This study aims to explore the effects of biochar ageing on its surface properties and the bioavailability of heavy metals in soil. The biochar was subjected to chemical oxidation/dry–wet cycles (CDWs), chemical oxidation/freeze–thaw cycles (CFTs), and natural ageing (NT) to analyze changes in the elemental composition, pH, specific surface area, pore volume, and surface functional groups. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were applied to characterize the functional groups and microstructure, and the BCR sequential extraction method was employed to demonstrate the fractionation distribution of Cu, Cd, and Pb. The results showed that the CDWs and CFTs treatments significantly reduced the carbon content of the biochar (with a maximum reduction to 47.70%), increased the oxygen content (up to 49.17%), and notably increased the specific surface area and pore volume. The pH decreased significantly from 9.91 to 4.92 and 4.99 for the CDWs and the CFTs, respectively. The FTIR analysis indicated notable changes in hydroxyl and carboxyl functional groups, and the SEM revealed severe microstructural damage in biochar after the CDWs and CFTs treatments. The heavy metal fractionation analysis indicated that exchangeable Cu, Cd, and Pb significantly increased after the CDWs treatment, reaching 31.40%, 5.25%, and 6.79%, respectively. In conclusion, biochar ageing significantly affects its physicochemical properties and increases the bioavailability of heavy metals, raising concerns about its long-term remediation effectiveness.

In this study, eleven organochlorine pesticides (OCPs) in fresh vegetables in the Changchun suburb were investigated, and their potential health risks were evaluated. The average concentrations of OCPs in edible parts of vegetables were found in the following descending order: Σhexachlorocyclohexanes (ΣHCHs) (6.60 µg·kg⁻¹) > Σdichlorodiphenyltrichloroethanes (ΣDDTs) (5.82 µg·kg⁻¹) > ΣChlordanes (2.37 µg·kg⁻¹) > heptachlor (0.29 µg·kg⁻¹). Moreover, OCPs in different types of vegetables exceeded the maximum residue limits (MRLs), and the exceeding rates in various vegetables decreased in the following order: leafy vegetables (19.12%) > root vegetables (18.75%) > fruit vegetables (3.85%). The proportions of OCPs exceeding MRL in different vegetables were found in the following descending order: Welsh onion (22.50%) > radish (18.75%) > Chinese cabbage (14.29%) > pepper (6.90%) > cucumber (3.23%) > eggplant (2.94%) > tomato (2.78%). The sources’ identification results showed that DDTs in vegetables came mainly from newly imported technical DDTs and dicofol, while HCHs originated mainly from lindane. For both adults and children, the average target hazard quotients (avg. THQ) were all less than 1, and the average hazard index (avg. HI) values were 0.043 and 0.036, respectively. There were no significant health risks associated with OCP exposure for the inhabitants of the study area.

Soil heavy metal contamination in agricultural land has emerged as a critical environmental issue, threatening both food security and ecological sustainability. However, the contamination characteristics and associated potential ecological risks under different land use types remain poorly understood. This study presents a systematic comparison of heavy-metal pollution between three distinct agricultural land use systems (suburban vegetable fields, paddy fields, and maize fields) using an integrated approach that combines spatial analysis, pollution indices, and receptor modeling. Dehui City, a major grain-producing region in Northeast China, was selected as the study region, in which 73 topsoil samples were systematically collected. The concentrations and spatial distributions of heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn, and As) were analyzed. Source apportionment of soil heavy metals was performed using principal component analysis (PCA) and positive matrix factorization (PMF), while pollution assessment employed the geo-accumulation index (I_geo), Nemerow integrated pollution index (NIPI), and potential ecological risk index (PERI). The results showed that the mean concentrations of all heavy metals exceeded the soil background values for Jilin Province. The enrichment factors for Hg, Pb, and Cu were 3.51, 1.32, and 1.31, respectively, while all metals remained below the risk screening values (GB 15618-2018, China) for agricultural soils. Land use-specific patterns in heavy-metal accumulation were evident. Suburban vegetable fields showed elevated levels of Ni, As, and Cr, paddy fields showed elevated levels of Cd, Hg, and As, and maize fields showed elevated levels of Hg and Pb. Source apportionment revealed that agricultural fertilization, traffic emissions, industrial and coal-combustion activities, and natural sources were the main contributors. Notably, industrial and coal-combustion sources accounted for 77.7% of Hg in maize fields, while agricultural fertilization contributed 67.7% of Cd in suburban vegetable fields. The I_geo results indicated that 65.75% of the sampling sites exhibited slight or higher pollution levels for Hg. However, the NIPI results showed that 97.26% of the sampling sites remained at a safe level (NIPI < 0.7). The PERI results revealed a moderate ecological risk across the study area, with the risk levels following the order: maize fields > paddy fields > vegetable fields. Although agricultural soils generally met the safety standards, Hg-dominated ecological risks warrant priority attention and mitigation measures.

