrations that are hundreds to thousands of times greater than what is normal for most plants. The hyperaccumulation phenomenon is rare (exhibited by less than 0.2% of all angiosperms), with most of the ~500 hyperaccumulator species known globally for nickel.
Scope This review highlights the contemporary understanding of nickel hyperaccumulation processes, which include root uptake and sequestration, xylem loading and transport, leaf compartmentation and phloem translocation processes.
Conclusions Hyperaccumulator plants have evolved highly efficient physiological mechanisms for taking up nickel in their roots followed by rapid translocation and sequestration into the aerial shoots. The uptake of nickel is mainly involved with low affinity transport systems, presumably from the ZIP family. The presence of high concentrations of histidine prevents nickel sequestration in roots. Nickel is efficiently loaded into the xylem,where it mainly presents as Ni2+. The leaf is the main storage organ, which sequestrates nickel in non-active sites, e.g. vacuoles and apoplast. Recent studies show that phloem translocates high levels of nickel, which has a strong impact on nickel accumulation in young growing tissues.
The Citarum River has a volcanic catchment area in West Java Province, and is one of the nationally strategic rivers in tropical Indonesia due to its roles in water supply and in power generation. The river is economically important, but it is also polluted by industrial, agricultural, and residential wastes. Suspended sediment samples were collected along a certain section of the Citarum River, starting in Balekambang through the area of Bandung Regency to the downstream village of Nanjung, where the river is dammed. Similar samples were also collected from seven tributaries of the Citarum River. Magnetic and heavy metal analyses show that unlike river sediments from a non-volcanic catchment area in temperate climates, magnetic susceptibility values tend to decrease downstream, showing that the magnetic minerals in the upstream area are mostly lithogenic in origin, containing more Fe-bearing minerals compared to those in tributary samples which are anthropogenic in origin. Anthropogenic pollution is also represented by the increase of Zn content along the river. The results suggest that applying magnetic methods for monitoring river pollution in the tropics or in the volcanic areas should be carefully analyzed and interpreted.
Globally, ultramafic outcrops are renowned for hosting floras with high levels of endemism, including plants with specialised adaptations such as nickel or manganese hyperaccumulation. Soils derived from ultramafic regoliths are generally nutrient-deficient, have major cation imbalances, and have concomitant high concentrations of potentially phytotoxic trace elements, especially nickel. The South and Southeast Asian region has the largest surface occurrences of ultramafic regoliths in the world, but the geoecology of these outcrops is still poorly studied despite severe conservation threats. Due to the paucity of systematic plant collections in many areas and the lack of georeferenced herbarium records and databased information, it is not possible to determine the distribution of species, levels of endemism, and the species most threatened. However, site-specific studies provide insights to the ultramafic geoecology of several locations in South and Southeast Asia. The geoecology of tropical ultramafic regions differs substantially from those in temperate regions in that the vegetation at lower elevations is generally tall forest with relatively low levels of endemism. On ultramafic mountaintops, where the combined forces of edaphic and climatic factors intersect,
obligate ultramafic species and hyperendemics often occur. Forest clearing, agricultural development, mining,
and climate change-related stressors have contributed to rapid and unprecedented loss of ultramafic-associated habitats in the region. The geoecology of the large ultramafic outcrops of Indonesia’s Sulawesi, Obi and Halmahera, and many other smaller outcrops in South and Southeast Asia, remains largely unexplored, and should be prioritised for study and conservation.
Keywords: Adaptations, Conservation, Edaphic endemism, Edaphic flora, Extreme environments, Geobotany, Plant–soil relations, Serpentine vegetation, Ultramafic plants, Metal hyperaccumulators
Iron oxide nanoparticles are of interest in a wide range of biomedical applications due to their response to applied magnetic fields and their unique magnetic properties. Magnetization measurements in constant and time-varying magnetic field are often carried out to quantify key properties of iron oxide nanoparticles. This chapter describes the importance of thorough magnetic characterization of iron oxide nanoparticles intended for use in biomedical applications. A basic introduction to relevant magnetic properties of iron oxide nanoparticles is given, followed by protocols and conditions used for measurement of magnetic properties, along with examples of data obtained from each measurement, and methods of data analysis.
This review synthesizes contemporary understanding of Cu-Co tolerance and accumulation in plants. Accumulation of foliar Cu and Co to >300 μg g-1 is exceptionally rare globally, and known principally from the Copperbelt of Central Africa. Cobalt accumulation is also observed in a limited number of Ni hyperaccumulator plants occurring on ultramafic soils around the world. None of the putative Cu or Co hyperaccumulator plants appears to comply with the fundamental principle of hyperaccumulation as foliar Cu-Co accumulation is strongly dose-dependent. Abnormally high plant-tissue Cu concentration occurs only when plants are exposed to high soil Cu concentrations with a low shoot translocation factor. Most Cu tolerant plants are Excluders sensu Baker and therefore setting threshold values for Cu hyperaccumulation is not informative. Abnormal accumulation of Co occurs under similar circumstances in the Copperbelt of Central Africa as well as sporadically in Ni hyperaccumulators on ultramafic soils, however, Co tolerant plants behave physiologically as Indicators sensu Baker. Practical application of Cu-Co accumulator plants in phytomining is limited due to their dose-dependent accumulation characteristics, although for Co field trials may be warranted on highly Co-contaminated minerals wastes because of its relatively high metal value.
