Distribution of select per- and polyfluoroalkyl substances at a chemical manufacturing plant.

Per- and polyfluoroalkyl substances (PFAS) are used in various industrial products; however, they pose serious health risks. In this study, soil, soil gas, and groundwater samples were collected at a PFAS manufacturing facility in New Jersey, USA, to determine the presence and distribution of PFASs from the soil surface to groundwater and at various distances from the presumed source. Fluorotelomer alcohols (FTOHs) were detected in soil (< 0.26-36.15 ng/g) and soil gas (160-12,000 E µg/m3), while perfluorinated carboxylic acids (PFCAs) were found in soil (4.3-810 ng/g), soil gas (<0.10-180 µg/m3), and groundwater (37-49 µg/L). FTOH and PFCA concentrations decreased as the distance from the presumed source increased, suggesting that PFCAs are likely to migrate in groundwater, whereas FTOHs primarily move in the vapor phase. The presence of PFAS in the groundwater, soil, and soil gas samples indicate its potential for vapor intrusion; thus, some PFAS may contribute to indoor air inhalation exposure. To the best of our knowledge, this is the first report on the quantification of volatile PFAS in soil gas at a PFAS manufacturing facility.

Comparison of modeled and measured indoor air trichloroethene (TCE) concentrations at a vapor intrusion site: influence of wind, temperature, and building characteristics.

There is a lack of vapor intrusion (VI) models that reliably account for weather conditions and building characteristics, especially at sites where active alternative pathways, such as sewer connections and other preferential pathways, are present. Here, a method is presented to incorporate freely-available models, CONTAM, and CFD0, to estimate site-specific building air exchange rates (AERs) and indoor air contaminant concentrations by accounting for weather conditions and building characteristics at a well-known VI site with a land drain preferential pathway. To account for uncertainty in model input parameters that influence indoor air chlorinated volatile organic compound (CVOC) concentration variability, this research incorporated Monte Carlo simulations and compared model results with retrospective field data collected over approximately 1.5 years from the study site. The results of this research show that mass entry rates for TCE are likely influenced by indoor air pressures that can be modeled as a function of weather conditions (over seasons) and building characteristics. In addition, the results suggest that temporal variability in indoor air TCE concentrations is greatest (modeled and measured) due to the existence of a land drain, which acts as a preferential pathway, from the subsurface to the granular fill beneath the floor slab. The field data and modeling results are in good agreement and provide a rare comparison of field data and modeling results for a VI site. The modeling approach presented here offers a useful tool for decision makers and VI practitioners as they assess these complex and variable processes that have not been incorporated within other VI models.

Key Design Elements of Building Pressure Cycling for Evaluating Vapor Intrusion-A Literature Review.

Building pressure cycling (BPC) is becoming an increasingly important tool for studying vapor intrusion. BPC has been used to distinguish subslab and indoor sources of vapor intrusion as well as to define reasonable worst case volatile organic compound mass discharge into a structure. Analyses have been performed both semi-quantitatively with concentration trends and quantitatively with more rigorous flux calculation and source attribution methods. This paper reviews and compares the protocols and outcomes from multiple published applications of this technology to define the key variables that control performance. Common lessons learned are identified, including those that help define the range of building size and type to which BPC is applicable. Differences in test protocols are discussed, recognizing that the complexity of the test protocol required depends on the particular objectives of each project. Research gaps are identified and tabulated for future validation studies and applications.