Microplastics, an emerging pollutant in the environment, have attracted extensive attention in recent years for their possible negative impact on organisms. However, direct and indirect effects of polystyrene (PS) microplastics on vegetables are still not completely known. In this study, we used red lettuce (Lactuca sativa L. Red Sails) in a hydroponic system to investigate the effects of nano- and micro-sized PS and dibutyl phthalate (DBP) on the photosynthesis and red lettuce quality. The results clearly indicated that PS reduced the bioavailability of DBP while causing a decrease in the photosynthetic parameters as well as the total chorophyll content compared to DBP alone by affecting the crystalline structure of the water-soluble chlorophyll protein. Compared with DBP monotherapy, the presence of PS significantly increased hydrogen peroxide and malondialdehyde content in the lettuce treated with DBP, indicating serious oxidative damage. Furthermore, the soluble protein and sugar content in lettuce leaves decreased with higher PS concentration and smaller PS size. It may be due to PS inhibited lettuce root and ribulose-1,5-bisphosphate carboxylase/oxygenase activities. In contrast, nitrite content increased significantly with the induction of the glutathione-ascorbic acid cycle, indicating that the presence of PS reduced the quality of DBP-treated-red lettuce. Additionally, the nano-sized PS greatly inhibited lettuce growth and quality more than the micro-sized PS. This study described the interactions between microplastics and phthalates using molecular simulation and experimental validation to highlight the potential risks of microplastics on vegetable crop production.

Microorganisms comprise the bulk of biodiversity and biomass in Antarctic terrestrial ecosystems. To effectively protect and manage the Antarctic environment from anthropogenic impacts including contamination, the response and recovery of microbial communities should be included in soil remediation efficacy and environmental risk assessments. This is the first investigation into the microbial dynamics associated with large scale bioremediation of hydrocarbon contaminated soil in Antarctica. Over five years of active management, two significant shifts in the microbial community were observed. The initial shift at 12–24 months was significantly correlated with the highest hydrocarbon degradation rates, increased microbial loads, and significant increases in alkB gene abundances. ANCOM analysis identified bacterial genera most likely responsible for the bulk of degradation including Alkanindiges, Arthrobacter, Dietzia and Rhodococcus. The second microbial community shift occurring from 36 to 60 months was associated with further reductions in hydrocarbons and a recovery of amoA nitrification genes, but also increasing pH, accumulation of nitrite and a reduction of oligotrophic bacterial species. Over time, the addition of inorganic fertilisers altered the soil chemistry and led to a disruption of the nitrogen cycle, most likely decoupling ammonia oxidisers from nitrite oxidisers, resulting in nitrite accumulation. The results from this study provide key insights to the long-term management of hydrocarbon bioremediation in Antarctic soils.

Sulfate radical (SO₄⁻)-based advanced oxidation processes (SR-AOPs) are promising in-situ chemical oxidation technologies widely applied for soil/groundwater remediation. The presence of non-target water constituents may interfere the abatement of contaminants by SR-AOPs as well as result in the formation of unintended byproducts. Herein, we reported the formation of toxic chloronitrophenols during thermally activated persulfate oxidation of 2-chlorophenol (2CP) in the presence of nitrite (NO₂⁻). 2-Chloro-4-nitrophenol (2C4NP) and 2-chloro-6-nitrophenol (2C6NP) were identified as nitrated byproducts of 2CP with total yield up to 90%. The formation of nitrated byproducts is a result of coupling reaction between 2CP phenoxyl radical (ClPhO) and nitrogen dioxide radical (NO₂). As a critical step, the formation of ClPhO was supported by density functional theory (DFT) computation. Both 2C4NP and 2C6NP could convert to 2-chloro-4,6-dinitrophenol (2C46DNP) upon further treatment via a denitration-renitration process. The formation rate of 2C4NP and 2C6NP was closely dependent on the concentration of NO₂⁻, solution pH, and natural water constituents. ECOSAR calculation suggests that chloronitrophenols are generally more hydrophobic and ecotoxic than 2CP. Our result therefore reveals the potential risks in the abatement of chlorophenols by SR-AOP, particularly when high level of NO₂⁻ is present in water matrix.

Thiocyanate (SCN⁻)-based autotrophic denitrification (AD) has recently been demonstrated as a promising technology that could be integrated with anaerobic ammonium oxidation (Anammox) to achieve simultaneous removal of nitrogen and SCN⁻. However, there is still a lack of a complete SCN⁻-based AD model, and the potential microbial competition/synergy between AD bacteria and Anammox bacteria under different operating conditions remains unknown, which significantly hinders the possible application of coupling SCN⁻-based AD with Anammox. To this end, a complete SCN⁻-based AD model was firstly developed and reliably calibrated/validated using experimental datasets. The obtained SCN⁻-based AD model was then integrated with the well-established Anammox model and satisfactorily verified with experimental data from a system coupling AD with Anammox. The integrated model was lastly applied to investigate the impacts of influent NH₄⁺-N/NO₂⁻-N ratio and SCN⁻ concentration on the steady-state microbial composition as well as the removal of nitrogen and SCN⁻. The results showed that the NH₄⁺-N/NO₂⁻-N ratio in the presence of a certain SCN⁻ level should be controlled at a proper value so that the maximum synergy between AD bacteria and Anammox bacteria could be achieved while their competition for NO₂⁻ would be minimized. For the simultaneous maximum removal (>95%) of nitrogen and SCN⁻, there existed a negative relationship between the influent SCN⁻ concentration and the optimal NH₄⁺-N/NO₂⁻-N ratio needed.

