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1.
Environ Sci Process Impacts ; 24(8): 1195-1211, 2022 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-35829655

RESUMO

Filtered and particulate mercury (Hg) and methylmercury (MMHg), and associated water chemistry parameters, were evaluated bi-hourly for several 30 h periods during the summer and winter seasons at several distinct locations (downstream forested, midstream urban/suburban, upstream industrial) along a creek contaminated with high levels of inorganic Hg to determine if biogeochemical Hg and MMHg cycles respond to the daily photocycle. In summer particulate Hg and MMHg concentrations doubled overnight (excluding the upstream industrial site) concurrent with increases in turbidity and total suspended sediment; no such pattern was evident in winter. Seasonal and diel changes in the activity of macrobiota affecting the suspension of contaminated sediments are likely responsible for these patterns as other potential explanatory variables (e.g., instrument drift, pH, discharge) could not account for the range and timing of our observations. Diel patterns in filtered Hg (HgD) were significant only at locations and times of the year when channel shading was not present and daytime concentrations increased 22-89% above nighttime minima likely caused by direct and indirect photochemical reactions. Relationships between HgD and dissolved organic carbon (DOC) concentration or character were inconsistent between sites. Unlike HgD, there were significant diel patterns in filtered MMHg (MMHgD) at all sites and times of year, with summer concentrations peaking in mid to late afternoon while the timing differed in winter, with concentrations peaking after sunset. Daily variability in MMHgD concentration ranged between 25 and 75%. The results imply key controls on net methylation occur within the stream or on the stream bed and include factors such as small-scale temperature changes in the water column and photosynthetic activity of stream biofilm. With respect to stream monitoring, results from this study indicate (1) consistent timing in stream Hg and MMHg sampling is required for accurate assessment of long-term trends, (2) in situ measurements of turbidity can be used to quantify diel dynamics of both particulate Hg and MMHg concentrations, and (3) in situ fluorescing dissolved organic matter (FDOM), a potential proxy for DOC, was not capable of resolving diel dynamics of filtered Hg or MMHg.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Poluentes Químicos da Água , Monitoramento Ambiental/métodos , Mercúrio/análise , Água , Poluentes Químicos da Água/análise
2.
Sci Total Environ ; 721: 137647, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32197286

RESUMO

This review documents recent advances in terrestrial mercury cycling. Terrestrial mercury (Hg) research has matured in some areas, and is developing rapidly in others. We summarize the state of the science circa 2010 as a starting point, and then present the advances during the last decade in three areas: land use, sulfate deposition, and climate change. The advances are presented in the framework of three Hg "gateways" to the terrestrial environment: inputs from the atmosphere, uptake in food, and runoff with surface water. Among the most notable advances: These and other advances reported here are of value in evaluating the effectiveness of the Minamata Convention on reducing environmental Hg exposure to humans and wildlife.

3.
Environ Sci Process Impacts ; 20(4): 686-707, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29520399

RESUMO

Natural abundance stable Hg isotope measurements were used to place new constraints on sources, transport, and transformations of Hg along the flow path of East Fork Poplar Creek (EFPC), a point-source contaminated headwater stream in Oak Ridge, Tennessee. Particulate-bound Hg in the water column of EFPC within the Y-12 National Security Complex, was isotopically similar to average metallic Hg(0) used in industry, having a mean δ202Hg value of -0.42 ± 0.09‰ (1SD) and near-zero Δ199Hg. On average, particulate fraction δ202Hg values increased downstream by 0.53‰, while Δ199Hg decreased by -0.10‰, converging with the Hg isotopic composition of the fine fraction of streambed sediment along the 26 km flow path. The dissolved fraction behaved differently. Although initial Δ199Hg values of the dissolved fraction were also near-zero, these values increased transiently along the flow path. Initial δ202Hg values of the dissolved fraction were more variable than in the particulate fraction, ranging from -0.44 to 0.18‰ among three seasonal sampling campaigns, but converged to an average δ202Hg value of 0.01 ± 0.10‰ (1SD) downstream. Dissolved Hg in the hyporheic and riparian pore water had higher and lower δ202Hg values, respectively, compared to dissolved Hg in stream water. Variations in Hg isotopic composition of the dissolved and suspended fractions along the flow path suggest that: (1) physical processes such as dilution and sedimentation do not fully explain decreases in total mercury concentrations along the flow path; (2) in-stream processes include photochemical reduction, but microbial reduction is likely more dominant; and (3) additional sources of dissolved mercury inputs to EFPC at baseflow during this study predominantly arise from the hyporheic zone.


