Occurrence and risk assessment of potentially toxic elements and typical organic pollutants in contaminated rural soils

Heavy metals in urban soil: Contamination levels, spatial distribution and human health risk assessment (the case of Ufa city, Russia)

The article examines the concentration of 9 heavy metals (Hg, Pb, Zn, Cr, Co, Ni, Cu, Ba and V) and As in the soil cover of the urban area in one of the largest cities in Russia, Ufa (the Republic of Bashkortostan). It is compared with aggregated data of concentrations on urbanized areas in surface soils throughout the world. For elements exceeding the average background values in soils of the urban area (Cr, Ni, Cu and Co), the average concentrations in the city soils were 346, 101, 51 and 18 ppm, respectively. Using enrichment factor (EF), geoaccumulation index (Igeo), and concentration coefficients (CC), Cr and Ni were identified as elements entering the soil cover as a result of anthropogenic pollution. Although the level of their enrichment and contamination of soils in the most territory of the city corresponds to the moderate class, there are sites with critical threshold values. Spatial analysis of heavy metals distribution was carried out based on the results of pollution load index (PLI) and ecological risk factor (Er) calculations with the use of graphical presentation of results, which allowed specific and detailed description of sites calling for special attention. The use of cluster analysis allowed dividing the sample of chemical elements into groups with probably similar sources of entry into the environment. Monte Carlo modeling of risk calculation showed negligible non-cancer risks for both adult and child populations in most of the city. While children's exposure to Cr was of concern in the more residential part of the city, free of large industrial plants, As posed a threat with respect to cancer risks in the southern part of the city, with elevated concentrations and other HMs in vicinity of the oil refineries.

Risk assessment and source analysis of heavy metals in soil around an asbestos mine in an arid plateau region, China

Asbestos is widely used in construction, manufacturing, and other common industrial fields. Human activities such as mining, processing, and transportation can release heavy metals from asbestos into the surrounding soil environment, posing a health hazard to the mining area's environment and its surrounding residents. The purpose of the present study was to determine the extent of ecological and human health damage caused by asbestos pollution, as well as the primary contributors to the contamination, by examining a large asbestos mine and the surrounding soil in China. The level of heavy metal pollution in soil and sources were analyzed using methods such as the geo-accumulation index (Igeo), potential ecological risk index (RI), and positive matrix factorization (PMF) model. A Monte Carlo simulation-based health risk model was employed to assess the health risks of heavy metals in the study area's soil to human beings. The results showed that the concentrations of As, Pb, Cr, Cu, and Ni in the soil were 1.74, 0.13, 13.31, 0.33, and 33.37 times higher than the local soil background values, respectively. The Igeo assessment indicated significant accumulation effects for Ni, Cr, and As. The RI evaluation revealed extremely high comprehensive ecological risks (RI ≥ 444) in the vicinity of the waste residue heap and beneficiation area, with Ni exhibiting strong individual potential ecological risk (Eir ≥ 320). The soil health risk assessment demonstrated that As and Cr posed carcinogenic risks to adults, with mean carcinogenic indices (CR) of 1.56E - 05 and 4.14E - 06, respectively. As, Cr, and Cd posed carcinogenic risks to children, with mean CRs of 1.08E - 04, 1.61E - 05, and 2.68E - 06, respectively. Cr also posed certain non-carcinogenic risks to both adults and children. The PMF model identified asbestos contamination as the primary source of heavy metals in the soil surrounding the asbestos mining area, contributing to 79.0%. According to this study, it is recommended that management exercise oversight and regulation over the concentrations of Ni, Cr, Cd, and As in the soil adjacent to asbestos mines, establish a designated control zone to restrict population activities, and locate residential zones at a safe distance from the asbestos mine production zone.

Exposure assessment of plastics, phthalate plasticizers and their transformation products in diverse bio-based fertilizers

Bio-based fertilizers (BBFs) produced from organic waste have the potential to reduce societal dependence on limited and energy-intensive mineral fertilizers. BBFs, thereby, contribute to a circular economy for fertilizers. However, BBFs can contain plastic fragments and hazardous additives such as phthalate plasticizers, which could constitute a risk for agricultural soils and the environment. This study assessed the exposure associated with plastic and phthalates in BBFs from three types of organic wastes: agricultural and food industry waste (AgriFoodInduWaste), sewage sludge (SewSludge), and biowaste (i.e., garden, park, food and kitchen waste). The wastes were associated with various treatments like drying, anaerobic digestion, and vermicomposting. The number of microplastics (0.045-5 mm) increased from AgriFoodInduWaste-BBFs (15-258 particles g-1), to SewSludge-BBFs (59-1456 particles g-1) and then to Biowaste-BBFs (828-2912 particles g-1). Biowaste-BBFs mostly contained packaging plastics (e.g., polyethylene terephthalate), with the mass of plastic (>10 g kg-1) exceeding the EU threshold (3 g kg-1, plastics >2 mm). Other BBFs mostly contained small (< 1 mm) non-packaging plastics in amounts below the EU limit. The calculated numbers of microplastics entering agricultural soils via BBF application was high (107-1010 microplastics ha-1y-1), but the mass of plastic released from AgriFoodInduWaste-BBFs and SewSludge-BBFs was limited (< 1 and <7 kg ha-1y-1) compared to Biowaste-BBFs (95-156 kg ha-1y-1). The concentrations of di(2-ethylhexyl)phthalate (DEHP; < 2.5 mg kg-1) and phthalate transformation products (< 8 mg kg-1) were low (< benchmark of 50 mg kg-1 for DEHP), attributable to both the current phase-out of DEHP as well as phthalate degradation during waste treatment. The Biowaste-BBF exposed to vermicomposting indicated that worms accumulated phthalate transformation products (4 mg kg-1). These results are overall positive for the implementation of the studied AgriFoodInduWaste-BBFs and SewSludge-BBFs. However, the safe use of the studied Biowaste-BBFs requires reducing plastic use and improving sorting methods to minimize plastic contamination, in order to protect agricultural soils and reduce the environmental impact of Biowaste-BBFs.

Pollution characteristics and affecting factors of phthalate esters in agricultural soils in mainland China

Phthalate esters (PAEs), the most commonly produced and used plasticizers, are widely used in plastic products and agroecosystems, posing risks to agricultural products and human health. However, current research on PAE pollution characteristics in agricultural soils in China is not comprehensive; affecting factors and relationships with microplastics and plasticizer organophosphate esters have not been sufficiently considered. In this study, farmland soil samples were collected with field questionnaires on a national scale across mainland China. The results showed that the detection rate of PAEs was 100% and the Σ16PAEs concentrations were 23.5 - 903 μg/kg. The level of PAEs was highest in the greenhouse, and significantly higher than that in mulched farmland (p < 0.05). The PAE concentration in northwestern China was the lowest among different physical geographic zones. PAEs in farmlands posed a low cancer risk to Chinese people. PAE pollution in farmlands was significantly (p < 0.05) affected by agronomic measures (such as disposal method), environmental factors, and socioeconomic factors. Overall, PAEs were significantly and positively correlated (p < 0.05) with organophosphate esters but not with microplastics. This study aims to provide scientific data for relevant prevention and control policies, as well as actionable recommendations for pollution reduction.

