Monitoring and modelling of siloxanes in a sewage treatment plant in the UK

Monitoring of cyclic volatile methylsiloxanes (cVMS) carried out at Anglian Water’s Broadholme sewage treatment plant (STP) is described. The method deployed used headspace gas chromatography/mass spectrometry (HS-GC/MS) and the addition of isotopically labelled cVMS to correct for partitioning in samples containing high levels of particulate and dissolved organic carbon. The method was capable of measuring cVMS in raw sewage samples, with recoveries of 80%, 85% and 71% respectively, for D₄, D₅ and D₆. The limit of quantification was 0.2 μg L⁻¹ for all three substances. Recoveries close to 100% were observed for all cVMS spiked into treated effluent (LOQ = 0.01 μg L⁻¹). Despite the volatile nature of cVMS and its ubiquitous presence in the ambient atmosphere, the methods deployed showed excellent recoveries, reproducibility and quantification limits. A distinct diurnal variation in cVMS concentration, probably linked with the use of personal care products was observed for raw sewage but not in treated sewage effluent. The estimated per capita consumption of D₅ (∼2.7 mg cap⁻¹ d⁻¹) derived for the population served by this plant was significantly lower than that derived in the Environment Agency (UK) risk assessment (11.6 mg cap⁻¹ d⁻¹). The cVMS were highly removed during sewage treatment with efficiencies greater than 98%. The methods and findings of this pilot study can be used as the basis for future studies on the fate of cVMS substances in STPs.     

Nontarget deposition and losses of chlorothalonil in irrigation runoff water from a commercial foliage plant nursery

Commercial foliage plant production requires the use of pesticides for controlling pests and pathogens that can reduce aesthetic qualities of crops, rendering them unwanted by consumers. Chlorothalonil is a common, broad-spectrum, foliar fungicide used for protecting plants from a variety of fungal diseases. This fungicide may also be acutely toxic to nontarget aquatic organisms due to its mode of action. This study evaluated the amount of chlorothalonil deposited on nontarget ground surfaces during normal sprayer applications at a commercial nursery using Teflon targets. One day following application, irrigation runoff events were initiated and runoff water samples were collected and analyzed for chlorothalonil. Discharge volumes were also measured to allow estimation of the total mass of chlorothalonil discharged during each event. Results indicated that 9.8 to 53.6% of the active ingredient applied landed on nontarget ground surfaces depending on plant size, spacing, and row lengths (short rows sprayed from one side vs. longer rows sprayed from both ends). On an entire production-area scale, 29.2% of the active ingredient applied was deposited on ground surfaces. Of the total nontarget deposition, 0.25 to 0.53% was detected in runoff water discharged from the production area. Concentrations ranged from 1.2 to 500 microg/L during the first runoff events following application.     

Illicit drugs in Canadian municipal wastewater and estimates of community drug use

In this study of wastewater treatment plants in three Canadian cities, selected illicit drugs, including cocaine and its major metabolite, benzoylecgonine (BE), amphetamine, methamphetamine and ecstasy (i.e. MDMA) were detected in untreated wastewater. Cocaine was the most widely used illicit drug at a median level for the 3 cities of 15.7 doses per day per 1000 people. For the other drugs, the median doses per day per 1000 people were 1.8 for amphetamine, 4.5 for methamphetamine and 0.4 for ecstasy. Methamphetamine use was highest in the largest city and cocaine use was lowest in the smallest city. Removal of the illicit drugs by wastewater treatment was generally >50%, except in a WWTP that uses primary treatment. The community consumption estimate for ecstasy in the present study is far below published estimates of the prevalence of ecstasy use among the Canadian population, which may be due to only occasional use of ecstasy.     

Body burdens of polybrominated diphenyl ethers in childbearing-aged women at an intensive electronic-waste recycling site in China

Background, aim and scope  

This study is the first to investigate PBDE body burden with regard to the concurrent analyses of multiple human matrices, namely milk, placenta, and hair, collected from a group of childbearing-aged women at an electronic waste (e-waste) recycling site to determine the partitioning of PBDEs in these different human matrices and the possible health risks imposed to infants at the e-waste recycling site.     

Guidance for the Performance Evaluation of Three-Dimensional Air Quality Modeling Systems for Particulate Matter and Visibility

ABSTRACT

Guidance for the performance evaluation of three-dimensional air quality modeling systems for particulate matter and visibility is presented. Four levels are considered: operational, diagnostic, mechanistic, and probabilistic evaluations. First, a comprehensive model evaluation should be conducted in at least two distinct geographical locations and for several meteorological episodes. Next, streamlined evaluations can be conducted for other similar applications if the comprehensive evaluation is deemed satisfactory. In all cases, the operational evaluation alone is insufficient, and some diagnostic evaluation must always be carried out. Recommendations are provided for designing field measurement programs that can provide the data needed for such model performance evaluations.     

