Polycyclic aromatic hydrocarbons (PAHs) in soil can be recalcitrant to solvent extraction after aging. We showed in this study that mixing a small amount of water in the extracting solvent during microwave-assisted extraction (MAE) can release recalcitrant PAHs, resulting in significant improvement in the analyzed concentrations. The improvement factor (F) for the total of 16 priority PAHs (∑PAH16) listed by the United States Environmental Protection Agency was 1.44–1.55 for field soils. By comparing the F values for different soil organic components, we demonstrated that the recalcitrant PAHs were primarily associated with biochar, humic acid (HA), and humin (HM), with the F values for ∑PAH16 of 1.94, 6.62, and 4.59, respectively. The results showed that the recalcitrant PAHs comprised a sequestered fraction and a desorption-limited fraction. NMR spectra showed that water worked alone at elevated temperature to promote hydrolysis of biochar and destroy the macromolecular structure, thus causing the release of the otherwise sequestered PAHs during MAE. The substantial reduction in F values for HA and HM after demineralization indicated sequestration of PAHs in organic-mineral complexes, which can be destroyed by hot water treatment. The release of the sequestered fraction was nonselective and independent of compound hydrophobicity. In comparison, the release of the desorption-limited fraction was positively affected by the hydrophobicity of PAHs and was facilitated by the presence of water in the extracting solvent. The results of this study provide important insights into the sequestration and release of recalcitrant PAHs in soil.

There is increasing concern about the environmental behaviors of microplastics (MPs), in particular fine MPs (FMPs), such as their concentrations, sources, size distributions, and fragmentation by weathering in waters. However, there is little information about size distributions of MP polymer types and their relationships to their sources. Here, we analyzed concentrations, compositions, and size distributions of 18 polymer types of MPs of >20 μm by micro-Fourier transform infrared spectroscopy with a novel pretreatment method in surface waters at five sites from the headwaters to the mouth of a Japanese river, and in influent and effluent from a sewage treatment plant (STP). The microplastic concentrations ranged from 300 to 1240 particles/m³ in surface waters. Cluster analysis identified two primary sources of MPs: residential wastewater at the headwater site and non-point sources from urban areas at downstream sites; concentrations of chemical contaminants from STPs were much higher at the downstream sites. The median particle sizes (D₅₀) of MPs increased in urban areas at the downstream sites and were larger than those in influent and effluent. These results imply the release of larger MPs from non-point sources in urban areas. The size distributions of each polymer and all MPs could be fitted significantly to the Weibull distribution function. Values of D₅₀, shape parameters, and scale parameters estimated from the functions were useful indicators for evaluating size distributions in detail. A significant positive correlation of D₅₀ with the tensile strengths of virgin polymers among 13 dominant polymers detected in the surface water suggests that the fragmentation properties of each polymer are influenced by its physical strength. Multidimensional analysis with concentrations, polymeric compositions, and size distributions of MPs, including FMPs, could provide useful information about their sources and their environmental behaviors.

Breast milk is a unique biological sample that reflects the exposure levels of both lactating mothers and infants. The exposure levels of BPA due to breast milk consumption for infants can be estimated easily, but the method to estimate the total daily intake (TDI) of lactating mothers from breast milk has not yet been established. In this study, BPA concentrations were detected in breast milk samples from 149 lactating mothers from Hunan, China. The median concentration of BPA in breast milk was 0.053 μg/L with a range of 0.001–2.535 μg/L, and a temporal decline trend was found for BPA concentrations in breast milk (p < 0.05). The median intake of BPA via breast milk was 26.8 ng/kg bw/day for 0-3-month-old infants and 7.0 ng/kg bw/day for 4-12-month-old infants. Based on the predicted concentrations of BPA in urine and blood via the conversion coefficients from breast milk, the TDIs of lactating mothers were estimated. The TDIs estimated from the simulated urine concentration were 84.0 ± 175.2 ng/kg bw/day for 0-3-month-old infants' mothers and 36.9 ± 80.8 ng/kg bw/day for 4-12-month-old infants' mothers. The dietary daily intakes estimated from the simulated blood concentration were 579.6 ± 370.8 ng/kg bw/day for 0-3-month-old infants' mothers and 280.1 ± 195.2 ng/kg bw/day for 4-12-month-old infants’ mothers. When assuming the dietary daily intakes in Hunan of the fifth total diet study (TDS) as the “true” total dietary intake of our population, the contribution of diet was estimated to be 63.7%, which suggested that non-dietary BPA exposure may be underestimated.

