Nitrate enhancement of in-situ bioremediation of monoaromatic compounds in groundwater

Removal of benzene, toluene, and the isomers of xylene (BTX) from gasoline-contaminated groundwater under denitrifying conditions was investigated. In laboratory microcosms, benzene removal was found to be significantly stimulated by phosphorus addition. For total xylenes, removal followed a similar response, but toluene disappearance was unaffected by phosphorus enrichment. An in-situ bioremediation project was conducted to extend this laboratory work to an actual field-scale cleanup of gasoline-contaminated groundwater. The flow of groundwater from two extraction wells to an infiltration gallery created a mostly closed loop to recycle the groundwater enriched with added nutrients and the electron acceptor (nitrate). The coincident occurrence of BTX loss (greater than 90 percent) in situ, nitrate (as well as phosphorus and ammonia) appearance, and increased levels of denitrifying bacteria at a downgradient well all suggested that denitrification may play a significant role in BTX remediation at this site.     

Modelling mining: Open pit copper production in British Columbia

Open pit copper mining in British Columbia is modelled to examine how different price levels affect rates of output and stocks of reserves and to consider the existence and distribution of economic rents. The model depicts the influence of different economic circumstances on production plans, for example, with respect to scale of operations and cutoff grade. To achieve this it represents a balance between the high level of abstraction which has characterized the writing of most economists and the degree of detail and complexity required of models used by operating mines. The model provides a basis for the study of the consequences of alternative forms of taxation, a subject to be pursued in subsequent articles.     

SOIL CONSERVATION PRACTICES AND WATER QUALITY: IS EROSION CONTROL THE ANSWER?1

ABSTRACT: This paper is a computer simulation analysis of an agricultural nonpoint pollution problem. Computer modeling is a universally applicable tool that can be used for establishing the linkages between and the quality of agricultural runoff in both surface and subsurface flow. The tradeoffs between the costs of soil conservation practices and water quality are reported, and the economic implications of such tradeoffs are discussed. Soil and nutrient losses resulting from crop production practices are analyzed using a field-scale computer simulation model (CREAMS). No-till planting, reduced tillage, and sod waterway systems are more cost effective than other practices for controlling soil and nutrient runoff losses. Nitrate leaching losses are increased slightly by most soil conservation practices. Terrace systems and permanent vegetative cover impose the greatest societal cost for water quality protection. Public cost sharing and tax incentives encourage farmers to adopt expensive structural practices, and policies are needed to get cost-effective practices implemented on critical acreage. Extensive treatment of land is necessary for agricultural best management practices (BMPs) to significantly improve water quality in areas that are intensively farmed.     

Mitigation translocation as a management tool

Mitigation translocation is a subgroup of conservation translocation, categorized by a crisis-responsive time frame and the immediate goal of relocating individuals threatened with death. However, the relative successes of conservation translocations with longer time frames and broader metapopulation- and ecosystem-level considerations have been used to justify the continued implementation of mitigation translocations without adequate post hoc monitoring to confirm their effectiveness as a conservation tool. Mitigation translocations now outnumber other conservation translocations, and understanding the effectiveness of mitigation translocations is critical given limited global conservation funding especially if the mitigation translocations undermine biodiversity conservation by failing to save individuals. We assessed the effectiveness of mitigation translocations by conducting a quantitative review of the global literature. A total of 59 mitigation translocations were reviewed for their adherence to the adaptive scientific approach expected of other conservation translocations and for the testing of management options to continue improving techniques for the future. We found that mitigation translocations have not achieved their potential as an effective applied science. Most translocations focused predominantly on population establishment- and persistence-level questions, as is often seen in translocations more broadly, and less on metapopulation and ecosystem outcomes. Questions regarding the long-term impacts to the recipient ecosystem (12% of articles) and the carrying capacity of translocation sites (24% of articles) were addressed least often, despite these factors being more likely to influence ultimate success. Less than half (47%) of studies included comparison of different management techniques to facilitate practitioners selecting the most effective management actions for the future. To align mitigation translocations with the relative success of other conservation translocations, it is critical that future mitigation translocations conform to an established experimental approach to improve their effectiveness. Effective mitigation translocations will require significantly greater investment of time, expertise, and resources in the future.