Environmental Science: Processes & Impacts最新文献

Uranium (U) is a natural radioactive metal and a persistent environmental pollutant. Characterising the influence of arbuscular mycorrhizal fungi (AMF) on U bioaccumulation and partitioning in plants is crucial to understand U soil-to-plant transfer mechanisms. High resolution elemental mapping, spectroscopy and microscopy techniques were conducted on uranyl nitrate dosed Plantago lanceolata roots colonised with Rhizophagus irregularis. U-rich particles accumulated within the root cells, with higher abundance in epidermal and outer cortex cells of mycorrhizal root samples than in non-mycorrhizal roots. Electron microscopy determined two different crystalline U phases, an acicular crystal and a novel rounded aggregate formation, the latter of which was only found within the mycorrhizal root cells. Multiple imaging and spectroscopic techniques enabled the dominant elements with these U biominerals to be determined. Co-localisation between U, phosphorus and oxygen indicated the dominance of U-phosphate biominerals, but metals including calcium and zinc were also found to co-localise. The most dominant U compound was uranyl orthophosphate, likely accompanied by autunite. This study demonstrates alteration in U localisation and U particle morphology within Plantago roots as a direct consequence of AMF colonisation. This knowledge will allow more accurate U food-chain transfer modelling and better assessment of AMF-assisted phytoremediation feasibility.

Occupational exposure to semi-volatile organic compounds (SVOCs) among various population groups has garnered insufficient attention. We investigated the occupational exposures of waste disposal workers and daily exposure of university students to phthalates (PAEs), organophosphate esters (OPEs), and polycyclic aromatic hydrocarbons (PAHs) using polydimethylsiloxane (PDMS)-based passive sampling combined with machine learning-driven serum concentration predictions. The SVOC exposures of students varied depending on their professional activities, e.g., experiments, but dormitories emerge as a significant source. The SVOC exposures among workers varied across different workshops with each acting as the dominant source. The exposure concentrations of PAEs, OPEs, and PAHs among workers were 2.24 times, 6.87 times, and 14.9 times higher than those among students, respectively, whereas the exposure of tris(2,4-di-tert-butylphenyl) phosphate (TDTBPP) among students was 37.8 times higher than that among workers. Sources of PAEs or PAHs for workers and students were relatively similar, while sources of OPEs exhibited greater complexity, especially for TDTBPP. Significant cancer risks were identified for waste disposal workers exposed to di(2-ethylhexyl) phthalate (DEHP), benzo[a]pyrene (BaP), and naphthalene (NAP), and for students subjected to DEHP. Machine learning prediction revealed that despite higher environmental exposures, the predicted serum concentrations of PAEs and OPEs among workers were generally comparable with those of male students but much higher than those of female students, while the predicted serum concentrations of PAHs were comparable across all groups. Risk assessments using Monte Carlo simulations indicated that without protective measures, 99.7% of workers and 55.0% students may face DEHP exposure risk. This emphasized the need for improved ventilation and reduced plasticizer use.

China is a global hotspot of nitrogen (N) emissions and N deposition, which has implications for the N dynamics of ecosystems and stimulates the production of nitrous oxide (N₂O). Although many studies have explored the contributions of different processes to N₂O emissions, it remains unclear whether N addition affects the relative contributions of these different processes to N₂O emissions. We conducted a meta-analysis from 55 published works and 3 unpublished datasets in terrestrial and coastal ecosystems of China to generalize information about the effects of N addition on N cycling, from genes to processes. On average, N addition increased nitrification, denitrification, and N₂O emission rates by 165%, 37%, and 160%, respectively. There was a significant increase in the abundances of nitrification-related genes (i.e., amoA) but a significant decrease in the abundances of denitrification-related genes (i.e., narG, nirS, nirK, and nosZ) after N addition. The variance of nitrification genes caused by N addition was the most important factor explaining increases of N₂O emissions. The N₂O emissions increased exponentially with the N addition rates while decreased with the duration of experiments. The responses of the N₂O emissions to N additions were 2.89 times and 1.3 times stronger in farmland and wetland ecosystems than those in forest and grassland ecosystems, respectively. Additionally, this effect was stronger in regions with high temperature and precipitation. Overall, our meta-analysis reveals the response of soil N cycling to N addition and suggests that N addition promotes N₂O emissions by enhancing nitrification; these findings have major implications for N fertilizer management in China.

