Publications

Calcareous fens in Minnesota are spring-seepage peatlands with adistinctive flora of rare calciphilic species. Peat characteristics andgroundwater geochemistry were determined for six calcareous fens in theMinnesota River Basin to better understand the physical structure andchemical processes associated with stands of rare vegetation. Onset of peataccumulation in three of the fens ranged from abou

The occurrence, concentration, and geographical distribution of agricultural pesticides were determined in air over the Mississippi River from New Orleans, LA, to St. Paul, MN, during the first 10 days of June 1994. Air samples were collected from a research vessel by pulling air through polyurethane foam plugs at about 100 L/min for up to 24 h. Each sample was analyzed for 42 pesticides and 3 pes

Seasonal and annual variation in biomass and structure of algal assemblages of hyposaline Devils Lake were examined in relation to turbidity, ambient concentrations of major ions, trace elements and nutrients, and the standing crop of herbivores. Lake level declined during the early years of study, but rose markedly in subsequent years as historically large volumes of water flowed into this hydrol

The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The ra

Cholinesterase (ChE) activity was used as a biomarker for assessing exposure of common carp (Cyprinus carpio) to organophosphate and carbamate insecticides from irrigated agricultural waters. Carp were collected from a lake (Royal Lake) that receives most of its water from irrigation return flows and from a reference lake (Billy Clapp Lake) outside of the irrigation system. Results indicated that

Natural variations in concentrations of 18O, D, and H4SiO4 in two tributary catchments of Woods Lake in the west-central Adirondack Mountains of New York were measured during 1989–1991 to examine runoff processes and their implications for the neutralization of acidic precipitation by calcium carbonate treatment. The two catchments are similar except that one contained a 1.3 ha beaver pond. Evapor

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) are highly hydrophobic compounds that have been implicated as carcinogens and, more recently, as estrogen disrupters. An occurrence and distribution study of these compounds in the Willamette Basin, Oregon, was conducted by the U.S. Geological Survey as part of the National Water-Quality Assessment Program. Bed sediment was collected fro

During 1992-93, 27 organochlorine compounds (pesticides plus total PCB) and 17 trace elements were analyzed in bed sediment and aquatic biota from 20 stream sites in the Willamette Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Data from each medium were compared to evaluate their relative effectiveness for assessing occurrence (broadly defined as document

Carbon dioxide and helium with isotopic compositions indicative of a magmatic source ( δ13C = −4.5 to −5‰, 3He/ 4He = 4.5 to 6.7 RA) are discharging at anomalous rates from Mammoth Mountain, on the southwestern rim of the Long Valley caldera in eastern California. The gas is released mainly as diffuse emissions from normal‐temperature soils, but some gas issues from steam vents or leaves the mount

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations. Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ~24,500 and ended by ~13,60

Landslides are common in sttep mountainous areas of Puerto Rico where mean annual rainfall and the frequency of intense storms are high. Each year, landslides cause extensive damage to property and coccasionally result in loss of life. Average population density is high, 422 people/km2, and is increasing. This increase in population density is accompanied by growing stress on the natural environme

A simulation-optimization model has been developed for the optimal management of the city of Santa Barbara's water resources during a drought. The model, which links groundwater simulation with linear programming, has a planning horizon of 5 years. The objective is to minimize the cost of water supply subject to: water demand constraints, hydraulic head constraints to control seawater intrusion, a