Remediation of a Former Dry Cleaner Using Nanoscale Zero Valent Iron

Nanoscale zero valent iron (nZVI) was evaluated in a laboratory treatability study and subsequently injected as an interim measure to treat source area groundwater impacts beneath a former dry cleaner located in Chapel Hill, North Carolina (the site). Dry cleaning operations resulted in releases of tetrachloroethene (PCE) that impacted site soil at concentrations up to 2,700 mg/kg and shallow groundwater at concentrations up to 41 mg/L. To achieve a design loading rate of 0.001 kg of iron per kilogram of aquifer material, approximately 725 kg of NanoFe? (PARS Environmental) was injected over a two‐week period into a saprolite and partially weather rock aquifer. Strong reducing conditions were established with oxidation–reduction potential (ORP) values below –728 mV. pH levels remained greater than 8 standard units for a period of 12 months. Injections resulted in near elimination of PCE within one month. cis‐1,2‐Dichloroethene accumulated at high concentrations (greater than 65 mg/L) for 12 months. MAROS software (Version 2.2; AFCEE, 2006 ) was used to calculate mass reduction of PCE and total ethenes at 96 percent and 58 percent, respectively, compared to baseline conditions. Detections of acetylene confirmed the presence of the beta‐elimination pathway. Detections of ethene confirmed complete dechlorination of PCE. Based on hydrogen gas generation, iron reactivity lasted 15 months. © 2013 Wiley Periodicals, Inc.     

Junge relationships in measurement data for cyclic siloxanes in air

In 1974, Junge postulated a relationship between variability of concentrations of gases in air at remote locations and their atmospheric residence time, and this Junge relationship has subsequently been observed empirically for a range of trace gases. Here, we analyze two previously-published datasets of concentrations of cyclic volatile methyl siloxanes (cVMS) in air and find Junge relationships in both. The first dataset is a time series of concentrations of decamethylcyclopentasiloxane (D₅) measured between January and June, 2009 at a rural site in southern Sweden that shows a Junge relationship in the temporal variability of the measurements. The second dataset consists of measurements of hexamethylcyclotrisiloxane (D₃), octamethylcyclotetrasiloxane (D₄) and D₅ made simultaneously at 12 sites in the Global Atmospheric Passive Sampling (GAPS) network that shows a Junge relationship in the spatial variability of the three cVMS congeners. We use the Junge relationship for the GAPS dataset to estimate atmospheric lifetimes of dodecamethylcyclohexasiloxane (D₆), 8:2–fluorotelomer alcohol and trichlorinated biphenyls that are within a factor of 3 of estimates based on degradation rate constants for reaction with hydroxyl radical determined in laboratory studies.     

Synoptic evaluation of regional PM2.5 concentrations

By comparing short-term fluctuations in PM2.5 species concentrations among nearby air quality monitors and among species, it becomes possible to understand the regional and local events leading to higher concentrations. This approach was applied at thirteen sites in the Maryland area for the 2001–2006 timeframe in order to identify and explain the behavior of eighteen different analytes as well as the daily Air Quality Index.Findings included identification of local upwind events such as fireworks displays, construction and demolition, the spatial extent of sulfate, nitrate, and ammonium correlations between ground-level monitors, correlations between some crustal species to indicate similar emissions sources in urban areas, and indicators of particle adsorption as a rate-limiting step for certain species. For example, the bromine behavior suggests that bromine concentrations on particulate matter may be limited by the particle adsorption rate and thus show a dependence on the Air Quality Index measurements.     

The toxicology of climate change: Environmental contaminants in a warming world

Climate change induced by anthropogenic warming of the earth's atmosphere is a daunting problem. This review examines one of the consequences of climate change that has only recently attracted attention: namely, the effects of climate change on the environmental distribution and toxicity of chemical pollutants. A review was undertaken of the scientific literature (original research articles, reviews, government and intergovernmental reports) focusing on the interactions of toxicants with the environmental parameters, temperature, precipitation, and salinity, as altered by climate change. Three broad classes of chemical toxicants of global significance were the focus: air pollutants, persistent organic pollutants (POPs), including some organochlorine pesticides, and other classes of pesticides. Generally, increases in temperature will enhance the toxicity of contaminants and increase concentrations of tropospheric ozone regionally, but will also likely increase rates of chemical degradation. While further research is needed, climate change coupled with air pollutant exposures may have potentially serious adverse consequences for human health in urban and polluted regions. Climate change producing alterations in: food webs, lipid dynamics, ice and snow melt, and organic carbon cycling could result in increased POP levels in water, soil, and biota. There is also compelling evidence that increasing temperatures could be deleterious to pollutant-exposed wildlife. For example, elevated water temperatures may alter the biotransformation of contaminants to more bioactive metabolites and impair homeostasis. The complex interactions between climate change and pollutants may be particularly problematic for species living at the edge of their physiological tolerance range where acclimation capacity may be limited. In addition to temperature increases, regional precipitation patterns are projected to be altered with climate change. Regions subject to decreases in precipitation may experience enhanced volatilization of POPs and pesticides to the atmosphere. Reduced precipitation will also increase air pollution in urbanized regions resulting in negative health effects, which may be exacerbated by temperature increases. Regions subject to increased precipitation will have lower levels of air pollution, but will likely experience enhanced surface deposition of airborne POPs and increased run-off of pesticides. Moreover, increases in the intensity and frequency of storm events linked to climate change could lead to more severe episodes of chemical contamination of water bodies and surrounding watersheds. Changes in salinity may affect aquatic organisms as an independent stressor as well as by altering the bioavailability and in some instances increasing the toxicity of chemicals. A paramount issue will be to identify species and populations especially vulnerable to climate–pollutant interactions, in the context of the many other physical, chemical, and biological stressors that will be altered with climate change. Moreover, it will be important to predict tipping points that might trigger or accelerate synergistic interactions between climate change and contaminant exposures.     