Origin, spatial distribution, sediment contamination, ecological and health risk evaluation of trace metals in sediments of ship breaking area of Bangladesh

Eleven trace metals (Cd, Cr, Fe, Mn, Cu, Ni, Co, Zn, As, Pb, and Ag) in sediments of Bangladesh's ship breaking area were measured by an atomic absorption spectrometer to determine origin, contamination extent, spatial distributions, and associated ecological and human health hazards. This study found considerable quantities of Pb, Cd, Mn, Zn, and Cu when compared with standards and high levels of Pb, Cd, Zn, Cu, As, and Ag contamination according to pollution evaluation indices. Different indices indicate most of the sampling sites were highly polluted. However, spatial distribution maps indicate that trace metals were predominantly deposited in the northern and southern region. The ecological risk index revealed that Cd has the highest while Pb and As had moderate risk. Based on the health index values, Zn for both adults and children were higher than the safe limit while Mn, Pb, Cr, As, Fe, Cu, Ni, and Co for children were close to the threshold. The mean total carcinogenic risk values of Cr, As, and Ni for children and Ni for adults exceeded the permissible threshold. The cancer risk possibilities were further assessed using Monte Carlo simulation. Most trace metals have anthropogenic origins, which were attributed to ship breaking activities.

Spatial distribution, sources and health risk assessment of heavy metals in topsoil around oil and natural gas drilling sites, Andhra Pradesh, India

Soils are usually the interface between human activity and environmental components that must be conserved and protected. As a result of rising industrialization and urbanization, activities such as exploration and extraction operations lead to the release of heavy metals into the environment. This study presents distribution of six heavy metals (As, Cr, Cu, Ni, Pb and Zn) in 139 top soil samples collected in and around oil and natural gas drilling sites at a sampling density of 1 site/12 km2. The results indicated the concentration ranged from 0.1 to 16 mg/kg for As, 3-707 mg/kg for Cr, 7-2324 mg/kg for Cu, 14-234 mg/kg for Ni, 9-1664 mg/kg for Pb, and 60-962 mg/kg for Zn. The contamination of soil was estimated on the basis of Index of geo accumulation (Igeo), enrichment factor (Ef), and contamination factor (Cf). Further, spatial distribution pattern maps indicated that the pollution levels for Cu, Cr, Zn, and Ni were higher around drilling sites of the study area relative to other regions. Using exposure factors for the local population and references from the USEPA's integrated database, potential ecological risk indices (PERI) and health risk assessments were made. The hazard index (HI) values of Pb (in adults) and Cr, Pb (in children) exceeded the recommended limit of HI = 1, indicating the non-carcinogenic risks. Total carcinogenic risk (TCR) calculations revealed Cr (in adults) and As, Cr (in children) levels in soils exceeded the threshold value of 1.0E - 04, indicating significant carcinogenic risk due to high metal concentrations in the study area. These results may assist in determining the soil's present state and its effect due to extraction strategies used during drilling process and initiate few remedial techniques, particularly for proper management strategies in farming activities to decrease point and non-point source of contamination.

Enhanced Organic Contaminant Retardation by CTMAB-Modified Bentonite Backfill in Cut-Off Walls: Laboratory Test and Numerical Investigation

Adding organically modified bentonite into impervious wall materials may improve the adsorption of organic pollutants. In this study, cetyltrimethylammonium bromide organically modified bentonite (CTMAB bentonite) was mixed with sodium bentonite and kaolin to obtain two materials, which were then used as cut-off walls for typical pollutants. Soil column consolidation tests, diffusion tests, and breakdown tests were conducted to study migration of organic pollutants in soil columns. The parameter sensitivity of pollutant transport in the cut-off wall was analysed by numerical simulation. The sodium bentonite mixed with 10% CTMAB bentonite and kaolin-CTMAB bentonite showed the greatest impermeability: with a consolidation pressure of 200 kPa, the permeability coefficients were 1.03 × 10^-8 m/s and 3.49 × 10^-9 m/s, respectively. The quantity of phenol adsorbed on sodium bentonite-CTMAB bentonite increased with increasing water head height. The kaolin-CTMAB bentonite column showed the best rhodamine B adsorption performance, and the adsorption rate reached 98.9% on day 67. The numerical results showed that the permeability coefficient was positively correlated with the diffusion of pollutants in the soil column. The quantity adsorbed on the soil column was positively correlated with the retardation factor, and the extent of pollutant diffusion was negatively correlated with the retardation factor. This study provides a technical means for the optimal design of organic pollutant cut-off walls.

Role of plant growth-promoting rhizobacteria in boosting the phytoremediation of stressed soils: Opportunities, challenges, and prospects

Soil is considered as a vital natural resource equivalent to air and water which supports growth of the plants and provides habitats to microorganisms. Changes in soil properties, productivity, and, inevitably contamination/stress are the result of urbanisation, industrialization, and long-term use of synthetic fertiliser. Therefore, in the recent scenario, reclamation of contaminated/stressed soils has become a potential challenge. Several customized, such as, physical, chemical, and biological technologies have been deployed so far to restore contaminated land. Among them, microbial-assisted phytoremediation is considered as an economical and greener approach. In recent decades, soil microbes have successfully been used to improve plants' ability to tolerate biotic and abiotic stress and strengthen their phytoremediation capacity. Therefore, in this context, the current review work critically explored the microbial assisted phytoremediation mechanisms to restore different types of stressed soil. The role of plant growth-promoting rhizobacteria (PGPR) and their potential mechanisms that foster plants' growth and also enhance phytoremediation capacity are focussed. Finally, this review has emphasized on the application of advanced tools and techniques to effectively characterize potent soil microbial communities and their significance in boosting the phytoremediation process of stressed soils along with prospects for future research.

Coupled Dynamic Material Flow, Multimedia Environmental Model, and Ecological Risk Analysis for Chemical Management: A Di(2-ethylhexhyl) Phthalate Case in China

Di(2-ethylhexhyl) phthalate (DEHP) is a widely used plasticizer that has adverse effects on ecosystems and human health. However, data about its stocks, flows, emission rates, as well as ecological risks are generally unknown in China, one of the world's largest producers of chemicals including DEHP, limiting sound management of chemicals. Herein, dynamic material flow analysis, coupled with a multimedia environmental model and ecological risk analysis, was performed to fill the data gap about DEHP in China mainland from 1956 to 2020. Results indicate that the in-use stocks of DEHP increased from 6.54 × 10⁶ kg in 1956 to 8.40 × 10⁹ kg in 2020. With growth in the emission rates, DEHP concentrations in air, soil, water, and sediment kept increasing from 1956 to 2010, which declined after 2010 and regrew after 2015. Sediment was a main sink of DEHP with the highest ecological risk quotient of >10 after 1999, necessitating measures for controlling the risk, for example, technology innovation to reduce DEHP emission rates, and substitution of DEHP with low-toxic alternatives. The coupled models that connect socio-economic data with ecological risk output may provide a systematic methodology for verification of the data necessary for risk control of chemicals.

