Monitoring mercury in fish in a stream system receiving multiple industrial inputs

Sunfish and a minnow species were used as indicators of anthropogenic mercury contamination in an east Tennessee stream system receiving multiple point and non-point discharges. The monitoring of bluegill (Lepomis macrochirus) and redbreast sunfish (Lepomis auritus) identified bioavailable mercury near three geographically separate industrial facilities, and was able to detect decreases in contamination with distance away from these facilities. In general, total mercury concentrations in the tissue of sunfish in this study were low in comparison to the most commonly cited human health threshold limits, although concentrations at some sites exceeded 1 g/g. Caged blacknose dace (Rhinichthys atratulus) were monitored in conjunction with resident fish as an indicator of more discrete sources in selected headwater streams where fish movement was deemed a potential factor affecting mercury body burdens. Mercury concentrations in muscle tissue of caged dace after 12 weeks exposure were generally low (<0.2 g/g) at all sites but higher than in fish from reference streams. mercury accumulation varied between species (sunfish vs. dace) and monitoring method (caged vs. resident) at the same site, with sunfish tending to accumulate higher concentrations of mercury than resident dace which, in turn, contained about twofold higher concentrations than caged dace. However, the site-to-site pattern of mercury accumulation was similar. This study demonstrates the utility of using small stream dwelling fish with restricted home ranges as a tool for identifying and evaluating the bioavailability of mercury sources in large industrial or urbanized settings.     

Phase-in of nonpoint sources in a transferable discharge permit system for water quality management: setting permit prices

The composite market design is a proposal for a transferable discharge permit system that specifically includes agricultural non-point-source dischargers and addresses both property rights and transaction cost problems. The first step to implementation of a composite market scheme is the estimation of a supply curve for abatement measures in the catchment area. Estimation is performed by combining costs with modeled loss reductions from selected best management practices and then using this information to estimate the supply curve for abatement, which in turn can then be used to set permit prices. The R?nne? catchment in southern Sweden is used as a pilot study area for making this type of estimate. Costs for existing measures that reduce nutrient losses from farmland (catch crops and spring planting) are based on existing programs financed by the Swedish Agricultural Board. A set of supply curves is calculated for these measures using retention estimates for seven subcatchments and three soil types in the area. Although existing information is sufficient to calculate partial supply curves and may be used to set permit prices, additional measures should be included as well as an increased number of variables for differentiating site specific reduction costs.     

Risk communication in emergency response to a simulated extreme flood

Risk communication in flood incident management can be improved through developing hydrometeorological and engineering models used as tools for communicating risk between scientists and emergency management professionals. A range of such models and tools was evaluated by participating flood emergency managers during a 4-day, real-time simulation of an extreme event in the Thamesmead area in the Thames estuary close to London, England. Emergency managers have different communication needs and value new tools differently, but the indications are that a range of new tools could be beneficial in flood incident management. Provided they are communicated large model uncertainties are not necessarily unwelcome among flood emergency managers. Even so they are cautious about sharing the ownership of weather and flood modelling uncertainties.     

Control strategies for particulate emissions from vehicular diesel exhaust

The advantages and disadvantages of several possible control strategies for particulate emissions from vehicular diesel exhaust are discussed. The evaluation of the potential usefulness of the various control strategies is based on available data concerning the mass loading and particle size distribution and on anticipated control standards. Several studies have been made on devices for removing particulate emissions from vehicular diesel exhaust. These studies, which include the techniques of filtration, wet scrubbers, and electrostatic precipitation, are summarized. A comparison of the various control devices is made based on such factors as size, efficiency, and maintenance requirements.     

Soil washing: Practical considerations and pitfalls

The use of soil washing to remove petroleum hydrocarbon contamination from the soil matrix is becoming more widely used. When viewed as a volume reduction tool, this technology shows some promise. However, ongoing research and treatability studies indicate that without further treatment, even larger-sized soil fractions (sands and cobbles) may retain hydrocarbon contamination at levels that require further cleaning prior to permanent disposal or reuse. The perception has been that by removing the sand from the soil matrix, thus achieving a 30 percent to 60 percent volume reduction, expensive post-washing treatment or approved disposal of the finer materials (silts and clays) would be cost-effective. There exists evidence to the contrary, however. Hydrocarbon retention after soil washing may be influenced by a number of factors unrelated to particle size. Soil characteristics that may play a role include soil humic acids, metal oxide coatings, geologic origin of the soil particles, and clay type. In this article the authors describe a laboratory study designed to evaluate the “cleanability” of two soils.     

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m³ FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NO_x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO_x and simplified ambient surrogate–NO_x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO_x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO_x levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.     

Influence of sulfide (S2-) on preservation and speciation of inorganic arsenic in drinking water

Generally, H2SO4, HNO3, HCl or the combination of ethylenediaminetetraacetate with acetic acid (EDTA-HAc) have been used to preserve arsenite and arsenate species prior to analysis. When these acidic preservatives are added in sulfidic water, instantaneous precipitation of poorly crystalline orpiment, As2S3(am), occurs, thereby lowering the total arsenic, As(Tot), analysis. A new method for the determination of As(Tot) was developed in which acid-preserved sulfidic water samples were oxidized with NaOCl, converting As2S3(am) and thioarsenic species to arsenate. A new method was also developed for the separation of uncharged arsenite and charged thioarsenic species in fresh, unpreserved sulfidic water by adsorbing the charged thioarsenic species while allowing uncharged arsenite to pass through a strong-base resin unhindered. The adsorbed thioarsenic species could be eluted efficiently with 0.16 M NaOCl solution.     

DESIGN CONSIDERATIONS FOR AMBIENT STREAM QUALITY MONITORING1

ABSTRACT: Existing ambient water quality monitoring programs have resulted in data which are often unsuitable for assessment of water quality trends. A primary concern in designing a stream quality monitoring network is the selection of a temporal sampling strategy. It is extremely important that data for trend assessment be collected uniformly in time. Greatly superior trend detection power results for such a strategy as compared to stratified sampling strategies. In general, it is desirable that sampling frequencies be at least monthly but not greater than biweekly; higher sampling frequencies usually result in little additional information. An upper limit on trend detectability exists such that for both five and ten year base periods it is often impossible to detect trends in time series where the ratio of the trend magnitude to time series standard deviation is less than about 0.5. For the same record lengths trends in records with trend to standard deviation ratios greater than about one can usually be detected with very high power when a uniform sampling strategy is followed.     

Predictability of clinical assessments for driving performance

PROBLEM: As the number of older drivers grows, it is increasingly important to accurately identify at-risk drivers. This study tested clinical assessments predictive of real-time driving performance. METHOD: Selected assessment tools considered important in the identification of at-risk older drivers represented the domains of vision, cognition, motor performance, and driving knowledge. Participants were administered the battery of assessments followed by an on-road test. A univariate analysis was conducted to identify significant factors (<.05) to be included in a multivariate regression model. RESULTS: Assessments identified as independently associated with driving performance in the regression model included: FACTTM Contrast sensitivity slide-B, Rapid Pace Walk, UFOV rating, and MMSE total score. DISCUSSION: The domains of vision, cognitive, and motor performance were represented in the predictive model. SUMMARY: Due to the dynamic nature of the driving task, it is not likely that a single assessment tool will identify at risk drivers. IMPACT ON INDUSTRY: By standardizing the selection of clinical assessments used in driving evaluations, practitioners should be able to provide services more efficiently, more objectively, and more accurately to identify at-risk drivers.