Metagenomics is a powerful tool for investigating functional microorganisms, molecular mechanisms and genes involved in the degradation of polycyclic aromatic hydrocarbons (PAHs) in situ complex environments. In this study, we selected three land use types in the lower reaches of the Shiwuli River in Chaohu and applied metagenomics technology. The results revealed that Rhodoplanes and Bradyrhizobium were the abundant PAH-degrading microorganisms across the three land use types. Based on the functional annotation and PAH degradation pathway, it was found that the in situ microbial communities of the three land use types shared common metabolic pathways for phenanthrene degradation. In addition, a unique metabolic pathway for PAH degradation was identified in the agricultural land. Only Patulibacter contributed to flnE (KO14604) in the agricultural land, which was involved in the metabolic pathway of fluorene degradation. Results of this study suggested that the in situ degradation of PAHs was not completed by a single genus, and it involved the synergy effects of different PAH-degrading microorganisms. There was no significant difference between the compositions and relative abundances of PAH-degrading microorganisms in the three land use types and those presented in the Kyoto Encyclopedia of Genes and Genomes Orthology (KO). However, the same microorganism contributed to different functional genes in different samples. Genes encoding protocatechuic acid 4,5-dioxygenase were widely distributed and relatively abundant. Therefore, this gene may serve as an indicator of PAH degradation potential. Among all the factors, the total organic carbon and nitrate nitrogen contents exhibited significant influences on the functional genes (KO) related to PAH degradation (p < 0.05).

Cannabis cultivation and processing are emerging sources of air pollutants, particularly malodorous volatile organic compounds (VOCs), yet uncertainties remain regarding their emission rates and chemical composition. Emission rates are typically the starting point for an air quality assessment; not addressing their uncertainty and chemical profile may lead to under/over estimation of impacts. This study aims to quantify terpene emissions from indoor cannabis operations in the Lower Fraser Valley, BC, Canada a region already affected by odorous sources and peak ozone concentrations in the summer due to imbalance of VOC and nitrogen oxides (NO_x) emissions. We assessed terpene concentration variability across activities, and evaluated their potential odor impacts during peak summertime. For this, we developed an automated gas chromatography sampling and processing protocol to measure concentrations of 22 key cannabis terpenes in (1) eight rooms of an indoor cultivation facility and (2) six rooms of a processing and extraction facility. Emission rates varied widely, ranging from 1.05 × 10^-3 to 3.09 × 10^-1 kg h^-1, with the highest emissions occurring during trimming (i.e., buds' extraction). We observed substantial temporal variability; individual terpene concentrations fluctuated by up to 1500% depending on activity type and lighting conditions. Pearson correlation analysis revealed non-linear relationships between individual terpenes and total emissions, suggesting shifts in chemical composition during peak emissions. To assess odor implications, we conducted screening dispersion modeling for β-myrcene, a terpene considered a tracer of cannabis emissions. Of the 7560 dispersion scenarios evaluated, 88 exceeded the odor threshold under average emissions, increasing to 241 scenarios during peak trimming emissions. Because emission rates and chemical compositions vary significantly depending on activity type and conditions, and dispersion modeling results showed that average conditions are sufficient to cause odor episodes, it is important to characterize both the temporal and chemical profiles of terpene emissions in cannabis facilities to avoid mis-estimating their air pollution and odor impact. Given the growing industry and the potential for odor complaints and secondary air pollution impacts (e.g., ozone formation), it is crucial to understand these emissions in detail. Policymakers, scientists, and industry stakeholders can use our findings to develop better mitigation strategies and inform environmental regulations.

