Multiple types of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and hexachlorobenzene (HCB), can be unintentionally released from combustion or thermal industrial processes, which are speculated to be the main sources of these contaminants, as they were banned on production and use since several decades ago. In this study, concentrations and sources of 40 PCBs, 39 PCNs, and HCB were analyzed in air samples collected during the period 2012–2015 at a background site in east China. ΣPCBs, ΣPCNs, and HCB were in the range of 9–341 pg/m³, 6–143 pg/m³, and 14–522 pg/m³, respectively. Seasonal characteristics with high levels in winter and low levels in summer were observed for PCNs and HCB. PCBs also exhibited slightly higher levels in winter. Source apportionment was conducted, using polycyclic aromatic hydrocarbons (PAHs) as combustion sources indicator, combined with principal component analysis (PCA) and positive matrix factorization (PMF) model. The results indicated that the legacy of past produced and used commercial PCBs was the dominant contributor (∼56%) to the selected PCBs in the atmosphere in east China. PCNs were mainly emitted from combustion sources (∼64%), whereas HCB almost entirely originated from combustion process (>90%).

Eating fish provides numerous health benefits, but it is also a dominant pathway for human exposure to contaminants. Many studies have examined mercury (Hg) accumulation in fish, but fewer have considered other elements, such as arsenic (As) and chromium (Cr). Recently, freshwater fish from several pristine boreal systems across northern Ontario, Canada, have been reported with elevated concentrations of As and Cr for reasons that are not well understood. Our goal was to investigate the ecological and environmental influences over concentrations of As, Cr, and other elements in these fish to better understand what affects metal uptake and the risk to consumers. We measured 10 elements (including As, Cr, Hg) as well as carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) stable isotopes in 388 fish from 25 lake and river sites across this remote region. These data were used to determine the effect of: 1) trophic ecology; and 2) watershed geology on piscine elemental content. Overall, most element concentrations were low, often below provincial advisory benchmarks (ABs). However, traces of Hg, As, Cr, and selenium (Se) were detected in most fish. Based on their exceedance of their respective ABs, the most restrictive elements on fish consumption in these boreal systems were Hg > As > Cr. Arsenic and Se, but not Cr concentrations were related to fish size and trophic ecology (inferred from δ¹³C and δ¹⁵N), suggesting bioaccumulation of the former elements. Fish with enriched δ³⁴S values, suggestive of anadromous behaviour, had marginally lower Hg but higher Se concentrations. Modeling results suggested a strong effect of site-specific factors, though we found weak trends between piscine elemental content and geological features (e.g., mafic intrusions), potentially due to the broad spatial scale of this study. Results from this study address gaps in our understanding of As and Cr bioaccumulation and will help to inform fish consumption guidelines.

Perfluorooctane sulfonate (PFOS), a classic environmental pollutant, is reported to accumulate in brain and induce neurotoxicity. However, little is known the route and mechanism of its entrance in brain. In the present study, ICR mice were treated with PFOS for 28 days, the cerebral PFOS were measured and the morphological and ultrastructural changes of blood–brain barrier (BBB) were observed. Also, the expression and localization of the proteins related to the cerebral damages, tight junctions (TJs) and p38 activation were detected. Additionally, U87 cells were used to explore the role of p38 in PFOS-induced damages of astrocytes. PFOS significantly decreased the expression of TJ-related proteins (ZO-1, Claudin-5, Claudin-11, Occludin) in endothelial cells and disrupted BBB, which subsequently led PFOS to astrocytes and increased the expression of the proteins related to astrocytic damages (Aquaporin 4 and S100β). These results aggravated BBB disruption and further increased the cerebral PFOS levels. Besides, phosphorylated p38 activation was involved into PFOS-induced astrocytic damages in vivo and in vitro. In conclusion, the crosstalk between endothelial cells and astrocytes facilitated the BBB disruption and increased the accumulation of PFOS in brain. Our findings provided a new insight into the toxicological and physiological profiles of PFOS-induced neurotoxicity.

Coal mining activities may increase residential exposure to polycyclic aromatic hydrocarbons (PAHs), but personal PAH exposures have not been studied in mining areas. We used silicone wristbands as passive personal samplers to estimate PAH exposures in coal mining communities in Central Appalachia in the United States. Adults (N = 101) wore wristbands for one week; 51 resided in communities within approximately three miles of surface mining sites, and 50 resided 10 or more miles from mining sites. Passive indoor polyurethane foam (PUF) sampling was conducted in residents’ homes, and a sample of 16 outdoor PUF samples were also collected. Nine PAH congeners were commonly detected in wristbands (mean ± standard deviation), including phenanthrene (50.2 ± 68.7 ng/g), benz[a]anthracene (20.2 ± 58.2 ng/g), fluoranthene (19.4 ± 24.1 ng/g) and pyrene (15.2 ± 18.2 ng/g). Controlling for participant characteristics and season, participants living closer to mining sites had significantly higher levels of phenanthrene, fluorene, fluoranthene, pyrene and ∑PAHs in wristbands compared to participants living farther from mining. Indoor air showed no significant group differences except for pyrene, but outdoor air showed significant or marginally significant differences for phenanthrene, fluorene, pyrene and ∑PAHs. The results suggest that mining community residents face exposure to outdoor mining-related pollutants, and demonstrate that personal silicone wristbands can be deployed as effective passive sampling devices.

