Assessment of the variation of heavy metal pollutants in soil and crop plants through field and laboratory tests

A field trial for remediation of multi-metal contaminated soils using the combination of fly ash stabilization and Zanthoxylumbungeanum- Lolium perenne intercropping system

Insitu stabilization and phytoextraction are considered as two convenient and effective technologies for the remediation of toxic elements (TEs) in soils. However, the effectiveness of these two remediation technologies together on the bioavailability and phytoextraction of TEs in field trials has not been explored yet. Specifically, the remediation potential of fly ash (FA; as stabilizing agent) and ryegrass (as a TE accumulator) intercropped with a target crop for soil polluted with multiple TEs has not been investigated yet, particularly in long-term field trials. Therefore, in this study, a six-month combined remediation field experiment of FA stabilization and/or ryegrass intercropping (IR) was carried out on the farmland soils contaminated with As, Cd, Cr, Cu, Hg, Ni, Pb and Zn where Zanthoxylumbungeanum (ZB) trees as native crops were grown for years. The treatments include soil cultivated alone with ZB untreated- (control) and treated-with FA (FA), produced by burning lignite in Shaanxi Datong power plant, China, soil cultivated with ZB and ryegrass untreated- (IR) and treated-with FA (FA + IR). This was underpinned by a large-scale survey in Daiziying (China), which showed that the topsoils were polluted by Cd, Cu, Hg and Pb, and that Hg and Pb contents in the Zanthoxylumbungeanum fruits exceeded their allowable limits. The TEs contents in the studied FA were lower than their total element contents in the soil. The DTPA-extractable TEs contents of the remediation modes were as follows: FA < FA + IR < IR < control. Notably, TEs contents in the ZB fruits were lowest under the FA + IR treatment, which were decreased by 27.6% for As, 42.3% for Cd, 16.7% for Cr, 30.5% for Cu, 23.1% for Hg, 15.5% for Ni, 33.2% for Pb and 38.1% for Zn compared with the control treatment. Whereas the FA + IR treatment enhanced TEs contents in ryegrass shoots and roots, and the TEs contents in ryegrass shoots were below their regulatory limits for fodder crops. The findings confirmed that the combined remediation strategy, i.e., FA (with low content of TEs) stabilization effect and intercropping of ZB (target crop) and ryegrass (accumulating plant) could provide a prospective approach to produce target plants within safe TEs thresholds with greater economic benefits, while remediating soils polluted with multiple TEs and mitigating the potential ecological and human health risk. Those results are of great applicable concern.

Vetiver grass cleans up arsenic contaminated field for subsequent safe cultivation of rice with low arsenic in grains: A two year field study

The presence of high concentrations of arsenic (As) in agricultural soils and its subsequent accumulation in rice crop is a serious issue threatening sustainability of agriculture and human health. In the present work, remediation of As contaminated field in Nadia, West Bengal, India was done through the cultivation of Vetiver (Vetiveria zizanoides L. Nash) and the same field was subsequently used for rice (Oryza sativa L.) cultivation. The results showed that V. zizanoides could reduce As concentrations in the field to bring it lower than the maximum permissible limit (20 mg kg-1) in 11 months' time. The rice plants grown in remediated field showed improvement in growth and photosynthesis parameters as compared to that of contaminated field. Importantly, yield related parameters (filled seed, 1000 grain weight, number of panicles etc.) were also significantly higher in remediated field than that in contaminated field. Arsenic concentration in roots, shoot, husk and grains of rice was found to be significantly lower in remediated field than in contaminated field. Grain As decreased from 0.75 to 0.77 μg g-1 dw in contaminated field to 0.15-0.18 μg g-1 dw. In conclusion, replacing rice for single year with V. zizanoides crop can significantly remediate the field and can be a viable option.

