Pollution Risk Assessment Research Articles

Regional metal pollution risk assessment based on a long short-term memory model: A case study of the South Altai Mountain mining area, China

The discharge of wastewater and waste rock in mining production activities is a significant hidden cause of soil heavy metal pollution. The accumulation of heavy metals in soil occurs through a variety of processes, and exposure to these metals can permanently damage the human body. Due to multiple factors, such as the formation causes, sources, and distribution trends of heavy metals in mineral resources, reasonably applying different machine learning methods to monitor and evaluate heavy metal pollution remains challenging. In this paper, we choose the copper mining area in the southern Altai Mountains of China as the study area, and 19 different types of spatial data are uniformly managed in a distributed database to improve monitoring efficiency. Furthermore, we propose a heavy metal pollution evaluation framework based on a stacked long short-term memory (LSTM) model, which considers spatial data correlations and extracts spatial clustering features. Information is screened through state updating in the framework, the short-term memory features of long sequences are extracted, and an effective prediction model is established. The results show that 26 of the 31 mining occurrences in the study area are in moderate- and high-pollution-risk grids, suggesting that the spatial distribution of copper mines is consistent with the predicted spatial distribution of pollution risk. Overall, these results show that using the optimized stacked LSTM model to integrate multisource geological features and mine the internal rules of feature information has a positive effect on improving the risk assessment of heavy metal pollution.

A Review on Detection Techniques, Health Hazards and Human Health Risk Assessment of Arsenic Pollution in Soil and Groundwater

One of the most significant elements in the environment is arsenic (As). It is a hazardous metalloid that causes contamination of soil and water supplies as a result of numerous anthropogenic and natural sources. This pollution has detrimental impacts on human health and the ecosystem, making it crucial to monitor and control. The release of As from minerals into the soil and groundwater depends on the kind of mineral, pH, and redox conditions. As is typically found in two forms, trivalent arsenic (As3+, arsenite) and pentavalent arsenic (As5+, arsenate), both of which are inorganic and extremely deadly. When it comes to toxicity, arsenite is more dangerous than arsenate. Many people have been affected by As poisoning, due to exposure to As through water and food. Nowadays, accurate, fast measurement of As in the field remains a technical challenge; however, the X-ray fluorescence method is considered the most reliable, cost effective and capable of measuring a wide spectrum of metals. Health risk assessment is a crucial parameter to estimate the health hazards of the As molecule. The risk assessment approach proposed by the USEPA is common and widely used, amongst others. On the numerous health risk assessment models/frameworks used to foresee the carcinogenic and non-carcinogenic health impacts brought on by As-contaminated water, little information is currently accessible. This discussion also emphasizes the need for more study on the risks to human health posed by specific As species (both organic and inorganic) found in As-contaminated water.

Risk assessment of microplastic pollution in urban lakes and peripheral Rivers of Dhaka, Bangladesh

Although microplastics (MPs) are considered as a ubiquitous pollutants, most of the studies on MPs in water have paid little attention to the analysis of the ecological risk of MPs, which is decisive in understanding the effect of MPs on the aquatic ecosystem. Therefore, to evaluate possible ecological risks, this study investigated the abundance of MPs in surface water and underlying sediments of several lakes and peripheral rivers of Dhaka city, Bangladesh. 19 sites (in five lakes and five rivers) were sampled to ensure maximum city coverage. Density separation, microscopic inspection and FTIR analysis were conducted to analyze the characteristics of MPs and the type of polymers. The average MPs abundance in water and sediment samples was 36000 MPs/m3 and 13607 MPs/kg dry weights. Most of the MPs are fiber and fragments in shape in sediment samples. However, foam is also a significant fraction of water samples. The high MPs numbers have occurredespecially for the particles having diameter <0.5 mm. Using FTIR, eight polymer types were identified in the MPs samples, including polypropylene, polystyrene, nylon, low-density polyethylene, ethylene-vinyl acetate, acrylonitrile butadiene styrene, and polyethylene terephthalate. For assessing the ecological risk of MPs, the predicted no-effect concentration (PNEC) values were calculated through a species' sensitivity distribution (SSD) model. The PNEC for MPs in the surface water of those lakes and rivers are 43870 n/m3. Ecological risk assessment for MPs suggests that most of the water bodies posed low risks (Risk quotient (RQ)<1) to freshwater biota, except the five sites with high risk. The estimated RQ values based on SSD analysis in this pilot study may serve as a baseline to understand the possible ecological risks of MPs in fresh water.

