Environmental Science: Processes & Impacts最新文献

Chemical emission rates and mode-of-release (MOR; distribution of emissions across compartments) are key processes relating to exposures and potential environmental impacts and are often the most uncertain input parameters for mass balance multimedia environmental fate and exposure models. Three independent methods of estimating emission rate and MOR including generic scenarios, expert judgment, and a high-throughput mass-flow tool, are used to calculate exposure concentrations and margins of exposure (MOEs) for select cyclic volatile methyl siloxanes (cVMS): octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6). The same chemical properties and hazard data are used as model input in the methods comparison. The MOR for cVMS has a large impact on estimated exposure levels and MOE for aquatic species; exposure estimates varied by up to seven orders of magnitude, depending solely on MOR assumptions, with even small fractions released to water substantially increasing aquatic exposure. Exposure model predictions using a high-throughput emission estimation tool, use category estimates, and regional production volume information including mechanistic modelling of their release due to their use in personal care products show reasonable agreement with spatially and temporally curated (bio)monitoring data (n = 85). MOEs are ∼10¹ to 10⁸ when calculated for the biomonitoring data and the high-throughput emission estimation and exposure models. Additional methods for addressing uncertainty in emission rates are outlined. The results demonstrate that mechanistic emission modelling can help address uncertainty in chemical emission rate estimates and inform decision-making for chemical safety and sustainability.

Surface properties impact indoor gas-surface interactions and thus indoor air quality. Specific surface area impacts sorption capacity, while pores increase diffusion and storage in the bulk material. We measured roughness, porosity, and specific surface area of eleven common indoor surfaces and calculate the sorption capacity of an authentic office space. The specific surface area of the office is four orders of magnitude greater than the geometric surface area typically considered in indoor studies. Paint decreases the specific surface area for wood and drywall. Due to the substantial sorption capacity, surface films may be patchworks of organic and water-rich layers instead of spatially-ubiquitous, multilayer organic films on top of all indoor surfaces. The pores within surfaces can enhance diffusion resulting in different bulk diffusion equilibration timescales for different surfaces with ceiling tile, carpet and wood require longer timescales (up to years) to equilibrate. Thus, easily cleaned dust and surface films can increase short-term uptake of gas-phase contaminants then be removed to reduce re-emission; however, those contaminants may still penetrate deeper into the indoor building material that cannot be removed by surface cleaning. More solid surfaces with lower sorption capacity and longer diffusive timescales improve air quality in the long term by decreasing the gas-phase contaminants stored on surfaces that can be later re-emitted. Our results imply that building material selection may decrease long-term exposure to wildfire smoke or other air pollutants.

Freshwater ecosystems are increasingly threatened by land-use changes associated with agricultural and urban development. Comprehensive assessments of water quality are necessary to understand their status and implement appropriate measures for its protection and conservation. The present study evaluated the water quality of two streams from Ramallo, Buenos Aires, Argentina (Las Hermanas and Marconi streams) with point (agroindustrial) and non-point sources of pollution through the analysis of landscape structure and anthropogenic transformations, physicochemical parameters, metal and pesticide quantification, and lethal toxicity bioassays and biomarkers (oxidative stress and cholinesterase activity biomarkers) using Rhinella arenarum larvae. Dissolved oxygen levels were below the threshold established for the protection of aquatic life at most sites, whereas ammonia, Mn, Cu, and Zn concentrations exceeded the limits for protection of aquatic life (Argentine Law 24 051). In sediment samples, several metals that were not detected in the water samples were quantified. Herbicides were the predominant pesticide class detected, with the site downstream of a feedlot showing the greatest variety. In addition, a higher diversity of pesticide residues was observed in water samples compared to sediments. Mainly, atrazine (0.125-1.193 µg L^-1), flurochloridone (0.218-0.452 µg L^-1), AMPA (0.27-1.16 µg L^-1), and glyphosate (0.28-0.48 µg L^-1) were quantified in water samples. Significant larval mortality was observed after acute exposure times, especially at Las Hermanas stream. Also, alterations in the oxidative stress biomarkers and cholinesterase inhibition were observed in larvae exposed to water samples from both sites located at Las Hermanas stream. Overall, sites with a higher proportion of cultivated land, feedlots, and agricultural buildings, together with a lower proportion of wetlands, exhibited poorer water quality and greater environmental degradation, which coincided with stronger ecotoxicological responses. These findings highlight the value of integrating landscape metrics, water quality, and ecotoxicological responses to comprehensively assess environmental degradation in freshwater ecosystems.

