Profiling the spatial concentration of allethrin and piperonyl butoxide using passive sorptive sampling and thermal desorption capillary GC-MS

Spatial concentration distribution of a chemical in an indoor environment is an important factor in the evaluation of chemical nuisances. However, straightforward techniques for the determination of this distribution are not very common and usually limited in their application. Sorptive sampling using polydimethylsiloxane-coated stir bars and the combination of active and diffusive sampling were shown to allow uncomplicated spatial concentration profiling of multiple compounds in an indoor environment. The validity of the approach was demonstrated in the analysis of the spatial concentration distribution of a pyrethroid insecticide in a common bedroom. The relative concentrations of allethrin and piperonyl butoxide were profiled throughout the room upon the application of an insecticide vaporizer.     

Demarcating coastal vegetation buffers with multicriteria evaluation and GIS at Saldanha Bay, South Africa

The Saldanha-Langebaan coastal zone forms an integral part of the South African coastal resource base. As elsewhere in the world, an acute need exists to balance development and economic growth and conservation in the coastal zone as an exploitable resource frontier area. Vegetated buffers and greenways are conservation concepts that have been used with great success in such conservation efforts. They are applied in the study area through the use of a Geographic Information System (GIS) as spatial decision-support system to legitimize the demarcation of a vegetated buffer zone. The method of multicriteria evaluation, as applied here, incorporates public decision-making in constructing an objective model for buffer zone demarcation. Representatives from interested and affected parties participated in model construction and calibration, resulting in the spatial delimitation of a multifunctional vegetated buffer. It conforms to a range of functional criteria and can serve as an environmental element in coastal conservation planning frameworks.     

An integrated test strategy for the assessment of anaerobic biodegradability of wastewaters

The anaerobic biodegradability of wastewaters from different chemical plants was determined by an integrated test strategy consisting of an anaerobic toxicity test, a static anaerobic biodegradation test and a continuously operated fixed bed reactor test. This integrated procedure offered a useful tool for screening wastewaters for anaerobic biodegradability. Four different wastewaters were tested for anaerobic toxicity and biodegradability. One wastewater was used in subsequent testing in a fixed bed reactor which aimed to illustrate a potential design of an anaerobic treatment plant.     

A model of oscillatory transport in granular soils, with application to barometric pumping and earth tides

A simple algebraic model is proposed to estimate the transport of a volatile or soluble chemical caused by oscillatory flow of fluid in a porous medium. The model is applied to the barometric pumping of vapors in the vadose zone, and to the transport of dissolved species by earth tides in an aquifer. In the model, the fluid moves sinusoidally with time in the porosity of the soil. The chemical concentration in the mobile fluid is considered to equilibrate with the concentration in the surrounding matrix according to a characteristic time governed by diffusion, sorption, or other rate processes. The model provides a closed form solution, to which barometric pressure data are applied in an example of pore gas motion in the vadose zone. The model predicts that the additional diffusivity due barometric pumping in an unfractured vadose zone would be comparable to the diffusivity in stagnant pore gas if the equilibration time is 1 day or longer. Water motion due to the M2 lunar tide is examined as an example of oscillatory transport in an aquifer. It is shown that the tidal motion of the water in an aquifer might significantly increase the vertical diffusivity of dissolved species when compared to diffusion in an absolutely stagnant aquifer, but the hydrodynamic dispersivity due to tidal motion or gravitational flow would probably exceed the diffusivity due to oscillatory advection.     

Source-term development for a contaminant plume for use by multimedia risk assessment models

Multimedia modelers from the US Environmental Protection Agency (EPA) and US Department of Energy (DOE) are collaborating to conduct a comprehensive and quantitative benchmarking analysis of four intermedia models: MEPAS, MMSOILS, PRESTO, and RESRAD. These models represent typical analytically based tools that are used in human-risk and endangerment assessments at installations containing radioactive and hazardous contaminants. The objective is to demonstrate an approach for developing an adequate source term by simplifying an existing, real-world, ⁹⁰Sr plume at DOE's Hanford installation in Richland, WA, for use in a multimedia benchmarking exercise between MEPAS, MMSOILS, PRESTO, and RESRAD. Source characteristics and a release mechanism are developed and described; also described is a typical process and procedure that an analyst would follow in developing a source term for using this class of analytical tool in a preliminary assessment.     

