Heavy Metals In Crops Research Articles

Meta-analysis of Heavy Metal Pollution in Soil-crop Systems in China's Urban-Rural Fringe

Owing to the influence of human activities, the issue of heavy metal pollution in farmland soil at the urban-rural fringe has become increasingly prominent. An accurate understanding of the characteristics of soil-crop heavy metal pollution in these areas is of great significance for ensuring food safety and promoting social sustainable development. Most of the existing studies rely on small-scale field monitoring, but research at the national level has not effectively captured the unique pollution dynamics of this urban-rural interface. Based on the published literature, the present study investigated the status of heavy metal pollution in the soil-crop system within China's urban-rural fringe through Meta-analysis. On this basis, the study evaluated the risks to human health associated with heavy metals in major crops in a given region. The results showed that heavy metals were accumulated in farmland soil in the urban-rural fringe of China, especially in Cd （Igeo = 0.89） pollution, and its distinct spatial heterogeneity patterns emerged. When considering different types of cultivated land, paddy fields and irrigated land exhibited a higher tendency of heavy metal accumulation. From the varying urbanization levels, the accumulation of heavy metals in soils of small and medium-sized cities was more obvious. For crops in the urban-rural fringe, Cd and Pb had the highest exceedance rate in rice （28.25% and 39.64%） and wheat （27.72% and 42.72%）. The health risk assessment results of heavy metals in crops showed that Cd was the main element that posed human health risks, which had some degree of non-carcinogenic risk and unacceptable carcinogenic risk to both children and adults.

Transport characteristics of heavy metals in the soil-atmosphere-wheat system in farming areas and development of multiple linear regression predictive model

Heavy metal accumulation in agricultural products has become a major concern. Previous studies have focused on the transport of heavy metals from the soil and their accumulation in crops. However, recent studies revealed that wheat leaves, ears, and awns can also transport and accumulate heavy metals. Wheat grains can be influenced by two sources of heavy metals: soil contamination and atmospheric deposition. To comprehend the transport characteristics of heavy metals in soil, atmospheric deposition, and wheat, 37 samples each for wheat rhizosphere soil, wheat roots, stems, leaves, and grains were collected. Fifteen samples of atmospheric dry deposition and atmospheric wet deposition were collected from Linshu County (northern area), China. Based on the test data, the characteristics of heavy metals and their distribution in the study area were analyzed. Migration patterns of heavy metals in crops from different sources were investigated using Pearson correlation and redundancy analysis. Finally, a predictive model for heavy metals in wheat grains was developed using multiple linear regression analysis. Significant disparities in the distribution of heavy metals existed among wheat roots, stems, leaves, and grains. The coefficient of variation of heavy metals in atmospheric deposition was relatively high, indicating discernible spatial patterns influenced by human activities. Notably, a positive correlation was observed between the concentration of heavy metals in wheat grains and atmospheric deposition of Hg, Cd, and Pb. Conversely, Zn and Ni levels in wheat grains were significantly negatively associated with soil Zn, Ni, pH, and OM content. The contribution of heavy metal elements from different sources varied in their impact on the grain's heavy metal content. Specifically, atmospheric deposition was the primary source of Hg and Pb in wheat grains, while Cd, Ni, Cu, and Zn were predominantly derived from soil. Using a multiple linear regression model, we could accurately predict Hg, Pb, Cd, Ni, Zn, and As concentrations in crop grains. This model can facilitate quantitative evaluation of ecological risk of heavy metals accumulation in crops in the study area.

Elevated Uptake and Translocation Patterns of Heavy Metals in Different Food Plants Parts and Their Impacts on Human Health.

