Characterizing Spatial and Temporal Dynamics: Development of a Grid-Based Watershed Mercury Loading Model

Dai, Ting; Ambrose, Robert B.; Alvi, Khalid; Wool, Tim A.; Manguerra, Henry; Chokshi, Mira; Yang, Haihong; Kraemer, Stephen R.

doi:10.1061/40763(178)56

Cited by 9 publications

(11 citation statements)

References 2 publications

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“…Details of GBMM's equations and sensitivity analysis are previously published [ Golden and Knightes , 2011]. GBMM has been applied and validated in multiple settings in the southeastern United States, including the Piedmont Physiographic Province [ Golden and Knightes , 2011; Golden et al , 2010] and Coastal Plain Province [ Dai et al , 2005; Feaster et al , 2010]. Final input parameters for McTier Creek watershed are found elsewhere for the hydrology module [ Feaster et al , 2010].…”

Section: Methodsmentioning

confidence: 99%

Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

et al. 2012

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[1] Mercury (Hg) is one of the leading water quality concerns in surface waters of the United States. Although watershed-scale Hg cycling research has increased in the past two decades, advances in modeling watershed Hg processes in diverse physiographic regions, spatial scales, and land cover types are needed. The goal of this study was to assess Hg cycling in a Coastal Plain system using concentrations and fluxes estimated by multiple watershed-scale models with distinct mathematical frameworks reflecting different system dynamics. We simulated total mercury (Hg T , the sum of filtered and particulate forms) concentrations and fluxes from a Coastal Plain watershed (McTier Creek) using three watershed Hg models and an empirical load model. Model output was compared with observed in-stream Hg T . We found that shallow subsurface flow is a potentially important transport mechanism of particulate Hg T during periods when connectivity between the uplands and surface waters is maximized. Other processes (e.g., stream bank erosion, sediment re-suspension) may increase particulate Hg T in the water column. Simulations and data suggest that variable source area (VSA) flow and lack of rainfall interactions with surface soil horizons result in increased dissolved Hg T concentrations unrelated to DOC mobilization following precipitation events. Although flushing of DOC-Hg T complexes from surface soils can also occur during this period, DOC-complexed Hg T becomes more important during base flow conditions. TOPLOAD simulations highlight saturated subsurface flow as a primary driver of daily Hg T loadings, but shallow subsurface flow is important for Hg T loads during high-flow events. Results suggest limited seasonal trends in Hg T dynamics.

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Section: Methodsmentioning

confidence: 99%

Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

et al. 2012

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“…The model has three main modules that compute daily mass balances of hydrology, sediment, and mercury within each GIS raster grid cell [31,32]. Here we use a 90-m grid cell resolution for all GBMM simulations, which totals over 40,000 grid cells for the analysis.…”

Section: Grid-based Mercury Modelmentioning

confidence: 99%

“…The equations have been further modified and applied as the GIS-based Watershed Characterization System [41] to estimate Hg loading from different land cover sources at the watershed scale [6] and are incorporated into GBMM mercury, sediment, and hydrology calculations [31]. The mass balance of Hg at the watershed outlet is simulated based on Methylmercury is calculated as a weighted average per day based on land cover type and literature values estimating land- cover-specific percent methylmercury (Table 1) and the proportion of total daily Hg from each land cover type delivered to the stream outlet.…”

Section: Grid-based Mercury Modelmentioning

confidence: 99%

“…We calculated rate constants K r , K l , K ro , and K se , and used default values for all other parameters (Supplemental Data, Extended Model Equations and Table S1). A sensitivity analysis for GBMM was previously conducted in the Brier Creek Watershed, Georgia (USA), to identify both sensitive parameters and default parameter values for nonsensitive parameters [31,32].…”

Section: Gbmm Calibrationmentioning

confidence: 99%

“…Our research is implemented using an existing watershed Grid-Based Mercury Model (GBMM) [31,32], one of the first spatially explicit, process-based watershed scale mercury models, and a NO 3 -N watershed flux model we developed that links to GBMM. This approach allows us to maintain the spatial integrity of land cover types throughout the watershed, rather than lumping land cover types together; thus, land cover conversions are made at each Geographic Information System (GIS) pixel location of the previous land cover classification.…”