Sugarcane vinasse as organo-mineral fertilizers feedstock: Opportunities and environmental risks

Fertigation using sugarcane vinasse is expected in the sugar and alcohol industries; however, its indiscriminate practice can trigger soil salinization and contamination of water sources. This review article appraises the vinasse use as a precursor material in producing organo-mineral fertilizers. Vinasse use could be an alternative for the increased demand for organo-mineral fertilizers. In that case, the vinasse reuse would be maintained but through controlled practices and lower environmental impact. The state-of-art points to possible advantages associated with the vinasse conversion into organo-mineral fertilizers, such as ease of transport and handling, low variability in its composition, and lower risks of soil and water resources contamination. It has been summarized and critically discussed the past ten years (2011-2021, total number papers revised: 175) of research data about vinasse composition, along with the limitations to be overcome in the near future to enable the application of organo-mineral fertilizers. Possible nutrients supplementation beyond those already present in vinasse composition would depend on the crop requirement, and the impact on the soil biota and integrity should be better understood. The aspects discussed along the manuscript would be aligned with circular economy principles, converting a residue (vinasse) into a potential resource for agricultural activities, including sugar and alcohol industries. After all, although promising, obtaining organo-mineral fertilizers from vinasse must be empirically validated and its feasibility proven by comparative studies between fertigation and the use of organo-mineral fertilizers.

Source identification and toxicity apportionment of polycyclic aromatic hydrocarbons in surface soils in Beijing and Tianjin using a PMF-TEQ method

Beijing and Tianjin are two of the largest cities in northern China with high population densities and highly developed manufacturing industries. In the past decade, some authors have reported their PAH concentrations in surface soils, identified their sources and quantitatively reported their health risks. However, the contributions of different PAH sources to their toxicity have not been reported thus far. In this study, we reviewed the PAH concentrations, contributions of different sources to the toxicity, and cancer risks in soils from different land use types found within Beijing and Tianjin from data gathered by 41 studies. The total PAH concentration varied in the range of 175.7–1989.0 ng g-1 with a higher median PAH concentration detected in urban soils (789.7 ng g-1), followed by suburban soils (647.3 ng g-1) and rural soils (390.8 ng g-1). Source identification using diagnostic ratios and principal component analysis (PCA) suggested that the PAHs in all three land use types mainly originated from biomass and coal combustion, vehicular emissions, and petrogenic processes with contributions varying from 13% to 62%. Furthermore, results from a positive matrix factorization (PMF) model suggested that vehicular emissions and coal combustion in urban soils, and the vehicular emissions, coal combustion and biomass combustion in suburban and rural soils dominated the total PAH concentrations (>85%). These results were consistent with those of the PCA model. Results of the additional toxicity apportionment performed using the PMF model suggested that vehicular emissions and coal combustion contributed the most to the toxic equivalent quantity for Benzo(a)Pyrene (BaPTEQ) and, by extension, to the carcinogenic potencies. The incremental lifetime cancer risk (ILCR) values suggested a low risk level for adults exposed to PAHs in the different land use types found within Beijing and Tianjin.

Plants-Microorganisms-Based Bioremediation for Heavy Metal Cleanup: Recent Developments, Phytoremediation Techniques, Regulation Mechanisms, and Molecular Responses

Rapid industrialization, mine tailings runoff, and agricultural activities are often detrimental to soil health and can distribute hazardous metal(loid)s into the soil environment, with harmful effects on human and ecosystem health. Plants and their associated microbes can be deployed to clean up and prevent environmental pollution. This green technology has emerged as one of the most attractive and acceptable practices for using natural processes to break down organic contaminants or accumulate and stabilize metal pollutants by acting as filters or traps. This review explores the interactions between plants, their associated microbiomes, and the environment, and discusses how they shape the assembly of plant-associated microbial communities and modulate metal(loid)s remediation. Here, we also overview microbe-heavy-metal(loid)s interactions and discuss microbial bioremediation and plants with advanced phytoremediation properties approaches that have been successfully used, as well as their associated biological processes. We conclude by providing insights into the underlying remediation strategies' mechanisms, key challenges, and future directions for the remediation of metal(loid)s-polluted agricultural soils with environmentally friendly techniques.

Bioaccessibility and human exposure to metals in urban soils (Huelva, SW Spain): evaluation by in vitro gastric extraction

The main purpose of this study was to assess the human health risk of heavy metals in the urban-peri-urban soils from Huelva Township. The soils present high concentrations of potentially toxic elements well beyond the regional screening soil concentration. A site-specific health risk assessment of exposure (oral ingestion, oral inhalation and dermal contact) was conducted according to the regulatory normative. To reduce the uncertainty derived from soil characteristics, bioaccessibility and predicted bioavailability data were included in the assessment. Thereby, in order to evaluate the oral bioaccessibility, a simulation of the gastric condition (pH and T) was applied dissolving the samples in a solution of HCl and 0.4 M glycine. Soils located in industrial areas present higher bioaccessibility than those associated with urban or other uses. The adjusted-relative bioaccessibility total carcinogenic risk for As exceeded the regulatory level in all samples (except samples 7 and 184) indicating that children are more vulnerable, while no detrimental health effects are expected for Pb (except in sample 76, a "greenway" recreational area). The adjusted hazard index for non-carcinogenic effects also overpassed the threshold values in practically all possible scenarios for an adult resident working in Huelva, as well as for a child living and playing in the urban/recreational areas. The main pollutant contributions were related to As and Pb. For this reason, the reported soils exceeding the regulatory levels should be classified as polluted and, therefore, this study should be helpful to initiate necessary soil management interventions to avoid the human health risk.

Di(2-ethylhexyl) phthalate and dibutyl phthalate have a negative competitive effect on the nitrification of black soil

Di (2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) are the most widely used plasticizers for agricultural mulching films and one of the most common organic pollutants in black soil. However, little is known about the effect of these two contaminants on nitrification in black soil. This study investigated the changes of 20 mg/kg DEHP and DBP on the diversity of nitrification microbial communities, the abundance of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) related genes, and the activities of key enzymes involved in nitrification. During ammonia oxidation, DEHP and DBP had uncompetitive inhibition of urease, reducing the copy number of amoA gene, and microorganisms (Azoarcus, Streptomyces and Caulobacter) would use inorganic nitrogen as a nitrogen source for physiological growth. During nitrite oxidation, the copy number of nxrA gene also reduced, and the relative abundance of chemoautotrophic nitrifying bacteria (Nitrosomonas and Nitrobacter) decreased. Moreover, the path analysis results showed that DEHP and DBP mainly directly or indirectly affect AOB and NOB through three ways. These results help better understand the ecotoxicological effects of DEHP and DBP on AOB and NOB in black soil.

