Microbial communities in activated sludge (AS) have a significant influence on the functions and stability of aeration tanks in wastewater treatment plants (WWTPs). The microbial community structure is affected by various factors, among which operational parameters outcompeted as the key factors in shaping its structure. However, as an important operational parameter of aeration tank, the mechanisms by which sludge retention time (SRT) affect community properties remain unclear. In this study, 144 AS samples from aeration tanks of 48 full-scale WWTPs operating under different SRT conditions were examined via high-throughput Illumina-MiSeq sequencing technology. The results indicated that SRT significantly affected the diversity, composition, assembly, and co-occurrence patterns of the microbial community in aeration tanks. Moreover, our results provided clear evidence that the microbial communities in aeration tanks operating under SRT of 10–20 days have the highest biodiversity, the lowest stochastic processes influence, the more stable molecular ecological network structure, the lowest risks of filamentous sludge bulking and enhanced nitrogen removal potential. The microbial communities could be more stable and resilient to disturbance when aeration tanks were operated under this SRT condition. The findings of this study provided a reference for the optimization of aeration tanks from an of microbial community perspective.

Cadmium (Cd) is a toxic heavy metal and widespread in environment and food, which is adverse to human and animal health. Food intervention is a hot topic because it has no side effects. Selenium (Se) is an essential trace element, found in various fruits and vegetables. Many previous papers have described that Se showed ameliorative effects against Cd. However, the underlying mechanism of antagonistic effect of Se against Cd-induced cytotoxicity in avian leghorn male hepatoma (LMH) cells is unknown, the molecular mechanism of Se antagonistic effect on Cd-induced and calcium (Ca²⁺) homeostasis disorder and crosstalk of ER stress and autophagy remain to be explored. In order to confirm the antagonistic effect of Se on Cd-induced LMH cell toxicity, LMH cells were treated with CdCl₂ (2.5 μM) and Na₂SeO₃ (1.25 and 2.5 μM) for 24 h. In this study, Cd exposure induced cell death, disrupted intracellular Ca²⁺ homeostasis and Ca²⁺ homeostasis related regulatory factors, interfered with the cycle of cadherin (CNX)/calreticulin (CRT), and triggered ER stress and autophagy. Se intervention inhibited Cd-induced LDH release and crosstalk of ER stress and autophagy via regulating intracellular Ca²⁺ homeostasis. Moreover, Se mitigated Cd-induced Intracellular Ca²⁺ overload by Ca²⁺/calmodulin (CaM)/calmodulin kinase IV (CaMK-IV) signaling pathway. Herein, CNX/CRT cycle played a critical role for the protective effect of Se on Cd-induced hepatotoxicity. Based on these findings, we demonstrated that the application of Se is beneficial for prevention and alleviation of Cd toxicity.

Evidence for effects of PM₂.₅ on systemic oxidative stress in pregnant women is limited, especially in early pregnancy. To estimate the associations between ambient PM₂.₅ exposures and biomarkers of lipid peroxidation and total antioxidant capacity (T-AOC) in women with normal early pregnancy (NEP) and women with clinically recognized early pregnancy loss (CREPL), 206 early pregnant women who had measurements of serum malondialdehyde (MDA) and T-AOC were recruited from a larger case-control study in Tianjin, China from December 2017 to July 2018. Ambient PM₂.₅ concentrations of eight single-day lags exposure time windows before blood collection at the women’s residential addresses were estimated using temporally-adjusted land use regression models. Effects of PM₂.₅ exposures on percentage change in the biomarkers were estimated using multivariable linear regression models adjusted for month, temperature, relative humidity, gestational age and other covariates. Unconstrained distributed lag models were used to estimate net cumulative effects. Increased serum MDA and T-AOC were significantly associated with increases in PM₂.₅ at several lag exposure time windows in both groups. The net effects of each interquartile range increase in PM₂.₅ over the preceding 8 days on MDA were significantly higher (p < 0.001) in CREPL [52% (95% CI: 41%, 62%)] than NEP [22% (95% CI: 9%, 36%)] women. Net effects of each interquartile range increase in PM₂.₅ over the preceding 5 days on T-AOC were significantly lower (p = 0.010) in CREPL [14% (95% CI: 9%, 19%)] than NEP [24% (95% CI: 18%, 29%)] women. Exposure to ambient PM₂.₅ may induce systemic lipid peroxidation and antioxidant response in early pregnant women. More severe lipid peroxidation and insufficient antioxidant capacity associated with PM₂.₅ was found in CREPL women than NEP women. Future studies should focus on mechanisms of individual susceptibility and interventions to reduce PM₂.₅-related oxidative stress in the first trimester.