The health impacts of aerosols from southwestern China remain poorly understood. To identify the key chemical contributors and sources of PM_2.5 toxicity in this region, detailed chemical composition (carbonaceous and inorganic species), different air volume normalized acellular oxidative potential (OP) metrics (OPDTTV and OPEPRV), and cellular oxidative stress (in vitro ROS_V) were measured using PM_2.5 collected from Chongqing. OPDTTV was measured to be 1.1-5.4 nmol min^-1 m^-3 with a mean value of 2.8 nmol min^-1 m^-3, which was higher than the values reported in other coastal cities. In particular, airborne radicals (OPEPRV) were measured to be in the range of 4.1 × 10^-3-2.3 × 10^-2 nmol m^-3 with a mean value of 1.2 × 10^-2 nmol m^-3. The OP_V and in vitro ROS_V increased significantly during haze episodes compared with those during clean episodes. OC, Cu, Zn, polycyclic aromatic hydrocarbons (PAHs), and oxygenated PAHs (OPAHs) were observed to be the major contributors to OPDTTV, while nitrated PAHs (NPAHs), EC, Fe, and Cu primarily influenced OPEPRV and in vitro ROS_V. Backward trajectory and potential source contribution function (PSCF) analysis indicated that the source of PM_2.5 oxidative stress effects was mainly derived from the local and western air masses, indicating the roles of atmospheric aging and industrial emission in the health impacts of PM_2.5. Overall, by revealing that transition metals, PAHs, and functionalized PAHs are the most imperative components for both the acellular and cellular health impacts of wintertime PM_2.5 of southwestern China, this work sheds light on future mitigation strategies for improving urban air quality from a public health perspective.

The relationship between microplastics (MPs) and organic pollutants such as organophosphate esters (OPEs), which are widely used as plastic additives is poorly understood. Given the potential toxic implications for such chemical additives, this is a substantial research gap. To address this, we collected 12 sets of freshwater sediment samples from 3 rivers and an urban canal in the West Midlands of the UK between November 2019 and April 2021. Riverine sediment samples were collected both upstream and downstream of waste water treatment plants (WWTPs) discharge points. The mean number of MPs per kg (dw) for all four UK study locations ranged from 67-267 (Birmingham and Worcester Canal), 133-283 (River Tame), 66.67-317 (River Severn), and 67-233 (River Sowe) per month. The highest mean number of MPs per kg was recorded in the River Tame. Overall, 57% of the mean number of MPs identified across all three locations over the 12 months period were detected downstream of the WWTPs while 43% were upstream; however this difference was not significant. Using previously reported concentrations of OPEs in the same samples by our research group, we observed a significant negative correlation (p < 0.05) between mean MPs number and OPE concentrations in sediment at the River Tame over a 12 months sampling period. Additionally, a significant negative correlation was observed between concentrations of Tris(2-butoxyethyl) phosphate (TBOEP)-the most abundant OPE and mean particle number (r = -0.309, p = 0.004). A similar negative correlation was observed between Tri-n-butyl phosphate (TnBP) concentrations and mean MPs per kg at the River Severn. These results suggest that the sources of MPs and OPEs in these waterways may differ and imply that MPs could potentially adsorb OPEs from the sediment in the samples studied.