Editorial: Toxic effects and ecological risk assessment of typical pollutants in aquatic environments

Editorial: Toxic effects and ecological risk assessment of typical pollutants in aquatic environments

Omics-based high throughput toxicity screening and risk assessment of pollutants

<p indent="0mm">Screening priority pollutants with high toxicity and risk potential from a large number of environmental chemical pollutants is the prerequisite for prevention and control of environmental risks. After entering the living system, toxic pollutants can induce adverse outcomes through a series of disturbed molecular targets and biological pathways. Existing high-throughput toxicity screening methods rely on few and isolated cellular or molecular endpoints, making it difficult to capture the key biological processes that cause toxicity and to determine the direct relationship between chemical pollutants and disease. Meanwhile, the awareness is increasing that we are exposed to a true cocktail of chemicals, among which only a fraction has been identified through analytical methods. Integrated bioanalytical approaches, such as effect-directed analysis and toxicity identification evaluation (TIE), have been used to identify risk drivers in complex mixture pollutants. However, it is still difficult to elucidate the molecular toxicological drivers of chemical stress in the environment. Toxicogenomics take advantage of genome-wide coverage, high throughput, and big data capacity that are associated with omics technologies to achieve technology innovation in screening and risk assessment of chemical pollutants. We reviewed the technical advantages and the recent progress of toxicogenomic methodology in high-throughput toxicological screening and risk assessment of chemical pollutants from four aspects with specific research cases. To identify the molecular events initiated by toxic pollutants, toxicogenomics could uncover a large number of molecular events and pathways potentially disturbed at the early development stage of toxicity. Dose-dependent transcriptomes for high-throughput chemical testing have been developed to quantitatively assess responses induced by chemical pollutants at the molecular level, which improve the sensitivity of identifying bioactivity by 1–3 orders of magnitude. To uncover the biological pathways of adverse health outcome by chemical pollutants, systemic toxicological assessment by omics strategies provide mechanistic information for chemical pollution screening and health risk assessment at multiple biological levels. Through biological pathway enrichment analysis, such as the gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) pathway, the molecular mechanistic information of toxicity could be captured. Moreover, multi-omics integration allows for multi-scale, comprehensive biological network analysis, which provide a systematic understanding of toxicity pathways or adverse outcome pathways (AOPs) to guide ecological and human health risk assessments. For human diseases diagnostics, functional genomics provide a new tool to explore mechanisms of individual disease risk and susceptibility under toxic pollutants exposure. Variations of individual susceptibility to toxicant-induced disease are largely due to genetic susceptibility across different populations. The direct relationship among pollutants, genes and adverse outcomes could be established by combining functional genomics and molecular epidemiological approaches. Finally, for risk management of complex mixture pollutants, it is important to assess the overall toxicity effects of the pool of pollutants and identify the key toxic pollutant. The combination of high-throughput bioassays and chemical analysis can be used to identify the highly bioactive fraction and to screen the key chemical pollutant that pose ecological and health risks. Recently, progresses have been made in integrating transcriptomic techniques with molecular toxicity identification and evaluation (mTIE) to assess the overall effects of mixtures and distinguish the key pollutants in inducing the corresponding biological responses. Particularly, dose-response transcriptome could be used to quantitatively evaluate the overall toxic effects and to guide the key toxicant identification by high mechanistic resolution. In summary, the development of omics-based high-throughput toxicity screening technologies will strongly support accurate environmental risk assessment of conventional and new pollutants in the future.

