Risk Assessment of Metals in Urban Soils from a Typical Industrial City, Suzhou, Eastern China

Review of soil environment quality in India near coal mining regions: current and future predictions

Production and utilization of coal are one of the primary routes of accumulation of Toxic Elements (TEs) in the soil. The exploration of trends in the accumulation of TEs is essential to establishing a soil pollution strategy, implementing cost-effective remediation, and early warnings of ecological risks. This study provides a comprehensive review of soil concentrations and future accumulation trends of various TEs (Cr, Ni, Pb, Co, Cu, Cd, Zn, Fe, Mn, and As) in Indian coal mines. The findings revealed that average concentrations of Cr, Mn, Ni, Cu, Zn, Pb, and Co surpass India's natural background soil levels by factors of 2, 4.05, 5.32, 1.77, 9.6, and 6.15, respectively. Geo-accumulation index values revealed that 27.3%, 14.3%, and 7.7% of coal mines are heavily polluted by Ni, Co, and Cu, respectively. Also, the Potential Ecological Risk Index indicates that Cd and Ni are primary contaminants in coal mines. Besides, the health risk assessment reveals oral ingestion as the main exposure route for soil TMs. Children exhibit a higher hazard index than adults, with Pb and Cr being major contributors to their non-carcinogenic risk. In addition, carcinogenic risks exist for females and children, with Cr and Cu as primary contributors. Multivariate statistical analysis revealed that TEs (except Cd) accumulated in the soil from anthropogenic sources. The assessment of future accumulation trends in soil TE concentrations reveals dynamic increases that significantly impact both the ecology and humans at elevated levels. This study signifies a substantial improvement in soil quality and risk management in mining regions.

Human health risk assessment due to mercury use in gold mining areas in the Ecuadorian Andean region

Mining activity drives economic development and has established itself as one of the main industrial spheres globally. However, illegal, and artisanal gold mining, which uses mercury (Hg), is a major source of global pollution. Hg is highly toxic and persistent in the environment, affecting human health and the ecosystem. The objective of this research is to; (a) analyze Hg concentrations in surface waters of nine provinces of the Andean region of Ecuador and compare them with the maximum permissible limits of Ecuadorian regulations, and (b) evaluate the health risk of people exposed to waters with high Hg content through residential and recreational scenarios. In this study, 147 water samples from rivers and streams were analyzed. The results revealed worrying levels of Hg, especially in the provinces of Azuay and Loja where Hg values of up to 0.0913 mg/L and 0.0387 mg/L, respectively, were detected. In addition, it was found that 45% of the samples did not meet the water quality criteria for the preservation of aquatic life, which represents a severe risk to the ecosystem. The probabilistic risk analysis yielded values that exceeded the acceptable exposure limit for adults and children in residential settings in Azuay and Loja, while in the recreational scenario the safe exposure limit was exceeded for both receptors only in the province of Azuay. The elevated presence of Hg in the provinces, mainly in Azuay and Loja, possibly related to illegal gold mining activity, represents a threat to water quality and aquatic life in the Andean region of Ecuador. Children are especially vulnerable, and effective regulation is required to ensure the safety of the population. This study provides valuable information for decision makers regarding the risk associated with Hg exposure in areas of mining activity in the Ecuadorian Andean region. In addition, it can contribute to the development of policies and strategies to control contamination in mining environments and protect human and environmental health in the region.

Extraction methods optimization of available heavy metals and the health risk assessment of the suburb soil in China

Heavy metal pollution has attracted increasing concern due to its high toxicity and persistence. A suitable extraction procedure for available heavy metals in soil is necessary for assessing the ecological risk. In this work, the single extraction methods aided by shaking and microwaves were investigated and analyzed for their ability to extract available heavy metals from soil samples, and a total of 42 soil samples were collected from suburbs of Zhengzhou city in China. The extraction efficiency of Cu, Zn, As, and Cd in the certified fluvo-aquic soil was compared using eight different types of solutions: CaCl2, CH3COONH4, NH4NO3, CH3COOH, Na2EDTA, DTPA, HNO3, and NH4H2PO4. Results indicated that the shaking-assisted method that utilized Na2EDTA as an extractant demonstrated satisfactory efficiency and was chosen for further optimization and that the optimal conditions were obtained using 0.05 M Na2EDTA at pH 7, soil-liquid ratio 1:20, and extraction duration 2 h, which gained the perfect extraction efficiency ranging from 85.8 to 109.5%. The proposed approach has been applied to extract available Cu, Zn, As, and Cd in soils of Zhengzhou suburbs, where the mean values varied from 0.129 to 6.881 mg/kg. The bioavailability of different heavy metals in the soil varies greatly, with Cd having the highest activity in the survey region. Significant (p < 0.01) positive relationships were observed between the available state and the total amount of all the heavy metals. The assessment of health risks associated with heavy metals indicated that there was no risk for chronic non-carcinogenic effects. Even though the total amount of metal elements in suburban soil of Zhengzhou is 1.6% with high carcinogenic risk, the risk of available elements is still within the acceptable range, which verified that the risk grade obtained by the total amount is higher than the actual risk.