Irrigation with contaminated wastewater is a common practice in cultivation of crops and vegetables in many developing countries due to the scarcity of available fresh water. The present study has investigated the transfer and mobilization trends of heavy metals in different crops and vegetables plants grown in contaminated soil and waterbody. The translocation patterns of metals from polluted sources into different organs of plants bodies such as roots and edible parts and associated health risks have been evaluated simultaneously. Total of 180 different environmental samples including food plants, agricultural soil, and irrigation water were collected and analyzed. Heavy metal concentrations (Fe, Ni, Mn, Pb, Cu, Cd, As) in water, soil, and different parts of crops and vegetable plants were compared with the permissible levels reported by FAO/WHO, EU, and USEPA. Different metals contents within the food plants were found to be in the order of Fe > Mn > Ni > Cu > Pb > Cd > As. Pollution load index (PLI) data indicate that soil is highly polluted with Cd as well as moderately contaminated by As and Cu. Bioconcentration factor (BCF) analysis showed excessive accumulation of some heavy metals in crops and vegetables. Target hazard quotient (THQ) and target carcinogenic risk (TCR) analysis data showed higher carcinogenic and non-carcinogenic risks for both adult and children from the consumption of metal-contaminated food items. The results of metal pollution index (MPI), estimated daily intake (EDI), and hazard index (HI) analyses demonstrated the patterns of metals pollution in different food plants.

Heavy Metals in Agricultural Soils: Sources, Influencing Factors, and Remediation Strategies.

Soil heavy metal pollution is a global environmental challenge, posing significant threats to eco-environment, agricultural development, and human health. In recent years, advanced and effective remediation strategies for heavy metal-contaminated soils have developed rapidly, and a systematical summarization of this progress is important. In this review paper, first, the anthropogenic sources of heavy metals in agricultural soils, including atmospheric deposition, animal manure, mineral fertilizers, and pesticides, are summarized. Second, the accumulation of heavy metals in crops as influenced by the plant characteristics and soil factors is analyzed. Then, the reducing strategies, including low-metal cultivar selection/breeding, physiological blocking, water management, and soil amendment are evaluated. Finally, the phytoremediation in terms of remediation efficiency and applicability is discussed. Therefore, this review provides helpful guidance for better selection and development of the control/remediation technologies for heavy metal-contaminated agricultural soils.

MOBILE FORMS OF HEAVY METALS IN TYPICAL CHERNOZEM OF THE BASHKORTOSTAN REPUBLIC, CONTAMINATED WITH OIL AND SODIUM CHLORIDE, UNDER THE CONDITIONS OF A FIELD EXPERIMENT

The influence of oil pollution and concomitant salinization of chernozem typical in a fi eld experiment has been studied. It is shown that the oil intake of 2 and 3 g·kg-1 with or without sodium chloride 1 g·kg-1 does not have a negative effect. It was found that under the influence of salinization, the content of mobile forms of heavy metals increases by an average of 1.5 times. The analysis of the content of heavy metals in crops cultivated on the territory of the Republic of Bashkiria (Pisum sativum L., Triticum aestivum L.) aft er contamination with oil and sodium chloride was carried out both individually and jointly in a fi eld experiment. The content of mobile forms of heavy metals in the soil under the influence of two crops is different, which is due to the physiological characteristics of crops and the influence of pollutants.

Effect of Biogas Slurry Return to Field on Heavy Metal Accumulation in Soil-crop System: A Meta-analysis

To investigate the effects of biogas slurry return-to-field methods, the duration of biogas slurry return to field and the amount of heavy metals brought in from biogas slurry on the accumulation of heavy metals in soil-crop systems, and the importance of factors influencing heavy metal accumulation, 41 papers and 1972 pairs of data were integrated and analyzed. The results showed that the application of biogas slurry alone significantly increased the accumulation of As, Cd, Cr, Cu, and Zn in soil and As and Cr in crops by 20.5%, 15.2%, 25.6%, 18.7%, and 26.3% and 14.6% and 39.5%, respectively, and it had no significant effect on the accumulation of other heavy metals in crops. The combined application of biogas slurry and chemical fertilizers significantly increased the accumulation of soil Cr and Zn by 8.05% and 4.70% and decreased the accumulation of As by crops. Correlation analysis showed that the accumulation rates of soil As, Cd, and Cr were highly significantly and positively correlated (P<0.01) with the duration of biogas slurry return to field and soil organic matter (SOM) content, with correlation coefficients of 0.30, 0.15, and 0.13 and 0.22, 0.27, and 0.22, respectively; they were highly significantly and negatively correlated (P<0.01) with soil pH, with correlation coefficients of 0.16, 0.13, and 0.11, respectively. The heavy metals brought in by biogas slurry return to field promoted the accumulation of As, Cd, and Cr in soil and As, Cd, Cr, and Zn in crops, whereas the accumulation of Cd, Cu, and Zn in soil promoted the accumulation of Cd, Cu, and Zn in crops, with correlation coefficients of 0.45, 0.58, and 0.42, respectively. The main factors of heavy metal accumulation in the soil-crop systems were the duration of biogas slurry return to field, SOM, and soil pH.

