Environmental gradients in northwest freshwater wetlands

Wetland environmental characteristics are examined to determine their spatial and temporal relationships. Two very different Oregon freshwater wetlands provided a range of wetland types. Results are evaluated to determine the possible use of environmental characteristics in defining wetlands and their boundaries. Representative physical, hydrological, and edaphic properties were periodically measured in microplots along upland/wetland transects. A multivariate approach is stressed in the data analysis; correlation, cluster analysis, and principal components analyses were used. The results indicate the environmental characteristics change in a quantifiable manner both spatially and temporally. The controlling mechanism is moisture, spatially in terms of the upland/wetland transect and temporally with respect to seasonal response. These changes do not correlate well with vegetation. Several hypotheses are offered as an explanation. Correlation within environmental characteristics is variable but definite patterns are discernible. These data suggest both single and combinations of environmental characteristics that could serve as keys in wetland identification and boundary determination. However, before extensive use is made of this information additional long-term monitoring of wetland environmental characteristics will be required.     

MODELING GROUND WATER FLOW USING FLUX BOUNDARY CONDITIONS1

ABSTRACT: Determination of the boundary conditions for modeling ground water flow is a critical point especially in regional models. Normally the regional models require model areas that are greater than the given area of interest. This work focuses on the prediction of hydraulic heads in regional models using flux boundary conditions. The model uses flux boundary conditions that were estimated using a radial flow analog and Darcy's law. The regional model that is presented uses no parameter identification (inverse estimation) procedures. In the present work, the Houston area was used. The simulation of the hydrological conditions of the Chicot and Evangeline Aquifers that underlie the Houston area were made using the available information about the geological profile in the Houston region and the current information about the existing production wells. The regional model works as a forward problem. The system parameters such as hydraulic conductivity, specific storage, and hydrological stresses were specified, and the model predicts the hydraulic head. Actual data from piezometers operated by the U.S. Geological Survey (USGS) in many places throughout Houston were used as initial conditions. Some piezometric head data were generated using the regional variable theory called kriging to supply head estimates in areas where data were unavailable. The Modular Three Dimensional Finite Difference Groundwater Flow Model developed by the USGS was used to predict the hydraulic heads. The predicted ground water heads are compared to the actual data. The results show that the model performs well for locations where data were available.     

UV peroxidation with air stripping for optimized removal of VOCs from groundwater

No one remedial technology is best suited to treat every groundwater contaminant plume. This article describes how pilot testing and analytical evaluation targeted selection of two treatment technologies, UV peroxidation and air stripping, to be used in series to create a synergistic, cost-effective pump-and-treat system for the removal of VOCs from groundwater. Pilot plant size equipment was employed to treat the VOC-contaminated groundwater in order to obtain site-specific reaction rates and to develop full-scale design parameters. It was found that by using the two treatment technologies in combination, the influent concentration of 2,000 ppb total VOCs could be reduced to less than 1 ppb, thus meeting drinking water standards.     

No bioavailability of 17α-ethinylestradiol when associated with nC60 aggregates during dietary exposure in adult male zebrafish (Danio rerio)

The C(60) fullerene is a manufactured carbon nanoparticle (CNP) that could pose a risk to humans and other organisms after release into the environment. In surface waters, C(60) is likely to be present as aggregates of nC(60) and these aggregates can associate with other substances that are toxic. Our goal was to evaluate the association of a model contaminant [17α-ethinylestradiol (EE2)] with nC(60) and determine bioavailability of EE2 after accumulation by a filter feeding organism [Brine shrimp (BS) Artemia sp.] and subsequent dietary exposure in zebrafish. Aqueous suspensions of nC(60) were prepared (600 mg C(60)/900 mL, 6-month water stirred method) with/without EE2 (1 μg/L) and BS were exposed to these preparations. Accumulation of nC(60) in gut of BS was assessed by light microscopy, and C(60) were extracted from BS and concentration analyzed by HPLC. Adult male zebrafish were fed (5d) live BS according to the following treatments: BS (control); BS containing nC(60); BS containing nC(60)+EE2; or BS containing EE2. Liver was excised from exposed fish and total RNA was extracted for assessment of vitellogenin gene (vtg1A/B) expression. The vtg1A/B was highly up-regulated in fish exposed to BS containing EE2, but expression of vtg1A/B did not differ from controls in other treatments. The EE2 associated with nC(60) did not become bioavailable in zebrafish during passage through the intestinal tract of zebrafish. Results have implications on the effect of nC(60) on the bioavailability of co-contaminants in organisms during dietary exposure.     

THE NATIONAL WATER COMMISSION REVISITED1

ABSTRACT: In 1973 the National Water Commission concluded its five-year study of national water policy by issuing a massive report containing over 200 recommendations for improvements in the way the Nation deals with its water resources. The Carter Administration is now engaged in another water policy review which incorporates many of the policies espoused by the National Water Commission. In this paper, presented at the 13th American Water Resources Conference in Tucson in November of 1977, the author describes the work of the National Water Commission and the actions taken on its recommendations.     

LABORATORY TESTS OF EROSION DEPENDENCE ON PROPERTIES OF SOILS AND RAINFALL1

ABSTRACT: One hundred and sixty-two rainfall-induced soil erosion tests were conducted to assist in predicting soil loss and subsequent increase in total suspended solids leaving a highway construction site during a rainfall event. A rainfall simulator and a water flume were constructed for the tests. Soil shear strength, compressive strength, rainfall intensity, and soil bed slope were treated as variables during the experiments. The soil with a higher shear strength resisted soil erosion better than lower strength soils. Soil loss was nearly independent of shear strength at low rainfall intensity but at high intensities, the shear strength was more important in resisting soil loss. Lower soil loss can be expected for cohesive soils if the compressive strength is high.     

Parametric cost-benefit analysis applied to underwater pipeline safety

Policy alternatives must often be evaluated without the benefit of experimentation to determine the effectiveness of each one. A parametric approach to dealing with this problem is presented for the case of deciding on the appropriate degree of deregulation, if any, for the use of signs to prevent accidents involving damage to underwater pipelines. The information obtained demonstrates whether experimentation would have been advantageous and, if so, how the policy conclusions would have been affected.