Health risk assessment of dietary cadmium intake in children aged 2-17 years in East China

Food is the main way for people to be exposed to heavy metal cadmium (Cd), and Cd pollution will affect human health. In this paper, exposure and health risk assessment of dietary Cd intake were conducted in children aged 2, 3, 4, 5, 6-8, 9-11, 12-14 and 15-17 years in East China. The results showed that the total exposure of dietary Cd intake in children exceeded the standard limits. The total exposure of all age groups were 1.11 × 10-3, 1.15 × 10-3, 9.67 × 10-4, 8.75 × 10-4, 9.18 × 10-4, 7.75 × 10-4, 8.24 × 10-4, 7.11 × 10-4 mg kg-1 d-1, respectively, and the highest was the children aged 3 years. The hazard quotients of children aged 2 and 3 years were 1.11 and 1.15, respectively, at an unacceptable health risk level. The hazard quotients of dietary Cd intake in children of other ages were less than 1, at an acceptable health risk level. Staple foods were the most significant contributor to the dietary Cd intake in children, and the contribution ratio of non-carcinogenic risk of dietary Cd intake in all age groups were more than 35%, the proportion of non-carcinogenic risk in children aged 6-8 and 9-11 years were as high as 50%. This study provides scientific basis for the health of children in East China.

Pollution and health-risk assessments of Cr-contaminated soils from a tannery waste lagoon, Hebei, north China: With emphasis on Cr speciation

In this paper, heavy metals (i.e., V, Cr, Co, Cu, Zn, Cd, Pb, and Sb) in soils from a tannery waste lagoon, Hebei, north China were investigated. Element concentrates were determined by a portable X-ray fluorescence in situ and an inductively coupled plasma mass spectrometry in the lab. Two sets of indexes, including geological accumulation index, contamination factor, and pollution load index, and hazard quotient and total carcinogenic risk were adopted to evaluate the pollution and health-risk of heavy metals. A scanning electron microscopy in conjunction with an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy was used to observe chromium occurrence and speciation. With an average of 6493.11 mg/kg, chromium contents in the lagoon soils reached up to 12971.19 mg/kg, 211-times higher than the threshold of Chinese soils (61.00 mg/kg). Elevated Cr contents resulted in significantly high pollution and noncarcinogenic and carcinogenic risks in the studied area. Chromium in most soils occurred predominately as Cr³⁺ (60-74%), and to a lesser extent, Cr⁶⁺. The mechanism responsible for decreasing Cr⁶⁺ percentages in soils with increasing depth was summarized: Cr⁶⁺ favors aqueous environment; soil moisture decreased with increasing depth; in soils especially in the lower portion, Cr⁶⁺ was reduced by Fe⁰ and Fe², transforming into Cr³⁺ and Fe³⁺. In addition, the alkaline condition promoted Cr³⁺ to precipitate, resulting more Cr³⁺ absorbing in soils. The intimate association of Cr and Fe in soils (i.e., Cr mainly occurred in Fe oxides and dolomite) further confirmed our assumptions. A combined application of microorganism (e.g., Aeromonas hydrophila) and biochar (prepared from maize stalk or peanut shells) were recommended to alleviate Cr pollution in the soils.

Contamination Assessment and Potential Human Health Risks of Heavy Metals in Urban Soils from Grand Forks, North Dakota, USA

Heavy metal (HM) pollution of soil is an increasingly serious problem worldwide. The current study assessed the metal levels and ecological and human health risk associated with HMs in Grand Forks urban soils. A total 40 composite surface soil samples were investigated for Mn, Fe, Co, Ni, Cu, Zn, As, Pb, Hg, Cr, Cd and Tl using microwave-assisted HNO3-HCl acid digestion and inductively coupled plasma mass spectrometry (ICP-MS) analysis. The enrichment factor (EF), contamination factor (CF), geoaccumulation index (Igeo), ecological risk and potential ecological risk index were used for ecological risk assessment. The park soils revealed the following decreasing trend for metal levels: Fe > Mn > Zn > Cr > Ni > Cu > Pb > As > Co > Cd > Tl > Hg. Based on mean levels, all the studied HMs except As and Cr were lower than guideline limits set by international agencies. Principal component analysis (PCA) indicated that Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Pb, Cr and Tl may originate from natural sources, while Hg, Pb, As and Cd may come from anthropogenic/mixed sources. The Igeo results showed that the soil was moderately polluted by As and Cd and, based on EF results, As and Cd exhibited significant enrichment. The contamination factor analysis revealed that Zn and Pb showed moderate contamination, Hg exhibited low to moderate contamination and As and Cd showed high contamination in the soil. Comparatively higher risk was noted for children over adults and, overall, As was the major contributor (>50%), followed by Cr (>13%), in the non-carcinogenic risk assessment. Carcinogenic risk assessment revealed that As and Cr pose significant risks to the populations associated with this urban soil. Lastly, this study showed that the soil was moderately contaminated by As, Cd, Pb and Hg and should be regularly monitored for metal contamination.