Onsite wastewater treatment systems (OWTSs) are designed for the removal of pathogens and nutrients from septic effluent. However, many other contaminants are widespread in wastewater including pharmaceuticals, personal care products, and other trace organic chemicals. We analyzed per/polyfluoroalkyl substances (PFASs) in residential septic effluent and investigated their fate in nitrogen-removing biofilters (NRBs), an innovative and alternative type of OWTS. We measured concentrations of 22 targeted PFASs in septic effluent pre- and post-NRB treatment in nine residential OWTSs. We measured total PFAS in septic effluent ranging from 42 to 9795 ng L^-1 and in NRB effluent ranging from 72 to 2575 ng L^-1, corresponding to estimated effluent loads of 39 to 1423 mg PFASs per household per year. Perfluoroalkyl carboxylates (PFCAs) were generally enriched in NRB effluent versus influent while perfluoroalkyl sulfonates appeared to be partially removed during NRB treatment. Grab sampling results were highly variable but passive sampling (microporous polyethylene tubing containing WAX sorbent) consistently showed greater PFAS levels post-NRB treatment. High-resolution mass spectrometry screening of composited grab samples using two different workflows (suspect screening and untargeted analysis with ion mobility spectrometry) resulted in tentative identifications of 40 additional PFASs not included on the target list. The average mass defect of features identified as potential PFASs was significantly lower (p = 0.014) in post-NRB samples. This, along with increasing concentrations of PFCAs in effluent, suggested transformation of precursors to end products with greater fluorinated character in the NRB.

Two long-term air monitoring programs for persistent organic pollutants (POPs) have been established in the Great Lakes Basin (GLB), Ontario, and Alert, Nunavut, Canada since the 1980s for evaluating regional and long-range transport (LRT) dynamics. With growing attention towards Chemicals of Emerging Arctic Concern (CEACs), including volatile halomethoxybenzenes (HMBs) and POPs, these programs have been expanded to monitor CEACs, which can experience significant sampling breakthrough due to their high volatility. To improve collection efficiency, a high-volume air sampler utilizing a polyurethane foam-XAD2 resin sandwich was implemented for concentration characterization at the Alert and GLB sites. At Alert, the air concentrations of hexachlorobutadiene (HCBD), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), 2,4-dibromoanisole (DBA), 2,4,6-tribromoanisole (TBA), and drosophilin A methyl ether (DAME) have increased from 2009 to 2020, with the rising levels of HCBD, HCB, and PeCB potentially linked to unintentional byproducts from industrial processes. Atmospheric concentrations of HMBs and POPs at Alert are primarily governed by LRT, whereas local surface-air exchange exerts a secondary influence on DBA and TBA. In contrast, at GLB sites, local surface-air exchange is the predominant driver of HMB and POP concentrations, regardless of emission origins, with the exception of TBA at Evansville, where additional influencing factors may be involved (i.e. LRT).

Aquatic environments have long been threatened by heavy metal pollution, which poses potential risks to human health. Rizhao City, in a typical coastal area, has witnessed increasingly severe heavy metal contamination in its aquatic systems. To comprehensively assess the status of heavy metal pollution in the aquatic environment and formulate effective mitigation strategies, this study focused on the water, sediments and Pseudorasbora parva from the major rivers and reservoirs in Rizhao City. The distribution characteristics and potential sources of Cr, Ni, Cu, As and Pb were systematically analysed. Ecological risks were evaluated using indices such as the water quality index (WQI), geoaccumulation index (I_geo), bioconcentration factor (BCF), estimated daily intake (EDI), target hazard quotient (THQ) and incremental lifetime cancer risk (ILCR). The results revealed that the average concentrations of heavy metals in water followed the order Cr > Ni > Cu > As > Pb, with variations across different rivers and reservoirs. In sediments, Cr and Ni exhibited higher concentrations in the Chaobai River (CR), reaching 45.21 and 34.87 mg kg^-1, respectively. Cr and Ni showed higher enrichment in the gills and viscera of P. parva compared to muscle tissues, while the distribution patterns of Cu, As and Pb were more complex. WQI assessments indicated that all sampling sites had WQI values <0, suggesting negligible heavy metal pollution levels in water. However, the I_geo values for Ni and Cu in CR sediments were -0.52 and -0.21, respectively, approaching the threshold and warranting attention to potential contamination risks. BCF results demonstrated stronger enrichment capabilities in gills and viscera. Health risk assessments revealed that EDI was correlated with heavy metal concentrations in fish tissues, with THQ > 1 and ILCR > 1.0 × 10^-4 for gills, indicating potential health threats to frequent consumers from long-term ingestion.