Pollutant emissions are significantly altering the chemical composition of the atmosphere and its impacts on other earth systems. My research focuses on resolving fundamental chemical and physical processes in the troposphere and differentiating anthropogenic and natural influences.
My research focuses on the complex interactions and constraints that govern the evolution of natural landscapes, including surfaces of other planets. This research combines field studies, theory, simulation modeling, and quantitative analysis. Field studies have included evolution of channels in badlands, the natural regime and man’s influence on the Colorado River in the Grand Canyon, and the role of groundwater sapping in erosion of sandstone canyons in the southwest U.S..
My general field of interest is low-temperature aqueous geochemistry, encompassing problems in water-rock interactions, kinetics of geochemical reactions, and evolution of groundwater chemistry in various hydrogeological environments. My research includes elements of field studies, laboratory experimentation, and theoretical modeling. One research project is focused on the fate and transport of bacteria and organic contaminants in groundwater and is a collaborative effort with Messrs. Mills and Hornberger.
Convective storms, sometimes reaching into the stratosphere, play a major role in maintaining the heat balance of the atmosphere and in governing the vertical distribution of critical trace gases and aerosols. Work involving the coupling of the deeper atmosphere to the surface and boundary layers is being conducted over the tropical Atlantic and Pacific. Other studies, which capitalize upon knowledge of convective storms and the boundary layer, include global and regional rainfall, gaps in the rainforest and low-frequency sound transmission.
My biogeochemical research includes investigations on the natural and anthropogenic controls on chemical cycles at the watershed, regional and global scales. I started first with trace metal biogeochemistry of the coastal ocean, and then expanded to investigations on the increased acidification of the atmosphere, soils and fresh waters. My current research focuses on beneficial and detrimental effects of reactive nitrogen as it cascades between the atmosphere, terrestrial ecosystems and freshwater and marine ecosystems. My most recent work examines how to maximize the use of nitrogen for
I am broadly interested in understanding how coastal wetlands respond to sea level rise. Current research focuses on:
1. Plant community composition and soil genesis as salt marshes move overland into upland ecosystems as sea level rises.
2. The contribution of plant roots to marsh surface elevation change and soil organic matter content.
3. Quantification of soil component content including living roots, peat, air, water, sand, and rock and shell through the use of Computer-aided X-ray Tomography (CAT-scans).
Prior to retirement in May 2018, my primary teaching interests were physical geology, landscape evolution, petrology, economic ore deposits, and environmental geology. I am also interested in the geology of Virginia and the tectonic evolution of the state and mid-Atlantic region, as well as the geology and ecology of US National Parks.