Microbial community profiling in bio-stimulated municipal solid waste for effective removal of organic pollutants containing endocrine disrupting chemicals

The study was aimed to improve the degradation of organic pollutants in municipal solid waste (MSW) through the bio-stimulation process. The results showed that the physico-chemical properties of MSW (control) had a high value of pH (9.2 ± 0.02); total suspended solids (TSS: 1547 ± 23 mg/kg^-1), and total dissolved solids (TDS:76 ± 0.67 mg/kg^-1). After the biostimulation process (biostimulated MSW), the physico-chemical parameters of MSW were reduced as pH (7.1 ± 0.01); TSS (41 ± 0.01 mg/kg^-1), and TDS (789 ± 03 mg/kg^-1). Furthermore, the major organic pollutants detected from MSW by gas chromatography-mass spectroscopy (GC-MS) analysis at different retention time (RT) were hexadecane (RT-8.79); pentadecane (RT-9.36); and hexasiloxane (RT-9.43) while these organic pollutants were degraded after the biostimulation process. The whole-genome metagenome sequencing size (%) analyses showed major groups of bacteria (40.82%) followed by fungi (0.05%), virus (0.0032%), and archaea (0.0442%) in MSW. The species richness and evenness of the microbial community were decreased substantially due to the biostimulation treatment. The total number of genes in the biostimulated MSW (PS-3_11267) sample were 465302 whereas the number of genes in the control MSW (PS-4_11268) sample were 256807. Furthermore, the biostimulated MSW (PS-3_11267) aligned the reads to bacteria (19502525), fungi (40030), virus (3339), and archaea (12759) genomes whereas the control sample (PS-4_11268) aligned the reads to bacteria (17057259), fungi (19148), virus (1335), and archaea (18447) genomes. Moreover, the relative abundance at genus level in biostimulated MSW (PS-3_11267) (Ochrobactrum and Phenylobacterium), phylum; (Proteobacteria and Actinobacteria), and species (Chthoniobacter flavus and Vulgatibacter incomptus) level was the most abundant. The results provided valuable information regarding the degradation of organic pollutants in MSW by microbial communities through biostimulation for the prevention of soil pollution and health protection.

Distribution of heavy metals in surface soil near a coal power production unit: potential risk to ecology and human health

Coal thermal power plants are the dominant factor in producing various hazardous elements in surrounding surface soil, resulting in a significant human health hazard. In the current study, the seasonal (pre- and post-monsoon) concentration of As, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Ni, Pb, and Zn in surface soil around coal power production unit was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). The possible health risks throughout multiple exposure routes, i.e., ingestion, dermal, and inhalation were estimated for adult and children. Furthermore, geo-accumulation index (Igeo), enrichment factor (EF), pollution factor (CF), ecological risk index, and pollution load index (PLI) were applied to interpret the environmental pollution in the study area. The geospatial distribution pattern was computed to understand the trace and hazardous element distribution in the surface soil. As a result, the concentration of Fe (mg/kg) in pre-monsoon (15,620) and post-monsoon (27,180), Ni (mg/kg) in pre-monsoon (19.8), and post-monsoon (81.7) was found above the standard limits of soil prescribed by the WHO and FAO. Enrichment factor was observed between 0.95-6948 (pre-monsoon) and 0.53-116.09 (post-monsoon). The ecological risk index was found moderate to considerable for As and Cd metals during both seasons. In addition, the average PLI value was observed high for both seasons indicating the contamination of the study area with heavy metals. Moreover, Igeo values for Fe, Mg, and As were found relatively high. Conversely, health risks to the human population were found within the USEPA acceptable limits.

Comprehensive assessment of harmful heavy metals in contaminated soil in order to score pollution level

Soil-related problems have grown up to be a major threat to human society. Scientific evaluation is helpful to understand the status of soil pollution and provide reference to further work. In this situation, Liaoning Province, a typical industrial and agricultural province in Northeast China, was selected as a case study region. It reviewed 200 studies published between 2010 and 2020 and recorded related data of soil heavy metal. It used model method and index method to evaluate the agricultural region. The comprehensive assessment score of Liaoning pollution level was 0.8998. Dalian was 0.9536, ranking first among the 14 cities. Huludao and Jinzhou were 0.7594 respectively, ranked the last. Heavy metal accumulation in different cities stemmed from different sources, including weathering of parent materials, industrial wastes, sewage irrigation, and mining activities. In general, the pollution level of heavy metal in Liaoning was at low risk level, but it still needs to pay attention to the health risk of heavy metal and the input of heavy metal into the soil, especially cadmium (Cd). This study provides a comprehensive assessment of soil heavy metal pollution in Liaoning, while identifying policy recommendations for pollution mitigation and environmental management.

Potential Human Exposure to Mercury (Hg) in a Chlor-Alkali Plant Impacted Zone: Risk Characterization Using Updated Site Assessment Data

Industrial activities have resulted in severe environmental contamination that may expose rural and urban populations to unacceptable health risks. For example, chlor-alkali plants (CAPs) have historically contributed mercury (Hg) contamination in different environmental compartments. One such site (a burden from the Soviet Union) is located in an industrial complex in Pavlodar, Kazakhstan. Earlier studies showed the CAP operating in the second half of the twentieth century caused elevated Hg levels in soil, water, air, and biota. However, follow-up studies with thorough risk characterization are missing. The present study aims to provide a detailed risk characterization based on the data from a recent site assessment around the former CAP. The ⅀HI (hazard index) ranged from 9.30 × 10−4 to 0.125 (deterministic method) and from 5.19 × 10−4 to 2.54 × 10−2 (probabilistic method). The results indicate acceptable excess human health risks from exposure to Hg contamination in the region, i.e., exposure to other Hg sources not considered. Air inhalation and soil ingestion pathways contributed to the highest ⅀HI values (up to 99.9% and 92.0%, respectively). The residential exposure scenario (among four) presented the greatest human health risks, with ⅀HI values ranging from 1.23 × 10−2 to 0.125. Although the local urban and rural population is exposed to acceptable risks coming from exposure to Hg-contaminated environmental media, an assessment of contamination directly on the former CAP site on the industrial complex could not be performed due to access prohibition. Furthermore, the risks from ingesting contaminated fish were not covered as methyl-Hg was not targeted. An additional assessment may be needed for the scenarios of exposure of workers on the industrial complex and of the local population consuming fish from contaminated Lake Balkyldak. Studies on the fate and transport of Hg in the contaminated ecosystem are also recommended considering Hg methylation and subsequent bioaccumulation in the food chain.

