Research Interests

My research questions:
 
What can metals tell us about critical zone processes?
How do plants, invertebrates, humans affect essential and toxic metals in soils?

 
 
Weathering and secondary mineral controls on metals in the Critical Zone
 

  • The retention and loss of metals during the development of soil is a central question for understanding nutrient balances and the formation of important geologic deposits. My research conducted across the Critical Zone Observatories Network examines the processes that promote retention of certain metals as rock weathers to soil. Specifically, how are metals retained in secondary minerals or sorbed to organic matter. Our primary tools are the use index, immobile metals and metal ratios as tracers for these processes. One metal system of interest is the Ga to Al ratio, which can inform us about the retention of Al during soil formation. In particular, I am interested in quantifying how precipitation of Fe and Al secondary minerals influences the retention of Al in soils. In addition, I am working to quantify Al other metal losses relative to immobile elements like Ti and Zr. I plan to use field samples and laboratory experiments for my project.
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    Soil metal biogeochemistry
     
     
     
     
    Plant controls on soil metal biogeochemistry

       

    • Plants need certain metals to meet for chemical signaling, enzyme cofactors, and many other roles associated with their biochemistry. To meet this need plants, absorb plant-essential metals and non-essential metals. This uptake of metals leads to preferential retention of metals in soils. I am interested in continuing studies on how plants exert control on the retention of their plant-nutrient metals and non-essential toxic metals in soils.

     

  • In plant-dominated ecosystems, such as the temperate and subtropical forests of the United States, vegetation control how soils form and how they function. The decomposition of leaves and growth of roots have strong influences on the chemistry of soils. I am conducting laboratory-based and field studies on the role of organic matter derived from vegetation controls the geochemistry of the evolution of the critical zone.
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    plant soil metal biogeochemistry
     
     
     
     
    Earthworm influences on soil metal biogeochemistry

       

    • Earthworms are an expanding source of environmental change in the northeastern United States. Their effects on carbon and nitrogen are likely to affect the retention of plant nutrient and toxic metals. I have conducted laboratory experiments to determine how earthworms affect soil properties such as soil morphology and metal chemistry. Using mesocosm or “pots” studies and field sampling campaigns, I have sought to quantify the how earthworms ecophysiology (what they eat and how they move in the soil) have affected metal pools in forest soils across the northeast US. We found that earthworms enhance the decomposition of the forest floor but did not alter the bioavailbility of metals in the mesocosms. I have also conducted soil columns coupled with synchrotron techniques (micro-XRF and XANES) to look at mobilization and stabilization by earthworms.

     
    Soil morphology of earthworm invaded soils
     
     
     
     
    Human influences on soil metal biogeochemistry

    • Humans have drastically impacted the concentration of metals in soils through atmospheric pollution and land-use changes. Of the metals released into the atmosphere, I have focused my research on lead (Pb) and mercury (Hg), two widely released and toxic metals found in the forest soils of the northeastern United States. My research methods have quantified their accumulation and retention rates in forest soils at a first order approximation using empirical data. Previous studies I have conducted examined the spatial, temporal, and vertical distribution of these metals. Moreover, I have examined how forest structure affects their cycling in soils. Future studies will address how human impacts such as land use affects Pb and Hg retention in soil.

    human mercury Hg pollution critical zone