I investigate metals and metalloids in the Critical Zone, which is the zone from the tops of the trees down to the bottom of the groundwater. Metals and metalloids can serve as nutrients but may also be toxic to humans and wildlife, depending on their chemical properties and concentrations. My research addresses three biogeochemical topics. First, I track the transport of pollutant trace metals (e.g. lead, mercury) to determine human inputs and the natural processes that promote their sequestration. Secondly, I investigate mechanisms that control accumulation and bioavailability of macro and micronutrient metals. Third, I use metals and metalloids to quantify biogeochemical changes during soil formation and ecosystem disturbances. I use a combination of laboratory based-experiments and field sampling campaigns. For quantitative analyses, I apply mass spectrometry, x-ray based techniques (XRF, XANES, XRD), stable isotopes, and metal ratios and indices. I have studied plant-soil-rock interactions across the United States and internationally, but I primarily focus on the forests of New England and northeastern states.