Source apportionment and health risk assessment of chemicals of concern in soil, water and sediment at a large strontium slag pile area

Strontium (Sr) is an alkaline earth metal that has adverse effects on bone tissue, but received little attention compared to other often-studied metals. This study analyzed the contents/concentrations of Sr, barium (Ba), sulfate (SO₄^2-), sulfide (S^2-), and six common metals in 209 multi-media samples, including slag, soil, groundwater, surface water, and sediment, collected at a large Sr slag pile area. Sr was the dominant chemical of concern (COC) in the soil and groundwater, with contents/concentrations being 35.50-32200 mg/kg and 0.57-152 mg/L, respectively, much higher than those reported in previous research. Contents/concentrations of all COCs in the surface water and sediment were relatively low, except Sr content in the sediment near the slag pile. The LogK_d value of Sr was calculated to be lower than those of common metals, indicating relatively high mobility of Sr in the aquatic environment. Contamination assessment using Nemerow index indicated near half of the soil and groundwater sampling locations, especially those within and near the slag pile, were heavily contaminated, and Sr was the dominant COC. The positive matrix factorization model suggested four sources for the COCs in soil, including Sr slag pile/SrCO₃ production, agricultural activities, industrial activities, and natural sources, with contribution rates of 66.88%, 5.28%, 7.5%, and 20.34%, respectively. Monte Carlo simulation-based probabilistic health risk assessment revealed that the non-carcinogenic risk of groundwater, and the carcinogenic risk of soil and groundwater, were unacceptable. Notably, Sr was the unique COC posing non-carcinogenic risk among the COCs studied. Our results provide the scientific support needed for managing Sr point source impacted area.

Comprehensive characterization of PAHs profile in Serbian soils for conventional and organic production: potential sources and risk assessment

This study presents a comprehensive characterization of occurrence and levels of 16 polycyclic aromatic hydrocarbons (PAHs) in arable soils used for conventional and organic production in northern and central part of Serbia as well as cross-border region with Hungary. Furthermore, this study includes a characterization of PAH sources and carcinogenic/non-carcinogenic human health risk for PAHs accumulated in analysed arable soils. The total concentration of 16 PAHs varied between 55 and 4584 µg kg^-1 in agricultural soil used for conventional production and between 90 and 523 µg kg^-1 in agricultural soil used for organic production. High molecular weight (HMW) PAHs were dominant compounds with similar contribution in both soil types (86% and 80% in conventional and in organic soil, respectively). Principal component analysis and diagnostic ratios of selected PAHs were used for identification of PAH sources in the analysed soils. Additionally, positive matrix factorization was applied for quantitative assessment. The results indicated that the major sources of PAHs were vehicle emissions, biomass and wood combustion, accounting for ~ 93% of PAHs. Exposure of farmers assessed through carcinogenic (TCR) and non-carcinogenic (THQ) risk did not exceed the acceptable threshold (TCR < 10^-6 and THQ < 1). Oral ingestion was the main exposure route which accounted for 57% of TCR and 80% of THQ. It was followed by dermal contact. This investigation gives a valuable data insight into the PAHs presence in arable soils and reveals the absence of environmental and health risk. It also acknowledges the importance of comprehensive monitoring of these persistent pollutants.

Metabolomic Studies for the Evaluation of Toxicity Induced by Environmental Toxicants on Model Organisms

Environmental pollution causes significant toxicity to ecosystems. Thus, acquiring a deeper understanding of the concentration of environmental pollutants in ecosystems and, clarifying their potential toxicities is of great significance. Environmental metabolomics is a powerful technique in investigating the effects of pollutants on living organisms in the environment. In this review, we cover the different aspects of the environmental metabolomics approach, which allows the acquisition of reliable data. A step-by-step procedure from sample preparation to data interpretation is also discussed. Additionally, other factors, including model organisms and various types of emerging environmental toxicants are discussed. Moreover, we cover the considerations for successful environmental metabolomics as well as the identification of toxic effects based on data interpretation in combination with phenotype assays. Finally, the effects induced by various types of environmental toxicants in model organisms based on the application of environmental metabolomics are also discussed.

Assessment of Perceptions and Cancer Risks of Workers at a Polychlorinated Biphenyl-Contaminated Hotspot in Ethiopia

BACKGROUND

Polychlorinated biphenyls (PCBs) are synthetic and persistent toxic chemicals with a high potential to bioaccumulate in human tissue. There is no existing literature on workers' perceptions and occupational cancer risk due to exposure to PCBs in Ethiopia.

OBJECTIVES

The aim of the present study was to assess workers' perceptions of occupational health and safety measures of PCB management and to evaluate the cancer risk posed by PCBs to workers handling these chemicals in Ethiopia.

METHODS

A total of 264 questionnaires were administered to workers at the study area to obtain information about PCB management. A mathematical model adopted from the United States Environmental Protection Agency (USEPA) was used to assess the potential cancer risk of people working in PCB-contaminated areas.

RESULTS

The results showed that the majority of the workers had little knowledge of safe PCB management practices. Furthermore, 82.6% had not received training on chemical management and occupational health and safety protocols. The association between respondents' responses on the impact of PCBs to the use of personal protective equipment was statistically significant (p <0.005). Accidental ingestion, dermal contact and inhalation exposure pathways were considered in assessing the cancer risk of people working in these areas. The estimated cancer risk for PCBs via dermal contact was higher than for the accidental ingestion and inhalation pathways. The health risk associated with dermal contact was 73.8-times higher than the inhalation exposure route. Workers at the oil tanker and oil barrel area and swampy site are at higher risk of cancer via dermal contact at the 95th centile (879 and 2316 workers per million due to PCB exposure, respectively). However, there is very low cancer risk at the staff residence and garden area via the inhalation route.

CONCLUSIONS

Training programs would help improve the knowledge of workers in the area of occupational health and safety of chemical handling. Further studies on PCBs in the exposed workers will provide information on their blood sera PCB levels and consequently identify potential health impacts.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

Ethics approval was obtained from the Research Ethics Review Committee of Adama Hospital Medical College, Adama, Ethiopia.

COMPETING INTERESTS

The authors declare no competing financial interests.