Ecological and health risk assessments of heavy metals and their accumulation in a peanut-soil system

Heavy metals pollution is a notable threat to environment and human health. This study evaluated the potential ecological and health risks of heavy metals (Cu, Cr, Cd, Pb, Zn, Ni, and As) and their accumulation in a peanut-soil system based on 34 soil and peanut kernel paired samples across China. Soil As and Cd posed the greatest pollution risk with 47.1% and 17.6% of soil samples exceeding the risk screen levels, respectively, with 26.5% and 20.6% of the soil sites at relatively strong potential ecological risk level, respectively, and with the geo-accumulation levels at several soil sites in the uncontaminated to moderately contaminated categories. About 35.29% and 2.94% of soil sites were moderately and severely polluted based on Nemerow comprehensive pollution index, respectively, and a total of 32.4% of samples were at moderate ecological hazard level based on comprehensive potential ecological risk index values. The Cd, Cr, Ni, and Cu contents exceeded the standard in 11.76, 8.82, 11.76 and 5.88% of the peanut kernel samples, respectively. Soil metals posed more health risks to children than adults in the order As > Ni > Cr > Cu > Pb > Zn > Cd for non-carcinogenic health risks and Ni > Cr ≫ Cd > As > Pb for carcinogenic health risks. The soil As non-cancer risk index for children was greater than the permitted limits at 14 sites, and soil Ni and Cr posed the greatest carcinogenic risk to adults and children at many soil sites. The metals in peanut did not pose a non-carcinogenic risk according to standard. Peanut kernels had strong enrichment ability for Cd with an average bio-concentration factor (BCF) of 1.62. Soil metals contents and significant soil properties accounted for 35-74% of the variation in the BCF values of metals based on empirical prediction models.

Unveiling the Rising Threat of Cadmium Pollution and Alarming Health Risks Associated with the Consumption of 15 Commercially Important Fish Species in the Middle Stretch of River Ganga, at Patna, India

Among environmental contaminants, the rising level of cadmium in freshwater ecosystems is one of the most significant global concerns. The study addresses the current pollution status of cadmium in the middle stretch of River Ganga and explores the potential hazard associated with the consumption of 15 commercially important fish species by the inhabitants. Together 72 water and sediment samples were analyzed from the four representative sampling sites of River Ganga after the surveillance of major anthropogenic stressors. The concentration of cadmium ranges from 0.003 to 0.011 mg/l and 0.2 to 3.48 mg/kg in water and sediment respectively in 2022. The average concentration of cadmium was recorded to be the highest in Channa punctatus (1.35 mg/kg), followed by Rita rita = Johnius coitor (1.15 mg/kg), and the lowest in Labeo bata (0.2 mg/kg). The finding highlights greater exposure duration and feeding preferences of fish species have played a significant role in the bioaccumulation of the metal in the riverine system. Notably, the domestic effluents, agricultural runoffs, and pollutants brought along by the tributaries of River Ganga are identified as the main anthropogenic stressors for the moderate to considerably polluted status of the River Ganga. The target hazard quotient (THQ) and target carcinogenic risk (TCR) have revealed a higher susceptibility to cadmium contamination in children followed by females, and males. In addition, hierarchical cluster analysis (HCA) has noted intake of Rita rita, Channa punctata, Puntius sophore, and Johnius coitor could be more detrimental to children's health than adults.

Migration patterns of heavy metals from solid waste stockpile soils by native plants for ecological restoration in arid and semi-arid regions of Northwest China

Ecological remediation with native plants is the main measure to control the pollution of solid waste in Northwest China. However, the heavy metal transport characteristics of these native plants are still unidentified. This study analyzed the distribution of 16 heavy metals in native plants in the desulfurization gypsum yard (DGY), the gangue yard (GY) and the fly ash yard (FAY). The results showed that the soil contained many heavy metals in high concentrations. For instance, As concentrations were comparable to the global soil background values, whereas Cr and Mn concentrations in the area were 2-3 times greater than the global soil background values. The content of heavy metals in the plant root system increased first, then decreased as the distance from the yard increased. Ni, Pb, and Cd migrated well in Artemisia frigida Willd and Artemisia sieversiana Ehrhart ex Willd, with A. sieversiana showing a particularly strong migration in GY. A. sieversiana, on the other hand, was more successful at migrating Cd at DGY and had a similar capability for Mg migration in all three locations. Festuca rubra L was potentially suitable for planting in GY for Ni removal. In conclusion, the migration patterns of different heavy metals were not alike for plants in the three landfills. The results provided a basis for plant selection for ecological restoration in arid and semi-arid regions.