Emission Factors for High-Emitting Vehicles Based on On-Road Measurements of Individual Vehicle Exhaust with a Mobile Measurement Platform

ABSTRACT

Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NO_x), and particle mass with aerodynamic diameter below 2.5 μm (PM_2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NO_x, black carbon (BC), PM_2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NO_x and CO fleet-average emission factors and more than 60% of PM_2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM_2.5, and NO_x tended to cluster among the same vehicles.

IMPLICATIONS This study presents the characterization of on-road vehicle emissions in Wilmington, CA, by sampling individual vehicle plumes. Approximately 5% of the vehicles were high emitters, whose emissions were more than 5 times the fleet-average values. These high emitters were responsible for 30% and more than 50% of the average emission factors of LDGVs and HDDVs, respectively. It is likely that as the overall fleet becomes cleaner due to more stringent regulations, a small fraction of the fleet may contribute a growing and disproportionate share of the overall emissions. Therefore, long-term changes in on-road emissions need to be monitored.     

Soil intervention as a strategy for lead exposure prevention: the New Orleans lead-safe childcare playground project

The feasibility of reducing children's exposure to lead (Pb) polluted soil in New Orleans is tested. Childcare centers (median = 48 children) are often located in former residences. The extent of soil Pb was determined by selecting centers in both the core and outlying areas. The initial 558 mg/kg median soil Pb (range 14-3692 mg/kg) decreased to median 4.1 mg/kg (range 2.2-26.1 mg/kg) after intervention with geotextile covered by 15 cm of river alluvium. Pb loading decreased from a median of 4887 μg/m(2) (454 μg/ft(2)) range 603-56650 μg/m(2) (56-5263 μg/ft(2)) to a median of 398 μg/m(2) (37 μg/ft(2)) range 86-980 μg/m(2) (8-91 μg/ft(2)). Multi-Response Permutation Procedures indicate similar (P-values = 0.160-0.231) soil Pb at childcare centers compared to soil Pb of nearby residential communities. At ～$100 per child, soil Pb and surface loading were reduced within hours, advancing an upstream intervention conceptualization about Pb exposure prevention.     

Temporal trends in polychlorinated dibenzo-p-dioxins and dibenzofurans, dioxin-like PCBs, and polybrominated diphenyl ethers in Niagara river suspended sediments

Archived suspended sediment samples collected over the period 1980-2002 at Niagara-on-the-Lake in the Niagara river were analyzed to assess temporal trends in contaminants associated with historical industrial activities in the watershed (PCDDs/PCDFs, DLPCBs), compared to more modern industrial chemicals (PBDEs). The temporal trends for PCDDs/PCDFs and DLPCBs were generally similar, and showed a general trend toward decreasing concentrations, which was presumably due to implementation of control measures in the Niagara river watershed, including the remediation of hazardous waste facilities. The temporal trend in PBDEs contrasted with those of PCDDs/PCDFs and DLPCBs. Prior to 1988, PBDEs (sum of 16 congeners including deca-BDE) were generally detected at low-ppb concentrations, but showed a trend toward increasing concentrations over the period 1980-1988. After 1988, PBDE concentrations in the Niagara river showed a more rapidly increasing trend to a maximum of approximately 35 ng/g in 1995, with deca-BDE as the predominant congener detected. Samples collected over the period February 2003 to March 2004 at the head and mouth of the Niagara river were also analyzed for PBDEs; in all cases PBDE concentrations were higher at the mouth of the river at the outflow to Lake Ontario, indicating the Niagara river watershed is a source of PBDE contamination to Lake Ontario. However, PBDE concentrations in suspended sediments of the Niagara river were comparable to, or lower than, concentrations in bottom sediments in other industrialized/urbanized areas of the world. Based on these comparisons of global PBDE bottom sediment concentrations, the Niagara river watershed does not appear to be a significant local source of PBDEs to Lake Ontario, and concentrations in suspended sediments appear to be indicative of general PBDE contamination from a contamination of local, regional, and continental sources.     

Emissions of chromium (VI) from arc welding

The presence of Cr in the +6 oxidation state (Cr[VI]) is still observed in ambient air samples in California despite steps taken to reduce emissions from plating operations. One known source of emission of Cr(VI) is welding, especially with high Cr-content materials, such as stainless steels. An experimental effort was undertaken to expand and update Cr(VI) emission factors by conducting tests on four types of arc-welding operations: gas-metal arc welding (GMAW), shielded metal arc welding (SMAW), fluxcore arc welding, and pulsed GMAW. Standard American Welding Society hood results were compared with a total enclosure method that permitted isokinetic sampling for particle size-cut measurement, as well as total collection of the aerosol. The fraction of Cr(VI) emitted per unit mass of Cr electrode consumed was determined. Consistent with AP-42 data, initial results indicate that a significant fraction of the total Cr in the aerosol is in the +6 oxidation state. The fraction of Cr(VI) and total aerosol mass produced by the different arc welding methods varies with the type of welding process used. Self-shielded electrodes that do not use a shield gas, for example, SMAW, produce greater amounts of Cr(VI) per unit mass of electrode consumed. The formation of Cr(VI) from standard electrode wires used for welding mild steel was below the method detection limit after eliminating an artifact in the analytical method used.