Assuntos
Monitoramento Ambiental/métodos , Isótopos de Mercúrio/análise , Mercúrio/análise , Rios/química , Poluentes Químicos da Água/análise , Indústrias , Tennessee
4.
Environ Sci Process Impacts ; 19(12): 1505-1517, 2017 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-29147694

RESUMO

Wildfires alter forested ecosystems, which include large stores of mercury (Hg) and organic carbon, two compounds that are closely linked in vegetation, soils, and streamwater. Studies have shown that wildfires release elevated levels of mercury to the atmosphere which can be locally redeposited and leave charred organic material (vegetation and litter) on the soil surface. Both can contribute to the elevated mobilization of Hg into lakes and streams. However, no studies have conducted a detailed examination of hydrological transport of Hg following a wildfire. This study investigates the coupled transport of mercury and carbon at Twomile Run, a headwater stream located in the forested mountains of Shenandoah National Park, in the year following a low-severity wildfire. Weekly baseflow samples and bi-hourly high-flow storm samples were analyzed for dissolved and particulate mercury (HgD and HgP, respectively), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254, surrogate for DOC quantity and character), and total suspended solids (TSS), and were compared with identical measurements taken from a nearby unburned watershed. For all flow conditions sampled at the burned site (which did not include the 2 months following the fire), streamwater HgD and DOC concentrations, and corresponding UV254, were similar to the unburned system. TSS concentrations varied between sites but overall differences were relatively small in magnitude and likely attributable to site differences rather than fire effects. Notably, the HgP per unit of TSS at the burned site was an order of magnitude higher than the unburned site (2.66 and 0.13 ng HgP per mg TSS, respectively) for 8 months following the fire, resulting in elevated HgP concentrations for the range of flow conditions, after which there was a rapid return to non-disturbed conditions. Streamwater total Hg fluxes roughly doubled (0.55 to 1.04 µg m-2 yr-1) as a consequence of the fire, indicating that in addition to changing atmospheric and terrestrial Hg cycling, fires can rapidly and significantly alter the streamwater Hg which has implication for downstream ecosystems. These findings are particularly relevant as the occurrence and severity of wildfires are expected to increase in the mid-latitudes in response to climate change.


Assuntos
Monitoramento Ambiental/métodos , Florestas , Mercúrio/análise , Compostos Orgânicos/análise , Rios/química , Poluentes Químicos da Água/análise , Incêndios Florestais , Mudança Climática , Ecossistema , Poluentes do Solo/análise , Sudeste dos Estados Unidos , Movimentos da Água
5.
Environ Toxicol Chem ; 35(6): 1386-400, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26574732

RESUMO

Sediments and floodplain soils in the East Fork Poplar Creek watershed (Oak Ridge, TN, USA) are contaminated with high levels of mercury (Hg) from an industrial source at the headwaters. Although baseflow conditions have been monitored, concentrations of Hg and methylmercury (MeHg) during high-flow storm events, when the stream is more hydrologically connected to the floodplain, have yet to be assessed. The present study evaluated baseflow and event-driven Hg and MeHg dynamics in East Fork Poplar Creek, 5 km upstream of the confluence with Poplar Creek, to determine the importance of hydrology to in-stream concentrations and downstream loads and to ascertain whether the dynamics are comparable to those of systems without an industrial Hg source. Particulate Hg and MeHg were positively correlated with discharge (r(2) = 0.64 and 0.58, respectively) and total suspended sediment (r(2) = 0.97 and 0.89, respectively), and dissolved Hg also increased with increasing flow (r(2) = 0.18) and was associated with increases in dissolved organic carbon (r(2) = 0.65), similar to the dynamics observed in uncontaminated systems. Dissolved MeHg decreased with increases in discharge (r(2) = 0.23) and was not related to dissolved organic carbon concentrations (p = 0.56), dynamics comparable to relatively uncontaminated watersheds with a small percentage of wetlands (<10%). Although stormflows exert a dominant control on particulate Hg, particulate MeHg, and dissolved Hg concentrations and loads, baseflows were associated with the highest dissolved MeHg concentration (0.38 ng/L) and represented the majority of the annual dissolved MeHg load. Environ Toxicol Chem 2016;35:1386-1400. Published 2015 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work, and as such, is in the public domain in the United States of America.


