Hexabromocyclododecane: current understanding of chemistry, environmental fate and toxicology and implications for global management

Hexabromocyclododecane (HBCD) is a globally produced brominated flame retardant (BFR) used primarily as an additive FR in polystyrene and textile products and has been the subject of intensified research, monitoring and regulatory interest over the past decade. HBCD is currently being evaluated under the Stockholm Convention on Persistent Organic Pollutants. HBCD is hydrophobic (i.e., has low water solubility) and thus partitions to organic phases in the aquatic environment (e.g., lipids, suspended solids). It is ubiquitous in the global environment with monitoring data generally exhibiting the expected relationship between proximity to known sources and levels; however, temporal trends are not consistent. Estimated degradation half-lives, together with data in abiotic compartments and long-range transport potential indicate HBCD may be sufficiently persistent and distributed to be of global concern. The detection of HBCD in biota in the Arctic and in source regions and available bioaccumulation data also support the case for regulatory scrutiny. Toxicity testing has detected reproductive, developmental and behavioral effects in animals where exposures are sufficient. Recent toxicological advances include a better mechanistic understanding of how HBCD can interfere with the hypothalamic-pituitary-thyroid axis, affect normal development, and impact the central nervous system; however, levels in biota in remote locations are below known effects thresholds. For many regulatory criteria, there are substantial uncertainties that reduce confidence in evaluations and thereby confound management decision-making based on currently available information.     

Selenium speciation in kerogen from two Chinese selenium deposits: environmental implications

Selenium is an essential trace element for humans, animals, and vegetation. Its occurrence in the environment is characterized by specific chemical and biochemical properties that control its elemental solubility, toxicity, and environmental behavior. The Laerma Se-Au deposit and Yutangba Se deposit are two important Se-bearing deposits found recently in China. In one of these areas (Yutangba), a serious environmental impact happened involving Se poisoning. Previous studies have shown that Se in both deposits is closely related to organic matter, especially kerogen fractions, but detailed relationships between Se and kerogen and Se chemical forms were not reported. In this study, the different speciation of Se is identified by transmission electron microscopy (TEM) and other geochemical techniques (infrared spectra (IS) and X-ray diffraction (XRD)) from kerogen samples extracted from ore rocks of both deposits. The occurrence of organically bound Se in the Laerma deposit and elemental Se nanograins in the Yutangba deposit is observed, indicating the diversity of formation mechanisms and possible chemical forms of Se in Se-rich rocks. The formation of elemental Se associated with organic matter is likely related to redox conditions, whereas organic species are related to the higher sulfur content of kerogen and possibly result from S-Se substitutions. This discovery provides new evidence with which to assess potential Se mobility during weathering of ore-bearing rocks. In an altered rock, the elemental Se in kerogen is more steadily mobilized and is potentially accumulated by vegetation, which may explain the sudden prevalence of Se poisoning in the Yutangba area. In contrast, organically bound Se seems more resistant to chemical alteration compared to other Se species so that its bioavailability may be very restricted.     

Increasing water productivity on Vertisols: implications for environmental sustainability

BACKGROUND: The availability and quality of irrigation water have become a serious concern because of global climate change and an increased competition for water by industry, domestic users and the environment. Therefore, exploring environmentally friendly water‐saving irrigation strategies is essential for achieving food and environmental security. In northern Ethiopia, where traditional furrow irrigation is widely practiced, water mismanagement and its undesirable environmental impact are rampant. A 2‐year field study was undertaken to compare the traditional irrigation management with surge and deficit irrigation practices on a Vertisol plot. RESULT: Results have shown that surge and deficit irrigation practices increase water productivity by 62% and 58%, respectively, when compared to traditional management. The study also found out that these practices reduce the adverse environmental impacts (waterlogging and salinity) of traditional management by minimizing deep percolation and tail water losses. Total irrigation depth was reduced by 12% (for surge) and 27% (for deficit) when compared to traditional management. CONCLUSION: Based on the results, the study concluded that surge and deficit irrigation technologies not only improve water productivity but also enhance environmental sustainability. Copyright © 2010 Society of Chemical Industry     

A review of nitrite and chloride chemistry: Interactions and implications for cured meats

Concerns for the health-related implications of sodium nitrite and sodium chloride in cured meats have lead to reductions in use of both ingredients and there is evidence of chemical interaction between nitrite and chloride in food systems which have implications for cured meats. This review considers the role of chloride in nitrite chemistry and extends this consideration to evaluation of potential changes in cured meat products. Microbiological control depends on nitrite reactivity and a chloride effect has been demonstrated in Clostridium botulinum spore outgrowth and toxin formation. Changes in flavour of cured meats or in development of cured colour are of lesser concern but may take place. More information on specific inhibitory mechanisms by nitrite is needed.     

