Characterization of colored products formed during irradiation of aqueous solutions containing H2O2 and phenolic compounds

Irradiation of aqueous (pH = 5) mixtures containing hydrogen peroxide (1 mM) and phenolic compounds (10 mM) were found to produce visible light absorbing solutions over the course of several hours. The kinetics and products of these reactions were studied by UV–VIS absorbance, electrospray mass spectrometry, FTIR, fluorescence, and NMR and compared to humic-like substances commonly found in atmospheric particulate matter. It was determined the reactions leading to formation of color are quite general to this compound class, and the reactions proceeded more rapidly with hydroxyl or methoxy substitution ortho to the phenolic OH. However, para substitution generally slowed formation of colored compounds compared to the unsubstituted form. Mass spectrometry confirms compounds of several hundred Da formed in the reaction mixtures. The IR spectra of the reaction products bear similarity to that observed for authentic aerosol humic-like substances. The results indicate radical coupling of phenols and methoxylated phenols in tropospheric waters may contribute to humic-like particulate matter.     

Intra-laboratory evaluation of Microbial Assay for Risk Assessment (MARA) for potential application in the implementation of the Water Framework Directive (WFD)

The Microbial Assay for Risk Assessment (MARA) is an innovative system based on an array of 11 different microbial species freeze-dried in a 96-well micro-titre plate format. Developed for testing the toxicity of chemicals, mixtures and environmental samples, the assay employs species of a taxonomically diverse range. In addition to ten prokaryotic species, a eukaryote (yeast) is included in the range. The MARA's innate scope of a multi-dimensional test allows determination of toxicity based on a unique assay fingerprint or index, numerically expressed as the mean Microbial Toxic Concentration (MTC). The most significant potential of the test is in the additional inference that can be conveyed to the toxicity evaluation because of the presence of each of the constituent species. In view of the fact that conventional aquatic bioassays, like fish or cladoceran tests, are expensive and impractical, the MARA could provide a cost-effective solution for routine ecotoxicological testing. The performance of the MARA was evaluated to ascertain its capability and potential scope. Sensitivity to toxicants and different environmental samples was assessed. Evaluation included comparison with other tests: namely Microtox, invertebrate (Daphnia magna and Thamnocephalus platyurus) microbiotests, and respiration-inhibition and nitrification-inhibition tests. The most sensitive invertebrate test was found to be the T. platyurus microbiotest for three of the four metals tested. The LC(50) values for this test for Cd(ii), Cr(vi) and As(iii) were 0.2, 0.018 and 0.3 mg l(-1), respectively; and the corresponding most sensitive MARA species MTC values were 4.4, 2.8 and 17 mg l(-1), respectively.     

Impact of electrokinetic remediation on microbial communities within PCP contaminated soil

Electrokinetic techniques have been used to stimulate the removal of organic pollutants within soil, by directing contaminant migration to where remediation may be more easily achieved. The effect of this and other physical remediation techniques on the health of soil microbial communities has been poorly studied and indeed, largely ignored. This study reports the impact on soil microbial communities during the application of an electric field within ex situ laboratory soil microcosms contaminated with pentachlorophenol (PCP; 100mg kg(-1) oven dry soil). Electrokinetics reduced counts of culturable bacteria and fungi, soil microbial respiration and carbon substrate utilisation, especially close to the acidic anode where PCP accumulated (36d), perhaps exacerbated by the greater toxicity of PCP at lower soil pH. There is little doubt that a better awareness of the interactions between soil electrokinetic processes and microbial communities is key to improving the efficacy and sustainability of this remediation strategy.     

Gill morphogenesis in the oyster Ostrea chilensis

Despite the importance of the gills in the acquisition of food by suspension-feeding bivalve mollusks, there is almost no information on gill organogenesis. By means of a series of stereoscan electron micrographs, this paper describes gill development in the Chilean oyster, Ostrea chilensis, from the brooded larval stages to 1-month-old spat. A single gill rudiment was observed on each side of the mantle at a shell length of 320 μm, and the rudiments increased in number and size until the end of the brooding period. During metamorphosis the gill filaments increased in number from 5 or 6 to between 7 and 9. The loss of the velum and the absence of functional gill filaments during metamorphosis are consistent with previous observations of weight loss during this critical period of the life history, because the newly settled juvenile lacks the ability to remove particles from suspension. The end of metamorphosis (100% of spat with dissoconch edge) was reached 36 h after larval settlement, when the gill filaments began to grow cilia, which increased in density and differentiated as the spat developed and acquired the capability of suspension-feeding, accounting for the increase in body weight previously recorded during this stage. The larval rudiments gave rise to the inner demibranchs. The outer demibranchs were observed 10 days after settlement, located between the inner demibranch and the mantle. In 1-month-old spat, the gill did not show differentiation between primary and secondary filaments, indicating that the heterorhabdic condition characteristic of adult oysters had yet to be attained. Received: 11 December 1998 / Accepted: 21 August 2000     

The European Water Framework Directive beyond 2010: let actions speak louder than words

The first generation of WFD River Basin Management Plans is now available. This is a formidable achievement and a great step towards addressing Europe's deteriorated river systems. However, plans are only words: only the actual implementation of the selected measures will result in achievement of good ecological and chemical status. The WFD Lille 2010 Conference pointed out that a lot of new, but so far unused scientific knowledge is available to improve the effectiveness of selected measures or to inspire the introduction of complementary measures. Furthermore, the complexity in terms of the functioning of the water system, its interaction with the socio-economic system and the uncertain consequences of climate change, urges a 'learning-by-doing' approach. This approach should be applied in well-designed, -coordinated and -monitored learning catchments.     