Magnetic data are reported for Prussian Blue Analogs (PBAs) of composition M3[M’(C,N)6]2.xH2O, where M = Mn, Co, Ni or Cu and M’ = Cr, Fe or Co and x is the number of water molecules per unit cell. PBAs crystallize in cubic framework structures, which consist of alternating MIIIN6 and MIIC6 octahedra. Occupancies of the octrahedra are not perfect: they may be empty and the charges are balanced by the oxygen atoms originating from guest water molecules at the lattice site (C or N site) or the interstitial site (between the octahedrals) of the unit cell. Large crystal-field splittings due to the octrahedral environment results in a combination of low- or high-spin configurations of localized magnetic bivalent and trivalent 3d moments. The magnetic susceptibility of studied PBAs follows the Curie-Weiss behavior in the paramagnetic region up to room temperature. Moreover, the data provide evidence for a long-range magnetic ground state for most metal hexacyanochromates and all metal hexacyanoferrates, while hexacyanocobaltates remain paramagnetic down to the lowest temperature measured (2 K). For all compounds, the effective magnetic moments determined from experiments were found to be in reasonable agreement with predicted combinations of high- and low-spin moments.
The genus Alyssum (Brassicaceae) contains Ni hyperaccumulators (50), many of which can achieve 30 g kg⁻¹ Ni in dry leaf. Some Alyssum hyperaccumulators are viable candidates for commercial Ni phytoremediation and phytomining technologies. It is not known whether these species secrete organic and/or amino acids into the rhizosphere to solubilize Ni, or can make use of such acids within the soil to facilitate uptake. It has been hypothesized that in fields with mixed plant species, mobilization of metals by phytosiderophores secreted by Graminaceae plants could affect Alyssum Ni, Fe, Cu, and Mn uptake. We co-cropped the Ni hyperaccumulator Alyssum murale, non-hyperaccumulator A. montanum and perennial ryegrass in a natural serpentine soil. All treatments had standard inorganic fertilization required for ryegrass growth and one treatment was compost amended. After 4 months A. murale leaves and stems contained 3600 mg kg⁻¹ Ni which did not differ significantly with co-cropping. Overall Ni and Mn concentrations were significantly higher in A. murale than in A. montanum or L. perenne. Copper was not accumulated by either Alyssum species, but L. perenne accumulated up to 10 mg kg⁻¹. A. montanum could not compete with either A. murale or ryegrass, and neither Alyssum species survived in the compost-amended soil. Co-cropping with ryegrass reduced Fe and Mn concentrations in A. murale but not to the extent of either increasing Ni uptake or affecting plant nutrition. The hypothesized Alyssum Ni accumulation in response to phytosiderophores secreted by co-cropped grass did not occur. Our data do not support increased mobilization of Mn by a phytosiderophore mechanism either, but the converse: mobilization of Mn by the Alyssum hyperaccumulator species significantly increased Mn levels in L. perenne. Tilling soil to maximize root penetration, adequate inorganic fertilization and appropriate plant densities are more important for developing efficient phytoremediation and phytomining approaches.
In the present study, we demonstrate magnetic iron (III) oxide nanoparticle (Fe2O3
NPs) uptake by the Solanum lycopersicum (S. lycopersicum) plant. The S. lycopersicum seeds
were coated with Fe2O3 NPs and allowed to germinate in moistened sand bed. The seedlings are
observed for 20 days and then it was post treated using different amounts of Fe2O3 NPs in
hydroponic solution for 10 days. The plant was allowed to grow in green house for three months
and uptake of NP through roots and translocation into different parts was studied. For this, we
have segmented the plants and incubated with 10% NaOH solution. It is found that the NPs are
deposited preferentially in root-hairs, root-tips followed by nodal and middle zone of plant. The
iron present in the whole plant was quantitatively estimated by treating dry biomass of the plant
in acid. The Fe2+/Fetotal increased with increasing concentration of NPs and >45% ferrous iron
suggests the biomineralization of NPs due to rich phytochemicals in plants. We believe the
present study is useful to build a base line data for novel applications in agri-nanotechnology
Only three elements are ferromagnetic at room temperature: the transition metals iron, cobalt and nickel. The Stoner criterion explains why iron is ferromagnetic but manganese, for example, is not, even though both elements have an unfilled 3d shell and are adjacent in the periodic table: according to this criterion, the product of the density of states and the exchange integral must be greater than unity for spontaneous spin ordering to emerge. Here we demonstrate that it is possible to alter the electronic states of non-ferromagnetic materials, such as diamagnetic copper and paramagnetic manganese, to overcome the Stoner criterion and make them ferromagnetic at room temperature. This effect is achieved via interfaces between metallic thin films and C60 molecular layers. The emergent ferromagnetic state exists over several layers of the metal before being quenched at large sample thicknesses by the material's bulk properties. Although the induced magnetization is easily measurable by magnetometry, low-energy muon spin spectroscopy provides insight into its distribution by studying the depolarization process of low-energy muons implanted in the sample. This technique indicates localized spin-ordered states at, and close to, the metal-molecule interface. Density functional theory simulations suggest a mechanism based on magnetic hardening of the metal atoms, owing to electron transfer. This mechanism might allow for the exploitation of molecular coupling to design magnetic metamaterials using abundant, non-toxic components such as organic semiconductors. Charge transfer at molecular interfaces may thus be used to control spin polarization or magnetization, with consequences for the design of devices for electronic, power or computing applications (see, for example, refs 6 and 7).
Information about multi-elemental concentrations in different plant parts of tropical Ni hyperaccumulator species has the potential to provide insight into their unusual metabolism relative to a range of essential and non-essential elements, but this information is scant in the literature. As Ni hyperaccumulation, and possibly co-accumulation of other toxic elements, has been hypothesized to provide herbivore (insect) protection, there is a need to quantify a range of these elements in plant tissues and transport fluids to at least verify the possibility of this explanation. In this study, multiple elements were analyzed in a range of different plant parts and transport fluids from Ni hyperaccumulator species collected from Sabah (Malaysia). The results show preferential accumulation of Ni in leaves over woody parts, but the highest concentrations were found in the phloem tissue (up to 7.9 % in Rinorea bengalensis) and phloem sap (up to 16.9 % in Phyllanthus balgooyi), visible by a bright green coloration in the field fresh material. The amount of Ni contained in one mature R. bengalensis tree was calculated at 4.77 kg. The high Ni concentration in the flowers of Phyllanthus securinegoides could affect insect floral visitors and pollination. High concentrations of Ni in the seeds of this species also could supply the seedling with Ni and aid in herbivory protection during the first stages of development. Foliar Ca and Ni in P. cf. securinegoides and R. bengalensis are positively correlated. Low accumulation of Ca is desirable for phytomining but concentrations of Ca are high in most Ni hyperaccumulators examined, and this could have consequences for the economic viability of Ni extraction from bio ore if these species were to be used as 'metal crops'.