Potential environmental pollution and human health risk assessment due to leachate contamination of groundwater from anthropogenic impacted site

One of the consequences of landfill systems is the emission of leachate, which is capable of causing contamination of the surrounding environment, including groundwater. Considering three major abandoned landfills in an urban area in Nigeria, the potential environmental pollution due to leachate generated from landfills and human health risk assessment of nearby groundwater were examined using laboratory standards (APHA 2012). The result revealed that the landfills' leachate pollution index (LPI) is 18.84, 19.57, and 19.66, indicating potential pollution of the environment, including groundwater and soil. Conformity of groundwater indicated that Arsenic (Ar-0.0001), Cadmium (Cd-0.002), Zinc (Zn-0.02), Barium (Ba-0.03), Manganese (Mn-0.05), Copper (Cu-0.02, 0.012), Chromium (Cr-0.006, 0.007), and Cobalt (Co-0.03, 0.015) are within the WHO permissible limit while Nickel (Ni-0.06) and Lead (Pb-0.05) exceeded the permissible limit. Using the USEPA model for human health risk assessment, the Total Hazard quotient (THQ) for ingestion and derma exposure indicated that the heavy metals have ≤1 across the three landfills, indicating that the exposed population experience no significant health risk. The THQ trended as Cd>Co>Zn>Ba>Mn>Cu>Cr>Ni>As>Pb for children across all the landfills. The estimation for Total Carcinogenic Risk (TCR) for carcinogenic metals (As, Cd, Cr, Ni, and Pb) from various landfill indicated no carcinogenic risk (TCR <10−6). Although the abandoned landfills showed potential environmental pollution and contamination of groundwater; however, the health risk assessment of the groundwater revealed no significant carcinogenic risk to the population exposed to it. Hence, the need for water treatment and evaluation of the soil contamination status of landfills.

Spatial Differentiation and Influencing Factor Analysis of Soil Heavy Metal Content at Town Level Based on Geographic Detector

Geographic detectors can quickly detect spatial stratified heterogeneity and quantitatively reveal the intensity of driving factors of heavy metal content, which is of great significance for the prevention, control, and remediation of soil heavy metal pollution. In order to reveal the spatial differentiation and influencing factors of soil heavy metal content on the town-scale, 788 topsoil samples were collected from a town in the hinterland of Chengdu Plain. Soil heavy metal (Cd, Hg, As, Cu, Pb, Cr, Zn, and Ni) pollution risk assessments were carried out by using the geo-accumulation index method. Additionally, based on the geographic detector model, 15 factors such as soil properties, topography, soil forming factors, and distance were taken as independent variables, and the contents of each heavy metal element were taken as dependent variables to explore the spatial differentiation and influencing factors of heavy metal content in soils. The results showed that:the average contents of Hg, As, Pb, Cr, Cu, Ni, and Zn in the study area were 1.06-1.93 times the background value of Chengdu, and the content of Cd was lower than the background value; among them, Hg reached the light pollution level, and the other seven heavy metals were at the non-pollution level. The spatial distribution of eight heavy metals was significantly different, the correlation among the elements was significant, and a significant correlation was found between most heavy meals with soil properties; however, the correlation with distance factor and topographic factor was relatively weak. The factor detection showed that TP, TK, pH, TOC, elevation, and distance from the railway had the most significant explanatory power for the heavy metal contents. Interaction detection showed that the interaction between soil properties and other factors was the dominant factor for the spatial variation in heavy metals, and elevation, distance from residential area, distance from railways, and distance from industrial areas were also important factors. Risk detection showed that Hg had the most significant difference in the subregion of elevation and distance from railway, whereas the other seven heavy metals had the most significant difference in the sub-regions of influencing factors of soil properties. The spatial distribution of heavy metals varied significantly in soil at the town-scale, which was closely related to soil properties, topography, and human activities in the study area.

