Microplastic pollution of intertidal mangrove ecosystems is receiving growing attention, and scientists suspect that the microplastic pollution of semi-enclosed seas is significantly different from that of other coastal types because of their unique geographical features. However, data on the distributions and characteristics of microplastics in the mangrove sediment of semi-enclosed seas are very limited. This study selected the Maowei Sea, a typical semi-enclosed sea, as its representative study site. The analysis revealed that the microplastic abundances in the river estuaries were much lower than those at the oceanic entrance zones, with values ranging from 520 ± 8 to 940 ± 17 items/kg. Polyethylene (PE)/polypropylene (PP)/polystyrene (PS), white/transparent, and <1 mm were the dominant type, colour, and size of the microplastics, respectively, in the observed mangrove sediments. Moreover, some other factors, including the rhizosphere/non-rhizosphere and the proportion of organic matter, codetermined the distribution and characteristics of microplastics. Specifically: (1) the percentage of colorful microplastics were higher in the rhizosphere due to the microbial activities and (2) positive linear relationships were found between the pore volume (PV) values of the free particulate organic matter (FPOM), occluded particulate organic matter (OPOM) (1.6–2.0 g/cm³ and >2.0 g/cm³), and the abundance of very small microplastics (<1 mm).

The widespread application of commercial TiO₂ NPs inevitably leads to their release into environmental waters through various ways. TiO₂ NPs released into water might be absorbed by and react with periphytic biofilms, which are a kind of aquatic environmental media of important ecological significance, and influence the physiological activity and ecological function of periphytic biofilms. This study investigated the effects of exposure to 1 mg/L and 5 mg/L of TiO₂ NPs on periphytic biofilms cultured indoors. After a 10-day exposure to TiO₂ NPs, the growth (measured by chlorophyll-a content) of microalgal community was inhibited greatly (more than 60%); however, the primary production (indicated by quantum yield) of periphytic biofilms maintained changeless. As for bacteria, TiO₂ NP-exposure increased the bacterial diversity and altered the composition structure. Significant changes were observed in the bacterial communities at the class level, mainly including Alphaproteobacteria, Gammaproteobacteria, Cytophagia, Flavobacteriia, Sphingobacteriia, Synechococcophycideae and Oscillatoriophycideae. The enhancement of metabolic activities (the production of extracellular polymeric substances, especially proteins content increased by 48.51%) of periphytic biofilms was a resistance mechanism to toxicity of NPs. As for extracellular enzyme activities of periphytic biofilms, alkaline phosphatase activity was inhibited (22.43%) after exposed to 5 mg/L of TiO₂ NPs, which posed a threat to phosphorus metabolism of periphytic biofilms. Overall, this study demonstrated that 1 mg/L and 5 mg/L of TiO₂ NPs negatively influenced physiological activities and ecological functions of periphytic biofilms, highlighting that the ecological risks of TiO₂ NPs should be paid attention to.

Benzo[a]pyrene (BaP), a common environmental pollutant, can modulate the immune-associated signal pathway NF-κB, which is one of the critical signal pathways involved in various immune responses. BaP exposure usually generates reactive oxygen species (ROS), but whether ROS are predominantly involved in the modulation mechanism of the NF-κB pathway has not been clearly understood. In this study, an in vivo examination of Oryzias melastigma demonstrated that BaP exposure led to a down-regulation of the NF-κB pathway and increased levels of ROS. Conversely, in vitro results using the medaka liver cell line DIT-29 and a widely applied H₂O₂ method showed the opposite: up-regulation of the NF-κB pathway. However, the down-regulation of NF-κB upon BaP exposure in vitro was inhibited by the addition of a ROS inhibitor, indicating ROS are involved in the modulation of NF-κB. The discrepancy between in vivo and in vitro results of ROS impacts on NF-κB activation might be related to the concentration and persistence of ROS. Using a modified luminol detection system, BaP was found to generate sustained physiological concentrations of ROS for 24 h, while an H₂O₂ bolus generated ROS for less than 30 min. Furthermore, a steady-state sub-micromolar H₂O₂ system (H₂O₂ss) was developed in parallel as a positive control of ROS, by which H₂O₂ could be maintained for 24 h. Comparative evaluation using H₂O₂, H₂O₂ss and BaP exposures on the medaka cell line with pGL4.32 demonstrated that the persistent physiological concentrations of ROS generated upon BaP exposure or treatment with H₂O₂ss inhibited the NF-κB pathway, but direct H₂O₂ exposure had the opposite effect. Moreover, a western-blot assay and EMSA detection further confirmed the modulation of the NF-κB pathway in DIT-29. Taken together, this study shows that BaP exposure inhibits the NF-κB pathway by generating sustained physiological concentrations of ROS.

