Status and trends in bioremediation treatment technology

This article is a critical analysis of the treatment potential of bioremediation technology to degrade eight major environmental pollutants, polycyclic aromatic hydrocarbons, phenols, pentachlorophenols, creosote, polychlorinated biphenyls, trichloroethylene, chlorobenzoates, and chlorophenols. The discussion includes information on transformation mechanisms, identification of intermediate metabolites, elucidation of partial or complete pathways, effects of environmental parameters, as well as current and future industrial application. Results indicate that bioremediation used in conjunction with other physical and chemical treatment methodologies can effectively transform most prevalent nonchlorinated organic contaminants and some chlorinated contaminants, such as creosote and pentachlorophenol, into innocuous materials. Successful biodegradation of several other chlorinated organic compounds, notably polychlorinated biphenyls and trichloroethylene, is currently possible only under controlled laboratory conditions. Future successful field applications, however, appear promising.     

DIQUAT DISTRIBUTION IN WATER AFTER APPLICATION TO SUBMERSED WEEDS1

ABSTRACT: Diquat herbicide and rhodamine WT dye were applied in a lake to three 1.6 ha plots either with a polymer, which reportedly aids in sinking and confinement of aquatic herbicides, or without a polymer. Diquat and dye concentrations were measured at three different depths in the water column within the plots during the first three hours after application to determine vertical distribution of diquat and dye, and in composite samples at fixed distances from the plot up to 168 hours after application to determine movement out of the treated plots. Diquat and dye were homogeneous in the water column when no polymer was used, but were concentrated near the surface when polymer was used. This distribution may have resulted from temperature stratification. Polymer did not affect movement of diquat or dye out of the plots. The half-lives of diquat within the plots were 25 (SE=6.2) hr, 39 (SE=4.3) hr, and 25 (SE=2.0) hr. Forty-six percent of samples collected at the edges of the plots did not contain detectable diquat residues and only 66 percent of those samples with detectable diquat contained greater than the potable water tolerance (10 ppb). Diquat was not found in any samples 168 hours after application 61 m or farther from the edge of the plots. Dye and diquat concentrations were weakly correlated within and outside the plots. Dye half-lives were consistently higher than diquat, which suggests that the herbicide was removed from the water by plants and sediments more rapidly than dye.     

In‐Situ Plasma Remediation of Contaminated Soils

Plasma‐torch technology has excellent potential for cost‐effective treatment of contaminated soils and other types of buried waste material. This article describes the evolution and basic features of this technology, with emphasis on the non‐transferred plasma arc torch. In addition, selected results from both laboratory experiments and field demonstrations will show how this technology can successfully destroy hazardous/toxic materials and/or stabilize contaminants in situ so they are no longer a threat to human health and the environment. © 2001 John Wiley & Sons, Inc.     

Ecophilosophy and science

Summary This paper aims to do two main things: first, to provide an introduction to ecophilosophy by presenting a spectrum of positions that have been developed to characterise the relationship between humans and their environment; second, to examine the variety of ways in which scientific work impacts upon human thought in regard to each of these positions. The import of this discussion should be twofold: first, it should help to acquaint readers with, and hopefully, interest them in, the kinds of developments that have been occurring in the area of ecophilosophy; second, it should help to acquaint environmentally concerned people with, and, hopefully, interest them in, the relevance of science to their arguments. Although many environmentally concerned people are scientifically informed, this second aim is worth stating because a number of environmentally concerned people unfortunately remain suspicious of the role of science in general.Dr Warwick Fox is a Research Fellow at the Centre for Environmental Studies at the University of Tasmania. His first degree, in experimental psychology from the University of Western Australia, was followed by PhD in environmental philosophy. Currently his research interests are concerned with the development of a comprehensive and coherent oriented world view, from epistemology and cosmology to psychology, ethnics and politics.     

A bioeconomic model of afforestation in Southern Ontario: Integration of fiber,carbon and municipal biosolids values

This study explores the economic attractiveness of afforestation as a strategy for the joint production of fibre, carbon storage and biosolids (treated municipal sewage sludge) disposal for municipalities in Southern and Central Ontario, Canada. We use a spatial, stochastic model, the Canadian Forest Service Afforestation Feasibility Model (CFS-AFM), to simulate a range of spatial biosolids application scenarios in hybrid poplar afforestation projects. Results suggest that such joint afforestation strategies could be financially attractive. Significant cost savings can be expected through decreases in transportation distances and avoided waste disposal fees. Sensitivity analysis is used to examine the effects of variations in critical model parameters on net present values. Our findings indicate that waste disposal savings from application of biosolids on hybrid poplar plantations combined with incentives for landowners to sequester carbon can easily compete with agricultural land rental values in some regions of Ontario. Social acceptance of this kind of activity, however, may be an impediment to adoption.     

Identification of Sediment Sources in Forested Watersheds With Surface Coal Mining Disturbance Using Carbon and Nitrogen Isotopes1

Abstract: Sediments and soils were analyzed using stable carbon and nitrogen isotope ratio mass spectrometry and carbon and nitrogen elemental analyses to evaluate the their ability to indicate land‐use and land management disturbance and pinpoint loading from sediment transport sources in forested watersheds disturbed by surface coal mining. Samples of transported sediment particulate organic matter were collected from four watersheds in the Southern Appalachian forest region of southeastern Kentucky. The four watersheds had different surface coal mining history that were classified as undisturbed, active mining, and reclaimed conditions. Soil samples were analyzed including reclaimed grassland soils, undisturbed forest soils, geogenic organic matter associated with coal fragments in mining spoil, and soil organic matter from un‐mined grassland soils. Statistically significant differences were found for all biogeochemical signatures when comparing transported sediments from undisturbed watersheds and surface coal mining disturbed watersheds, and the results were attributed to differences in erosion sources and the presence of geogenic organic matter. Sediment transport sources in the surface coal mining watersheds were analyzed using Monte Carlo mass balance un‐mixing and it was found that: δ¹⁵N showed the ability to differentiate streambank erosion and surface soil erosion; and δ¹³C showed the ability to differentiate soil organic matter and geogenic organic matter. Results from the analyses suggest that streambank erosion downstream of surface coal mining sites is an especially significant source of sediment in coal mining disturbed watersheds. Further, the results suggest that the sediment transport processes governing streambank erosion loads are taking longer to reach geomorphologic equilibrium in the watershed as compared with the surface erosion processes. The dual‐isotope technique provides a useful method for further investigation of the impact of surface coal mining in the uplands of the watershed upon the geomorphologic state of the channel and the source of organic matter in aquatic systems impacted by surface coal mining.