Environmental Science: Processes & Impacts最新文献

Per and polyfluoroalkyl substances (PFAS) are ubiquitous in the indoor environment, resulting in indoor exposure. However, a dearth of concurrent indoor multi-compartment PFAS measurements, including air, has limited our understanding of the contributions of each exposure pathway to residential PFAS exposure. As part of the Indoor PFAS Assessment (IPA) Campaign, we measured 35 neutral and ionic PFAS in air, settled dust, drinking water, clothing, and on surfaces in 11 North Carolina homes. Ionic and neutral PFAS measurements reported previously and ionic PFAS measurements reported herein for drinking water (1.4-34.1 ng L^-1), dust (202-1036 ng g^-1), and surfaces (4.1 × 10^-4-1.7 × 10^-2 ng cm^-2) were used to conduct a residential indoor PFAS exposure assessment. We considered inhalation of air, ingestion of drinking water and dust, mouthing of clothing (children only), and transdermal uptake from contact with dust, air, and surfaces. Average intake rates were estimated to be 3.6 ng kg^-1 per day (adults) and 12.4 ng kg^-1 per day (2 year-old), with neutral PFAS contributing over 80% total PFAS intake. Excluding dietary ingestion, which was not measured, inhalation contributed over 65% of PFAS intake and was dominated by neutral PFAS because fluorotelomer alcohol (FTOH) concentrations in air were several orders of magnitude greater than ionic PFAS concentrations. Perfluorooctanoic acid (PFOA) intake was 6.1 × 10^-2 ng kg^-1 per day (adults) and 1.5 × 10^-1 ng kg^-1 per day (2 year-old), and biotransformation of 8 : 2 FTOH to PFOA increased this PFOA body burden by 14% (adults) and 17% (2 year-old), suggesting inhalation may also be a meaningful contributor to ionic PFAS exposure through biotransformation.

Dissolved organic matter (DOM) released from biochar may impact antibiotic mobility and environmental fate in subsurface environments. Here, DOM samples derived from biochars (BDOM) generated by pyrolyzing corn straw at 300, 450, and 600 °C were employed to elucidate the mobility characteristics of these organic substances and their influences on the transport of sulfamerazine (SMZ, a typical sulfonamide antibiotic) in soil porous media. The results demonstrated that BDOM produced at a lower pyrolysis temperature exhibited greater mobility owing to the weaker hydrophobic and H-bonding interactions between BDOM and soil particles. Additionally and importantly, BDOM facilitated the promotion of SMZ mobility owing to the increased electrostatic repulsion between SMZ^- forms and soil grains, the steric hindrance effect induced by the deposition of organic matter, and the competitive retention between SMZ molecules and BDOM. Meanwhile, the promotion effects of BDOM enhanced with improving pyrolysis temperature owing to the promoted deposition of organic matter on soil surfaces and the strengthened electrostatic repulsion. Moreover, the facilitated effects of BDOM on SMZ mobility declined as the solution pH values were raised from 5.0 to 9.0 or the flow rate increased from 0.18 to 0.51 cm min^-1. This trend was due to decreased deposition competition and the steric effect caused by decreased retention of BDOM on soil particles. Furthermore, the cation-bridging effect emerged as an important mechanism contributing to the promotion effects of BDOM when the solution contained divalent cations (Cu²⁺ or Ca²⁺). Moreover, a two-site non-equilibrium model was used to interpret the controlling mechanisms for the effects of BDOM on the transport of SMZ. Findings from this work highlight that biochar-derived dissolved organic matter can remarkably affect the environmental behaviors of antibiotics in aquatic environments.

Multiphase interactions and chemical reactions at indoor surfaces are of particular importance due to their impact on air quality in indoor environments with high surface to volume ratios. Kinetic multilayer models are a powerful tool to simulate various gas-surface interactions including partitioning, diffusion and multiphase chemistry of indoor compounds by treating mass transport and chemical reactions in a number of model layers in the gas and condensed phases with a flux-based approach. We have developed a series of kinetic multilayer models that have been applied to describe multiphase chemistry and interactions indoors. They include the K2-SURF model treating the reversible adsorption of volatile organic compounds on surfaces, the KM-BL model treating diffusion through an indoor surface boundary layer, the KM-FILM model treating organic film formation by multi-layer adsorption and film growth by absorption of indoor compounds, and the KM-SUB-Skin-Clothing model treating reactions of ozone with skin lipids in skin and clothing. We also developed the effective mass accommodation coefficient that can treat surface partitioning by effectively taking into account kinetic limitations of bulk diffusion. In this study we provide detailed instructions and code annotations of these models for the model user. Example sensitivity simulations that investigate the impact of input parameters are presented to help with familiarization to the codes. The user can adapt the codes as required to model experimental and indoor field campaign measurements, can use the codes to gain insights into important reactions and processes, and can extrapolate to new conditions that may not be accessible by measurements.

