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Diversity and Negative Effect of PM0.3-10.0 Adsorbed by Needles
of Urban Trees in Irkutsk, Russia
Tatiana Alekseevna Mikhailova
Siberian Institute of Plant Physiology and Biochemistry: Sibirskij institut ziologii i biohimii rastenij SO RAN
Olga Vladimirovna Shergina ( sherolga80@mail.ru )
Sibirskij institut ziologii i biohimii rastenij SO RAN https://orcid.org/0000-0002-6333-8821
Research Article
Keywords: Urban trees, Pollution by PM, SEM, EDAX, EDS, Negative effect on tree metabolism
Posted Date: July 21st, 2023
DOI: https://doi.org/10.21203/rs.3.rs-3065315/v1
License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License
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Abstract
The study was performed in natural forests preserved within the Boreal zone city, Irkutsk, Russia. Test sites were selected in the
forests in different districts of the city, where samples of Scots pine (
Pinus sylvestris L.
) and Siberian larch (
Larix sibirica Ledeb.
)
needles were taken to study the adsorption on their surface of aerosol particles of different sizes, in microns: PM0.3, PM0.5, PM1,
PM2.5, PM5, PM10. Scanning electron microscopy was used to obtain high–resolution photographs (magnication 800–2000x,
16000x) and aerosol particles (Particulate Matter – PM) were shown to be intensively adsorbed by the surface of needles, with
both size and shape of the particles characterized by a wide variety. Pine needles can be covered with particles of solid aerosol by
50–75%, stomata are often completely blocked. Larch needles often show areas, which are completely covered with aerosol
particles, there are often found stomata deformed by the penetration of PMx. X–ray spectral microanalysis showed differences in
the chemical composition of adsorbed PMx, the particles can be metallic if metals predominate in their composition,
carbonaceous – in case of carbon predominance, or polyelemental, if the composition is complex and includes signicant
quantities of other elements besides metals and carbon (calcium, magnesium, potassium, sodium, sulfur, chlorine, uorine). Since
the particles contain a large proportion of technogenic pollutants, accumulation by the needles of some widespread pollutants
was investigated. A direct correlation of a highly signicant level between the concentration of PMx in the air and the
accumulation of many heavy metals in pine and larch needles, as well as sulfur, uorine, chlorine, has been revealed, which
indicates a high cleaning capacity of urban forests. At the same time, the negative impact of PMx particles on the vital status of
trees is great, which shows in intense disturbance of the parameters of photosynthesis and transpiration, leading to a signicant
decrease in the growth characteristics of trees and reduction in the photosynthetic volume of the crowns. We consider that the
results obtained are instrumental in developing an approach to improvement of urban forests status and creating a comfortable
urban environment for the population.
Introduction
Aerosol particles (Particulate Matter, PMx) of different sizes, different morphological characteristics and diverse chemical
composition are currently believed to be among the most common and dangerous pollutants of atmospheric air. PMx can contain
almost all known technogenic pollutants, including uorides, chlorine-containing, sulfur-containing, nitrates, ammonia, heavy
metals, polyaromatic hydrocarbons (PAHs), as well as pathogenic microorganisms, viruses, allergens (Baldacchini et al. 2019; Xin
et al. 2021; Wang et al. 2021; Tianfang et al. 2022; Leonard et al. 2023). Therefore, the results of the PMx measurement in the air
provide quite comprehensive information about the level and nature of its pollution. Such data are especially important for
assessing the state of the environment of urbanized territories with high population density. Numerous publications of researchers
from many countries great point to the interest in aerosol particles, their origin, composition, morphology, and impact on human
health (Mukherjee and Agrawal 2017; Jain et al. 2021; Jirau-Colón et al. 2021; Mei et al. 2021; Xin et al. 2021). The negative
impact of PMx on human health has been proven by many studies. For example, suspended particles have been shown to cause
exacerbation of respiratory diseases (Jirau-Colón et al. 2021), to spur asthmatic symptoms (Lu et al. 2021), ne particles can
penetrate deep into the lungs (Wang et al. 2021) and even increase the incidence of lung cancer (Chu et al. 2021), prolonged
exposure to PM can increase the risk of hypertension (Xu et al. 2021). The greatest danger to human health is believed to be
represented by particles with a size of ≤ 2.5 µm, which are constantly suspended in the air and are assessed by some researchers
as a very high environmental risk factor, ranking fth in the general list of mortality risk factors (Cohen et al. 2017).
Researchers unanimously agree that one of the most effective methods of reducing urban air pollution is creation of different
types of green spaces that serve as powerful phytolters against PM (Ram et al. 2015; Chen et al. 2020; Letter and Jäger 2020;
Wróblewska and Jeong, 2021; Popek et al. 2022). In our opinion, the key ecosystem function of air purication belongs to natural
forests as sustainable ecosystems preserved within cities. However, many megacities obviously lack this component of the urban
ecosystem, so various types of articial landscaping are being created there and active research is underway to identify the types
of arboreal plants that most effectively absorb PMx (Beckett et al. 2000; Yang et al. 2015; Jin et al. 2021; Mei et al. 2021; Chen et
al. 2022; Triratnesh et al. 2022). Such species include
Fraxinus excelsior, Ulmus laevis, Quercus ilex, Pinus nigra, Pinus pinea
(Vigevani et al. 2022). In articial landings near highways in Norway,
Pinus mugo, Pinus sylvestris, Taxus media, Taxus baccata,
Stephanandra incisa, Betula pendula
demonstrated the highest eciency in PMx capturing (Sæbø et al. 2012). When studying
urban trees in Korea,
Quercus salicina and Pinus densiora
stood out by the largest number of PMx adsorbed by the leaf surface
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(Jin et al. 2021). When ranking the most common tree species in cities of the world according to the eciency of removing PM2.5
from the air, it was found that
Platanus acerifolia, Acer saccharinum, Gleditsia triacanthos
exceeded the average eciency
estimate; however, a high potential of evergreen coniferous trees in urban air purication from suspended particles was observed
(Yang et al. 2015; Lindén et al. 2023). It is also shown that the eciency of capturing ne particles rises with an increase in the
volume of urban plantings due to additional planting of shrubs (Kim et al. 2017).
