Assessing Effects of Climate Change on Biogeochemical Cycling of Trace Metals in Alluvial and Coastal Watersheds
Ming-Kuo Lee *
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
Michael Natter
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
Jeff Keevan
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
Kirsten Guerra
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
James Saunders
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
Ashraf Uddin
Department of Geology and Geography, Auburn University, Auburn, AL, 36839, United States.
Munir Humayun
Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306, United States.
Yang Wang
Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306, United States.
Alison R. Keimowitz
Department of Chemistry, Vassar College, Poughkeepsie, NY, 12604, United States.
*Author to whom correspondence should be addressed.
Abstract
Assessing the impacts of climate changes on water quality requires an understanding of the biogeochemical cycling of trace metals. Evidence from research on alluvial aquifers and coastal watersheds shows direct impacts of climate change on the fate and transformation of trace metals in natural environments. The case studies presented here use field data and numerical modeling techniques to test assumptions about the effects of climate change on natural arsenic contamination of groundwater in alluvial aquifers and mercury bioaccumulation in coastal salt marshes. The results show that the rises of sea level and river base during the warm Holocene period has led to an overall increase in groundwater arsenic concentration due to the development of reducing geochemical conditions and sluggish groundwater movement. Modeling results indicate that the intrusion of seawater occurring during high sea-level stand may lead to desorption of arsenic from surface of hydrous oxides due to pH effects and ionic competition for mineral sorbing sites. Our results also show that contamination and bioaccumulation of Hg and other metals in estuarine and coastal ecosystems may be influenced by climate-induced hydrologic modifications (atmospheric deposition, riverine input, salinity level, etc.).
Keywords: Biogeochemical cycle, climate change, sea level rise, trace metals, arsenic, mercury, alluvial aquifers, groundwater, saltwater intrusion, salt marsh, bacterial iron reduction, bacterial sulfate reduction.