Recent advances in mercury speciation analysis with focus on spectrometric methods and enriched stable isotope applications

This paper discusses some recent advances in spectrometric methods and approaches for mercury speciation analysis of environmental samples with focus on isotope dilution techniques for determination of mercury species' concentrations in gaseous samples and reaction rates in soils and sediments. Such analytical data is important inter alia in fundamental research on mercury biogeochemistry and for risk assessments of mercury-contaminated soils and sediments and for designing effective remedial actions. The paper describes how the use of enriched stable isotope tracers in mercury speciation analysis can improve the traceability and accuracy of results, facilitate rational method developments, and be useful for studying biogeochemical processes, i.e. rate of reactions and fluxes, of mercury species. In particular the possibilities to study and correct for unwanted species transformation reactions during sample treatment and to study "natural" transformations of species in environmental samples, or micro- and mesocosm ecosystems, during incubations are highlighted. Important considerations to generate relevant data in isotope tracer experiments as well as reliability and quality assurance of mercury speciation analysis in general are also discussed.     

International trade in meat: the tip of the pork chop

This paper provides an original account of global land, water, and nitrogen use in support of industrialized livestock production and trade, with emphasis on two of the fastest-growing sectors, pork and poultry. Our analysis focuses on trade in feed and animal products, using a new model that calculates the amount of "virtual" nitrogen, water, and land used in production but not embedded in the product. We show how key meat-importing countries, such as Japan, benefit from "virtual" trade in land, water, and nitrogen, and how key meat-exporting countries, such as Brazil, provide these resources without accounting for their true environmental cost. Results show that Japan's pig and chicken meat imports embody the virtual equivalent of 50% of Japan's total arable land, and half of Japan's virtual nitrogen total is lost in the US. Trade links with China are responsible for 15% of the virtual nitrogen left behind in Brazil due to feed and meat exports, and 20% of Brazil's area is used to grow soybean exports. The complexity of trade in meat, feed, water, and nitrogen is illustrated by the dual roles of the US and The Netherlands as both importers and exporters of meat. Mitigation of environmental damage from industrialized livestock production and trade depends on a combination of direct-pricing strategies, regulatory approaches, and use of best management practices. Our analysis indicates that increased water- and nitrogen-use efficiency and land conservation resulting from these measures could significantly reduce resource costs.     

Energy use,blue water footprint,and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the US

This article measures the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with shifting from current US food consumption patterns to three dietary scenarios, which are based, in part, on the 2010 USDA Dietary Guidelines (US Department of Agriculture and US Department of Health and Human Services in Dietary Guidelines for Americans, 2010, 7th edn, US Government Printing Office, Washington, 2010). Amidst the current overweight and obesity epidemic in the USA, the Dietary Guidelines provide food and beverage recommendations that are intended to help individuals achieve and maintain healthy weight. The three dietary scenarios we examine include (1) reducing Caloric intake levels to achieve “normal” weight without shifting food mix, (2) switching current food mix to USDA recommended food patterns, without reducing Caloric intake, and (3) reducing Caloric intake levels and shifting current food mix to USDA recommended food patterns, which support healthy weight. This study finds that shifting from the current US diet to dietary Scenario 1 decreases energy use, blue water footprint, and GHG emissions by around 9 %, while shifting to dietary Scenario 2 increases energy use by 43 %, blue water footprint by 16 %, and GHG emissions by 11 %. Shifting to dietary Scenario 3, which accounts for both reduced Caloric intake and a shift to the USDA recommended food mix, increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %. These perhaps counterintuitive results are primarily due to USDA recommendations for greater Caloric intake of fruits, vegetables, dairy, and fish/seafood, which have relatively high resource use and emissions per Calorie.     

