Publications

Elemental selenium, Se(0), is a prevalent chemical form in sediments, but little is known about its bioavailability. We evaluated the bioavailability of two forms of Se(0) by generating radioisotopic 75Se(0) through bacterial dissimilatory reduction of 75SeO32- by pure bacterial cultures (SES) and by an anaerobic sediment microbial consortium (SED). A third form was generated by reducing 75SeO32- 

Sulfonylurea (SU), imidazolinone (IMI), and sulfonamide (SA) herbicides are new classes of low-application-rate herbicides increasingly used by farmers. Some of these herbicides affect both weed and crop species at low dosages and must be carefully used. Less is known about the effect of these compounds on non-crop plant species, but a concentration of 100 ng/l in water has been proposed as the th

Weekly composite rainfall samples were collected in three paired urban and agricultural regions of the Midwestern United States and along the Mississippi River during April–September 1995. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agriculture areas, was located near Lake Superior in Michigan. Herbicides were the pred

No abstract available.

Flooding that occurred in southwest Iowa during June 15–17, 1998, was the worst flood ever recorded on the Nishnabotna River, exceeding the theoretical 500-year flood calculated from peak-flow records (1922 to present). This flood was a direct consequence of severe thunderstorm activity that caused more than 4 inches of rain to fall over a large part of the Nishnabotna River Basin. In fact, a new

Natural attenuation processes such as dispersion, advection, and biogradation serve to decrease concentrations of disssolved contaminants as they are transported in all ground-water systems.  However, the efficiency of these natural attenuation processes and the degree to which they help attain remediation goals, varies considerably from site to site.  This report provides a methodology for quanti

This report documents the U.S. Geological Survey Eulerian-Lagrangian Localized Adjoint Method (ELLAM) algorithm that solves an integral form of the solute-transport equation, incorporating an implicit-in-time difference approximation for the dispersive and sink terms. Like the algorithm in the original version of the U.S. Geological Survey MOC3D transport model, ELLAM uses a method of characterist

Metals transport in the Sacramento River, northern California, was evaluated on the basis of samples of water, suspended colloids, streambed sediment, and caddisfly larvae that were collected on one to six occasions at 19 sites in the Sacramento River Basin from July 1996 to June 1997. Four of the sampling periods (July, September, and November 1996; and May-June 1997) took place during relatively

No abstract available.

Metals transport in the Sacramento River, northern California, from July 1996 to June 1997 was evaluated in terms of metal loads from samples of water and suspended colloids that were collected on up to six occasions at 13 sites in the Sacramento River Basin. Four of the sampling periods (July, September, and November 1996; and May-June 1997) took place during relatively low-flow conditions and tw

No abstract available.

No abstract available.