Spontaneous coal combustion (SCC) occurs globally and releases particulate matter, acid gases (e.g., SO₂ and NO_x), and metals into the environment. This study characterizes nanometer-scale processes that occur during and after SCC in Urussanga, Santa Catarina, Brazil. A multi-analytical approach using various surface- and electron-microscopy techniques allowed the identification of secondary mineral processes and the formation of secondary minerals. Weathering of thermally altered pyrite and coal rejects forms secondary weathering crusts composed predominantly of Fe-oxides (hematite and spinel-group minerals), amorphous silica, clay minerals (illite-smectite, I-S, and kaolinite), sulfides (pyrite), and sulfates (gypsum and jarosite-alunite group minerals). The crusts are enriched in metals common in pyrite, form efflorescent minerals, or show high structural compatibility with Fe-oxides. Pyrite transforms into pyrrhotite, mikasaite, Fe₂(SO₄)₃, and hematite under different O₂ and hydrocarbon activities. Porous coal matrices allowed inferred meteoric water to infiltrate pyrite-coal-clay mineral associations. This promoted the non-stoichiometric dissolution of I-S into amorphous silica and the weathering of pyrite to nanometer-thick secondary Fe-sulfate layers in confined pore spaces along pyrite-coal interfaces. The high abundance of clay minerals and amorphous silica resulted in the entrapment/armoring of pyrite-, TiO₂-, and jarosite-alunite nanoparticles and the heterogeneous nucleation of jarosite on the (001) basal surface of kaolinite. These findings indicate complex interactions between the original minerals in coal rejects (pyrite and I-S), thermal alteration products (pyrrhotite, mikasaite, and TiO₂), and post-combustion weathering products (amorphous silica, Fe-sulfates and -(hydr)oxides), as well as the geochemical redistribution of environmentally significant elements during and after SCC.

Gas transfer across river interfaces remains a poorly quantified process in the Earth's carbon cycle. Standard frameworks overlook how turbulence, biofilm impedance, and suspended sediment interact. We propose a mechanistic k model integrating (i) turbulence-driven transfer via the O'Connor & Dobbins formulation, (ii) biofilm suppression as a power-law function of thickness (δ), (iii) sediment suppression as an exponential function of suspended sediment concentration (C_sed), and (iv) diurnal inhibition of k(Δk_photo). We apply this model to the Damodar River, India-a regulated, eutrophic tropical system. Field measurements (SF₆ tracer injections, floating chambers, micro-profiling, ADCP surveys) reveal that biofilms suppress k by 18-37% in dry-season low-flow reaches (δ = 1.2-3.0 mm), while suspended sediments dominate monsoon fluxes, reducing k by 22-29% at estimated C_sed of 300-850 mg L^-1. The model captures observed spatial and seasonal patterns with RMSE = 1.82 cm h^-1 and NSE = 0.64, outperforming conventional formulations (O'Connor and Dobbins, NSE = 0.42; Raymond et al., NSE = 0.45). Because sediment concentrations were estimated from published post-dam baselines, we report results as a sensitivity analysis across plausible C_sed ranges. These findings highlight the need to incorporate biofilm-sediment interactions into gas flux models, particularly in anthropogenically altered rivers.

