Benzo[a]pyrene (BaP), a widely existed polycyclic aromatic hydrocarbon pollutant in aquatic environment, has toxic effects on marine animals and their generations, but the intergenerational immunotoxic mechanism underlying has not been clearly understood. In the study, the offspring of marine medaka (oryzias melastigma) which were exposed to 0.5 μg L⁻¹ BaP suffered from circadian rhythm oscillation disorders and severe DNA damage. Many clock-associated genes like per1 were significantly modulated in offspring, both per1 and p53 were significantly inhibited that altered the progression of cell cycle and inhibited DNA repair, which possibly resulted in the increased mortality of offspring. The hypermethylation of the per1 promotor and abnormal levels of N⁶-methyladenosine (m⁶A) suggested that the underlying mechanism was probably related to the epigenetic modification. Moreover, the offspring from paternal BaP exposure had more severe DNA damage and a higher degree of hypermethylation than those from maternal exposure. F1 larvae from BaP-exposed parents were more sensitive to BaP exposure, showing that the expression of immune and metabolism-related genes were significantly up-regulated. Taken together, the parental toxicity induced by BaP could be passed to F1 generation and the mechanism underlying was probably associated with a characteristic circadian rhythm disorder.

Nitrogen dioxide (NO₂) is a well-established traffic emissions tracer and has been associated with multiple adverse health outcomes. Short- and long-term exposure to NO₂ has been studied and is well-documented in existing literature, but information on intermediate-term NO₂ effects and mortality is lacking, despite biological plausibility. We obtained daily NO₂ and mortality data from 42 counties in China from 2013 to 2015. Distributed-lag non-linear models were employed to investigate the relationship between non-accidental mortality and NO₂ up to 30 days before the event, including PM₂.₅, temperature, relative humidity, and holidays as covariates in a random effects meta-analysis pooling county-specific estimates. We repeated the analysis for cardiovascular- and respiratory-related mortality, and explored sex-stratified associations. Per 10 μg/m³ increase in NO₂, we estimated a 0.13% (95%CI: 0.03, 0.23%), 0.57% (95%CI: −0.04, 1.18%), and −0.14% (95%CI: −1.63, 1.37%) change in non-accidental mortality for same-day and previous-day NO₂ (lag0-1 cumulated), in the preceding 7 days (lag0-7 cumulated), and in the preceding 30 days (lag0-30 cumulated), respectively. The strongest estimate was observed for respiratory-related mortality in the lag0-30 cumulated effect for women (3.12%; 95%CI: −1.66, 8.13%). We observed a trend of higher effect estimates of intermediate-term NO₂ exposure on respiratory mortality compared to that of the short-term, although the differences were not statistically significant. Our results at longer lags for all-cause and cardiovascular mortality were sensitive to modeling choices. Future work should further investigate intermediate-term air pollution exposure given their potential biological relevance, but in larger scale settings.

Paddy soils around mining areas suffer from the great threat of heavy metal pollution. The traditional source-tracing methods based on metal concentrations limit our ability to quantify the sources of heavy metals and trace their transport processes to paddy soils. In this study, Zn isotope compositions of paddy soils in Dabaoshan mine area, a typical sulfide deposit in southern China, have been systematically studied. According to a plot between 1/Zn (i.e. inverse concentration) and δ⁶⁶Zn value, all the polluted paddy soils fall on the mixing line between acid mine drainage precipitate (AMD-precipitate) and fertilizer while the unpolluted paddy soil falls on the mixing line between fertilizer and bedrock. This indicates the mixing of Zn sources at least three end-members: the mining end-member (i.e. AMD-precipitate), the agricultural end-member (i.e. fertilizer), and bedrock whose geochemical signature is often overprinted by the former two sources around the mining area. The quantitative calculations to apportion the end-member’s contributions show that the mining activity contributes most Zn in the paddy soils with an average of ∼66.2%. The contribution of mining activities has significant spatial variations. Specifically, the mining activities have relatively low impacts on the lower reach and the deep soil. Additionally, the apparent Zn isotope fractionation between AMD and AMD-precipitate (Δ⁶⁶ZnAMD₋ₚᵣₑcᵢₚᵢₜₐₜₑ − AMD of −0.35 to −0.08‰) in the tailings dam suggests that Zn cations in AMD coprecipitated with the secondary Fe-bearing minerals (e.g. jarosite and goethite). After being discharged from the tailings dam, Zn is mainly carried by the Fe-oxide minerals and migrated during surface runoff. Our study highlights the contribution of human activities to the Zn pollution in the paddy soils and the key role of Fe-bearing minerals in the migration of Zn. These findings provide a scientific base for the development of policy for pollution control in mining-affected region.