Scale transfer learning of hyperspectral prediction model of heavy metal content in maize: From laboratory to satellite

ABSTRACT For sustainable development of the environment, there has been a growing interest in using remote sensing technology to monitor the content of heavy metals in crops. Satellite hyperspectral data, while capable of providing valuable information, is often subject to environmental factors. On the other hand, laboratory spectra are collected under controlled conditions, enabling more accurate and stable models to be built. As a result, this study used the laboratory maize spectra measured using an SVC spectrometer to establish the heavy metal content prediction model and applied it to hyperspectral satellite images (Gaofen-5 and Zhuhai-1) to achieve large-scale and rapid monitoring of heavy metal content in farmland maize. However, due to the difference between the laboratory spectra (source domain) and satellite spectra (target domain), the direct transfer of laboratory models to the satellite scale has shown poor results. To address this challenge, multiple factors, including spectral feature selection, domain adaptation, regression methods, and correction models were taken into account to construct the multi-factor combined model. The research has shown that modelling after spectral feature selection can increase the accuracy of the model while reducing its complexity. Additionally, the domain adaptation method can narrow the gap between the source domain and the target domain, improving the transfer learning performance of different domains to a certain extent. Furthermore, the addition of a constructed correction model generally improves the accuracy of the transfer model. The optimal transferable model is finally obtained, which can effectively apply the laboratory heavy metal content prediction model to satellite images, and achieve large-scale and rapid monitoring of heavy metal content in farmland maize.

Availability of Se-rich Arable Land in High Geological Background Area and Suggestions for Zoning

In order to promote the results of land quality geochemical surveys to serve the development of characteristic land resources and realize the safe utilization of Se-rich resources in high geological background areas, Wuli Town, Qianjiang District, Chongqing City were taken as the research object to evaluate the Se-rich level and heavy metal content of soil crops and carry out research on Se-rich cultivated area division and the availability method system in the high geological background area, in order to improve the utilization efficiency of Se-rich resources and provide ideas for the safe utilization of Se-rich resources in high geological background areas. The results showed that the soil and crops in the study area were rich in Se and had the potential to develop Se-rich resources, but some samples had the problem of excessive Cd. Soil pH was a key factor affecting the content of Se and Cd in crops, and alkaline conditions were conducive to the safe utilization of Se-rich resources. The areas of Class A-E (A:selenium-enriched arable land, B:crops that were not selenium-enriched but were safe, C:crops that were selenium-enriched but unsafe, D:crops that were not selenium-enriched and unsafe, and E:soil selenium content less than the selenium-enriched threshold and soil heavy metals not exceeding the standard)cultivated land were 0.72, 0.75, 0.28, 0.13, and 0.56 km2, respectively. It is recommended to develop safe and Se-rich resources in the distribution area of Class A cultivated land and to carry out soil acidification conditioning and low-accumulation crops in the distribution area of Class C and D cultivated land; other agronomic measures should be taken to reduce the risk of excessive heavy metals in crops and strengthen the protection of cultivated land in the region to prevent the input of new pollutants.

Risk Assessment of Heavy Metal in Farmlands and Crops Near Pb–Zn Mine Tailing Ponds in Niujiaotang, China

To accurately evaluate the pollution and risk of heavy metals in crops and farmlands near mines, we determined the contents of Cr, Ni, Cu, As, Cd, Pb, and Zn in 10 farmland soil sampling sites and six crops (pak choi, rice, spring onion, radish, Chinese cabbage, Chrysanthemum coronarium) in an area near the Niujiaotang Pb-Zn mine in Duyun City, China. Four evaluation methods were compared, including the potential ecological hazard index, Nemeiro comprehensive pollution assessment, risk assessment code, and the ratio of secondary phase to primary phase methods. The average concentration of As, Cd, Pb, and Zn exceeded the soil environmental background levels in Niujiaotang and Guizhou Province. Cd exceeded the standard substantially, and Zn pollution accumulation was the most evident. Heavy metal contamination of crops was in the order pak choi > Chinese cabbage > spring onion > paddy > radish > Chrysanthemum coronarium, whereas heavy metal concentration in crops were in the order Zn > As > Cr > Cd > Ni > Pb. The levels of all heavy metals except Cu exceeded Chinese food hygiene standards. Carcinogenic and non-carcinogenic chemicals in crops present significant risks to adults and children. Risk evaluation considering the morphological contents of heavy metals rather than their total concentration was more accurate for environmental quality assessment of agricultural soils. Samples should be collected at different times to study the spatial and temporal distribution, and further studies on the migration transformation of heavy metals between the tailings pond-soil-crop should be conducted.