Section: Introductionmentioning

confidence: 99%

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Simulated watershed mercury and nitrate flux responses to multiple land cover conversion scenarios

Golden

Knightes

2011

Enviro Toxic and Chemistry

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Water quality and toxic exposure science is transitioning towards analysis of multiple stressors rather than one particular environmental concern (e.g., mercury) or a group of similarly reacting chemicals (e.g., nutrients). However, two of the most important water quality constituents affecting both human and ecosystem health today, reactive nitrogen (N(r) ) and methylmercury (MeHg), are often assessed separately for their independent effects on water quality. With the continued pressure of landscape modifications on water quality, a challenge remains in understanding the concurrent watershed flux response of both N(r) and MeHg to such physical stressors, particularly at the spatial scale (regional watersheds) and within the mixed land cover type systems that most decision-making processes are conducted. We simulate the annual average and monthly flux responses of Hg (MeHg and total mercury [HgT]), NO(3) -N, and runoff to four land cover change scenarios in the Haw River Watershed (NC, USA), a headwater system in the Cape Fear River Basin. Fluxes are simulated using a process-based, spatially explicit watershed Grid-Based Mercury Model (GBMM) and a NO(3) -N watershed flux model we developed to link to GBMM. Results suggest that annual NO(3) -N and Hg fluxes increase and decrease concomitantly to land cover change; however, the magnitude of the changes in NO(3) -N, MeHg, HgT, and water fluxes vary considerably between different land cover conversion scenarios. Converting pasture land to a suburbanized landscape elicited the greatest increase in runoff and MeHg, HgT, and NO(3) -N fluxes among all four conversion scenarios. Our findings provide insight for multi-stressor ecological exposure research and management of coastal eutrophication resulting from elevated N(r) loadings and exposure risk due to elevated concentrations of MeHg in fish tissue.

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Association of dissolved mercury with dissolved organic carbon in U.S. rivers and streams: The role of watershed soil organic carbon

Stoken

Riscassi

Scanlon

2016

Water Resources Research

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Streams and rivers are important pathways for the export of atmospherically deposited mercury (Hg) from watersheds. Dissolved Hg (HgD) is strongly associated with dissolved organic carbon (DOC) in stream water, but the ratio of HgD to DOC is highly variable between watersheds. In this study, the HgD:DOC ratios from 19 watersheds were evaluated with respect to Hg wet deposition and watershed soil organic carbon (SOC) content. On a subset of sites where data were available, DOC quality measured by specific ultra violet absorbance at 254 nm, was considered as an additional factor that may influence HgD:DOC . No significant relationship was found between Hg wet deposition and HgD:DOC, but SOC content (g m−2) was able to explain 81% of the variance in the HgD:DOC ratio (ng mg−1) following the form: HgD:DOC=17.8*SOC−0.41. The inclusion of DOC quality as a secondary predictor variable explained only an additional 1% of the variance. A mathematical framework to interpret the observed power‐law relationship between HgD:DOC and SOC suggests Hg supply limitation for adsorption to soils with relatively large carbon pools. With SOC as a primary factor controlling the association of HgD with DOC, SOC data sets may be utilized to predict stream HgD:DOC ratios on a more geographically widespread basis. In watersheds where DOC data are available, estimates of HgD may be readily obtained. Future Hg emissions policies must consider soil‐mediated processes that affect the transport of Hg and DOC from terrestrial watersheds to streams for accurate predictions of water quality impacts.

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Characterizing Spatial and Temporal Dynamics: Development of a Grid-Based Watershed Mercury Loading Model

Cited by 9 publications

References 2 publications

Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

Simulated watershed mercury and nitrate flux responses to multiple land cover conversion scenarios

Association of dissolved mercury with dissolved organic carbon in U.S. rivers and streams: The role of watershed soil organic carbon

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