Evaluation of nitrogen and heavy metal pollution in southern Caspian Sea: Risk assessment and modeling approach

Industrial, agricultural, and recreational activities dump several pollutants into the Caspian Sea, which is one of the main water bodies of Iran. Therefore, performing risk assessments would be required as part of the monitoring programs. Herein, non-cancer health risk assessment of the consumption of macroalgae was performed and the ecological risk assessment of metal pollution in sediments of the southern Caspian Sea was presented using sediment quality guidelines (SQGs), enrichment factors (EF), contamination factors (CF), contamination degrees (CD), pollution load indices (PLI), geo accumulation indices (I_geo), and potential ecological risk indices (RI). Next, machine-learning approaches were used to predict the stable isotope value of nitrogen in macroalgae, in which physicochemical information of water and heavy metal levels in macroalgae were used separately and together as predictor variables. Results indicated that simultaneous use of physicochemical properties of water and heavy metal levels resulted in the best prediction of isotopic nitrogen content.

Physicochemical and molecular characterization of heavy metal-tolerant bacteria isolated from soil of mining sites in Nigeria

Background

Mining for precious metals is detrimental to the composition of soil structure and microbial diversity distribution and is a health risk to human communities around the affected communities. This study was aimed at determining the physical and chemical characteristics and diversity of bacteria in the soil of local mining sites for biosorption of heavy metals.

Results

Results of physical and chemical characteristics showed mean pH values and percentage organic carbon to range from 7.1 to 8.2 and 0.18 to 1.12% respectively with statistical significance between sampling sites (P ≤ 0.05). Similarly, cation exchange capacity, electrical conductivity, moisture, total nitrogen, and carbon/nitrogen ratio (C:N) in the soil ranged between 1.52 to 3.57 cmol/kg, 0.15 to 0.32 ds/m, 0.14 to 0.82%, 0.10 to 0.28%, and 1.7 to 4.8 respectively. The highest heavy metal concentration of 59.01 ppm was recorded in soils obtained from site 3. The enumeration of viable aerobic bacteria recorded the highest mean count of 4.5 × 10⁶ cfu/g observed at site 2 with statistical significance (P ≤ 0.05) between the sampled soils. Alcaligenes faecalis strain UBI, Aeromonas sp. strain UBI, Aeromonas sobria, and Leptothrix ginsengisoli that make up 11.2% of total identified bacteria were able to grow in higher amended concentrations of heavy metals. The evolutionary relationship showed the four heavy metal–tolerant bacteria identified belonged to the phylum Proteobacteria of class Betaproteobacteria in the order Burkholderiales. Heavy metal biosorption by the bacteria showed Alcaligenes faecalis strain UBI having the highest uptake capacity of 73.5% for Cu.

Conclusion

In conclusion, Alcaligenes faecalis strain UBI (MT107249) and Aeromonas sp. strain UBI (MT126242) identified in this study showed promising capability to withstand heavy metals and are good candidates in genetic modification for bioremediation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-021-00251-x.

Interactive effects of natural and anthropogenic factors on heterogenetic accumulations of heavy metals in surface soils through geodetector analysis

The rapid socioeconomic development has led to severe pollution of urban soils by heavy metals. It is vital to identify and quantify the factors that affect trace-element pollution for better preventing and managing soil pollution. In this study, we collected 179 surface soil samples from Zhangzhou City in a coastal area of south China to determine the concentration of seven heavy metals (As, Cr, Cu, Hg, Ni, Pb, and Zn) and used the Nemerow Pollution Index (P_n) to estimate the level of heavy metal pollution in soils. Eighteen environmental factors, including six natural factors (e.g. soil properties, surface topography) and twelve anthropogenic factors (e.g. industry, road network, land use types and landscape pattern), were evaluated with the geodetector statistical method. The results indicate that the heavy metal contamination of soils in Zhangzhou City was highly heterogeneous. We found that the primary influencing factors for heavy metal concentrations were soil organic matter content, agriculture activities, and landscape pattern. Furthermore, the nonlinear relationship between the primary factors and their interaction factors enhanced soil contamination by the heavy metals. Among the anthropogenic factors, landscape pattern enhanced P_n the most when interacting with natural factor. In addition, the buffer zone should be considered when evaluating the effects of factors such as land use and landscape pattern, because the interactions between landscape pattern and slope aspect produce a maximum effect, accounting for 31.0% of the P_n value on the scale of 800 m. Based on this analysis, we identified the key factors of heavy metal pollution in the soils of Zhangzhou City and proposed strategic procedures for effective soil pollution prevention and treatment in the future.