Health risk assessment of heavy metals in wild fish and seasonal variation and source identification of heavy metals in sediments: a case study of typical urban river in Xi'an, China

In order to determine the status of heavy metal pollution in river sediments and wild fish in Xi'an, concentrations of heavy metals (Cr, Ni, Cu, Zn, As, and Pb) were collected and analyzed in sediments and wild fish during dry season (October-November 2020) and wet season (June-July 2021). This study aimed to investigate the spatial and temporal variations of heavy metals in urban rivers of Xi'an, China. Their distribution characteristics and sources as well their pollution levels and health risks were assessed. The findings revealed that influenced by human activities, the heavy metal content in sediments (mg·kg-1 dry weight) in wet season was ranked as follows: Cr (73.09) > Zn (63.73) > Pb (40.31) > Ni (31.52) > Cu (24.86) > As (6.83); in the dry season: Zn (94.07) > Cr (69.59) > Cu (34.24) > Ni (33.60) > Pb (32.87) > As (7.60). Moreover, 32 fish samples from six species indicated an average metal content trend (mg·kg-1 wet weight) of Zn (8.70) > Cr (0.57) > Pb (0.28) > Ni (0.27) > Cu (0.24) > As (0.05). The potential ecological risk indices for sediment heavy metal concentrations in both seasons were well below the thresholds, which indicates that the aquatic environment is in safe level. The analysis of the potential ecological risk of sediment heavy metal concentrations indicates that the aquatic environment is safe for the time being. Based on the estimated daily intake (EDI), target risk quotient (THQ), total target risk quotient (TTHQ), cancer risk (CR), total cancer risk (TCR), and the permissible safety limits set by the agencies, the consumption of the fish examined is safe for human health. However, the presence of Cr and As in wild fish should still be a concern for human health, especially for children. The cumulative effect of heavy metals and the bioconcentration factor (BCF) suggest that sediment and heavy metals in fish are closely related, with higher concentrations in fish living in the bottom layer of the water column than in other water layers, and increasing with increasing predator levels. Correlation analysis and PMF modeling identified and determined four comparable categories of potential sources, namely, (1) atmospheric deposition and traffic sources, (2) agricultural sources, (3) industrial sources, and (4) natural sources.

Melatonin alleviated cadmium accumulation and toxicity by modulating phytohormonal balance and antioxidant metabolism in rice

Cadmium (Cd) contamination is an eminent dilemma that jeopardizes global food safety and security, especially through its phytotoxicity in rice; one of the most edible crops. Melatonin (MET) has emerged as a protective phytohormone in stress conditions, but the defensive role and underlying mechanisms of MET against Cd toxicity in rice still remain unclear. To fulfill this knowledge gap, the present study is to uncover the key mechanisms for MET-mediated Cd-stress tolerance in rice. Cd toxicity significantly reduced growth by hindering the process of photosynthesis, cellular redox homeostasis, phytohormonal imbalance, and ultrastructural damages. Contrarily, MET supplementation considerably improved growth attributes, photosynthetic efficiency, and cellular ultrastructure as measured by gas exchange elements, chlorophyll content, reduced Cd accumulation, and ultrastructural analysis via transmission electron microscopy (TEM). MET treatment significantly reduced Cd accumulation (39.25%/31.58%), MDA (25.87%/19.45%), H2O2 (17.93%/9.56%), and O2 (29.11%/27.14%) levels in shoot/root tissues, respectively, when compared with Cd treatment. More importantly, MET manifested association with stress responsive phytohormones (ABA and IAA) and boosted the defense mechanisms of plant by enhancing the activities of ROS-scavenging antioxidant enzymes (SOD; superoxide dismutase, POD; peroxidase, CAT; catalase, APX; ascorbate peroxidase) and as well as regulating the key stress-responsive genes (OsSOD1, OsPOD1, OsCAT2, OsAPX1), thereby reinstate cellular membrane integrity and confer tolerance to ultrastructural damages under Cd-induced phytotoxicity. Overall, our findings emphasized the potential of MET as a long-term and cost-effective approach to Cd remediation in paddy soils, which can pave the way for a healthier and more environmentally conscious agricultural sector.