Abandoned nonferrous metal(loid) tailings sites are anthropogenic, and represent unique and extreme ecological niches for microbial communities. Tailings contain elevated and toxic content of metal(loid)s that had negative effects on local human health and regional ecosystems. Microbial communities in these typical tailings undergoing natural attenuation are often very poorly examined. The diversity and inferred functions of bacterial communities were examined at seven nonferrous metal(loid) tailings sites in Guangxi (China), which were abandoned between 3 and 31 years ago. The acidity of the tailings sites rose over 31 years of site inactivity. Desulfurivibrio, which were always coupled with sulfur/sulfide oxidation to dissimilate the reduction of nitrate/nitrite, were specific in tailings with 3 years abandonment. However, genus beneficial to plant growth (Rhizobium), and iron/sulfur-oxidizing bacteria and metal(loid)-related genera (Acidiferrobacter and Acidithiobacillus) were specific within tailings abandoned for 23 years or more. The increased abundance of acid-generating iron/sulfur-oxidizing and metal(loid)-related bacteria and specific bacterial communities during the natural attenuation could provide new insights for understanding microbial ecosystem functioning in mine tailings. OTUs related to Sulfuriferula, Bacillus, Sulfurifustis, Gaiella, and Thiobacillus genera were the main contributors differentiating the bacterial communities between the different tailing sites. Multiple correlation analyses between bacterial communities and geochemical parameters indicated that pH, TOC, TN, As, Pb, and Cu were the main drivers influencing the bacterial community structures. PICRUSt functional exploration revealed that the main functions were related to DNA repair and recombination, important functions for bacterial adaptation to cope with the multi-contamination of tailings. Such information provides new insights to guide future metagenomic studies for the identification of key functions beyond metal-transformation/resistance. As well, our results offers novel outlooks for the management of bacterial communities during natural attenuation of multi-contaminated nonferrous metal(loid) tailings sites.

In order to understand the impacts of regional emission changes and local tourism on sulfur and nitrogen wet deposition in Jiuzhaigou National Nature Reserve of southwestern China, wet deposition was monitored at a background site (Rize) and a tourist-affected site (PE: park entrance) in the reserve during 2015–2016. The observation data were compared between Rize and PE and between 2010–2011 and 2015–2016 monitoring campaigns. Also, the observation data were used in the Positive Matrix Factorization (PMF) model to identify the major sources of sulfur and nitrogen wet deposition. The results show that although local tourism emissions had considerable contributions to NH₄⁺, NO₂⁻, NO₃⁻, and SO₄²⁻ concentrations in wet deposition (p < 0.05), most of the annual Volume Weighted Mean (VWM) concentrations of these four ions were likely from emissions outside Jiuzhaigou. Annual wet deposition fluxes of the four ions were also affected more by precipitation and regional emissions than by local emissions. Although annual precipitation was higher at Rize (818 mm) during 2015–2016 than at another background site near Long Lake (LL: 752 mm) during 2010–2011, the annual concentrations and fluxes of SO₄²⁻ and NO₃⁻ wet deposition decreased by 77% and 74% for SO₄²⁻ and by 12% and 19% for NO₃⁻, respectively, most likely due to regional emission reductions. Similar large reductions in SO₄²⁻ and NO₃⁻ concentrations have been also found in some other sites in southwestern China. In contrast, the annual concentration and flux of NH₄⁺ wet deposition at Rize during 2015–2016 were 1.4 and 1.2 times of that measured at LL during 2010–2011, respectively. The results of source apportionment analysis and tour bus emission estimates suggest that elevated NH₄⁺ wet deposition was possibly related to NH₃ emissions from local tour buses, but additional studies on NH₃ emissions from tour buses in the reserve are needed to confirm this.