Coal combustion generates large volumes of mineral residues containing naturally occurring radioactive materials (NORM), whose radiological characteristics vary systematically with plant operational scale and fuel properties. Understanding the factors governing this variability is essential for radiological risk assessment and sustainable management of coal combustion residues. This study investigates the capacity-associated variability of radionuclide activity concentrations (²²⁶Ra, ²³²Th, ⁴⁰K) in coal combustion slag using a dataset of 251 samples collected from 18 Polish power plants with capacities ranging from 51 to 5091 MW. Gamma spectrometry and multivariate statistical methods, including K-means clustering and PERMANOVA, were applied to identify patterns in radionuclide distribution and their relationship to plant scale as a proxy for facility-scale operational categories. Three distinct clusters were identified, revealing a non-linear relationship between plant capacity and radionuclide concentrations. Slag from medium-capacity plants exhibited the highest activity levels and radiological hazard indices, indicating that plant-scale factors are associated with systematically elevated radionuclide activity concentrations in slag. In contrast, high-capacity plants showed more stable and moderate radiological profiles, while low-capacity units exhibited greater variability linked to fuel characteristics and combustion efficiency. Radiological risk assessment based on radium equivalent activity, activity index, and indoor dose indicators demonstrated that a subset of slag materials may exceed commonly applied screening levels, particularly within the medium-capacity cluster. These findings highlight the importance of incorporating plant-scale operational factors into the radiological risk evaluation of coal combustion residues. The results demonstrate that naturally occurring radionuclides serve as effective indicators of capacity-associated variability in slag radiological composition, while also providing a basis for risk-informed management of coal-derived waste. Integrating plant-scale parameters with radiological assessment offers a practical framework for supporting environmental regulation and sustainable reuse strategies.

Tripolyphosphate (TPP) is a short-chain polyphosphate (polyP) that enters aquatic systems through industrial and consumer applications, yet the kinetics of its abiotic hydrolysis in the presence of dissolved metal cations remain poorly quantified. This study systematically investigates the hydrolysis of TPP in the presence of common cations. The results demonstrate that dissolved cations promoted TPP hydrolysis in a concentration- and pH-dependent manner. At pH 6, the promoting effect decreased in the order Cu²⁺ > Al³⁺ > Zn²⁺ > Ca²⁺ > Mn²⁺ > Mg²⁺, a trend that directly correlates with the stability constants of the corresponding metal-TPP complexes, supporting a Lewis-acid-type promotion mechanism. Apparent rates increased with metal dose, whereas ionic strength had no effect, and excess EDTA suppressed the reaction to the metal-free background, indicating that metal-TPP association, rather than outer-sphere electrostatics, governs the rate. Time-resolved ³¹P NMR spectroscopy resolved the sequential conversion of TPP to pyrophosphate and then orthophosphate, consistent with exo-cleavage. Regression of the apparent rate constants on cation descriptors across the full pH grid (pH 4-8; n = 18) linked the activity ranking to metal electronegativity (partial Spearman ρ = 0.74, p < 0.001, controlling for pH), interpreted as statistical consistency with Lewis-acid promotion. Extrapolation of the dose-response data to realistic dissolved metal concentrations indicates that this pathway is unlikely to dominate polyP turnover in pristine waters but may be relevant in metal-rich, particle-poor systems. This work provides an internally consistent kinetic baseline and mechanistic constraints for cation-promoted abiotic hydrolysis of short-chain polyphosphate.

Lightning is a dominant free tropospheric source of nitrogen oxides (NO_x), impacting climate by affecting global tropospheric ozone (O₃) and other key oxidants. We calculate temporally and spatially resolved lightning NO_x (LNO_x) production rates using lightning flash energies from space-based Lightning Imaging Sensors (LIS). Our production rates average ∼309 moles per flash (mol fl^-1) over oceans, peaking at midday, and ∼172 mol fl^-1 over land, peaking in the early morning. Replacing static values in the original GEOS-Chem model inventory with our spatially and hourly varying production rates yields global annual LNO_x emissions of 4.4 Tg nitrogen (N) for 2015-2019; almost 2 Tg N less than the original inventory. Annual terrestrial LNO_x emissions still exceed those over the ocean, due to more frequent lightning over land, but the relative proportion of maritime emissions increases. The largest decline in LNO_x emissions is north of 35°N in summer, as static 500 mol fl^-1 is replaced with 150-250 mol fl^-1. Global decline in LNO_x emissions decreases abundances of free tropospheric NO_x, O₃, the hydroxyl radical (OH) and peroxyacetyl nitrate (PAN). Hourly variability in LIS flash radiances is broadly consistent with high-frequency Geostationary Lightning Mapper (GLM) flash energies, though the comparison is limited to tropical America. Introducing hourly variability in LNO_x production rates leads to a greater than 10% localised decline in equatorial lower tropospheric O₃. Independent validation is critically needed, given our updated LNO_x emissions offer a viable solution to model overestimates in O₃ and OH and underestimates in the lifetime of the greenhouse gas methane.