Working Wetland Potential: An index to guide the sustainable development of African wetlands

Past experience shows that inappropriate agricultural development in wetlands can undermine sustainability and may have profound social and economic repercussions for people dependent on the range of ecosystem services provided by those wetlands. Nonetheless, there is escalating pressure to expand agriculture within wetlands due to increasing population, in conjunction with efforts to increase food security. This paper describes the development of a semi-analytical framework for identifying, organizing and analyzing the complex factors that link people, agriculture and wetland ecosystems — an index of Working Wetland Potential (WWP). The method is based on a form of multi-criteria analysis that integrates biophysical and socio-economic aspects of wetland utilization. The WWP index emerges from the aggregation of two values: the first arising from an appraisal of both the biophysical and socio-economic suitability of using the wetland for agriculture; and the second resulting from an assessment of the possible hazards, in relation to both social welfare and the ecological character of the wetland. Hence, the approach provides a way to explicitly integrate biophysical and social aspects of wetland utilization in a single index to enable an initial assessment of the suitability of using a wetland for agriculture. Results from three contrasting wetlands in sub-Saharan Africa are presented.     

Vascular function and short-term exposure to fine particulate air pollution

Exposure to fine particulate air pollution has been implicated as a risk factor for cardiopulmonary disease and mortality. Proposed biological pathways imply that particle-induced pulmonary and systemic inflammation play a role in activating the vascular endothelium and altering vascular function. Potential effects of fine particulate pollution on vascular function are explored using controlled chamber exposure and uncontrolled ambient exposure. Research subjects included four panels with a total of 26 healthy nonsmoking young adults. On two study visits, at least 7 days apart, subjects spent 3 hr in a controlled-exposure chamber exposed to 150-200 microg/m3 of fine particles generated from coal or wood combustion and 3 hr in a clean room, with exposure and nonexposure periods alternated between visits. Baseline, postexposure, and post-clean room reactive hyperemia-peripheral arterial tonometry (RH-PAT) was conducted. A microvascular responsiveness index, defined as the log of the RH-PAT ratio, was calculated. There was no contemporaneous vascular response to the few hours of controlled exposure. Declines in vascular response were associated with elevated ambient exposures for the previous 2 days, especially for female subjects. Cumulative exposure to real-life fine particulate pollution may affect vascular function. More research is needed to determine the roles of age and gender, the effect of pollution sources, the importance of cumulative exposure over a few days versus a few hours, and the lag time between exposure and response.     

Chemical speciation of PM2.5 and PM10 in south Phoenix, AZ, USA

Phoenix, AZ, experiences high particulate matter (PM) episodes, especially in the wintertime. The spatial variation of the PM concentrations and resulting differences in exposure is of particular concern. In this study, PM2.s (PM with aerodynamic diameter <2.5 microm) and PM10 (PM with aerodynamic diameter <10 microm) samples were collected simultaneously from the east and west sides of South Phoenix and at a control site in Tempe and analyzed for trace elements and bulk elemental and organic carbon. Measurements showed that although PM2.5 concentrations had similar trends in temporal scale across all sites, concentrations of PM10 did not. The difference in PM10 concentrations and fluctuation across the three sites suggest effects of a local soil source as evidenced by high concentrations of Al, Ca, and Fe in PM10. K and anthropogenic elements (e.g., Cu, Pb, and Zn) in PM2.5 samples on January 1 were strikingly high, suggesting the influence of New Year's fireworks. Concentrations of toxic elements (e.g., Pb) in the study presented here are not different from similar studies in other U.S. cities. Application of principal component analysis indicated two broad categories of emission sources--soil and combustion--together accounting for 80 and 90% of variance, respectively, in PM2.5 and PM10. The soil and combustion components explained approximately 60 and 30% of the variance in PM10, respectively, whereas combustion sources dominated PM2.5 (>50% variance). Many elements associated with anthropogenic sources were highly enriched, with enrichment factors in PM2.5 an order of magnitude higher than in PM10 relative to surface soil composition in the study area.     