We propose a methodology to estimate single and multiple emission sources of atmospheric contaminants. It combines hybrid metaheuristic/gradient-descent optimization techniques and Tikhonov-type regularization. The dispersion problem is solved by the Galerkin/Least-squares finite element formulation, which allows more realistic modeling. The accuracy of the proposed inversion model is tested under different contexts with experimental data. To identify single and multiple emissions, we use experimental field data. We consider different configurations for both the Tikhonov-type functional and optimization techniques. Several single and composite data misfit functions are tested. We also use a discrepancy-based choice rule for the regularization parameter. The resulting inversion tool is highly versatile and presents accurate results under different contexts with a competitive computational cost.

Parabens are class of preservatives used in vast majority of commercial products, and a potential Endocrine Disrupting Chemical (EDC). The present study was undertaken to delineate the effects of n-butylparaben on F1 male progeny exposed maternally through gestation and lactation via subcutaneous route. The F0 dams were given subcutaneous injections of n-butylparaben from gestation day (GD) 6 to postnatal day (PND) 21 with doses of 10, 100, 1000 mg/kg Bw/day in corn oil. The F1 male rats were monitored for pubertal development and sexual maturation; these were sacrificed on PND 30, 45 and 75. On PND 75, these F1 male rats were subjected for fertility assessment with unexposed female rats.A delayed testicular descent at 100 and 1000 mg/kg Bw dose and delayed preputial separation at 10 mg/kg Bw dose was observed in exposed F1 male rats. Decreased sperm count, motility and Daily Sperm Production was observed at 100 mg/kg Bw dose at PND 75. Interestingly, the sperm transit time in the epididymis was accelerated at this dose. Significant perturbed testicular expression of steroid receptors (ERα and β, AR), INSL3 and StAR genes with increased T and LH levels indicates direct effect on spermatogenesis and steroidogenesis. These F1 generation adult rats were sub-fertile with increased (%) pre- and post-implantation loss at 100 and 1000 mg/kg Bw/day dose. This is the first report on n-butylparaben highlighting the involvement of testicular leydig cells with accelerated sperm transit time leading to reduced fertility in the maternally exposed F1 male rats through estrogenic/anti-androgenic action.

Light absorbing carbonaceous aerosols (LACA) consisting of black carbon (BC) and brown carbon (BrC) have received considerable attention because of their climate and health implications, but their sources, characteristics and fates remain unclear in Southeast Asia (SEA). In this study, we investigated spatio-temporal characteristics of LACA, their radiative properties and potential sources in Singapore under different weather conditions. Hourly BC concentrations, measured from May 2017 to March 2018, ranged from 0.31 μg/m³ to 14.37 μg/m³ with the mean value being 2.44 ± 1.51 μg/m³. High mass concentrations of BC were observed during the south-west monsoon (SWM, 2.60 ± 1.56 μg/m³) while relatively low mass concentrations were recorded during the north-east monsoon (NEM, 1.68 ± 0.96 μg/m³). There was a shift in the Absorption Ångström exponent (AAE) from 1.1 to 1.4 when the origin of LACA changed from fossil fuel (FF) to biomass burning (BB) combustion. This shift is attributed to the presence of secondary BrC in LACA, derived from transboundary BB emissions during the SWM. Lower AAE values were observed when local traffic emissions were dominant during the NEM. This explanation is supported by measurements of water-soluble organic carbon (WSOC) in LACA and the corresponding AAE values determined at 365 nm using a UV–vis spectrophotometer. The AAE values, indicative of the presence of brown carbon (BrC), showed that photochemically aged LACA contribute to an enhancement in the light absorption of aerosols. In addition, spatio-temporal characteristics of BC in the intra-urban environment of Singapore were investigated across diverse outdoor and indoor microenvironments. High variability of BC was evident across these microenvironments. Several air pollution hotspots with elevated BC concentrations were identified. Overall, the results stress a need to control anthropogenic emissions of BC and BrC in order to mitigate near-term climate change impacts and provide health benefits.

CH₄ oxidation in landfill cover soils plays a significant role in mitigating CH₄ release to the atmosphere. Oxygen availability and the presence of co-contaminants are potentially important factors affecting CH₄ oxidation rate and the fate of CH₄-derived carbon. In this study, microbial populations that oxidize CH₄ and the subsequent conversion of CH₄-derived carbon into CO₂, soil organic C and biomass C were investigated in landfill cover soils at two O₂ tensions, i.e., O₂ concentrations of 21% (“sufficient”) and 2.5% (“limited”) with and without toluene. CH₄-derived carbon was primarily converted into CO₂ and soil organic C in the landfill cover soils, accounting for more than 80% of CH₄ oxidized. Under the O₂-sufficient condition, 52.9%–59.6% of CH₄-derived carbon was converted into CO₂ (CECO₂₋C), and 29.1%–39.3% was converted into soil organic C (CEₒᵣgₐₙᵢc₋C). A higher CEₒᵣgₐₙᵢc₋C and lower CECO₂₋C occurred in the O₂-limited environment, relative to the O₂-sufficient condition. With the addition of toluene, the carbon conversion efficiency of CH₄ into biomass C and organic C increased slightly, especially in the O₂-limited environment. A more complex microbial network was involved in CH₄ assimilation in the O₂-limited environment than under the O₂-sufficient condition. DNA-based stable isotope probing of the community with ¹³CH₄ revealed that Methylocaldum and Methylosarcina had a higher relative growth rate than other type I methanotrophs in the landfill cover soils, especially at the low O₂ concentration, while Methylosinus was more abundant in the treatment with both the high O₂ concentration and toluene. These results indicated that O₂-limited environments could prompt more CH₄-derived carbon to be deposited into soils in the form of biomass C and organic C, thereby enhancing the contribution of CH₄-derived carbon to soil community biomass and functionality of landfill cover soils (i.e. reduction of CO₂ emission).