Assuntos
Monitoramento Ambiental/métodos , Mercúrio/análise , Compostos de Metilmercúrio/análise , Rios/química , Estações do Ano , Poluentes Químicos da Água/análise , Indústrias , Mercúrio/química , Compostos de Metilmercúrio/química , Solubilidade , Propriedades de Superfície , Tennessee , Poluentes Químicos da Água/química
6.
Environ Toxicol Chem ; 31(5): 1143-8, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22416015

RESUMO

Mercury (Hg) depuration into growing feathers is a well-studied phenomenon in waterbirds. Although the kinetics of Hg excretion in relation to molt and diet has been studied extensively, the relationship between the individual nutritional condition of nestlings and dietary Hg accumulation has not been investigated. In the present study, a body-condition index (BCI) and nutritional condition index (NCI) for nestlings of two waterbird species occupying different trophic positions on the aquatic food web were determined and used to predict Hg accumulation through diet. Candidate models consisting of these indices and nestling age were compared using Akaike's information criterion corrected for small sample sizes. For both species, the top-performing model contained the sole parameter of nutritional condition index (NCI). The relationship between Hg and NCI was stronger in the species foraging higher on the trophic web, which experienced higher rates of Hg depuration into feathers. Models containing BCI could not be discounted (AICc < 2) for one of the species and the utility of this index is discussed.


Assuntos
Biomarcadores/análise , Aves , Dieta/veterinária , Plumas/química , Mercúrio/farmacocinética , Animais , Cadeia Alimentar , Mercúrio/análise , New York , Virginia
7.
Environ Toxicol Chem ; 30(9): 2081-3, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21647948

RESUMO

Feathers are commonly used biomarkers of mercury (Hg) contamination in waterbird species. Most studies that analyze waterbird feathers for Hg content report concentrations on a per-unit mass basis. While this is appropriate for intraspecific comparisons, we suggest a more effective method for studies comparing multiple species of similar size and with similar foraging habits. Ptilochronology is a technique for determining the rate of feather growth in individuals based on their nutritional condition. When paired with Hg analysis, feather growth rates can be used to calculate the average daily Hg deposition into a feather. In this study we used this technique in comparison with the commonly used metric of Hg per-unit feather mass in two waterbird species. Average daily Hg deposition into feathers was 26.7% more sensitive to differences in Hg between the two species, suggesting that this may be a more biologically meaningful metric to use in interspecific comparisons.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/metabolismo , Plumas/química , Mercúrio/metabolismo , Animais , Atmosfera/química , Plumas/metabolismo , Compostos de Mercúrio/metabolismo , Comportamento de Nidação , New York , Virginia , Tempo (Meteorologia)
8.
J Environ Monit ; 12(10): 1833-9, 2010 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-20848013

RESUMO

Understanding the processes by which mercury is mobilized from soil to stream is currently limited by a lack of observations during high-flow events, when the majority of this transport occurs. An automated technique to collect stream water for unfiltered total mercury (HgT) analysis was systematically evaluated in a series of laboratory experiments. Potential sources of error investigated were 1) carry-over effects associated with sequential sampling, 2) deposition of HgT into empty bottles prior to sampling, and 3) deposition to or evasion from samples prior to retrieval. Contamination from carry-over effects was minimal (<2%) and HgT deposition to open bottles was negligible. Potentially greater errors are associated with evasive losses of HgT from uncapped samples, with higher temperatures leading to greater evasion. These evasive losses were found to take place primarily within the first eight hours. HgT associated with particulate material is much less prone to evasion than HgT in dissolved form. A field test conducted during a high-flow event confirmed unfiltered HgT concentrations sampled with an automated system were comparable to those taken manually, as the mean absolute difference between automated and manual samples (10%) was similar to the mean difference between duplicate grab samples (9%). Results from this study have demonstrated that a standard automated sampler, retrofitted with appropriately cleaned fluoropolymer tubing and glass bottles, can effectively be used for collection of streamwater during high-flow events for low-level mercury analysis.


Assuntos
Monitoramento Ambiental/métodos , Mercúrio/análise , Rios/química , Poluentes Químicos da Água/análise , Automação , Fracionamento Químico , Mercúrio/química , Poluentes Químicos da Água/química
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