Ultramafic Vertisols cover large areas in Albania and offer opportunities for phytomining. We undertook a field experiment with native Alyssum murale on two representative Vertisols distant from 20 km (Pojskë and Domosdovë, Albania) to test the effect of planting density (transplanted seedlings) on a phytomining cropping system. Both areas were cleared in late summer 2012 and then ploughed and the soils characterized. 0.5 ha at Domosdovë was planted with local native seedlings at a density of 6 plants m-2 in September 2012., Spontaneous plants that had germinated in spring 2012 were left to grow without any competition from other plants on a second 0.1-ha plot at Domosdovë. All plots were weeded manually in the autumn of 2012 and in spring 2013. Individual plants occupied c. 1 m2 at maturity. At Pojskë, 0.3 ha was also planted in September 2012 with local native seedlings of A. murale at a density of 4 plants m-2. Plants grown at initial densities of 4 and 6 plants m-2 did not fully cover the ground; gaps were filled in naturally by a second spontaneous generation of A. murale seedlings (recruits) which had germinated in autumn 2012. Other weeds were eliminated with herbicides. At Domosdovë, at densities of 1 and 6 plants m-2 and at Pojskë for 4 plants m-2, the biomass yield was 10, 5 and 10 t ha-1, respectively. Phytoextracted Ni was 77, 41 and 112 kg ha-1. We suggest that a density of 4 plants m-2 is suitable for phytoextraction with native populations of A. murale. Alyssum murale can be a weed to itself and lower the Ni phytoextraction yield. Plants responded differently in their native environment than in previous field trials in North America
Large ultramafic areas exist in Albania, which could be suitable for phytomining with native Alyssum murale. We undertook a five-year field experiment on an ultramafic Vertisol, aimed at optimizing a low-cost Ni-phytoextraction crop of A. murale which is adapted to the Balkans. The following aspects were studied on 18-m(2) plots in natural conditions: the effect of (i) plant phenology and element distribution, (ii) plant nutrition and fertilization, (iii) plant cover and weed control and (iv), planting technique (natural cover vs. sown crop). The optimal harvest time was set at the mid-flowering stage when Ni concentration and biomass yield were highest. The application of N, P, and K fertilizers, and especially a split 100-kg ha(-1) N application, increased the density of A. murale against all other species. It significantly increased shoot yield, without reducing Ni concentration. In natural stands, the control of graminaceous weeds required the use of an anti-monocots herbicide. However, after the optimization of fertilization and harvest time, weed control procured little benefit. Finally, cropping sown A. murale was more efficient than enhancing native stands and gave higher biomass and phytoextraction yields; biomass yields progressively improved from 0.3 to 9.0 t ha(-1) and phytoextracted Ni increased from 1.7 to 105 kg ha(-1).
Nickel is an economically important metal and phytotechnologies are being developed to limit the impact of nickel mining on
the environment. More than 300 plant species are known to hyperaccumulate nickel. However, our knowledge of the mechanisms
involved in nickel accumulation in plants is very limited because it has not yet been possible to study these hyperaccumulators
at the genomic level. Here, we used next-generation sequencing technologies to sequence the transcriptome of the nickel hyperaccumulator
Psychotria gabriellae of the Rubiaceae family, and used yeast and Arabidopsis as heterologous systems to study the activity of identified metal transporters. We characterized the activity of three metal
transporters from the NRAMP and IREG/FPN families. In particular, we showed that PgIREG1 is able to confer nickel tolerance when expressed in yeast and in transgenic plants, where it localizes in the tonoplast.
In addition, PgIREG1 shows higher expression in P. gabriellae than in the related non-accumulator species Psychotria semperflorens. Our results designate PgIREG1 as a candidate gene for nickel tolerance and hyperaccumulation in P. gabriellae. These results also show how next-generation sequencing technologies can be used to access the transcriptome of non-model
nickel hyperaccumulators to identify the underlying molecular mechanisms.
Rock magnetic methods have increasingly been applied in many fields of study as they are relatively easy, fast, non-destructive and affordable. We present some examples of such applications in soil and environmental studies that had been conducted at InstitutTeknologi Bandung by its faculty members and graduate students. After a brief introduction on fundamentals of rock magnetism, we described our study on lateritic soil from Pomalaa, which show that magnetic properties correlate well with soil horizons suggesting that magnetic methods could be used as additional tools in pedogenic studies. We also described our study in leachate sludge samples from two sites near Bandung showing that leachate sludge samples are reasonably magnetic and that correlation between magnetic parameters and heavy metal content might exist. Supported by other analyses, such as SEM and XRD, we were also able to identify the sources of magnetic grains in leachate sludge.
Aims
Past studies have demonstrated that hyperaccumulators absorb Ni from the same labile pools in soil as normal plant species. This study investigated whether the Ni hyperaccumulator plant Alyssum corsicum possesses distinct extraction mechanisms for different Ni species present in soils. Different Ni species have different solubilities and potential bioavailabilities to roots.
Methods
Uptake of Ni in shoots of A. corsicum was analyzed after four weeks of plant growth in nutrient solution with 17 different Ni compounds or soils.
Results
The results indicate that Ni uptake is related to Ni solubility and plant transpiration rate. The most soluble compounds had the highest Ni uptake, with the exception of Ni3(PO4)2, Ni phyllosilicate, Ni-acid birnessite which showed a low solubility but a relatively high plant uptake and transpiration rate. In serpentine soils and insoluble NiO plant transpiration rate was high but uptake was very low and statistically comparable to the control.
