Vermont-wide assessment of anthropogenic background concentrations of perfluoroalkyl substances in surface soils.

Shallow surface soils from 66 suburban sampling locations across Vermont were analyzed for 17 different perfluoroalkyl acids (PFAA). PFAA were detected in all 66 surface soils, with a total concentration of PFAA ranging from 540 to 36,000 ng/kg dry soil weight (dw). Despite the complexity of site-specific factors, some general trends and correlations in PFAA concentrations were observed. For instance, perfluoro-1-octanesulfonate (PFOS) dominated in all soil samples while seven other PFAA, including perfluoro-n-nonanoic acid, perfluoro-n-octanoic acid, perfluoro-n-hexanoic acid, perfluoro-n-heptanoic acid, perfluoro-n-decanoic acid, perfluoro-n-undecanoic acid, perfluoro-1-butanesulfonate, and perfluoro-1-hexanesulfonate (PFNA, PFOA, PFHxA, PFHpA, PFDA, PFUnDA, and PFBS, respectively), were identified at more than 50 % of the locations. Perfluoroalkyl carboxylic acids (PFCA) showed a positive correlation with total organic carbon, whereas no clear correlation was observed for perfluoroalkyl sulfonate acids (PFSA). In addition, variations in geographical distributions of PFAA were observed, with relatively higher total PFAA in northern regions when compared to Southern Vermont. Moreover, PFHxA, PFNA, PFDA, PFUnDA, PFOS, and total PFAA were positively correlated to land-use types in Northern Vermont. These results are useful for understanding unique behaviors of PFCA vs. PFSA in geospatially distributed surface soils and for providing anthropogenic background data for setting PFAS cleanup standards for surface soils.

Polychlorinated dibenzo(p)dioxin and furan (PCDD/F) congener profiles in cement kiln emissions and impacts.

Cement kilns are known to emit polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs; "dioxins"), but estimates of the amounts and patterns of these emissions vary widely. These variations may stem from a combination of factors, including the design and operating conditions of the kiln, and the fuels and raw materials fed into the kiln. The goal of this study was to examine the patterns of dioxin emissions in a large set of stack-tests at two Portland cement kilns in Portugal that use a variety of fuels. A total of 152 stack-tests provided data on PCDD/F congener concentrations during which the kilns combusted a varied mix of fuels, including petroleum coke, coal, various "special" supplemental fuels, and refinery distillation ends, which are classified as hazardous wastes. The use of coal to fuel the kilns was found to generate significantly different emission-profiles relative to the use of petroleum coke, but the addition of hazardous wastes as a supplemental fuel did not significantly alter profiles. All of the kiln emission profiles were found to differ markedly from profiles in ambient air. However, the small absolute dioxin emission rates from the kilns suggested that kiln impacts would not be detectable via ambient air monitoring, even in rural settings.

Emissions of metals and polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs) from Portland cement manufacturing plants: inter-kiln variability and dependence on fuel-types.

Emissions from Portland cement manufacturing facilities may increase health risks in nearby populations and are thus subject to stringent regulations. Direct testing of pollutant concentrations in exhaust gases provides the best basis for assessing the extent of these risks. However, these tests (i) are often conducted under stressed, rather than typical, operating conditions, (ii) may be limited in number and duration, and (iii) may be influenced by specific fuel-types and attributes of individual kilns. We report here on the results of more than 150 emissions-tests conducted of two kilns at a Portland cement manufacturing plant in Portugal. The tests measured various regulated metals and polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs). Stack-gas concentrations of pollutants were found to be highly variable, with standard deviations on the order of mean values. Emission rates of many pollutants were higher when coal was used as the main kiln fuel (instead of petroleum coke). Use of various supplemental fuels, however, had little effect on stack emissions, and few statistically significant differences were observed when hazardous waste was included in the fuel mix. Significant differences in emissions for some pollutants were observed between the two kilns despite their similar designs and uses of similar fuels. All measured values were found to be within applicable regulatory limits.