The principal aim of this study was to understand the enrichment patterns of elements in water from typical coal mine and irrigation areas. For this study, samples of surface water, shallow water, and deep water were collected from Handan, Jining, and Heze cities and their surrounding areas in the central North China Plain. The results showed that the hydrochemical characteristics were dominated by Ca–Mg–Cl and Ca–HCO₃. Elements in the studied surface water, including strontium, iron and boron, were anomalously enriched at levels more than 654, 294 and 134 times their global river water averages, respectively. The concentrations of elements in the studied area were influenced by both natural processes and anthropogenic sources, but the dominant origins of the anomalous enriched elements were bedrock weathering and soil leaching. The deep well water quality in the Handan coal mining area was good, while the poor-quality water samples in the study area were mainly distributed in the alluvial plain, which is characterized by Neogene-Quaternary sediments and aquifers. The measured hazard quotient and hazard index values indicate that the arsenic and nickel in the studied samples could pose a noncarcinogenic risk to the health of local residents, especially children. The leading source of the high arsenic levels is influenced by natural process. Monitoring plans for arsenic, iron, manganese, nitrate and other potentially harmful elements in surface water and groundwater and effective health education on pollution by these elements are essential.

Marine and freshwater plastic pollution is a challenging issue receiving large amounts of research and media attention. Yet, few studies have documented the impact of microplastic ingestion to aquatic organisms. In the Pacific Northwest, Chinook salmon are a culturally and commercially significant fish species. The presence of marine and freshwater microplastic pollution is well documented in Chinook salmon habitat, yet no research has investigated the impacts to salmon from microplastic ingestion. The majority of the marine microplastics found in the Salish Sea are microfibers, synthetic extruded polymers that come from commonly worn clothing. To understand the potential impacts of microfiber ingestion to fish, we ran a feeding experiment with juvenile Chinook salmon to determine if ingested fibers are retained or digestion rates altered over a 10 day digestion period. The experiment was completed in two trials, each consisted of 20 control and 20 treatment fish. Treatment fish were each fed an amended ration of 12 food pellets spiked with 20 polyester microfibers and control fish were fed the same ration without added microfibers. Fish were sampled at day 0, 3, 5, 7, and 10 to assess if fibers were retained in their gastrointestinal tract and to determine the rate of digestion. Fibers for the experiment came from washing a red polyester fleece jacket in a microfiber retention bag. Fibers had a mean length of 4.98 mm. Results showed fish were able to clear up to 94% of fed fibers over 10 days. Differences in mean gastrointestinal mass were not statistically significant at any sampled time between treatment and controls, suggesting that the ingestion of microfibers did not alter digestion rates. Further work is needed to understand if repeated exposures, expected in the environment, alter digestion or food assimilation for growth.

The Bohai Sea is a shallow-water, semi-enclosed marginal sea of the Northwest Pacific. Since the late 1990s, it has suffered from nutrient over-enrichment. To better understand the eutrophication characteristics of this important coastal sea, we examined four survey datasets from summer (June 2011), late autumn (November 2011), winter (January 2016), and early spring (April 2018). Nutrient conditions in the Bohai Sea were subject to seasonal and regional variations. Survey-averaged N/P ratios in estuarine and nearshore areas were 20–133. In contrast, the central Bohai Sea had mean N/P ratios of 16.9 ± 3.4 in late autumn, 16.1 ± 3.0 in winter and 13.5 ± 5.8 in early spring, which are close to the traditional N:P Redfield ratio of 16. In summer, both dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) were used up in the surface waters of the central Bohai Sea, suggesting that the biological consumption of DIN and DIP may also follow the Redfield ratio. Wintertime nutrient budgets of the central Bohai Sea water were then established based on a mass balance study. Our results suggest that the adjacent North Yellow Sea supplied additional DIP to the central Bohai Sea via wintertime water intrusion, balancing terrigenous excess DIN that was introduced in summer. A water-mixing simulation combining these two nutrient sources with atmospheric nitrogen deposition suggests that eutrophication in the central Bohai Sea will likely be enhanced by the large-scale accumulation of anthropogenic nitrogen in adjacent open oceans. Such changes in nutrients may have fundamentally contributed to the recent development of algal blooms and seasonal hypoxia in the central Bohai Sea.

