Environmental Science: Processes & Impacts最新文献

In shallow lakes, mobilization of legacy phosphorus (P) from the sediments can be the main cause for persisting eutrophication after reduction of external P input. In-lake remediation measures can be applied to reduce internal P loading and to achieve ecosystem recovery. The eutrophic shallow peat lake Terra Nova (The Netherlands) was treated with iron (Fe) to enhance P retention in the sediment. This treatment, however, intensified seasonal internal P loading. An earlier study suggested that Fe addition led to increased P binding by easily-reducible Fe(III) associated with organic matter (OM), which readily releases P when bottom waters turn hypoxic. In this complementary study, bulk and micro Fe K-edge and P K-edge X-ray absorption spectroscopy and micro-focused X-ray fluorescence spectroscopy were applied to characterize the P hosting Fe(III) pool. Combined with sequential extraction data, the synchrotron X-ray analyses revealed that a continuum of co-precipitates of Fe(III) with calcium, phosphate, manganese and organic carbon within the OM matrix constitutes the reducible Fe(III) pool. The complementary analyses also shed new light on the interpretation of sequential extraction results, demonstrating that pyrite was not quantitatively extracted by nitric acid (HNO₃) and that most of the Fe(II) extracted by hydrochloric acid (HCl) originated from phyllosilicate minerals. Formation of an amorphous inorganic–organic co-precipitate upon Fe addition constitutes an effective P sink in the studied peaty sediments. However, the high intrinsic reactivity of this nanoscale co-precipitate and its fine distribution in the OM matrix makes it very susceptible to reductive dissolution, leading to P remobilization under reducing conditions.

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.

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.

This study uses mobile monitoring to gain a better understanding of particulate matter (PM) sources in two areas of Central and Outer London, UK. We find that, unlike emissions of nitrogen oxides (NO + NO₂ = NO_x), which are elevated in Central London due to the high number of diesel vehicles and congestion, fine particulate matter (PM_2.5) emissions are well-controlled. This finding provides evidence for the effectiveness of vehicle particulate filters, supporting the view that their widespread adoption has mitigated PM_2.5 emissions, even in the highly dieselized area of Central London. However, mobile monitoring also reveals infrequent elevated PM_2.5 concentrations caused by malfunctioning vehicles. These events were confirmed through simultaneous measurements of PM_2.5 and sulfur dioxide (SO₂), the latter being a strong tracer of engine lubricant combustion. A single event from a gasoline car, representing just 0.15% of the driving distance in Outer London, was responsible for 7.4% of the ΔPM_2.5 concentration above background levels, highlighting the ongoing importance of addressing high-emission vehicles. In a novel application of mobile monitoring, we demonstrate the ability to identify and quantify non-vehicular sources of PM. Among the sources unambiguously identified are construction activities, which result in elevated concentrations of coarse particulate matter (PM_coarse = PM₁₀ − PM_2.5). The mobile measurements clearly highlight the spatial extent of the influence of such sources, which would otherwise be difficult to determine. Furthermore, these sources are shown to be weather-dependent, with PM_coarse concentrations reduced by 62.1% during wet conditions compared to dry ones.

Isocyanates are well-known irritants and sensitizers, and measuring their occupational airborne exposure is challenging due to their high chemical reactivity and semi-volatile nature. This study builds on a previous publication by our team that focused on comparing evaluation methods for isocyanates. The current research aims at developing, validating, and applying a laboratory generation system designed to replicate real-world conditions for spraying clear coats in autobody shops using hexamethylene diisocyanate (HDI)-based products. The system involved a spray gun connected to two chambers in series, enabling sample collection and analysis. The system successfully generated HDI and isocyanurate concentrations ranging from 0.008 to 0.040 mg m⁻³ and 0.351 to 3.45 mg m⁻³, respectively, with spatial homogeneity (RSD) of 5.8% and 16.5%. The particle-size distribution (MMAD) of 4 μm was measured using a cascade impactor and an electrical low-pressure impactor. The samples generated were used to correlate the amount of isocyanates collected with scanning electron microscope images of droplets on a filter. Three methods were compared to the reference method—an impinger with a backup glass fibre filter (GFF) and 1,2-methoxyphenylpiperazine (MP) based on ISO 16702/MDHS 25—in six generation experiments: (1) Swinnex cassette 13 mm GFF MP (MP-Swin); (2) closed-face cassette 37 mm GFF (end filter and inner walls) MP (MP-37); and (3) denuder and GFF dibutylamine (DBA) (ISO 17334-1 Asset). The analysis revealed clear trends regarding which sampler sections collected HDI (mainly in the vapor phase) or isocyanurate (exclusively in the particulate phase). The study found no significant bias between the tested methods (MP-Swin, MP-37, and Asset) and the reference method (impinger) for both HDI monomer and isocyanurate. The three tested methods showed limits of agreement beyond the acceptable range of ±30% (95% confidence interval), largely due to data variability, though MP-Swin and MP-37 exhibited lower variability than Asset. The results will be further evaluated in a real-world environment where similar clear coats are used.

Quantifying source contributions to indoor PM_2.5 levels by indoor PM_2.5 sources has been limited by the costs associated with chemical speciation analyses of indoor PM_2.5 samples. Here, we propose a new methodology to estimate this contribution. We applied FUzzy SpatioTemporal Apportionment (FUSTA) to a database of indoor and outdoor PM_2.5 concentrations in school classrooms plus surface meteorological data to determine the main spatiotemporal patterns (STPs) of PM_2.5. We found four dominant STPs in outdoor PM_2.5, and we denoted them as regional, overnight mix, traffic, and secondary PM_2.5. For indoor PM_2.5, we found the same four outdoor STPs plus another STP with a distinctive temporal evolution characteristic of indoor-generated PM_2.5. Concentration peaks were evident for this indoor STP due to children's activities and classroom housekeeping, and there were minimum contributions on sundays when schools were closed. The average indoor-generated estimated contribution to PM_2.5 was 5.7 μg m⁻³, which contributed to 17% of the total PM_2.5, and if we consider only school hours, the respective figures are 8.1 μg m⁻³ and 22%. A cluster-wise indoor–outdoor PM_2.5 regression was applied to estimate STP-specific infiltration factors (F_inf) per school. The median and interquartile range (IQR) values for F_inf are 0.83 [0.7–0.89], 0.76 [0.68–0.84], 0.72 [0.64–0.81], and 0.7 [0.62–0.9], for overnight mix, secondary, traffic, and regional sources, respectively. This cost-effective methodology can identify the indoor-generated contributions to indoor PM_2.5, including their temporal variability.

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.

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.