Tag: Water

Sulfurization of Dissolved Organic Matter Increases Hg-Sulfide-Dissolved Organic Matter Bioavailability to a Hg-Methylating Bacterium

Student Database

Author: Graham, AM; Cameron-Burr, KT; Hajic, HA; Lee, C; Msekela, D; Gilmour, CC Description: Reactions of dissolved organic matter (DOM) with aqueous sulfide (termed sulfurization) in anoxic environments can substantially increase DOM’s reduced sulfur functional group content. Sulfurization may affect DOM-trace metal interactions, including complexation and metal-containing particle precipitation, aggregation, and dissolution. Using a diverse suite of DOM samples, we found that susceptibility to additional sulfur incorporation via reaction with aqueous sulfide increased with increasing DOM aromatic-, carbonyl-, and carboxyl-C content. The role of DOM sulfurization in enhancing Hg bioavailability…

See more and a link to full text

Effect of divalent metals on Hg(II) uptake and methylation by bacteria

Student Database

Author: Schaefer, JK; Szczuka, A; Morel, FM Description: The production of methylmercury by some bacteria is a key first step in the accumulation and biomagnification of this toxic substance in aquatic food webs, a major human health concern. By direct measurement of cellular Hg(II) uptake in model iron and sulfate reducing bacteria, we have observed that specific trace metals, such as Zn(II) and Cd(II), inhibit uptake and methylation in these organisms, whereas other metals, such as Ni(II), Co(II), or Fe(II), do not. The inhibition of Hg(II) methylation by Zn(II) was…

See more and a link to full text

Anaerobic Mercury Methylation and Demethylation by Geobacter bemidjiensis Bem

Student Database

Author: Lu, X; Liu, Y; Johs, A; Zhao, L; Wang, T; Yang, Z; Lin, H; Elias, DA; Pierce, EM; Liang, L; Barkay, T; Gu, B Description: Microbial methylation and demethylation are two competing processes controlling the net production and bioaccumulation of neurotoxic methylmercury (MeHg) in natural ecosystems. Although mercury (Hg) methylation by anaerobic microorganisms and demethylation by aerobic Hg-resistant bacteria have both been extensively studied, little attention has been given to MeHg degradation by anaerobic bacteria, particularly the iron-reducing bacterium Geobacter bemidjiensis Bem. Here we report, for the first time,…

See more and a link to full text

Influences of watershed characteristics on mercury levels in Wisconsin rivers

Student Database

Author: Hurley, JP; Benoit, JM; Babiarz, CL; Shafer, MM; Andren, AW; Sullivan, JR; Hammond, R; Webb, DA Description: Total and monomethyl mercury were measured at 39 river sites in Wisconsin during fall 1992 and spring 1993. Using a Geographic Information System (GIS), we delineated watersheds with unique and homogeneous physical characteristics. Mean unfiltered total Hg (HgT) was higher in spring (7.94 ng L-1) than in fall (3.45 ng L-1). Major differences in HgT yields were observed among various land-use groupings. In wetland/forest watersheds, elevated HgT fluxes were associated with the…

See more and a link to full text

Mercury and methyl mercury in fishes from Bacaja River (Brazilian Amazon): evidence for bioaccumulation and biomagnification

Student Database

Author: Souza-Araujo, J; Giarrizzo, T; Lima, MO; Souza, MB Description: This study assessed total mercury (THg) and methyl mercury (MeHg) concentrations, bioaccumulation and biomagnification of THg through the food web in fishes consumed by indigenous communities of Bacaja River, the largest tributary of the right bank of Xingu River. In total, 496 fish (22 species) were sampled. Nine species had THg concentrations above the limit recommended by the World Health Organisation (0.5 microg g(-1) wet mass), and one exceeded the recommended level for Hg in predatory fishes by Brazilian law…

See more and a link to full text

Emerging investigator series: methylmercury speciation and dimethylmercury production in sulfidic solutions

Student Database

Author: Kanzler, CR; Lian, P; Trainer, EL; Yang, X; Govind, N; Parks, JM; Graham, AM Description: Alkylated mercury species (monomethylmercury, MeHg, and dimethylmercury, DMeHg) exhibit significant bioaccumulation, and pose significant risks to ecosystems and human health. Although decades of research have been devoted to understanding MeHg formation and degradation, little is known about the DMeHg formation in aquatic systems. Here, we combine complementary experimental and computational approaches to examine MeHg speciation and DMeHg formation in sulfidic aqueous solutions, with an emphasis on the formation and decomposition of the binuclear bis(methylmercuric(ii))…

See more and a link to full text

Mercury methylation and methylmercury demethylation in boreal lake sediment with legacy sulphate pollution

Student Database

Author: Huang, H; Mangal, V; Rennie, MD; Tong, H; Simpson, MJ; Mitchell, CPJ Description: Sulphate and dissolved organic matter (DOM) in freshwater systems may regulate the formation of methylmercury (MeHg), a potent neurotoxin that biomagnifies in aquatic ecosystems. While many boreal lakes continue to recover from decades of elevated atmospheric sulphate deposition, little research has examined whether historically high sulphate concentrations can result in persistently elevated MeHg production and accumulation in aquatic systems. This study used sediment from a historically sulphate-impacted lake and an adjacent reference lake in northwestern Ontario,…

See more and a link to full text

Nitrate and Brain/CNS Cancer Diagnoses in the First Year of Life

Featured Database

Author: Sajid, Arshi; Semprini, Jason Description: Nitrates in drinking water, common in agricultural states like Iowa, pose health risks to young infants. This brief first reviews the plausible biological mechanisms linking nitrate exposure to brain and central nervous system (BCNS) cancers in the first year of life. We then linked historic water quality and cancer registry data at the county level to construct linear and quantile regression models estimating the association between a BCNS diagnosis and nitrate measures. We found significantly higher nitrate levels preceding pediatric zero-year-old BCNS cancer diagnoses….

See more and a link to full text

Trends in nitrate contamination: implications for communities reliant on groundwater for drinking

Featured Database

Author: Jayasekera, D. Harshanee; Munde, Siddhi; Snow, Daniel D.; Rimšaitė, Renata Description: Nebraska’s vulnerability to nitrate contamination in water systems is highlighted by agrochemical inputs with leaching potential and the state’s reliance on groundwater for drinking. Nitrate is a regulated compound in drinking water due to its association with methemoglobinemia and other chronic health conditions. This study examines water quality in Nebraska’s groundwater over several decades, focusing on temporal and spatial variations in nitrate concentrations across different well types. The findings reveal increasing statewide trends in nitrate levels, with considerable…

See more and a link to full text

The association between increases in nitrate in drinking water and colorectal cancer incidence rates in California, USA

Featured Database

Author: Cisneros, Ricardo; Amiri, Marzieh; Gharibi, Hamed Description: PURPOSE: The water resources in California are polluted with nitrate (NO3) due to the ever-increasing application of nitrogen-based fertilizers. Considering the potential connection between NO3 in drinking water and the incidence rate of colorectal cancer, this study aims to investigate the association between long-term exposure to NO3 via drinking water and the incidence of colorectal cancer from 2010 to 2015 in California. METHODS: A total of 56,631 diagnoses of colorectal cancer were recorded from 2010 to 2015. A generalized linear model was…

See more and a link to full text
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.