Concentration of heavy metals and trace elements in soils, waters and vegetables and assessment of health risk in the vicinity of a lignite-fired power plant

Heavy metal contamination of vegetables in China: status, causes, and impacts

Exposure to heavy metals from vegetable consumption poses a serious health risk to the Chinese population. The lack of knowledge on the overall status of vegetable contamination at the national level hinders the development of national regulations on preventing heavy metal exposure. To address this issue, the study presents an overview of heavy metal contamination in vegetables across China based on 96 peer-reviewed studies published over the past 20 years. The average concentrations of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn in the edible parts of vegetables are 3.7 ± 12.9, 1.6 ± 4.0, 4.3 ± 10.3, 18.6 ± 27.6, 164 ± 281, 4.5 ± 5.5, 7.7 ± 23.7, and 105 ± 283 mg kg-1 (dry weight), respectively. The associated daily exposures are 0.1-5.7, 0.1-1.7, 0.6-4.2, 4.1-20.5, 26-107, 0.7-3.0, 0.4-16.0, and 13-93 μg kg-1 d-1, respectively. General linear models explained 80%, 44%, 83%, 79%, 64%, 81%, 65%, and 55% of the total variance in As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn concentrations in vegetables, respectively, based on vegetable type and selected geological, meteorological, economic, and environmental factors. Agroforestry is the main source of heavy metal contamination, accounting for 3%-30% of the total variance in heavy metal concentrations in vegetables. Mining, smelting, refining, metalworking, and electrical equipment manufacturing are important source of As, Cr, Cu, Mn, Ni, and Pb, accounting for 7%-17% of the total variance.

Exploring the environmental risks and seasonal variations of potentially toxic elements (PTEs) in fine road dust in resource-based cities based on Monte Carlo simulation, geo-detector and random forest model

The environmental pollution caused by mineral exploitation and energy consumption poses a serious threat to ecological security and human health, particularly in resource-based cities. To address this issue, a comprehensive investigation was conducted on potentially toxic elements (PTEs) in road dust from different seasons to assess the environmental risks and influencing factors faced by Datong City. Multivariate statistical analysis and absolute principal component score were employed for source identification and quantitative allocation. The geo-accumulation index and improved Nemerow index were utilized to evaluate the pollution levels of PTEs. Monte Carlo simulation was employed to assess the ecological-health risks associated with PTEs content and source orientation. Furthermore, geo-detector and random forest analysis were conducted to examine the key environmental variables and driving factors contributing to the spatiotemporal variation in PTEs content. In all PTEs, Cd, Hg, and Zn exhibited higher levels of content, with an average content/background value of 3.65 to 4.91, 2.53 to 3.34, and 2.15 to 2.89 times, respectively. Seasonal disparities were evident in PTEs contents, with average levels generally showing a pattern of spring (winter) > summer (autumn). PTEs in fine road dust (FRD) were primarily influenced by traffic, natural factors, coal-related industrial activities, and metallurgical activities, contributing 14.9-33.9 %, 41.4-47.5 %, 4.4-8.3 %, and 14.2-29.4 % to the total contents, respectively. The overall pollution and ecological risk of PTEs were categorized as moderate and high, respectively, with the winter season exhibiting the most severe conditions, primarily driven by Hg emissions from coal-related industries. Non-carcinogenic risk of PTEs for adults was within the safe limit, yet children still faced a probability of 4.1 %-16.4 % of unacceptable risks, particularly in summer. Carcinogenic risks were evident across all demographics, with children at the highest risk, mainly due to Cr and smelting industrial sources. Geo-detector and random forest model indicated that spatial disparities in prioritized control elements (Cr and Hg) were primarily influenced by particulate matter (PM10) and anthropogenic activities (industrial and socio-economic factors); variations in particulate matter (PM10 and PM2.5) and meteorological factors (wind speed and precipitation) were the primary controllers of seasonal disparities of Cr and Hg.

Differences in soil bacterial community structure during the remediation of Cd-polluted cotton fields by biochar and biofertilizer in Xinjiang, China

Introduction

Heavy metal pollution is a major worldwide environmental problem. Many remediation techniques have been developed, these techniques have different performance in different environments.

Methods

In this study, soil sampling was conducted in multiple cotton fields in Xinjiang, China, and found that cadmium (Cd) was the most abundant soil heavy metal. Then, to find the most suitable technique for the remediation of Cd pollution in cotton fields, a two-year study was conducted to explore the effects of cotton straw-derived biochar (BC, 3%) and Bacillus-based biofertilizer (BF, 1.5%) on cotton Cd uptake and transport and soil microbial community structure under Cd exposure conditions (soil Cd contents: 1, 2, and 4 mg·kg-1).

Results

The results showed that the bioaccumulation coefficients (Cd content of cotton organs / soil available Cd content) of cotton roots, stems, leaves, and buds/bolls reduced by 15.93%, 14.41%, 23.53%, and 20.68%, respectively after the application of BC, and reduced by 16.83%, 17.15%, 22.21%, and 26.25%, respectively after the application of BF, compared with the control (no BC and BF). Besides, the application of BC and BF reduced the transport of Cd from soil to root system, and enhanced the diversity of soil bacterial communities (dominant species: Alphaproteobacteria and Actinobacteria) and the metabolic functions related to amino acid synthesis. It was worth noting that the differential species for BF group vs BC group including Alphaproteobacteria, Gemmatimonadetes, Bacilli, and Vicinamibacteria were associated with the enrichment and transport of Cd, especially the transport of Cd from cotton roots to stems.

Discussion

Therefore, the application of BC and BF changed the soil bacterial diversity in Cd-polluted cotton field, and then promoted the transport of Cd in cotton, ultimately improving soil quality. This study will provide a reference for the selection of soil heavy metal pollution remediation techniques in Xinjiang, China.

Review on heavy metal contaminants in freshwater fish in South India: current situation and future perspective

The primary natural resource we use in our daily lives for a variety of activities is freshwater for drinking and various developmental goals. Furthermore, the pace of human population increase worldwide is rising rapidly and has a great impact on the Earth's natural resources. Natural water quality has diminished owing to various anthropogenic activities. Water is crucial to the life cycle. On the other hand, chemical and agricultural industries pollute heavy metals. Acute and chronic diseases caused by heavy metals, such as slow metabolism and damage to the gills and epithelial layer of fish species, are divided into two categories. Pollutants can also harm liver tissues and result in ulceration as well as diseases such as fin rot, tail rot, and gill disease. The most prevalent heavy metals are As, Cr, Pb, and Hg, which are systemic toxicants that affect human health. These metals are categorized as carcinogens by the US Environmental Protection Agency and the worldwide agency for cancer research because they cause organ damage even at low exposure levels. The focus of the current study is to review various freshwater sources of heavy metal pollution.

Heavy metals contamination in vegetables irrigated with wastewater: a case study of underdeveloping regions of Pakistan

Irrigation of food crops with untreated wastewater leads to the accumulation of heavy metals in their edible parts. Exposure to toxic elements through consumption of contaminated vegetables even at very low concentration is becoming a serious problem for human health in many countries. This issue of heavy metals contamination needs great attention especially in Pakistan where irrigation by wastewater has become a common practice in urban and periurban areas. The present study was conducted to assess the contamination of different heavy metals including nickel (Ni), cadmium (Cd), lead (Pb) and chromium (Cr) in vegetables irrigated with wastewater in different districts of Punjab (Pakistan) like, Faisalabad, Lahore, Gujranwala, Sargodha, Sahiwal, Multan, Rawalpindi and Bahawalpur during years 2016-2019. The maximum contamination factor (Ni, 1.39; Cd, 5.86; Pb, 3.99; Cr, 2.24), pollution load index (2.92) and degree of contamination (13.48) were observed in wastewater irrigated agricultural soils of district Gujranwala as compared to other districts. Mean metal concentration in vegetables grown with untreated wastewater and transfer factor varied with plant type, frequency of irrigation and soils types/series of different districts of Punjab. The highest metal contamination was observed in Gujranwala where 44% vegetable samples were contaminated with Ni, 87% with Cd, 97% with Pb and 88% with Cr. Radar analysis and hierarchical cluster analysis showed that mustard leaves, spinach and lettuce were more contaminated vegetables compared to other vegetables. This study contributes to the evidence-based conclusion that cultivation of vegetable with untreated wastewater should be prohibited and required treatment of wastewater is needed.

