Can adsorption isotherms predict sediment bioavailability?

The adsorption and desorption of 2,4-dichlorophenol (DCP) and pentachlorophenol (PCP) were studied for a range of synthetic particles, a dimethylditallowammonium exchanged clay and a natural sediment. The synthetic particles were Dowex 1X8400, Toyopearl Phenyl 650M and Toyopearl SP 650M. The bioaccumulation of the DCP and PCP from these particles was then studied using the oligochaete, Lumbriculus variegatus. There is a correlation between contaminant-particle interactions, as determined from adsorption and desorption isotherms, and bioaccumulation. Bioaccumulation by L. variegatus was found to be highest from the systems where differences in the classification of adsorption and desorption isotherms were observed.     

Thermal degradation of fluorotelomer treated articles and related materials

This study reports the first known studies to investigate the thermal degradation of a polyester/cellulose fabric substrate ("article") treated with a fluorotelomer-based acrylic polymer under laboratory conditions conservatively representing typical combustion conditions of time, temperature, and excess air level in a municipal incinerator, with an average temperature of 1000 degrees C or greater over approximately 2s residence time. The results demonstrate that the polyester/cellulose fabric treated with a fluorotelomer-based acrylic polymer is destroyed and no detectable amount of perfluorooctanoic acid (PFOA) is formed under typical municipal incineration conditions. Therefore, textiles and paper treated with such a fluorotelomer-based acrylic polymer disposed of in municipal waste and incinerated are expected to be destroyed and not be a significant source of PFOA in the environment.     

THE UNITED NATIONS GROUND WATER EXPLORATION AND DEVELOPMENT PROGRAMME - A FIFTEEN YEAR PERSPECTIVE

The United Nations ground water exploration and development programme during 15 years of active life, has resulted in substantial socio-economic benefits to 57 developing countries through some 100 ground water projects. Systematic study, development and use of this important resource have contributed to intensification of agricultural production through supplemental irrigation from ground water; alleviation of water shortages in urban and industrial areas through construction of supply wells; improvement and stabilization of pastoral and rural economies, thereby counteracting in some measure adverse demographic trends of migration to the cities; and other related benefits in training, institutional development, and development of national water policies and plans.     

Temporal and spatial variability in water quality of wetlands in the Minneapolis/St. Paul,MN metropolitan area: Implications for monitoring strategies and designs

Temporal and spatial variability in wetland water-quality variables were examined for twenty-one wetlands in the Minneapolis/St. Paul metropolitan area and eighteen wetlands in adjacent Wright County. Wetland water quality was significantly affected by contact with the sediment (surface water vs. groundwater), season, degree of hydrologic isolation, wetland class, and predominant land-use in the surrounding watershed (p<0.05). Between years, only nitrate and particulate nitrogen concentrations varied significantly in Wright County wetland surface waters. For eight water-quality variables, the power of a paired before-and-after comparison design was greater than the power of a completely randomized design. The reverse was true for four other water-quality variables. The power of statistical tests for different classes of water-quality variables could be ranked according to the predominant factors influencing these: climate factors>edaphic factors>detritivory>land-use factors>biotic-redox or other multiple factors.For two wetlands sampled intensively, soluble reactive phosphate and total dissolved phosphorus were the most spatially variable (c.v.=76–249%), while temperature, color, dissolved organic carbon, and DO were least variable (c.v.=6–43%). Geostatistical analyses demonstrated that the average distance across which water-quality variables were spatially correlated (variogram range) was 61–112% of the mean radius of each wetland. Within the shallower of the two wetlands, nitrogen speciation was explained as a function of dissolved oxygen, while deeper marsh water-quality variables were explained as a function of water depth or distance from the wetland edge. Compositing water-quality samples produced unbiased estimates of individual sample means for all water quality variables examined except for ammonium.     

Statistical modeling of restricted pollutant data sets to assess compliance with air quality criteria

Three statistical models are used to predict the upper percentiles of the distribution of air pollutant concentrations from restricted data sets recorded over yearly time intervals. The first is an empirical quantile-quantile model. It requires firstly that a more complete date set be available from a base site within the same airshed, and secondly that the base and restricted data sets are drawn from the same distributional form. A two-sided Kolmogorov-Smirnov two-sample test is applied to test the validity of the latter assumption, a test not requiring the assumption of a particular distributional form. The second model represents the a priori selection of a distributional model for the air quality data. To demonstrate this approach the two-parameter lognormal, gamma and Weibull models and the one-parameter exponential model were separately applied to all the restricted data sets. A third model employs a model identification procedure on each data set. It selects the best fit model.     

Tolerance to SO2, NO2 and their mixture in Plantago major L. populations

The possible evolution of tolerance to NO2, alone or in combination with SO2 was investigated in three populations of Plantago major L., originating from Hyde Park in central London (polluted site), Ascot (clean site) and The Netherlands. Screening for sensitivity to the pollutants was carried out by means of chronic fumigations with NO2 or NO2 plus SO2 and acute fumigations with SO2, NO2 or their mixture. The Hyde Park population showed smaller growth reductions induced by the pollutant mixture, than did the other populations. In contrast no differential response in terms of foliar injury was observed after an acute fumigation with SO2+ NO2, but the Hyde Park population was the most sensitive to NO2 alone. The results indicate that selection for tolerance to SO2 does not confer tolerance to NO2 alone or the pollutant mixture.     

Incomplete oxidation of ethylenediaminetetraacetic acid in chemical oxygen demand analysis.

Ethylenediaminetetraacetic acid (EDTA) was found to incompletely oxidize in chemical oxygen demand (COD) analysis, leading to incorrect COD values for water samples containing relatively large amounts of EDTA. The degree of oxidation depended on the oxidant used, its concentration, and the length of digestion. The COD concentrations measured using COD vials with a potassium dichromate concentration of 0.10 N (after dilution by sample and sulfuric acid) were near theoretical oxygen demand values. However, COD measured with dichromate concentrations of 0.010 N and 0.0022 N were 30 to 40% lower than theoretical oxygen demand values. Similarly, lower COD values were observed with manganic sulfate as oxidant at 0.011 N. Extended digestion yielded somewhat higher COD values, suggesting incomplete and slower oxidation of EDTA, as a result of lower oxidant concentrations. For wastewater in which EDTA is a large fraction of COD, accurate COD measurement may not be achieved with methods using dichromate concentrations less than 0.1 N.