Assessment of mercury bioavailability in garden soils around a former nonferrous metal mining area using DGT, accumulation in vegetables, and implications for health risk

Mercury (Hg) is a toxic, non-essential element for living organisms, frequently present in high concentrations in soils from industrial areas. The total, dissolved, and labile Hg concentrations in garden soils and their accumulation in edible vegetables (onion, garlic, lettuce, and parsley) grown on contaminated soils in localities situated a former mining area were evaluated. The labile Hg fraction was estimated by diffusive gradient in thin films (DGT). The soil-to-vegetable transfer factors, as well as the health risk by exposure to Hg, were calculated based on the labile Hg concentration in soil. The total Hg concentration in soil varied widely (0.11-3.77 mg kg-1), Hg in soil solution ranged between 2.14 and 20.2 μg L-1 and labile Hg between 1.13 and 18.6 μg L-1. About 36-96% (84% on average) of the Hg concentration in soil solution was found in labile form. Multivariate analysis revealed significant correlations between the labile Hg concentration in soil and Hg accumulated in vegetables. The hazard indices showed that, although the study area is affected by legacy pollution, exposure to soil and consumption of locally grown vegetables do not pose health risks.

Health risk assessment of heavy metal pollution and its sources in agricultural soils near Hongfeng Lake in the mining area of Guizhou Province, China

Background

Accelerated modern industrial processes, extensive use of pesticides and fertilizers and remaining issues of wastewater irrigation have led to an increasingly severe composite pollution of heavy metals in arable land. Soil contamination can cause significant damage to ecological environments and human health. Mineral resource mining can result in varying degrees of heavy metal pollution in surrounding water systems and soil. As a plateau lake, Hongfeng Lake has a fragile watershed ecosystem. Coupled with the rapid development of the current socio-economy and the ongoing activities of mining, urbanization and agricultural development, the water and soil environment of the lake and arable land are facing serious heavy metal pollution. Therefore, the situation warrants attention.

Methods

This study focused on characterizing soil types and conducted sampling and laboratory testing on the farmland soil in Hongfeng Lake. The integrated Nemero comprehensive pollution assessment and potential ecological pollution assessment methods were used to evaluate the heavy metal pollution status. The APCS-MLR model was employed to explore the sources of heavy metal pollution. In addition, the human health risk model was used to analyze the association between heavy metal content in cultivated land and human health risks.

Results

The single-factor pollution of each element was ranked in descending order: Hg > As > Pb > Cr > Cd, with Hg being the main pollutant factor. The entire area was subjected to mild pollution according to the pollution index. Pollution source analysis indicated two main pollution sources. Hg, As, Pb and Cr pollution mainly resulted from Source 1 (industrial and natural activities), accounting for 71.99%, 51.57%, 67.39% and 68.36%, respectively. Cd pollution was mainly attributed to Source 2 (agricultural pollution source), contributing 84.12%. The health risk assessment model shows that heavy metals posed acceptable carcinogenic risks to humans rather than non-carcinogenic risks. As was the main non-carcinogenic risk factor, while Cr was the main carcinogenic risk factor, with higher risks in children than adults.

Conclusion

Our study identified the heavy metal pollution in farmland soil in Hongfeng Lake, evaluated and analyzed the pollution sources and identified the heavy metal elements in cultivated lands that have the greatest impact on human health risks. The aim of this study is to provide a scientific basis for soil heavy metal pollution control.

