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Simulated Response of Mercury and Nitrogen to Land Management and Land Use Change in a Large River Basin
Citation:
GOLDEN, H. E. AND C. D. KNIGHTES. Simulated Response of Mercury and Nitrogen to Land Management and Land Use Change in a Large River Basin. Presented at 2009 American Geophysical Union Fall Meeting, San Francisco, CA, December 14 - 18, 2009.
Impact/Purpose:
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Description:
Increases in nitrogen cascading from headwater systems to coastal waterways and bioaccumulation of mercury in aquatic ecosystems have become primary environmental concerns in recent decades. Studies assessing the effects of land use or climate change on water quality in large river basins, however, typically focus on one particular chemical constituent (e.g., inorganic nitrogen) or a group of similarly reacting chemicals (e.g., nutrients). Rarely have long-term studies or management decisions simultaneously focused on excess nitrogen, a nutrient linked to coastal eutrophication, and methyl mercury (MeHg), a neurotoxin linked to multiple human health effects. This is unfortunate, as strategies focusing exclusively on reducing nitrogen in surface waters might counteract efforts to attenuate mercury, and vice versa. For example, the presence of extensive riparian wetland areas within a watershed provides a sink for nitrogen by promoting denitrification, but these anoxic conditions may also enhance mercury methylation, thereby potentially increasing methyl mercury fluxes to surface waters. On the other hand, nutrient management strategies may concurrently reduce mercury exposure. We simulate concurrent long-term changes in loadings of total mercury (THg), MeHg, and nitrate-nitrogen (NO3-N) using a spatially distributed grid-based watershed mercury model (GBMM) linked to a simple watershed nitrogen process model, both of which receive inputs from a regional atmospheric model (CMAQ). We assess change in the fluxes of each, in response to modifications in land use practices and land cover change, and discuss potential implications for targeting nitrogen and mercury reductions in large river basins. Our work focuses on linking regional watershed and atmospheric models in the Cape Fear River Basin, North Carolina. This large river basin is located in the Coastal Carolinas, one of the place-based research initiatives within the broader US Environmental Protection Agency (USEPA) Ecosystems Services Research Program (ESRP). The ESRP focuses on modeling and evaluating the long-term effects of diverse stressors on nutrient and contaminant fluxes and consequently on ecosystem services, particularly in estuarine systems. Our findings provide a window to the temporally linked dynamics of mercury and nitrate in response to land cover and management practices, and may therefore guide future watershed management.
URLs/Downloads:
GOLDEN 09 105 AGU ABSTRACT.PDF (PDF, NA pp, 10 KB, about PDF)GOLDEN 09 105A_AGUFALL2009_FINAL.PDF (PDF, NA pp, 746 KB, about PDF)