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851 results on '"Fendorf, Scott"'

57. Mechanism of Arsenic Partitioning During Sulfidation of As-Sorbed Ferrihydrite Nanoparticles

Author

Kumar, Naresh, Noël, Vincent, Besold, Johannes, Planer-friedrich, Britta, Boye, Kristin, Fendorf, Scott, Brown, Gordon E., Kumar, Naresh, Noël, Vincent, Besold, Johannes, Planer-friedrich, Britta, Boye, Kristin, Fendorf, Scott, and Brown, Gordon E.

Abstract

Knowledge of how arsenic (As) partitions among various phases in Fe-rich sulfidic environments is critical for understanding the fate and mobility of As in such environments. We studied the reaction of arsenite and arsenate sorbed on ferrihydrite nanoparticle surfaces with dissolved sulfide at varying S/Fe ratios (0.1–2.0) to understand the fate and transformation mechanism of As during sulfidation of ferrihydrite. By using aqueous As speciation analysis by IC-ICP-MS and solid-phase As speciation analysis by synchrotron-based X-ray absorption spectroscopy (XAS), we were able to discern the mechanism and pathways of As partitioning and thio-arsenic species formation. Our results provide a mechanistic understanding of the fate and transformation of arsenic during the codiagenesis of As, Fe, and S in reducing environments. Our aqueous-phase As speciation data, combined with solid-phase speciation data, indicate that sulfidation of As-sorbed ferrihydrite nanoparticles results in their transformation to trithioarsenate and arsenite, independent of the initial arsenic species used. The nature and extent of transformation and the thioarsenate species formed were controlled by S/Fe ratios in our experiments. However, arsenate was reduced to arsenite before transformation to trithioarsenate.

Published
2022

77. Perchlorate and Agriculture on Mars

Author

Oze, Christopher, primary, Beisel, Joshua, additional, Dabsys, Edward, additional, Dall, Jacqueline, additional, North, Gretchen, additional, Scott, Allan, additional, Lopez, Alandra Marie, additional, Holmes, Randall, additional, and Fendorf, Scott, additional

Published
2021
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85. Prevalence of elevated blood lead levels among pregnant women and sources of lead exposure in rural Bangladesh: A case control study

Author

Forsyth, Jenna E., Saiful Islam, M., Parvez, Sarker Masud, Raqib, Rubhana, Sajjadur Rahman, M., Marie Muehe, E., Fendorf, Scott, and Luby, Stephen P.

Subjects
Rural Population, Bangladesh, Case control study, Turmeric, Food Contamination, Environmental Exposure, Prenatal lead exposure, Article, Lead Poisoning, Lead, Pregnancy, Case-Control Studies, Prevalence, Humans, Female, Agrochemicals, Lead-soldered cans
Abstract

Prenatal and early childhood lead exposures impair cognitive development. We aimed to evaluate the prevalence of elevated blood lead levels (BLLs) among pregnant women in rural Bangladesh and to identify sources of lead exposure. We analyzed the BLLs of 430 pregnant women randomly selected from rural communities in central Bangladesh. Fifty-seven cases were selected with the highest BLLs, ≥ 7 μg/dL, and 59 controls were selected with the lowest BLLs, 5 μg/dL. Most women with elevated BLLs were spatially clustered. Cases were 2.6 times more likely than controls to consume food from a can (95% CI 1.0–6.3, p = 0.04); 3.6 times more likely to use Basudin, a specific brand of pesticide (95% CI 1.6–7.9, p = 0.002); 3.6 times more likely to use Rifit, a specific brand of herbicide (95% CI 1.7–7.9, p = 0.001); 2.9 times more likely to report using any herbicides (95% CI 1.2–7.3, p = 0.02); and 3.3 times more likely to grind rice (95% CI 1.3–8.4, p = 0.01). Five out of 28 food storage cans were lead-soldered. However, there was minimal physical evidence of lead contamination from 382 agrochemical samples and 129 ground and unground rice samples. Among 17 turmeric samples, one contained excessive lead (265 μg/g) and chromium (49 μg/g). Overall, we found evidence of elevated BLLs and multiple possible sources of lead exposure in rural Bangladesh. Further research should explicate and develop interventions to interrupt these pathways., Highlights • Prenatal blood lead levels and lead sources are assessed in rural Bangladesh. • Elevated blood lead levels are found among pregnant women. • Multiple possible sources of lead are identified; all related to food. • Future lead prevention studies should investigate food storage and production.

Published
2018

88. Insights into the role of lateral hyporheic exchange on biogeochemical cycling as a function of varying annual discharge in the East River, CO, USA

Author

Fox, Patricia, primary, Arora, Bhavna, additional, Anderson, Carolyn, additional, Beutler, Curtis, additional, Carroll, Rosemary, additional, Christensen, John, additional, Dewey, Christian, additional, Dong, Wenming, additional, Dwivedi, Dipankar, additional, Faybishenko, Boris, additional, Fendorf, Scott, additional, Keiluweit, Marco, additional, Malenda, Helen, additional, Newcomer, Michelle, additional, Newman, Alexander, additional, Williams, Kenneth, additional, and Nico, Peter, additional

Published
2021
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95. Processes conducive to the release and transport of arsenic into aquifers of Bangladesh

Author

Polizzotto, Matthew L., Harvey, Charles F., Sutton, Steve R., and Fendorf, Scott

Subjects
Aquifers -- Environmental aspects, Heavy metals -- Health aspects, Heavy metals -- Environmental aspects, Science and technology
Abstract

Arsenic is a contaminant in the groundwater of Holocene aquifers in Bangladesh, where [approximately equal to] 57 million people drink water with arsenic levels exceeding the limits set by the World Health Organization. Although arsenic is native to the sediments, the means by which it is released to groundwater remains unresolved. Contrary to the current paradigm, ferric (hydr)oxides appear to dominate the partitioning of arsenic in the near surface but have a limited impact at aquifer depths where wells extract groundwater with high arsenic concentrations. We present a sequence of evidence that, taken together, suggest that arsenic may be released in the near surface and then transported to depth. We establish that (i) the only portion of the sediment profile with conditions destabilizing to arsenic in our analysis is in the surface or near-surface environment; (ii) a consistent input of arsenic via sediment deposition exists; (ii) retardation of arsenic transport is limited in the aquifers; and (iv) groundwater recharge occurs at a rate sufficient to necessitate continued input of arsenic to maintain observed concentrations. Our analyses thus lead to the premise that arsenic is liberated in surface and near-surface sediments through cyclic redox conditions and is subsequently transported to well depth. Influx of sediment and redox cycling provide a long-term source of arsenic that when liberated in the near surface is only weakly partitioned onto sediments deeper in the profile and is transported through aquifers by groundwater recharge. redox | Ferric (hydr)oxides

Published
2005

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