A small subsurface ion mobility spectrometer sensor for detecting environmental soil-gas contaminants

A small subsurface ion mobility spectrometer (SS-IMS) was constructed and tested with several environmental contaminants to determine its potential for monitoring gaseous volatile organic compounds in the vadose zone. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were detected and separated in IMS for the first time. Detection limits as low as 1 part per billion volume-to-volume (ppb(v)) were observed. Reduced mobility (K(0)) values were reported for 11 environmental contaminants. These data demonstrated the potential of ion mobility spectrometry as a viable technology for detecting and separating environmental soil-gas contaminants in the field, which may lead to a practical and simple approach for long-term monitoring of contaminated soils.     

Ökotoxikologie am Beispiel der Rheinverschmutzung durch den Chemie-Unf all bei Sandoz in Basel

A fire at a chemical manufacturing plant at Schweizerhalle (near Basel) in November 1986 and the subsequent release of toxic agrochemicals into the Rhine river is taken as a basis to discuss some problems and needs in ecotoxicological research. Especially serious is the lack of knowledge about chronic effects of mixtures of chemicals to individuals and whole ecosystems. There is an urgent need for generally applicable principles and concepts. A discussion of the relationship between toxic effects to fish, exposure time, and concentration provides some hints about the direction towards which research should proceed. Finally, eight theses pertaining to ecotoxicology summarize what can be learned from the analysis of a chemical spill.     

Implications of non-equilibrium transport in heterogeneous reactive barrier systems: evidence from laboratory denitrification experiments

Organic substrates in reactive barrier systems are often heterogeneous material mixtures with relatively large contrasts in hydraulic conductivity and porosity over short distances. These short-range variations in material properties imply that preferential flow paths and diffusion between regions of higher and lower hydraulic conductivity may be important for treatment efficiency. This paper presents the results of a laboratory column experiment where denitrification is investigated using a heterogeneous reactive substrate (sawdust mixed with sewage sludge). Displacement experiments with a non-reactive solute at three different flow rates are used to estimate transport parameters using a dual porosity non-equilibrium model. Parameter estimation from breakthrough curves produced relatively consistent values for the fraction of the porosity consisting of mobile water (β) and the mass transfer coefficient (α), with average values of 0.27 and 0.42 d(-1), respectively. The column system removes >95% of the influent nitrate at low and medium flow, but only 50-75% of the influent nitrate at high flow, suggesting that denitrification kinetics and diffusive mass transfer rates are limiting the degree of treatment at lower hydraulic residence times. Reactive barrier systems containing dual porosity media must therefore consider mass transfer times in their design; this is often most easily accommodated by adjusting flowpath length.     

TOWARD A BETTER UNDERSTANDING OF RECREATIONAL BOATING IN THE ADIRONDACK LAKES REGION1

ABSTRACT: Results of a study to determine the relationship between physical characteristics of Adirondack lakes and variations in peak boat-use intensity indicated that 69 percent of the variation in peak use can be accounted for by the number of public and commercial boat-launching facilities per mile of lake shoreline. Other lake characteristics related to peak boat use were: the number of commercial overnight accommodations available, number of boat slips, lake size, and miles of lake shoreline. Lake characteristics not related to peak use were: accessibility, configuration, tent spaces available, surrounding landscape quality, volume of traffic and availability of other lakes. This information should provide recreation managers and planners with a better understanding of factors related to variation in peak boating-use periods.     