Evaluation of radioactive and heavy metal pollution in agricultural soil surrounding the lignite-fired thermal power plant using pollution indices

Soil pollution caused by heavy metals negatively affects the environment and human health. However, the assessment of the environmental and ecological risks caused by heavy metals in agricultural soils in developing countries is limited. This study was carried out to determine heavy metal pollution and its possible sources in the agricultural lands surrounding the lignite-fired Afşin-Elbistan thermal power plant (TPP). A total of 52 soil samples were collected from the agricultural soils surrounding the TPP, and seven different heavy metal (U, Th, Ni, Fe, Cu, Cr and Zn) analyzes were performed on these samples. Soil samples were taken according to the prevailing wind direction. Nickel had a higher geoaccumulation index (1.40) and enrichment factor (5.09) values than the other metals. In addition, U posed a "moderate potential ecological risk" in the study area. Pearson correlation and principal component analyses showed that U, Ni, and Cr were controlled by anthropogenic sources.

Immobilization of cadmium in paddy soil using a novel active silicon-potassium amendment: a field experimental study

The rapid development of industrialization and agriculture has led to extensive environmental issues worldwide such as cadmium (Cd) pollution of paddy soils, posing a potential threat to environmental safety and food health. Therefore, there is an urgent need to reduce the Cd contents in paddy soils. In this study, a newly active silicon-potassium amendment was first prepared from potassium hydroxide-assisted potassium feldspar at a low temperature, and then was used to remediate a contaminated paddy soil by Cd over a long period. The obtained results demonstrated the effectiveness of the applied active silicon-potassium in promoting rice growth in the experimental field. In addition, soil pH values increased to 6.89-7.03, thus decreasing the bioavailability of Cd bioavailability by 8.61-13.7%. The soil enzyme activities and available nutrients (Si, Ca, Mg, N, and P) were also significantly increased. In particular, the Cd contents in the rice grains decreased from 0.279 to 0.179-0.194 mg/kg following the application of the active silicon-potassium amendment, reaching the food crop standard level of China (< 0.2 mg/kg). The detailed remediation mechanisms of the Cd-contaminated paddy soil involved several processes, including ion exchange, ligand complexation, electrostatic attraction, and precipitation. Overall, the active silicon-potassium material is a promising amendment for achieving effective control of Cd-contaminated paddy soils.

Geochemical distribution and environmental risk assessment of trace metals in groundwater released from e-waste management activities in Lahore, Pakistan

Non-sustainable e-waste recycling and dumping activities release trace metals into the ambient environment where they may threaten the biological communities and human health. A total of 45 groundwater and 21 leachate samples were collected from seven recycling, seven dumping, and one reference site in Lahore, Pakistan, and analyzed for Cu, Pb, Zn, Cd, Mn, and Fe in atomic absorption spectrophotometer. Comparing the results with the World Health Organization (WHO) standards of drinking water, only the concentrations of Cu, Zn, Mn, and Fe at all sites were found to be within the permissible limits, i.e., 2, 3, 0.5, and 1 mg/L, respectively. In leachates, only Cd and Mn at one site (0.204 and 8.636 mg/L, respectively) exceeded the allowable limits of National Environmental Quality Standards of Municipal and Liquid industrial effluents. Geo-accumulation index, contamination factor, contamination degree, and pollution load index values showed no to moderate contamination. The ecological risk index did not exceed 150, depicting low risk to nearby biological communities. The non-carcinogenic health risk assessment showed a hazard index value greater than 1 at all sites for children (2.04) and adults (1.52), with Pb being the major contributor to adverse health impacts via ingestion and dermal route. Children (1.21 × 10^-4) were at a more significant threat of carcinogenic risk from Pb and Cd as compared to adults (8.10 × 10^-5). Therefore, there is a dire need to introduce sustainable e-waste recycling and managing techniques to reduce further groundwater contamination via the percolation of trace metals and to reduce the current contamination level.

Trace elements in Foodstuffs from the Mediterranean Basin-Occurrence, Risk Assessment, Regulations, and Prevention strategies: A review

Trace elements (TEs) are chemical compounds that naturally occur in the earth's crust and in living organisms at low concentrations. Anthropogenic activities can significantly increase the level of TEs in the environment and finally enter the food chain. Toxic TEs like cadmium, lead, arsenic, and mercury have no positive role in a biological system and can cause harmful effects on human health. Ingestion of contaminated food is a typical route of TEs intake by humans. Recent data about the occurrence of TEs in food available in the Mediterranean countries are considered in this review. Analytical methods are also discussed. Furthermore, a discussion of existing international agency regulations will be given. The risk associated with the dietary intake of TEs was estimated by considering consumer exposure and threshold values such as Benchmark dose lower confidence limit and provisional tolerable weekly intake established by the European Food Safety Authority and the Joint FAO/WHO Expert Committee on Food Additives, respectively. Finally, several remediation approaches to minimize TE contamination in foodstuffs were discussed including chemical, biological, biotechnological, and nanotechnological methods. The results of this study proved the occurrence of TEs contamination at high levels in vegetables and fish from some Mediterranean countries. Lead and cadmium are more abundant in foodstuffs than other toxic trace elements. Geographical variations in TE contamination of food crops clearly appear, with a greater risk in developing countries. There is still a need for the regular monitoring of these toxic element levels in food items to ensure consumer protection.

Analyzing the relationship between product waste footprints and environmental damage - A life cycle analysis of 1,400+ products

A major problem for the circular economy is monitoring improvements in environmental sustainability. Measuring how much waste reduction efforts contribute to the decrease of environmental impact is difficult, because knowledge on whether life cycle waste amounts correlate with environmental damage is limited. In this article, product waste footprints are used to explore structural similarities and differences in associations with environmental damage. Using the waste flows linked to the production system of 1487 reference products from the Ecoinvent database, we found significant regression equations with R² of 0.75-0.89 between product waste footprints and potential impact on ecosystem diversity, human health and resource availability using log-transformed variables. For each 1 % increase in solid waste, potential impact on the environment increased by 0.75-0.84 %. This strong association between pre-consumer waste and environmental damage is particularly important for advocating for circular economy efforts at the point of consumption, where life cycle waste is invisible to consumers.

Biomagnification of potentially toxic elements in animals consuming fodder irrigated with sewage water

Globally, sewage water is considered a cheap and effective alternative source of irrigation and nutrient supplement. For example, in Faisalabad, Pakistan untreated sewage water loaded with potentially toxic elements (PTEs) is being routinely used to grow fodder crops in the peri-urban areas, where PTEs accumulate at different trophic levels and contaminate the food chain. Trophic transfer, bioaccumulation, and biomagnification of hazardous metals in food chains had toxic implications for human health. Currently, the major concern is associated with the consumption of PTEs contaminated fodder by animals and the subsequent translocation into humans via consumption of milk and meat from these animals. This study thus analyzed the concentration of Cd, Cu, Pb and Zn in sewage water, sewage irrigated soil, fodder is grown on such soils and the milk of cows and buffalos to calculate the transfer through water and fodder to animal milk. Overall, concentrations and bioaccumulation factors of Cd and Cu in buffalo milk were higher than the cow milk, whereas it was inverse for the concentration of Zn. Non-significant difference in the bioaccumulation factor for Pb in both buffalo and cow milk was observed. Calculation of the estimated daily intake indicated that there was no health risk associated with the consumption of tested milk samples. However, given the widespread exposure of infants to milk, continuous monitoring of milk quality is recommended to preclude a child's exposure to elevated levels of PTEs.