In the collection of dust, vacuum cleaners are used to clean everything inside the car, including floor/carpet, seat, console, etc. To investigate the characteristics, possible sources and carcinogenic risks of polycyclic aromatic hydrocarbons (PAHs) contamination in car dust, fourteen car dust samples were collected from commercial car washes in Changchun, Northeast China. The 16 priority PAHs were all detected in 100%, and PAHs were predominantly tetracyclic. The mean ∑16PAHs content was 9297.79 ± 5855.89 ng g⁻¹, ranging from 2940.03 to 23,174.51 ng g⁻¹. Black carbon, total carbon and PAHs were weakly correlated. The results of positive matrix factorization indicated that coal combustion contributed 30.03% of PAHs and biomass combustion contributed 24.70%. Vehicle exhaust from traffic emissions, mainly incomplete combustion of gasoline and diesel, contributed 45.27% of PAHs. The mean incremental lifetime cancer risk (ILCR) values for children and adults were 4.94 × 10⁻³ and 4.37 × 10⁻³, respectively, both above the threshold value of 10⁻⁴. This indicates that PAHs from car dust put both adults and children at high carcinogenic risk, and that children are exposed to a higher carcinogenic risk than adults. This study provides a basis for proposing targeted measures to control PAHs’ contamination from car dust.

In recent years, heavy metal contamination in suburban vegetable soils calls for significant concerns due to the rapid urbanization and industrialization. In present study, 110 suburban vegetable soil samples from Yanbian, Northeast China, were collected. Concentration characteristics, pollution level, health risk, and source identification were evaluated by using different quantitative indices. Concentrations of Pb, Cr, Cu, Ni, Zn, Cd, and As in suburban soils were measured. Mean concentrations of Pb, Cr, Cu, Ni, Zn Cd, and As were 34.9 ± 10.5, 73.5 ± 44.4, 29.6 ± 19.4, 23.4 ± 12.0, 88.5 ± 26.7, 0.16 ± 0.16, and 9.24 ± 3.79 mg/kg, which were showed significantly higher than corresponding background values of Jilin province, respectively. The soils were moderately heavy polluted by Cu and Cd based on the results of geo-accumulated index and pollution indices. The pollution load index indicated that almost all of the study area were middle or heavy polluted, especially in Antu County and Helong City. Children in Yanbian may pose non-carcinogenic and carcinogenic risks with the major exposure pathway of ingestion. Principle component analysis results suggested that Pb, Cu, Zn, and Cd were mainly associated with agricultural activities, Ni and Cr were defined as combined source (lithogenic and anthropogenic), and As was tended to be from excessive application of pesticides and industrial activities.

To investigate heavy metals (HMs) in the dust of the urban streets and evaluate health hazards through dust pollution exposure, this research implements an analysis method called principal component analysis and a model called positive matrix factorization to investigate the associations between HMs and their plausible allocation of sources. A total number of 118 dust samples were collected from Harbin, China, which is one of the most eloquent industrial hubs and tourist destinations. The results suggest that the mean concentrations of Cd, Cr, Cu, Zn, Ni, Pb, and Mn are 1.79 ± 1.618, 67.23 ± 32.84, 57.76 ± 51.50, 328.52 ± 117.62, 27.11 ± 4.66, 83.03 ± 25.39, and 745.34 ± 153.22 mg kg⁻¹, respectively. The erratic enrichment of Cu, Zn, Pb, and Cd is succeeded by a geo-accumulation index and the factors that are used for enrichment. Both the spatial distribution and correlation analysis imply that Cu, Zn, Pb, and Cd can be controlled by anthropogenic activities. On the contrary, Cr, Mn, and Ni can be ascribed to natural sources. The hazard quotients are less than 1, and the hazard indexes for seniors and kids are 0.129 and 0.852, respectively. So, kids had more non-carcinogenic hazards than the older individuals did. Both groups have carcinogenic risks of less than 1 × 10⁻⁶. The results indicated that street dust could not be potentially accepted as a health hazard for dwellers. Cu, Zn, Pb, Cr, Ni, and Cd existed in the street dust of the research region and have been influenced by the combination of industrial and traffic sources and domestic coal combustion, and the parent material that forms soil affects the levels of Mn. A model, called the PMF, is implemented in the study of street dust pollution sources, enhancing the reliability and accuracy of pollution source determination, and presenting some potential applications.