Spatial clustering and source-specific risk of combined pollutants in soils from an industrial area in Shanxi Province, China

Ryegrass uptake behavior and forage risk assessment after exposing to soil with combined polycyclic aromatic hydrocarbons and cadmium

Internalization of chemicals and the forage risks of ryegrass under the combined exposure to PAHs and Cd at environmental concentrations were studied here. The effect of soil pH was also concerned due to the widely occurred soil acidification and general alkali remediation for acidification soil. Unexpectedly, as same as the acid-treated group (pH 6.77), the alkali-treatment (pH 8.83) increased Cd uptake compared with original soil pH group (pH 7.92) for the reason of CdOH+ and CdHCO3+ formed in alkali-treated group. Co-exposure to PAHs induced more oxidative stress than Cd exposure alone due to PAHs aggregated in young root regions, such as root tips, and consequently, affecting the expression of Cd-transporters, destroying the basic structure of plant cells, inhibiting the energy supply for the transporters, even triggering programmed cell death, and finally resulting in decreased Cd uptake. Even under environmental concentrations, combined exposure caused potential risks derived from both PAHs and Cd. Especially, ryegrass grown in alkali-treated soil experienced an increased forage risks despite the soil meeting the national standards for Cd at safe levels. These comprehensive results reveal the mechanism of PAHs inhibiting Cd uptake, improve the understanding of bioavailability of Cd based on different forms, provide a theoretical basis to formulate the safety criteria, and guide the application of actual soil management.

Integrated framework to assess soil potentially toxic element contamination through 3D pollution analysis in a typical mining city

Soil potentially toxic elements (PTEs) pollution of contaminated sites has become a global environmental issue. However, given that previous studies mostly focused on pollution assessment in surface soils, the current status and environmental risks of potentially toxic elements in deeper soils remain unclear. The present study aims to cognize distribution characteristics and spatial autocorrelation, pollution levels, and risk assessment in a stereoscopic environment for soil PTEs through 3D visualization techniques. Pollution levels were assessed in an integrated manner by combining the geoaccumulation index (Igeo), the integrated influence index of soil quality (IICQs), and potential ecological hazard index. Results showed that soil environment at the site was seriously threatened by PTEs, and Cu and Cd were ubiquitous and the predominant pollutants in the study area. The stratigraphic models and pollution plume simulation revealed that pollutants show a decreasing trend with the deepening of the soil layer. The ranking of contamination soil volume is as follows: Cu > Cd > Zn > As > Pb > Cr > Ni. According to the IICQs evaluation, this region was subject to multiple PTE contamination, with more than 60% of the area becoming seriously and highly polluted. In addition, the ecological hazard model revealed the existence of substantial ecological hazards in the soils of the site. The integrated potential ecological risk index (RI) indicated that 45.7%, 10.13%, and 4.15% of the stereoscopic areas were in considerable, high, and very high risks, respectively. The findings could be used as a theoretical reference for applying multiple methods to integrate evaluation through 3D visualization analysis in the assessment and remediation of PTE-contaminated soils.

Bacterial response to the combined pollution of benzo[a]pyrene and decabromodiphenyl ether in soil under flooding anaerobic condition

This study investigated the interaction between the co-pollutants of Benzo[a]pyrene (BaP) and decabromodiphenyl ether (BDE-209) and the bacterial community in soil under flooding anaerobic condition. Three levels of combined pollution (at nominal concentrations of 1, 5, and 25 mg/kg, respectively, for each pollutant), their corresponding sterilized controls, and a blank control (CK) were set up. During the incubation time of 270 days, BaP attenuated more easily than BDE-209. The second-order rate constant of BaP attenuation was negatively correlated with the Ln value of initial BaP concentration. Maximal difference in bacterial community occurred between the CK soil and the highly polluted soil. Desulfomonilaceae, Parcubacteria and Rhodanobacter were probably involved in BaP and BDE-209 degradation, while Nitrosomonadaceae, Phenylobacterium and Mitochondria were significantly suppressed by BaP and BDE-209 or their degrading products. Genes narI, bcrC, fadJ, had, dmpC, narG and CfrA were involved in the degradation of BaP and BDE-209. Impacts of BaP and BDE-209 on metabolisms of carbon, nitrogen and sulfur were not significant. The results provide guidance for the management and remediation of the contaminated soil.