Study on the pore structure and radon release characteristics of coal in northern China

Identifying the release characteristics of radon (Rn-222) in coal mines is critical preventing cancer risks for coal miners and coal fires. The present investigates the pore structure characteristics of coal samples from eleven coal mines in northern China, using low-temperature nitrogen adsorption (LTNA) test, combined with the radon exhalation rate in coal. The findings of the study reveal that the N₂ adsorption isotherms of all the coal samples fall under the inverse S type, with micropores dominating in low-rank coals and mesopores dominating in the medium and high-rank coals, due to the separation of organic matter and quartz by shrinkage of micro-components and the orderly arrangement of aromatic rings as a result of ring condensation and thermal cleavage. The pore diameters of coal samples show similar distribution characteristics for sizes >2 nm, represented by a single peak near the pore diameter of 3 nm. Ash yield controls the mesopore and micropore volumes of medium and high-rank coal samples. The radon emission rate displays positive linear correlation (r² = 0.87) with micropore volumes of analyzed coal samples due to the infillings of free radon in micropores. The radon element is derived by uranium decay, which causes a greater radon exhalation rate of coal mines in areas near the uranium mines. The results of the present study could be helpful to understand the influence mechanism of radon emission processes in coal, which provides an important basis for reducing cancer risks for coal miners and predicting coal fires.

Multi-geostatistical analyses of the spatial distribution and source apportionment of potentially toxic elements in urban children's park soils in Pakistan: A risk assessment study

In the past few decades, contamination of urban children's parks (UCPs) with potentially toxic elements (PTEs) has been attracting more and more interest; however, assessment of eco-environmental and child exposure risks particularly in developing countries remains limited. The current study investigated PTE (Cr, Ni, Zn, As, Cd, and Pb) concentrations, potential sources, and their health risk assessment in UCP soils of 12 major cities in Pakistan. The results showed that the mean concentration of Ni exceeded the SEPA-permissible limit in all UCP sites, while other PTEs were found to be within acceptable limits. The soil properties such as pH, electrical conductivity, organic matter, and soil particles size were determined in UCPs soils. The contamination factor and pollution load index results indicated low to moderate pollution levels (CF < 3) and (PLI<1) for all PTEs except Ni in some of the selected cities. Quantile-quantile (Q-Q) plotting determined the normal distribution line for all PTEs in the UCPs. Principal component analysis showed the mixed sources of contamination from industrial emissions, fossil fuel combustion, vehicular emissions, wastewater irrigation, as well as solid waste disposal and natural sources of soil parent materials in all park sites. ANOVA results showed that all the PTEs except Cd had moderate to higher contamination values than the reference site. The risk assessment study revealed that children had high exposure to the selected PTEs via all exposure pathways. The hazard index (HI) mean value (1.82E+00) of Ni for all exposure pathways was greater than 1, while total risk value of Cr (1.00E-03) had exceeded USEPA limit, indicating cancer risk. Consequently, the study of UCPs soils revealed PTEs contamination that could pose a potential health risk to the local population in the studied UCPs regions of Pakistan. Thus, the present study recommends that the influx of PTEs originating from natural and anthropogenic sources should be mitigated and government should implement strict enforcement of environmental regulations and proper management, as well as air quality monitoring guidelines for public health should be strictly adopted to reduce traffic- and industrial emission-related to PTEs in metropolitan areas.

Dynamics of Major and Trace Elements in Water-Soil-Tree Interaction: Translocation in Pyrus malus in Chihuahua, Mexico Using ICP-OES and Its Health Risk Implications

The transference of metals from water irrigation and soil to plants is a possible pathway of contamination for the trophic chain. This research is focused on the distribution of 16 analytes in the water-soil-tree (Pyrus malus) interaction in an agricultural region in the state of Chihuahua in Mexico from August 2019 (first sampling) to August 2020 (second sampling). The apple variety under investigation was Golden Delicious; it was found that the trace elements of As (0.18-0.34 mg·kg^-1) and Cd (0.11-0.14 mg·kg^-1) in the apple were above the corresponding permissible limit, according to FAO/WHO, and Cr (0.08-0.86 mg·kg^-1) was below the limit. Furthermore, the health risk implications were estimated by the Hazard Quotients (HQ) and carcinogenic risk (CR). For carcinogenic risk, As, Cd, and Cr exceeded the risk limit (CR > 10^-4). This investigation as well provides a link for similar research around the globe. Major and trace elements detection was performed with the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) technique, along with a prior homogenization of samples and microwave acid digestion. To obtain the statistical behavior, an analysis of variance and correlation was performed.

Agriculture management and seasonal impact on soil properties, water, sediment and chemicals transport in a hazelnut orchard (Croatia)

Soil and water conservation practices are key to agroecosystems sustainability and avoiding diffuse pollution. Here, we compare the impacts of different types of mulch, barley straw (Straw), wooden chips (Chip) and tillage (Till) on vegetation mulch cover (VMC); soil properties, bulk density (BD), mean weight diameter (MWD), water stable aggregates (WSA), soil water content (SWC), soil organic matter (SOM), pH and total phosphorous (P), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), Zinc (Zn) and lead (Pb). We also assessed the ponding time (PT), runoff time (RT), runoff, sediment concentration (SC), sediment loss (SL) and chemicals transport (the same studied in soil). A set of rainfall simulation experiments (90 in total) was applied in the different Spring, Summer, and Fall treatments. The results showed that mulch increased VMC in all the seasons, while other properties (BD; MWD, WSA SOM, pH) were not affected, especially in Spring. The biggest impact was observed in Fall, especially in the Till plot, due to the tillage practices applied in Summer. Mulch increased PT, RT and reduced runoff, SL and chemicals transport. Chemical losses were very much associated with SL, and the concentration of P and metals in soil depended on soil Ca and pH. SWC, MWD and runoff were inversely related to PT, RT and SC. Finally, BD, VMC and SOM were highly associated. Overall, tillage practices dramatically impact SL, and diffuse pollution and urgent measures are needed to reverse this. Mulching is excellent and cost-effective to mitigate the impacts of agriculture on land degradation and diffuse pollution.

Distribution and temporal variability of uranium and toxic metal(loid)s in snow and rainwater from an oil industry and urban area in Thessaloniki-Greece

The concentrations of uranium and nine elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in snow and rainwater samples were determined. Samples were collected in Thessaloniki-northern Greece in three sites, one in the industrial area close to an oil production power plant and two in the centre of the city. Snow samples were collected during January-February 2019 and 2021 whereas in the case of rainwater, a two-year survey has been performed during 2019 and 2020. The activity concentrations of the uranium radioisotopes were measured by alpha spectrometry whereas the metal(loid)s concentrations were determined by inductively coupled plasma mass spectroscopy (ICP-MS). The elevated concentrations of uranium (U) and the deviation of the isotopic ratio of U-234/U-238 from the equilibrium value indicated intensive dissolution of uranium. The results were analyzed using statistical analysis (Shapiro-Wilk, Friedman and Kruskal-Wallis tests). The obtained data and the calculated enrichment factors (Efs) denote variation of the concentration values between industrial and urban area and different elemental distribution influenced from anthropogenic contributions, meteorological conditions and the COVID-19 pandemic.

Arsenic and trace metal concentrations in different vegetable types and assessment of health risks from their consumption

The levels of 12 trace metal (loid)s (TMs) in 10 vegetable types including leafy vegetables (purslane, purple basil and parsley) and fruiting vegetables (pepper, tomato, eggplant, cucumber, zucchini, green bean and melon) and in maize grown in Malatya province (Turkey) were investigated and non-carcinogenic health risks from consumption of these crops were assessed. The levels of TMs were measured by inductively coupled plasma-optical emission spectrometry. The mean levels of Ni, Cu, Cd, Cr, As and Zn in all crops were below maximum permissible concentrations (MPCs), while those of Pb in pepper (0.109 mg/kg fw), eggplant (0.103 mg/kg fw) and green bean (0.177 mg/kg fw) slightly exceeded MPCs (0.1 mg/kg fw). Leafy vegetables had relatively higher concentrations of Al, As, Ba, Cr, Cu, Fe and Mn compared to fruiting vegetables and maize. The estimated daily intake value of each TM estimated for each crop was found to be below the tolerable daily intake value. The target hazard quotients of all TMs in all crops did not exceed the acceptable non-carcinogenic risk level. However, hazard index (HI) value (1.57) in tomato was found to be above the threshold value of 1, indicating non-carcinogenic risks for consumers due to the intake of combined TMs in tomato. The THQ values of As, Co and Pb contributed 46.4%, 24.5% and 16.4% of the HI value of tomato, respectively. High daily consumption amount of tomato likely resulted in high HI value. The findings obtained in this study reveal that even if the levels of TMs in vegetables are safe, more attention should be paid to non-carcinogenic risks associated with TMs as a result of high vegetable intake.