Fuzzy health risk assessment and integrated management of toxic elements exposure through soil-vegetables-farmer pathway near urban industrial complexes

Urban industrial areas were being built globally, which decreased key geographical separation between agriculture and industrial areas, especially in developing countries. Now, limited studies concerned coordinated the vegetables and soil management for toxic elements (TEs) in this mixed land system. To fill this gap, an integrated environmental multi-media risk management method was explored based on laboratory analysis, health risk assessment, uncertainty control, and source apportionment. The Chinese Beihu area of Wuhan City was selected as a typical case and the measurements of Zn, Cr, Cu, Pb, As, and Cd in soil revealed that TEs pollution was slight and concentrations met the Chinese standards. Meanwhile, some vegetables exceeded corresponding standard limits. To further quantify negative health effects posed by the studied TEs both in soils and vegetables, an established fuzzy health risk assessment for farmers was employed and the results indicated that the soil exposure of As and the vegetable consumption needed the priority control. The carcinogenic risk (CR) of As in soil was [4.60E-6, 1.45E-5] and the cumulative CR (sum of CR_As, CR_Pb and CR_Cd) in leafy vegetables was [1.08E-4, 1.38E-4], which was higher than that of the other vegetables. Preventing soil oral exposure and reducing self-grown vegetable consumption (30%-50%) were proven as effective risk interventions via uncertainty control methods. Spatially, the risk grades under maximum membership principle decreased from south to north in the Beihu area, and the south area was identified as the priority control area. Source apportionment identified four source patterns (Zn-Cr-Cu, Pb, As, and Cd) for soil, and the probable bioaccumulation mechanisms for leafy vegetables by multivariate statistical analyses. Finally, the integrated management strategies were formulated from perspectives of the risk sources, exposure pathways and the scenario.

Hydrogeochemical evaluation, suitability, and health risk assessment of groundwater in the watershed of Godavari basin, Maharashtra, Central India

In this investigation, the geochemical progression of a total of 31 groundwater samples of pre-monsoon season was assessed with categorization based on entropy weight water quality index and risk assessment on public health in the semi-arid area of Godavari basin, Maharashtra, Central India. Graphically, the major groundwater types identified were Ca-HCO₃, mixed Ca-Mg-Cl, and mixed Ca-Na-HCO₃. Based on [Mg²⁺/Na⁺] with [Ca²⁺/Na⁺] and [HCO₃^-/Na⁺] with [Ca²⁺/Na⁺] plots, carbonate and silicate weathering were identified as a major geochemical process governing groundwater chemistry. The presence of reverse ion exchange process was authenticated by (Ca²⁺ + Mg²⁺) vs. (HCO₃^- + SO₄^2-) and Na⁺ + K⁺-Cl^- vs. (Ca²⁺ + Mg²⁺)-(HCO₃^- + SO₄^2-) plots. The saturation index values for calcite and dolomite showed that these minerals were in dissolution state. The dissolution of gypsum, dolomite, and anhydrite increased Ca²⁺ load in groundwater which accelerated the precipitation of calcite. The high toxic level of NO₃^- (> 45 mg/L) was identified in 64.5% of the 31 groundwater samples, whereas F^- concentration exceeded the threshold value in 12.9% of samples. Based on the entropy weight water quality index values, 70% of the samples were found to have moderate quality for drinking. In addition, health risk evaluation showed that the total hazard, due to fluoride and nitrate through oral pathways, was much higher than that through the dermal pathway. Children were found to be at high risk due to the consumption of NO₃^- and F^- contaminated water. The calculated irrigation water quality index (IWQI) diverge from 7.4-89.2, expressing excellent to good quality for irrigation. Based on the irrigation water quality index, 90.3% of samples were found excellent for irrigation and 6.4% of good quality for irrigation. Authors recommend that continuous water quality monitoring programs along with effective management practices should be developed to avoid excessive extraction of groundwater.

Chemical composition of soil-associated ash from the southern California Thomas Fire and its potential inhalation risks to farmworkers

The increasing frequency and severity of wildfires poses human health risks, especially for those within burnt regions. The potential health effects of fire ash on farmworkers in orchards via inhalation exposure after fire is rarely studied. After the 2017 Thomas Fire, in Ventura County (California, USA), fire ash and corresponding soil samples were collected from several impacted orchards and analyzed for eight trace elements (TEs) and 16 polycyclic aromatic hydrocarbons (PAHs). Results indicate that except for mercury (Hg), the concentrations of TEs and PAHs were higher in ash samples compared with the corresponding soil samples. In general, ash samples showed greater potential to expose farmworkers to health risks than the corresponding soil samples. One site had particularly high concentrations of As (778 mg kg^-1), Cr (629 mg kg^-1), and Cu (499 mg kg^-1) in the ash. This location corresponds to a house which was burned during the Thomas Fire, which might have contained chromated copper arsenate as a wood preservative. Therefore, the existence of construction materials in orchards could add hazardous materials to ash deposited on soil. Furthermore, a monitored dust generation experiment was designed to obtain the particle emission factors (PEF) of soil and ash, which is an essential parameter for the calculation of inhalation health risks. A two-fold difference in the PEFs was found between ash and the corresponding soil sample. Hence, health risks through inhalation exposure from fire ash may be underestimated if the default PEF suggested by the US Environmental Protection Agency is used.

Effect of enhancers on the phytoremediation of soils polluted by pyrene and Ni using Sudan grass (Sorghum sudanense (Piper) Stapf.)

Remediation of heavy metal and polycyclic aromatic hydrocarbon (PAH)-co-contaminated soils has drawn much more attention; phytoremediation is an often-used technique. Sudan grass (Sorghum sudanense (Piper) Stapf.) with developed root system and strong PAHs and heavy metal tolerance is a potential choice for phytoremediation. In this study, the application of tea saponin (TS) (1 g kg^-1 soil) and nitrilotriacetic acid (NTA) (1 g kg^-1 soil) was to improve the removal efficiency of Ni and pyrene. TS and NTA had no obvious effects on the growth and soluble proteins of Sudan grass. Ni concentration in root was higher than that in the shoot. The addition of TS and NTA increased the Ni concentration in the root by 25.98% in Ni-contaminated treatment. Pyrene was mainly accumulated in the shoot of Sudan grass. Pyrene concentration in shoot increased by 20.14% with TS-NTA in pyrene-contaminated treatment and increased by 31.97% in Ni-contaminated treatment. TS and NTA had significantly improved dissolved organic matter and soil microbial activity. Microbial activity increased by 16.75%, 18.07%, and 23.364% in pyrene-contaminated, Ni-contaminated, and pyrene and Ni-co-contaminated treatment, respectively. This study showed that phytoremediation of pyrene and Ni-co-contaminated soil by Sudan grass could be enhanced by the application of TS-NTA and the interaction between pyrene and Ni impacted the accumulation of Ni and pyrene in Sudan grass.