The increase of annual organic wastes generated worldwide has become a major problem for many countries since the mismanagement could bring about negative effects on the environment besides, being costly for an innocuous disposal. Recently, insect larvae have been investigated to valorize organic wastes. This entomoremediation approach is rising from the ability of the insect larvae to convert organic wastes into its biomass via assimilation process as catapulted by the natural demand to complete its lifecycle. Among the insect species, black soldier fly or Hermetia illucens is widely researched since the larvae can grow in various environments while being saprophagous in nature. Even though black soldier fly larvae (BSFL) can ingest various decay materials, some organic wastes such as sewage sludge or lignocellulosic wastes such as waste coconut endosperm are destitute of decent nutrients that could retard the BSFL growth. Hence, blending with nutrient-rich low-cost substrates such as palm kernel expeller, soybean curd residue, etc. is employed to fortify the nutritional contents of larval feeding substrates prior to administering to the BSFL. Alternatively, microbial fermentation can be adopted to breakdown the lignocellulosic wastes, exuding essential nutrients for growing BSFL. Upon reaching maturity, the BSFL can be harvested to serve as the protein and lipid feedstock. The larval protein can be made into insect meal for farmed animals, whilst the lipid source could be extracted and transesterified into larval biodiesel to cushion the global energy demands. Henceforth, this review presents the influence of various organic wastes introduced to feed BSFL, targeting to reduce wastes and producing biochemicals from mature larvae through entomoremediation. Modification of recalcitrant organic wastes via fermentation processes is also unveiled to ameliorate the BSFL growth. Lastly, the sustainable applications of harvested BSFL biomass are as well covered together with the immediate shortcomings that entail further researches.

Industrial dye effluents, which are a major wastage component that enter the natural environment, pose a significant health risk to human and aquatic life. Therefore, the effective removal of dye effluents is a major concern. Against this backdrop, in this study, a low-cost, earth-abundant, and ecofriendly ɤ-Fe₂O₃–PPy nanocomposite was prepared employing the conventional hydrothermal method. The morphology, functional groups, and elemental composition of ɤ-Fe₂O₃–PPy were characterized by XRD, SEM, XPS, and FTIR studies. Under optimized conditions, the prepared novel ɤ-Fe₂O₃–PPy nanocomposite showed a high methylene blue (MB) adsorption capacity of 464 mg/g, which is significantly higher than that of existing adsorbents such as CNTs and polymer-modified CNTs. The adsorption parameters such as pH, adsorbent dosage, and ionic strength were optimized to enhance the MB adsorption capacity. The adsorption results revealed that MB is adsorbed onto the adsorbent surface via electrostatic interactions, hydrogen bonding, and chemical binding interactions. In terms of practical application, the adsorbent’s adsorption–desorption ability in conjunction with magnetic separation was investigated; the prepared ɤ-Fe₂O₃–PPy nanocomposite exhibited excellent adsorption and desorption efficiencies over more than seven adsorption–desorption cycles.

Potential toxic metal(loid)s (PTMs) in road dust are a major concern in relation to urban environmental quality. Identifying pollution hotspots and sources of PTMs is an essential prerequisite for pollution control and management. Herein, the concentrations, pollution and potential health risks of 8 PTMs (As, Cd, Co, Cu, Hg, Mo, Pb and Zn) in road dust from the highly urbanized areas of Nanjing were studied. Spatial occurrences and sources of PTMs were explored using geostatistics, principal component analysis (PCA) and local Moran’s index. The contamination factor (CF) results showed that Co was mainly natural in origin, while the other PTMs were polluted, with average CFs ranging from 1.4 to 11.0 as follows: Hg > Mo > Cd > Cu > Pb > Zn > As, indicating moderate to very high contamination. Except for Co and Hg, the other PTMs were heavily loaded on PC1, which explained 44.72% of the total variance. Combining the statistical results and distributions of potential sources, we deduced that industrial emissions dominated the spatial patterns of all polluted PTMs in road dust, which showed high levels in the northern parts of the study region and generally decreasing levels southwards. Moreover, Pb and Zn in the south-central area and Cd in the north-central area displayed hotspots, with maximum CFs of 5.5 (Pb), 4.2 (Zn) and 16.2 (Cd), which were related to additional automotive and railway braking emissions, respectively. The resuspension of legacy pesticides in soil is likely responsible for the As pollution hotspot in the southwestern part. Despite the high anthropogenic contributions (27% for As and 68–88% for the other metals) to the PTMs in road dust, their noncarcinogenic and carcinogenic health risks were rarely found for children and adults based on the values of the hazard index and carcinogenic risk index. However, attention still should be paid to the pollution hotspots in the northern region.