Microplastic reorganization in urban river before and after rainfall

Microplastics (MPs) present in non-negligible amounts in urban environments, where urban rivers serve as important transport channels for MPs. However, the footprint of MPs in urban rivers under the influence of natural and anthropogenic factors is poorly understood. This study investigated the MPs organization, stability and pollution risk before and after rainfall in the Qing River, Beijing. Rainfall potentially diluted the MPs abundance, attributed to opening of barrages and increase of flow velocity. The proportion of small-sized MPs (SMPs, 48–300 μm) decreased slightly, whereas that of normal-sized MPs (NMPs, 300–1000 μm) and large-sized MPs (LMPs, > 1000 μm) increased. However, SMPs dominantly presented in the Qing River before and after rainfall. Polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), and polystyrene (PS) were main polymers observed in the Qing River. The proportions of PET and PS decreased, while PP and PE increased after rainfall. The main types of MPs introduced by stormwater were PP and PE. The elevated MP diversity integrated index after rain suggested that rainfall enriched the local sources of MPs. Rainfall reduced the stability and fragmentation of MPs owing to the introduction of large debris. NMPs and LMPs were susceptible to further fragmentation and downsizing, implying that MPs abundance in the Qing River tended to rise and SMPs might enriched. In addition, alteration of MPs fragmentation and stability reflected that the likely input source was wastewater treatment plant and atmospheric deposition before rainfall, whereas soil and road dust were possible sources after rainfall. The pollution risk assessment defined the MPs pollution risk of Qing River as low level and decreased after rainfall. This study demonstrated that rainfall substantially influences MPs organization in urban river and provided empirical support for MPs environmental behavior under influence of natural and anthropogenic factors.

Use of whole-cell bioreporters to assess bioavailability of contaminants in aquatic systems.

Water contamination has become increasingly a critical global environmental issue that threatens human and ecosystems’ health. Monitoring and risk assessment of toxic pollutants in water bodies is essential to identifying water pollution treatment needs. Compared with the traditional monitoring approaches, environmental biosensing via whole-cell bioreporters (WCBs) has exhibited excellent capabilities for detecting bioavailability of multiple pollutants by providing a fast, simple, versatile and economical way for environmental risk assessment. The performance of WCBs is determined by its elements of construction, such as host strain, regulatory and reporter genes, as well as experimental conditions. Previously, numerous studies have focused on the design and construction of WCB rather than improving the detection process and commercialization of this technology. For investigators working in the environmental field, WCB can be used to detect pollutants is more important than how they are constructed. This work provides a review of the development of WCBs and a brief introduction to genetic construction strategies and aims to summarize key studies on the application of WCB technology in detection of water contaminants, including organic pollutants and heavy metals. In addition, the current status of commercialization of WCBs is highlighted.

Groundwater pollution risk assessment using a calculated contamination index and geostatistical analysis: Jerba Island case study (southeast of Tunisia)

Groundwater pollution risk assessment using a calculated contamination index and geostatistical analysis: Jerba Island case study (southeast of Tunisia)

Comparison of Pollution Levels, Biomagnification Capacity, and Risk Assessments of Heavy Metals in Nearshore and Offshore Regions of the South China Sea.

Seawater and fish were collected from nearshore (Pearl River Estuarine, PRE) and offshore (middle of the South China Sea, MSCS) regions of the South China Sea (SCS) to determine the heavy metals (HMs) pollution status and biomagnification characteristics. Results show that Cu in PRE seawater was moderately contaminated. Overall pollution risk of seawater were PRE (3.32) > MSCS (0.56), whereas that of fish was MSCS (0.88) > PRE (0.42). δ13C and δ15N exhibited distinguished characteristics for PRE and MSCS fish, indicating the diverse energy sources, nitrogen sources, and food web structures of nearshore and offshore regions. Cu was biomagnified whereas Pb and Ni were biodiluted in offshore fish. Hg presented significant biomagnification in both of nearshore and offshore fish. Finally, the target hazard quotient of Hg (1.41) in MSCS fish exceeded the standard limit, which was posed by high Hg concentration and consumption rate of offshore fish.