Denitrification is a key microbial process in nitrogen cycling and a major source of N₂O emissions from agricultural soils. In this study, we investigated denitrification rates and their intrinsic controls across four contrasting agricultural soils from China (black, yellow loessal, purple, and red soils) using anaerobic microcosm incubations with the acetylene inhibition method. Denitrification rate constants were derived from a pseudo-first-order kinetic model. Microbial community composition and the abundance of denitrification functional genes (narG, napA, nirK, nirS, norB, and nosZ) were characterized using 16S rRNA gene sequencing and quantitative polymerase chain reaction (qPCR), respectively. Denitrification rate constants differed significantly among soils, decreasing from 12.0 ± 1.3 to 0.1 ± 0.1 d^-1 in the order black > yellow loessal > purple > red. Soil type explained 92.1% of the variation in bacterial community composition (PERMANOVA, p < 0.001), demonstrating pronounced soil-specific microbial assemblages. Soil physicochemical properties, especially pH, soil organic carbon (SOC), and cation exchange capacity (CEC), were strongly associated with microbial community structure and denitrification potential. Microbial diversity correlated positively with denitrification rates, and norB abundance closely tracked differences in denitrification activity across soils. However, functional gene abundance did not always correspond to the microbial structure or denitrification rates, as illustrated by the high abundance but non-significant relationship of narG with denitrification rate constants. Together, these results highlight the integrated roles of intrinsic soil properties, microbial community characteristics, and functional potential in explaining denitrification variability among soils. By providing a quantitative baseline, this study offers a reference framework for future investigations assessing how external environmental disturbances may alter soil nitrogen cycling.

Biochar-associated persistent free radicals (PFRs) can directly induce oxidative damage in plants. However, this toxic mechanism may not be fully applicable to plants growing in a real soil ecosystem considering the complexity of the soil environment. In this study, biochar was applied to soil at rates ranging from 0 to 20 g kg^-1, and wheat growth was inhibited at 20 g kg^-1, but did not at 1-10 g kg^-1. Notably, inhibitor and sterilization experiments indicated that PFRs and their derived hydroxyl radical (˙OH) were the primary factors inhibiting wheat growth, and wheat damage degree primarily depended on the impact of free radicals on rhizosphere microbes rather than direct damage to wheat itself. Integrated analyses of enzymatic stoichiometry, microbial community structure, and transcriptomic profiles analysis further revealed that at 20 g kg^-1 dosage, PFRs and ˙OH aggravated microbial C and P limitations, prompting rhizosphere microbes to preferentially allocate metabolic energy for alleviating nutrient limitations. This reduces the abundance of disease-suppressive bacteria (e.g., Actinobacteria, Gemmatimonadetes, and Nitrospirae) and bacterial α-diversity, ultimately increasing wheat susceptibility to free radical stress. By contrast, free radicals did not induce stoichiometric imbalance at 1-10 g kg^-1 dosage. Rhizosphere microbes could allocate more energy to activate the wheat defense system, including salicylic acid metabolism, L-phenylalanine metabolism, and the MAPK signaling pathway, thereby reducing free radical-induced damage to wheat. These findings highlight a previously overlooked mechanism of free radical-induced phytotoxicity, providing a foundation for developing improved biochar application strategies.