Effects of reduced contaminant loading on downgradient water quality in an idealized two-layer granular porous media

The following explores the issue of how reductions in contaminant loading to plumes will effect downgradient water quality. An idealized scenario of two adjacent layers of uniform geologic media, one transmissive and the other low permeability, is considered. A high concentration source, similar to a thin DNAPL pool, is introduced in the transmissive layer immediately above the low permeability layer. While the source is active, dissolved constituents are driven along the contact by advection and into the low permeability layer by transverse diffusion. Removing the source reverses the concentration gradient between the layers, driving back diffusion of contaminants from the low permeability layer. Laboratory studies involving four contaminants demonstrate that 15 to 44% of the introduced contaminant moves into the low permeability zone (along a distance of 87 cm in a sand tank) over a period of 25 days. The greatest movement of contaminants into the low permeability zone is seen with the contaminants with the greatest sorption coefficients. A unique two-dimensional analytical solution is developed for the two-layer scenario. Processes addressed include advection; transverse dispersion; adsorption and degradation in the transmissive zones; and diffusion, adsorption, and degradation in the low permeability layer. Laboratory data agree favorably with the analytical solutions. Collectively, the laboratory results and analytical solutions provide a basis for testing other modeling approaches that can be applied to more complex problems. A set of field-scale scenarios are considered using the analytical solutions. Results indicate that improvement in water quality associated with source removal diminish with distance downgradient of the source. Furthermore, contaminant degradation and contaminant adsorption in the stagnant zone are shown to be critical factors governing the timing and magnitude of downgradient improvements in water quality. For five of six scenarios considered, observed improvements in water quality 100 m downgradient of the source fall in the range of 1 to 2 orders of magnitude 15 years after complete source removal. The sixth scenario, involving a contaminant half-life of three years and no adsorption, shows greater than three order of magnitude improvements in downgradient water quality within one year of source removal.     

Estimation of pollutant partition in sandy soils with different water contents

The objectives of this work were: (1) to identify an isotherm model to relate the contaminant contents in the gas phase with those in the solid and non-aqueous liquid phases; (2) to develop a methodology for the estimation of the contaminant distribution in the different phases of the soil; and (3) to evaluate the influence of soil water content on the contaminant distribution in soil. For sandy soils with negligible contents of clay and natural organic matter, contaminated with benzene, toluene, ethylbenzene, xylene, trichloroethylene (TCE), and perchloroethylene (PCE), it was concluded that: (1) Freundlich’s model showed to be adequate to relate the contaminant contents in the gas phase with those in the solid and non-aqueous liquid phases; (2) the distribution of the contaminants in the different phases present in the soil could be estimated with differences lower than 10% for 83% of the cases; and (3) an increase of the soil water content led to a decrease of the amount of contaminant in the solid and non-aqueous liquid phases, increasing the amount in the other phases.     

The reproduction of Enchytraeus sp.—technical improvement for the counting of juveniles

Soil-dwelling annelids of the genus Enchytraeus are used in ecotoxicology for testing of chemicals mixed in artificial soil or for testing of wastes and soils of unknown quality. ISO 16387 describes a method for determining the effects of substances or contaminated soils on survival and reproduction of Enchytraeus albidus or of the smaller species Enchytraeus buchholzi or Enchy-traeus crypticus. After the total test duration of 6 (or 4)?weeks, the juveniles hatched in the meantime are counted. There are several possible extraction techniques, which are always followed by counting the juveniles by hand, but none of them seems easy to handle. We proposed a new modification of the worm extraction method using flotation of fixed and stained juveniles followed by taking a photograph. The digital image of the juveniles is evaluated by computer processing. It makes the counting of juveniles much easier and less labor intensive.     

Economic impacts of soil fertility degradation by traces of iron from drinking water treatment

Environment, Development and Sustainability - The most common drinking water clarification technology worldwide is based on precipitation using the floccules of iron(III) oxide-hydroxide FeO(OH)....     

拉普拉塔河流域以及巴塔哥尼亚地区及相关海域水生态栖息地的改变

本文描述了南美大陆南部陆地和东南沿海地区环境特性及水生栖息地和群落的现状(GIWA巴塔哥尼亚大陆架亚区),结果来自一项GIWA项目框架任务所完成的一份全面评估,绝大部分依据的是公开发表的数据.分析主要集中在跨边界水资源目前的情况和人类活动带来的影响.内陆水体的栖息地和群落变化主要是由为发电和其他用途而建的水坝和水库引起的.从活水环境到净水环境影响了生境,造成了生物群落的改变.在拉普拉塔(La Plata)河流域,外来入侵物种使本地物种消失.过度捕捞和污染影响了生物多样性,造成了海洋栖息地质量下降.本篇文章讨论了相关的原因,讨论了布宜诺斯艾利斯省和渔业资源由两国共享的阿根廷-乌拉圭公共渔业区对沿海生态环境的政策选择.