Urban returns to scale and environmental resources: an estimate of environmental externalities in an urban production function

The paper deals with the measurement of the economic advantages and environmental disadvantages of an urban setting. Based on a large sample of Italian cities, the paper provides results from an estimate of an urban production function which contains, in addition to the traditional labour and capital production factors, a variable representing the environmental resource consumption and the negative environmental externalities associated with urban life. A major result highlighted in the paper is that cities have in themselves mechanisms to favour an efficient consumption of environmental resources; however, the use of these resources has a cost in terms of environmental output, of negative externalities that are generated on the environment and which become worse by increasing the urban size.     

The Formulation of Emission Control Strategies Using a Cubic Polynomial Approximation

Assuming the existence of an ambient air standard for a given pollutant, there is some agreement that emission standards for local area and point sources should be established by formulating and testing various “control strategies” with use of a computer diffusion model. The procedure requires several, perhaps many, computer simulations of pollutant dispersion followed by an analysis of the results of each simulation. Part of this analysis is to include an “optimization” of sorts which is intended to provide a workable control strategy which, in turn, is to indicate required emission level reductions for point sources. This paper is intended to describe and apply an approximation technique which, when used in conjunction with a diffusion model, could be of value in determining acceptable emission levels for point sources.     

Light-induced formation of hydroxyl radicals in fog waters determined by an authentic fog constituent,hydroxymethanesulfonate

The determination of the photo-production rate of hydroxyl radical (OH) in atmospheric liquids is of fundamental importance to an understanding of atmospheric aquatic chemistry. Recently, several studies have been performed to examine the photo-chemical formation rate of OH in cloud and fog waters using a free radical quenching technique with addition of a relatively large concentration of organic compounds as an OH scavenger. The addition of free-radical scavenger chemicals may significantly alter the nature of the sample water and its OH production rate. In this paper, an authentic constituent, hydroxymethanesulfonate, is proposed as a free radical probe for the measurement of photo-chemical generation rate of OH in fog water. At 313 nm, an apparent quantum yield for the production of OH in a fog water was found to be 0.012+/-0.001, indicating that aqueous-phase photo-chemical processes could represent a significant and may be a dominant source of OH in atmospheric liquids.     

A Cost-Benefit Approach to Air Pollution Control

Air pollution has plagued the urban areas of our Nation for many years, both as a serious health hazard and as a costly economic burden. Users of the air as a waste disposal medium have treated it as a free resource with no regard for the damages incurred by receptors of the dirty air. Unfortunately, no self-regulating market forces exist that will bring this diseconomy into an acceptable equilibrium. An outside regulating force, which can affect abatement of air pollution, is needed to achieve control of air pollution to a level acceptable to a community. A prerequisite of any proposed regulatory action to be applied by an outside force, however, is the need to define an acceptable level of pollution. One means of accomplishing the task is to apply an economic evaluation, in the form of a cost-benefit analysis, to the problem. Previous analyses of the economic aspects of air pollution have stressed only one side of the problem. That is, they have dealt only with the cost of control or the damages caused by air pollution. No analysis has combined both aspects into a meaningful analysis of the overall economic impact. The objective of this paper is to present a technique that can be used to find the level of pollution abatement in an area that balances the cost of controlling pollution with the benefits received from its control. To present a clearer picture of this technique and its results, it has been applied to the Washington, D. C. area to find the optimum level of particulate abatement. This method is generally applicable to any area, in which an air pollution problem exists.     

The probability of NAAQS nonattainment when exceedance outcomes constitute a two-state Markov process

The pattern of annual exceedances of a short-term National Ambient Air Quality Standard (NAAQS) likely under an assumption of independence is compared to the pattern likely under an assumption that exceedance outcomes constitute a two-state Markov process. The probability distribution of the annual number of exceedances is approximated by the Poisson distribution if independence is assumed and by the Polya-Aeppli distribution under the Markov assumption. This provides a simple setting for gauging the effect of autocorrelation on the probability of attaining a short-term standard. The maximum effect is calculated and the consequences of such an effect on emission rollback factors are illustrated.     

Parameters governing permeate flux in an anaerobic membrane bioreactor treating low-strength municipal wastewaters: a literature review.