We have also previously showed the ability of different types of trees, shrubs, herbaceous plants to accumulate pollutants of
various chemical composition in assimilation organs – heavy metals, PAHs, acidogenic gases, uorides (Kalugina et al. 2018,
2019; Mikhailova et al. 2018; Takahashi et al. 2020). The data obtained are important both for monitoring of environmental
pollution and for selecting the species recommended for urban greening. For example, we believe that when creating articial
plantings, it is impossible to do without evergreen coniferous trees, at the same time, we recommend introducing deciduous
species into such plantings:
Cotoneaster melanocarpus, Populus suaveolens, Duschekia fruticosa, Sambucus racemose, Populus
tremula, Spirea media
, these species can accumulate toxic pollutants in leaves in very high concentrations exceeding the
background by 15–22 times.
In this paper, we sum up the results of research of aerosol particles effects on trees growing in urban forests of natural origin. We
present real photos of particles of different sizes adsorbed by pine needles (
Pinus sylvestris
) and larch needles (
Larix sibirica
),
since there is little information on the status of assimilation organs of trees exposed to aerosol particles pollution. However, this
data would be useful to clearly show why photosynthesis process is disrupted and other physiological and biochemical
parameters of the tree change. With this in view, we undertook a special study of the adsorption of aerosol particles by needles of
two common coniferous species in the urban forests of Irkutsk in order to nd out specic features of the particles, their
morphology and chemical composition. Accordingly, the purpose of our work was to investigate the distribution of adsorbed
aerosol particles on the surface of the needles of urban trees, to identify their chemical composition, to show the variety of their
shapes and sizes, to identify their negative impact on tree metabolism.
Material and methods
Study area
The city of Irkutsk is located in Eastern Siberia (boreal zone) and occupies an area of 280 sq. km, about 20% of which are urban
forests of natural origin, preserved in forest parks and on the outskirts of the city (Atlas of development of Irkutsk 2011). The
coniferous species dominating in the forests are Scots pine (
Pinus sylvestris
L.) and Siberian larch (
Larix sibirica
Ledeb.). To
conduct the study, we created 14 test sites in urban forests according to the ICP Forests methodology (Manual on methods and
criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on forests 2010), the 15th
background (reference) test site (TS) was located at a distance of 120 km from the city in a forest area with no technogenic
pollution (Fig.1). The size of each TS amounted to 0.1 ha (1000 m2). Concentrations of aerosol particles of the size range PM0.3,
PM0.5, PM1.0, PM2.5, PM5.0, PM10.0 were measured in the air at all test sites using the atmospheric air quality monitor Air detector 2
AM7P, "Environmental Protection Agency", US. PM Detector Biostar air monitor, “BIOTEQ Technologies”, China, was used to
measure the AQI index. Based on the data obtained, 8 representative test sites were selected (see Fig.1), showing stable results on
PMx concentration measured over a decade, from July 1 to July 10, 2022. Further studies were carried out at these test sites.
Analysis of adsorbed particles
Samples of pine and larch needles from 6–10 trees of each species were collected at representative 8 test sites and immediately
delivered to the laboratory in an isothermal container Mobicool MP30. Samples were prepared from fresh needles by the
quartering method (in 10-fold repetition) for the analysis of its surface contamination by aerosol particles by scanning electron
microscopy (SEM). Certied equipment of the Limnological Institute of SB RAS (Irkutsk) was used to perform the work: FEI
Company Quanta 200 scanning electron microscope with an X–ray microanalysis unit with nitrogen-free cooling GENESIS XM 2
60 – Imaging SEM with APOLLO 10 and an EDAX unit. Qualitative and quantitative microanalysis of PMx particles was performed
using energy dispersive X-ray spectroscopy (EDS) and mapping of the distribution of chemical elements on the needles surface.
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Spectrograms of chemical composition of the adsorbed particles and high-resolution photographs (magnication from 800 to
2000 times) of surface contamination of pine and larch needles were obtained. To determine the size of the PMx, their chemical
composition and concentration, 16000 times increase of the particles was used.
Analytical procedures
Based on the fact that PMx contain a large amount of technogenic pollutants, we investigated the degree of accumulation by the
needles of heavy metals (Pb, Cd, Fe, Zn, Cu, Mn, Al, Cr, Ni, Co, Mo, Ti), sulfur, uorine, chlorine, calcium, magnesium, potassium,
sodium using certied methods and equipment of the Center for Bioanalytics of the Siberian Branch of the Russian Academy of
Sciences and the Republican Analytical Center of Eastern Siberia. The following equipment was used: atomic absorption
spectrophotometer AAnalyst 600 ("PerkinElmer Life and Analytical Sciences", US), optical emission spectrometer ICP-OES Spectro
Arcos with spectrum excitation in inductively coupled plasma ("Spectro Analytical Instruments", Germany). All the analyses were
carried out in 5-fold repetition, the content of elements was calculated in mg/kg of dry weight of needles.