Arsenic is a potent toxicant, and long-term exposure to inorganic arsenic causes lung damage. M2 macrophages play an important role in the pathogenesis of pulmonary fibrosis. However, the potential connections between arsenic and M2 macrophages in the development of pulmonary fibrosis are elusive. C57BL/6 mice were fed with drinking water containing 0, 10 and 20 ppm arsenite for 12 months. We have found that, in lung tissues of mice, arsenite, a biologically active form of arsenic, elevated H19, c-Myc, and Arg1; decreased let-7a; and caused pulmonary fibrosis. For THP-1 macrophages (THP-M) and bone-marrow-derived macrophages (BMDMs), 8 μM arsenite increased H19, c-Myc, and Arg1; decreased let-7a; and induced M2 polarization of macrophages, which caused secretion of the fibrogenic cytokine, TGF-β1. Down-regulation of H19 or up-regulation of let-7a reversed the arsenite-induced M2 polarization of macrophages. Arsenite-treated THP-M and BMDMs co-cultured with MRC-5 cells or primary lung fibroblasts (PLFs) elevated levels of p-SMAD2/3, SMAD4, α-SMA, and collagen I in lung fibroblasts and resulted in the activation of lung fibroblasts. Knockout of H19 or up-regulation of let-7a in macrophages reversed the effects. The results indicated that H19 functioned as an miRNA sponge for let-7a, which was involved in arsenite-induced M2 polarization of macrophages and induced the myofibroblast differentiation phenotype by regulation of c-Myc. In the sera of arseniasis patients, levels of hydroxyproline and H19 were higher, and levels of let-7a were lower than levels in the controls. These observations elucidate a possible mechanism for arsenic exposure-induced pulmonary fibrosis.

The importance of hydrochar properties for soil application is well known, but the effects of natural aging on hydrochar properties remain ambiguous. The present study aimed to determine the shift patterns in the physicochemical properties of hydrochar through a 16-month soil column aging experiment conducted in a rice-wheat rotation system with hydrochars derived from a wheat straw at 220 °C and 260 °C. Obvious decreasing hydrophilic/polarity indices and increasing porosity, ash content, and stability occurred in aged hyrdrochar, which were due to the dissolved organic matter (DOM) leaching and the interaction with mineral content and fertilizer during the 16-month aging process. Besides, fewer C–OH, slightly more CO, and higher aromaticity (C–C/CC) in aged hydrochar were observed. Meanwhile, the relative abundance of the compounds containing only C, H, and O atoms in water extract of aged hydrochar decreased, while that of the compounds containing C, H, O, and N atoms increased during aging; these findings were attributed to the less labile DOM and microbial degradation and the retention of some plant-derived dissolved organic carbon, respectively. This study provided 16-month aging characterization data regarding alteration in hydrochar physicochemical properties, which was conducive to make a better understanding of the use of hydrochars as sustainable soil amendments from agroecosystems and environmental perspective.

The incidence of thyroid cancer (TC) has increased rapidly worldwide in recent years. Exposure to endocrine disruptors can affect thyroid hormones and is probably carcinogenic to humans. The effects of polybrominated diphenyl ethers (PBDEs), some heavy metals (Cd, Pb, As and Hg) on risk of TC have been rarely reported. Hence, we aimed to examine the associations of TC risk with exposure to PBDEs and four heavy metals. This case-control study involved 308 TC cases and 308 age- and sex-matched controls. Plasma PBDEs concentrations were determined by gas chromatograph-mass spectrometry. Concentrations of heavy metals concentrations in urine specimens were detected by graphite furnace atomic absorption spectrometry or inductively coupled plasma optical emission spectrometry. Conditional logistic regression models were used to explore associations of PBDEs and 4 heavy metals exposures with TC risk. A joint-effect interaction term was inserted into the logistic regression models to assess the multiplicative interaction effects of PBDEs-heavy metals on TC risk. Some PBDE congeners (BDE-028, -047, −099, −183, −209) were positively correlated with TC risk. As and Hg were also associated with the increased TC risk. Compared with low exposure levels, participants with high exposure levels of As and Hg were 5.35 and 2.98 times more likely to have TC, respectively. Co-exposure to BDE-209 and Pb had a negative interaction effect on TC risk. Some PBDE congeners (e.g. BDE-028, -047, −209) and Hg had a significant positive interaction effect on the risk of TC. The joint exposure of BDE-183 and Hg showed a negative interaction effect on TC risk, but the corresponding OR value was still statistically significant. Exposure to PBDEs, As and Hg may be associated with TC development. Joint exposure to PBDEs and Pb or Hg has interaction effects on TC risk. Further prospective research with large sample is required to confirm these findings.