Atmospheric dispersion of chemical, biological, and radiological hazardous pollutants: Informing risk assessment for public safety

Modern society is confronted with emerging threats from chemical, biological, and radiological (CBR) hazardous substances, which are intensively utilized in the chemical, medical, and energy industries. The atmospheric dispersion of released CBR hazardous pollutants can influence a large percentage of the population owing to their rapid process with extensive spatial coverage. It is important to comprehensively understand the behaviors of the released CBR pollutants in the atmosphere to fully evaluate the risks and protect public safety. In this study, we reviewed the advancements in the atmospheric transport of CBR pollutants, including the urban atmospheric boundary layer, unique concepts, and models for CBR pollutants. We underlined the development of innovative methodologies (e.g., inverse estimation and data assimilation methods) for the atmospheric transport of accidentally released CBR pollutants to reduce uncertainties in emissions and accumulated errors during dispersion by combining numerical models with monitoring data. Finally, we introduced progress in quantitative risk assessment, including exposure assessment and dose-response relationships for CBR hazardous pollutants. A framework, source, assimilation, fundamentals, exposure, and risk (SAFER), has been proposed to integrate the key components in the risk assessment of airborne CBR hazardous pollutants. These methods and models can contribute to effective risk preparedness, prevention, evidence-based policymaking, and emergency response to airborne CBR pollutants.

Chemical profile and toxicity of the leachates from aged plastics under simulated conditions

Marine organisms are prone to be exposed to leachates from aged plastics. However, the ecological risk of leachates from aged plastics remains elusive. In this study, the chemical profile and toxicity of leachates from aged plastics under simulated seawater (SW) and fish digest (FD) conditions were respectively investigated by chemical analyses and bioassays. Overall, 371 additives were identified in the leachates from 15 aged plastics, with the FD leachates containing nearly half as many identified additives as the SW leachates. In terms of toxicity, 20% of the FD leachates inhibited the bioluminescence of the recombinant Escherichia coli, while 16.7% of the SW leachates stimulated the bioluminescence. Besides, the heart rate of marine medaka (Oryzias melastigma) embryos was significantly accelerated by 66.7% of the FD leachates and 53.3% of the SW leachates. In general, the FD leachates had fewer identified additives and lower concentrations but elicited higher toxicity than the SW leachates. Furthermore, the leachates induced higher genotoxicity in O. melastigma embryos than in larvae. Compared with the virgin plastics, the aging process potentially promoted the leaching of additives, but exerted relatively lower toxicity on E. coli and O. melastigma larvae. This study has offered a comprehensive understanding of the chemical profile and toxicity of the leachates from plastics under virgin and aged status, which facilitates the risk assessment of marine plastic pollution.

Pollution levels, sources and risk assessment of polycyclic aromatic hydrocarbons in farmland soil and crops near Urumqi Industrial Park, Xinjiang, China

This study investigated the concentration, source, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in farmland soil and crops around the Urumqi Industrial Park in Xinjiang, China. The total concentration of 16 different PAHs in the soil (Quantity: 51) and crop (Species: onion, cabbage, coriander, beans, spinach, celery, lettuce, and sunflower) samples ranged between 2.32 and 225.11 ng/g and between 132.44 and 504.03 ng/g respectively, with average values of 39.29 ± 2.39 ng/g for the soil samples and 295.81 ± 105.00 ng/g for the crop samples. The source analysis of PAHs was performed using the positive matrix factorization and ratio method and identified the high-temperature combustion of fossil fuels, the volatilization of petroleum, coke oven emissions, and traffic emissions as main sources of PAHs in soil. The ecological risk posed by the PAHs detected in the soil samples was within a safe range. The incremental lifetime cancer risk (ILCR) value quantifies resulting from human exposure to soil containing PAH is at a safe level except for the potential carcinogenic risk to children due to ingestion exposure (ILCRs > 1.0 × 10–6). The ILCR posed by crops exceed 1.0 × 10–6 and the risk from sunflower crop was the highest. The highest ILCR values for each crop high exposed for the adult female population. These results indicate that the farmland soil and crops near the Urumqi Industrial Park have been contaminated by PAHs and require urgent remediation to minimize adverse effects of exposure to carcinogens.