Fractionation of Potentially Toxic Elements (PTEs) in Urban Soils from Salzburg, Thessaloniki and Belgrade: An Insight into Source Identification and Human Health Risk Assessment

Concentrations of potentially toxic elements (PTEs) (Al, As, Cd, Cr, Cu, Ni, Pb, and Zn) were measured in topsoil samples collected from parks in the cities of Salzburg (Austria), Thessaloniki (Greece), and Belgrade (Serbia) in order to assess the distribution of PTEs in the urban environment, discriminate natural (lithogenic) and anthropogenic contributions, identify possible sources of pollution, and compare levels of pollution between the cities. An assessment of the health risks caused by exposure to PTEs through different pathways was also conducted. The study revealed that, with the exception of Pb in Salzburg, levels of PTEs in the soils in polluted urban parks were higher than in unpolluted ones, but still lower than those recorded in other European soils. Results of sequential analyses showed that Al, Cr, and Ni were found in residual phases, proving their predominantly lithogenic origin and their low mobility. In contrast, the influence of anthropogenic factors on Cu, Pb, and Zn was evident. Site-dependent variations showed that the highest concentrations of As, Cu, Pb, and Zn of anthropogenic origin were recorded in Salzburg, while the highest levels of Al, Cr, and Ni of lithogenic origin were recorded in Belgrade and Thessaloniki, which reflects the specificity of the geological substrates. Results obtained for the health risk assessment showed that no human health risk was found for either children or adults.

Heavy metal accumulation and distribution in Phragmites australis seedlings tissues originating from natural and urban catchment

The retention of heavy metal (HM) was studied in root and rhizomes (BLG), stems (ST), and leaves (LF) of Phragmites australis (common reed) seedlings collected from different locations, differing in the scale of anthropogenic interference. The analysis includes the reference samples of sediments in uncontaminated lake Garczonki and contaminated roadside ditch in Cieplewo. The concentrations of Zn, Cu, Pb, Cd, Ni, and Cr were analyzed in plant tissues and sediments using the atomic absorption spectrometry and inductively coupled plasma mass spectrometry. The general assessment of sediments collected in the Garczonki lake showed a good environmental status; while in the roadside ditch in Cieplewo, the sediments were considerably polluted with HM. In the first stage of plant growth, all of the analyzed HMs are mainly inhibited by BLG system. The decreasing trend of elements was as follows: BLG > ST > LF. The organs followed different decreasing trends of HM concentration; the trend Zn > Cu > Ni > Cr > Pb > Cd was found in ST and LF for the Garczonki lake seedlings and for BLG and LF for the roadside ditch in Cieplewo seedlings. Zn showed the highest concentration, while Cd the lowest concentration in each of the examined organs. The bioaccumulation factor indicated the higher mobility of HM in seedlings in the Garczonki lake than in the roadside ditch in Cieplewo. The morphological studies suggest the good state and health of seedling from both sites; however, the reduction of root hair surface was observed for the roadside ditch seedlings. The anatomical studies present changes in the size of the nucleus and count of chloroplasts in LF. No reaction on HM contamination sediments in the seedlings from the roadside ditch in Cieplewo in the aerenchyma was noted. Potentially, both types of seedlings can be used to decontaminate environments rich in HM. However, the level of HM absorbed by seedlings (in the first stage of growth) should be considered due to the behavior in the target phytoremediation site.

How polluted are cities in central Europe? - Heavy metal contamination in Taraxacum officinale and soils collected from different land use areas of three representative cities

The level of environmental contamination can vary according to different types of land use. The aim of the present study was to determine the relations among Cd, Pb, Ni and Cr content in plants (Taraxacum officinale) and soils for 10 types of land use in the urban areas of representative cities for central Europe region (Warsaw, Poznan and Wroclaw in Poland). Descriptive statistical analysis, as well as cluster analysis and principal component analysis, heatmaps and Andrews curves, was performed to identify relations between HMs and land use, as well as differences between particular cities. The investigations revealed variation among sites, plant organs and cities. The content (mg kg^-1 DW) in soils, roots and leaves for Cd varied between 0.4 and 3.6, 0.4-2.8 and 0.5-3.9, Cr ranged between 23.2 and 40.6, 14.0-26.1 and 15.8-24.8, Ni varied between 2.1 and 13.2, 0.2-42.1 and 0.0-3.9, while Pb varied between 27.0 and 231.5, 4.3-34.2 and 3.0-9.5, respectively. It was possible to note some tendencies. Nickel was the element with the highest content in the roots (up to 42.1 mg kg^-1 DW) in comparison to leaves and soils and the highest bioaccumulation factor (up to 15.0). This means that the main source of Ni might be contamination of the soil. The cluster analysis of standardized HM levels in leaves revealed that cadmium is a different from the other three elements, which might be related to the translocation factor, for which this element was found to have the highest levels at many sites.