An analysis of flaring and venting activity in the Alberta upstream oil and gas industry

Alberta, Canada, is an important global producer of petroleum resources. In association with this production, large amounts of gas (1.14 billion m3 in 2008) are flared or vented. Although the amount of flaring and venting has been measurably reduced since 2002, data from 2005 reveal sharp increases in venting, which have important implications in terms of resource conservation and greenhouse gas emissions (which exceeded 8 million tonnes of carbon dioxide equivalent in 2008). With use of extensive monthly production data for 18,203 active batteries spanning the years 2002-2008 obtained in close cooperation with the Alberta Energy Resources Conservation Board, a detailed analysis has been completed to examine activity patterns of flaring and venting and reasons behind these trends in the Alberta upstream oil and gas industry. In any given year, approximately 6000 batteries reported flaring and/or venting, but the distribution of volumes flared and vented at individual sites was highly skewed, such that small numbers of sites handled large fractions of the total gas flaring and venting in the Province. Examination of month-to-month volume variability at individual sites, cast in terms of a nominal turndown ratio that would be required for a compressor to capture that gas and direct it into a pipeline, further revealed that volumes at a majority of sites were reasonably stable and there was no evidence that larger or more stable sites had been preferentially reduced, leaving potential barriers to future mitigation. Through linking of geospatial data with production data coupled with additional statistical analysis, the 31.2% increase in venting volumes since 2005 was revealed to be predominantly associated with increased production of heavier oils and bitumen in the Lloydminster region of the Province. Overall, the data suggest that quite significant reductions in flaring and venting could be realized by seeking mitigation solutions for only the largest batteries in the Province.     

Aluminum water treatment residuals as permeable reactive barrier sorbents to reduce phosphorus losses

Two aluminum water treatment residuals (Al-WTRs) from water treatment plants in Manatee County, FL and Punta Gorda, FL were evaluated as potential permeable reactive barrier (PRB) media to reduce groundwater phosphorus (P) losses. Short-term (<24 h) P sorption kinetics and long-term P sorption capacity were determined using batch equilibration studies. Phosphorus desorption was characterized following P loadings of 10, 20, 30, 40 and >70 g kg⁻¹. Sorption and desorption studies were conducted on the <2.0 mm material and three size fractions within the <2.0 mm material. The effect of dissolved organic carbon (DOC) on P retention was determined by reacting Al-WTRs with P-spiked groundwater samples of varying initial DOC concentrations. Phosphorus sorption kinetics were rapid for all size fractions of both Al-WTRs (>98% P sorption effectiveness at shaking times ?2 h). The effect of DOC was minimal at <150 mg DOC L⁻¹, but modest reductions (<22%) in P sorption effectiveness occurred at 587 mg DOC L⁻¹. The P sorption capacities of the Manatee and Punta Gorda Al-WTRs (<2.0 mm) are ∼44 g kg⁻¹ and >75 g kg⁻¹, respectively, and the lifespan of an Al-WTR PRB is likely many decades. Desorption was minimal (<2% of the P sorbed) for cumulative P loadings <40 g kg^-l, but increased (<9% of the P sorbed) at cumulative P loads >70 g kg⁻¹. The <2.0 mm Manatee and Punta Gorda Al-WTRs are regarded as ideal PRB media for P remediation.     

Tetracycline photolysis in natural waters: loss of antibacterial activity

Previous work has shown that tetracycline undergoes direct photolysis in the presence of sunlight, with the decomposition rate highly dependent on conditions such as water hardness and pH. The purpose of this study was to examine the potential long-term significance of photoproducts formed when tetracycline undergoes photodegradation under a range of environmentally relevant conditions. Tetracycline was photolyzed in nine different natural and artificial water samples using simulated sunlight. The pH values of the samples ranged from 5 to 9. Total hardness values (combined Ca²⁺ and Mg²⁺ concentrations) varied from 30 to 450 ppm. Assays based on growth inhibition of two bacterial strains, Escherichia coli DH5α and Vibrio fischeri, were used to determine the antibacterial activity of tetracycline’s photoproducts in these water samples. In all tested conditions, it was determined that the photoproducts retain no significant antibacterial activity; all observed growth inhibition was attributable to residual tetracycline. This suggests that tetracycline photoproducts formed under a wide range of pH and water hardness conditions will not contribute to the selection of antibiotic-resistant bacteria in environmental systems.