Ph.D. Geochemistry, Dartmouth College
Low Temperature Geochemistry and Environmental Mineralogy
Office Hours: by appointment
Delehanty Hall, Room 110
Hello! I am a low temperature geochemist with interdisciplinary research interests spanning the crossroads of geology, chemistry, biology and hydrology. My research has focused on understanding the evolution of biogeochemical systems in New England, New York, Montana, and Alaska in the broad context of environmental change. The overarching aim of my research is to describe geochemical processes occurring at the earth’s surface with a general focus on nutrient and pollutant mobility and cycling on present day to glacial/interglacial timescales. Specifically, my goal is to understand how biogeochemical systems are affected by global or regional environmental change such as acid and metal pollution, deglaciation, shifting tree species distribution, evolving atmospheric composition, land use modification and changes in climate patterns. My students and I develop and apply a broad array of field and laboratory approaches to study earth surface processes including: 1) watershed solute and solid mass balances, 2) quantitative characterization of soil mineralogy and profile development, 3) synchrotron-based approaches to directly determine the speciation of pollutants and nutrients in soils, dusts and suspended sediments, 4) size fractionation studies of trace metal partitioning in fresh and marine waters to study colloidal chemistry and transport mechanisms, and 5) various laboratory experiments to confirm or supplement field-based observations in a controlled setting.
In marine waters, iron is an essential micronutrient to the base of the food chain. Iron supply and bioavailability can limit primary productivity in offshore regions of the North Pacific, but controls on both are extremely poorly understood, particularly in high latitude systems. Over the past 5 years, my research at U.S. Geological Survey and now at the University of Vermont has focused on understanding trace metal cycling in Alaskan watersheds and coastal systems. My group’s primary research thrust has been to understand the role of glaciers in supplying reactive iron species to the productive marine ecosystem of the Gulf of Alaska(GoA) and developing a process-based model for the behavior of iron and other trace metals in high latitude riverine and coastal systems. Our research has suggested that glaciers play an essential role in generating a reactive terrestrial flux of iron species through both riverine and aeolian transport of Fe to the GoA, which is likely critical to the present day function of the GoA ecosystem. As we continue to learn more about this understudied high latitude nutrient cycle, we strive to view our research efforts through the prism of predicting how the system will evolve due to continued warming climate and ice loss in Alaska.
Since joining the faculty at UVM in July of 2012, I have become involved in a large interdisciplinary research project funded by NSF EPSCoR that aims to understand nutrient and algal bloom dynamics within the Lake Champlain Basin in the context of climate change and related adaptive management. I am the research team leader of what we call ‘Question 1’ of the project, which is stated as: ‘What is the relative importance of endogenous in-lake processes (e.g. internal loading, ice cover, hydrodynamics) versus exogenous to-lake processes (e.g. land use change, snow/rain timing, storm frequency and intensity, land management) to Lake Champlain eutrophication and algal blooms?’ . My primary responsibility is to coordinate a large research team of faculty, post docs, graduate and undergraduate students from UVM, Middlebury College, Saint Michaels College, and Johnson State College in a collaborative effort to describe nutrient and algal bloom dynamics in Lake Champlain and its watershed. Our diverse cross disciplinary team is well-suited to tackle this research question. We maintain a sensor and sampling network within the Missisquoi and Winooski watersheds to study exogenous nutrient dynamics and hydrology, as well as a sampling and sensor array within Lake Champlain’s Missisquoi Bay to study endogenous nutrient dynamics and physical processes in relation to algal bloom initiation, propagation and senescence. Over the next 4 years, the extensive network of time series sampling sites and sensor arrays that the research team established during the summer of 2012, coupled with targeted intensive process-based spatial sampling efforts, will allow us to obtain significant insight towards conceptually and quantitatively describing nutrient dynamics in the lake and its watershed. We believe that this study will help to provide the requisite knowledge base so that we may begin to predict how a system like the Lake Champlain Basin could evolve under changing land use and climate.
I am actively recruiting masters and undergraduate students to work on geochemical projects in both AK and VT! Interested students should contact me for more information.
Schroth, A. W., J. Crusius, et al. (2011). "Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation." Geophysical Research Letters 38.
Crusius, J., A. W. Schroth, et al. (2011). "Glacial flour dust storms in the Gulf of Alaska: Hydrologic and meteorological controls and their importance as a source of bioavailable iron." Geophysical Research Letters 38.
Schroth, A. W., J. Crusius, et al. (2009). "Iron solubility driven by speciation in dust sources to the ocean." Nature Geoscience 2(5): 337-340.
Schroth, A. W., B. C. Bostick, et al. (2008). "Lead sequestration and species redistribution during soil organic matter decomposition." Environmental Science & Technology 42(10): 3627-3633.
Schroth, A. W., A. J. Friedland, et al. (2007). "Macronutrient depletion and redistribution in soils under conifer and northern hardwood forests." Soil Science Society of America Journal 71(2): 457-468.