This paper reports polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F) and polychlorinated biphenyls (PCB) concentrations in sediment and fish collected from Polish rivers in agricultural and urban areas and the associated risk for fish consumers. Total TEQ concentrations in fish muscles were in the range 0.29–7.25 pg WHO-TEQ g⁻¹ wet weight (w.w.). Generally, levels in sediment and fish muscles were low except for in the Vistula River in Cracow. In this fishery, total TEQ concentrations in sediments were high at 7.84 ± 1.73 pg WHO-TEQ g⁻¹ dry matter and fish were non-compliant with Commission Regulation (EU) 1259/2011/EU (3.5 pg WHO-TEQ g⁻¹ w.w. for PCDD/F and 6.5 pg WHO-TEQ g⁻¹ w.w. for total TEQ). Dioxin congener profiles in sediments were dominated by OCDD, and in the most contaminated fisheries in Cracow additionally by OCDF and 1,2,3,4,7,8-HxCDF. The most accumulated PCDD/Fs congeners in fish were 2,3,7,8-TCDF and 2,3,4,7,8-PeCDF except in Cracow, where 1,2,3,4,7,8-HxCDF dominated. The most abundant dioxin-like PCB (DL-PCB) and non-dioxin-like PCB (NDL-PCB) congeners were PCB 118 and PCB 153, respectively, both in sediment and fish muscles. The levels and profiles of contaminants in fish reflected the pollution of their environment. To characterize the potential health risk associated with dioxin and DL-PCB intake, doses ingested in two 100g portions of fish by adults and children were calculated and expressed as percentages of Tolerable Weekly Intake (TWI). Both values of TWI – that of 14 pg WHO-TEQ kg⁻¹ b.w. and the newer value of 2 pg WHO-TEQ kg⁻¹ b.w. established by the EFSA in November 2018 – were taken into account.It appears that regular consumption of some species could pose a health risk, especially those from urban areas.

Most aquatic systems show characteristic seasonal fluctuations in the total nutrient pool supporting primary productivity. The nutrient dynamics essentially exacerbate critical demand for the counterpart micronutrients towards achieving ecosystem equilibrium. Herein, the phytoplankton demand for iron (Fe) uptake under high concentration of nitrate-nitrogen during spring in Xiangxi Bay, China, was studied. Our result confirmed that significant Fe concentrations (P = 0.01) in both autumn (0.62 ± 0.02 mgL⁻¹) and winter (0.06 ± 0.03 mgL⁻¹) relative to spring (0.004 ± 0.01 mgL⁻¹) are linked to the low NO₃⁻N paradigms during autumn and winter. As NO₃⁻N showed a sharp increase in spring, a dramatic reduction in the Fe pool was observed in the entire tributary, driving the system to a critical Fe limited condition. Bioassay study involving Fe additions both alone and in combinations led to maximum growth stimulation with biomass as chla (16.44 ± 0.82 μgL⁻¹) and phytoplankton cell density (6.75 × 10⁶ cellsL⁻¹) which differed significantly (P = 0.03) with the control. Further, the study demonstrated that Fe additions triggered biomass productions which increased linearly with cell densities. The P alone addition caused biomass production (15.26 ± 2.51 μgL⁻¹) greater than both NO₃⁻N (9.15 ± 0.66 μgL⁻¹) and NH₄⁺N (13.65 ± 1.68 μgL⁻¹) separate additions but reported a low aggregate cell density (3.18 × 10⁶ cellsL⁻¹). This indicates that nutrient and taxonomic characteristics e.g., high cell pigment contents rather than just the cell bio-volume also determine biomass. The Bacilliarophyta, Chlorophyta, and Cryptophyta with the total extinction of Cyanophyta characterized the bloom in spring. The anthropogenic NO₃⁻N input into XXB would have driven to higher NO₃⁻N than NH₄⁺N situation, and incapacitated the Cyanophyta that preferentially utilize NH₄⁺N. Our study provides a useful report for incorporation into the monitoring programs for prudent management of phytoplankton bloom and pollution across the eutrophic systems.

Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ⁵³Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ⁵³Crₐᵤₜₕ) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ⁵³Crₐᵤₜₕ value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ⁵³Crₐᵤₜₕ values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%–55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ⁵³Crₐᵤₜₕ values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ⁵³Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.