A review on adsorption characteristics and influencing mechanism of heavy metals in farmland soil.

The accumulation of heavy metals in soil and crops is considered to be a severe environmental problem due to its various harmful effects on animals and plants. Soil adsorption is an essential characteristic of mud, which is the fundamental reason for soil to have a specific self-purification capacity and environmental capacity for heavy metals. The adsorption of heavy metals by soil reduces the uptake of these pollutants by crops, thereby limiting food contamination. Therefore, the adsorption of heavy metals in crop soils was taken as the primary research object. Based on the entire reading of the literature, the previous research results were compared and discussed from the four aspects of heterogeneity, physical and chemical properties, competitive adsorption, and external factors. The influencing mechanism of heavy metal adsorption characteristics in soil was reviewed. Finally, suggestions and prospects for future research on heavy metal adsorption were put forward.

Determination of cadmium in Chinese pepper and its health implications based on bioaccessibility.

The contamination of cadmium (Cd) in agro-products causes major concern because of its potential dietary risks. In this study, a total of 647 pepper samples from 21 provinces in China were randomly collected according to the distribution of pepper production. Cd pollution levels in Chinses pepper and its health risks were evaluated based on bioaccessibility, which was measured by the physiologically based extraction test (PBET). The results showed that Cd concentration in all pepper ranged from 0.002 to 1.470mg/kg, with an average of 0.222mg/kg and a median of 0.132mg/kg. The highest daily intake of Cd was observed in the female child group (4.037 × 10-5mg/kg bw/day), which accounted for 4% of the maximum daily permissible dose - 0.001mg/kg bw/day. The target hazard quotients of Cd were all lower than 1, indicating low potential non-carcinogenic health risks to residents via the consumption of pepper. Notably, carcinogenic risk values suggested potential adverse health effects to adults, while after considering the bioaccessibility of Cd in pepper (mean of 43.07%), those values had fallen under the acceptable level (1 × 10-4). This may indicate that dietary risk assessment of heavy metals in crops could not be conducted just based on their content; the bioaccessibility of metals is also an important factor for consideration.

Comprehensive assessment of heavy metals in soil-crop system based on PMF and evolutionary game theory

The traditional assessment of farmland environmental quality usually focuses on soil heavy metals, but ignores agricultural produce safety. It is urgent to comprehensively assess the effects of farmland environmental quality based on soil quality and produce safety. To fill this gap, the comprehensive assessment method was improved based on previous studies, which was used to assess the pollution level of heavy metals in soil-crop system of Shenyang, Liaoning Province, Northeast China. In addition, this study also made a comprehensive analysis of pollution sources based on positive matrix factorization (PMF) model, and discussed soil-crop system income stability by evolutionary game theory. The mean concentrations of As, Cd, Cr, Hg, Pb, Cu, Zn, and Ni in soil exceeded the corresponding Shenyang soil background values (5.68 %, 14.36 %, 57.61 %, 7.86 %, 30.32 %, 5.21 %, 211.72 %, 171.88 %). The results showed that about 28.28 % of paired soil-crop points were polluted by heavy metals, especially rice-soil points. Furthermore, heavy metals in crops may be transmitted less from soil and more from other environmental media. The PMF analysis results showed that there were six pollution sources in study area, and the major contributor of pollution were agricultural activities, traffic-related activities, and industrial activities. In farmland environment protection, the only stable strategy is soil-crop system, and soil-crop system is better than the benefits of single soil or crop from the perspective of benefits. This study provides a scientific and reliable method to combine soil quality with produce safety to assess the risk of heavy metals in farmland.

