Aromatic amines in aquatic ecosystems Aniline is involved in many industrial chemical processes, and its release into the environment is of concern. The kinetics and reactions of the covalent binding of aniline with humic substances have been studied in two papers by Eric J. Weber et al. and Kevin A. Thorn et al. The results corresponded to a second-order rate expression, and the reaction pathway was proposed to involve nucleophilic addition to carbonyl humic moieties. Only 10% of the humic binding sites were highly reactive and quickly saturated. The rate of binding decreased with decreasing pH. The low concentration of reactive sites found for typical dissolved organic matter led the authors to conclude that the sink for most aromatic amines in aquatic ecosystems will be the natural organic matter associated with bottom sediments. (Environ. Sci. Technol., ,his issue, 2755-63,2764-75)
multiple measurements in ecological risk assessments. The evaluation can be used to determine whether a stressor has caused or could cause harm to the environment. Their procedure evaluates three characteristics including the weight assigned to each measurement endpoint, the magnitude of responses observed in the measurement endpoint, and the concurrence among outcomes of multiple measurement endpoints. [Human and Ecological Risk Assessment 1996, 2(2), 277-304)
SOIL Landfill soil liners Compacted soil liners are an essential element of landfill leachate containment systems. However, some soils crack as they dry, leading to poorer containment in the field than laboratory studies predict. G. H. Omidi and co-workers attempted to quantitate the effect of desiccation cracking on compacted soil liners and find methods for increasing resistance to cracking. They found that compacted clay soils normally used for liner systems shrink by as much as 16% and increase hydraulic conductivity of soils by as much as two orders of magnitude as a. result of drying They found that amending the soils with 30% sand could significantly minimize both volume and conductivity changes (Water Air Soil Pollut 1996 89 91-103)
evaluate sorption kinetics of multiple metals on humic materials. The model incorporates functions which use the rate constants of individual metal species. Results of a study involving seven metals showed that the most reactive metals followed a first-order reaction during the initial reaction period, followed by a second-order reaction in longer periods with less reactive metal species. The authors state that the lumped model can be used to predict the total toxicity of complex systems such as waste dumps, landfills, or Superfund sites. (J. Environ. Qual. 1996, 25, 552-61)
Controlled test facility Controlled environment facilities are often used to study plant, soil, and environmental interactions. D. T. Tingey and colleagues developed a facility that uses solar radiation, tracking of temperature and vapor pressure deficit, control of atmospheric carbon dioxide (C0 2 ), and a large lysimeter to allow reconstruction of field soils. They designed the facility to operate continuously for several years to permit long-term studies. Initial tests comparing the facility with an adjacent weather station showed that it effectively simulated seasonal and diurnal variations in CO
laboratory and the field. E. R. Kline and colleagues compared the effects of a non-ionic surfactant on the survival, growth, and reproduction of bluegill sunfish and fathead minnows in laboratory studies and outdoor stream mesocosms. No-observed and lowest-observed effect concentrations were similar between the two testing systems. Results indicate that a safety factor in extrapolating the laboratory results to field situations may not be necessary [Environ. Toxicol. Chem. 1996 15(6) 997-1002)
WASTEWATER Household metal sources Domestic activities are a significant uncontrolled diffuse source of heavy metals, particularly zinc and copper, to sewage treatment works. S.D.W. Comber and A. M. Gunn conducted an analysis of houses in England and found a link between the concentration of copper being discharged and the age of plumbing or the quality of construction materials. They determined that domestic sources contribute 64% of the total copper load to sewage treatment systems, 93% of which came from plumbing. Zinc discharges were highest in older houses with galvanized header tanks Domestic sources contributed about 50% of the total zinc load to sewage systems Household products had low h e a w metal contents except
medicated shampoos (Zn) and washint? powders (Cd) Washine machines were also major sources Dochromium and cadmium was IPSS than 269/ of t h e total load t o t r p a r m p n t p l a n r s t h p v fnnnrl (Writer Fnvirnn Mnnnce tnpnt l