Molecular-level investigation of monoaromatic compound sorption to suspended soil particles by deuterium nuclear magnetic resonance

Molecular-level sorption behavior of monoaromatic compounds in suspensions of water-dispersable clay components was studied by measuring 2H nuclear magnetic resonance (NMR) spin-spin relaxation times (T2). In general, decreased T2 values indicate stronger solute-sorbent interactions and increased sorption of the solute. A decreasing trend for T2 values in the order benzene > fluorobenzene > toluene (-C6D5 moiety) was observed, which was probably caused by the hydrophobic effect. The T2 values for benzene and the -C6D5 moiety of toluene increased with increasing pH, whereas the trend with pH was much weaker and less consistent for fluorobenzene and the methyl group of toluene. Conversely, no clear relationship was found between T2 values and pH for dichloromethane. These contrasting results cannot be explained by the pH-dependent self-assembly and hydrophobicity of humics. Instead, directed specific forces, including hydrogen bonding, cation-pi interactions, and aromatic-aromatic interactions, are proposed between the benzene ring of monoaromatic solutes and soil organic matter (SOM). Substituents of benzene affect these interactions by varying the pi electron density. When the soil fraction was treated with NaOH to remove humic and fulvic acids, T2 values for the different monoaromatic solutes were surprisingly lower compared with those for the untreated soil fraction. This result is probably caused by the increased ratio of solutes adsorbed to "hard" or "glassy" SOM components, which leads to less mobile sorbed solute molecules, after removing NaOH-extractable humics that contain more "soft" or "rubbery" SOM components.     

Assessing potential bioavailability of metals in sediments: A proposed approach

Due to anthropogenic inputs, elevated concentrations of metals frequently occur in aquatic sediments. In order to make defensible estimates of the potential risk of metals in sediments and/or develop sediment quality criteria for metals, it is essential to identify that fraction of the total metal in the sediments that is bioavailable. Studies with a variety of benthic invertebrates indicate that interstitial (pore) water concentrations of metals correspond very well with the bioavailability of metals in test sediments. Many factors may influence pore water concentrations of metals; however, in anaerobic sediments a key phase controlling partitioning of several cationic metals (cadmium, nickel, lead, zinc, copper) into pore water is acid volatile sulfide (AVS). In this paper, we present an overview of the technical basis for predicting bioavailability of cationic metals to benthic organisms based on pore water metal concentrations and metal-AVS relationships. Included are discussions of the advantages and limitations of metal bioavailability predictions based on these parameters, relative both to site-specific assessments and the development of sediment quality criteria.     

Predictive effects of occupational and marital stress on the mental health of a male workforce

This study examined the predictive contribution of occupational and marital stress to the development of symptomatolgoy, affective disorder, and alcohol-related problems in a sample of 325 male power plant employees interviewed at baseline and one-year follow up. After controlling for known clinical and social risk factors, we found statistically significant predictive effects of job demands on affective disorder and job decision latitude on alcohol problems. In addition, the specific combination of high job demands with low decision latitude was important in predicting the occurrence of alcohol problems. Marital stress was not predictive of poorer mental health. The analyses provided only minimal support for a stress-buffering rote of social support.     

Solving Problems in the Electrical Energization of Electrostatic Precipitators

Achieving and maintaining continuous, reliable performance in electrostatic precipitators depends critically upon the proper design, application, operation, and maintenance of the high voltage electrical energization system. Common problems among these factors are discussed, and effects on performance are illustrated from field experience. Practical recommendations for solving problems and for preventing their occurrence in the electrical aspects of precipitation are presented for effective use by designers, operators, and maintenance personnel.     

PROJECT 2000, A PLANNING IMPERATIVE1

Time is running out on this country's planners. Generally speaking, the art of planning has retrogressed since the time of Christ. If we are to survive, this will have to be drastically changed by the year 2000. To achieve this, we need to begin to change our thinking, today. We badly need wider social planning, giving us more alternatives-more thought on where we are going. Reasonableness requires blending of planning and construction-but a sharp line of independence is essential. We must think about all the consequences of a particular act. Through intensive professional development and achievement of professional expertise, many outstanding technicians often move into vital decision making positions within their respective agencies. As planners, they see a part of the action but miss the big picture. Problem solutions become restricted to agency or individual authorities and are not always the best alternative. Thus, the planning field is overflowing with solutions to our every problem but many solutions offer spot control, and while the black spot is removed from the garment the white spot remaining from the solution offers little consolation to the wearer.