Field application of hydroxyapatite and humic acid for remediation of metal-contaminated alkaline soil

The quality of soil is essential for ensuring the safety and quality of agricultural products. However, soils contaminated with toxic metals pose a significant threat to agricultural production and human health. Therefore, remediation of contaminated soils is an urgent task, and humic acid (HA) with hydroxyapatite (HAP) materials was applied for this study in contaminated alkaline soils to remediate Cd, Pb, Cu, and Zn. Physiochemical properties, improved BCR sequential extraction, microbial community composition in soils with superoxide dismutase (SOD), peroxidase (POD), and chlorophyll content in plants were determined. Among the studied treatments, application of HAP-HA (2:1) (T7) had the most significant impact on reducing the active forms of toxic metals from soil such as Cd, Pb, Cu, and Zn decreased by 18.59%, 9.12%, 11.83%, and 3.33%, respectively, but HAP and HA had a minor impact on metal accumulation in Juncao. HAP (T2) had a beneficial impact on reducing the TCleaf/root of Cd, Cu, and Zn, whereas HAP-HA (T5) showed the best performance for reducing Cd and Cu in EFleaf/soil. HAP-HA (T5 and T7) showed higher biomass (57.3%) and chlorophyll (17.9%), whereas HAP (T4) showed better performance in POD (25.8%) than T0 in Juncao. The bacterial diversity in soil was increased after applying amendments of various treatments and enhancing metal remediation. The combined application of HAP and HA effectively reduced active toxic metals in alkaline soil. HAP-HA mixtures notably improved soil health, plant growth, and microbial diversity, advocating for their use in remediating contaminated soils.

Pollution and source-specific risk analysis of potentially toxic metals in urban soils of an oasis-tourist city in northwest China

Source-specific risk apportionment for soil potentially toxic metals (PTMs) is of great significance for contamination prevention and risk management in urban environments. Eighty-five urban soil samples were obtained from an oasis-tourist city, China and examined for eight PTMs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn). The pollution levels, sources, and ecological risk of soil PTMs were quantified, and their source-specific ecological and human health effects were also estimated using the multi-proxy approaches. The results demonstrated that accumulation of Cd, Hg, Pb, Cr, Cu, and Zn in soils was observed compared to their background levels, and the soils experienced varying degrees of PTMs pollution, especially at sites with high-intensity anthropogenic activities. Natural sources, atmospheric deposition, industrial sources, vehicular emissions, and comprehensive inputs were the principal sources, with contributions of 29.28%, 25.86%, 20.13%, 16.50%, and 8.23%, respectively. The integrated ecological risks of PTMs in soils were moderate at most sites, with atmospheric deposition being the dominant contributor to ecological risks. Children exhibited pronounced non-cancer risks, but adults had no notable non-cancer risks. Moreover, there were potential carcinogenic risks for both children and adults within the study region. Non-cancer and carcinogenic risks were more significant for children than adults, and traffic emissions were the primary contributor to non-cancer risks (adults: 20.53%, children: 20.49%) and carcinogenic risks (adults: 22.95%, children: 22.08%). The industrial and traffic activities were considered as priority control sources for soil pollution control and risk management, with Hg, Cd, Zn, and Pb corresponding to the priority elements. This study highlights the source-specific ecological and human health effects of PTMs pollution in urban soils, thereby providing valuable information for targeted pollution control and priority source management.

