Research Interests

Overarching Research Questions:


 


(1) What can metals and metalloids tell us about natural and human-impacted processes occurring in the Critical Zone?
 
(2) How do essential and toxic metals in soils impact plants, animals, and humans?


 

 
 
 
 

Why pursue these questions:

 
 

Pollution

  • Globally, up to 10 million people die annually from pollution related diseases.
  • Uptake of toxic metals by humans and animals can cause neurological, cardiovascular, and endocrine disorders.
  • Soils in the Critical Zone sequester pollution from reaching our crops, drinking water, and atmosphere.

 
 
 

Nutritional security and ecosystem sustainability

  • Metals are essential for humans, plants, and animals and deficiencies can cause permanent damage to our development and functioning.
  • 2 Billion people suffer from ‘hidden hunger’ from insufficient micronutrients.
  • The growth of forests (which provide wood products) and crops (for human consumption) can be reduced from insufficient micronutrients as well.

 
 

National Security

  • Trace metals and rare earth elements are important for clean energy, batteries, and smart materials.
  • Trace metal and rare earthworms deposits derived from soil and weathering are needed to meet future demand without relying on imports from other countries like China.
  • Understanding what soil processes accumulate these metals could lead to identifying new, domestic sources of these metals.

 
 
 

Current and future study areas

  • Critical Zone Observatories (Luquillo PR, Southern Sierra CA, Eel River CA, Shale Hills PA, Boulder Creek CO, Calhoun SC)
  • White mountains of New Hampshire
  • Green mountains of Vermont
  • Adirondack mountains of New York
  • Berkshire mountains of Massachusetts
  • Suburban-Urban forests of the Connecticut River Valley(Brattleboro, Springfield, Hartford)

 
 

Research project 1:
 Plant controls on soil metal biogeochemistry
 

plant soil metal biogeochemistry

  • Plants need an assortment of metals and metalloids 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 from soils (and atmospheric deposition to an extent). The uptake of metals by plants causes to preferential retention of metals in soils. Moreover, soils and atmospheric deposition may not meet plant needs, potentially limiting plant growth. This is important for long-term soil fertility and soil geochemistry.
     

    • Metals of interest include:
      • Calcium
      • Magnesium
      • Manganese
      • Copper
      • Zinc
      • Cobalt
      • Nickel
      • Molybdenum
      • Chromium
      • Vanadium

       
       

  • Geochemical tools to quantify plant uptake of metals:
    • Sequential extractions of soils to determine mobility of metals.
    • Metal ratios (.e.g Mn/Ca) to examine provenance.
    • Stable isotopes (e.g. Ca, Mg) to investigate genesis.
    • Micro-XRF to probe physical and biological components.
    • SEM-EDS  for examining physical distribution.

 

Research project 2:
Human influences on toxic and potentially-toxic metals
human mercury Hg pollution critical zone

     

  • Humans have drastically impacted the concentration and pools of many metals in forest and urban soils through atmospheric pollution and land-use changes. 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 current and future forest composition affects their cycling in soils.
     

    • Metals of interest:
      • Mercury
      • Lead
      • Cadmium
      • Zinc
      • Copper
      • Antimony
      • Chromium
      • Uranium

 

  • Geochemical tools to quantify toxic metals:
    • Sequential extractions of soils to determine mobility of metals.
    • Stable isotopes (e.g. Ca, Mg) to investigate genesis.
    • Micro-XRF to probe physical and biological components.
    • SEM-EDS  for examining physical distribution.
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Research project 3:
Weathering and secondary minerals impacts on metals in the Critical Zone

Soil metal biogeochemistry

  • The accumulation and retention of metals during weathering of primary minerals and secondary minerals central to quantifying soil development and the formation of important geologic deposits. My research across the Critical Zone Observatories Network is examining the processes that promote retention of metals as bedrock and primary minerals weather.
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  • Humans rely on products derived from weathering, in particular geologic resources (bauxite, laterites, etc). Determining the processes that govern metals and rare earth elements in soils is key for identifying economically-valuable deposits. Because many metals and rare earth elements are key for clean energy technology (e.g. solar panels and batteries) and digital components (chips and smart materials in laptops, tablets, and cell phones), determining the natural processes that control their accumulation during weathering is of importance for national security.
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  • Geochemical tools to understand weathering and secondary minerals:
    • Ga to Al ratios
    • Ga to Fe ratios
    • Gallium isotopes
    • Rare earth elements ( e.g. Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb)
    • Ti and Zr as index elements

     
     

Research project 4:Earthworm influences on soil metal biogeochemistry

    Soil morphology of earthworm invaded soils

    • Exotic and invasive earthworm species are an expanding source of environmental change in the northeastern United States. Their effects on carbon and nitrogen are affecting 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. I am very interested in their role in terrestrial bioaccumulation and their role as metal ‘vectors’ to predators.
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    • Metals of interest:
      • Mercury
      • Lead
      • Cadmium
      • Selenium
      • Copper
      • Zinc
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    • Experiments to study earthworms
      • Mesocosm or “pots” studies
      • Field sampling campaigns
      • Column leaching experiments
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    • Geochemical tools to evaluate earthworms impact on metals
      • Sequential soil extractions
      • micro-XRF (X-Ray Fluorescence)
      • XANES (X-Ray absorption near edge structure)
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