Stable isotope ratios (δ13C and δ15N) and heavy metal levels in macroalgae, sediment, and benthos from the northern parts of Persian Gulf and the Gulf of Oman

In this investigation, δ¹³C and δ¹⁵N isotope ratios and heavy metal levels were assessed in macroalgae, sediment samples, and benthic species from northern parts of the Persian Gulf and the Gulf of Oman. The highest δ¹⁵N values in algal samples (11±0.42), indicative of anthropogenic organic N inputs, were detected in the Sadaf region, whereas the lowest values (3.17 ± 0.12), indicative of anthropogenic inorganic inputs, were detected in the Parvaz region. In addition to sediment quality guidelines (SQGs), contamination factors (CF), enrichment factors (EF), contamination degree (CD), pollution load index (PLI), geo accumulation index (Igeo), and potential ecological risk index (RI) were employed to assess the anthropogenic influence on sediment quality and to describe the sensitivity of the biota to toxic heavy metals. The obtained results demonstrate that the analyzed elements (Mn, Cr, Ni, Pb, Zn, Cu, Co, and V) had no ecological risk in the sampling area.

Contamination, sources and risk assessments of metals in media from Anka artisanal gold mining area, Northwest Nigeria

Mining is a major human activity that has contributed significantly to high degree of environmental and human health degradation. This study was done to uncover the degree of contamination and risks associated with metals in environmental media collected from Anka area, Northwest Nigeria. A total of eighty-two (82) samples which include 42 soils, 22 stream sediments, 13 tailings and 5 plants were collected. Media were air-dried, pulverized and sieved to collect fine particles. They were digested and analyzed for toxic metal contents using High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometer (HPLC-ICPMS). Metals analyzed include As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Zn and Fe. From the results, degree of contamination in samples were obtained using pollution indices, while ecological and health risks were calculated using acceptable risk indices. Average concentrations of metals in the soils were: As: 0.64 μg/g; Cr: 42.55 μg/g; Pb: 131.76 μg/g; Hg: 0.85 μg/g while in sediments, the average concentration were As: 15.46 μg/g; Cr: 111.82 μg/g; Pb: 2234.02 μg/g; Hg: 2.12 μg/g. In tailings, the mean concentration were As: 4.79 μg/g; Cr: 96.95 μg/g; Pb: 2802.56 μg/g; Hg: 1.25 μg/g. Metals in plants are above acceptable limits. Metals in the media are both from geogenic and mining activities, and they pose high ecological risks. High carcinogenic (>10^-4) and non-carcinogenic (>1) health risks are associated with metals in media from this area. Further epidemiological studies should be carried to know the extent of occurrence of diseases associated with mining in the area.

Concentration, Spatial Distribution, Contamination Degree and Human Health Risk Assessment of Heavy Metals in Urban Soils across China between 2003 and 2019-A Systematic Review

This study provides an overview of the studies of heavy metal pollution regarding As, Cd, Cr, Hg, Pb, Cu, Zn and Ni in the urban soils throughout 71 cities of China, based on data from online literature, during the period 2003-2019. The concentrations, spatial distributions, contamination degrees and health risks of heavy metals in the urban soils were evaluated. The results demonstrated that the mean values of eight heavy metals all exceeded the soil background values in China, and the kriging interpolation method showed that the hot-spot cities with heavy metal contamination in urban soils were mainly concentrated in the southwest, southcentral, southeast coast, northcentral and northwest regions of China. The geoaccumulation index (Igeo) indicated that Hg and Cd were at moderate contamination levels and that the levels of the other six metals did not appear contamination. The pollution index (PI) showed that Cd and Hg reached high contamination levels, and the other metals reached moderate contamination levels. The integrated pollution index (IPI) and potential ecological risk index (PRI) indicated that the integral urban soils in the study areas ranked high contamination levels and moderate ecological risk degree, respectively, and Cd and Hg should be labeled as priority metals for control in the urban soils around China. The human health risk assessments for the heavy metals indicated that ingestion was the dominant exposure pathway for having adverse effects on human health. The mean Hazard index (HI) values of eight heavy metals all showed that adverse effects on human health were unlikely, and the mean carcinogenic (CR) values of As, Cr and Ni for children and adults all suggested an acceptable carcinogenic risk to human beings. In addition, children exposed to these heavy metals faced more serious non-carcinogenic and carcinogenic health threats compared to adults. The results could provide valuable information for demanding the better control of heavy metal pollution and mitigation of the adverse effects on residents by environmental regulators in national urban regions.

Potential ecological and health risks of toxic metals associated with artisanal mining contamination in Ijero, southwest Nigeria

This investigation was done to decide the concentrations, sources and potential risks of metals in media around Ijero area. A total of 80 samples including topsoils, sediments, tailings and whole plants were gathered from this territory while control samples were taken from zone with less human exercises. Samples were pounded, sieved and chemically analyzed utilizing Agilent High Plasma Liquid Chromatography Inductively Coupled Plasma-Mass Spectrometer. Results demonstrated that the mean concentrations of lead (Pb) and zinc (Zn) in soils are 30.61 and 123.71 µg/g individually. In tailings the mean distribution of Pb and Zn are 33.16 and 22.44 µg/g each. Toxic units in all media were less than 4, indicating low effect on the ecosystem. Bivariate correlation, hierarchical cluster and principal component analyses revealed that metals in media from this area originated from mining and mineral processing activities, mixed and geogenic sources. Study revealed that metals in the media pose high degree of contamination and moderate to high ecological hazard. Also, there is high cancer-causing hazard index (HI) (10^-6-10^-4) and non-cancer-causing (HI > 1) dangers which is more articulated in kids than the grown-ups. It is important to introduce measures that will decrease the negative impacts associated with mining in the area.