Gut microbiota is of critical importance to host health. Aryl hydrocarbon receptor (AhR) is found to be closely involved in the regulation of gut microbial dynamics. However, it is still not clear how AhR signaling shapes the gut microbiota. In the present study, adult zebrafish were acutely exposed to an AhR antagonist (CH223191), an AhR agonist (polychlorinated biphenyl 126; PCB126) or their combination for 7 d. Overall intestinal health and gut microbial community were temporally monitored (1 d, 3 d and 7 d) and inter-compared among different groups. The results showed that single exposure to PCB126 significantly disrupted the overall health of intestines (i.e., neural signaling, inflammation, epithelial barrier integrity, oxidative stress). However, CH223191 failed to inhibit but enhanced the physiological toxicities of PCB126, implying the involvement of extra mechanisms rather than AhR in the regulation of intestinal physiological activities. Dysbiosis of gut microbiota was also caused by PCB126 over time as a function of sex. It is intriguing that CH223191 successfully abolished the holistic effects of dioxin on gut microbiota, which inferred that growth of gut microbes was directly controlled by AhR activation without the involvement of host feedback modulation. When coming to detailed alterations at certain taxon, both antagonistic and synergistic interactions existed between CH223191 and dioxin, depending on fish sex, exposure duration and bacterial species. Correlation analysis found that gut inflammation was positively associated with pathogenic Legionella bacteria, but was negatively associated with epithelial barrier integrity, suggesting that integral intestinal epithelial barrier can prevent the influx of pathogenic bacteria to induce inflammatory response. Overall, this study has deciphered, for the first time, the direct regulative effects of AhR activity on gut microbiota. Future research is warranted to elucidate the specific mechanisms of AhR action on certain bacterial population.

Blueberry anthocyanin (BA) have strong health benefits as an active natural antioxidant and perfluorooctanoic acid (PFOA) can result in oxidative stress in animals. In our study, the protective effects of BA against stress induced by PFOA was investigated in the planarian Dugesia japonica using oxidative stress biomarkers, ATP contents, ATPase activity, DNA methylation and mRNA expression. PFOA exposure could resulted in malondialdehyde production. At the same time, treatment with BA decreased the production of malondialdehyde in BA-exposed and co-treatment planarians. PFOA caused activities increase in glutathione peroxidase (GPx), glutathione S-transferase (GST) and activities decrease in glutathione reductase (GR). PFOA exposure decreased the GSH and ATP contents. Additionally, it increased the GSSG contents and ATPase activity. BA administration increased the activities of GPx, GST and GR in BA and co-treatment planarians. Meanwhile BA maintained the contents of ATP, ATPase activity, GSH and GSSG by alleviating PFOA toxicity. Moreover, PFOA and BA increased the contents of 5-methylcytosine and decreased 5-hydroxymethylcytosine in all group. In addition, PFOA and BA treated planarians significantly altered the expression of genes associated with above biochemical parameters. The results showed that the mRNA expression of gpx, Djgst, gr, Djnak and dnmt1 were significantly elevated in all groups. Alterations in the mRNA expression levels indicated a stress response to PFOA exposure and anthocyanin protection. These alterations regulated biomarkers of oxidative stress, energy metabolism and DNA methylation levels in planarians. These results indicate that BA attenuated PFOA-induced oxidative stress, energy metabolism, DNA methylation and gene expression disorders.

Absolute principal component score/multiple linear regression (APCS/MLR) and positive matrix factorization (PMF) were applied to a dataset consisting of 10 heavy metals in 300 surface soils samples. Robust geostatistics were used to delineate and compare the factors derived from these two receptor models. Both APCS/MLR and PMF afforded three similar source factors with comparable contributions, but APCS/MLR had some negative and unidentified contributions; thus, PMF, with its optimal non-negativity results, was adopted for source apportionment. Experimental variograms for each factor from two receptor models were built using classical Matheron's and three robust estimators. The best association of experimental variograms fitted to theoretical models differed between the corresponding APCS and PMF-factors. However, kriged interpolation indicated that the corresponding APCS and PMF-factor showed similar spatial variability. Based on PMF and robust geostatistics, three sources of 10 heavy metals in Guangrao were determined. As, Co, Cr, Cu, Mn, Ni, Zn, and partially Hg, Pb, Cd originated from natural source. The factor grouping these heavy metals showed consistent distribution with parent material map. 43.1% of Hg and 13.2% of Pb were related to atmosphere deposition of human inputs, with high values of their association patterns being located around urban areas. 29.6% concentration of Cd was associated with agricultural practice, and the hotspot coincided with the spatial distribution of vegetable-producing soils. Overall, natural source, atmosphere deposition of human emissions, and agricultural practices, explained 81.1%, 7.3%, and 11.6% of the total of 10 heavy metals concentrations, respectively. Receptor models coupled with robust geostatistics could successfully estimate the source apportionment of heavy metals in soils.