Antagonistic effect of polystyrene nanoplastics on cadmium toxicity to maize (Zea mays L.)

Nanoplastics (NPs) (<1 μm) have gradually attracted worldwide attention owing to their widespread occurrence, distribution, and ecosystem risks. Few studies have explored the interaction between NPs and heavy metals in crops. In this study, we investigated the influence of polystyrene nanoplastics (PSNPs; 10 mg/L and 100 mg/L) and cadmium (2 mg/L and 10 mg/L) on the physiological and biochemical indices of maize plants, grown in Hoagland solution with contaminants, for 14 days. The fresh weight and growth of the maize plants were significantly reduced after exposure to high concentrations of PSNPs and Cd (p < 0.05). Specifically, the fresh weight decreased by 30.3% and 32.5% in the PSNPs and Cd treatment, respectively. Root length and shoot length decreased by 11.7% and 20.0%, and by 16.3% and 27.8%, in the PSNPs and Cd treatment, respectively. However, there were no significant effects on the fresh weight and growth of maize plants as Cd levels increased from 2 to 10 mg/L in the presence of PSNPs. Polystyrene nanoplastics alleviated the phytotoxicity of Cd in maize. Scanning electron microscopy (SEM) showed that PSNPs and Cd could enter maize roots and were transported upwards to the leaves through the vascular bundle. The activities of peroxidase (POD) and catalase (CAT) in maize leaves increased significantly under high concentrations of PSNPs, whereas superoxide dismutase (SOD) activity decreased (p < 0.05). The differences in SOD activity may be related to the absence of microelements such as Zn, Fe, and Mn. This study provides a scientific basis for further exploration of the combined toxicological effects of heavy metals and NPs on the environment.

Responses of Cd Accumulation in Rice and Spectral Characteristics of Soil Dissolved Organic Matter Regulated by Soil Amendments

Studying the chemical composition and characteristic differences of soil dissolved organic matter (DOM) is significant for understanding the mechanism of Cd immobilization by soil amendments. Soil amendments have been widely applied to contaminated farmlands to reduce the accumulation of heavy metals in crops, but the spectral characteristics of DOM in soils under amendment regulation have rarely been studied. Typical Cd-contaminated paddy soil from South China was collected, three categories of amendments (organic-based, inorganic-based, and lime-based, a total of 11 types) were applied, rice planting pot trials were done, and the effects of different amendments on soil DOM were investigated. The spectral characteristics of rhizosphere soil DOM under the regulation of different amendments were comparatively analyzed using UV-Vis spectroscopy, 3D fluorescence spectroscopy, and parallel factor analysis (PARAFAC). The results showed that the lime-based amendments increased the soil pH and promoted the dissolution of organic matter from the soil solid phase, resulting in a significant increase in soil DOM content. Compared with that of the control, organic-based amendments increased the relative molecular weight and recent autochthonous origin contribution of soil DOM, inorganic-based amendments increased the aromatic content and hydrophobic components of soil DOM, and lime-based amendments increased the chromogenic components and the degree of humification of soil DOM. Four fluorescence components, C1 (255/465), C2 (325/400), C3 (275/390), and C4 (240/460), were identified using PARAFAC and verified with the OpenFluor database, all of which were humic-like. Two types of spectra corroborated with each other, indicating that soil DOM dominated by humus-like matter originated from terrestrial source input. The correlation analysis showed that the fluorescent component C4 of soil DOM could be used to predict Cd accumulation in brown rice in the red limestone soil-rice system. These results will provide a reference for the selection of the appropriate soil amendments.

Concentrations and human health risk assessment of selected heavy metals in soils and food crops around Osukuru phosphate mine, Tororo District, Uganda