A case study on pollution and a human health risk assessment of heavy metals in agricultural soils around Sinop province, Turkey

In the present study, the concentration levels of heavy metals such as Cr, Fe, Ni, Cu, Zn, As and Pb in soil samples collected from 88 sampling locations around Sinop Province, Turkey were measured using energy dispersive X-ray fluorescence spectroscopy (EDXRF). To interpret and to evaluate the pollution status and distribution of heavy metals in soil, metal pollution parameters such as enrichment factor (EF), geo-accumulation index (I_geo), pollution factor (CF) and pollution load index (PLI) and geo-spatial distribution patterns were used. The mean concentrations of Cr, Fe, Ni, Cu, Zn, As, and Pb were found to be 194.73, 39,848.57, 85.02, 43.19, 65.10, 5.66, and 17.01 mg/kg, respectively. Results indicated that the mean concentrations of Cr, Ni, As, and Pb exceeded the world crustal average, with the exception of Fe, Cu, and As. Multivariate analysis results showed that Cr, Ni, Zn, As, and Pb levels in the investigated region were highly influenced by anthropogenic inputs such as agricultural practices. According to the health risk assessment model introduced by USEPA to evaluate the human health risks, the non-carcinogenic risk for children was above the threshold level, but low for adults. Total potential carcinogenic health risks for both children and adults in the study area were in acceptable range. Overall, when health risks are evaluated, it shows that children are more susceptible to non-carcinogenic and carcinogenic health effects of trace metals compared to adults.

Levels and human health risk assessment of heavy metals in surface soil of public parks in Southern Ghana

This study evaluates the extent to which humans may be exposed to health risk from heavy metals in surface soils of public parks in Southern Ghana during outdoor activities. The study investigated surface soils of 56 public parks from seven metropolitan cities in Southern Ghana. Heavy metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were determined using microwave-assisted HNO₃-HF acid digestion and atomic absorption spectroscopy with flame, graphite furnace, and cold vapor options. All parks studied registered the presence of heavy metals with mean concentrations following the order: Mn > Zn > Cr > Pb > Cu > Ni > Cd > Hg. Whereas the mean concentrations of Zn (221.92 mg/kg) and Cr (107.01 mg/kg) respectively exceeded the Canadian (200 mg/kg; 64 mg/kg) and the EU (100-200 mg/kg; 50-100 mg/kg) standards, the ranges of Cu (14.27-138.85 mg/kg) and Pb (6.46-628.31 mg/kg) also exceeded their EU range of 50-100 mg/kg. The results indicated that there was no immediate risk to Ni and Hg on the public parks studied; however, Pb, Cd, Zn, Cu, and Cr may pose some adverse effects as they exceed their respective guideline limits in soil. The ranges of non-carcinogenic risk for adults and children were 0.0186-0.0787 and 0.0197-0.0850 respectively while the corresponding ranges for carcinogenic risks were 3.75 × 10^-7-1.28 × 10^-6 and 4.17 × 10^-7-1.31 × 10^-6. Even though risk assessment suggested low and acceptable health risk levels to patrons, there is the need for close monitoring since Pb, Cd, Zn, Cu, and Cr have shown tendency of accumulating beyond acceptable limit.

A critical prospective analysis of the potential toxicity of trace element regulation limits in soils worldwide: Are they protective concerning health risk assessment? - A review

Trace elements (TEs) may have toxic effects to plants and humans; thus, countries and organizations impose maximum allowable regulation limits of their concentrations in soils. Usually such limits are placed in different categories according to soil use, soil properties or based on both attributes. However, some countries have regulation limits irrespective of differentiation in soil properties. In this review, we aimed at collecting TE regulation limits in soils from major countries and organizations around the globe, and critiquing them by assessing potential human health risks in the case of soils attaining the maximum allowable values. We explored the soil-to-human pathway and differentiated among three major exposures from TEs, i.e., residential, industrial and agricultural. We observed the existence of problems concerning TE regulation limits, among which the fact that limits across countries do not regulate the same TEs, not even a minimum number of TEs. This indicates that countries do not seem to agree on which regulation limits of TEs pose a high risk. Also, these regulation limits do not take into account TE mobility to neighbouring environment interphases such as plant, especially edible, and water matrices. Moreover, limits for same TEs are vastly diverse across countries; this indicates that those countries have conflicting information concerning TE-related health risks. Subsequently, we addressed this problem of diversity by quantifying resultant risks; we did that by calculating human health risk indices, taking into consideration the cases in which the highest allowable TE limits are attained in soil. Arsenic limits were found to generate a relatively high hazard quotient (HQ_i, accounting for human intake over the maximum allowable oral reference dose for that same TE), indicating that its risk tends to be underestimated. Other TE limits, such as those of Cd, Cu, Ni, Pb, and Zn typically result in low HQ_i, meaning that limits in their cases are rather overprotective. Our approach reveals the need of reducing diversity in regulation limits by drafting soil legislations of worldwide validity, since risks are common across countries. We suggest that new directions should strategically tend to (a) reduce limits of TEs with underestimated contribution to health risk (such as As), (b) cautiously increase limits of TEs that currently cause minor health risks, (c) quantify TE risks associated with uptake to edible plants and potable water, and (d) consider multi-element contamination cases, where risks are cumulatively enhanced due to TE synergism.