Conclusions
It appears that Ni uptake is driven by convection, which depends on the initial concentration of Ni in solution and the plant transpiration rate.
Hyperaccumulators are being intensely investigated. They are not only interesting in scientific context due to their “strange” behavior in terms of dealing with high concentrations of metals, but also because of their use in phytoremediation and phytomining, for which understanding the mechanisms of hyperaccumulation is crucial. Hyperaccumulators naturally use metal accumulation as a defense against herbivores and pathogens, and therefore deal with accumulated metals in very specific ways of complexation and compartmentation, different from non-hyperaccumulator plants and also non-hyperaccumulated metals. For example, in contrast to non-hyperaccumulators, in hyperaccumulators even the classical phytochelatin-inducing metal, cadmium, is predominantly not bound by such sulfur ligands, but only by weak oxygen ligands. This applies to all hyperaccumulated metals investigated so far, as well as hyperaccumulation of the metalloid arsenic. Stronger ligands, as they have been shown to complex metals in non-hyperaccumulators, are in hyperaccumulators used for transient binding during transport to the storage sites (e.g., nicotianamine) and possibly for export of Cu in Cd/Zn hyperaccumulators [metallothioneins (MTs)]. This confirmed that enhanced active metal transport, and not metal complexation, is the key mechanism of hyperaccumulation. Hyperaccumulators tolerate the high amount of accumulated heavy metals by sequestering them into vacuoles, usually in large storage cells of the epidermis. This is mediated by strongly elevated expression of specific transport proteins in various tissues from metal uptake in the shoots up to the storage sites in the leaf epidermis. However, this mechanism seems to be very metal specific. Non-hyperaccumulated metals in hyperaccumulators seem to be dealt with like in non-hyperaccumulator plants, i.e., detoxified by binding to strong ligands such as MTs.
Nanomaterials are structures whose exceptionality is based on their large surface, which is closely connected with reactivity and modification possibilities. Due to these properties nanomaterials are used in textile industry (antibacterial textiles with silver nanoparticles), electronics (high-resolution imaging, logical circuits on the molecular level) and medicine. Medicine represents one of the most important fields of application of nanomaterials. They are investigated in connection with targeted therapy (infectious diseases, malignant diseases) or imaging (contrast agents). Nanomaterials including nanoparticles have a great application potential in the targeted transport of pharmaceuticals. However, there are some negative properties of nanoparticles, which must be carefully solved, as hydrophobic properties leading to instability in aqueous environment, and especially their possible toxicity. Data about toxicity of nanomaterials are still scarce. Due to this fact, in this work we focused on studying of the effect of magnetic nanoparticles (NPs) and modified magnetic nanoparticles (MNPs) on tobacco BY-2 plant cell suspension culture. We aimed at examining the effect of NPs and MNPs on growth, proteosynthesis - total protein content, thiols - reduced (GSH) and oxidized (GSSG) glutathione, phytochelatins PC2-5, glutathione S-transferase (GST) activity and antioxidant activity of BY-2 cells. Whereas the effect of NPs and MNPs on growth of cell suspension culture was only moderate, significant changes were detected in all other biochemical parameters. Significant changes in protein content, phytochelatins levels and GST activity were observed in BY-2 cells treated with MNPs nanoparticles treatment. Changes were also clearly evident in the case of application of NPs. Our results demonstrate the ability of MNPs to negatively affect metabolism and induce biosynthesis of protective compounds in a plant cell model represented by BY-2 cell suspension culture. The obtained results are discussed, especially in connection with already published data. Possible mechanisms of NPs' and MNPs' toxicity are introduced.
The North Puruliya Shear zone (NPSZ) is characterized by occurrence of mafic-ultramafic rocks aligned parallel to the shear
zone, intruding the high grade Proterozoic rocks of Chhotanagpur Gneissic Complex. The ultramafic rocks occur as small lenses,
pockets, veins, thin dykes and are intimately associated with mafic (gabbro, norite) rocks. Pyroxenites (viz. olivine websterite,
websterite, plagioclase websterite) and hornblendite are the two important members of the ultramafic rocks containing clinopyroxene,
orthopyroxene, olivine, plagioclase, amphibole, phlogopite and ilmenite. The mafic-ultramafic rocks show evidence of shearing
and retrogressive metamorphism. Linear correlation of chemical attributes suggests fractionation-controlled magmatic differentiation.
Enrichment of LILE and LREE in the mafic-ultramafic suite suggests an enriched mantle source and pronounced negative Eu-anomalies
in all the rock types except hornblendite suggest fractionation of plagioclase under low fO2 condition. Progressive iron enrichment trend in rocks of the mafic-ultramafic suite also indicate magmatic differentiation
under low fO2 condition. Early fractionation and accumulation of clinopyroxene and plagioclase from a basaltic magma may have given rise
to the ultramafic rocks of the area. Little change in the Nb/Zr and Ce/Zr ratios of ultramafic and mafic rocks (except alkali
norite) strongly support low crustal contamination. A few samples of norite and gabbro-norites appeared to be variably contaminated
by a crustal component or affected by late granitic intrusion resulting in enrichment of alkali in the former.
Ultramafic outcrops are widespread in Albania and host several Ni hyperaccumulators (e.g., Alyssum murale Waldst. & Kit.). A field experiment was conducted in Pojske (Eastern Albania), a large ultramafic area in which native A. murale was cultivated. The experiment consisted in testing the phytoextraction potential of already installed natural vegetation
(including A. murale) on crop fields with or without suitable fertilisation. The area was divided into six 36-m2 plots, three of which were fertilised in April 2005 with (NPK+S). The soil (Magnesic Hypereutric Vertisol) was fully described
as well as the mineralogy of horizons and the localisation of Ni bearing phases (TEM-EDX and XRD). Ni availability was also
characterised by Isotopic Exchange Kinetics (IEK). The flora was fully described on both fertilised and unfertilised plots
and the plant composition (major and trace elements) and biomass (shoots) harvested individually were recorded.