This study investigated the concentrations of heavy metals, particularly chromium (Cr), cadmium (Cd); lead (Pb), copper (Cu), and iron (Fe) in the soil and crops. The accumulation of heavy metals in the crop system, the probable daily intake of heavy metals, and the assessment of potential health threats associated with the uptake of metals by the residents around the Osukuru phosphate mine in Tororo, Uganda. The concentrations were assessed with the assistance of an Atomic Absorption Spectrometer (AAS). The crops studied were amaranthus (Amaranthus hybridus) leaves, pumpkin (Cucurbita pepo) leaves, maize (Zea mays) grains, and cowpeas (Vigna unguiculata) leaves. A total of 200 samples were collected from five villages of Osukuru Sub County. The findings of this study showed that elemental concentrations of heavy metals in the soil were within the standard recognized limit for agriculture as documented by World Health Organization (WHO) and European Union (EU). While more noticeable levels of these elements were detected in crop samples, especially amaranthus. Chromium composition was lower than the detection level in all samples. The transfer factor results showed elemental intake by the crops in the sequence; Fe > Cu > Cd > Pb. The probable daily intakes of the elements were below the daily threshold values endorsed by WHO/FAO. The health threat index showed high values for Pb and Cd from maize but low values of Cu and Fe in all samples and therefore these crops may not be very safe for human intake.

Heavy Metal Characteristics and Comprehensive Quality Index Evaluation of Soil-Crop System in 11 Cities of Yunnan Province, China

Yunnan province in China is a high background area of soil heavy metals, and agricultural planting and industrial and mining activities are relatively frequent, which aggravate soil heavy metal pollution. However, at present, there are few reports on the overall or large-scale soil-crop pollution and risk assessment of heavy metals in Yunnan Province. This study through 11 cities in Yunnan province of China farmland soil-crop systems of heavy metal lead, cadmium content, enrichment coefficient is analyzed, and using the method of potential ecological harm index, index of compressive quality to evaluate heavy metal pollution soil-crop system risk. Results showed that the average content of soil heavy metal Cd and Pb were 1.31 mg/kg, 64.17 mg/kg, which are higher than the background value of Yunnan province. The average contents of Pb and Cd in the edible parts of crops were 0.20 mg/kg, 0.08 mg/kg. The average content of heavy metals in crops in Diqing (Pb) and Nujiang (Cd) was 0.72 mg/kg and 0.148 mg/kg. The enrichment coefficients of heavy metals in edible parts of crops were the largest in Diqing (Pb) and Zhaotong (Cd). The average value of ecological risk index of Pb element in soil is 2.79, which indicates that the study area is in a slight ecological hazard, the average value of the ecological risk index of Cd in soil is 126.43. The average value of the comprehensive quality impact index (IICQ) is 4.27, which indicates that the study area is moderately polluted. In this study, the contents of heavy metals Cd and Pb in soils and crops in different administrative regions were determined, and the heavy metals Pb and Cd in soil-crop system of Yunnan province, China were evaluated, it is expected to have important scientific and theoretical significance for the safe use of cultivated land to export safe agricultural products and promote the sustainable development of agriculture in Yunnan Plateau.

Health Risks Assessment of Heavy Metal Pollution in the Soil-Crop System from an E-Waste Dismantling Area

Soil is an essential resource for agricultural production. In order to investigate the pollution situation of heavy metals in the soil-crop system in the e-waste dismantling area, the crop and soil samples (226 pairs, including leaf vegetables, solanaceous vegetables, root vegetables, and fruits) around the e-waste dismantling area in southeastern Zhejiang Province were collected. The concentrations of Cd, Cu, Pb, and Cr were determined. The average concentrations of Cd, Cu, Pb, and Cr in soils were 0.94, 107.79, 80.28, and 78.14 mg kg-1, respectively, and their corresponding concentrations in crops were 0.024, 0.7, 0.041, and 0.06 mg kg-1, respectively. The transfer capacity of leaf vegetables was significantly higher than that of non-leaf vegetables, and the accumulation of four heavy metals in crops tended to be Cd > Cu > Cr/Pb. The pollution index’s results revealed that the soil pollution degree under different land uses ranked as root vegetables soil > leaf vegetables soil > solanaceous vegetables soil > fruit soil. The carcinogenic and non-carcinogenic risks of heavy metal exposure were ranked as food intake > accidental ingestion > dermal contact > inhalation. The comprehensive non-carcinogenic risk was ranked as Cr > Cd > Pb/Cu. Our results could be used to provide useful information for further crop cultivation layout in the study area, which can guarantee the local residents’ health and food safety.

