Atmospheric chemistry of organic molecules, organic photochemistry, gas phase kinetics and product analyses, tropospheric chemical modeling, air pollution monitoring, chromatographic detector development, chemiluminescent trace level detection of organics, synthetic production of organic oxidants, organic geochemistry, organic tracer development, and natural abundance isotope ratio determinations and interpretation. Groundwater chemistry and colloid characterization of subsurface aqueous systems; humic and fulvic acid interactions with radionuclides, particularly actinides; natural system interactions with pollutants in air and groundwater chemistries; natural radioactive aerosol tracers