Publications

Storm-driven flow pulses in rivers destroy and restructure sediment habitats that affect stream metabolism. This study examined thresholds of bed disturbances that affected patch- and reach-scale sediment conditions and metabolism rates. A 4 year record of discharge and diel changes in dissolved oxygen concentrations (ΔDO) was analyzed for disturbances and recovery periods of the ΔDO...

4-Nonylphenols (4-NPs) are known endocrine disruptors and by-products of the microbial degradation of nonylphenol polyethoxylate surfactants. One of the challenges to understanding the toxic effects of nonylphenols is the large number of isomers that may exist in environmental samples. In order to attribute toxic effects to specific compounds, a method is needed for the separation and...

Land application of biosolids (treated sewage sludge) can be an important route for introducing xenobiotic compounds into terrestrial environments. There is a paucity of available information on the effects of biosolids amendment on terrestrial organisms. In this study, the influence of biosolids and biosolids aging on earthworm (Eisenia fetida) reproduction and survival and lettuce...

Improved predictions of hyporheic exchange based on easily measured physical variables are needed to improve assessment of solute transport and reaction processes in watersheds. Here we compare physically based model predictions for an Indiana stream with stream tracer results interpreted using the Transient Storage Model (TSM). We parameterized the physically based, Multiscale Model...

The first versions of the widely used groundwater flow model MODFLOW (McDonald and Harbaugh 1988) had a sure but inflexible way of handling unconfined finite-difference aquifer cells where the water table dropped below the bottom of the cell—these "dry cells" were turned inactive for the remainder of the simulation. Problems with this formulation were easily seen, including the potential...

Hi‐Desert Water District (HDWD), the primary water‐management agency in the Warren Groundwater Basin, California, plans to construct a waste water treatment plant to reduce future septic‐tank effluent from reaching the groundwater system. The treated waste water will be reclaimed by recharging the groundwater basin via recharge ponds as part of a larger conjunctive‐use strategy. HDWD...

Apparent groundwater ages along two flow paths in the upper Patapsco aquifer of the Maryland Atlantic Coastal Plain, USA, were estimated using 14C, 36Cl and 4He data. Most of the ages range from modern to about 500 ka, with one sample at 117 km downgradient from the recharge area dated by radiogenic 4He accumulation at more than one Ma. Last glacial maximum (LGM) water was located about...

Potential climate change effects on aspects of conjunctive management of water resources can be evaluated by linking climate models with fully integrated groundwater-surface water models. The objective of this study is to develop a modeling system that links global climate models with regional hydrologic models, using the California Central Valley as a case study. The new method is a...

Arsenic and Sb are common mine-water pollutants and their toxicity and fate are strongly influenced by redox processes. In this study, simultaneous Fe(II), As(III) and Sb(III) oxidation experiments were conducted to obtain rates under laboratory conditions similar to those found in the field for mine waters of both low and circumneutral pH. Additional experiments were performed under...

In this work, we present the first observations of stable water isotopologue ratios in cloud droplets of different sizes collected simultaneously. We address the question whether the isotope ratio of droplets in a liquid cloud varies as a function of droplet size. Samples were collected from a ground intercepted cloud (= fog) during the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010)...

Forty to fifty percent decreases in acidic deposition through the 1980s and 1990s led to partial recovery of acidified surface waters in the northeastern United States; however, the limited number of studies that have assessed soil change found increased soil acidification during this period. From existing data, it's not clear whether soils continued to worsen in the 1990s or if recovery...

A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004–0.7 mol kg−1), temperature (0–95 °C), pH (1–10), and conductivity (30–70,000 μS cm−1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+...