To identify the negative impact of PMx on trees vital status, a number of physiological, biochemical and morphostructural
parameters of pine and larch were determined. As the most representative indicators of trees vital status, the following parameters
were selected: level of tree crowns defoliation, shoots length, needles weight, content of pigments (chlorophylls and carotenoids)
in the needles, the chlorophyll level in the light-collecting complex (LCC), the intensity and productivity of photosynthesis, the
photosynthetic volume of the tree crown, the transpiration rate. Photosynthesis and transpiration parameters were measured in
Binder KBW 240 growth chambers for measuring CO2-O2 and H2O gas exchange on cut shoots in experimental vacuum
polycarbonate chambers with integrated infrared CO2 gas analyzer (PTH, Protmex), O2 gas analyzer (Smart sensor Pro AS8901),
air quality monitor (Air Master 2 AM7), temperature and humidity sensors (Elitech RC-5 Data Logger GSP-6, Engbird IBS-TH1). The
measurement data were transmitted to the computer monitor. The content of chlorophylls and carotenoids was determined by
spectrophotometric method, the optical densities of extracts were measured at wavelengths of 662, 644 and 440.5 nm. The
proportion of chlorophylls localized in the light-collecting complex (LCC) was calculated using the Lichtenthaler formula
(Lichtenthaler 1987): (Chl
b
+ 1.2 Chl
b
)/ (Chl
a
+ Chl
b
). The photosynthetic volume of the tree crown was measured using the
Huepar HLR1000 laser rangender and the Photosynthesis light quantum meter TES 1339P, the calculation was performed using
the formula of the volume of a truncated cone with a correction factor for defoliation (Taxation of a single tree 2020).
Statistical analysis
Statistical processing of all the data obtained was performed with the program "Statistical Computing Environment R" and its use
in Data Mining (Shipunov et al. 2014). The average values of each parameter and their standard deviations were calculated. To
establish correlations between the indicators, the nonparametric Spearman coecient was used. The equality of the mean values
in paired samples was checked using the t-test. The signicance of the differences was assessed using the Mann–Whitney
criterion (at P ≤ 0.05). All the values of the indicators given in this paper yielded statistically signicant differences.
Results and discussion
Representative test sites selected in urban forests showed signicant differences in the concentration of PMx of different sizes in
the air and AQI, as well as large differences from the background test site (Fig.2). Judging by the data obtained, most urban test
sites (TS) are heavily polluted with aerosol particles, at the same time, the AQI on them is at least 3–4 times and at most 12–13
times higher than the background. The exceptions are TS 3 and TS 8, which are less polluted, possibly due to their remoteness
from sources of technogenic emissions and from highways. It should be noted that in urban test sites, the largest share among
polluting suspended particles is taken by small particles (PM0.3, PM0.5, PM1.0, PM2.5), while the concentrations of PM5.0 and PM10
particles are not high, and in the background test site there are no such particles at all. Other authors also report higher
concentrations of small particles in polluted urban air (Linh et al. 2023; Vlasov et al. 2023).
The study of pine and larch needles demonstrated that suspended particles are intensively adsorbed on its surface. Heavily
polluted pine needles, for example, on TS 1 and TS 5, can be covered with aerosol particles by 50–75%, moreover, complete
blockage of stomata is often observed (Fig.3a, b). Active adsorption of PMx particles on the surface of pine needles is fostered by
their morphological features: a signicant thickness of the wax layer, the presence of trichomes, a large number of stomata and
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resin passages. Besides, these features cause a strong connection of polluting particles, especially small particles, with needles,
which makes it almost impossible for the particles to wash out by precipitation or to get released by wind currents.
In microphotographs, the surface of larch needles (epidermis and cuticle) looks lumpy, formations in the form of folds and ridge-
like protrusions are visible, which contributes to the active adsorption of suspended particles. The areas between the folds may be
seen to be almost completely covered with aerosol particles (Fig.4a). Penetration of particles into the stomata often leads to
deformation of the latter (Fig.4b). Since the covering tissues of larch needles are more thin-walled, they are more vulnerable to
suspended particles, especially those containing heavy metals.
X-ray spectral microanalysis of adsorbed PMx was carried out and the percentage of chemical elements in them was calculated
(Fig.5). PMx particles were found to contain carbon, silicon, sulfur, calcium, phosphorus, chlorine, magnesium in the largest
amount, a signicant proportion of heavy metals (Cd, Pb, Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, V, W, Zn), present in the form of metallized
clusters of different-sized particles capable of actively penetrating into tissues through the stomata and cuticle.
The photographs show that the size and shape of the particles are characterized by a wide variety (Fig.6). The particles with
carbon as a dominating component are in most cases of irregular round shape, their surface is not smooth and has through holes.
Particles containing metals, as a rule, have a spherical shape and are able to attract each other by their magnetic elds, forming
large clusters of PM particles. Polyelement particles may contain up to 10–15 different elements, including C, Si, S, Cl, As, heavy
metals.
In addition to the study of the adsorption of suspended particles on the surface of needles, the accumulation of the most common
pollutants in pine and larch needles – heavy metals (Pb, Cd, Fe, Zn, Cu, Mn, Al, Cr, Ni, Co, Mo, Ti), sulfur, uorine, chlorine – was
also determined at all TS, these elements often being the components of PMx coming from technogenic emissions of most
enterprises, as well as from vehicle emissions. The results showed high HM contents in pine and larch needles, in all cases
exceeding background values (Table1). For example, in pine needles, the lead content is higher than the background by 5–16
times, cadmium – by 3–9 times, chromium by 9–16 times, nickel – up to 10 times, copper accumulates to a lesser extent (the
maximum excess of the background is 6.1 times), zinc, iron, aluminum, strontium (max excess background 5.2 times),
molybdenum, manganese, cobalt, titanium (max background excess 3.3–4.1 times). The results of the larch needles analysis also
indicate a signicant accumulation of HM, especially strontium, lead, iron, aluminum, chromium, titanium. High content of lead
(exceeding the background by 40 times), chromium (31 times), cadmium (14 times) is characteristic of TS 4 located in the forest
near the airport. The lowest content of HM, both in pine and larch conifers, was found on TS 3 and TS 8.