Spatio-temporal variation and source changes of potentially toxic elements in soil on a typical plain of the Yangtze River Delta, China (2002-2012)

The spatio-temporal variation and temporal changes in the sources of Cr, Pb, Cd, Hg, and As in soil on the Hangzhou-Jiaxing-Huzhou (H-J-H) Plain were analysed based on 4,359 soil samples collected in 2002 and 2012. Geostatistical and spatial analysis methods were used to explore the spatio-temporal variation in the pollution levels and 'pollution hotspots' for potentially toxic elements (PTEs), and the positive matrix factor model was used to quantitatively appoint and analyse temporal changes in PTE sources. The results indicated that the PTE content in most parts of the survey area were at a safe level in both 2002 and 2012, but a clearly upward trend was detected for Cr, Pb, and Cd. Moreover the pollution index for Cr, Pb, Cd, and the Nemerow composite pollution index increased in the west but decreased in the east of the H-J-H Plain from 2002 to 2012. The pollution index for Hg and As presented the opposite spatial pattern. It is obvious that there have been changes in the spatial pattern of pollution hotspots for PTEs on the H-J-H Plain from 2002 to 2012. Four sources of PTEs in soil were quantitatively appointed. In 2002, 2012, the dominant sources of Cr, Cd, Hg, and As were soil parent materials, industrial activities, atmospheric deposition and agricultural inputs, respectively. The dominant source of Pb in the soil changed from traffic emissions to soil parent materials, indicating the benefit of banning the use of leaded gasoline in China. This study highlights the importance of monitoring soil environmental quality and highlights the significance of spatio-temporal variation in PTEs in suburban zones or transitional areas undergoing rapid industrialization and urbanization, like the H-J-H Plain.

Fe-Activated Peroxymonosulfate Enhances the Degradation of Dibutyl Phthalate on Ground Quartz Sand

Soil contamination by organic compounds has received worldwide concern for decades. Here, we found that dibutyl phthalate (DBP) could be degraded on moist quartz sand (QS, crystal, a typical soil constituent) during stirring, and the removal rate reached 57.2 ± 3.1% after 8 h of reaction. The introduction of peroxymonosulfate (PMS) and zerovalent iron (Fe⁰) substantially improved the decomposition of DBP to 94.2 ± 1.6% in 8 h, suggesting they have great contributions. DBP decomposition was caused by multiple reactive species, such as surface silicon-based radicals (like ≡SiO^•) and other reactive species like superoxide radical (O₂^•-), hydroxyl radical (^•OH), and sulfate radical (SO₄^•-). In the QS/ultrapure water system, DBP was mainly attacked by O₂^•- or ≡SiO^•, with the formation of hydrolysis products. In the iron@QS/PMS system, due to the activation of PMS by Fe⁰, SO₄^•- and ^•OH were produced while the latter led to DBP degradation, and thus hydroxyl substitution products of DBP were ubiquitous. DBP was hardly removed on amorphous supporters like silica gel, alumina, and red soil even with the presence of PMS and Fe⁰, indicating the indispensable role of surface radicals on crystals like QS. This work presents a new remediation technology for polluted soil, especially aquifer.

Pollution characteristics and health risk assessment of phthalate esters in agricultural soil and vegetables in the Yangtze River Delta of China

As an important environmental reservoir of phthalate esters (PAEs), soil-plant system constitutes a key exposure pathway to human health. In this study, agricultural soil and vegetable samples were collected from the Yangtze River Delta (approximately 211,700 km²), one of the most developed regions in China, to determine the contamination characteristics of priority PAEs. The total concentrations of six PAEs ranged from 5.42 to 1580 ng·g^-1 dry weight in soils and from 10.9 to 16,400 ng·g^-1 dry weight in vegetables. Di-(2-ethylhexyl) phthalate (DEHP) accounted for 88.3% and 61.9% of the total PAEs in soils and vegetables, respectively. The spatial distribution of PAEs in the soils was as follows: Shanghai city (70.8-1583 ng·g^-1 dw) > Anhui province (46.8-1530 ng·g^-1 dw) > Jiangsu province (14.4-558 ng·g^-1 dw) > Zhejiang province (5.40-488 ng·g^-1 dw). Non-cancer risks exist for adults and children in 6.5% and 7.8% of the sites, respectively. Carcinogenic risks were regarded unacceptable in 5.6% and 1.3% of the sites for adults and children, respectively. The bioconcentration factor (BCF) of PAEs showed positive correlation with lipid content of vegetables. A basic reference of the lipid-content threshold to guarantee the safety of leafy vegetables was proposed based on partition-limited model. We suggested to cultivate vegetables with lipid content <0.21% in most heavily contaminated area in the region. This study provides information for effectively controlling PAEs contamination in soil-plant system in developed districts.

Heavy metals contamination in urban surface soils of Medak province, India, and its risk assessment and spatial distribution

The main purpose of the current study is to assess the contamination status, human health risk, and spatial distribution of heavy metals in the urban soils from the Medak province in India. For this purposes, a total of 40 urban surface soil samples were collected and analyzed seven heavy metals including chromium (Cr), copper (Cu), cadmium (Cd), arsenic (As), nickel (Ni), lead (Pb), and zinc (Zn). The results of the study showed that the concentration of Cr (81-751 mg/kg), Cu (2-180 mg/kg), Zn (25-108 mg/kg), Pb (5-77 mg/kg), Ni (1-50 mg/kg), As (0.4-14 mg/kg), and Cd (0.1-4.2 mg/kg), respectively, was found above their natural background values. The geo-accumulation index analysis indicated that except Zn, all other tested heavy metals had a range of moderately to heavily polluted/contaminated in the study region. Spatial distribution pattern analysis inferred that the soil heavy metal (Cu, Cr, Zn, and Ni) pollutions in western regions of Medak were relatively larger than that in central and eastern regions. The hazard index (HI) values for Cu, Cd, Zn, As, Pb, and Ni were below 1, implying that there is no non-carcinogenic risks exposure from these heavy metals in soil for children and adults in the study region. However, HI value for Cr ranged from 3.08E-01 to 2.86E+00 for children, implying that children were relatively vulnerable population than adults in the current study region. Comparatively speaking, 67.5% and 100% total carcinogenic risks for Cr values for adults and children were larger than the acceptable threshold value of 1.0E-04, indicating chromium poses the greatest carcinogenic risk in the study region.

Major factors dominating the fate of dibutyl phthalate in agricultural soils

Dibutyl phthalate (DBP) is a ubiquitous soil contaminant. We have investigated the sorption, degradation and residue of DBP in 20 types of agricultural soils and aimed to identify the major soil properties that dominate the fate of DBP. Sorption isotherms of DBP in all soils were fitted well with the Freundlich model. The sorption coefficient (K_f) varied between 3.99 and 36.1 mg^1-1/nL^1/n/kg. Path analysis indicated that 59.9% of variation in K_f could be explained by the combination of pH, organic carbon (OC) and clay content. Degradation of DBP in the 20 soils was well described by the first-order kinetic model, with half-lives (t_1/2) ranging from 0.430 to 4.99 d. The residual DBP concentration after 60 d of incubation (R₆₀) ranged from 0.756 to 2.15 mg/kg and the residual rates ranged from 3.97% to 9.63%. The K_f value was significantly positively correlated with t_1/2 and R₆₀. Moreover, soil pH, microbial biomass carbon (C_mic) and OC were identified as dominating factors that explained 84.4% of variation in t_1/2. The R₆₀ data indicated 72.2% of its variability attributable to the combination of OC and C_mic. The orders of the relative importance of dominating factors on the K_f, t_1/2 and R₆₀ were OC > pH > clay, C_mic > pH > OC and OC > C_mic, respectively. This work contributes to better understand the fate of DBP in soils and make scientific decisions about accelerating its dissipation in different soils.