Uptake, organ distribution and health risk assessment of potentially toxic elements in crops in abandoned indigenous smelting region

Inorganic pollution induced by smelting waste has threatened the safety of environment, whereas the impacts on farmlands with regards to potentially toxic elements (PTEs) receive insufficient attention. Herein, the contents, transfer pathways and potential risks of the PTEs in common crops were examined from different farmlands distributed around an indigenous Zn-smelting area in Guizhou, China. The results showed that Tl in cabbage (Brassica oleracea L.) (up to 3.74 mg/kg) and radish (Raphanus sativus L.) (up to 1.16 mg/kg) at some sites exceeded the maximum permissible level (MPL) (0.5 mg/kg) for food, and, under the same pollution condition, cabbage and radish were more likely to enrich PTEs, and the edible portion of maize was not prone to Tl risk. Hazard quotient calculations of Tl, Ba, and U were greater than 1, indicating the edible risk of crops for these PTEs. Further characterization of selected soils revealed that MnFe₂O₄ and Fe₂O₃ controlled the phase transformation of Tl(III) in rhizospheric soils. Furthermore, distinctive mullite was detected in the soil which confirmed the contribution of high temperature smelting to PTEs pollution. The findings indicate an emergent need for soil remediation around historical indigenous metal smelting areas for the sake of food security.

Combing phosphorus-modified hydrochar and zeolite prepared from coal gangue for highly effective immobilization of heavy metals in coal-mining contaminated soil

Considering the adverse effects of heavy metals (HMs) on agriculture soil, in-situ immobilization has been paid great attention worldwide. P-modified biochar/hydrochar along with synthetic zeolite for efficient HMs immobilization in contaminated soil becomes a promising choice. In this study, H₃PO₄-modified hydrochar (BPH) derived from banana peels, and Na-X zeolite (ZL) prepared from coal gangue was applied individually and synergistically (1%BPH, 2%BPH 1%ZL, 2%ZL, and 1%BPH+1%ZL) to remediate a farmland soil polluted by Cd, Cu, and Pb near the coal-mining area. Compared with the mono-application of these two amendments, their combination significantly improved the soil organic carbon (SOC), electric conductivity (EC), and dehydrogenase activity. Besides, the addition of 1%CLH+1%ZL remarkably reduced the Cd, Cu, and Pb bioavailability by 67.01%, 57.01%, and 78.72%, respectively, in the soil after 100 d incubation by transforming these metals to more stable forms. The order of the HMs immobilization capacity for these two amendments was as follows: Pb > Cu > Cd. Moreover, the dominated immobilization mechanism of their synergistic application was that BPH could immobilize HMs by precipitation, complexation, and π-π electron-donor-acceptor interaction. The precipitation and complexation blocked the surface pores of BPH. The sustained release of phosphorus groups and radicals was prevented. This obstacle was possibly alleviated by adding ZL. Besides, the formation of cationic bridging, the enhancement of soil properties, and the physical adsorption of these amendments were also conducive to HMs immobilization in soil. This work indicated that co-application of BPH and ZL possibly was an excellent choice for immobilizing HMs in soil.

A synthetic health risk assessment based on geochemical equilibrium simulation and grid spatial interpolation for zinc (II) species

Soil heavy metal pollution has become a global issue involving environmental safety and human health risks. This paper quantified the sources of heavy metals by positive matrix factorization (PMF) model and explored the spatial distribution of heavy metals by means of grid scales, with an industrial site as the study area in Suzhou. The PMF identified four pollution sources of heavy metal in soil, and the quantitative results revealed that industrial activities (33.5%) contributed the most to heavy metals, followed by soil parent materials (30.8%) and agricultural activities (19.7%). Zinc (Zn) was screened out as the targeted metal (TM) through the potential ecological risk assessment, the metal species of which was simulated by the geochemical software PHREEQC. This research aimed to determine the dominant metal species of TM with high-risk levels to realize the transformation of toxic metal species. Herein, according to the morphological evolution of metal species, the activity and concentration of the Zn ion species were obtained for both carcinogenic and non-carcinogenic risk assessment. The evaluation of the optimized human health risk demonstrated that the associated health risk of Zn (II) ions depended predominantly on its metal speciation. Overall, the optimized carcinogenic and non-carcinogenic risk value of Zn₂S₃^2- for adults was 2.01E-04 and for children was 1.31, resulting in corresponding hazardous risk to humans, which accounted for high-risk levels of 61.5% and 58.5% for adults and children, respectively. The OHRA method can provide a reference for the decision-making of soil heavy metal pollution and remediation for specific heavy metals in polluted areas.

Metal accumulation and health risk assessment in wastewater used for irrigation around the Agra Canal in Faridabad, India

Wastewater application for irrigation is a traditional and economic tool in developing nations. Yet prolonged use of wastewater for agricultural activities contributes to the accumulation of metals in both soil and vegetables. This study investigated the accumulation and contamination of vegetables with heavy metals ensuing from the application of wastewater from the Agra Canal and the associated risks posed to human health. Three sites across the Agra canal were selected for sampling (CW-1, CW-2, and CW-3), where untreated wastewater is being used to irrigate vegetables (spinach, coriander, radish, and garlic crops), for which tube-well water (TW) from a village served as the control site. Water, soil, and vegetable samples were collected from all sites. The presence in them of various metals, such as As, Pb, Cr, Mn, Cu, Zn, and Ni, was detected at all four sites. The greatest content of Mn was found in CW-1's water (7.91 mg/L), soil (633.77 mg/kg), and in spinach 368.12 (mg/kg) grown there. Significantly higher metal concentrations were observed in vegetables irrigated with wastewater than in tube-well-irrigated vegetables, with the metals ranked in accumulation as follows Mn > Zn > Ni > Cu > Cr > Pb > As. Our results also revealed that metal bioaccumulation varied enormously between foliar and non-foliar vegetables, as well as among the four sites. Daily metal intake (DMI) and health risk index (HRI) analyses suggested that children consuming contaminated vegetables are at higher risk than adults. The HRI for Mn, Ni, and Pb was above 1, which indicated significant health hazards to humans consuming the wastewater-irrigated vegetables. Moreover, the control site where tube-well water was used had an HRI below 1, signifying a negligible health risk for its consumption. Therefore, we may conclude that the extensive application of contaminated water for a longer duration would likely further increase metal accumulation in soil and vegetables that may be hazardous to living organisms.

Essentiality of Trace Elements in Pregnancy, Fertility, and Gynecologic Cancers-A State-of-the-Art Review

Gynecological neoplasms pose a serious threat to women's health. It is estimated that in 2020, there were nearly 1.3 million new cases worldwide, from which almost 50% ended in death. The most commonly diagnosed are cervical and endometrial cancers; when it comes to infertility, it affects ~48.5 million couples worldwide and the number is continually rising. Ageing of the population, environmental factors such as dietary habits, environmental pollutants and increasing prevalence of risk factors may affect the reproductive potential in women. Therefore, in order to identify potential risk factors for these issues, attention has been drawn to trace elements. Trace mineral imbalances can be caused by a variety of causes, starting with hereditary diseases, finishing with an incorrect diet or exposure to polluted air or water. In this review, we aimed to summarize the current knowledge regarding trace elements imbalances in the case of gynecologic cancers as well as female fertility and during pregnancy.