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Table 1
The content of heavy metals* (mg/kg) in the needles of Scots pine and Siberian larch on the surveyed test site in the urban forests
of Irkutsk
Test site
number Pb Cd Zn Cu Fe Mn Al Cr Ni Co Mo Sr Ti
Scots pine
1 0.66 0.044 51.22 3.94 295.75 2.34 520.46 0.86 4.14 0.27 0.21 22.75 21.54
2 0.72 0.039 49.12 3.64 283.73 3.45 587.08 0.88 5.70 0.32 0.18 19.70 26.92
3 0.45 0.015 40.07 2.76 203.01 1.36 345.35 0.61 0.78 0.14 0.10 10.63 15.98
4 0.97 0.042 49.57 3.99 351.74 3.77 533.80 1.11 4.05 0.29 0.23 26.05 28.23
5 0.79 0.029 55.77 3.83 313.65 2.73 443.36 0.94 3.91 0.20 0.16 17.59 22.48
6 0.62 0.027 47.87 3.73 276.76 1.99 390.64 0.78 1.30 0.16 0.14 15.89 20.16
7 0.46 0.018 42.17 3.68 242.34 1.87 389.09 0.74 1.09 0.15 0.13 13.94 18.39
8 0.32 0.017 41.45 3.28 209.67 1.32 358.26 0.63 1.01 0.12 0.11 9.17 14.75
Background 0.06 0.005 10.97 0.65 68.81 1.02 115.42 0.07 0.54 0.08 0.07 5.04 6.81
Siberian larch
1 1.15 0.072 31.33 7.58 825.78 6.36 1245.78 1.95 4.96 0.71 0.26 177.27 42.05
2 1.08 0.068 28.71 7.26 772.36 7.65 1179.45 1.86 5.79 0.76 0.22 169.53 45.47
3 0.24 0.021 19.17 3.26 470.12 1.95 722.54 1.27 1.22 0.27 0.14 86.72 19.48
4 1.98 0.084 36.45 8.29 989.45 7.80 1709.12 2.48 7.06 0.85 0.31 186.12 76.37
5 0.97 0.062 30.64 5.59 649.25 5.98 1025.23 1.74 4.64 0.62 0.24 158.10 49.94
6 0.81 0.042 29.74 5.05 639.05 4.35 901.15 1.69 2.18 0.59 0.18 147.62 44.69
7 0.67 0.036 21.35 4.98 630.51 4.22 886.12 1.47 1.68 0.51 0.17 126.92 35.17
8 0.32 0.024 20.18 3.38 497.35 1.86 732.61 1.31 1.28 0.24 0.13 88.627 20.41
Background 0.05 0.006 7.15 0.78 89.78 1.38 189.45 0.08 0.63 0.09 0.09 75.04 11.51
* Average values are given; the error of the average value is from 5 to 10%.
Besides heavy metals, concentrations of sulfur, uorine and chlorine were determined in needles of the conifer trees in urban TS;
although these elements are important in plant metabolism (perhaps uorine is an exception), but with their high content they act
as toxic pollutants contained in PM particles. The following parameters were determined: the total content of sulfur (Fig.7а) and
its ionic form SO4 − 2 (Fig.7d), the total concentration of chlorine (Fig.7b) and its ionic form Cl−(Fig.7e), the total content of
uorine (Fig.7c) and its ionic form F− (Fig.7f). The data obtained show that in pine and larch needles, the trend of total sulfur
accumulation is similar, its level is 2.5–3.5 times higher than the background, while the level of ionic form in larch needles is 9
times higher than the background, in pine needles – 6 times. According to the accumulation of chlorine in the needles, similarity is
observed both in the level of total chlorine (exceeds the background by 2.1–2.5 times), and in the concentration of the ionic form
(above the background by 12.4–12.7 times). The uorine content also exceeds the background, in pine needles – by 2.0–3.5
times, in larch needles – by 3.0–6.5 times. The data obtained indicate that the source of these pollutants (HM, sulfur, uorine,
chlorine) in pine and larch needles is PMx, polluting the atmospheric air. To support this conclusion, correlations were calculated
between the accumulation of pollutants (on the example of thirteen heavy metals) in the needles and the concentration of
different–sized PMx in the air at each TS (Table2). Correlation analysis conrmed the presence of direct dependencies of a high
level of signicance (r = 0.52–0.85; P = 0.05, n = 24) between the concentration of aerosol particles and the accumulation of
pollutants (HM) in pine and larch needles from urban forests, while in the background TS the correlations between PMx and HM
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were not statistically signicant. These data also indicate the pronounced ability of pine and larch trees to purify polluted urban
atmospheric air from suspended particles. Therefore, urban forests have a high ecosystem signicance, as they function as
natural phytolters.
However, chronic exposure to aerosol particles negatively affects the status of urban trees themselves, as our studies have shown.
The tree crown defoliation level in urban forests in most TS was found to exceed the background, reaching a maximum of 65% for
pine and larch (background 10–15%). The length of shoots is smaller, in comparison with background parameters, in pine by 1.5–
3.1 times, in larch by 15–44%. Pine shoots have signicantly reduced the weight of needles (from 1.3 to 2.3 times) and the
number of pairs of needles (from 1.8 to 2.8 times). The weight of needles on larch shoots is in most cases halved. Changes in the
photosynthetic volume of pine and larch tree crowns in urban forests are similar, the sharpest decrease in this indicator being
observed at TS 2, 4, 5, for pine – by 2.1–2.6 times, for larch – by 2.3–2.6 times. Changes in the parameters considered are less
pronounced on TS 3 and TS 8, which are located on the outskirts of the city away from major highways and industrial enterprises.
