Degradation of ethylenethiourea pesticide metabolite from water by photocatalytic processes

In this study, photocatalytic (photo-Fenton and H₂O₂/UV) and dark Fenton processes were used to remove ethylenethiourea (ETU) from water. The experiments were conducted in a photo-reactor with an 80 W mercury vapor lamp. The mineralization of ETU was determined by total organic carbon analysis, and ETU degradation was qualitatively monitored by the reduction of UV absorbance at 232 nm. A higher mineralization efficiency was obtained by using the photo-peroxidation process (UV/H₂O₂). Approximately 77% of ETU was mineralized within 120 min of the reaction using [H₂O₂]₀ = 400 mg L^?1. The photo-Fenton process mineralized 70% of the ETU with [H₂O₂]₀ = 800 mg L^?1 and [Fe²⁺] = 400 mg L^?1, and there is evidence that hydrogen peroxide was the limiting reagent in the reaction because it was rapidly consumed. Moreover, increasing the concentration of H₂O₂ from 800 mg L^?1 to 1200 mg L^?1 did not enhance the degradation of ETU. Kinetics studies revealed that the pseudo-second-order model best fit the experimental conditions. The k values for the UV/H₂O₂ and photo-Fenton processes were determined to be 6.2 × 10^?4 mg L^?1 min^?1 and 7.7 × 10^?4 mg L^?1 min^?1, respectively. The mineralization of ETU in the absence of hydrogen peroxide has led to the conclusion that ETU transformation products are susceptible to photolysis by UV light. These are promising results for further research. The processes that were investigated can be used to remove pesticide metabolites from drinking water sources and wastewater in developing countries.     

Laboratory Evaluations of the Thermal Degradation Properties of Toxic Organic Materials in Sewage Sludge

Laboratory thermal decomposition studies were performed to evaluate potential emissions from sewage sludge incinerators. Precisely controlled thermal decomposition experiments were conducted on sludge spiked with mixtures of hazardous organic compounds, on mixtures of pure compounds without sludge, and on unspiked sludge. Experiments were conducted in nitrogen and air atmospheres with gas phase reaction times of 2.0 seconds over the temperature range 300°C-1000°C.

It was found that sludge inhibited the decomposition of moderately stable spiked contaminants but accelerated the decomposition of the most stable components. This effect was attributed to radical scavengers produced by the sludge matrix at lower temperatures which then decomposed at higher temperatures. A multiple hearth simulation study suggested that most of the organic material present In the sludge matrix is vaporized within the upper hearths that are held at lower temperatures and may consequently escape from such incinerators undestroyed. A number of stable byproducts resulted from the sludge decomposition that may be of environmental concern.     

Traffic and meteorological impacts on near-road air quality: summary of methods and trends from the Raleigh Near-Road Study

A growing number of epidemiological studies conducted worldwide suggest an increase in the occurrence of adverse health effects in populations living, working, or going to school near major roadways. A study was designed to assess traffic emissions impacts on air quality and particle toxicity near a heavily traveled highway. In an attempt to describe the complex mixture of pollutants and atmospheric transport mechanisms affecting pollutant dispersion in this near-highway environment, several real-time and time-integrated sampling devices measured air quality concentrations at multiple distances and heights from the road. Pollutants analyzed included U.S. Environmental Protection Agency (EPA)-regulated gases, particulate matter (coarse, fine, and ultrafine), and air toxics. Pollutant measurements were synchronized with real-time traffic and meteorological monitoring devices to provide continuous and integrated assessments of the variation of near-road air pollutant concentrations and particle toxicity with changing traffic and environmental conditions, as well as distance from the road. Measurement results demonstrated the temporal and spatial impact of traffic emissions on near-road air quality. The distribution of mobile source emitted gas and particulate pollutants under all wind and traffic conditions indicated a higher proportion of elevated concentrations near the road, suggesting elevated exposures for populations spending significant amounts of time in this microenvironment. Diurnal variations in pollutant concentrations also demonstrated the impact of traffic activity and meteorology on near-road air quality. Time-resolved measurements of multiple pollutants demonstrated that traffic emissions produced a complex mixture of criteria and air toxic pollutants in this microenvironment. These results provide a foundation for future assessments of these data to identify the relationship of traffic activity and meteorology on air quality concentrations and population exposures.     

A new generic approach for estimating the concentrations of down-the-drain chemicals at catchment and national scale

A new generic approach for estimating chemical concentrations in rivers at catchment and national scales is presented. Domestic chemical loads in waste water are estimated using gridded population data. River flows are estimated by combining predicted runoff with topographically derived flow direction. Regional scale exposure is characterised by two summary statistics: PEC(works), the average concentration immediately downstream of emission points, and, PEC(area), the catchment-average chemical concentration. The method was applied to boron at national (England and Wales) and catchment (Aire-Calder) scales. Predicted concentrations were within 50% of measured mean values in the Aire-Calder catchment and in agreement with results from the GREAT-ER model. The concentration grids generated provide a picture of the spatial distribution of expected chemical concentrations at various scales, and can be used to identify areas of potentially high risk.     

The hardrock minerals industry and the landscape architect

The landscape architecture profession is a source of creative thinking and planning which is relatively untapped within the mining industry in the United States of America. The landscape architect has been active in European operations for years as indicated by the four examples presented. The landscape architect can provide an important interface with mine design and engineering and environmental affairs. To initiate this interface within the United States, and increase its effectiveness, six objectives are presented and discussed.     

LED irradiated photo-Fenton for the removal of estrogenic activity and endocrine disruptors from wastewater treatment plant effluent

Environmental Science and Pollution Research - The goal of this work was to evaluate the performance of the LED irradiated photo-Fenton process on the removal of (i) estrogenic activity and (ii)...     

Sustainability and materiality: The bioregional and cultural challenges to evaluation

Concepts of sustainable development have stimulated innovation in the delivery of environmental management. In particular, new partnership approaches have been developed in recognition of the need to adopt more holistic perspectives and facilitate multi-sectoral and cross-sectoral working. River catchments are complex systems and have been one particular focus of experimentation in environmental management mechanisms. This paper provides a brief overview of river management experience in the UK, charting changing approaches in terms of scope and organisation since the 1970s. This sets the context for a more detailed examination of the Mersey Basin Campaign and, in particular, its River Valley Initiatives. The paper concludes with an evaluation of the merits of this approach in relation to sustainable river management.     

A review of light-scattering techniques for the study of colloids in natural waters

In order to understand the movement of colloidal materials in natural waters, we first need to have a means of quantifying their physical characteristics. This paper reviews three techniques which utilize light-scattering phenomena to measure the translational diffusion coefficient, the rotational diffusion coefficient, and the electrophoretic mobility of colloids suspended in water. Primary emphasis is to provide sufficient theoretical detail so that hydrologists can evaluate the utility of photon correlation spectrometry, electrophoretic light scattering, and electric birefringence analysis.