This work investigates the absorption properties of soluble brown carbon (BrC), extracted in methanol and water, from ambient aerosol (PM₁₀) samples, collected over an urban background site in Mumbai, India. The diurnal variability was investigated in samples collected in the morning (7–11 a.m.) and afternoon (12–4 p.m.) periods. Absorption properties of BrC (in the 300–600-nm wavelength range) were measured in filter extracts of water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MSOC). WSOC and MSOC accounted for on average 52% and 77%, respectively, of the measured OC, potentially indicating unextracted BrC and rendering these values the lower bound. Compared with afternoon samples, the morning samples of MSOC and WSOC had increased BrC concentrations and absorption coefficients (bₐbₛ365; 40%–65%). The correlation between bₐbₛ365 and EC, ns-K⁺, and NO₃⁻ in the morning samples indicated contributions from primary sources, including both biomass and vehicular sources. The decreased bₐbₛ365 in the afternoon samples was partly explained by mixing layer dilution, accompanied by a reduction in the concentrations of primary aerosol constituents. Furthermore, in the afternoon samples, ¹HNMR spectroscopy revealed the presence of more oxidized functional groups and significantly higher OC/EC and WSOC/OC ratios, indicating the greater aging of afternoon aerosol. The MAC₃₆₅ (m²gC⁻¹) for both WSOC and MSOC extracts decreased significantly by 20%–34% in the afternoon samples compared with the morning samples, indicating degradation in the absorption properties of the particles and potentially a change in the constituent BrC chromophores.

Useful information on the potential radon risk in existing buildings can be obtained by combining data from sources such as potential risk maps, the ‘Sistema de Información sobre Ocupación del Suelo de España’ (SIOSE) [information system on land occupancy in Spain], cadastral data on built property and population surveys. The present study proposes a method for identifying urban land, premises and individuals potentially subject to radon risk. The procedure draws from geographic information systems (GIS) pooled at the municipal scale and data on buildings possibly affected. The method quantifies the magnitude of the problem in the form of indicators on the buildings, number of premises and gross floor area that may be affected in each risk category. The findings are classified by type of use: residential, educational or office. That information may guide health/prevention policies by targeting areas to be measured based on risk category, or protection policies geared to the construction industry by estimating the number of buildings in need of treatment or remediation. Application of the methodology to Greater Madrid showed that 47% of the municipalities have houses located in high radon risk areas. Using cadastral data to zoom in on those at highest risk yielded information on the floor area of the vulnerable (basement, ground and first storey) premises, which could then be compared to the total. In small towns, the area affected differed only scantly from the total, given the substantial proportion of low-rise buildings in such municipalities.

Atmospheric particulate matter (PM) pollution levels and human health risks resulting from exposure to non-anthropogenic pollution sources, such as coal mine-fires, are serious global issues. The toxicity of PM₁₀-bound metals and polycyclic aromatic hydrocarbons (PAHs) was assessed according to their non-cancer and cancer risks (CRs) at the mine-fire and in an adjacent city area. Health risks were estimated for inhalation, ingestion, and dermal absorption pathways. The non-cancer risks, presented in terms of the hazard index (HI) and hazard quotient (HQ), were found to be significant (>1) at all locations, except in the mining (for HQ-dermal) and city background area (for HQ-ingestion and HQ-dermal) in children and adults, respectively. The total CR was estimated to be highest at the city nearby the mine-fire area (3.31E-02 and 1.93E-02) followed by the mine-fire area (2.66E-02 and 1.71E-02) for children and adults, respectively. The total CR and CR via individual exposure routes were estimated to be in the high risk (10⁻³ ≤ CR < 10⁻¹) category at the mine-fire site and adjacent city area. For all exposures, CR levels were calculated to be higher than the acceptable range (from 1.00E-06 to 1.00E-04), except for the CR-inhalation level at the A5 location. Among all elements, Cd and BaPₑqᵤ were more significant for the CR at the coal mine-fire and the adjacent city area. Hence, this study concluded that non-anthropogenic sources, such as coal mine-fires, could be part for the significant health risk (carcinogenic and non-carcinogenic) levels in the study area.