The soil had mainly two Ni-bearing phases: high-Mg smectite (1.3% Ni) and serpentine (0.7% Ni), the first one being the source
of available Ni. Ni availability was extremely high according to IEK and confirmed by Ni contents in Trifolium nigriscens Viv. reaching 1,442mgkg−1 (A new hyperaccumulator?). Total biomass yields were 6.3tha−1 in fertilised plots and 3.2tha−1 in unfertilised plots with a highly significant effect: fertilisation increased dramatically the proportion of A. murale in the plots (2.6tha−1 vs. 0.2tha−1). Ni content in the shoots of A. murale reached 9,129mgkg−1 but metal concentration was not significantly affected by fertilisation. Phytoextracted Ni in total harvest reached 25kg
Niha−1 on the fertilised plots. It was significantly lower in unfertilised plots (3kg Niha−1). Extensive phytomining on such sites could be promising in the Albanian context by domesticating already installed natural
populations with fertilisation.
Indonesiahas one of the largest surface expressions of ultramafic rocks on Earthand in parallel hosts one of the most species-rich floras. Despite the extensive knowledge of the botanical diversity and the chemistry of thesesubstrates, until recently the records for nickel hyperaccumulators in the region have been scant.Identification of native local hyperaccumulator species is the critical initial step for phytomining as these species match ambient bioclimatic, geochemical and physiological conditions. Prior to this research just 11nickelhyperaccumulators were known from Indonesia.Thisfield-basedinvestigation at Weda Bayrevealed the existence of 13 nickel and two cobalthyperaccumulators. Phylogenetic affinityfor nickel hyperaccumulation is diverse and spans several orders but was most frequent in the Malpighiales as in other ultramafic regions of Southeast Asia.In contrast to global patterns, hyperaccumulation was infrequent in the Phyllanthaceae.
The association of fine grained Mg-Ni silicates with oxy-hydroxides in laterites and saprolites represents challenges for ore processing, in particular, in nickel enrichment. The Weda Bay nickel deposit in Indonesia is a typical example of these complex ores, where clays such as nontronites develop on polyphase serpentinite as protolith. Thus, ores at
Weda Bay have a very fine textured and complex mineralogy, which requires a comprehensive mineralogical identification through the use of a series of different types of analytical approaches (i.e. macroscopic and microscopic methods including SEM equipped with energy dispersive X-ray spectrometry (EDS), Raman spectroscopy, Infrared and X-ray fluorescence spectroscopy, and QEMSCAN® mapping). Nickel rich saprolites were found to be principally composed of several types of Mg Ni serpentines, quartz, clays (nontronite in particular) and little amounts of iron hydroxides. Besides, some parts of the deposit were characterized by the development of nontronites at the interface between the saprolite and the limonite zone. Above this zone, the limonite zone is dominated by iron hydroxides as expected, which replace all earlier silicates including serpentine, and contains a significant amount of nickel. The representative composite ore sample contains several nickel bearers with variable nickel grade of 2 to 3%.
Exceptionally richer phases such as polygonal Fe (Ni)-rich serpentine were also found with nickel grade of 5 to 10%.Serpentine types as well as other newly formed silicates such as Fe-Mg-(Ni) smectites, are intimately mixed, preventing any mineral separation. Therefore, the only phases which can be separated are quartz and magnetite. This complicates the upgrading of nickel in Weda Bay laterite ore.
Metal hyperaccumulator plants represent a unique biological resource for scientific research and practical applications. Though essential, however, an adequate knowledge of the systematics of these plants is often missing. This is the case of Odontarrhena, a large but taxonomically critical group of nickel hyperaccumulators from Eurasia. We present a study on this genus in Albania, to fill a gap in our knowledge of this group from a major centre of diversity of metallicolous flora, and to contribute updated information to the Global Hyperaccumulator Database. Morphological and karyological analyses of material from field collections across all major serpentine outcrops in the country, in different years and seasons, allowed to delimit seven taxa: O. albiflora, O. chalcidica, O. moravensis, O. sibirica, O. decipiens, O. smolikana subsp. glabra and O. rigida. The three latter taxa have been long neglected and were resurrected in view of their clear distinctness, while commonly accepted taxa such as O. bertolonii subsp. scutarina and O. markgrafii were reduced to synonymy of O. chalcidica due to the lack of consistent differentiation. Polyploidy was prevalent, while diploid complements were typical of the two vicariant endemics O. rigida and O. moravensis. Types are indicated or newly designated for each entity, and nomenclatural issues are addressed based on in-depth studies of literature and herbarium material. Revised descriptions, phenology, habitat and distribution data are given for each taxon, as well as original iconographies and chromosome counts. A revised identification key is provided. Shoot nickel concentrations were determined to assess accumulation levels of taxa and populations in natural conditions and their potential for phytoextraction of this metal from the soil. With ca. 23000 and 17000 µg of Ni g⁻¹of shoot dry weight, respectively, the tetraploids O. chalcidica and O. decipiens were the most promising candidates, especially the latter for its robust habit.