Table 2
Correlation coecients between the concentration of PMx particles in
atmospheric air in test sites and the content of thirteen HM in pine and larch
needles at the test sites in urban forests of Irkutsk
Test site number ∑ PMх, µg/m3Correlation coecients between ∑PMх
and ∑13 HM
for pine needles for larch needles
1 3265 ± 126.3 85.1 ± 4.2 87.3 ± 4.2
2 2245 ± 87.6 65.2 ± 3.8 71.2 ± 4.3
3 1023 ± 55.3 53.2 ± 3.6 59.4 ± 3.8
4 2975 ± 112.6 78.2 ± 5.2 80.3 ± 6.1
5 2501 ± 107.8 68.4 ± 4.4 74.5 ± 4.2
6 2185 ± 103.5 72.2 ± 3.6 79.2 ± 3.5
7 1734 ± 69.3 64.4 ± 2.7 68.4 ± 2.6
8 1286 ± 63.5 54.3 ± 3.8 62.3 ± 3.5
It was logical to assume that the identied negative morphostructural changes in trees result from signicant disturbances of their
metabolism, primarily photosynthesis, respiration, transpiration. A signicant disturbance of pine photosynthesis in urban forests
is indicated by a drop in its intensity, ranging from 9–46% of background values, productivity – from 6–38% (Fig.8, 9). Larch
studies also detect negative changes in photosynthesis, its productivity is especially sharply reduced on most TS (by 1.6–2.0
times), with the exception of TS 3 and 8, where pathological changes are much less pronounced (Fig.8, 9). Functional disorders of
photosynthesis are largely determined by the changes found in the pigment complex of needles. These changes led to a
disturbance in the amount and ratio of different pigment groups. For the studied species of coniferous trees in urban forests, the
general trend was a decrease in chlorophyll
a
and carotenoids content, and at the same time an increase in of chlorophyll
b
level
in comparison with background indicators (Table3). In pine needles, the decrease in the content of chlorophyll
a
was maximum
30%, the level of carotenoids decreased more dramatically, by a maximum of 47%. As for chlorophyll
b
, its content in pine needles
increased signicantly, from 26 to 48% on all TS except TS 3 and 8, where its level increased slightly, only by 8%. Larch needles
demonstrated the same tendency in reducing chlorophyll
a
content – its level fell to the greatest extent on TS 1, 2, 4, 5 (by 19–
25%), and slightly on TS 3 and 8. Accordingly, pronounced changes in the ratio of chl
a
and chl
b
were observed. The percentage
of carotenoid levels drop in general was slightly less than in pine needles – by a maximum of 39%. At the same time, there was a
much greater increase in the content of chlorophyll
b
than in pine needles, by a maximum of 63% (TS 1), and a minimum of 10%
(TS 3).
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Table 3
The content of photosynthetic pigments (mg/g dry mass) in the needles of pine and larch trees growing in the
urban forests of Irkutsk
Test site number Chlorophyll Carotenoids % chlorophylls (
a + b
) in LCC
a b
Chl
a
/ Chl
b
Scots pine
1 0.63 ± 0.02 0.34 ± 0.03 1.85 ± 0,11 0.23 ± 0.01 77.1 ± 3.12
2 0.65 ± 0.02 0.31 ± 0.04 2.10 ± 0,12 0.22 ± 0.02 71.0 ± 5.61
3 0.77 ± 0.02 0.25 ± 0.01 3.08 ± 0,13 0.33 ± 0.01 53.9 ± 2.33
4 0.61 ± 0.03 0.32 ± 0.03 1.91 ± 0,16 0.21 ± 0.01 75.7 ± 4.62
5 0.61 ± 0.03 0.33 ± 0.02 1.84 ± 0,07 0.20 ± 0.03 77.2 ± 4.65
6 0.68 ± 0.02 0.33 ± 0.03 2.06 ± 0,14 0.25 ± 0.01 71.9 ± 4.02
7 0.71 ± 0.02 0.29 ± 0.01 2.45 ± 0,15 0.29 ± 0.01 63.8 ± 2.44
8 0.78 ± 0.03 0.25 ± 0.02 3.12 ± 0,12 0.32 ± 0.01 53.4 ± 1.62
Background 0.86 ± 0.02 0.23 ± 0.01 3.74 ± 0,18 0.38 ± 0.01 46.4 ± 1.67
Siberian larch
1 0.72 ± 0.02 0.31 ± 0.02 2.32 ± 0,11 0.27 ± 0.01 66.2 ± 2.9
2 0.76 ± 0.03 0.29 ± 0.02 2.62 ± 0,12 0.30 ± 0.02 60.8 ± 0.7
3 0.87 ± 0.04 0.21 ± 0.01 4.14 ± 0,13 0.34 ± 0.02 42.8 ± 1.2
4 0.7 ± 0.02 0.31 ± 0.02 2.26 ± 0,16 0.26 ± 0.01 67.5 ± 1.4
5 0.75 ± 0.02 0.28 ± 0.02 2.68 ± 0,07 0.23 ± 0.01 59.8 ± 0.7
6 0.82 ± 0.03 0.26 ± 0.01 3.15 ± 0,14 0.28 ± 0.02 53.0 ± 1.8
7 0.84 ± 0.03 0.25 ± 0.02 3.36 ± 0,15 0.29 ± 0.01 50.5 ± 1.3
8 0.91 ± 0.03 0.23 ± 0.02 3.96 ± 0,12 0.35 ± 0.02 44.4 ± 2.8
Background 0.93 ± 0.02 0.19 ± 0.01 4.89 ± 0,18 0.38 ± 0.01 37.3 ± 1.3
The analysis of the data obtained allows us to conclude that the most vulnerable component of pine and larch pigment complex
is chlorophyll
a
. A signicant decrease in its level can be caused either by the breakdown of its molecules or by synthesis
deceleration under the inuence of pollution (Tuzhilkina 2009). The reason for the decrease in carotenoids concentration may be
their enhanced use for maintaining the photochemical function of chlorophyll
a
, particularly in case of absorbtion of toxicants
from polluted air that initiate the formation of reactive oxygen species (ROS), since carotenoids extinguish the excited triplet states
of chlorophyll and ROS (Mulenga et al. 2020). This is exactly the situation we observe in this case – the entry of toxic substances
(pollutants) into the assimilation organs of arboreal plants. We have previously found that technogenic pollutants contribute to
ROS formation in plant cells (Kalugina et al. 2021). As for chlorophyll
b
, the trend of its change is determined, apparently, by its
greater stability, as well as by the performance of a compensatory role in reducing the concentration of chlorophyll
a
under various
kinds of negative inuences (Khanna-Chopra 2012). The important role of chlorophyll
b
is also indicated by its presence almost
exclusively in light-collecting antenna complexes (LCCs). Our calculations demonstrate that a clear increase in the percentage of
chlorophylls amount in pine (by an average of 22%) and larch (by an average of 19%) is mainly due to chlorophyll
b
, which allows
us to infer that its protective role does grow with pollution of assimilation organs (see Table3).