Riparian areas are widely recognized as the main areas for carbon sequestration and nitrogen pollution removal, while little is known about the effects of the respective sand mining activities on riparian zones. In this study, the effects of sand mining activities on the soil organic carbon (SOC) storage, different N-removal processes (Feammox, anammox, and denitrification), and composition of the relative bacterial community at a depth of 0–40 cm were determined based on investigations in riparian sand mining areas and adjacent forestlands. The SOC density of the sand mining areas (2.59 t ha⁻¹, depth of 0–40 cm) was lower than that of the riparian forestlands (80.42 t ha⁻¹). Compared with those of the riparian forestland, the sand mining area exhibited a dramatic reduction in the CO₂-fixed gene abundances (cbbL) and a significant change in the composition of cbbL-containing bacteria. The rates of the Feammox (0.038 ± 0.014 mg N kg⁻¹ d⁻¹), anammox (0.017 ± 0.017 mg N kg⁻¹ d⁻¹), and denitrification (0.090 ± 0.1 mg N kg⁻¹ d⁻¹) processes at a depth of 0–20 cm in the soil layer of the sand mining area were reduced by 70.17%, 91.5%, and 93.62% compared with those of the riparian forestland, respectively. The riparian areas in the study area (approximately 12 ha, depth of 0–40 cm) destroyed by sand mining activities released approximately 933.96 t stored soil carbon, which reduce the annual carbon sequestration potential by 28.8–40.8 t. Moreover, the potential N-removal rates in the riparian forestlands (depth of 0–20 cm) by the Feammox, anammox, and denitrification processes were 1514.21–1530.95 kg N ha⁻¹ year⁻¹, whereas the potential N-removal rates in the sand mining area were only 121.2–126.19 kg N ha⁻¹ year⁻¹. Therefore, more investigations are necessary for comparing the benefits and damage of sand mining activities in riparian areas before more sand mining activities are approved.

Chromium has been proven to be extremely phytotoxic. This study explored the impacts of increasing Cr(VI) exposure (up to 10 mg L⁻¹ K₂Cr₂O₇) on the growth and development of alfalfa plants and adaptation responses employed, in an environmentally relevant context. The threshold concentration of K₂Cr₂O₇ in irrigation water beyond which stress responses are initiated is 1 mg L⁻¹. Lower Cr(VI) exposure (0.5 mg L⁻¹ K₂Cr₂O₇) induced hormesis, evident through increased biomass and larger leaves, likely mediated by increased NO content (supported by elevated NR enzymatic activity and overexpression of NR and ndh genes). Elevated Cr(VI) exposure (5 and 10 mg L⁻¹ K₂Cr₂O₇) resulted in reduced biomass and smaller leaves, and lower levels of photosynthetic pigment (10 mg L⁻¹ K₂Cr₂O₇). Higher levels of lipid peroxidation, H₂O₂ and NO contents in these plants suggested nitro-oxidative stress. Stress responses included increased SOD and CAT enzymatic activities, further supported to some extent by MnSOD, FeSOD, Cu/ZnSOD and CAT transcripts levels. GST7 and GST17 gene expression patterns, as well as proline content, P5CS enzymatic activity and corresponding P5CS and P5CR gene expression levels emphasized the role of proline and GSTs in the adaptation responses. Results highlight the importance of managing Cr(VI) levels in irrigation water.

Many remote montane ecosystems are experiencing biogeochemical changes driven by warming climate and atmospheric pollution. Compared with circumpolar and temperate lakes, the responses of subtropical montane lakes to these external stressors have been less investigated. Here we present sedimentary multi-proxies records (i.e. chironomids, elements and stable isotope of carbon and nitrogen) in ²¹⁰Pb-dated cores from two montane ponds (central China). Before the 1900s, low biomass and the dominance of opportunistic species (e.g. Chironomus anthracinus-type) in both ponds might be in response to cold and harsh condition. Thereafter, chironomid communities in both ponds experienced pronounced shifts. Nutrient-tolerant/warm-adapted species (e.g. Chironomus sp., Polypedilum nubeculosum-type and Endochironomus impar-type) proliferated and biomass increased synchronously after the 1900s, suggestive of favorable condition for chironomid growth. Redundancy analyses revealed that changes in chironomid communities in both ponds were significantly correlated with rising temperature and δ¹⁵N depletion. Prolonged growing season and nitrogen subsidy would increase primary productivity, and hence enhancing food availability for chironomids. Catchment-mediated indirect effects of warming and nitrogen deposition, such as hydrological changes and terrestrial organic matter inputs, would impose further influences on chironomid communities. Taken together, the combined effects of climate warming and nitrogen deposition have caused significant shifts in primary consumers of these montane ponds, and imposed cascading effects on structure and function of subtropical montane aquatic ecosystems.