The objective of this review was to conduct a comprehensive literature survey to identify the parameters that govern the permeate flux in an anaerobic membrane bioreactor (AnMBR) treating municipal wastewater. Based on the survey, research to date indicates that the optimal membrane system for an AnMBR consists of an organic, hydrophilic, and negatively charged membrane with a pore size of approximately 0.1 microm. The use of both external and submerged membrane configurations shows promise. The operating parameters that affect permeate flux in an external membrane system are transmembrane pressure (TMP) and cross-flow velocity. The operating parameters that affect permeate flux in a submerged membrane system are TMP, sparging intensity, and duration of the relaxation period. Both cross-flow velocity and sparging intensity impart a significant amount of shear force on the biomass in an AnMBR. High shear forces can reduce the microbial activity in an AnMBR. In addition, high shear forces can reduce the size of the biosolids in the mixed liquor and increase the release of soluble microbial products. In this respect, external and submerged membrane systems are expected to perform differently because the magnitude of the shear forces to which the biomass is exposed in an external membrane system is significantly greater than that in a submerged system. The size of the biosolid particles and concentration of soluble microbial products in the mixed liquor affect permeate flux. Higher concentrations of soluble microbial products may be present in the mixed liquor when an AnMBR is operated at relatively low operating temperatures. Aerobic polishing following anaerobic treatment can potentially significantly reduce the concentration of some components of the soluble microbial products in the mixed liquor. It is not possible to remove the foulant layer on an organic membrane with caustic cleaning alone. Acidic cleaning or acidic cleaning followed by caustic cleaning is required to remove the foulant layer. This suggests that both biological/organic and inorganic material contribute to membrane fouling.     

Effect of formaldehyde on biofilm activity and morphology in an ultracompact biofilm reactor for carbonaceous wastewater treatment.

The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity.     

Forecasting Air Pollution Potential: A Synoptic Climatological Approach

ABSTRACT

This paper describes the development and application of an air pollution potential (APP) forecast model based on a synoptic climatological approach in a heavily industrialized area in Durban, South Africa. The aim of the forecasting procedure, based on a system of orange, red, and all-clear alerts, was to give industry advance warning of periods of poor atmospheric dispersion so that it could take action to reduce emissions. The key meteorological parameter in accurately identifying the commencement of an APP episode was found to be negative surface pressure tendency. Wind direction was the most useful parameter in estimating the end point of an APP episode. The model was very successful in identifying periods of elevated SO₂, but there is a need for further refinement in forecasting the end point of an episode.     

Compatibility analysis of material and energy recovery in a regional solid waste management system

The rising prices of raw materials and concerns about energy conservation have resulted in an increasing interest in the simultaneous recovery of materials and energy from waste streams. Compatibility exists for several economic, environmental, and managerial reasons. Installing an on-site or off-site presorting facility before an incinerator could be a feasible alternative to achieve both goals if household recycling programs cannot succeed in local communities. However, the regional impacts of presorting solid waste on a waste-to-energy facility remain unclear because of the inherent complexity of solid waste compositions and properties over different areas. This paper applies a system-based approach to assess the impact of installing a refuse-derived fuel (RDF) process before an incinerator. Such an RDF process, consisting of standard unit operations of shredding, magnetic separation, trommel screening, and air classification, might be useful for integrating the recycling and presorting efforts for a large-scale municipal incinerator from a regional sense. An optimization modeling analysis is performed to characterize such integration potential so that the optimal size of the RDF process and associated shipping patterns for flow control can be foreseen. It aims at exploring how the waste inflows with different rates of generation, physical and chemical compositions, and heating values collected from differing administrative districts can be processed by either a centralized presorting facility or an incinerator to meet both the energy recovery and throughput requirements. A case study conducted in Taipei County, which is one of the most densely populated metropolitan areas in Taiwan, further confirms the application potential of such a cost-benefit analysis.     

Engineering risk assessment for emergency disposal projects of sudden water pollution incidents

Without an engineering risk assessment for emergency disposal in response to sudden water pollution incidents, responders are prone to be challenged during emergency decision making. To address this gap, the concept and framework of emergency disposal engineering risks are reported in this paper. The proposed risk index system covers three stages consistent with the progress of an emergency disposal project. Fuzzy fault tree analysis (FFTA), a logical and diagrammatic method, was developed to evaluate the potential failure during the process of emergency disposal. The probability of basic events and their combination, which caused the failure of an emergency disposal project, were calculated based on the case of an emergency disposal project of an aniline pollution incident in the Zhuozhang River, Changzhi, China, in 2014. The critical events that can cause the occurrence of a top event (TE) were identified according to their contribution. Finally, advices on how to take measures using limited resources to prevent the failure of a TE are given according to the quantified results of risk magnitude. The proposed approach could be a potential useful safeguard for the implementation of an emergency disposal project during the process of emergency response.