Source and migration patterns of heavy metals and human health risk assessment of heavy metals in soil-corn straw-flue gas system

The process of rapid urbanization in Northeast China has resulted in severe heavy metal pollution in the environment. In this study, we investigated the characteristics of heavy metal pollution in soil-corn straw and its combustion flue gas system, and the health risks of heavy metal pollution. The results showed that Cu and Zn in soil were more easily absorbed by corn straw roots. Heavy metals in soil, corn straw and flue gas from corn straw burning all pose some health risk to humans, and are more harmful to children than adults. The concentrations of heavy metals in both soil and flue gas from corn straw burning have reached extremely high ecological risk. The main sources of heavy metal elements in soils are, in order, industrial production, agricultural production activities and metallurgical production. This study highlights the key issues of heavy metal contamination in soil-corn straw and its combustion flue gas system, provides an auxiliary guide for the next step in analyzing the transfer mechanisms, and suggests a rational approach to mitigate heavy metal contamination.

Biogenic silicon nanoparticles mitigate cadmium (Cd) toxicity in rapeseed (Brassica napus L.) by modulating the cellular oxidative stress metabolism and reducing Cd translocation

Nano-enabled strategies have emerged as promising alternatives to resolve heavy metals (HMs) related harms in an eco-friendly manner. Here, we explored the potential of biogenic silicon nanoparticles (SiNPs) in alleviating cadmium (Cd) stress in rapeseed (Brassica napus L.) plants by modulating cellular oxidative repair mechanisms. Biogenic SiNPs of spherical shapes with size ranging between 14 nm and 35 nm were synthesized using rice straw extract and characterized through advanced characterization techniques. A greenhouse experiment results showed that SiNPs treatment at 250 mg kg-1 significantly improved growth parameters, including fresh weight (33.3 %) and dry weight (32.6 %) of rapeseed plants than Cd-treated control group. Photosynthesis and leaf gas exchange parameters were also positively influenced by SiNPs treatment, indicating enhanced photosynthetic efficiency. Additionally, SiNPs treatment at 250 mg kg-1 increased the activities of antioxidant enzymes such as superoxide dismutase (19.1 %), peroxidase (33.4 %), catalase (14.4 %), and ascorbate peroxidase (33.8 %), which may play a crucial role in ROS scavenging and reduction in Cd-induced oxidative stress. TEM analysis revealed that SiNPs treatment effectively mitigated Cd-induced damage to leaf ultrastructure, while qPCR analysis showed that SiNPs treatment changed the expressions of the antioxidant defense and stress related genes. Moreover, SiNPs treatment significantly influenced the Cd accumulation and Si contents in plants. Overall, our findings revealed that biogenic SiNPs have great potential to serve as a sustainable, eco-friendly, and non-toxic alternative for the remediation of Cd toxicity in rapeseed plants.

Reliability of stored river water as an alternative for consumption in Ekpoma, Nigeria: a human health risk assessment

With looming global water-related issues, the monitoring of water quality for household and industrial consumption has become more pertinent. Rivers in nearby towns serve as primary water sources for Ekpoma town. 123 samples of stored river water were collected from 41 sampling locations and physical properties - pH, electrical conductivity (EC), salinity, temperature, and total dissolved solids (TDS) - were measured in situ using the Hanna edge® Multiparameter EC/TDS/Salinity Meter-HI2030. Atomic absorption spectrophotometry (AAS) was used to detect and measure the concentration of potentially toxic metals (PTMs): Al, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. The measured concentrations were compared to the WHO, US EPA, and NSDWQ regulatory standards, and a spatiotemporal health risk analysis was performed using HERisk software. Twenty-five percent of the tested samples contained PTM concentrations within the allowable regulatory limits. Spatiotemporal health risk analysis showed that 98.8% of the cumulative carcinogenic risks (CRcum) were entirely from Pb contamination via oral ingestion. PTM concentrations in the samples suggest the degradation of river water quality due to agricultural activities, crude oil exploration activities, and soil composition in the region. Best management practices (BMPs) and treatment processes for the removal of detected contaminants are recommended to improve water quality.

