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Biogeochemical Cycling of Mercury Coupled with a Nitrogen and Carbon Watershed Hydrology Model (VELMA)
Citation:
Davis, G., Chris Knightes, A. Abdelnour, AND M. Stieglitz. Biogeochemical Cycling of Mercury Coupled with a Nitrogen and Carbon Watershed Hydrology Model (VELMA). Presented at 8th National Monitoring Conference - Water: One Resource - Shared Effort - Common Future, Portland, OR, April 30 - May 04, 2012.
Impact/Purpose:
Watershed scale mercury modeling is just beginning to emerge and help further understanding of mercury fate, transport, and transformation within a watershed. The principle processes and equations governing mercury cycling were incorporated into VELMA (Visualizing Ecosystems for Land Management Assessment) to predict daily fluxes and concentrations of total mercury (THg) and methylmercury (MeHg) for a specified catchment. VELMA is a spatially-distributed eco-hydrological model that simulates soil water infiltration and redistribution, evapo-transpiration, surface and subsurface runoff, carbon (C) and nitrogen (N) cycling in plants and soils, and the transport of dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), and dissolved organic nitrogen (DON) from the terrestrial landscape to streams. VELMA uses a distributed soil column framework to simulate the vertical movement of water, heat, and nutrients within the soil, between the soil and vegetation, and between the soil surface and vegetation to the atmosphere. The transport of mercury species down the hillslope is accomplished through advection of dissolved mercury (aqueous phase and DOC complexed). Each soil column within the watershed accounts for mercury accumulation through governing processes of deposition, decomposition, inflows, outflows, and transformation reactions. Site and species-specific rate constants, along with complexation constants, have a significant role in mercury transport. The mercury-incorporated VELMA model has been calibrated and simulated for both WS10 of the H.J. Andrews experimental forest and McTier Creek of the Edisto River Basin. WS10 is a 0.102 km 2 forested catchment located in central Cascade Range of Oregon while McTier Creek is a 79.4 km 2 watershed in the Sand Hills of South Carolina. The seasonality of in-stream mercury concentration was low during dry summers, while mercury concentration typically peaked during the first fall storm and remained notable throughout the rainy winter season. A large flux in mercury through storm events did not always correspond to an increase of in-stream mercury concentration. At both sites simulated total mercury concentration are within range of observations and help to predict and understand mercury species at the watershed level.
Description:
Presented at 8th National Monitoring Conference - Water: One Resource - Shared Effort - Common Future, Portland, OR, April 30 - May 04, 2012