Contamination and source-specific health risk assessment of polycyclic aromatic hydrocarbons in soil from a mega iron and steel site in China

The iron and steel industry has always been a key and difficult point of environmental pollution control. In the present study, 493, 175, 153, 72, and 42 soil samples were collected from the soil depths of 0-0.5, 0.5-2, 2-3, 3-4, and 4-5 m (herein called the layers) of the Shougang Steel site, respectively. Compared with the evaluation criteria, the Shougang Steel surface soil was severely polluted by polycyclic aromatic hydrocarbons (PAHs). Inverse distance-weighted interpolation and the Kruskal-Wallis H test revealed that the soil PAH pollution in the iron-making area, especially the coking area, was severer than those in other areas. The PAH concentrations first decreased, and then, increased with the increase of depth. With the increase in depth, the contributions of 2- and 3-ring PAHs increased, while those of 4-, 5-, and 6-ring PAHs decreased. The bivariate local indicators of spatial association (LISA) analysis was used to identify the areas prone to soil PAH pollution due to atmospheric deposition of industrial waste gas and traffic emissions. The method could be used to analyze the impact of anthropogenic activities on soil's PAH pollution for other contaminated sites. Three main pollution sources of soil PAHs, the backfill source, the combustion of coal, and the traffic emissions, were identified based upon three diagnostic ratios, positive matrix factorization and the bivariate LISA analysis, and accounted for 53.8%, 23.5%, and 22.7%, respectively. The combination of bivariate LISA analysis and other source analysis methods could improve the accuracy of source analysis. Benzo[a]pyrene contributed the most to the total health risk among sixteen PAHs. The health risks related to the three pollution sources decreased in the order of backfill sources > coal combustion > traffic emissions. The incremental life-time carcinogenic risks were all below 10-4, indicating negligible or acceptable risks.

Heavy metal toxicity in poultry: a comprehensive review

Arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) have been recognized as most toxic heavy metals that are continuously released into the environment, both from natural sources and from anthropogenic production of fertilizers, industrial activities, and waste disposal. Therefore, As, Cd, Hg, and Pb are found in increasing concentrations in bodies of water, fodder, feed, and in the tissues of livestock, including poultry, in the surroundings of industrial areas, leading to metabolic, structural, and functional abnormalities in various organs in all animals. In poultry, bioaccumulation of As, Pb, Cd, and Hg occurs in many organs (mainly in the kidneys, liver, reproductive organs, and lungs) as a result of continuous exposure to heavy metals. Consumption of Cd lowers the efficiency of feed conversion, egg production, and growth in poultry. Chronic exposure to As, Pb, Cd, and Hg at low doses can change the microscopic structure of tissues (mainly in the brain, liver, kidneys, and reproductive organs) as a result of the increased content of these heavy metals in these tissues. Histopathological changes occurring in the kidneys, liver, and reproductive organs are reflected in their negative impact on enzyme activity and serum biochemical parameters. Metal toxicity is determined by route of exposure, length of exposure, and absorbed dosage, whether chronic and acute. This review presents a discussion of bioaccumulation of As, Cd, Pb, and Hg in poultry and the associated histopathological changes and toxic concentrations in different tissues.

Organophosphate esters in soils of Beijing urban parks: Occurrence, potential sources, and probabilistic health risks

Organophosphate esters (OPEs) are an emerging contaminant widely distributed in the soil. OPEs have drawn increasing attention for their biological toxicity and possible threat to human health. This research investigated the pollution characteristics of two typical OPEs, organophosphate triesters (tri-OPEs) and organophosphate diesters (di-OPEs), in soils of 104 urban parks in Beijing. The median concentrations of Σ₁₁tri-OPEs and Σ₈di-OPEs were 157 and 17.9 ng/g dw, respectively. Tris(2-chloroisopropyl) phosphate and bis(2-ethylhexyl) phosphate were the dominant tri-OPE and di-OPE, respectively. Consumer materials (such as building insulation and decorative materials), traffic emissions, and reclaimed water irrigation may be critical sources of tri-OPEs in urban park soils. Di-OPEs mainly originated from the degradation of parent compounds and industrial applications. Machine learning models were employed to determine the influencing factors of OPEs and predict changes in their concentrations. The predicted OPEs concentrations in Beijing urban park soils in 2025 and 2030 are three times and five times those in 2018, respectively. According to probabilistic health risk assessment, non-carcinogenic and carcinogenic risks of OPEs can be negligible for children and adults. Our results could inform measures for preventing and controlling OPEs pollution in urban park soils.