First-principle study on the stability of Cd passivates in soil

The stable existence of heavy metals in soil under natural conditions is the core issue in heavy metal pollution solidification and remediation technology. However, the existing research is limited to soil passivation tests of different materials or biochar adsorption tests and cannot reveal the internal mechanism of functional groups of different compounds in soil passivation. This paper takes the common heavy metal ion Cd²⁺ as an example to analyze the stability of the combination of heavy metal ions and common ion groups in soil. The stability and existing form of Cd are analyzed by using first-principle calculations, and the free energy, band structure, and partial density of states of CdCO₃, CdSO₄, CdCl₂, and CdSiO₃ are computed. The stability of Cd binding to common anions in soil is determined. Results show the descending order of structural stability of cadmium compounds is CdSiO₃, CdSO₄, CdCO₃, and CdCl₂. SO₄^2- and SiO₃^2- can be used as preferred functional groups for cadmium pollution passivation. Anhydrous sodium sulfate and sodium silicate are promising passivators.

A Multi-Method Approach for Impact Assessment of Some Heavy Metals on Lactuca sativa L

Heavy metals represent a large category of pollutants. Heavy metals are the focus of researchers around the world, mainly due to their harmful effects on plants. In this paper, the influence of copper, cadmium, manganese, nickel, zinc and lead, present in soil in different concentrations (below the permissible limit, the maximum permissible concentration and a concentration higher than the maximum permissible limit) on lettuce (Lactuca sativa L.) was evaluated. For this purpose, the authors analyzed the variation of photosynthetic pigments, total polyphenols, antioxidant activity and the elemental content in the studied plants. The experimental results showed that the variation of the content of biologically active compounds, elemental content and the antioxidant activity in the plants grown in contaminated soil, compared to the control plants, depends on the type and concentration of the metal added to the soil. The biggest decrease was recorded for plants grown in soil treated with Ni I (-42.38%) for chlorophyll a, Zn II (-32.92%) for chlorophyll b, Ni I (-40.46%) for carotenoids, Pb I (-40.95%) for polyphenols and Cu III (-29.42%) for DPPH. On the other hand, the largest increase regarding the amount of biologically active compounds was registered for Mn I (88.24%) in the case of the chlorophyll a, Mn I (65.56%) for chlorophyll b, Pb I (116.03%) for carotenoids, Ni III (1351.23%) for polyphenols and Ni III (1149.35%) for DPPH.

Role of biochar-based free radicals in immobilization and speciation of metals in the contaminated soil-plant environment

The structure of biochar produced at various pyrolysis temperatures influences metal geochemical behavior. Here, the impact of wheat straw-derived biochar (300, 500, and 700 °C) on the immobilization and transformation of metals in the contaminated soil-plant system was assessed. The findings of the sequential extraction revealed that biochar additives had a substantial influence on the speciation of Cr, Ni, Pb, and Zn in the contaminated soil. The lowest F1 (exchangeable and soluble fraction) + F2 (carbonate fraction) accounted for Cr (44%) in WB-300, Ni (43.87%) in WB-500, Pb (43.79%), and Zn (49.78%) in WB-700 with applied amendments of their total amounts. The characterization results indicated that high pyrolysis temperatures (300-700 °C) increased the carbon-containing groups with the potential to adsorb metals from the soil-plant environment. The bioconcentration and translocation factors (BCF and TF) were less than 1, indicating that metal concentration was restricted to maize roots and translocation to shoots. Reactive oxygen species (ROS) intracellularly influence metal interactions with plants. Electron paramagnetic resonance (EPR) was performed to determine hydroxyl radical generation (•OH) in plant segments to assess the dominance of free radicals (FRs). Consequently, the formation of •OH significantly depends on the pyrolysis temperature and the interaction with a contaminated soil-plant environment. Thus, metal transformation can be effectively decreased in the soil-plant environment by applying WB amendments.

Pollution Risk Assessment and Sources Analysis of Heavy Metal in Soil from Bamboo Shoots

In order to investigate the pollution situation and sources analysis of heavy metals in bamboo shoot soil in Guangdong Province, a total of 175 soil samples were collected at 46 sites. Atomic fluorescence spectrophotometer and inductively coupled plasma mass spectrometry were used to determine the content of five heavy metals: lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), and chromium (Cr). In addition, the soil environmental quality was evaluated through different index methods, including single-factor pollution, Nemeiro comprehensive pollution, geoaccumulation, and potential ecological risk. Furthermore, the correlation coefficients were also discussed. The results showed that the soils collected were acidic or slight alkaline. The maximum content of Pb and As from some areas exceeded the standard limit value. The coefficient of variation value from six areas exceeded 100%. The index method mentioned above confirmed that the soil within study areas was divided into three pollution levels: no, slightly, and mild. Additionally, there was a very significant correlation between pH and Pb, Hg; the correlation between heavy metal As and Pb, Cr also reached a very significant level. The principal component analysis results show that PC1 accounts for 39.60% of the total variance, which includes Pb, Cd, and As. PC2 mainly includes Hg and Cr.