Estimating the pollution characteristics and health risks of potentially toxic metal(loid)s in urban-industrial soils in the Indus basin, Pakistan

The Indus Basin Irrigation Network (IBIN) plays a vital role in the agricultural system of Pakistan, irrigating seventeen million hectares of cultivated areas. Rapid urbanization, industrialization, and agricultural activities along the Indus basin have influenced the soil quality and human health; it is, therefore, critical to know its pollution characteristics. Soil samples from Indus basin, i.e., Abbottabad (ABT), Haripur (HRP), Attock (ATC), and Islamabad (ISB) have been analyzed for the total contents of potentially toxic metal(loid)s (PTMs) in the top layer. The topsoil samples from 0 to 10 cm depth have been further investigated using different pollution indices and human health risk assessment models. The contamination degree of soil pollution was highest in ISB (33.75), followed by ABT (25.30) and ATC (23.57). The assessment of the daily intake of PTMs by children and adults through different pathways revealed ingestion as the significant exposure pathway. Cr was found to be the major element posing non-carcinogenic health risks to children at ATC whereas the non-carcinogenic risks posed by all other PTMs were within the safe limit. Furthermore, life-time carcinogenic risks for Ni followed by Cr and Cd were greatly exceeded at all locations and As at ATC and ISB for both age groups, but comparatively children were found to be at a higher risk of carcinogenicity. Hence, efficient remediation strategies are needed to reduce the increasing content and health risks of PTMs in the Indus basin.

Occurrence, source apportionment, and potential human health risks of metal(loid)s and PAHs in dusts from driving school campuses in an urban area of Henan, China

Concentrations, health risks, and sources of 9 metal(loid)s (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) and 16 PAHs in dusts collected from the 29 driving school campuses in the urban area of Kaifeng, Henan Province, China, were evaluated. The health risks due to exposure to these pollutants in dusts were assessed under three different scenarios (working for 10 years, 20 years, and 30 years in driving schools), using the health risk assessment model developed by US EPA. The results indicated that the mean concentrations for As, Cd, Cr, Cu, Hg, Pb, and Zn were higher than the local dust background except Co and Ni. The total PAH concentrations ranged from 198.21 to 3 400.89 μg kg^-1, with a mean value of 908.72 μg kg^-1. The dominant components were the two and three member-ring PAHs, accounting for 55.79% of the ∑PAHs, while PAHs with four to six member-rings accounted for 44.21% of total PAHs. The non-cancer risks of metal(loid)s in most samples were within the safe range except for two samples, with Pb as the major non-carcinogenic risk factor. The cancer risks of As, Cd, Cr, and Ni were also within the currently acceptable range except for one sample under two scenarios (working for 20a and 30a in a driving school). The cancer risks of PAHs in most samples were within the safe range except for one sample under scenario 3. The source identification results demonstrated that Pb, Zn, Cu, and Cd in the driving school dusts are mainly affected by the emission of driving-school vehicles. For PAHs, the typical driving school vehicle emissions were predominated by Phe and Ant, followed by Flu, Pyr, BkF, and Nap. The concentrations and health risks of the metal(loid)s and PAHs in the dusts were not significantly related to the driving school operation time or vehicle density, but closely related to the surrounding environments and the historical land uses of driving schools.

Effects of Phthalate Esters on Ipomoea aquatica Forsk. Seedlings and the Soil Microbial Community Structure under Different Soil Conditions

Phthalate acid esters (PAEs) are the most frequently utilized synthetic chemical compounds worldwide. They are typical emergent contaminants and are currently attracting considerable concern due to their risks to plants, animals, and public health. Determining the vital environmental factors that affect the toxicity of target pollutants in soil is important for vegetable production and the maintenance and control of soil productivity. We investigated the influence of di-n-butyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) under different soil conditions on physiological changes in water spinach (Ipomoea aquatic Forsk.) seedlings and the rhizosphere soil microbial community. Supported by our former experiments in which we determined the representative concentrations that caused the most pronounced toxic effects, three experimental concentrations were studied including control soils without PAEs and spiked soils with either 20 mg DBP or DEHP kg⁻¹ soil. The soil at all the three PAE concentrations was then adjusted to test two soil pH values, three levels of soil organic matter (SOM) content, and three levels of soil moisture content; thus, we completed 12 treatments or conditions simulating different soil environment conditions in greenhouses. After 30 days of cultivation, we analyzed the toxicity effects of two target PAEs on plant growth and physiological factors, and on soil microbial community characteristics. The toxicity of soil DBP and DEHP to the physiology of water spinach was found to be most affected by the soil pH value, then by SOM content, and least of all by soil moisture. The results of the 454 high-throughput sequencing analysis of the soil microbial community indicated that the toxicity of target PAEs to soil microorganisms was most affected by SOM content and then by soil moisture, and no clear relationship was found with soil pH. Under different soil conditions, declines in leaf biomass, chlorophyll a content, and carotenoid content—as well as increases in free amino acid (FAA) content, superoxide anion free radical activity, and hydroxyl radical activity—occurred in response to DBP or DEHP. Heavy use of chemical fertilizer, organic fertilizer, and high humidity led to the special environmental conditions of greenhouse soil, constituting the main conditions considered in this study. The results indicate that under the special highly intensive production systems of greenhouses, soil conditions may directly influence the effects of pollutant phytotoxicity and may thus endanger the yield, nutrient content, and food safety of vegetables. The combined studies of the impacts on plants and rhizosphere microorganisms give a more detailed picture of the toxic effects of the pollutants under different soil conditions.

Polycyclic aromatic hydrocarbon (PAHs) geographical distribution in China and their source, risk assessment analysis

In China, the huge amounts of energy consumption caused severe carcinogenic polycyclic aromatic hydrocarbon (PAHs) concentration in the soil and ambient air. This paper summarized that the references published in 2008-2018 and suggested that biomass, coal and vehicular emissions were categorized as major sources of PAHs in China. In 2016, the emitted PAHs in China due to the incomplete combustion of fuel was about 32720 tonnes, and the contribution of the emission sources was the sequence: biomass combustion > residential coal combustion > vehicle > coke production > refine oil > power plant > natural gas combustion. The total amount of PAHs emission in China at 2016 was significantly decreased due to the decrease of the proportion of crop resides burning (indoor and open burning). The geographical distribution of PAHs concentration demonstrated that PAHs concentration in the urban soil is 0.092-4.733 μg/g. At 2008-2012, the serious PAHs concentration in the urban soil occurred in the eastern China, which was shifted to western China after 2012. The concentration of particulate and gaseous PAHs in China is 1-151 ng/m3 and 1.08-217 ng/m3, respectively. The concentration of particle-bound PAHs in the southwest and eastern region are lower than that in north and central region of China. The incremental lifetime cancer risk (ILCR) analysis demonstrates that ILCR in the soil and ambient air in China is below the acceptable cancer risk level of 10-6 recommended by US Environmental Protection Agency (EPA), which mean that there is a low potential PAHs carcinogenic risk for the soil and ambient air in China.