Lack of water quality data for private drinking water sources prevents robust evaluation of exposure risk for communities co-located with historically contaminated sites and ongoing industrial activity. Areas of the Appalachian region of the United States (i.e., Pennsylvania, Ohio and West Virginia) contain extensive hydraulic fracturing activity, as well as other extractive and industrial technologies, in close proximity to communities reliant on private drinking water sources, creating concern over potential groundwater contamination. In this study, we characterized volatile organic compound (VOC) occurrence at 307 private groundwater well sites within Pennsylvania, Ohio, and West Virginia. The majority (97%) of water samples contained at least one VOC, while the average number of VOCs detected at a given site was 5 ± 3. The majority of individual VOC concentrations fell below applicable U.S. Environmental Protection Agency (EPA) Maximum Contamination Levels (MCLs), except for chloroform (MCL of 80 μg L^-1; n = 1 at 98 μg L^-1), 1,2-dibromoethane (MCL of 0.05 μg L^-1; n = 3 ranging from 0.05 to 0.35 μg L^-1), and 1,2-dibromo-3-chloropropane (MCL of 0.2 μg L^-1; n = 7 ranging from 0.20 to 0.58 μg L^-1). To evaluate well susceptibility to VOCs from industrial activity, distance to hydraulic fracturing site was used to assess correlations with contaminant occurrences. Proximity to closest hydraulic fracturing well-site revealed no statistically significant linear relationships with either individual VOC concentrations, or frequency of VOC detections. Evaluation of other known industrial contamination sites (e.g., US EPA Superfund sites) revealed elevated levels of three VOCs (chloroform, toluene, benzene) in groundwaters within 10 km of those Superfund sites in West Virginia and Ohio, illuminating possible point source influence. Lack of correlation between VOC concentrations and proximity to specific point sources indicates complex geochemical processes governing trace VOC contamination of private drinking water sources. While individual concentrations of VOCs fell well below recommended human health levels, the low dose exposure to multiple VOCs occurring in drinking supplies for Appalachian communities was noted, highlighting the importance of groundwater well monitoring.

The historical use and storage of aqueous film-forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) at a range of sites including airports, defence, and port facilities have resulted in a legacy of contaminated infrastructure such as concrete. Contaminated concrete constitutes an ongoing source of PFAS contamination requiring management to ensure the protection of human health and the environment. In this study, modified Leaching Environmental Assessment Framework (LEAF) and Australian Standard Leaching Procedure (ASLP) were used to examine the leachability of PFAS, specifically, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS) and perfluorohexanoic acid (PFHxA) from AFFF-contaminated concrete collected from an Australian Defence Fire Training Area (FTA). In general, PFAS readily leached from intact contaminated concrete monoliths with the cumulative proportion (%) decreasing in the order: PFHxA (>95%) > PFOS (26-84%) ≈ PFHxS (14-78%) > PFOA (<1-54%). Higher leachability for PFHxA from concrete is consistent with previous findings for solids, however, inconsistent for PFOA with higher retention (lower leachability) in concrete as compared to PFOS. Duration of exposure to water (0.5-48 h) and temperature (25 °C and 50 °C) had little influence on the proportion of PFAS leachability from powdered concrete. A higher proportion of PFAS leached from a <2 mm concrete powder size fraction as compared to 2-20 mm and 20 mm size fractions. This behavior reflects an increase in surface area with decreasing concrete particle size. Reducing the particle size could enhance PFAS removal from waste concrete.

Millions of tons of coal fly ashes (CFAs) are produced annually during coal combustion in the U.S., which are commonly beneficially used in the concrete industry or disposed of in ash ponds. CFAs contain trace amounts of a range of toxic heavy metals including selenium (Se). Because the toxicity of Se is dependent on its speciation, investigating Se speciation in CFAs as affected by coal source and combustion conditions can help understand the related environmental and human health impacts during disposal or beneficial reuse. In this study, a set of representative CFA samples were characterized for Se speciation using synchrotron X-ray absorption spectroscopy (XAS) and micro-X-ray fluorescence spectromicroscopy (μ-XRF/XAS). Se-containing particles were highly heterogeneous, and individual particles might contain multiple oxidation states including Se(0), Se(IV), and Se(VI). Principal component analysis was performed for sample characteristics including Al₂O₃, SiO₂, CaO, FeO, loss on ignition, average particle size, Se concentration, and Se oxidation state. Selective catalytic reduction (SCR), which is used to limit nitrogen oxide (NO_x) emissions during coal combustion, was found to be associated with the presence of reduced Se oxidation states, with up to 90% Se(0) observed in samples with SCR. Alongside SCR, FeO content may also influence Se speciation.