Soil Quality Assessment in Farmland of a Rapidly Industrializing Area in the Yangtze Delta, China

The comprehensive quality assessment of farmland soil is critical for agricultural production and soil ecological protection. Currently, there is no systematic method for conducting a comprehensive quality assessment of farmland soil; subsequently, as the most developed economic area in China, the comprehensive quality assessment of farmland soil in the Yangtze River Delta is lacking. We chose the farmland soil of Suzhou city as the research object. The soil fertility index (SFI) and soil environment index (SEI) were calculated with the membership function and Nemerow index. Finally, the comprehensive assessment of soil quality was achieved with the TOPSIS model. The results showed that the average values of soil pH, SOM, TN, AHN, AP, and AK were 6.44 (slightly acidic), 28.17 g/kg (medium), 1.63 g/kg (rich), 118.16 mg/kg (medium), 38.31 mg/kg (rich), and 160.63 mg/kg (rich), respectively. For the concentrations of heavy metals, including Cr, Ni, Cu, Zn, Cd, and Pb, in 122 soil samples, the percentages exceeding the background values of Jiangsu province were 5.74%, 8.20%, 8.20%, 10.66%, 86.07%, and 84.43%, respectively. Cd and Pb were the main heavy metal pollutants on farmlands. The soil samples with SFI values below the medium level (SFI < 0.6) accounted for 44.26%, and samples with SEI values below the medium level (SEI < 0.6) accounted for 13.12%. The values of the soil quality index (SQI) ranged from 0.171 to 0.996, with an average SQI value of 0.586 (very poor-V), and approximately half of the farmland soil quality in Suzhou city needed to be further improved. In a word, this study provides a theoretical basis and scientific support for the quality assessment and rational utilization of farmland soil.

Risk assessment and early warning of the presence of heavy metal pollution in strawberries

Heavy metal pollution is a major threat to agricultural produce and it can pose potential ecological risks which subsequently impacts on human health. Strawberries are an economically important produce of China. The intrinsic link of heavy metal pollution risk in the soil-strawberry ecosystem is of concern. In this study, the pollution index of heavy metal pollutants in farmlands of different provinces were evaluated, and the results showed significantly high levels of cadmium. In addition, Nemerow integrated pollution index analysis showed that low-pollution farmlands only accounted for 14.07% of the total arable land area. Then, the transfer factors were used to calculate the migration of heavy metals from the soil into strawberries. The results showed that cadmium and nickel were relatively high in strawberries from the Guangxi province. Similar results were found for mercury in Jiangxi Province. The pollution index of single food pollution also showed that mercury in strawberries from Jiangxi Province was at a moderate pollution level. The comprehensive pollution index indicated that heavy metal pollution in strawberries in Central China may be severe. In addition, spatial clustering analysis showed that cadmium, chromium, lead, arsenic and zinc in strawberries had significant hotspot clustering in central, south and southwest China. Finally, our studies also suggested that the risk of carcinogenic and non-carcinogenic diseases was higher in the (2, 4] years age group than in other age groups. People in Yunnan Province were also found to have a higher non-carcinogenic risk than those in other provinces and cities in China. This study provides a comprehensive view of the potential risks of heavy metal contamination in strawberries, which could provide assistance in the design of regulatory and risk management programs for chemical pollutants in strawberries, thus ensuring the safety of consumption of these edible fruits.