Ecotoxicological studies show the association between pesticide pollution and transgenerational toxicity in aquatic organisms. However, a less considered risk is that many pesticides can be metabolized and transferred to offspring as new toxicants. In this study, we used zebrafish to evaluate the maternal transfer risk of fipronil (FIP), which is a great threat to aquatic organisms with toxic metabolite formation. After 28-day exposure to environmentally relevant concentrations (1.0, 5.0 and 10.0 μg/L) of FIP in adult female zebrafish (F0), the toxicants off-loading and transgenerational toxicity in offspring were studied. High burdens of FIP and its sulfone metabolite were found in both F0 and the embryos (F1), resulting in increased CYP450 activity. The residual levels of the metabolite were higher than those of the parent compound. Chiral analysis further showed a preferential accumulation of S-enantiomer of FIP in both F0 and F1. Maternal exposure to FIP increased the malformation rate and decreased the swim speed in larvae. Additionally, after exposure, the levels of thyroid hormones (THs), including triiodothyronine (T3) and thyroxine (T4), decreased in both generations, particularly in the F1. Gene transcription expression along the hypothalamic-pituitary-thyroid (HPT) axis was also significantly affected. Maternal exposure to FIP increased sulfone metabolite enrichment and cause multiple toxic effects in F1. Findings from this study highlight the key role of biologically active product formation in the maternal transfer of pollutants and associated risk assessment.

Phagocytosis suppression induced by nanoparticles (NPs) exposure is increasingly reported in marine species. However, the mechanisms underlying this impact remain poorly understood. In order to improve our present understanding of the immunotoxicity of NPs, acute (96 h) TiO2 NP exposure and rescue trials via exogenous supply of Ca2+ were performed in the blood clam, Tegillarca granosa. The results show that the phagocytosis rate, cell viability, and intracellular Ca2+ concentration of haemocytes were significantly suppressed, whereas the intracellular ROS concentration of haemocytes significantly increased upon nTiO2 exposure. Exposure to nTiO2 also led to the significant downregulation of Caspase-3, Caspase-6, apoptosis regulator Bcl-2, Bcl-2-associated X, calmodulin kinase II, and calmodulin kinase kinase II. Furthermore, the toxic impacts of nTiO2 were partially mitigated by the addition of exogenous Ca2+, as indicated by the recovery tendency in almost all the measured parameters. The present study indicates that Ca2+ signaling could be one of the key pathways through which nTiO2 attacks phagocytosis.

Nitrogen (N) addition can change physicochemical properties and biogeochemical processes in soil, but whether or not these changes further affect the transport and transformation of heavy metal speciation is unknown. Here, a long-term (2004–2016) field experiment was conducted to assess the responses of different heavy metal speciation in three soil aggregate fractions to N additions in a temperate agroecosystem of North China. The organic matter turnover time was quantified based on changes in δ13C following the conversion from C3 (wheat) to C4 crop (corn). Averagely, N addition decreases and increases the heavy metal contents in bioavailable and organic bound fractions by 27.5% and 16.6%, respectively, suggesting N addition promotes the transformation of heavy metal speciation from bioavailable to organic bound, and such a promotion in a small aggregate fraction is more remarkable than that in a large aggregate fraction. The transformations of heavy metal speciation from bioavailable to organic bound in all soil aggregate fractions are largely dependent on the increments in the turnover time of organic matter. The increase in organic matter turnover time induced by N addition may inhibit the desorption of heavy metals from organic matter by prolonging the interaction time between heavy metals and organic matter and enhance the capacity of organic matter to adsorb heavy metals by increasing the humification degree and functional group. Our work can provide insights into the accumulation, migration, and transformation of heavy metals in soils in the context of increasing global soil N input from a microenvironmental perspective.

