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The concept of the Borehole Diffusive Flux Apparatus (BDFA) is presented herein. The BDFA is an innovative apparatus designed to provide continuous direct access to an undisturbed column of sediment that can be monitored at multiple discrete vertical intervals to provide high-resolution characterization of local-scale mass transfer and attenuation....
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Citations
... Fractured media may be particularly susceptible to issues arising from back diffusion, and characterization of fractured media sites has been discussed by Parker et al. [20]. More recently, a variety of field tests specific to back diffusion have been proposed [19,[21][22][23][24]. In addition, new approaches to numerical modeling have been developed to better simulate back diffusion [25][26][27][28][29]. ...
Recalcitrant groundwater contamination is a common problem at hazardous waste sites worldwide. Groundwater contamination persists despite decades of remediation efforts at many sites because contaminants sorbed or dissolved within low-conductivity zones can back diffuse into high-conductivity zones, and therefore act as a continuing source of contamination to flowing groundwater. A review of the available literature on remediation of plume persistence due to back diffusion was conducted, and four sites were selected as case studies. Remediation at the sites included pump and treat, enhanced bioremediation, and thermal treatment. Our review highlights that a relatively small number of sites have been studied in sufficient detail to fully evaluate remediation of back diffusion; however, three general conclusions can be made based on the review. First, it is difficult to assess the significance of back diffusion without sufficient data to distinguish between multiple factors contributing to contaminant rebound and plume persistence. Second, high-resolution vertical samples are decidedly valuable for back diffusion assessment but are generally lacking in post-treatment assessments. Third, complete contaminant mass removal from back diffusion sources may not always be possible. Partial contaminant mass removal may nonetheless have potential benefits, similar to partial mass removal from primary DNAPL source zones.
... As a result, the WHO has set a maximum limit of 50 mg/L in drinking water for it to be considered potable. In the last decade, studies on health risk assessment related to nitrate exposure in groundwater have gained momentum, and are widely applied and adopted by different countries, such as India [24][25][26], Mexico [27], Pakistan [28], China [29][30][31] and Iran [32,33]. ...
In recent years, the sharp increase in nitrate concentration in groundwater has become an important health issue worldwide, and uncontrolled groundwater use can cause potentially dangerous problems for human health. The aim of the present study is to determine the degree of groundwater pollution in the Bokoya massif, located in the Moroccan Rif, and to quantify the non-cancer risks associated with its consumption. Two rounds of sampling were carried out during April and September 2018, respectively collecting 96 and 73 samples distributed between wells and springs covering the entire study area. The pollution index results showed that 39% and 41% of the studied springs possess a pollution degree ranging from moderate to very high during the wet and dry periods, respectively. Deterioration of the water quality is mainly linked to strong mineralisation from mineral dissolution of Palaeozoic and Predorsal rocks, and to the high concentrations of anthropogenic nitrates found in the limestone formation. The assessment of non-carcinogenic risk by oral exposure to nitrates showed that about 47%, 45% and 43% of the samples constitute non-carcinogenic risk to the health of children, adult women, and adult men, respectively. Children have a slightly higher exposure to non-carcinogenic risks. In a situation typified by both the scarcity of drinking water and a lack of population-wide information for the study area, the results of this study will help guide decision-makers and water resource management services towards a policy of limiting the sources of nitrates found in aquifers in order to limit the potentially harmful effects on human health.