环评中环境现状监测存在问题与应对策略探究

环境现状监测在建设项目环评中发挥着十分关键的作用,监测结果关乎项目整体效益。基于此,本文首先阐述了环境保护的重要意义,分析了环评中环境现状监测存在的问题,研究了环评中环境现状监测可以采取的相关措施,以期能够对环评中环境现状监测工作的开展起到一定借鉴意义。     

规划环境影响评价在环境保护工作中的重要性

随着经济的发展,各种工业活动和人类活动给自然环境造成了极大地破坏.人类行为是生态环境变化非常关键的影响因素,为了保护生态环境,促进环境保护工作的可持续发展,我国对环境保护事业高度重视,对环境保护的投入持续增加.本文分析了规划环境影响评价在环境保护工作中的重要性,期望能够提升从事环保行业人员的工作效率,减少污染物的产出和...     

Evaluating uncertainty in environmental life-cycle assessment. A case study comparing two insulation options for a Dutch one-family dwelling

The evaluation of uncertainty is relatively new in environmental life-cycle assessment (LCA). It provides useful information to assess the reliability of LCA-based decisions and to guide future research toward reducing uncertainty. Most uncertainty studies in LCA quantify only one type of uncertainty, i.e., uncertainty due to input data (parameter uncertainty). However, LCA outcomes can also be uncertain due to normative choices (scenario uncertainty) and the mathematical models involved (model uncertainty). The present paper outlines a new methodology that quantifies parameter, scenario, and model uncertainty simultaneously in environmental life-cycle assessment. The procedure is illustrated in a case study that compares two insulation options for a Dutch one-family dwelling. Parameter uncertainty was quantified by means of Monte Carlo simulation. Scenario and model uncertainty were quantified by resampling different decision scenarios and model formulations, respectively. Although scenario and model uncertainty were not quantified comprehensively, the results indicate that both types of uncertainty influence the case study outcomes. This stresses the importance of quantifying parameter, scenario, and model uncertainty simultaneously. The two insulation options studied were found to have significantly different impact scores for global warming, stratospheric ozone depletion, and eutrophication. The thickest insulation option has the lowest impact on global warming and eutrophication, and the highest impact on stratospheric ozone depletion.     

环境监测在环境影响评价中的重要性分析

环境问题是当今社会发展中人们最为关心的一个话题,良好的环境质量是确保人类生存和发展的前提条件.为了适应我国可持续发展的战略,应通过环境监测,对环境的相关指标进行观察、测定、分析,以此提高环境保护力度,从而为人们的生活提供安全、健康、舒适的环境.     

Uncertainty in octanol-water partition coefficient: implications for risk assessment and remedial costs

The assessment of human health and ecological risks at chemically contaminated sites often includesthe use of models to assess chemical transport, fate, and exposure/toxicity. These models require input data on a variety of physical and chemical properties for each compound of concern. Small changes in some of these parameters may result in significant differences in estimated human health or ecological risks and in the extent of required remediation efforts. The octanol-water partition coefficient (Kow) for hydrophobic organic compounds is one such parameter, particularly because it is often used to estimate additional partitioning and bioaccumulation parameters. Unfortunately, there is considerable variability among tabulated Kow values for many compounds of concern. This paper assesses the implications of using various values of Kow to calculate health-protective polychlorinated biphenyl (PCB) sediment quality objectives (SQOs) in a case study using a simplified food chain model and the range of Kow values available from or recommended by the U. S. EPA. For the site and Kow values considered in this study, which are a snapshot of values available in the spring of 2004, the SQOs differ by as much as a factor of 5. This range of SQOs is estimated to correspond to a difference in remediation costs of $48 million.     

Bioreduction of uranium: environmental implications of a pentavalent intermediate

The release of uranium and other transuranics into the environment, and their subsequent mobility, are subjects of intense public concern. Uranium dominates the inventory of most medium- and low-level radioactive waste sites and under oxic conditions is highly mobile as U(VI), the soluble uranyl dioxocation (UO2)2+. Specialist anaerobic bacteria are, however, able to reduce U(VI)to insoluble U(IV), offering a strategy for the bioremediation of uranium-contaminated groundwater and a potential mechanism for the biodeposition of uranium ores. Despite the environmental importance of U(VI) bioreduction, there is little information on the mechanism of this transformation. In the course of this study we used X-ray absorption spectroscopy (XAS) to show that the subsurface metal-reducing bacterium Geobacter sulfurreducens reduces U(VI) by a one-electron reduction, forming an unstable (UO2)+ species. The final, insoluble U(IV) product could be formed either through further reduction of U(V) or through its disproportionation. When G. sulfurreducens was challenged with the chemically analogous (NpO2)+, which is stable with respect to disproportionation, it was not reduced, suggesting that it is disproportionation of U(V) which leads to the U(IV) product. This surprising discrimination between U and Np illustrates the need for mechanistic understanding and care in devising in situ bioremediation strategies for complex wastes containing other redox-active actinides, including plutonium.     