Open dumping and burning of solid waste are widely practiced in underserved communities lacking access to solid waste management facilities; however, the generation of microplastics from these sites has been overlooked. We report elevated concentrations of microplastics (MPs) in soil of three solid waste open dump and burn sites: a single-family site in Tuttle, Oklahoma, USA, and two community-wide sites in Crow Agency and Lodge Grass, Montana, USA. We extracted, quantified, and characterized MPs from two soil depths (0-9 cm and 9-18 cm). The average of abundance of particles found at community-wide sites three sites (18, 460 particles kg^-1 soil) equals or exceeds reported concentrations from currently understood sources of MPs including biosolids application and other agricultural practices. Attenuated total reflectance Fourier transformed infrared (ATR-FTIR) identified polyethylene as the dominant polymer across all sites (46.2-84.8%). We also detected rayon (≤11.5%), polystyrene (up to 11.5%), polyethylene terephthalate (≤5.1), polyvinyl chloride (≤4.4%), polyester (≤3.1), and acrylic (≤2.2%). Burned MPs accounted for 76.3 to 96.9% of the MPs found in both community wide dumping sites. These results indicate that solid waste dumping and burning activities are a major source of thermally oxidized MPs for the surrounding terrestrial environment with potential to negatively affect underserved communities.

Ecosystem services play an essential role as intermediaries, linking natural ecosystem resources to socio-economic demands. Understanding their impact on ecological well-being is pivotal for ensuring regional environmental security and promoting sustainable societal and economic development. However, there is insufficient research on the relationship between the two. Accordingly, this study explores the evolutionary relationship between ecological health and ecosystem services by constructing an evaluation system. Regression analysis is used to explore the spatial relationship between ecosystem services and ecological health, providing a reference for maintaining the balance between ecological supply and ecological health. The results show that from 1980 to 2020, an overall improvement was observed in the eco-health index of the Yangtze River Economic Belt's. This improvement was notably marked by substantial growth in the eco-vitality index alongside consistent maintenance of the spatial distribution within the eco-organization index. With regard to distributions of specific ecosystem services, dispersed occurrences characterized areas with high water production and crop yield levels; however, within forested regions, attributes for habitat quality preservation, water purification, soil retention and carbon sequestration were predominant. In the impact of ecosystem services on ecological health, food production held sway over less-developed areas, while soil conservation, water supply and habitat quality exerted greater influence over more-developed regions. This study regards ecosystem services as a bridge connecting humans and the environment not only providing a material basis for society but also reflecting the status of ecological health.

The Bioconcentration Factor (BCF) is used to evaluate the bioaccumulation potential of chemical substances in reference organisms, and it directly correlates with ecotoxicity. Traditional in vivo BCF estimation methods are costly, time-consuming, and involve animal sacrifice. Many in silico technologies are used to avoid the problems associated with in vivo testing. This study aims to develop a quantitative read across structure-property relationship (q-RASPR) model using a structurally diverse dataset consisting of 1303 compounds by combining quantitative structure-property relationship (QSPR) and read-across (RA) algorithms. The model incorporates simple, interpretable, and reproducible 2D molecular descriptors along with RASAR descriptors. The PLS-based q-RASPR model demonstrated robust performance with internal validation metrics (R² = 0.727 and Q²_(LOO) = 0.723) and external validation metrics (Q²_F1 = 0.739, Q²_F2 = 0.739, and CCC = 0.858). These results indicate that the q-RASPR model is statistically superior to the corresponding QSPR model. Furthermore, screening of 1694 compounds from the Pesticide Properties Database (PPDB) was performed using the PLS-based q-RASPR model for assessing the eco-toxicological bioaccumulative potential of various compounds, ensuring the external predictability of the developed model and confirming the real-world application of the developed model. This model offers a reliable tool for predicting the BCF of new or untested compounds, thereby helping to develop safe and environment-friendly chemicals.

Gas-phase reactive nitrogen species (N_r) are important drivers of indoor air quality. Cooking and cleaning are significant direct sources indoors, whose emissions will vary depending on activity and materials used. Commercial kitchens experience regular high volumes of both cooking and cleaning, making them ideal study locations for exploring emission factors from these sources. Here, we present a total N_r (tN_r) budget and contributions of key species NO, NO₂, acidic N_r (primarily HONO) and basic N_r (primarily NH₃) using novel instrumentation in a commercial kitchen over a two-week period. In general, highest tN_r was observed in the morning and driven compositionally by NO, indicative of cooking events in the kitchen. The observed HONO and basic N_r levels were unexpectedly stable throughout the day, despite the dynamic and high air change rate in the kitchen. After summing the measured NO_x, HONO and N_r,base fractions, there was on average 5 ppbv of N_r unaccounted for, expected to be dominated by neutral N_r species. Using co-located measurements from a proton transfer reaction mass spectrometer (PTR-MS), we propose the identities for these major N_r species from cooking and cleaning that contributed to N_r,base and the neutral fraction of tN_r. When focused specifically on cooking events in the kitchen, a vast array of N-containing species was observed by the PTR-MS. Reproducibly, oxygenated N-containing class ions (C_1-12H_3-24O_1-4N_1-3), consistent with the known formulae of amides, were observed during meat cooking and may be good cooking tracers. During cleaning, an unexpectedly high level of chloramines was observed, with monochloramine dominating the profile, as emitted directly from HOCl based cleaners or through surface reactions with reduced-N species. For many species within the tN_r budget, including HONO, acetonitrile and basic N_r species, we observed stable levels day and night despite the high air change rate during the day (>27 h^-1). The stable levels for these species point to large surface reservoirs which act as a significant indoor source, that will be transported outdoors with ventilation.