Effects of composite environmental materials on the passivation and biochemical effectiveness of Pb and Cd in soil: Analyses at the ex-planta of the Pak-choi root and leave

Passivation of soil heavy metals using environmental materials is an important method or important in situ remediation measure. There are more studies on inorganic environmental materials for heavy metal passivation, but not enough studies on organic and their composite environmental materials with inorganic ones. In order to reveal the passivation effect of coal-based ammoniated humic acid (CAHA), biochemical humic acid (BHA), biochar (BC) and other organic types and inorganic environmental materials such as zeolites (ZL) on soil heavy metals and their biological effectiveness. The microstructures of these materials were analyzed by Scanning electron microscope (SEM). The main components of the environmental materials were analyzed by Energy dispersive spectrometer (EDS), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction spectrum (XRD) to elucidate the mechanism of passivation of heavy metals in soil by these environmental materials. The study was conducted to investigate the effects of different types of environmental materials and their combinations on the passivation effect and biological effectiveness of Pb and Cd complex contamination in soil by means of soil incubation and pot experiments using single-factor and multifactor multilevel orthogonal experimental designs. Soil incubation experiments proved that the effective state of soil Pb and Cd in T₇ was reduced by 13.40% and 11.07%, respectively. The extreme difference analysis determined the optimized formulation of soil lead and cadmium passivation as BHA: CAHA: BC: ZL = 3.5:5:20:10. The pot experiment proved that the application of composite environmental materials led to the reduction of lead and cadmium content and increase of biomass of Pak-choi, and the optimal dosage of optimized composite environmental materials was 23.1 g/kg.

Bioaccumulation characteristics, transfer model of heavy metals in soil-crop system and health assessment in plateau region, China

This study investigated the bioaccumulation and transfer of heavy metals including Cd, Cr, Cu, Mn, Ni, Pb and Zn in soil-crop system in Lhasa, and assessed the health risks of the edible part of the crops. The results showed that the average values of Cd, Cr, Cu, Mn, Ni, Pb and Zn were 0.15, 44.55, 24.68, 532.40, 22.47, 38.18 and 73.99 mg kg^-1 in natural soil, and 0.16, 46.93, 38.45, 559.13, 23.23, 40.03 and 83.29 mg kg^-1 in cultivated soil, respectively. Highland barley and wheat had the strongest ability to accumulate Zn in grain, the BCF values were 0.24 and 0.27, respectively, significant differences in the distribution of metal contents in crop root, stem, leaf and grain were observed. Root presented larger accumulation capacity in most metals, Zn and Cu was easily transferred in the plant organs, most metals in this study presented difficult to migrate from root to grain. The transfer peak of most metals in soil-crop system appeared from stem to leaf. The concentrations of Cr and Mn in crop grains could be predicted according to the multiple linear regression models. THQ and HI values of heavy metals in edible parts of both highland barley and wheat were below the safety threshold of 1, indicating no detrimental effects posed to adults health. This study helps to understand the accumulation and transfer of heavy metals in soil-crop system in plateau region.

Insights on synthesis and applications of graphene-based materials in wastewater treatment: A review

Graphene has excellent unique thermal, chemical, optical, and mechanical properties such as high thermal conductivity, high chemical stability, optical transmittance, high current density, higher surface area, etc. Due to their outstanding properties, the attention towards graphene-based materials and their derivatives in wastewater treatment has been increased in recent times. Different graphene-based materials such as graphene oxides, graphene quantum dots, graphene nanoplatelets, graphene nanoribbons and other graphene-based nanocomposites are synthesized through chemical vapor deposition, mechanical and electrochemical exfoliation of graphite. In this review, the specifics about the graphenes and their derivatives, the synthesis strategy of graphene-based materials are described. This review critically explained the applications of graphene-based materials in wastewater treatment. Graphene-based materials were utilized as adsorbents, electrodes, and photocatalysts for the efficient removal of toxic pollutants such as heavy metals, dyes, pharmaceutics, antibiotics, phenols, polycyclic aromatic hydrocarbons have been highlighted and discussed. Herein, the potential scope of graphene-based material in the field of wastewater treatment is critically reviewed. In addition, a brief perspective on future research directions and difficulties in the synthesis of graphene-based material are summarized.