Multi-air pollution risk assessment in Southeast Asia region using integrated remote sensing and socio-economic data products

Air pollution has massive impacts on human life and poor air quality results in three million deaths annually. Air pollution can result from natural causes, including volcanic eruptions and extreme droughts, or human activities, including motor vehicle emissions, industry, and the burning of farmland and forests. Emission sources emit multiple pollutant types with diverse characteristics and impacts. However, there has been little research on the risk of multiple air pollutants; thus, it is difficult to identify multi-pollutant mitigation processes, particularly in Southeast Asia, where air pollution moves dynamically across national borders. In this study, the main objective was to develop a multi-air pollution risk index product for CO, NO2, and SO2 based on Sentinel-5P remote sensing data from 2019 to 2020. The risk index was developed by integrating hazard, vulnerability, and exposure analyses. Hazard analysis considers air pollution data from remote sensing, vulnerability analysis considers the air pollution sources, and exposure analysis considers the population density. The novelty of this study lies in its development of a multi-risk model that considers the weights obtained from the relationship between the hazard and vulnerability parameters. The highest air pollution risk index values were observed in urban areas, with a high exposure index that originates from pollution caused by human activity. Multi-risk analysis of the three air pollutants revealed that Singapore, Vietnam, and the Philippines had the largest percentages of high-risk areas, while Indonesia had the largest total high-risk area (4361 km2). Using the findings of this study, the patterns and characteristics of the risk distribution of multiple air pollutants in Southeast Asia can be identified, which can be used to mitigate multi-pollutant sources, particularly with respect to supporting the clean air targets in the Sustainable Development Goals.

Pollution index assessment of surface water and sediment quality with reference to heavy metals in Teesta River in Eastern Himalayan range, India

Assessment of heavy metals in water and sediment samples were done from six locations during monsoon and winter seasons in Teesta River in Eastern Himalayas. Three-way ANOVA was used to analyze seasonal, temporal and spatial variations in metals concentration in both water and sediment samples. Downstream sites exceeded the Indian River System prescribed concentration limits for cadmium, chromium, lead and zinc. Risk assessment of heavy metal pollution using heavy metal pollution index (HPI) and degree of contamination (Cdeg) indices revealed the upstream site S1 having the lowest HPI. Downstream site S3 showed the highest HPI of 68.24 and 44.82 during monsoon and winter respectively. Good water quality was indicated at site S1 compared to high to medium range pollution in downstream sites. Cdeg for sediments signalled sites S3 and S6 as moderately polluted. Correlation analysis of heavy metals exhibited a strong correlation among all heavy metals except Cd (water) and Cd and Pb (sediment) indicating a possible common origin. Cluster analysis based on metal concentrations identified two groups each for water and sediment sites. For water, group 1 comprised of S1 and S2 and the other group comprised of S3, S4, S5 and S6. For sediment samples, S1 was separated from the remaining five sites. Principal Component Analysis evinced high concentrations of Cu, Co and Zn at S3; Cd, Cu and Pb at S5; and Cu and Co at S6. S1 seemed devoid of heavy metals indicating anthropogenic input at downstream sites. The study indicated the river being vulnerable to various point and non-point sources of pollution, exacerbated by expanding small and large-scale industries. This study offers potential for extrapolation to design effective management policies to minimize pollution load in the Teesta River in order to improve the ecological health of the river.

Pollution, sources, and human health risk assessment of heavy metals in urban areas around industrialization and urbanization-Northwest China

Heavy metal pollution in urban soils and dust is mostly caused by extensive anthropogenic activity during urbanization and industrialization. In this research study, the pollution characteristics, sources, ecological and human health risks of heavy metals in urban soil, and dust have been thoroughly evaluated. The research findings demonstrate that dust has a higher level of contamination than urban soil, such as Pb, Cu, and Zn metals are more contaminated in both urban soil and dust throughout the city, and Hg and As are also found in locations with a high concentration of heavy industrial companies. This implies that traffic emissions are still a significant source of metals in urban areas, though industrial companies also contribute. The health risk assessment model used to calculate human exposure revealed that the non-carcinogenic and carcinogenic risks of selected metals in soil and dust were generally in the low range, except for the carcinogenic risk from Cr in children. Statistical analysis revealed that Cr and Ni concentrations were mainly of natural origin, Cu and Zn have been sourced from traffic, whereas Pb, Hg, and As have been sourced from industrial activities. The overall recommendation is that the road traffic environment and municipal construction facilities need to be improved to ensure the sustainable development of the city's environment, while pollution from industrial waste is strongly controlled.