Hydrothermally synthesized titanate nanomaterials for the removal of heavy metals and radionuclides from water: A review

Hazardous heavy metals and radionuclides in water and wastewater are of drastic concern owing to their detrimental impacts on the organisms as well as the circumambient ecosystem. To remove them as much as we can, both technique and materials were studied in the past years. The adsorption technique as superior water remediation method with the simplicity of design, environmental friendliness and high efficiency was well established. Consequently, it is practically important to explore advanced and economically feasible absorbents for removing these poisonous pollutants from aqueous solutions. So far, large numbers of experiments proved hydrothermally synthesized titanate nanomaterials (TNMs) could be a prospectively excellent adsorbent extracting heavy metals and radionuclides from water due to the high specific surface area, tunable pore size, abundant surface active sites, favorable hydrophilic properties. The objective of this work is to give an overview of hydrothermal synthesis, adsorption performance of TNMs for heavy metals and radionuclides, as well as the various influencing factors for water purification. It comprehensively reviews the structural changes and regenerability of TNMs after adsorption, and different modification methods adopted for improving removal capacity. Additionally, it uniquely highlights the efficient decontamination of the pollutants through a synergistic effect of adsorption and photocatalysis by TNMs. This review provides detailed information for the development, application, and research challenges faced by hydrothermally synthesized TNMs for the removal of heavy metals and radionuclides from aqueous solutions, which will serve as a reference guide for scientists in related fields.

Exploring human health risk assessment based on the screening of primary targeted metal and chemical balance simulation of ionic speciation in an industrial area, China

A comprehensive human health risk assessment methodology based on major hazard element screening and morphological evolution simulation is proposed. The primary targeted metal (PTM) screened by classical health risk assessment was introduced into chemical balance simulation to obtain speciation distribution and corresponding risk. According to the results of risk assessment of morphological evolution of primary targeted metal (PTM), a potential methodology for the remediation is proposed, which could reduce the risk level efficiently and quickly by changing the pH of soil environment with additional acid and alkali substances. A case study was performed in a dye factory in Suzhou city, Jiangsu Province, China. The results of classical health risk assessment showed that the regional health risk index for children exceeded tolerance value of 1, in which Cr accounted for high risk level of 61%. Chemical balance simulation results showed that CrO₄^2- and CaCrO₄ had the highest risk index, and the change of pH value would affect the proportion of CrO₄^2- and CaCrO₄ in Cr⁶⁺ ionic speciation, which may indirectly change the risk level. It is recommended to adjust the pH of the soil environment to quickly reduce regional human health risk. This study will provide a theoretical basis for public health protection and site restoration management.

Environmental and human health risk assessment of potentially toxic elements in soils around the largest coal-fired power station in Southern Russia

The combustion of solid fuel at power plants pollutes adjacent areas with potentially toxic elements (PTEs), which increases risks to public health in the vicinity of these facilities. The proposed paper presents the results of a geochemical study of PTEs (Cr, Mn, Ni, Cu, Zn, Cd, and Pb) contamination in the vicinity of Novocherkassk Power Plant (NPP) as it relates to environmental and human health risks. The impact zone of NPP is pronounced for a distance of approximately 7 km northwest of the enterprise-the second largest coal power plant in Southern Russia. Data from monitoring sites lead us to conclude that spatial patterns of soil pollution are strongly influenced by the peculiarities of local atmospheric circulation, while the characteristics of soils within the study area play a secondary role. The highest levels of PTEs and their exchangeable forms exceed both regional background and sanitary and hygienic standards within a radius of 3 km to the west of the plant, which corresponds to a zone of soils contaminated with Cr, Ni, Cu, Zn, Cd, and Pb. The carcinogenic risk to human health slightly exceeds the permissible standard of 1 × 10^-6 for soils in close vicinity of the enterprise due to the potential human intake of Ni, Cd, and Pb. The results of the health risk assessment indicate no noncarcinogenic risks for adults, while for children, they are low.

Human Exposure to Potentially Toxic Elements from the Consumption of Soybean Beverages Commercialized in Spain

ABSTRACT

Plant-based beverages have been positioned as an alternative to cow's milk. Some of the most commonly consumed plant-based beverages are those made from soybeans. Soybean beverages can be an important source of essential elements. However, soybean plants can be exposed to high concentrations of contaminants, such as toxic metals, from the soil and the environment. The objective of this study was to determine the concentrations of potentially toxic elements (PTEs; Fe, Cu, Cr, Co, Mn, Mo, Zn, B, Ba, Ni, Li, Sr, V, Al, Cd, and Pb) to evaluate the human exposure and toxic risk from the consumption of these soybean beverages. Forty samples of various brands of soybean beverages were analyzed by inductively coupled plasma-optical emission spectroscopy. The most abundant PTE was Al (3.93 mg/L), followed by Fe (1.91 mg/L) and Ba (0.69 mg/L). Based on a mean consumption of two servings of soybean beverage per day (250 mL per serving), this consumption results in a daily intake of Al and Pb that is significant but still below of the maximum recommended amount. However, higher consumption could exceed the maximum recommended Al and Pb values, with consequent risks to the human health.

HIGHLIGHTS

Microanalysis and signature of rare earth elements in geochemical samples using neutron activation analysis

Nuclear techniques are applied for exploration and efficient tapping of natural resources in finding promising resources of mining and mineral processing industries. The rare earth elements (REEs) in four fluorite samples, collected from Nuba Mountains are determined using neutron activation analysis (NAA) technique. The concentration of 11 REEs (Sc, La, Ce, Nd, Sm, Eu, Gd, Dy, Tb, Yb, Lu) was measured and found within ranges between 685 and 1747 ppm. The Ca is a major element in the four samples. The Fe, Al, Na, Ba and Sr are found as minor elements in the investigated samples. In addition, tracer levels of U, Th, Cs, V and Sc are also detected. The signature of Ce, La and Nd as light REEs is characterized in all samples under this study. The enrichment types of light-REEs (L-type), medium-REEs (M-type) and several distinct features of some REEs e.g., Ce and Eu anomalies are identified and described as the signature of REEs in the geochemical samples. These results have demonstrated promising materials that could be used for hydrometallurgy processing to get significant amounts of REEs.

Effect of different industrial activities on soil heavy metal pollution, ecological risk, and health risk

Soil heavy metal (Cr, Cu, Zn, Pb, Cd, V, As) concentrations in different areas were analyzed to investigate the effects of different industrial activities on heavy metal pollution status, potential ecological risk, and human health risk in Panzhihua. Our results showed that Cu and V enrichment in soil was due to ore smelting. Soil Cr accumulation was related to coal ore mining. Soil Cd, Zn, As, and Pb enrichment was attributed to high-temperature coal combustion. Under the effect of industrial activities, soils were moderately contaminated with Cd, uncontaminated to moderately contaminated with As and Zn, and uncontaminated with Cr, Cu, V, and Pb. Soil heavy metal potential ecological risk was considerable, and non-carcinogenic risks and carcinogenic risks of soil heavy metals were acceptable for adults but unacceptable for children. Thermal power generation was the dominated industrial activity that influence the soil heavy metal concentrations and environmental risks in Panzhihua, which posed considerable potential ecological risks and unacceptable heavy metal non-carcinogenic risks and As carcinogenic risk to both adults and children. This study indicates that industrial activities have great effects on heavy metal pollution, ecological risks, and health risk, and more attention should be paid to the ecological risk and health risks brought by thermal power generation.

Emerging risks of toxic metal(loid)s in soil-vegetables influenced by steel-making activities and isotopic source apportionment

Industrial activities tend to deteriorate adjacent agricultural lands due to accumulation of potentially toxic elements in soils and crops. However, better understanding of their distinctive source partitions and transfer process remains insufficient in steel-making area. The paper focuses on the pollution levels, health risks, and provenance identification of Tl, As, Pb, Cu, Ni, Co, Sb, Cd, Zn, Be, Cr, Fe, Mn, Mo, Sn, and V in common vegetables from different farmlands near a steel-making plant. The results showed that the Tl, As, Pb, Cd, Cr, Cu and Mn were of high-level contamination in soils and generally above the maximum permissible level (MPL). Calculation using hazard quotients (HQ) exhibited that consumption of the studied vegetables may entail significant health risks to residents, especially for children, resulting from the elevated contents of Tl, As and associated toxic elements. Calculation by binary mixing model using Pb isotopic compositions suggested that steel-making activities contributed to 35-80% of the contamination of Pb and As in vegetables. It is necessary to adopt appropriate remediation measures to mitigate the farmland contamination and ensure the food safety of the agricultural products.

