Mercury in sediment and fish from North Mississippi Lakes

Sediments and/or fish were collected from Sardis, Enid and Grenada Lakes, which are located in three different watersheds in North Mississippi, in order to assess mercury contamination. The mean total mercury concentration in sediments from Enid Lake in 1997 was 0.154 mg Hg/kg, while 1998 sediment concentrations in Sardis, Enid and Grenada Lakes were 0.112, 0.088 and 0.133 mg Hg/kg, respectively. Sediment mercury concentrations in 1999 were similar in all three lakes but, generally lower than 1998. Mean total mercury concentrations in edible fillets of fish collected from Enid Lake in 1998 were above the human health FDA action level (>1.0 mg Hg/kg) for bass (1.40), crappie (1.69) and gar (1.89); however, tissue concentrations were less than 1.0 mg Hg/kg in carp (0.63) and catfish (0.82). Human hazard indexes for each species was 1 for both adults and children, indicating that there is a potential for toxic effects to occur. In addition, calculated consumption limits indicate that adults may consume 4–12 oz. of fish per month, depending on the species consumed. For children, 2 oz. per month may be consumed. Further studies are needed to determine the exact environmental consequences and human health impacts associated with mercury contamination in North Mississippi and the Southeastern United States.     

Practice review of five bioreactor/recirculation landfills

Five landfills were analyzed to provide a perspective of current practice and technical issues that differentiate bioreactor and recirculation landfills in North America from conventional landfills. The bioreactor and recirculation landfills were found to function in much the same manner as conventional landfills, with designs similar to established standards for waste containment facilities. Leachate generation rates, leachate depths and temperatures, and liner temperatures were similar for landfills operated in a bioreactor/recirculation or conventional mode. Gas production data indicate accelerated waste decomposition from leachate recirculation at one landfill. Ambiguities in gas production data precluded a definitive conclusion that leachate recirculation accelerated waste decomposition at the four other landfills. Analysis of leachate quality data showed that bioreactor and recirculation landfills generally produce stronger leachate than conventional landfills during the first two to three years of recirculation. Thereafter, leachate from conventional and bioreactor landfills is similar, at least in terms of conventional indicator variables (BOD, COD, pH). While the BOD and COD decreased, the pH remained around neutral and ammonia concentrations remained elevated. Settlement data collected from two of the landfills indicate that settlements are larger and occur much faster in landfills operated as bioreactors or with leachate recirculation. The analysis also indicated that more detailed data collection over longer time periods is needed to draw definitive conclusions regarding the effects of bioreactor and recirculation operations. For each of the sites in this study, some of the analyses were limited by sparseness or ambiguity in the data sets.     

INTEGRATED ASSESSMENT OF USES OF WOODY DRAWS IN AGRICULTURAL LANDSCAPES1

ABSTRACT: This study assesses economic and environmental impacts of uses of woody draws, small natural drainage areas covered by trees and shrubs in agricultural landscapes. Three agricultural uses and four alternative uses are evaluated. A net present value approach is used to compare economic impacts of uses of draws and APEX is used to evaluate the interaction between a woody draw and the contributing upland area and simulate the environmental impacts of uses of draws in the field. The study shows that relative to agricultural uses, alternative uses of draws have significant environmental benefits in terms of reducing surface runoff and sediment and associated pollutants, such as nitrogen, phosphorus and pesticides. Agricultural uses of draws are not always the most profitable option. Certain alternatives, such as curly willow and the mixed buffer, are highly profitable. Agricultural landscapes could be differentially managed to achieve both economic variability and environmental benefits. Government support is necessary to promote alternative uses of woody draws. The support can be in the form of CRP payments or market development of buffer products. Farmers and resource managers can use study results to manage woody draws and evaluate the merits of alternative policies for managing woody draws.     

Development of a High Purity Filter for High Temperature Particulate Sampling and Analysis

This paper is directed to those interested in measuring trace metals in high-temperature particulate emissions. Particulate handsheet filters with satisfactory purity, efficiency, thermal stability, cost, strength (about 1 lb/in.), and flexibility for analysis of particulates in gases up to 800°C have been made with 99.2% Si0₂ Microquartzfibers. Almost all purity requirements for optimum atomic absorption and flame emission spectrophotometric analysis for trace metals have been achieved. The filters appear highly promising for X-ray fluorescence analysis but should be further evaluated. Suitability of the filters for neutron activation analysis is uncertain and should also be further evaluated. Dioctyl phthal-ate (DOP) aerosol efficiencies of 99 to 99.99% have been achieved by using fibers of various diameters. The filters are insensitive to humidity, insoluble In most acids and organic solvents. The handsheet filters have a slightly alkaline pH, but similar filters have been made on a papermaking machine with a pH of 6.4. Cost is estimated to be about $2.00/ft².     

Valuing wildlife: a review of methods

The paper analyses the costs and benefits of conserving wildlife and reports part of a wider research project which aims to estimate the benefits of certain ecological types and habitats, and to compare the outcome of different techniques used to value wildlife. The authors outline a range of philosophical, technical and methodological problems in deriving cardinal measures of costs and benefits.     

NATIONWIDE STUDY OF THE STREAMFLOW DATA PROGRAM

During 1970 the Geological Survey conducted a study to evaluate the surface-water data collection program. Objectives were formulated, specific goals were set, a massive analysis of available data was made to determine the extent to which the present system enables the goals to be met, alternatives were considered for meeting the remaining goals, and finally, specific elements were identified for inclusion in the future program. The results of the evaluation will be used in planning the future streamflow data program. Less productive elements in the present program can be weeded out, and the effort devoted to more critically needed water data. The study provides the groundwork for redirection of efforts towards a more efficient system for satisfying present and future needs.     

Field water balance of landfill final covers

Landfill covers are critical to waste containment, yet field performance of specific cover designs has not been well documented and seldom been compared in side-by-side testing. A study was conducted to assess the ability of landfill final covers to control percolation into underlying waste. Conventional covers employing resistive barriers as well as alternative covers relying on water-storage principles were monitored in large (10 x 20 m), instrumented drainage lysimeters over a range of climates at 11 field sites in the United States. Surface runoff was a small fraction of the water balance (0-10%, 4% on average) and was nearly insensitive to the cover slope, cover design, or climate. Lateral drainage from internal drainage layers was also a small fraction of the water balance (0-5.0%, 2.0% on average). Average percolation rates for the conventional covers with composite barriers (geomembrane over fine soil) typically were less than 12 mm/yr (1.4% of precipitation) at humid locations and 1.5 mm/yr (0.4% of precipitation) at arid, semiarid, and subhumid locations. Average percolation rates for conventional covers with soil barriers in humid climates were between 52 and 195 mm/yr (6-17% of precipitation), probably due to preferential flow through defects in the soil barrier. Average percolation rates for alternative covers ranged between 33 and 160 mm/yr (6 and 18% of precipitation) in humid climates and generally less than 2.2 mm/yr (0.4% of precipitation) in arid, semiarid, and subhumid climates. One-half (five) of the alternative covers in arid, semiarid, and subhumid climates transmitted less than 0.1 mm of percolation, but two transmitted much more percolation (26.8 and 52 mm) than anticipated during design. The data collected support conclusions from other studies that detailed, site-specific design procedures are very important for successful performance of alternative landfill covers.