Chemical compositions of fog and rain water were measured between July 2017 and September 2018 at Sejila Mountain, southeast Tibet, where fog events frequently occurred in original fir forests at altitude 3950 m. Fog water samples were collected using a Caltech Active Strand Cloud Collector (CASCC), and rain samples were collected using a precipitation gauge. Differences were observed between fog water and rain composition for most analyzed ions. Ion abundance in fog water was Ca²⁺ > Cl⁻ > Na⁺ > SO₄²⁻ > Mg²⁺ > NH₄⁺ >K⁺ > NO₃⁻ whereas an order of Ca²⁺ > Na⁺ > Cl⁻ > Mg²⁺ > SO₄²⁻ > NO₃⁻ > K⁺ > NH₄⁺ was observed for rain water. All ion concentrations were higher in fog water than in rain water. Additionally, Ca²⁺ was the dominant cation in both fog and rain samples, accounting for more than half of all measured cations. NH₄⁺ and SO₄²⁻ concentrations were notable for being higher in fog than rain water when compared with other ions. For trace elements, Al, As, Mn and Se were the most abundant elements in fog water; only Al and As were detected in rain water. Seventy-two hour back-trajectory analysis showed that air masses during fog and/or rain events mainly came from the south of Sejila Mountain. Spearman correlation analysis and source contribution calculations indicated that both marine and terrestrial sources contributed to the observed ion concentrations. Considering the higher concentrations of NH₄⁺ and higher ratio of NH₄⁺/NO₃⁻ measured in fog than in rain, we suggest that quantification of fog nitrogen deposition and its ecological effect in this area should be given more attention.

In order to evaluate the effect of mining activity on the environment of the Qhorveh mining area in the west of Iran, the geological, ecological and environmental data, related to social development and regional economic status, were used. The geological data included seven sub-indices, such as vegetation coverage, land utilization type, and fault activity; ecological data, with two sub-indices, such as degree of ecological environment recovery; and finally, environmental data, with three sub-indices, such as soil and dust pollutions. These were selected based on the literature and expert opinion which were utilized for environmental pollution and geo-ecological (EPGE) risk assessment of the study site. Remote sensing (RS) image, field sampling, digital elevation map, and data retrieved from different government agencies were used to generate layers for the sub-indices in the geographic information system (GIS) environment. In addition, the analytical hierarchy process (AHP) method was used to determine the weight of sub-indices. Five levels consisting of best, good, middle, poor and worst were used to describe the EPGE risk assessment of the Qhorveh mining area. Results showed that worst and poor levels of EPGE risk are in the east and northeast of the study area where the gold and pumice mines are located while best and good levels of EPGE risk are in its center where the stone mines are located. According to the results of this research, the EPGE risk assessment of the Qhorveh mining area is affected by the environmental pollution index with its highest weight (0.3908). It can be concluded that the integration of the RS, GIS and AHP methods proposed in this study improved the evaluation quality of EPGE risk assessment.

Electron transfer capacities (ETC) of humic-like acids (HLA) and their effects on dechlorination are dependent on their redox-active properties. Aging and minerals can affect the chemical compositions and structures of HLA. However, the underlying mechanism and the impacts on the dechlorination capacities of HLA are poorly understood. We investigated how redox properties change in association with the intrinsic chemical natures and exterior minerals of the HLA extracted from landfilled solid wastes. Furthermore, the ETC of the landfill-derived HLA could be strengthened by increasing landfill age and demineralization, thereby facilitating the dechlorination of pentachlorophenol (PCP). The HLA molecules started to polymerize aromatic macromolecules during landfilling, leading to an increase in ETC and dechlorination capacities. Macromolecular HLA were dissociated to smaller molecules and exposed more aromatic and carboxyl groups when separated from minerals, which enhanced the ETC and the dechlorination abilities of the HLA. Microbial-mediated dechlorination was an effective way to degrade PCP, and almost 80% of the PCP was transformed after 40 days of demineralized HLA and Shewanella oneidensis MR-1 incubation. The demineralization and aging further facilitated the microbial-mediated PCP dechlorination. The findings provide a scientific base for improving in-situ bioremediation of chlorinated compound-contaminated soils using freshly synthesized HLA.

The heavy metal concentration of soil samples often exhibits a skewed distribution, especially for soil samples from mining areas with an extremely high concentration of heavy metals. In this study, to model soil contamination in mining areas using reflectance spectroscopy, the skewed distribution was corrected and heavy metal concentration estimated. In total, 46 soil samples from a mining area, along with corresponding field soil spectra, were collected. Laboratory spectra of the soil samples and the field spectra were used to estimate copper (Cu) concentration in the mining area. A logarithmic transformation was used to correct the skewed distribution, and based on the sorption of Cu on spectrally active soil constituents, the spectral bands associated with iron oxides were extracted from the visible and near-infrared (VNIR) region and used in the estimation. A genetic algorithm was adopted for band selection, and partial least squares regression was used to calibrate the estimation model. After transforming the distribution of Cu concentration, the accuracies (R2) of the estimation of Cu concentration using laboratory and field spectra separately were 0.94 and 0.96. The results indicate that Cu concentration in the mining area can be estimated using reflectance spectroscopy following correction of skewed distribution.