Health risks of metal(loid)s in maize (Zea mays L.) in an artisanal zinc smelting zone and source fingerprinting by lead isotope

Metal(loid) contamination caused by industrial activities in agricultural soils has become a universal environmental and food safety concern. This study revealed the contamination, pathway, and source contribution of metal(loid)s such as lead (Pb), zinc (Zn) and cadmium (Cd) in maize and soils in different residential areas impacted by long-term historical artisanal zinc smelting activities from Southwest China. Results revealed that the soils were contaminated heavily by metals like Pb, Zn and Cd, with contents of 40-14,280, 150-47,020 and 1.28-61.7 mg/kg, respectively. Hazard quotients of food uptake for Pb, Cd and Cr in maize grains were extremely high for residents, in particular for the children. To trace the sources of metal health risk, lead isotope fingerprinting and binary mixing modeling were applied. It indicated that the anthropogenic activities contributed over 80% to the Pb contamination in maize grains. The findings highlighted warning levels of health risks to the residents in consuming maize grains in the historical artisanal PbZn smelting area. Therefore, an effective strategy including pollution source control and remediation measures must be taken to improve the soil quality and guarantee food safety around the historical smelting areas likewise.

Investigation on the Coupling Coordination Relationship between Electric Power Green Development and Ecological Civilization Construction in China: A Case Study of Beijing

In the context of ecological civilization construction (ECC) and energy revolution strategy, there are many studies on ECC or electric power green development (EPGD). However, EPGD and ECC influence each other and are closely related, and there are few studies on the development relationship of EPGD and ECC. Therefore, this paper aims to study the coupling coordination relationship between EPGD and ECC to make them develop in harmony. Firstly, an evaluation index system of EPGD and ECC for their coupling coordination relationship is proposed. Then, this paper combines the coupling coordination degree model (CCDM), improved analytic hierarchy process (AHP) based on cloud model, and regression model to propose a coupling coordination relationship analysis model for EPGD and ECC. The improved AHP based on cloud model can fully reflect the will of decision-makers and effectively deal with the ambiguity and randomness of weight judgment. Finally, this paper conducts an empirical study on Beijing and verifies the applicability of the model proposed in this study. Policy recommendations to promote EPGD and ECC are proposed based on weight analysis, coupling coordination degree (CCD) analysis and regression analysis. This paper provides tools for the study on policies related to power development and ecological civilization.

Risk assessment of potentially toxic elements in soils and vegetables around coal-fired thermal power plant: a case study of Dhanbad, India

The present study was intended to determine the potentially toxic elements (PTEs) concentration in fly ash (FA), soil, plant, and vegetable to assess the impacts of pollution on the nearby areas of coal-fired thermal power plant (TPP). The PTEs concentrations (mg/kg) in FA were Cr (48-74) > Pb (41-65) > Cd (7.4-9.7) > As (3.19-4.43) > Hg (0.518-0.598). The contamination factor (C_f) for Cd was highest in agricultural soil (C_f = 22) followed by roadside soil (C_f = 20), and forest soil (C_f = 15), which showed that the soil was strongly polluted due to the presence of Cd. The ecological risk index (ERI) in the topsoil of roadside area was also very high (1130), due to the high value of ecological risk factor of Cd (898) and Hg (213). The health risk associated with the intake of soil containing PTEs were also estimated by calculating hazard index (HI), and the values showed that the risk posed to children was minimum (HI < 1). But in case of roadside area, the HI was very close to one (0.975) indicating that the prolong exposure may pose severe health risk. The bioaccumulation coefficient of all PTEs for Albizia lebbeck and Madhuca longifolia were < 1, indicating less PTEs accumulation in the plant species. The hazard quotient of all PTEs (except of Hg) through vegetable consumption (Allium cepa and Raphanus sativus) was > 1, which signifies that the long-time consumption of contaminated vegetables may cause severe risk to the people.

The Effect of a Fly Ash-Based Soil Conditioner on Corn and Wheat Yield and Risk Analysis of Heavy Metal Contamination

The utilization of coal fly ash (CFA) as a soil conditioner has been a research hotspot in recent years. In this paper, the continuity and stability of the yield-increasing effect of a fly ash-based soil conditioner were investigated through field trials for three consecutive years. The yield-increasing effect and applicability were also investigated by planting a variety of crops in different types of soil. Field test results revealed that the new fly ash-based soil conditioner had wide adaptability and stability under the condition of reducing the application of traditional fertilizers by 20%. For corns grown in castano-cinnamon soil and dark brown soil, the application of the new fly ash-based soil conditioner for three consecutive years has steadily increased the yield by more than 10%. The yield of wheat planted in castano-cinnamon soil also increased by 15%. Additionally, considering that heavy metals (HMs) contained in the fly ash-based soil conditioner may cause environmental contamination, this paper calculated and analyzed the bio-concentration factor (BCF) and the translocation factor (TF) of Cr, As, Cd, Hg and Pb in the corn experimental fields. The results showed that the five heavy metals were not significantly enriched in various parts of the corn stalk after application of the soil conditioner, and there was temporarily no environmental risk in terms of returning straws to the field or raising livestock.

Assessment of soil and maize contamination by TE near a coal gangue-fired thermal power plant

Coal preparation by-products, such as coal gangue, are inferior fuels enriched with trace elements (TEs). Owing to the issues surrounding the disposal of coal preparation by-products and energy shortages, Chinese researchers have strongly advocated harvesting energy from by-products. However, the secondary environmental pollution caused by such by-products has been overlooked. In this study, we aimed to assess the contamination of soil and maize (Zea mays L.) near a coal gangue-fired power plant (CGPP) in Liupanshui City, Guizhou Province, China, by TEs. The contents of 11 TEs (Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, V, and Zn) in soil samples and different maize tissues were measured, and their chemical speciation in soil was also determined. The results showed that the soil in the study area was polluted by the above elements to varying degrees at a very high potential ecological risk. The Cr and Pb levels in niblets of partial samples exceeded the Chinese food safety standards. The TE contents of maize tissues largely depend on the bioavailable fraction of the same elements in the soils, rather than their total contents. Pearson's correlation and hierarchical cluster analyses resulted in three clusters:(1) Pb-Zn-Cd; (2) Co-Cu-Mn-Sb-V-Be; and (3) Cr-Ni. Coal preparation by-products should not be directly combusted without pre-treatment. These results will aid readers and engineers in understanding the adverse effect of CGPPs and provide regulators and policymakers with relevant data to scientifically guide the utilisation of coal preparation by-products.

Combining geospatial analyses to optimize quality reference values of rare earth elements in soils

High pedological and geological variability can trigger the formation of REE hotspots, causing a need to optimize the establishment of quality reference values (QRVs). Thus, we determined the background concentrations of REEs in the soils of an emerging Brazilian state and used a combination of Moran's I and indicator kriging to identify REE hotspots and determine QRVs. A total of 100 composite soil samples was collected at a 0.20 m depth to establish background concentrations, QRVs, and spatial distribution and to elaborate probability maps for REEs. The QRVs established for soils were the following (mg kg^-1): La (27.21), Ce (57.26), Pr (10.49), Nd (24.29), Sm (4.75), Eu (0.90), Gd (4.22), Tb (0.82), Dy (1.54), Ho (0.38), Er (1.23), Yb (1.07), Lu (0.24), Y (10.65), and Sc (3.70). It was possible to draw attention to the Northwest and Southwest regions of the Rio Grande do Norte (RN) state, due to the formation of REE hotspots, indicated by Moran's I, and a high tendency to exceed the QRVs, confirmed by the indicator kriging. The high background concentrations and geochemical patterns for REEs showed that a single QRV for each REE and the entire state can neglect specific environmental characteristics and misrepresent the natural geochemistry of the soil. Thus, specific QRVs were established to optimize the monitoring of natural REE values by identifying hotspot areas. The criteria established here may be useful for other groups of potentially toxic elements, provided that observations meet the requirements of the spatial autocorrelation and kriging analyses. Graphical abstract.