To meet the increasing global energy demand, expanding exploration for oil and gas reserves as well as associated drilling activities are expected in the Arctic-boreal region where sponge aggregations contribute to up to 90% of benthic biomass. These deep-water sponges along with their microbial endobionts play key roles in the nitrogen cycling in Arctic-boreal ecosystems. This study aimed to investigate the effects of drilling discharges and associated sediment resuspension events on net fluxes of oxygen, ammonium, nitrate and nitrite in three common deep-water sponge species in the form of explants. Sponges were exposed to suspended bentonite and barite, the primary particulate compounds in drilling waste, as well as suspended natural sediment particles for a period of 33 days (on average 10 mg L−1 for 12 h day−1). The exposure period was followed by a pollution abatement period for a further 33 days. No sponge mortality was observed during the experiment. However, exposure to these particles, especially to barite, led to reduced oxygen consumption by up to 33% that was linearly correlated with reduced nitrite/nitrate release by the sponges. The changes in net fluxes were accompanied by decreased tissue oxygenation by up to 54% within the sponges. These findings reveal the effects of fine particles on sponge metabolic processes by reducing aerobic respiration and microbial nitrification, and possibly by favouring anaerobic processes such as microbial denitrification. Most of the sponge responses recovered to their control levels upon the pollution abatement period, but the effects caused by barite may not be reversible. Our findings provide the first insight into the ecological consequences of oil and gas drilling activities on sponge-mediated nitrogen cycling in the Arctic-boreal region.

Toxicity and uptake of nano-CeO2 (nCeO2) in edible vegetables are not yet fully understood. In the present study, we grew romaine lettuce in sand amended with nCeO2. At high concentrations (1000 and 2000 mg/kg), nCeO2 diminished the chlorophyll content by 16.5% and 25.8%, respectively, and significantly inhibited the biomass production. nCeO2 (≥100 mg/kg) altered antioxidant enzymatic activities and malondialdehyde levels in the plants. nCeO2 (≥500 mg/kg) triggered a remarkable increase of nitrate-N level in the shoots, which can be converted to toxic nitrite in humans thereby posed risk to human health. Concentration dependent accumulation of Ce in the plant tissues was observed. X ray absorption near edge spectroscopy (XANES) results indicate that Ce presented as nCeO2 and CePO4 in the roots while as nCeO2 and Ce carboxylates in the shoots. Chelation of Ce3+ by citric acid or precipitation of Ce3+ by PO43− reduced the translocation and toxicity of nCeO2, indicating that release of Ce3+ played a critical role in the toxicity nCeO2.

Disruption of non-reproductive endocrine systems in wildlife by chemicals has received little attention but represents a potentially significant problem. Nitrate is a major anthropogenic contaminant in the freshwater aquatic environment and has been identified as a potential disrupter of endocrine function in aquatic animals. This study was conducted to investigate the relationship between the function of the neuroendocrine stress axis in fish and inorganic N loading along reaches of rivers receiving cumulative point source and diffuse chemical inputs. To accomplish this, the responsiveness of the stress axis, quantified as the rate of release of cortisol to water across the gills during exposure to a standardised stressor, was measured in three-spined sticklebacks (Gasterosteus aculeatus L.) resident at three sites on each of four rivers in north-west England. The magnitude of the stress response in fish captured at the sites furthest downstream on all rivers was more than twice that of fish captured at upstream sites. Site-specific variation in stress axis reactivity was better explained by between-site variation in concentrations of dissolved nitrate, nitrite, and ammonia than by the concentration of wastewater treatment works effluent. An increase in the magnitude of the stress response was seen among sticklebacks at sites where long-term averaged concentrations of NH3-N, NO3-N and NO2-N exceeded 0.6, 4.0 and 0.1 mg/L respectively. These data suggest that either (i) inorganic N is a better surrogate than wastewater effluent concentration for an unknown factor or factors affecting stress axis function in fish, or (ii) dissolved inorganic N directly exerts a disruptive influence on the function of the neuroendocrine stress axis in fish, supporting concerns that nitrate is an endocrine-modulating chemical.

Increases in water temperature, as a result of climate change, may influence biogeochemical cycles, sediment-water fluxes and consequently environmental sustainability. Effects of rising temperature on dynamics of nitrate, nitrite, ammonium, dissolved inorganic nitrogen (DIN), dissolved reactive phosphorus (DRP), dissolved organic carbon (DOC) and gaseous nitrogen (N2 and N2O) were examined in a subtropical river (the Jiulong River, southeast China) by microcosm experiments. Slurry sediments and overlying water were collected from three continuous cascade reservoirs, and laboratory incubations were performed at four temperature gradients (5 °C, 15 °C, 25 °C and 35 °C). Results indicated: (1) warming considerably increased sediment ammonium, DIN and DOC fluxes to overlying water; (2) warming increased retention of nitrate, and to a lesser extent, nitrite, corresponding to increases in N2 and N2O emission; (3) DRP was retained but released from Fe/Al-P enriched sediments at high temperature (35 °C) due to enhanced coupled transformation of carbon and nitrogen with oxygen deficiency. Using relationships between sediment fluxes and temperature, a projected 2.3°C-warming in future would increase ammonium flux from sediment by 7.0%–16.8%, while increasing nitrate flux into sediment by 8.9%–28.6%. Moreover, substrates (e.g., grain size, carbon availability) influenced nutrient delivery and cycling across cascade reservoirs. This study highlights that warming would increase bioreactive nutrient (i.e., ammonium and phosphate) mobilization with limited gaseous N removal from sediments, consequently deteriorating water quality and increasing eutrophication with future climate change.