In this study, data collected from an urban air quality monitoring network are being used for the purpose of evaluating various methodologies used for spatial interpolation in the context of proposing an effective yet simple to apply scheme for PM spatial point estimations. The examined methods are the Inverse Distance Weighting, two linear regression models, the Multiple Linear Regression and the Linear Mixed Model, along with a Feed Forward Neural Network (FFNN) model. These schemes utilize daily PM₁₀ and PM₂.₅ concentrations collected from five and three air quality monitoring sites respectively. In order to obtain the resulted estimations, the leave-one-out cross-validation methodology is used for all methods. The evaluation of their predictive ability is performed by using a combination of difference and correlation statistical measures, scatter plots and statistical tests. The results indicate the usefulness of FFNNs as they are found to be statistically significantly superior for modelling the particulate matter spatial variability. The model performance statistics show that in most cases the error values are considerably lower for the FFNN model. Additionally, the rank and Wilcoxon rank tests reveal that the null hypothesis for equal predictive accuracy is rejected for the majority of monitoring sites and schemes (values lower than the critical t-value). According to the comparison results, the FFNN model is selected for forecasting air quality limit exceedances set by the European Union and World Health Organization air quality standards. For two monitoring sites in which the largest number of exceedances occurred, the probability of detection is high while the probability of false detection is very low, further establishing the neural networks’ predictive ability.

Struvite recovered from swine wastewater can be used as a good slow release fertilizer. Nevertheless, the presence of heavy metals would be easily precipitated with struvite and increase the ecological risk for its agricultural use. This paper investigated the possibility of using process variables for heavy metal (Cu2+, Zn2+ and Cr3+) minimization during struvite crystallization in swine wastewater. The heavy metal content, effect ratios (ER) of the citric acid concentration under varying conditions were tested and their SEM, EDS and XRD patterns were compared for morphology analysis. The results show that an increase in pH decreased the content of Cu, Zn and Cr in recovered precipitates. Heavy metal content in the precipitates increased markedly with their initial concentrations in the solution. The effect ratio calculation indicates that Cr has the strongest co-precipitation potential, followed by Zn and Cu. An increase in citric acid concentration reduced the heavy metal removal efficiency (14.3, 27.7 and 28.1% for Cu, Zn and Cr, respectively) but did not decrease their content in struvite precipitates. What is more, increase of total ammonia nitrogen (TAN) to soluble phosphate molar ratio significantly decreased Cu, Zn removal efficiency (52.2 and 50% respectively), while Mg:PO4P molar ratio had much less effect.

A nationwide survey, including 75 sludge samples and 18 wastewater samples taken from different wastewater treatment plants (WWTPs) from 23 cities, was carried out to investigate the occurrence and composition profiles of polycyclic aromatic hydrocarbons (PAHs) in China. In total, the concentrations of ∑16PAHs in sludge ranged from 565 to 280,000 ng/g (mean: 9340 ng/g) which was at a moderate level in the world. The composition profiles of PAHs were characterized by 3- and 4-ring PAHs in textile dyeing sludge and 4- and 5-ring PAHs in domestic sludge. Significant variations in regional distribution of PAHs were observed. Both the principal components analysis and diagnostic ratios revealed that vehicle exhaust, coal and natural gas combustion were the main sources of PAHs in China. The estimated concentrations of PAHs were 3820 ng/L and 1120 ng/L in influents and effluents of the WWTPs, respectively. The high toxic equivalent quantity (TEQ) values of PAHs are ascribed to the high PAH levels. Risk quotient values (RQs) in sludge indicated that there was low potential risk to soil ecosystem after sludge had been applied one year except for indeno [1,2,3-cd]pyrene (IcdP) detected in Huaibei, Anhui province.

There are global concerns about heavy metal (HM) contamination in soils, which in turn has produced an increased demand for soil remediation. Biochar has been widely documented to effectively immobilize metals in contaminated soils and has received increasing attention for use in soil remediation. Here, we review recent progresses in understanding metal-biochar interactions in soils, potential risks associated with biochar amendment, and application of biochar in soil remediation in China. These recent studies indicate that: (1) the remediation effect depends on the characteristics of both biochar and soil and their interactions; (2) biochar applications could decrease the mobility/bioavailability of HMs in soils and HM accumulation in plants; and (3) despite its advantages, biochar applications could pose ecological and health risks, e.g., by releasing toxic substances into soils or by inhalation of biochar dust. Research gaps still exist in the development of practical methods for preparing and applying different biochars that target specific HMs. In the future, the long term effects and security of biochar applications on soil remediation, soil organisms and plant growth need to be considered.