Disturbance of metabolism of pine and larch trees is also indicated by such a parameter as a change in the transpiration rate,
which, rst of all, characterizes the state of their water metabolism (Feklistov and Biryukov 2007). Since transpiration as an
energy-dependent process is associated with photosynthesis, it could be expected to decrease in trees in an urban environment,
Page 9/20
which was proven by our study. A notable decrease in transpiration was found in both species, and the similarity is observed not
only in the trend, but also in the degree of weakening of this process in almost all TS (by a maximum of 2.1 times), with the
exception of TS 3 and 8, where this indicator changed slightly or remained at the background level (Fig.10) A signicant decrease
in transpiration was also anticipated as the needles stomata on most TS are literally "clogged" with polluting suspended particles
(PM).
Conclusion
The study of Irkutsk urban forests has shown that Scots pine and Siberian larch trees are polluted by aerosol particles of
technogenic origin. In the atmospheric air of the city, the concentration of particles (PMx) of different sizes is high, especially that
of nely dispersed particles (PM ≤ 2.5 microns), and the AQI index can be 12–13 times higher than the background. PMx are
intensively adsorbed by pine and larch needles, they can cover the surface of the needles almost completely. The chemical
composition of PMx is very diverse, they can be roughly classed as carbonaceous (with a predominance of carbon in the
composition), metallic (with a predominance of metals), polyelement (with different elements in approximately the same
concentrations: carbon, HM, silicon, calcium, sulfur, chlorine, sodium, magnesium, potassium, uorine). Direct correlations of a
high level of signicance between the concentration of aerosol particles in the air and the content of pollutants (HM) in pine and
larch needles on test sites in urban forests were identied. These data indicate a well pronounced ability of pine and larch trees to
purify polluted urban atmospheric air from suspended particles. Therefore, urban forests have a high ecosystem signicance due
to their function of natural phytolters. However, chronic exposure to aerosol particles negatively affects the state of urban trees
themselves, as evidenced by the following: decrease in the photosynthetic volume of tree crowns, functional disorders of
photosynthesis, decrease in transpiration. Taking into account the results obtained, it is extremely important to nd an approach
to optimizing the status of urban trees. And in order to improve the city ecological environment, we recommend to expand the area
of urban forests by creating articial plantations that would be similar in structure to natural forest ecosystems.
Declarations
Acknowledgment
We thank M.M. Maslennikova, leading engineer at the Department of Ultrastructure of the Limnological Institute, Siberian Branch,
Russian Academy of Sciences, Irkutsk for her help in the studies using scanning electron microscopy.
Ethical Approval
No ethical issues were violated in this study.
Consent to Participate
All authors agree to participate.
Consent to Publish
All authors agree for publication.
Authors Contributions
Tatiana Alekseevna Mikhailova: developed the idea of the paper, wrote the manuscript, Olga Vladimirovna Shergina: conceived the
study, performed the experiments, data collection, statistically analyzed the data, and drafted the manuscript. The authors read
and are in agreement of the nal manuscript.
Funding
This work was supported by the Russian Science Foundation, project No. 22-24-00140.
Competing Interests
Page 10/20
The authors declare no competing interests.
Availability of data and materials-missing
Not applicable' for that specic section.
References
1. Atlas of development of Irkutsk (2011) Editor L.M. Korytny. Publishing House of the Institute of Geography SO RAN, Irkutsk.
http:// http://irkipedia.ru/content/atlas_razvitiya_irkutska_2011_g_soderzhanie (In Russian)
2. Baldacchini C, Sgrigna G, Clarke W, Tallis M, Calfapietra C (2019) An ultra-spatially resolved method to quali-quantitative
monitor particulate matter in urban environment. Environ Sci Pollut Res 26:18719–18729. https://doi.org/10.1007/s11356-
019-05160-8
3. Beckett KP, Freer-Smith PH, Taylor G (2000) The capture of particulate pollution by trees at ve contrasting urban sites.
Arboric J 24(2–3):209–230. https://doi.org/10.1080/03071375.2000.9747273
4. Chen H, Kaiyang Q, Richard P (2020). Reduction of trac-related particulate matter by roadside plants: effect of trac
pressure and sampling height. Int J Phytoremediation 22(2):184–200. https://doi.org/10.1080/15226514.2019.1652565
5. Chen H, Xia D-S, Wang B, Liu H, Ma X (2022) Pollution monitoring using the leaf-deposited particulates and magnetism of the
leaves of 23 plant species in a semi-arid city, Northwest China. Environ Sci Pollut Res 29:34898–34911.
https://doi.org/10.1007/s11356-021-16686-1
. Chu J, Dong Y, Han X, Xie J, Xu X, Xie G (2021) Short-term prediction of urban PM2.5 based on a hybrid modied variational
mode decomposition and support vector regression model. Environ Sci Pollut Res 28:56–72. https://doi.org/10.1007/s11356-
020-11065-8
7. Cohen AJ, Brauer M, Burnett R, Anderson HR, Frostad J, Estep K, Balakrishnan K, Brunekreef B, Dandona L, Dandona R, Feigin
V, Freedman G, Hubbell B, Jobling A, Kan H, Knibbs L, Liu Y, Martin R, Morawska L, Pope CA, Shin H, Straif K, Shaddick G,
Thomas M, van Dingenen R, van Donkelaar A, Vos T, Murray CJL, Forouzanfar MH (2017) Estimates and 25-year trends of the
global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study
2015. Lancet 389(10082):1907–1918. https://doi.org/10.1016/S0140-6736(17)30505-6
. Feklistov P, Biryukov S (2007) Needle transpiration of shore pine and common pine in the conditions of the Arkhangelsk
region. Arct Environ Res 2:86-90 (In Russian)
9. Jain S, Sharma SK, Vijayan N, Mandal TK (2021) Investigating the seasonal variability in source contribution to PM2.5 and
PM10 using different receptor models during 2013–2016 in Delhi, India. Environ Sci Pollut Res 28:4660–4675.