We have synthesized three new cobalt based inorganic-organic hybrid materials by solvothermal method, these structure have either angular or linear trimeric cobalt cluster as a secondary building unit. In case of compounds 1 and 2, the cobalt centers were corner shared through common bridging –OH group to form the triangular cluster. Interestingly in compound 1, the monomeric cobalt center is linked with framework while in compound 2 the monomeric cobalt unit is trapped inside the pore of the framework. In compound 3, the cobalt centers are corner shared to form the linear trimeric cluster. These trimeric cobalt clusters are connected through BTB ligands to form two-dimensional coordination polymer structure. All three structures have common BTB (1,3,5-Tris(4-carboxyphenyl)benzene) ligand, whereas in case of compound 1 and 2, BPE (1,2-bis (4-pyridyl) ethane) and for 3, DPB (1,4-Di(4-pyridyl)benzene) have been used as co-ligand. The magnetic measurements revealed the large and positive values of θCW in compounds 1 and 2. This implies that the dominant interaction between the Co spins are antiferromagnetic in nature. In case of compound 3, the structure is quite different from the other two compounds. In compound 3 the coupling between the Co-atoms drastically reduce compared to compounds 1 and 2, respectively, resulting in a paramagnetic behavior. We have also measured the optical band gap energy for all three compounds and results show that the band gap is relatively low and it is in the range of 1.82 eV to 1.89 eV.
Introduction of non-native trees is one of the major threats to ecosystem integrity and biodiversity. Stands of maritime pine (Pinus pinaster Ait.) introduced decades ago represent a threat to the specialized plant communities of serpentine outcrops in Italy. This study investigates the effects of such invasions at the community and species level, based on vegetation sampling in three selected sites with comparable environmental conditions. Pine cover caused a decrease of ?-diversity by lowering the species evenness of the community, though species richness was not negatively affected. Compositional changes between the two habitats were significant but not clearly associated with a decrease in taxonomic distinctness in the pine stands. As many as nine indicator species were found in the open vegetation, along with the obligate endemics Odontarrhena bertolonii and Armeria denticulata. Both of them declined in the pine stands. Here, an increase in the phytoavailable nickel fraction was associated with a decrease in total nickel concentration in the soil, via mobilization of the metal caused by lowering of pH induced by the conifer litter. The nickel-hyperaccumulator O. bertolonii was able to maintain high metal concentrations in the shoots despite a decrease in root concentration, resulting in a higher shoot/root ratio in the pine stands (~20). Conversely, shoot/root ratio in the non-accumulator Plantago holosteum was <1 and not affected by the conifer, as well as its abundance in this anthropogenic habitat. Contrasting responses of the two species were likely due to their different sensitivity to modified light and soil conditions, whereas stability of shoot nickel-concentration in O. bertolonii did not support increased predation by natural enemies as one of the causes for its decline under the conifer. Progressive thinning of these stands is advocated to limit soil nickel mobilization and to restore a unique ecosystem with its endemic metallophytes.
Absence of a single smoking-gun experiment to identify a quantum spin liquid, has kept their characterisation difficult till date. Featureless dc magnetic susceptibility and large antiferromagnetic frustration are always considered as the essential pointers to these systems. However, we show that the amount of frustration estimated by using generalised Curie-Weiss law on these susceptibility data are prone to errors and thus should be dealt with caution. We measure and analyse susceptibility data of Ba3ZnIr2O9, a spin orbital liquid candidate and Gd2O3, a 1.5 K antiferromagnet and show the distinguishing features between them. A continuous and significant change in Curie and Weiss constants is seen to take place in Ba3ZnIr2O9 and other reported spin liquids with the change in the range of fitting temperatures showing the need of a temperature ‘range-of-fit’ analysis before commenting on the Weiss constants of spin liquids. The variation observed is similar to fluctuations among topological sectors persisting over a range of temperature in spin-ice candidates. On the other hand, even though we find correlations to exist at even 100 times the ordering temperature in Gd2O3, no such fluctuation is observed which may be used as an additional distinguishing signature of spin liquids over similarly featureless correlated paramagnets.
We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hypperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica.
Compost technology can be utilized for bioremediation of contaminated soil using the active microorganisms present in the matrix of contaminants. This study examined bioremediation of industrially polluted soil using the compost and plant technology. Soil samples were collected at the vicinity of three industrial locations in Ogun State and a goldmine site in Iperindo, Osun State in March, 2014. The compost used was made from cow dung, water hyacinth and sawdust for a period of twelve weeks. The matured compost was mixed with contaminated soil samples in a five-ratio pot experimental design. The compost and contaminated soil samples were analyzed using the standard procedures for pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), phosphorus, exchangeable cations (Na, K, Ca and Mg) and heavy metals (Fe, Mn, Cu, Zn and Cr). Kenaf (Hibiscus cannabinus) seeds were also planted for co-remediation of metals. The growth parameters of Kenaf plants were observed weekly for a period of one month. Results showed that during the one-month remediation experiment, treatments with 'compost-only' removed 49±8% Mn, 32±7% Fe, 29±11% Zn, 27±6% Cu and 11±5% Cr from the contaminated soil. On the other hand, treatments with 'compost+plant' remediated 71±8% Mn, 63±3% Fe, 59±11% Zn, 40±6% Cu and 5±4% Cr. Enrichment factor (EF) of metals in the compost was low while that of Cu (EF=7.3) and Zn (EF=8.6) were high in the contaminated soils. Bioaccumulation factor (BF) revealed low metal uptake by Kenaf plant. The growth parameters of Kenaf plant showed steady increments from week 1 to week 4 of planting.
This essay traces the development of geochemical exploration from its early beginnings in the modern era during the 1930s, concentrating especially in its application to deeply weathered terrain in the tropics and sub-tropics. Following promising results obtained in temperate regions in North America and Europe, test orientation surveys were conducted to see whether similar procedures were applicable in the tropics, where conventional geological prospecting was largely precluded due to the extensive cover of a deep lateritic regolith and consequent lack of outcrop. After initial work in Sierra Leone and Nigeria, the emphasis transferred to East Africa in the 1950s and 1960s, aimed principally at Cu exploration. Many of the basic principles for exploration in dominantly residual, free-draining terrain were quickly established in this period. Exploration in terrains with more complex weathering histories, however, raised a number of difficulties due to leaching and secondary concentrations of elements, problems in selecting and identifying appropriate sample media, and extensive transported overburden. These were encountered especially in more arid regions in Australia and Africa during exploration for Ni and Au during the 1970s and 1980s. This led to a change in approach, placing weathering and geochemical dispersion in the context of regolith and landscape evolution -a return to the early concept of landscape geochemistry. The 3D expression of mineralization in the landscape is depicted as empirical conceptual models, that account for both relict features and active processes, and portray element associations, dispersion mechanisms and host materials. They also indicate suitable sample media, sampling intervals and procedures for analysis and interpretation.
Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.
Double electron electron resonance (DEER) is an attractive technique that is utilized for gaining insight into protein structure and dynamics via nanometer scale distance measurements. The most commonly used paramagnetic tag in these measurements is a nitroxide spin label, R1. Here, we present the application of two types of high-affinity Cu(2+) chelating tags, based on the EDTA and cyclen metal-binding motifs as alternative X-band DEER probes, using the B1 immunoglobulin-binding domain of protein G (GB1) as a model system. Both types of tags have been incorporated into a variety of protein secondary structure environments and exhibit high spectral sensitivity. In particular, the cyclen-based tag displays distance distributions with comparable distribution widths and most probable distances within 1 Å to 3 Å when compared to homologous R1 distributions. The results display the viability of the cyclen tag as an alternative to the R1 side-chain for X-band DEER distance measurements in proteins.
This paper reports the paramagnetic behavior of Mn doped ZnO co-doped with rare earth (Gd and Sm) atoms. The formation of secondary rare earth oxides (Gd2O3 and Sm2O3) is confirmed from the X-ray diffraction patterns. The rare earth oxides in the system forbids the grain growth and interconnection between the grains. The weak link between the grains suppresses the long range exchange interaction between the Mn ions and hence, reduces the ferromagnetic ordering. Owing to the large mismatch between ionic radii of rare earth and transition metal atoms inside the matrix, the rare earth element cannot contribute to promote ferromagnetic behavior in Mn doped ZnO, irrespective of their high individual magnetic moments.
Phytostabilization involves the establishment of a plant cover on the surface of the contaminated sites with the aim of reducing the mobility of contaminants within the vadose zone through accumulation by roots or immobilization within the rhizosphere, thereby reducing off-site contamination. The process includes transpiration and root growth that immobilizes contaminants by reducing leaching, controlling erosion, creating an aerobic environment in the root zone, and adding organic matter to the substrate that binds the contaminant. Microbial activity associated with the plant roots may accelerate the degradation of organic contaminants such as pesticides and hydrocarbons to nontoxic forms. Phytostabilization can be enhanced by using soil amendments that immobilize metal(loid)s combined with plant species that are tolerant of high levels of contaminants and low-fertility soils or tailings. Although this technology is effective in the containment of metal(loid)s, the site requires regular monitoring to ensure that the stabilizing conditions are maintained. Soil amendments used to enhance immobilization may need to be periodically reapplied to maintain their effectiveness. We critically examine the applicability of this technology to manage metal(loid)s contaminated soils and identify fertile areas for future research.
Most rocks contain both ferromagnetic and paramagnetic minerals that contribute to their bulk magnetic susceptibility and the anisotropy of magnetic susceptibility. Anisotropy of magnetic susceptibility techniques typically measure the net susceptibility and are not able to separate paramagnetic and ferromagnetic contributions. Since different minerals may form at various times and/or under different conditions, examination of their individual contributions provides unique information related to the rock's formation and evolution. By subjecting a sample to high magnetic fields, the ferromagnetic minerals become saturated and the contribution of the paramagnetic minerals can be evaluated (the slope of the line at high field values, on a field vs magnetization plot). Using this approach, we developed a new technique that separates the ferromagnetic and paramagnetic components of standard 1 inch cylindrical samples using a Vibrating Sample Magnetometer. This separation is tested by artificially combining separate samples with known paramagnetic-only and ferromagnetic-only behaviour. By comparing the high-field results of a combined paramagnetic and ferromagnetic signal to the classic low field alternating current susceptibility of the paramagnetic-only signal, we demonstrate that the high field anisotropy is the result solely of the paramagnetic fabric even when the low field anisotropy of magnetic susceptibility is dominated by the ferromagnetic minerals. A ferromagnetic-only fabric is calculated for the combined paramagnetic and ferromagnetic rock, by tensor subtraction of the high field (paramagnetic-only) and low field (paramagnetic plus ferromagnetic) measurements on the same sample. Application of this technique to natural samples of combined paramagnetic and ferromagnetic behaviour is discussed.
The carbon-13 spin-lattice relaxation rates, T 1 -1, for nickel(II)-histidine complexes in aqueous solution at pH 10·4, caused by the unpaired electrons of the Ni2+ ions, have been studied at a magnetic field strength of 6·34 T over the temperature range from 298 to 361 K. Likewise, the T 1 -1 rates of the corresponding zinc(II) complex were obtained in the range from 308 to 372 K at 2·11 T and 6·34 T. These data have been analysed in conjunction with the corresponding spin-lattice and spin-spin relaxation rates, T 1 -1 and T 2 -1, and contact shift data for the nickel(II)-histidine complexes, which have previously been obtained (1977, J. Am. chem. Soc., 99, 5845) at 2·35 T. The total amount of data thus available, allows an independent determination of all the model parameters involved. The analysis shows that the field and temperature dependences of the relaxation of the carbons in the metal-bound ligands conform closely to the Solomon-Bloembergen-Morgan theories for the nuclear and the electron relaxations, while the parameters obtained are in general accord with the basic assumptions of these theories. Thus, the value of (6·4 ± 0·4) × 10-13 s found for the correlation time, τ v , for the modulation of the zero-field splitting (ZFS) interaction causing the electron relaxations, T 1e and T 2e, amply fulfil the condition, τ v T 1e, T 2e, for a rigorous application of the Bloembergen-Morgan theory. The small value for τ v is related to an increased mobility of the water molecules in the immediate vicinity of the complexes. The values obtained for five of the six Ni2+-carbon distances of the dominant complex, are in close agreement with the corresponding crystal phase distances obtained from X-ray analysis, which indicates strongly that the point-dipole approximation of the Solomon theory holds in these cases. Only the data for the most remote carbon atom in the complex show a significant deviation from this approximation due to electron delocalization. The analysis of these data also indicates a smaller relaxation rate for the delocalized part of the electrons than that found for the metalcentred part.
