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Influence of a carbon amendment on nutrient and metal concentrations at a managed aquifer recharge site
Managed aquifer recharge (MAR) can increase groundwater supply and improve water quality during infiltration of surface water. Subsurface biogeochemistry can be modified with a carbon amendment, such as wood chips, which can help to stimulate microbial processes. Carbon-rich soil amendments have been shown to increase denitrification and reduce N loading, but these same amendments may create conditions favorable for mobilizing redox sensitive elements, including trace metals.

We are conducting a series of field and lab experiments to better understand the influence of varying carbon amendments (biochar, woodchips, alfalfa and almond shells) on the ground water quality during infiltration. We are analyzing changes in nutrients (NOx, NH4, PO4, Si), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), select dissolved metals (such as Fe, Mn, and As) and microbial communities (16srRNA). 

Keywords: Hydrogeology, Biogeochemistry, Groundwater resources



Evaluating the drivers of mercury uptake in naturally occurring phytoplankton communities

Mercury is a potent neurotoxin that bioaccumulates in aquatic food webs, increasing 10-fold with each trophic level. However, very little is known about how phytoplankton at the base of the food web take up mercury, even though this first step leads to a million-fold increase in concentration.

Our aim was to understand the impact of community size on mercury uptake and assessed whether cell size is influential as a driver in mercury uptake in coastal lagoon systems, such as San Elijo. Bioavailable mercury is produced in coastal lagoons by bacteria when oxygen levels in the water are depleted (i.e. eutrophic conditions). To resolve this we tracked the geochemical characteristics of the water, including temperature, salinity, chlorophyll, DOC, nutrients, and mercury concentrations, though a series of field and lab incubations.

Keywords: Trace metals, Bioaccumulation, Phytoplankton



Determine the oceans’ role in ice age cycling 

Benthic and planktonic foraminifera species can serve as proxies to determine past climate conditions which can inform us of future climate scenarios. To further resolve past climate conditions, oceanic sediment cores are extracted and foraminifera are separated by species and radio-carbon dated. 

Keywords: Paleo-oceanography, Paleo-climatology



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