Distribution and health risk assessment of potentially toxic elements in soils around coal industrial areas: A global meta-analysis

Coal production and utilization are recognized as two principal sources of potentially toxic elements in the environment. Here the published literature (2008-2018) was searched to collect data on As, Ni, Cd, Cu, Cr, Hg, Pb and Zn concentrations in soils near different types of coal industrial areas such as coal mines, thermal power plants, coal chemical plants, coal mining cities and coal waster piles. The contamination levels of soils and associated health risks were assessed using global reference materials and multiple contamination indices. The results revealed that average concentrations of potentially toxic elements varied widely, yet most of them exceeded global averages in background soils and upper continental crust concentrations. Spatial distribution analysis suggested the concentrations of potentially toxic elements varied according to coalification and combustion conditions. Higher concentrations were found in Southeast Asia, South Europe, and North Africa compared with other regions. Assessment of the geoaccumulation index revealed that contamination levels of Cd and Hg were higher than those of other elements. In particular, Ni, Cd, Zn, and Hg were most likely to accumulate in soils near coal mining areas, while Cd and Hg tended to accumulate near coal chemical plants. Regarding non-carcinogenic risks, oral ingestion was the major pathway of exposure to potentially toxic elements in coal industry-associated soils, followed by dermal contact and inhalation. Tolerable non-carcinogenic risk of potentially toxic elements and relatively high carcinogenic risks of As were observed. Children were most vulnerable to non-carcinogenic risks, while the carcinogenic risks estimated for adult and children populations were similar. Accordingly, As should be designated as top candidates for priority control to protect human health in the vicinity of coal industry-associated areas. This study provides timely information for developing control and management strategies to reduce soil contamination by potentially toxic elements in different types of coal industrial areas.

Hyperaccumulation and transport mechanism of thallium and arsenic in brake ferns (Pteris vittata L.): A case study from mining area

Both thallium (Tl) and arsenic (As) bear severe toxicity. Brake fern (Pteris vittata L.) is well-known for its hyperaccumulation capacity of As, yet its role on Tl accumulation remains unknown. Herein, brake ferns growing near an As tailing site in Yunnan, Southwestern China are for the first time discovered as a co-hyperaccumulator of both Tl and As. The results showed that the brake ferns extracted both As and Tl efficiently from the soils into the fronds. The studied ferns growing on Tl and As co-polluted soils were found to accumulate extremely high levels of both As (7215-11110 mg/kg) and Tl (6.47-111 mg/kg). Conspicuously high bio-accumulation factor (BCF) was observed for As (7.8) and even higher for Tl (28.4) among these co-hyperaccumulators, wherein the contents of As and Tl in contaminated soils were 1240 ± 12 and 3.91 ± 0.01 mg/kg, respectively. The applied advanced characterization techniques (e.g. transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS)) indicated a preferential uptake of Tl(I) while simultaneous accumulation of As (III) and As(V) from the Tl(I)/Tl(III)-As (III)/As(V) co-existent rhizospheric soils. The findings benefit the phytoremediation practice and pose implications for managing and restoring Tl-As co-contaminated soils in other countries.

Effects of location, climate, soil conditions and plant species on levels of potentially toxic elements in Chinese Prickly Ash pericarps from the main cultivation regions in China

The presence of potentially toxic mineral elements is often reported in soil, fruits and vegetables. The concentrations of these are influenced by location, climate and soil conditions, and plant species. This study reports levels of aluminium (Al), arsenic (As), cadmium (Cd), lead (Pb), manganese (Mn) and nickel (Ni) in the soils where Chinese Prickly Ash - Zanthoxylum bungeanum (ZB) and Z. armatum (ZA) are grown. Soil and pericarp samples were taken from 72 ZB and ZA plantations in 12 provinces. The soil pollution index (PI) was generally low for As (0.04-0.35), Pb (0.01-0.74) and Ni (0.15-1.06). The PI was higher for Cd (0.06-6.99) and was assessed at three categorical levels: 'low' (in 26% of soils), 'moderate' (in 67% of soils) and high (in 7% of soils). The majority (94%) of soils were slightly polluted with Cd with the integrated pollution index in the range 0.17-2.02. More than 60% of pericarp samples posed a high non-cancer health risk based on the hazard index, while 43% of pericarp samples posed a considerable cancer risk based on the incremental lifetime cancer risk. The mean temperature and the mean relative humidity contributed most significantly (28% and 10%, respectively) to variation in the concentrations of potentially toxic elements in the pericarps. This study provides a comprehensive report on the concentrations of potentially toxic elements in the soils and associated pericarps, and the effects of location, climate, and soil on the levels of potentially toxic elements in the soil and pericarps, including the effects of tree species.

Health risk assessment and bioaccessibilities of heavy metals for children in soil and dust from urban parks and schools of Jiaozuo, China

Urban parks and schools sever as the mainly activity areas for children, but risk assessment posed by heavy metals (HMs) from soil and dust in these area has rarely been investigated. In this study, six urban parks and seven schools in Jiaozuo, China, were taken as research objects to understand the contamination level and bioaccessibility of HMs from soil and dust in urban parks and schools. The results indicated that Zn, Cu, Pb, Cd, As, Ni and Co from soil and dust were above the background values, especially Zn and Cd in dust, and As and Cd in soil. Serious Cd pollution was discovered, and respective Cd concentrations in soil and dust were 17.83 and 7.52 times the background value. Additionally, the average concentration and bioaccessibility of Zn, Mn, Pb, Cd, Cr, Ni and Co in dust were both higher than in soil. High concentration and high bioaccessibility of HMs in dust suggested that HMs contamination were serious and universal in Jiaozuo. The concentrations of most HMs were higher in the gastric phase, except for Cu and Cd which remained higher in the intestinal phase. Both in the gastric phase and intestinal phase, Mn, As and Cd in soil and dust both have high bioaccessibility which all exceed 10%. The carcinogenic and non-carcinogenic risks base on the total HMs for children (soil: 7.93, 1.96E-05; dust: 6.44, 3.58E-05) were greater than those for adults (soil: 6.35E-01, 1.32E-05; dust: 5.06E-01, 2.42E-05), and urban parks and schools posed high potential risk for children. Therefore, assessment the risk posed by HMs contamination of soil and dust in urban parks and schools is vital and urgent for children.

Thallium contamination, health risk assessment and source apportionment in common vegetables

As an element with well-known toxicity, excessive thallium (Tl) in farmland soils, may threaten food security and induce extreme risks to human health. Identification of key contamination sources is prerequisite for remediation technologies. This study aims to examine the contamination level, health risks and source apportionment of Tl in common vegetables from typical farmlands distributed over a densely populated residential area in a pyrite mine city, which has been exploiting Tl-bearing pyrite minerals over 50 years. Results showed excessive Tl levels were exhibited in most of the vegetables (0.16-20.33 mg/kg) and alarming health risks may induce from the vegetables via the food chain. Source apportionment of Tl contamination in vegetables was then evaluated by using Pb isotope fingerprinting technique. Both vegetables and soils were characterized with overall low ²⁰⁶Pb/²⁰⁷Pb. This indicated that a significant contribution may be ascribed to the anthropogenic activities involving pyrite deposit exploitation, whose raw material and salgs were featured with lower ²⁰⁶Pb/²⁰⁷Pb. Further calculation by binary mixing model suggested that pyrite mining and smelting activities contributed 54-88% to the thallium contamination in vegetables. The results highlighted that Pb isotope tracing is a suitable technique for source apportionment of Tl contamination in vegetables and prime contamination from pyrite mining/smelting activities urges authorities to initiate proper practices of remediation.

Remediation of hexavalent chromium contaminated water through zero-valent iron nanoparticles and effects on tomato plant growth performance

Contaminated water with hexavalent chromium Cr(VI) is a serious environmental problem. This study aimed to evaluate the Cr(VI) removal by zero valent iron nanoparticles (nZVI) reduction process and the impact of Cr(VI), nZVI and combined treatment with nZVI and Cr(VI) on tomato growth performance. To evaluate the Cr(VI) toxic effect on germination capability, seeds were exposed to increasing Cr(VI) concentrations up to 1000 mg L⁻¹. The inhibition of seed germination and the decrease of hypocotyl and root length started from Cr(VI) 5 mg L⁻¹. Under treatment with Cr(VI) + nZVI 5 mg L⁻¹, seed germination, hypocotyl and root length resulted significantly higher compared to Cr(VI) 5 mg L⁻¹ treatment. The impact of only nZVI was investigated on chlorophyll and carotenoid in leaves; iron levels in leaves, roots, fruits and soil; carotenoid, fat-soluble vitamin and nicotianamine in mature fruits. A significant increase of leaf chlorophyll and carotenoids was observed after nZVI 5 mg L⁻¹ treatment compared to controls. No significant variations were observed in carotenoids, fat-soluble vitamins and nicotianamine levels after treatment with nZVI 5 mg L⁻¹ in mature fruits. For their ability to reduce Cr(VI) and to stimulate tomato growth, nZVI might to be considered as alternative for remediation purposes.