Trace elements can be toxic when they cannot be easily removed after entering an ecosystem, so a long-term assessment is fundamental to guide ecosystem restoration after catastrophic pollution. In 1998, a pyrite mining accident in Aznalcóllar (south-western Spain) spilled toxic waste over a large area of the Guadiamar river basin, where, after restoration tasks, the Guadiamar Green Corridor was established. Eight years after the mine accident (2005–2006), the ground-dwelling insectivorous lizard Psammodromus algirus registered high trace-element levels within the study area compared to specimens from a nearby unpolluted control site. In 2017, 20 years after the accident, we repeated the sampling for this lizard species and also quantified trace elements in vegetation as well as in arthropod samples in order to identify remnant trace-element accumulation with the aim of assessing the transfer of these elements through the trophic web. We found remnant trace-element contamination in organisms of the polluted site compared to those from the unpolluted site. All trace-element concentrations were higher in arthropods than in plants, suggesting these compounds bioaccumulate through the trophic web. Lizards from the polluted areas had higher As, Cd, and Hg concentrations than did individuals from the unpolluted area. Lizard abundance between sampling periods (2005–06 and 2017) did not vary in unpolluted transects but strongly declined at polluted ones. By contrast, the Normalized Difference Vegetation Index indicated that in the study period, the vegetation was similar at the two sampling sites. These results suggest that, 20 years after the accident, the trace-element pollution could be the cause of a severe demographic decline of the lizard in the polluted area.

To highlight the levels and distributions and to assess the risk of human exposure of chlorinated paraffins (CPs) in PM₂.₅ in China, the concentrations and homologue patterns of short−chain chlorinated paraffins (SCCPs) and medium−chain chlorinated paraffins (MCCPs) in PM₂.₅ from 10 cities in China were studied in 2013 and 2014. The mean concentrations of ΣSCCPs and ΣMCCPs were 19.9 ± 41.1 ng m⁻³ and 15.6 ± 18.6 ng m⁻³, respectively. Unexpectedly, the highest pollution levels occurred in two central cities (Xinxiang and Taiyuan) rather than in well−known eastern megacities such as Beijing, Nanjing, Shanghai, and Guangzhou. By comparing with earlier research, it has indicated the trend of CPs industry shifting from large eastern cities to small and medium-sized cities in central China to some extent. In addition, the composition pattern of SCCPs demonstrated an obviously differences from previous studies, with C₁₁ and Cl₇ predominating and accounting for 45.1% and 24.9%, respectively. Meanwhile, the ratio of MCCPs/SCCPs in most cities was less than 1.00 except for Guangzhou (1.92), Shanghai (1.29), and Taiyuan (1.11). Combined with the results of correlation analysis and principal component analysis, the observed pollution characteristics of CPs in PM₂.₅ had similar sources, which were more influenced by the ratio of MCCPs/SCCPs than by organic carbon, elemental carbon, temperature, population, and gross domestic product. Overall, the composition of CPs reflected the characteristics of local industrial production and consumption, and also implied efforts of Chinese enterprises to reduce the content of short carbon groups of CPs production. The CPs mainly deposited in head airways during the process of entering the human respiratory system. However, at the present levels, there was no significant carcinogenic effect for human health.

Distinct cropland acidification has been reported in China due to nitrogen (N) fertilizer overuse. However, the impacts on food production and thereby on food security are largely unknown. Yield losses in the period 1980–2050 were therefore assessed by simulating soil pH changes combined with derived pH-yield relationships for wheat, maize and rice. If the N fertilizer input continues to increase at 1% annually, the predicted average soil pH decline is about one unit and relative yield losses are expected to increase from approximately 4%–24% during 2010–2050. If the N fertilizer increase stops in 2020 (N2020), the expected losses are approximately 16% in 2050, which is comparable to a scenario of 100% crop residue return (100%RR). However, if 30% of the N fertilizer is replaced by manure N (30%MR), the losses reduce to near 5% in 2050. Soil acidification was predicted to reverse and expected losses are only 2.5% in 2050 in a combined scenario of N2020, 100%RR and 30%MR. Our results illustrate the potential food insecurity induced by cropland acidification and address the necessity of mitigation.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and could produce oxidative toxicity to plants. Our previous study has shown that miR398 is involved in response to phenanthrene treatment by targeting CSD1 and CSD2. However, it is not clear which is essential for CSD1 and CSD2 and how miR398 changes. In this study, we performed discontinuous PAGE to separate superoxide dismutase (SOD) isozymes and found that two bands of the cytosolic Cu/Zn-SOD are induced by phenanthrene at day 5 and 7. Low expression of pri-miR398 and high expression of pre-miR398 indicate that the conversion process from pri-miR398 to pre-miR398 is impeded, which causes decrease in mature miR398. The relative expression of CSD1 is entirely up-regulated, further confirming the important role of CSD1 in response to phenanthrene exposure. Besides, the overexpression of WRKY implies its potential function in answering the call from phenanthrene stress. Therefore, it is concluded that the gene silencing of CSD1 recedes due to the biosynthesis inhibition of miR398, causing the increase of SOD activity in response to phenanthrene exposure in wheat roots. Our results are useful not only for better understanding miRNAs regulation in detoxication of reactive oxygen species, but also for alleviating the toxicity to crops caused by PAHs.