Three-dimensional distribution characteristics of multiple pollutants in the soil at a steelworks mega-site based on multi-source information

Soil pollution at steelworks mega-sites has become a severe environmental issue worldwide. However, due to the complex production processes and hydrogeology, the soil pollution distribution at steelworks is still unclear. This study scientifically cognized the distribution characteristics of polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and heavy metals (HMs) at a steelworks mega-site based on multi-source information. Specifically, firstly, 3D distribution and spatial autocorrelation of pollutants were obtained by interpolation model and local indicators of spatial associations (LISA), respectively. Secondly, the characteristics of horizontal distribution, vertical distribution, and spatial autocorrelations of pollutants were identified by combining multi-source information such as production processes, soil layers, and properties of pollutants. Horizontal distribution showed that soil pollution in steelworks mainly occurred in the front end of the steel process chain. Over 47% of PAHs and VOCs pollution area were distributed in coking plants and over 69% of HMs in stockyards. Vertical distribution indicated that HMs, PAHs, and VOCs were enriched in the fill, silt, and clay layers, respectively. Spatial autocorrelation of pollutants was positively correlated with their mobility. This study clarified the soil pollution characteristics at steelworks mega-sites, which can support the investigation and remediation of steelworks mega-sites.

Variation in pollution status, sources, and risks of soil heavy metals in regions with different levels of urbanization

Soil heavy metal (HM) pollution is an increasing threat to ecosystem integrity and human health with rapid urbanization. Nevertheless, how soil HMs vary with the process of urbanization remains unclear. Here we used index evaluation, spatial analysis, and a positive matrix factorization (PMF) model to determine the pollution characteristics and sources of eight soil HMs (Mn, Cr, Cu, Zn, As, Cd, Pb, and Ni) among regions with different urbanization levels (urban area, suburb, and ecoregion) in Baoding City, Northern China. We also assessed the risks posed to the ecosystem and human health using risk assessment models. The results indicated that the mean levels of Cu, Zn, As, Cd, and Pb in the study area exceeded the soil environmental quality standards by 10.7 %, 10.7 %, 12.5 %, 23.2 %, and 3.57 %, respectively. A pronounced regional spatial distribution was discovered with high levels in suburban areas. Both the geo-accumulation index and potential ecological risk index revealed significantly higher HM contamination in suburban areas than in urban or ecoregion areas. Source apportionment based on the PMF model and correlation analysis showed that soil HMs in suburban areas primarily originated from agricultural activity, industrial sources, and natural sources. Those in urban soils originated from industrial sources, urban traffic, and natural sources, whereas those in ecoregions derived from natural sources and agricultural activity. The complex sources of soil HMs in suburban areas resulted in the highest carcinogenic risks to children health, followed by the ecoregion, but not in urban areas. This study identified the differences in pollution levels, sources, and risks of soil HMs among regions with different urbanization levels and can guide future efforts to mitigate and manage soil HM pollution during urbanization.