Exploring Environmental and Economic Trade-offs Associated with Aggregate Recycling from Decommissioned Forest Roads

Forest road decommissioning is a pro-active mechanism for preventing future habitat degradation and for increasing the likelihood of endangered salmonid survival in the western U.S. High implementation costs however preclude many desirable projects from being undertaken, especially on federally owned land. Previous research and real-world applications have demonstrated the cost savings potential of reusing aggregate recovered from forest roads during decommissioning. These cost savings can effectively subsidize decommissioning projects, suggesting an economic benefit associated with improving environmental benefit. We present a mixed integer, multiple objective formulation to identify the efficient trade-off surface between conflicting economic and environmental criteria, where environmental benefit is defined as the hazard weighted length of roads decommissioned. We compare nondominated frontiers identified with and without the opportunity to recycle aggregate. Our results suggest that aggregate recycling promotes a synergistic relationship between cost savings (subsidy) and environmental performance, where subsidies generally increase with increasing environmental performance. Effective subsidy values can reach 31% of total expenditure, at the maximum level of environmental benefit. Transportation managers are therefore able to recover and reuse a nonrenewable resource, while at the same time promoting economic and environmental efficiency.     

Modeling to Evaluate Contribution of Oil and Gas Emissions to Air Pollution

Oil and gas production in the Western United States has increased considerably over the past 10 years. While many of the still limited oil and gas impact assessments have focused on potential human health impacts, the typically remote locations of production in the Intermountain West suggests that the impacts of oil and gas production on national parks and wilderness areas (Class I and II areas) could also be important. To evaluate this, we utilize the Comprehensive Air quality Model with Extensions (CAMx) with a year-long modeling episode representing the best available representation of 2011 meteorology and emissions for the Western United States. The model inputs for the 2011 episodes were generated as part of the Three State Air Quality Study (3SAQS). The study includes a detailed assessment of oil and gas (O&G) emissions in Western States. The year-long modeling episode was run both with and without emissions from O&G production. The difference between these two runs provides an estimate of the contribution of the O&G production to air quality. These data were used to assess the contribution of O&G to the 8 hour average ozone concentrations, daily and annual fine particulate concentrations, annual nitrogen deposition totals and visibility in the modeling domain. We present the results for the Class I and II areas in the Western United States. Modeling results suggest that emissions from O&G activity are having a negative impact on air quality and ecosystem health in our National Parks and Class I areas.

Implications: In this research, we use a modeling framework developed for oil and gas evaluation in the western United States to determine the modeled impacts of emissions associated with oil and gas production on air pollution metrics. We show that oil and gas production may have a significant negative impact on air quality and ecosystem health in some national parks and other Class I areas in the western United States. Our findings are of particular interest to federal land managers as well as regulators in states heavy in oil and gas production as they consider control strategies to reduce the impact of development.     

Case studies in co-benefits approaches to climate change mitigation and adaptation

Attempts to mitigate greenhouse gas emissions or manage the effects of climate change traditionally focus on management or policy options that promote single outcomes (e.g., either benefiting ecosystems or human health and well-being). In contrast, co-benefits approaches to climate change mitigation and adaptation address climate change impacts on human and ecological health in tandem and on a variety of spatial and temporal scales. The article engages the concept of co-benefits through four case studies. The case studies emphasize co-benefits approaches that are accessible and tractable in countries with human populations that are particularly vulnerable to climate change impacts. They illustrate the potential of co-benefits approaches and provide a platform for further discussion of several interdependent principles relevant to the implementation of co-benefits strategies. These principles include providing incentives across multiple scales and time frames, promoting long-term integrated impact assessment, and fostering multidimensional communication networks.     

Hexavalent chromium reduction kinetics in rodent stomach contents

Reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in the stomach prior to absorption is a well-recognized detoxification process thought to limit the toxicity of ingested Cr(VI). However, administration of high concentrations of Cr(VI) in drinking water cause mouse small intestinal tumors, and quantitative measures of Cr(VI) reduction rate and capacity for rodent stomach contents are needed for interspecies extrapolation using physiologically-based toxicokinetic (PBTK) models. Ex vivo studies using stomach contents of rats and mice were conducted to quantify Cr(VI) reduction rate and capacity for loading rates (1-400 mg Cr(VI) L⁻¹ stomach contents) in the range of recent bioassays. Cr(VI) reduction was measured with speciated isotope dilution mass spectrometry to quantify dynamic Cr(VI) and Cr(III) concentrations in stomach contents at select time points over 1 h. Cr(VI) reduction followed mixed second-order kinetics, dependent upon concentrations of both Cr(VI) and the native reducing agents. Approximately 16 mg Cr(VI)-equivalents of reducing capacity per L of fed stomach contents (containing gastric secretions, saliva, water and food) was found for both species. The second-order rate constants were 0.2 and 0.3 L mg⁻¹ h⁻¹ for mice and rats, respectively. These findings support that, at the doses that caused cancer in the mouse small intestine (?20 mg Cr(VI) L⁻¹ in drinking water), the reducing capacity of stomach contents was likely exceeded. Thus, for extrapolation of target tissue dose in risk assessment, PBTK models are necessary to account for competing kinetic rates including second order capacity-limited reduction of Cr(VI) to Cr(III).