Unexplained gonad alterations in whitefish (Coregonus spp.) from Lake Thun, Switzerland: levels of persistent organic pollutants in different morphs

Since 2000, a surprisingly high number of macroscopical gonad alterations has been reported in whitefish (Coregonus spp.) from Lake Thun, Switzerland. This unique phenomenon is still unexplained and has received much public attention. As one possible trigger for these effects, the presence of persistent, bioaccumulative and toxic compounds acting as endocrine disruptors in the lake has been discussed. In this study, concentrations of selected persistent organic pollutants were examined in two morphs of whitefish from Lake Thun and their link to the observed abnormalities was investigated. Analyzed compound classes included polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated naphthalenes, polybrominated diphenyl ethers and hexabromocyclododecanes. The target substances were identified in all samples and concentrations of the analyzed compounds were highly correlated among each other. These correlations show that the analyzed substances have the same distribution pattern throughout the lake and that uptake, accumulation and elimination processes are similar. Significant differences in contaminant levels within the samples existed between the two analyzed morphs of whitefish, most likely due to different age, food patterns and growth rate. No difference in contaminant levels was observed between fish with abnormal gonads and fish with normal gonads, suggesting no causal link between the investigated lipophilic organohalogen compounds present in fish and the observed gonad abnormalities in whitefish from Lake Thun. A comparison to existing data shows that concentrations in Lake Thun whitefish are at the lower bound of contaminant levels in whitefish from Swiss lakes or from European waters.     

Remediation of a chlorinated aromatic hydrocarbon in water by photoelectrocatalysis

Photoelectrocatalysis driven by visible light offers a new and potentially powerful technology for the remediation of water contaminated by organo-xenobiotics. In this study, the performance of a visible light-driven photoelectrocatalytic (PEC) batch reactor, applying a tungsten trioxide (WO₃) photoelectrode, to degrade the model pollutant 2,4-dichlorophenol (2,4-DCP) was monitored both by toxicological assessment (biosensing) and chemical analysis. The bacterial biosensor used to assess the presence of toxicity of the parent molecule and its breakdown products was a multicopy plasmid lux-marked E. coli HB101 pUCD607. The bacterial biosensor traced the removal of 2,4-DCP, and in some case, its toxicity response suggests the identification of transient toxic intermediates. The loss of the parent molecule, 2,4-DCP determined by HPLC, corresponded to the recorded photocurrents. Photoelectrocatalysis offers considerable potential for the remediation of chlorinated hydrocarbons, and that the biosensor based toxicity results identified likely compatibility of this technology with conventional, biological wastewater treatment.     

Mercury cycling and species mass balances in four North American lakes

A mass balance model for mercury based on the fugacity concept is applied to Lake Superior, Lake Michigan, Onondaga Lake and Little Rock Lake to evaluate model performance, analyze cycling of three mercury species groups (elemental, divalent and methyl mercury), and identify important processes that determine the source-to-concentration relationship of the three mercury species groups in these lakes. This model application to four disparate ecosystems is an extension of previous applications of fugacity-based models describing mercury cycling. The model performs satisfactorily following site-specific parameterization, and provides an estimate of minimum rates of species interconversion that compare well with literature. Volatilization and sediment burial are the main processes removing mercury from the lakes, and uncertainty analyses indicate that air-water exchange of elemental mercury and water-sediment exchange of divalent mercury attached to particles are influential in governing mercury concentrations in water. Any new model application or field campaign to quantify mercury cycling in a lake should consider these processes as important.     

Integrative approach to delineate natural attenuation of chlorinated benzenes in anoxic aquifers

Biodegradation of chlorobenzenes was assessed at an anoxic aquifer by combining hydrogeochemistry and stable isotope analyses. In situ microcosm analysis evidenced microbial assimilation of chlorobenzene (MCB) derived carbon and laboratory investigations asserted mineralization of MCB at low rates. Sequential dehalogenation of chlorinated benzenes may affect the isotope signature of single chlorobenzene species due to simultaneous depletion and enrichment of ¹³C, which complicates the evaluation of degradation. Therefore, the compound-specific isotope analysis was interpreted based on an isotope balance. The enrichment of the cumulative isotope composition of all chlorobenzenes indicated in situ biodegradation. Additionally, the relationship between hydrogeochemistry and degradation activity was investigated by principal component analysis underlining variable hydrogeochemical conditions associated with degradation activity at the plume scale. Although the complexity of the field site did not allow straightforward assessment of natural attenuation processes, the application of an integrative approach appeared relevant to characterize the in situ biodegradation potential.     

Conservation, commercialisation and confusion: harvesting of Ischyrolepis in a coastal forest, South Africa

Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition. Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade, the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than 20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to both conservation and livelihoods. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Cold start extra emissions as a function of engine stop time: Evolution over the last 10 years

Cars with catalysts show a significant increase in exhaust emissions at engine start. These extra emissions are expressed as the difference, over a particular driving cycle, between emissions generated when the vehicle is started and when the engine or the catalyst are stably warm. Experimental data, suitable for the assessment of cold start emissions, are usually available for completely cooled engines. Most results originate from tests at ambient temperature of 20–30 °C and with an engine stop time of at least 12 h. On the other hand, data including shorter stop times are very rare.The present work investigates the influence of exhaust emissions with shorter stop times, i.e. 0.5, 1, 2 and 4 h. The main goal consists in the comparison of emissions exhausted by recent car models (Euro-4) against emissions assessed in the framework of a similar campaign 10 years ago (FAV1/Euro-1 vehicles).A short survey of the current extra emission estimation methods is presented in this paper. It is shown that some methods are not suited for providing correct estimations in all cases. We discuss the fact that different estimation methods can show either similar or completely different results depending on the evolution behaviour of the hot emissions.Due to new technologies, e.g. the catalyst and improved engine control algorithms, emissions have been considerably reduced over the last 10 years. In this study it is determined how the relative extra emissions, i.e. extra emissions relative to the extra emissions for the standard stop time of 12 h, expressed as a function of stop time have changed. We may claim with caution that for medium stop times of 0.5–4 h the average relative extra emissions of Euro-4 vehicles are well below the average of the relative extra emissions of Euro-1 vehicles.     