Heavy metal pollution in soil around abandoned mine sites is one of the most critical environmental issues worldwide. Soil microbes form complex communities and perform ecological functions individually or in cooperation with other organisms to adapt to harsh environments. In this study, we investigated the distribution patterns of bacterial and fungal communities in non-contaminated and heavy metal-contaminated soil of the abandoned Samkwang mine in Korea to explore microbial interaction mechanisms and their modular structures. As expected, the bacterial and fungal community structures showed large differences depending on the degree of heavy metal contamination. The microbial network was divided into three modules based on the levels of heavy metal pollution: heavy metal-tolerant (HM-Tol), heavy metal-mid-tolerant (HM-mTol), and heavy metal-sensitive (HM-Sens) modules. Taxonomically, microbes assigned to Vicinamibacterales, Pedosphaeraceae, Nitrosomonadaceae, and Gemmatimonadales were the major groups constituting the HM-Tol module. Among the detected heavy metals (As, Pb, Cd, Cu, and Zn), copper concentrations played a key role in the formation of the HM-Tol module. In addition, filamentous fungi (Fusarium and Mortierella) showed potential interactions with bacteria (Nitrosomonadaceae) that could contribute to module stability in heavy metal-contaminated areas. Overall, heavy metal contamination was accompanied by distinct microbial communities, which could participate in the bioremediation of heavy metals. Analysis of the microbial interactions among bacteria and fungi in the presence of heavy metals could provide fundamental information for developing bioremediation mechanisms for the recovery of heavy metal-contaminated soil.

Air pollution is a major global public health problem. The situation is most severe in low- and middle-income countries, where pollution control measures and monitoring systems are largely lacking. Data to quantify the exposure to air pollution in low-income settings are scarce.In this study, land use regression models (LUR) were developed to predict the outdoor nitrogen dioxide (NO₂) concentration in the study area of the Western Region Birth Cohort in São Paulo. NO₂ measurements were performed for one week in winter and summer at eighty locations. Additionally, weekly measurements at one regional background location were performed over a full one-year period to create an annual prediction.Three LUR models were developed (annual, summer, winter) by using a supervised stepwise linear regression method. The winter, summer and annual models explained 52 %, 75 % and 66 % of the variance (R²) respectively. Cross-holdout validation tests suggest robust models. NO₂ levels ranged from 43.2 μg/m³ to 93.4 μg/m³ in the winter and between 28.1 μg/m³ and 72.8 μg/m³ in summer. Based on our annual prediction, about 67 % of the population living in the study area is exposed to NO₂ values over the WHO suggested annual guideline of 40 μg/m³ annual average.In this study we were able to develop robust models to predict NO₂ residential exposure. We could show that average measures, and therefore the predictions of NO₂, in such a complex urban area are substantially high and that a major variability within the area and especially within the season is present. These findings also suggest that in general a high proportion of the population is exposed to high NO₂ levels.

Biodegradation is responsible for most contaminant removal in plumes of organic compounds and is fastest at the plume fringe where microbial cell numbers and activity are highest. As the plume migrates from the source, groundwater containing the contaminants and planktonic microbial community encounters uncontaminated substrata on which an attached community subsequently develops. While attached microbial communities are important for biodegradation, the time needed for their establishment, their relationship with the planktonic community and the processes controlling their development are not well understood. We compare the dynamics of development of attached microbial communities on sterile substrata in the field and laboratory microcosms, sampled simultaneously at intervals over two years. We show that attached microbial cell numbers increased rapidly and stabilised after similar periods of incubation (∼100 days) in both field and microcosm experiments. These timescales were similar even though variation in the contaminant source evident in the field was absent in microcosm studies, implying that this period was an emergent property of the attached microbial community. 16S rRNA gene sequencing showed that attached and planktonic communities differed markedly, with many attached organisms strongly preferring attachment. Successional processes were evident, both in community diversity indices and from community network analysis. Community development was governed by both deterministic and stochastic processes and was related to the predilection of community members for different lifestyles and the geochemical environment.