Synergistic effects of biochar and processed fly ash on bioavailability, transformation and accumulation of heavy metals by maize (Zea mays L.) in coal-mining contaminated soil

In the paper, hydrothermally (HT) treated, sulfuric acid (H₂SO₄), and hydrochloric acid (HCl) washed fly ashes (FA) were used to examine the applied effects with and without biochar (BC) on the bioavailability of heavy metals (HMs) and growth of maize (Zea mays L.) plants in coal-mining contaminated soil. Addition of BC in combination with these processed fly ashes (PFA) significantly increased the soil pH, EC, and soil organic carbon (SOC). Individual application of BC and PFA increased the available contents of Mg, Mn, and Fe, while the combination of BC and PFA significantly decreased the bioavailability of HMs in soil compared to control. The BC + HT-FA and BC + H₂SO₄-FA were most efficient treatments followed by BC + HCl-FA in promoting plant growth parameters (i.e., fresh and dry biomass, root and shoot lengths), reduction in the uptake of HMs and increase in the uptake of macronutrients. The results established that the combined application of BC and PFA synergistically increased HMs immobilization and maize biomass yields. The lowest transfer rate (TR), bioconcentration factor (BCF), and translocation factor (TF) for Cr, Co, Ni, Cu, Zn, Cd, and Pb were detected in BC + HT-FA, followed by BC + H₂SO₄-FA and BC + HCl-FA treatments after 60 days of maize crop harvesting. It could be suggested that using BC along with PFA as a soil stabilizer may be a promising source to immobilize HMs in a coal-mining contaminated soil.

The effects of climate change and groundwater exploitation on the spatial and temporal variations of heavy metal content in maize in the Luan River catchment of China

The effects of climate change and anthropogenic activities on the concentration of heavy metal in maize were quantitatively characterized in this study to help us better understand the complex interactions among the groundwater, vadose, plant, and atmosphere layers in the critical zone. We hypothesized that climate change and groundwater resource exploitation firstly affected the shallow groundwater level, and then the groundwater table fluctuation (GTF) impacted the concentration of heavy metal in maize through the critical zone (CZ) structure and parameters. To test our hypothesis, we collected 960 soil and 288 maize samples from the Luan River catchment in the North China Plain. The Groundwater Modeling System software was used to describe the effects of precipitation and groundwater resource exploitation on the groundwater table, and then, the structural equation method was employed to characterize the quantitative effects of GTF, precipitation, and air temperature on the concentration of heavy metal in maize. The results indicate that the influence coefficients of the effects of climate change and anthropogenic activities on the concentrations of Fe, Mn, Cr As, Pb, and Sr were 0.1595, 0.088, 0.0042, - 0.0092, 0.2219, and 0.0493 in the north plain, respectively, and 0.0256, 0.0151, 0.0816, - 0.2264, 0.1125, and - 0.0106 in the south plain of the study region, respectively. Since the human health risks of metals were mainly attributed to Fe, Mn, and Cr in the Luan River catchment, increasing the groundwater resource exploitation volume is an effective way to decrease the Fe, Mn, and Cr contents in maize by decreasing the shallow groundwater table.

Human health risk from consumption of two common crops grown in polluted soils

Contamination of agricultural soils by trace elements is a recurrent hazard for human health because of the possibility of pollutants entering the food chain. Aim of this study was to assess the human health risk from consumption of the common leafy (Lactuca sativa L.) and fruit (Cucurbita pepo L.) crops, in an agricultural area of Southern Italy. Along with agricultural practices, a major pollutant source is recurrent flooding from the highly polluted Solofrana river. Soil samples and edible parts of crops from 14 sites (10 flooded and 4 not flooded) were analyzed for total amounts of As, Cd, Co, Cr, Cu, Ni, Pb, V, Zn. The bio-accumulation factor (BAF) and Health Risk Index (HRI) were calculated for each element, crop and site and as average values of all sites (BAF_mean and HRI_mean). Moreover, the Hazard Index (HI) was determined for each site, as the sum of HRI for all elements. Cr and Cu, mostly derived from river flooding and agricultural practices, respectively, were the only elements whose levels exceeded law thresholds and/or the natural background of the study area. Of the two considered crops, L. sativa accumulated more Cd, Cr and Ni, whereas C. pepo was a more effective bioaccumulator of Zn. Both HRI_mean (for As, Cd, Cr and Ni) and HI were higher for L. sativa than for C. pepo. A low health risk was associated to major soil pollutants (Cr and Cu) found in the study area; in contrast, combined data on soil pollution and plant bio-accumulation points to accumulation of Cd and As, mainly in lettuce, as a potential risk for human health. The results suggest that soil pollution data alone is not sufficient to assess health risk.

Impact of some industrial solid wastes on the growth and heavy metal uptake of cucumber (Cucumis sativus L.) under salinity stress

This study was conducted to investigate the effect of industrial solid wastes (ISWs) and salinity on growth and heavy metals uptake by cucumber (Cucumis sativus L.). The soil was treated with 5% and 10% of the ceramic factory (CFW), stone cutting (SCW) and sugar factory (SFW) wastes. Plant of cucumber was grown under greenhouse conditions in control and ISWs treated soils and stressed with electrical conductivities of 0, 4 and 8 dS m^-1. Plants were harvested after 2 months and separated into root, shoot, and fruit. Then, dry weights and heavy metals contents in each fraction of plants were determined. The addition of all ISWs in soil increased total heavy metals content in the soil. In all treatments, growth parameters of cucumber decreased when irrigated with saline waters. As compared to control soil, the addition of CFW and SCW to soil decreased plant dry weight, while, it was improved with the addition of the SFW. The result of plant analysis showed that there was an increase in the contents of heavy metals (except Cr) in all parts of cucumber with the addition of ISWs. Salinity decreased the content of Zn uptake and increased another heavy metal uptake by all parts of the plants. The application of ISWs and salinity did not show a significant effect on bioconcentration (BCF) and transfer factor (TF) of heavy metals in plants. The health risk index (HRI) values of all heavy metals for both adults and children were found to be less than 1, so, the health risk of heavy metal for people who consume cucumber grown in these industrial areas was generally assumed to be safe.

Implementing chemical mass balance model and vulnerability the theories to realize the comprehensive evaluation in an abandoned battery plant

In China groundwater contamination has become a serious problem. The assessment and remediation of contaminated sites are greatly important. Moreover, only few studies deal with the influence of metal speciation on human health risk assessment. This paper proposed a comprehensive assessment methodology combined human health risk assessment and groundwater vulnerability assessment for contaminated area, exploring a more reasonable model for the Cd morphology simulation, and utilizing accurate method to calculate the average daily dose by the weight analysis. PHREEQC and Visual MINTEQ were applied and compared to the morphology simulation, the modified of average daily dose and non-modified of average daily dose was investigated, carcinogenic and non-carcinogenic risks were calculated subsequently. The groundwater vulnerability was assessed by the DRASTIC model, the DRASTIC index as the indicator of groundwater vulnerability. The morphology simulation results showed 20 and 13 metal species which were simulated by PHREEQC and Visual MINTEQ, respectively. Cd²⁺ and CdCl⁺ were the primary species of Cd in groundwater. The modified average daily dose showed less than the average daily dose in results. The carcinogenic risks showed the species of Cd²⁺ and CdCl⁺ were simulated by PHREEQC which were harmful to human health. The DRASTIC index was ranged from 109 to 134 in the studied area, which showed that the area was susceptible to pollution. This method provided a more effective risk assessment model and supplied a fundamental advice for government policy-making and site remediation.