Source identification of personal exposure to fine particulate matter using organic tracers

Personal exposure to fine particulate matter (PM2.5) is due to both indoor and outdoor sources. Contributions of sources to personal exposure can be quite different from those observed at ambient sampling locations. The primary goal of this study was to investigate the effectiveness of using trace organic speciation data to help identify sources influencing PM2.5 exposure concentrations. Sixty-four 24-h PM2.5 samples were obtained on seven different subjects in and around Boulder, CO. The exposure samples were analyzed for PM2.5 mass, elemental and organic carbon, organic tracer compounds, water-soluble metals, ammonia, and nitrate. This study is the first to measure a broad distribution of organic tracer compounds in PM2.5 personal samples. PM2.5 mass exposure concentrations averaged 8.4 μg m^?3. Organic carbon was the dominant constituent of the PM2.5 mass. Forty-four organic species and 19 water-soluble metals were quantifiable in more than half of the samples. Fifty-four organic species and 16 water-soluble metals had measurement signal-to-noise ratios larger than two after blank subtraction.The dataset was analyzed by Principal Component Analysis (PCA) to determine the factors that account for the greatest variance. Eight significant factors were identified; each factor was matched to its likely source based primarily on the marker species that loaded the factor. The results were consistent with the expectation that multiple marker species for the same source loaded the same factor. Meat cooking was an important source of variability. The factor that represents meat cooking was highly correlated with organic carbon concentrations (r = 0.84). The correlation between ambient PM2.5 and PM2.5 exposure was relatively weak (r = 0.15). Time participants spent performing various activities was generally not well correlated with PCA factor scores, likely because activity duration does not measure emissions intensity. The PCA results demonstrate that organic tracers can aid in identifying factors that influence personal exposures to PM2.5.     

Improving the Integration of Recreation Management with Management of Other Natural Resources by Applying Concepts of Scale from Ecology

In this article, we examine how issues of scale affect the integration of recreation management with the management of other natural resources on public lands. We present two theories used to address scale issues in ecology and explore how they can improve the two most widely applied recreation-planning frameworks. The theory of patch dynamics and hierarchy theory are applied to the recreation opportunity spectrum (ROS) and the limits of acceptable change (LAC) recreation-planning frameworks. These frameworks have been widely adopted internationally, and improving their ability to integrate with other aspects of natural resource management has significant social and conservation implications. We propose that incorporating ecologic criteria and scale concepts into these recreation-planning frameworks will improve the foundation for integrated land management by resolving issues of incongruent boundaries, mismatched scales, and multiple-scale analysis. Specifically, we argue that whereas the spatially explicit process of the ROS facilitates integrated decision making, its lack of ecologic criteria, broad extent, and large patch size decrease its usefulness for integration at finer scales. The LAC provides explicit considerations for weighing competing values, but measurement of recreation disturbances within an LAC analysis is often done at too fine a grain and at too narrow an extent for integration with other recreation and resource concerns. We suggest that planners should perform analysis at multiple scales when making management decisions that involve trade-offs among competing values. The United States Forest Service is used as an example to discuss how resource-management agencies can improve this integration.     

Linking Theory and Practice for Restoration of Step-Pool Streams

Step-pools sequences are increasingly used to restore stream channels. This increase corresponds to significant advances in theory for step-pools in recent years. The need for step-pools in stream restoration arises as urban development encroaches into steep terrain in response to population pressures, as stream channels in lower-gradient areas require stabilization due to hydrological alterations associated with land-use changes, and as step-pools are recognized for their potential to enhance stream habitats. Despite an increasingly voluminous literature and great demand for restoration using step-pool sequences, however, the link between theory and practice is limited. In this article, we present four unique cases of stream restoration using step-pools, including the evolution of the approaches, the project designs, and adjustments in the system following restoration. Baxter Creek in El Cerrito, California demonstrates an early application of artificial step-pools in which natural adjustments occurred toward geomorphic stability and ecological improvement. Restoration of East Alamo Creek in a large residential development near San Ramon, California illustrates an example of step-pools increasingly used in locations where such a channel form would not naturally occur. Construction of a step-pool channel in Karnowsky Creek within the Siuslaw National Forest, Oregon overcame constraints posed by access and the type and availability of materials; the placement of logs allowed natural scouring below steps. Dry Canyon Creek on the property of the Mountains Restoration Trust in Calabasas, California afforded a somewhat experimental approach to designing step-pools, allowing observation and learning in the future. These cases demonstrate how theories and relationships developed for step-pool sequences over the past two decades have been applied in real-world settings. The lessons from these examples enable us to develop considerations useful for deriving an appropriate course of design, approval, and construction of artificial step-pool systems. They also raise additional fundamental questions concerning appropriate strategies for restoration of step-pool streams. Outstanding challenges are highlighted as opportunities for continuing theoretical work.     

Why the Far-Distant Future Should Be Discounted at Its Lowest Possible Rate

A critical feature of the distant future is currently unresolvable uncertainty about what will then be the appropriate rate of return on capital to use for discounting. This paper shows that there is a well-defined sense in which the “lowest possible” interest rate should be used for discounting the far-distant future part of any investment project. Some implications are discussed for evaluating long-term environmental projects or activities, like measures to mitigate the possible effects of global climate change.