环境工程中环境影响评价的重要性探讨

进入21世纪后,我国社会飞速发展,经济建设也取得了举世瞩目的成就,人们的生活水平也大幅提高.然而,在经济高速发展的同时,也给环境带来了一定的消极影响.在这样的背景下,环境工程中的环境影响评价工作也得到了前所未有的重视.这项工作能够通过对环境影响因素的分析,为相关部门制定科学的解决对策提供依据,推动我国环保事业的发展.本...     

TRLFS evidence for precipitation of uranyl phosphate on the surface of alumina: environmental implications

We studied the ligand-enhanced sorption of uranyl ions (1-12 μM) on α-alumina colloids suspended in (and pre-equilibrated with) solutions at various concentrations of phosphate ions (P(T) = 0-900 μM). A highly sensitive technique, time resolved laser-induced fluorescence spectroscopy (TRLFS), was used to examine the chemical speciation of uranyl sorbed at trace concentrations (0.4-4 μmol U·g?1). The suspensions with P(T) ≥ 100 μM exhibited high uranyl adsorption, and a very high intensity of fluorescence that increased with the sorbed amounts of phosphate and uranyl. These samples exhibited similar spectral and temporal characteristics of fluorescence emission, evidencing a uniform speciation pattern and a single coordination environment for sorbed U, despite large variation in parameters such as aqueous uranyl speciation, U loading, and extent of coverage of alumina by secondary Al phosphates precipitating on the surface. The results pointed formation of surface precipitates of uranyl phosphates, which are characterized by high quantum yield, peak maxima at positions similar to those of U(VI) phosphate minerals and four lifetimes indicating distortions, in-homogeneities or varying number of water molecules in the lattice. The findings have major implications for our understanding of the mechanisms of immobilization of U at trace levels on surfaces of oxides submitted to phosphated solutions in soils with low pH.     

Five-stage environmental exposure assessment strategy for mixtures: gasoline as a case study

A five-stage strategy is suggested for conducting an exposure assessment of mixtures that may contain numerous chemical components. The stages are: (1) determination of mixture composition and variability, (2) selection of component groups within the mixture and documentation of criteria used for this selection, (3) compilation of relevant property data for each group, (4) assessment of environmental fate of each group, and (5) assessment of environmental and human exposure to each group and to the mixture as a whole. A subsequent step is the assessment of environmental and/or human risk associated with the individual and aggregate exposure to each group. The approach is illustrated by application to gasoline, which is treated as 24 component groups or hydrocarbon blocks. Focusing on stages 2-4, the illustration shows that the groups display widely different environmental fates as a result of their different physicochemical properties, degradation half-lives, and mode-of-entry into the environment. As a result, the relative proportions of groups in each environmental medium (such as air and water) differ greatly from that of the original mixture. It is thus important to treat gasoline and similar mixtures as a number of component groups instead of as a single substance. A generic procedure is suggested in which the model is run for unit emissions of each component group to air, water, and soil. These results are compiled into matrices that can then be conveniently scaled to actual emission rates without rerunning the model. Methods for determining subsequent exposure and risk are also briefly outlined.     

Spatial and temporal trends of POPs in Norwegian and UK background air: implications for global cycling

Data are presented for PCBs and HCB measured by passive air samplers (SPMDs) along a latitudinal transect from the south of the UK to the north of Norway during 1998-2000. This work is part of an ongoing air sampling campaign in which data were previously gathered for 1994-1996. Comparisons of the masses of chemicals sequestered by the SPMDs during these different time intervals are used to investigate spatial and temporal trends. Results are discussed in the context of sources, long-range atmospheric transport, fractionation/cold condensation, and global clearance processes controlling ambient levels of POPs. Spatial trends show a decrease in absolute sequestered amounts of PCBs with increasing latitude i.e., with increasing distance from the source area. However, relative sequestered amounts of the homologue groups (expressed as a ratio to penta-PCB) show a clear latitudinal trend, with the relative contribution of the lighter congeners increasing with increasing latitude, providing evidence of latitudinal fractionation. Absolute amounts of HCB increase with latitude, suggesting this compound is undergoing cold condensation. Sequestered amounts of PCBs generally decreased between the two sampling periods by a factor 2-5 over 4 years, suggesting half-lives on the order of 1.7-4 years. The relative rates of decline (1998-2000 data as a percentage of the 1994-1996 data) were compared for different congeners and latitudes. No clear latitudinal trends were found, with all sites/congeners showing a similar marked decline over time to ca. 30% of the former value. We discuss the interpretation of these observations and conclude they imply that the underlying trends of current ambient levels of PCBs in European background air are still largely controlled by primary emissions, rather than recycling/secondary emissions from the major environmental repositories such as soils or water bodies.     

清洁生产在环境影响评价中的应用

本文重点针对清洁生产在环境影响评价中的应用进行了详细的分析,以供参考.