This paper describes how powerful neodymium magnets and an electronic balance can be used to determine magnetic moments and susceptibilities of transition metal complexes. The technique is an improvement on one previously reported (J. Chem. Educ. 1998, 75, 61) and allows the effect of temperature on paramagnetism to be studied. Results consistent with the Curie law are reported and a theoretical background to the measurement of magnetic moments is given to explain why magnetic field strength and its gradient are important to the technique described. Keywords (Audience): Second-Year Undergraduate
The combination of metal ions with malic acid (hydroxybutane diacid) and 4,4‘-bipyridine ligands under hydro(solvo)thermal conditions has resulted in the formation of three novel coordination polymers, {[M(C4H4O5)(bipy)0.5]·H2O}n (M = CoII (1), NiII (2), 0.3CoII + 0.7NiII (3); C4H4O52- = malate dianion, bipy = 4,4‘-bipyridine). The metal ions were interconnected by α- and β-carboxylates of malate to produce infinite [M(C4H4O5)]n layers, which were further pillared by bridging bipy molecules to form a 3D network. The μ3-malate ligand exhibits a pentadentate coordination mode, with all of the five oxygen atoms participating in the coordination. The magnetic pathways of three compounds are through M−O−C−O−M with nonplanar skew-skew conformations; compound 1 shows antiferromagnetic interactions, while 2 is ferromagnetic, due to different electronic configurations of the metal ions.
Nickel hyperaccumulation can defend plants against herbivores and pathogens. However, variability in plant tissue elemental concentrations in space and time will influence the effectiveness of this defense. We investigated a South African Ni hyperaccumulator, Senecio coronatus Thunb. (Harv.), for variation in nine elements (Ni plus Ca, Cu, Fe, K, Mg, Mn, P and Zn) between populations and between above-ground and below-ground plant organs (leaves, roots). Plant material was collected from four populations growing on ultramafic soils in the vicinity of Badplaas, Mpumalanga Province, South Africa. Concentrations of Ca, Cu, Fe, K, Mg, Mn, Ni, P and Zn were determined in dry-ashed samples. Two-way analysis of variance of data for each element revealed considerable variation in S. coronatus plant chemistry. Leaf concentrations of all elements except Cu were generally greater than root concentrations. Population-level variation was found for Ca, Fe, Mn, P, Ni and Zn, and of these all but P showed significant two-way interactions as well. Significant positive correlations were found between some pairs of elements: in hyperaccumulator roots (Ni–Ca, K–Mg), non-hyperaccumulator roots (Fe–Mn, Fe–Zn, Fe–Cu, Cu–Zn), hyperaccumulator leaves (P–Mg, P–Fe, P–Mn, Fe–Mg) and non-hyperaccumulator leaves (P–Mn, P–Ca, Ca–Mn). Two populations hyperaccumulated Ni in leaves (means of 12,000 and 8800 μg Ni/g) whereas the others did not (means of 120 and 130 μg Ni/g). Such extreme population-level variation in Ni accumulation ability is unusual among Ni hyperaccumulator species: its physiological basis and possible consequences for plant elemental defense deserve further investigation.
Various examples are given for plant memory. In plants magnetite is found in phytoferritin. This compound has the highest
electrical conductivity of any cell material and it is synthezised de novo in cells. We suggest that plant memory is stored
in magnetite in the core of phytoferritin.
KeywordsFerritin-Hormones-Magnetite-Plant memory-Provenances-Signal transmission
The phytoremediation is an environment friendly, green technology that is cost effective and energetically inexpensive. Metal
hyperaccumulator plants are used to remove metal from terrestrial as well as aquatic ecosystems. The technique makes use of
the intrinsic capacity of plants to accumulate metal and transport them to shoots, ability to form phytochelatins in roots
and sequester the metal ions. Harbouring the genes that are considered as signatures for the tolerance and hyperaccumulation
from identified hyperaccumulator plant species into the transgenic plants provide a platform to develop the technology with
the help of genetic engineering. This would result in transgenics that may have large biomass and fast growth a quality essential
for removal of metal from soil quickly and in large quantities. Despite so much of a potential, the progress in the field
of developing transgenic phytoremediator plant species is rather slow. This can be attributed to the lack of our understanding
of complex interactions in the soil and indigenous mechanisms in the plants that allow metal translocation, accumulation and
removal from a site. The review focuses on the work carried out in the field of metal phytoremediation from contaminated soil.
The paper concludes with an assessment of the current status of technology development and its future prospects with emphasis
on a combinatorial approach.
The successful application of various nanoplatforms in medicine under in vitro conditions has generated some interest in agri-nanotechnology. This technology holds the promise of controlled release of agrochemicals and site targeted delivery of various macromolecules needed for improved plant disease resistance, efficient nutrient utilization and enhanced plant growth. Processes such as nanoencapsulation show the benefit of more efficient use and safer handling of pesticides with less exposure to the environment that guarantees ecoprotection. The uptake efficiency and effects of various nanoparticles on the growth and metabolic functions vary differently among plants. Nanoparticle mediated plant transformation has the potential for genetic modification of plants for further improvement. Specifically, application of nanoparticle technology in plant pathology targets specific agricultural problems in plant–pathogen interactions and provide new ways for crop protection. Herein we reviewed the delivery of nanoparticulate materials to plants and their ultimate effects which could provide some insights for the safe use of this novel technology for the improvement of crops.