https://doi.org/10.1007/s11356-020-10645-y
10. Jin EJ, Yoon JH, Bae EJ, Jeong BR, Yong SH, Choi MS (2021) Particulate Matter Removal Ability of Ten Evergreen Trees
Planted in Korea Urban Greening. Forests 12(4):438. https://doi.org/10.3390/f12040438
11. Jirau-Colón H, Toro-Heredia J, Layuno J, Calderon ED, Gioda A, Jiménez-Vélez BD (2021) Distribution of toxic metals and
relative toxicity of airborne PM2.5 in Puerto Rico. Environ Sci Pollut Res 28:16504–16516. https://doi.org/10.1007/s11356-
020-11673-4
12. Kalugina OV, Mikhailova TA, Afanasyeva LV, Shergina OV (2021) Activity and isozyme composition of peroxidase in Scots
pine (Pinus sylvestris L.) needles effected by technogenic emissions from various enterprises and vehicles. Sib J Life Sci
Agric 13(1):11-34. https://doi.org/10.12731/2658-6649-2021-13-1-11-34
13. Kalugina OV, Mikhailova TA, Shergina OV (2018) Contamination of Scots pine forests with polycyclic aromatic hydrocarbons
on the territory of industrial city of Siberia, Russia. Environ Sci Pollut Res 25:21176–21184. https://doi.org/10.1007/s11356-
018-2230-9
14. Kalugina OV, Mikhailova TA, Shergina OV (2019) Use herbal plants (Chamaenerion angustifolium and Tanacetum vulgare) for
monitoring of territories polluted by uorine-containing emissions. Chem Plant Raw Mater 1:309-316.
https://doi.org/10.14258/jcprm.2019014097 (In Russian)
Page 11/20
15. Khanna-Chopra R (2012) Leaf senescence and abiotic stresses share reactive oxygen species-mediated chloroplast
degradation. Protoplasma 249:469–481. https://doi.org/10.1007/s00709-011-0308-z
1. Kim S, Lee S, Hwang K, An K (2017) Exploring Sustainable Street Tree Planting Patterns to Be Resistant against Fine Particles
(PM2.5). Sustainability 9(10):1709. https://doi.org/10.3390/su9101709
17. Leonard J, Borthakur A, Koutnik VS, Brar J, Glasman J, Cowger W, Dittrich TM, Mohanty SK (2023) Challenges of using leaves
as a biomonitoring system to assess airborne microplastic deposition on urban tree canopies. Atmospheric Pollut Res
14(2):101651. https://doi.org/10.1016/j.apr.2023.101651
1. Letter C, Jäger G (2020) Simulating the potential of trees to reduce particulate matter pollution in urban areas throughout the
year. Environ Dev Sustain 22:4311–4321. https://doi.org/10.1007/s10668-019-00385-6
19. Lichtenthaler HK (1987) Chlorophylls and carotenoids: pigments of photosynthetic biomembranes. Meth Enzymol 148:350–
382. https://doi.org/10.1016/0076-6879(87)48036-1
20. Lindén J, Gustafsson M, Uddling J, Watne A, Pleijel H (2023) Air pollution removal through deposition on urban vegetation:
the importance of vegetation characteristics. Urban For Urban Green 81:127843. https://doi.org/10.1016/j.ufug.2023.127843
21. Linh BD, Le HA, Truong NX (2023) Physico‐chemical properties and transboundary transport of PM2.5 in Bien Hoa City, Dong
Nai Province, Southeastern Vietnam. Environ Sci Pollut Res 30:36533–36544. https://doi.org/10.1007/s11356-022-24801-z
22. Lu X, Li R, Yan X (2021) Airway hyperresponsiveness development and the toxicity of PM2.5. Environ Sci Pollut Res 28:6374–
6391. https://doi.org/10.1007/s11356-020-12051-w
23. Manual on methods and criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution
on forests (2010) UNECE, ICP Forests Programme Coordinating Centre, Hamburg. http://www.icp-forests.org/Manual.htm/
24. Mei P, Malik V, Harper R, Jiménez J (2021). Air pollution, human health and the benets of trees: a biomolecular and
physiologic perspective. Arboric J 43:1–22. https://doi.org/10.1080/03071375.2020.1854995
25. Mikhailova TA, Shergina OV, Kalugina OV (2018) Selection of trees and shrubs for planting territories polluted by technogenic
uorides. Advances in Current Natural Sciences 11(2):284–288. https://doi.org/10.17513/use.36940 (In Russian)
2. Mukherjee A, Agrawal M (2017) World air particulate matter: sources, distribution and health effects. Environ Chem Lett
15:283–309. https://doi.org/10.1007/s10311-017-0611-9
27. Mulenga C, Clarke C, Meincken M (2020) Physiological and growth responses to pollutant-induced biochemical changes in
plants: a review. Pollution 6(4):827–848. https://doi.org/10.22059/poll.2020.303151.821
2. Popek R, Mahawar L, Shekhawat GS, Przybysz A (2022) Phyto‐cleaning of particulate matter from polluted air by woody plant
species in the near‐desert city of Jodhpur (India) and the role of heme oxygenase in their response to PM stress conditions.