Plastic film mulching increased the accumulation and human health risks of phthalate esters in wheat grains

Plastic film mulching is a common practice to increase crop yield in dryland, while the wide use of plastic film has resulted in ubiquitous phthalate esters (PAEs) releasing into the soil. PAEs in soil could be taken up and accumulated by dietary intake of food crops such as wheat, thus imposing health risks to residents. In the present study, samples from a long-term location-fixed field experiment were examined to clarify the accumulation of PAEs in soil and wheat, and to assess the human health risks from PAEs via dietary intake of wheat grain under plastic film mulching cultivation in dryland. Results showed that concentrations of PAEs in grains from mulching plots ranged from 4.1 to 12.6 mg kg^-1, which were significantly higher than those in the control group. There was a positive correlation for the PAE concentrations between wheat grains and field soils. Concentrations of PAEs in the soil were in the range of 1.8-3.5 mg kg^-1 for the mulching treatment, and 0.9-2.7 mg kg^-1 for the control group. Di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were detected in all soil and grain samples, and DEHP was found to be the dominant PAE compound in grains. Based on DEHP concentrations in wheat grains, the values of carcinogenic risk for adults were higher than the recommended value 10^-4. Results indicated that wheat grains from film mulching plots posed a considerable non-carcinogenic risk to residents, with children being the most sensitive resident group. Findings of this work call the attention to the potential pollution of grain crops growing in the plastic film mulching crop production systems.

Nickel uptake and distribution in Agropyron cristatum L. in the presence of pyrene

PAHs affect the uptake of heavy metal by plants. The uptake pathway, distribution and detoxification of nickel (Ni) in Agropyron cristatum L. (A. cristatum) were investigated in the presence of pyrene in this study. Most of Ni was adsorbed on the cell wall in the insoluble phosphate (57.31-72.18%) form and pectate and protein integrated (38.27-38.98%) form. Ni was transferred to the organelle (from 37.84% to 40.52%) in the presence of pyrene. The concentration of Ni in A. cristatum decreased by 27.42%; it was affected by the ATP production inhibitor and 29.49% by the P-type ATPase inhibitor. The results indicated that the uptake of Ni related closely to the synthesis and decomposition of ATP and was an active uptake process. Contents of phytochelatins (PCs) in A. cristatum in Ni contaminated soils increased by 19.97%, and an additional 4.13% increase occurred in the presence of pyrene when compared to single Ni contamination. The content of malic acid in A. cristatum was the highest for 262.78 mg g^-1 in shoots and 46.81 mg g^-1 in roots with Ni contamination. Besides, acetic acid in shoots and roots increased by 40.25% and 102.63% with Ni contamination, and by 61.59% and 185.71% with Ni-pyrene co-contamination. This study preliminarily explored the inhibitory mechanism of pyrene on plant uptake of Ni.

Distribution characteristics and health risk assessment of heavy metals and PAHs in the soils of green spaces in Shanghai, China

The environmental sustainability of megacities is a global problem, and megacities are experiencing increasing pressure and challenges with regard to providing a suitable living environment for people. Urban green space plays a crucial role in protecting urban ecological environments and in maintaining the physical and mental health of residents. In this study, a total of 94 soil samples from green spaces in Shanghai, including park green spaces and road green spaces in the eight central urban districts, were collected, and the contents of heavy metals and polycyclic aromatic hydrocarbons (PAHs) were analyzed to determine the distribution characteristics and influencing factors and to assess the associated health risks. The accumulation of heavy metals was greater in park green space soils than in road green space soils, although the variation coefficient of the former was lower than that of the latter. Conversely, the accumulation of PAHs was lower in park green space soils than that in road green space soils, although the variation coefficient of the former was higher than that of the latter. In particular, Cu, Zn, Pb, Cd, As, and PAHs have accumulated in Shanghai green space soils. With increasing soil depth (0-2 cm, 2-5 cm, 5-10 cm, and 10-30 cm), the PAH content increased in the park green space soils but decreased in the road green space soils. According to the "Technical guidelines for risk assessment of contaminated sites (MEP of China 2014)," the overall health risk posed by green space soils in urban areas in Shanghai can be considered safe, except at individual sampling sites. The PAH, Cu, and Zn contents of park green space soils might be related to the application of organic materials and to traffic and industry emissions. However, the soil pollutants in road green spaces are predominantly related to traffic and industrial emissions. Therefore, the monitoring and management of soil environmental quality must be strengthened.

Toxicity of phthalate esters to lettuce (Lactuca sativa) and the soil microbial community under different soil conditions

Phthalate esters (PAEs) are globally used plasticizers and typical endocrine disruptors that can readily accumulate in agricultural products and represent a substantial risk to human health via the food chain. The range of soil properties has an important influence on the expression of PAE toxicity, and the mechanisms by which soil physical and chemical properties affect the expression of toxicity of target PAEs to plants and microorganisms requires further investigation. Important soil factors affecting the eco-toxicological effects of two typical PAEs, di-n-butyl phthalate (DnBP) and bis (2-ethylhexyl) phthalate (DEHP), on lettuce (Lactuca sativa) in a spiked soil were investigated in the present study. Soil at various pH values was spiked with three PAE concentrations (1, 5 and 20 mg DnBP or DEHP kg-1 soil), organic matter contents and water holding contents to simulate the greenhouse soil environment for 30 days. Their influence on the biomass, photosynthetic pigment contents, various physiological changes and soil microbial communities was determined as endpoints. The toxicity to lettuce of DnBP was higher than that of DEHP in the soil and soil pH was the most important factor affecting their single toxicity, followed by soil organic matter content and soil moisture content in agreement with the Biolog test results. Under different soil conditions total protein, total soluble sugar and free amino acid contents were positively correlated with concentrations of the target PAEs, but leaf area, biomass, •O2- activity, vitamin C content and soil microbial diversity indices showed the opposite trend. Chlorophyll a and carotenoid contents were more inhibited by DnBP together with impacts on indices of soil microbial diversity. The results suggest that soil conditions in greenhouses directly explain the patterns of pollutant toxicity displayed and impact the quantity, quality and food safety of vegetables produced using highly intensive production systems.