Publications

In January 1999, wastewater influent and effluent from the pretreatment plant at the Stringfellow hazardous waste disposal site were sampled along with groundwater at six locations along the groundwater contaminant plume. The objectives of this sampling and study were to identify at the compound class level the unidentified 40–60% of wastewater organic contaminants, and to determine what...

Rhodamine WT dye-tracer injections in rivers of the Willamette Basin yield concentration-time curves with characteristically long recession times suggestive of active transient storage processes. The scale of drainage areas contributing to the stream reaches studied in the Willamette Basin ranges from 10 to 12,000 km2. A transient storage assessment of the tracer studies has been...

Mineralization of [U-14C] methyl t-butyl ether (MTBE) to 14CO2 without accumulation of t-butyl alcohol (TBA) was observed in surface-water sediment microcosms under denitrifying conditions. Methanogenic activity and limited transformation of MTBE to TBA were observed in the absence of denitrification. Results indicate that bed sediment microorganisms can effectively degrade MTBE to...

Many published studies have used visual comparison of the timing of peak breakthrough of colloids versus conservative dissolved tracers (hereafter referred to as dissolved tracers or tracers) in subsurface media to determine whether they are advected differently, and to elucidate the mechanisms of differential advection. This purely visual approach of determining differential advection...

A house exploded in the City of Kingsford, Michigan USA. The explosion was caused by CH4 that leaked into the basement from the surrounding soil. Evidence suggests that biodegradation of products from the distillation and spillage at or near a former wood carbonization plant site was the major source of CH4 and CO2 in the groundwater system. The plant area is directly upgradient from...

An evaluation of over 75 pesticides by high-performance liquid chromatography/mass spectrometry (HPLC/MS) clearly shows that different classes of pesticides are more sensitive using either atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI). For example, neutral and basic pesticides (phenylureas, triazines) are more sensitive using APCI (especially positive...

The concentration and distribution of inorganic Hg was measured using cold-vapor atomic fluorescence spectrometry in samples collected at selected sites on the Sacramento River from below Shasta Dam to Freeport, CA, at six separate times between 1996 and 1997. Dissolved (ultrafiltered, 0.005 μm equivalent pore size) Hg concentrations remained relatively constant throughout the system...

Three pilot studies were performed to assess application of the eddy covariance micrometeorological method in the measurement of carbon dioxide (CO2) flux of volcanic origin. The selected study area is one of high diffuse CO2 emission on Mammoth Mountain, CA. Because terrain and source characteristics make this a complex setting for this type of measurement, added consideration was given...

Pesticide degradates account for a significant portion of the pesticide load in surface water. Because pesticides with similar structures may degrade to the same degradate, it is important to distinguish between different sources of parent compounds that have different regulatory and environmental implications. A discrimination diagram, which is a sample plot of chemical data that...

The Yukon River Basin, which encompasses 330,000 square miles in northwestern Canada and central Alaska (Fig. 1), is one of the largest and most diverse ecosystems in North America. The Yukon River is also fundamental to the ecosystems of the eastern Bering Sea and Chukchi Sea, providing most of the freshwater runoff, sediments, and dissolved solutes. Despite its remoteness and perceived

Geochemical reaction models were evaluated to improve radiocarbon dating of dissolved inorganic carbon (DIC) in groundwater from confined parts of the Upper Floridan aquifer in central and northeastern Florida, USA. The predominant geochemical reactions affecting the 14C activity of DIC include (1) dissolution of dolomite and anhydrite with calcite precipitation (dedolomitization), (2)...

Using extended X-ray absorption fine structure (EXAFS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) measurements, we examined the sorption of Pb(II) to hematite in the presence of malonic acid. Pb LIII-edge EXAFS measurements performed in the presence of malonate indicate the presence of both Fe and C neighbors, suggesting that a major fraction of surface-bound...