Environ Sci Pollut Res 29:70228–70241. https://doi.org/10.1007/s11356-022-20769-y
29. Ram SS, Majumde, S, Chaudhuri P, Chanda S, Santra SC, Chakrabort, A, Sudarshan M (2015) A Review on Air Pollution
Monitoring and Management Using Plants With Special Reference to Foliar Dust Adsorption and Physiological Stress
Responses. Crit Rev Environ Sci Technol 45:2489–2522. https://doi.org/10.1080/10643389.2015.1046775
30. Shipunov AB, Baldin EM, Volkova PA, Korobeinikov AI, Nazarova SA, Petrov SV, Suyanov VG (2014) Visual statistics. Let's
use R! DMK-Press, Moscow. https://elib.grsu.by/doc/14364 (In Russian)
31. Sæbø A, Popek R, Nawrot B, Hanslin HM, Gawronska H, Gawronski SW (2012) Plant species differences in particulate matter
accumulation on leaf surfaces. Sci Total Environ 427–428:347–54. https://doi.org/10.1016/j.scitotenv.2012.03.084
32. Takahashi M, Feng Z, Mikhailova TA, Kalugina OV, Shergina OV, Afanasieva LV, Heng RKJ, Majid NMA, Sase H (2020) Air
pollution monitoring and tree and forest decline in East Asia: a review. Sci Total Environ 742:140288.
https://doi.org/10.1016/j.scitotenv.2020.140288
33. Taxation of a single tree (2020) Ural State Forest Engineering University, Yekaterinburg.
https://elar.usfeu.ru/handle/123456789/10532 (In Russian)
34. Tianfang Yu, Junjian W, Yiwen C, Hui Z (2022) Extinction effect of foliar dust retention on urban vegetation as estimated by
atmospheric PM10 concentration in Shenzhen, China. Remote Sens 14(20):5103. https://doi.org/10.3390/rs14205103
35. Triratnesh G, Sudhir P, Tanzil M, Ki-Hyun K, Mohammed K (2022). Micro-morphological analysis of foliar uptake and retention
of airborne particulate matter (PM)-bound toxic metals: implications for their phytoremediation. Chem Ecol 38:1–19.
Page 12/20
https://doi.org/10.1080/02757540.2022.2108021
3. Tuzhilkina VV (2009) Response of the pigment system of conifers to long-term industrial air pollution. Russ J Ecol 40(4):227–
232. https://doi.org/10.1134/S1067413609060149
37. Vigevani I, Corsini D, Mori J, Pasquinelli A, Gibin M, Comin S, Szwałko P, Cagnolati E, Ferrini F, Fini A (2022) Particulate
Pollution Capture by Seventeen Woody Species Growing in Parks or along Roads in Two European Cities. Sustainability
14:1113. https://doi.org/10.3390/su14031113
3. Vlasov DV, Vasil’chuk JYu, Kosheleva NE, Kasimov NS (2023) Contamination levels and source apportionment of potentially
toxic elements in size‐fractionated road dust of Moscow. Environ Sci Pollut Res 30: 38099–38120.
https://doi.org/10.1007/s11356-022-24934-1
39. Wang G, Xu Y, Huang L, Kun Wang K, Shen H, Li Z (2021) Pollution characteristics and toxic effects of PM1.0 and PM2.5 in
Harbin, China. Environ Sci Pollut Res 28:13229–13242. https://doi.org/10.1007/s11356-020-11510-8
40. Wróblewska K, Jeong BR (2021) Effectiveness of plants and green infrastructure utilization in ambient particulate matter
removal. Environ Sci Eur 33:110. https://doi.org/10.1186/s12302-021-00547-2
41. Xin L, Wang J, Sun J, Zhang C, Tong X, Wan J, Feng J, Tian H, Zhang Z (2021) Cellular effects of PM2.5 from Suzhou, China:
relationship to chemical composition and endotoxin content. Environ Sci Pollut Res 28:287–299.
https://doi.org/10.1007/s11356-020-10403-0
42. Xu J, Zhang Y, Yao M, Wu, Duan Z, Zhao X, Zhang J (2021) Long-term effects of ambient PM2.5 on hypertension in multi-
ethnic population from Sichuan province, China: a study based on 2013 and 2018 health service surveys. Environ Sci Pollut
Res 28:5991–6004. https://doi.org/10.1007/s11356-020-10893-y
43. Yang J, Chang Y, Yan P (2015) Ranking the suitability of common urban tree species for controlling PM2.5 pollution.
Atmospheric Pollut Res 6:267‐277. https://doi.org/10.5094/APR.2015.031
Figures
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Figure 1
Map of the study area and location of test sites: Irkutsk city on the Russian territory (a); representative test sites in the Irkutsk
urban forests (b), coordinates: No. 1 – 52°22'16''N 104°06'37''E; 2 – 52°19'46N 104°20'22''E; 3 – 52°18'17''N 104°21'19''E; 4 –
52°16'53''N 104°21'56''E; 5 – 52°17'04N 104°13'58''E; 6 – 52°15'35''N 104°13'39''E; 7 – 52°14'36''N 104°15'42''E; 8 – 52°13'07N
104°19'33''E; location of the background test site (c).
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Figure 2
AQI index and concentrations of PMx particles in the atmospheric air (the average values for a summer period) at the test sites in
urban forests of Irkutsk.
Figure 3
Stomata of pine (a) and larch (b) needles plugged up by aerosol particles.
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Figure 4
PMx particles on the folded surface of larch needles (a), a stomata deformated (b).
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Figure 5
X-ray spectral microanalysis by SEM and EDAX of individual PM particles (a), as an example – larch needle surface (b).
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Figure 6
PMx particles of different shapes and chemical composition on the surface of Scots pine and Siberian larch needles of urban
trees: a, b, c, d, e – metalized; f, g, h – carbonaceous; i, j, k, l, m, n, o – polyelemental.
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Figure 7
The total content of sulfur (a), chlorine (b), uorine (c) and the content of ionic forms of sulfur (d), chlorine (e), uorine (f) in the
needles of Scots pine and Siberian larch.
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Figure 8
Photosynthesis intensity of Scots pine and Siberian larch in surveyed test sites in urban forests of Irkutsk.
Figure 9
Photosynthetic productivity of Scots pine and Siberian larch in surveyed test sites in urban forests of Irkutsk.
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Figure 10
Transpiration rate of Scots pine and Siberian larch in surveyed test sites in urban forests of Irkutsk.