Sludge-based baking-free brick prepared by sewage sludge with high moisture content: Influence of process parameters and environmental risk assessment

The high-water content and difficult dehydration of sewage sludge are the main factors restricting its disposal and application in China. In the paper, the sludge-based baking-free brick (SBFB) was made from sludge and fly ash - carbide slag - desulfurization gypsum with a certain amount of aggregate using compaction forming technology. The influence of process parameters (e.g., sludge content, aggregate content, molding pressure, curing method and curing temperature) on the properties of SBFB were investigated. Additionally, the environmental risk assessment of heavy metals and organic pollution of SBFB samples were carried out. The results indicated that when the sludge content was less than 30 %, the SBFB strength reaches 13.7 MPa under wet-heat cycle curing, which can meet the national standard of nonbearing wall for building bricks. According to the analysis of SEM and XRD, mullite and silicalite crystals were needle-like structures, which made the sludge particles closely linked with solid waste and compact structure. The appearance of these crystal structures was the internal driving force for the later strength of SBFB. Values of risk assessment criteria decreased through solidification treatment, in which Cd decreased to no risk, As, Pb, Zn decreased to low risk, Cu, Ni had moderate risk. All heavy metals were within China standards (GB5085.3–2007). Compared with sludge, the degradability of protein under curing conditions was greater than 77.35 % because of the decomposition of proteins in gel reaction system.

Distribution and risk assessment of toxic metal pollution in the soil and sediment around the copper mine

Background: Industrial pollution of metals is a serious environmental concern. The presence of Sarcheshmeh copper (Cu) mine and the possibility of soil pollution, were the primary motivations for evaluating heavy metals in this area. Methods: A total of 171 soil and 10 sediment samples were collected randomly from the study area for Cu, aluminum (Al), molybdenum (Mo), lead (Pb), and cadmium (Cd) determination. The USEPA method was used to acid digest soil samples, and metals present in the samples were detected using atomic absorption spectroscopy. Results: By measuring metal concentrations and calculating the geo-accumulation index (Igeo), enrichment factor (EF), and contamination factor (CF), the level of soil pollution by metals was assessed. It was found that soil and sediment samples were contaminated with Cu and the pollution decreased from the mine to Rafsanjan city, indicating that the pollution was anthropogenic. The soil has not been poisoned by Al or non-natural states because it was alkaline. Sediment samples were less than moderately polluted by Mo and Pb, but Cd and Cu were more problematic. Conclusion: Increasing the distance from the Cu mine resulted in a decrease in toxic metal concentration. The study concludes that by monitoring and filtering wastewater from the Cu mine, pollution caused by trace elements in the soil can be greatly reduced.

Characteristics, sources and risk assessments of heavy metal pollution in soils of typical chlor-alkali residue storage sites in northeastern China.

In this study, thirty-four soil samples from a typical chlor-alkali slag residue storage site near the city of Qiqihar in northeastern China were collected and their arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc concentrations were determined. Sources of these heavy metals were analyzed with a positive matrix factorization model, and the health risks associated with different pollution sources were calculated. The results showed that mercury was the main heavy metal pollutant at the site (maximum concentration of 112.19 mg.kg−1) and the soil was also contaminated with arsenic, copper and lead. The sources of eight heavy metals were: mixed oil refinery wastewater and parent material (arsenic, chromium, copper and lead), vinyl chloride waste source (mercury), parent material (cadmium, nickel and zinc). The average potential ecological risk of the soil was 22344.39, with vinyl chloride waste source contributing 99.85% of this risk. The average carcinogenic risk of a mixture of oil refinery wastewater and parent material for children and adults was 9.06×10−6 and 6.36×10−6, respectively, accounting for 99.9% (children) and 99.48% (adults) of the total average carcinogenic risk. The average hazard index of vinyl chloride waste source for children and adults was 0.6 and 0.38, respectively, which accounted for 64.13% (children) and 52.34% (adults) of the total hazard index. These results provide a reference for soil pollution risk assessments at this type of site.