     

Forecasting air pollution potential: a synoptic climatological approach

This paper describes the development and application of an air pollution potential (APP) forecast model based on a synoptic climatological approach in a heavily industrialized area in Durban, South Africa. The aim of the forecasting procedure, based on a system of orange, red, and all-clear alerts, was to give industry advance warning of periods of poor atmospheric dispersion so that it could take action to reduce emissions. The key meteorological parameter in accurately identifying the commencement of an APP episode was found to be negative surface pressure tendency. Wind direction was the most useful parameter in estimating the end point of an APP episode. The model was very successful in identifying periods of elevated SO2, but there is a need for further refinement in forecasting the end point of an episode.     

Exceptional weather in the midlands, UK, during 1988-1990 results in the rapid acidification of an upland stream

Numerous catchment studies have identified the control exerted by hydrological processes on short-term (within a year) fluctuations in surface water acidity. Because discharge is, in turn, a function of broad climate parameters, there has been growing interest in the potential impact of changing precipitation and temperature regimes on water chemistry. The exceptionally warm and arid period 1988-1990 provided an opportunity to investigate the response of an acidic catchment in the East Midlands to an extreme climate scenario. The results obtained from three years of intensive monitoring indicated that between 1988 and 1990 there was a fourfold increase of the surface-water acidity at several observation sites within the Beacon catchment, Charnwood Forest, Leicestershire. As well as providing an indication of currently extreme hydrochemical conditions which in the near future may become the norm, these observations also have a bearing on the validity of long-term predictions derived from process-orientated models.     

Nonpoint source pollution of urban stormwater runoff: a methodology for source analysis

The characterization and control of runoff pollution from nonpoint sources in urban areas are a major issue for the protection of aquatic environments. We propose a methodology to quantify the sources of pollutants in an urban catchment and to analyze the associated uncertainties. After describing the methodology, we illustrate it through an application to the sources of Cu, Pb, Zn, and polycyclic aromatic hydrocarbons (PAH) from a residential catchment (228 ha) in the Paris region. In this application, we suggest several procedures that can be applied for the analysis of other pollutants in different catchments, including an estimation of the total extent of roof accessories (gutters and downspouts, watertight joints and valleys) in a catchment. These accessories result as the major source of Pb and as an important source of Zn in the example catchment, while activity-related sources (traffic, heating) are dominant for Cu (brake pad wear) and PAH (tire wear, atmospheric deposition).     

A combined first-order closure/gaussian dispersion model

A dispersion model incorporating a large wind direction shear has been developed for an industrialized coastal area with an indented coastline and rough terrain. The model is based on a first-order closure solution for the vertical spread and a Gaussian profile for the lateral spread. Lateral spread is obtained by numerical integration of turbulent energy spectra. The model is verified against a large number of tracer experiments with near surface release within industrial complexes. The model is shown to correctly simulate shear-enhanced spread out to a distance of 10 km from the source. Part of the observed scatter is believed to be the result of an oversimplified plume rise calculation.     

Responses of juvenile European flounder (Platichthys flesus) to multistress in the Vilaine estuary, during a 6-month survey

Physiological and genetic responses of age 0+ Platichthys flesus were investigated in the eutrophicated and moderately contaminated Vilaine estuary, during a 6-month survey. The main objective of this study was to explore the biological responses of fishes during their juvenile period in an estuarine system in order to detect a possible selective pressure induced by the environmental stress. Our results showed a general convergence in physiological responses along the survey: an increase in genotoxicity was associated with an increase in mRNA expression of ATPase and betaine homocysteine methyltransferase. These results could suggest an increase of cellular damage, energetic request, and detoxification rate related to the growing exposure time to stress. Considering the aging of the cohort, the genetic characteristics of the Vilaine flounder cohort came closer to the one observed in a highly stressed system, the Seine estuary, suggesting a potential selective pressure mainly induced by the chemical stress.