Vector maps and spatial autocorrelation of carbon emissions at land patch level based on multi-source data

An accurate carbon emissions map is of great significance for urban planning to reduce carbon emissions, mitigate the heat island effect, and avoid the impact of high temperatures on human health. However, little research has focused on carbon emissions maps at the land patch level, which makes poor integration with small and medium-sized urban planning based on land patches. In this study, a vectorization method for spatial allocation of carbon emissions at the land patch level was proposed. The vector maps and spatial autocorrelation of carbon emissions in Zhangdian City, China were explored using multi-source data. In addition, the differences between different streets were analyzed, and the carbon emissions ratio of the land patch was compared. The results show that the vector carbon emissions map can help identify the key carbon reduction land patches and the impact factors of carbon emissions. The vector maps of Zhangdian City show that in 2021, the total carbon emissions and carbon absorptions were 4.76 × 10⁹kg and 4.28 × 10⁶kg respectively. Among them, industrial land accounted for 70.16% of carbon emissions, mainly concentrated in three industrial towns. Forest land carbon absorption accounted for 98.56%, mainly concentrated in the peripheral streets away from urban areas. The Moran's I of land patch level carbon emissions was 0.138, showing a significant positive spatial correlation. The proportion of land patches is an important factor in determining carbon emissions, and the adjustment of industrial structure is the most critical factor in reducing carbon emissions. The results achieved can better help governments develop different carbon reduction strategies, mitigate the heat island effect, and support low-carbon and health-oriented urban planning.

Construction of bifunctional bacterial community for co-contamination remediation: Pyrene biodegradation and cadmium biomineralization

Polycyclic aromatic hydrocarbons and heavy metals are typical pollutants in the non-ferrous metal smelting industry. The combination of biodegradation and biomineralization has great development potential for co-contamination removal as an environmentally friendly method. Pyrene (Pyr) and cadmium (Cd) were regarded as model pollutants of co-contamination in this study. A bifunctional bacterial community named Ycp was screened from a non-ferrous smelting slag field soil. The 16S rRNA gene high throughput sequencing analysis showed that Enterobacter was the dominant genus (99.1%). Ycp had adaptability under a wide range of environmental conditions (pH 3-9, salinity 0-10 g L^-1 NaCl, Pyr concentration 0-50 mg L^-1, Cd concentration 0-100 mg L^-1), and the removal rate of Pyr and Cd reached 41.8%-76.9%, 82.8%-98.8%, respectively. It was found that compound carbon sources had promoting effect on the removal of Pyr and Cd, with the maximum removal rate of 88.3% and 98.0%. According to the degradation products of Pyr by LC-MS analysis and the mineralized products of Cd²⁺ by XRD and SEM-EDS analysis, the mechanism of Ycp for co-contamination remediation was: Ycp biodegraded Pyr through salicylic acid and phthalic acid metabolic pathways, and biomineralized Cd²⁺ into CdCO₃ through microbially induced carbonate precipitation. This study provided a basis for microbial remediation of co-contamination.

Spatial Distribution, Potential Sources, and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Soils under Different Land-Use Covers of Shanxi Province, North China

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment and pose a serious threat to the soil ecosystem. In order to better understand the health risks for residents exposed to PAH-contaminated soil, 173 surface soil samples were collected in Shanxi Province, China, to detect the levels of 16 priority PAHs. The spatial distribution patterns of PAHs were explored using interpolation and spatial clustering analysis, and the probable sources of soil PAHs were identified for different land-use covers. The results indicate that the soil Σ16 PAH concentration ranged from 22.12 to 1337.82 ng g^-1, with a mean of 224.21 ng g^-1. The soils were weakly to moderately contaminated by high molecular weight PAHs (3-5 ring) and the Taiyuan-Linfen Basin was the most polluted areas. In addition, the concentration of soil PAHs on construction land was higher than that on other land-use covers. Key sources of soil PAHs were related to industrial activities dominated by coal burning, coking, and heavy traffic. Based on the exposure risk assessment of PAHs, more than 10% of the area was revealed to be likely to suffer from high carcinogenic risks for children. The study maps the high-risk distribution of soil PAHs in Shanxi Province and provides PAH pollution reduction strategies for policy makers to prevent adverse health risks to residents.