Heavy Metals in Sediments of Urban Streams: Contamination and Health Risk Assessment of Influencing Factors

Sediments of two urban streams in northern Poland outflowing to the Baltic Sea were assessed to explain the spatial variation in relation to urbanization level of the catchment, the role of retention tanks (RTs) and identification of pollution level. During the 3 month period of investigation sediment samples were collected from the inflow (IN) and outflow (OUT) of six RTs located on streams for flood protection. Six heavy metals (HMs) were investigated: Cu, Pb, Zn, Cd, Ni, Cr. The assessment of four geochemical enrichment indices used to quantify contamination of HMs in the sediments at IN and OUT samples was carried out. Contamination factor (CF), pollution load index (PLI), geoaccumulation index (Igeo) and potential ecological risk (RI) were calculated and the indices usefulness was assessed. Also, the hazard quotient (HQ) was calculated to assess health risk associated with dredging works. In sediments from RTs where paved surfaces constituted more than 70% of the catchment the HMs concentrations were from one to three times higher for Ni and from two to 143 times higher for Cu in comparison to soft catchment results. The extremely high Cu concentration (1114 mg/kg d.w.) found in sediments at RT Orłowska IN was most likely associated with large area of roofs covered with copper sheet. Calculation of CF, PLI, Igeo, RI, HQ indicators allows for a complex and multi-dimensional assessment of sediment status. Among these, CF and PLI classified the analyzed sediments as most polluted. Basing on the sedimentary HMs concentrations the health risk level via dermal exposure pathway was assessed as low.

Distribution and Health Risk Assessment of Trace Metals in Soils in the Golden Triangle of Southern Fujian Province, China

In recent years, intensified industrialization and rapid urbanization have accelerated the accumulation of trace metals in topsoils of the Golden Triangle of Southern Fujian Province in China. Trace metals can cause adverse impacts on ecosystems and human health. In order to assess the ecological and human health risks of trace metals in the Golden Triangle region and to determine the distribution and degree of pollution of trace metals, 456 soil samples were collected from 28 districts. The concentrations of six metals (As, Cr, Cu, Ni, Pb, and Zn) were analyzed to assess ecological risk using the geoaccumulation index (I_geo) and the potential ecological risk index (RI). The United States Environmental Protection Agency (USEPA) model was applied to calculate health risk. The average soil concentrations of the six elements are ranked as follows: As < Ni < Cu < Cr < Pb < Zn. Inverse distance weighting (IDW) interpolation maps showed that Cr, Cu, Ni, and Zn are enriched in the soils of developed areas, while As and Pb are enriched in the soils of undeveloped areas. The I_geo showed that the levels of metals in most soil samples are below polluting levels. Similarly, RI values indicated that trace metals pose low potential ecological risk in the region's soils. The Hazard Quotient (HQ) ranked the mean total noncarcinogenic risk of the six metals, for both children and adults, as follows: As > Pb > Cr > Ni > Cu >Zn. The mean carcinogenic risk (CR) of the metals in the region's soils are ranked as follows: Cr > As > Ni. The Hazard Index (HI) values indicated that 3.7% of soils contained unsafe levels of toxic metals for children and total carcinogenic risk (TCR) values indicated that 23.3% of soils contained unsafe levels, indicating that children are facing both noncarcinogenic and carcinogenic risks from trace metals. Principal component analysis (PCA) and matrix cluster analysis were used to identify pollution sources and classified trace metals and soil samples into two and five groups, respectively. The five groups represented the effects of different land use types, including agricultural area, residential and public area, industrial area, forest, and industrial area and roadside, based on the contents of trace metals in soils. Industrial, agricultural and traffic activities attribute to the enrichment of Cr, Cu, Ni, Pb, and Zn in the region's soils. Moreover, the accumulation of As and Pb are also attributed to atmospheric deposition. These results can contribute to a better understanding of pollution, ecological risks, and human health risks from trace metals on large regional scales like the Golden Triangle of Southern Fujian Province.

Metal and metalloid concentrations in soil, surface water, and vegetables and the potential ecological and human health risks in the northeastern area of Hanoi, Vietnam

Heavy metal and metalloid contamination and related risks for the environment and human health are matters of increasing concern. This study assessed metal and metalloid concentrations in soil, surface water, and locally grown vegetable to assess exposure and related risks for the environment and human health in the northeastern rural area of Hanoi. Concentrations of metals and metalloids in soils exceeded regulatory thresholds in some locations (e.g., Me Linh and Gia Lam districts). The carcinogenic elements As and Cr were identified as a major concern with concentrations up to 693 μg g^-1 and 147 μg g^-1, respectively. Industrial point sources or groundwater irrigation practices in the intensive organic farming areas were identified as potential factors contributing to the accumulation of carcinogenic metals and metalloids in topsoil layers. Metal and metalloid concentrations detected in water and vegetables were below the regulatory threshold levels (WHO guideline and maximum allowable limits). While contamination was not observed at a large geographical scale, local soil contamination in specific areas of agricultural importance could pose high ecological and human health-related risks with unclear long-term impacts. The highly carcinogenic soil contamination detected in this study may be a factor adding to the increased cancer incidence rate in Hanoi area, as the total carcinogenic risk calculated for Hanoi area exceeds the cancer likelihood threshold by a factor of 25. Further research is needed to examine potential links, and the involvement of both stakeholders and policy makers is needed to adequately evaluate the risks for Hanoi area and coordinate future remediation plans if risks are justified.