POLICY Sustainable development In "Wildness, Wise Use, and Sustainable Development," R. Edward Grumbine argues that the idea of sustainable development should be replaced with the idea of sustainable landscape protection. Sustainable development, wise-use privatization, and wilderness management concepts all encourage a separation between people and nature. According to Grumbine, sustainable landscape protection in the United States needs to be based on science and to emphasize protection of biodiversity and habitats over preservation of scenery and recreation. (Environ. Ethics 1994, 16, 227-49)
REMEDIATION
Lead in forested ecosystems Atmospheric transport of lead has led to global distribution of the toxic metal. However, low levels of lead in surface and groundwater have made it difficult to assess lead inventories and soil lead-water interactions in forested ecosystems because of laboratory contamination. E. X. Wang, F. H. Bormann, and G. Benoit use ultraclean laboratory techniques to analyze natural waters from the Hubbard Brook Experimental Forest to evaluate the impact of soil lead. The results indicate that industrial lead in forest soil horizons is almost entirely retained. Lead in streams is associated with particulate matter, derived from surface soil debris; dissolved lead in streams originating from soil percolates is virtually nonexistent. (Environ. Sci. Technol., this issue, 735).
Organoclays and PCP Pentachlorophenol (PCP), a biocide used as a wood preservative, often contaminates soils at wood-preserving sites. J. M. Brixie and S. A. Boyd evaluated the effectiveness of nine organoclays in reducing leachable concentrations of PCP from contaminated soils. The organoclays consisted of smectite modified with different quaternary ammonium cations containing alkyl hydrocarbon groups. Two types of organoclays were synthesized: organophilic clays with large alkyl hydrocarbon groups and adsorptive organoclays with small hydrocarbon groups. The organophilic clays were the most effective in reducing the leachability of PCP from soil (as measured by the TCLP procedure), where a 20% (w/w) addition reduced PCP concentration from 16.9 mg/L to below detection limits (0.2 mg/L). However, a large decrease in TCLP-extractable PCP was observed with additions of as little as 2% (w/w) organoclay to contaminated soil. The authors conclude that organophilic clay amendments have the potential to effectively reduce PCP leaching in contaminated soils. (/. Environ. Quai. 1994, 23, 1283-90)
Soil vapor extraction One accepted technique for the removal of volatile organic compounds from contaminated vadose zones is soil vapor extraction (SVE). The
technology, however, is limited to soils with a high vapor permeability. Uwe Frank reports on a Superfund Innovative Technology Evaluation of pneumatic fracturing extraction to enhance SVE in low-permeability soils. The proprietary technique injects bursts of compressed air into narrow 2-foot intervals of one or more bore wells, resulting in a fractured subsurface environment. At the demonstration site, airflow through a sand/siltstone shale underlay increased an average of 600%, resulting in a 675% increase in the mass removal rate of trichloroethene (TCE), based on a single fracture extraction well. Adding passive air inlets to the system enhanced TCE mass removal as much as 2300% compared to prefracture test results. [J. Air Waste Manage. Assoc. 1994, 44, 1219-23)
RISK
ASSESSMENT
illustrating how exposure models can analyze health effects and establish ambient water quality goals, this study is unique in employing a Monte Carlo simulation to identify specific components of model uncertainty. Those identified uncertainties caused by incomplete or incorrect knowledge can then be reduced by investing time and resources toward more perfect data collection, creating a better exposure model and more accurate risk assessment. [Risk Anal. 1994, 14(4), 405-19)
SOILS Alum sludge application The disposal of alum sludge from drinking water treatment systems by land application has been investigated as an alternative to traditional disposal methods. The long-term environmental impact of the land application of a conventional alum sludge to a fine, loamy soil was studied by Wesley S. Geertsema and colleagues. A second study by Jay B. Lucas and others addressed the impact on plant growth from alum sludge application. The first study demonstrated no adverse effects on soil quality, groundwater quality, soil water quality, or plant growth 30 months after loading of forest lands with 1.5-2.5% dry weight of alum sludge. No significant migration of metals through soil or groundwater was observed, nor was there any contamination by nitrates. The second study demonstrated that 1-2% loadings of alum sludge reduced the growth of fescue grass under greenhouse conditions, but supplemental phosphorus could overcome this effect. Higher sludge loading rates increased manganese and copper levels in plant tissue but minimally affected plant growth. Both studies support land application as an alternative to traditional alum sludge disposal methods. (J. AWWA 1994, 86, 64-83)
Exposure models Probabilistic exposure models, an important part of ecological risk assessment, can be used to estimate exposure, establish remedial action goals, and identify model uncertainties. David Macintosh and Glen Suter show how two probabilistic food web exposure models assess the effects of PCBs and mercury on mink and great blue heron. Besides
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Pesticide degradation Cell-free enzymes have been used successfully in aqueous systems to transform pesticides into safer metabolites. These enzymes could provide an in-situ method for detoxifying contaminants in soil environments. Liliana Gianfreda and JeanMarc Bollag studied the behavior