Assessment of health risks from consumption of food crops fumigated with metal based pesticides in Gwadam, Gombe State, Nigeria

Intensive use of agrochemicals has led to build of heavy metals in the soil ecosystem and their transfer to edible parts of crops. This study was aimed to determine the heavy metals (Cd, Pb, Cr, Cu and Zn) concentrations in some twenty commonly used pesticides in northern Nigeria, and health risk associated from the consumption of food crops fumigated with these pesticides as the only source of metal contamination. Heavy metals content in pesticides, food crops and soils were analyzed after acid digestion using atomic absorption spectrometry. Traces of heavy metals (Cd, Pb, Cr, Cu and Zn) were detected in most of the pesticides. The concentrations of heavy metals in crops fumigated with pesticides ranged from 0.33-4.68, 1.75-38.08, 0.67-16.83, 9.01-436.75, 0.17-20.80mg/kg for Cd, Pb, Cr, Cu, and Zn respectively. The mean concentrations of Cd, Pb, and Cr in all the crops were above WHO, (2019) permissible limit. Heavy metals in soils of corresponding crops were below the permissible limits by UNEP, (2013) and NESREA, (2011). Bioaccumulation factor BAF showed high BAF&gt;1 for Cu and Pb in all the studied crops,while pollution index value revealed contamination for Cd and Pb in all the studied crops. Hazard quotient showed potential health risk from the consumption of only Capsicumannuum for Pb. However, consumers may experience advance health risk through the consumption of Oryza sativa, Zea mays, Solanumlycopersicum, Capsicumfrustescens for all metals (Hazard index). Hence, there is the need for screening of heavy metals in pesticides and monitoring of metals contents in food crops.

Visualization of heavy metal cadmium in lettuce leaves based on wavelet support vector machine regression model and visible‐near infrared hyperspectral imaging

AbstractIn order to effectively detect the distribution of Cd in lettuce leaves, this article proposes a wavelet support vector machine regression (WSVR) modeling method and uses it in the prediction of cadmium (Cd) content in lettuce leaves. In addition, this article also observed the internal and external tissue structure of lettuce leaves under different concentrations of Cd stress by scanning electron microscopy and transmission electron microscopy. Moreover, the lettuce leaf samples under different Cd concentration stresses were acquired by the hyperspectral imaging system, different preprocessing algorithms combined with dimensionality reduction algorithms were used to select the spectral characteristic wavelengths, and SVR and WSVR models were established based on the spectral characteristic data. The results showed that with the increase of Cd concentration, the internal and external tissue structure of lettuce leaves changed significantly. The WSVR model parameters for the best prediction of Cd concentration in lettuce were Rp2 of 0.8843, RMSEP of 0.1292 mg/kg. Finally, the Cd contents in lettuce leaves were visualized on the prediction maps by predicted spectral features on each hyperspectral image pixel.Practical ApplicationsIt is of great significance to realize the visual expression of the distribution of heavy metals in crop leaves through nondestructive testing. In order to demonstrate the feasibility of Vis‐NIR hyperspectral imaging technology for the detection of cadmium (Cd) content in lettuce leaves, scanning electron microscopy and transmission electron microscopy were used to observe the internal and external tissue structure of lettuce leaves under different concentrations of Cd. Wavelet support vector machine regression modeling method was proposed and used to predict the Cd content in lettuce leaves. It is proved that the Vis‐NIR hyperspectral imaging technology is a feasible and effective method to realize the visualization of Cd content distribution in crop leaves.

Predictive model for cadmium uptake by maize and rice grains on the basis of bioconcentration factor and the diffusive gradients in thin-films technique

It is possible for heavy metals in soils to be adsorbed by crop roots and then accumulated in crops, which eventually causes great health risk when the crops are ingested by humans. Thus, it is valuable to understand the enrichment model of heavy metals in crops. Diffusive gradients in thin-films (DGT) technique, as an in-situ passive sampling method, can be used to evaluate the bioavailable heavy metals contents in soils. In this study, data of the bioavailable cadmium (Cd) in soils determined by DGT and Cd contents uptake in rice and maize grains in Tianjin, Zhejiang and Guangxi provinces of China were collected from previous references in Web of Science. By comparing bioconcentration factors, it was found that the heavy metal concentrations accumulated in rice and maize followed a general order roots > stems or leaves > grains. An accurate and robust model for the prediction of Cd content in maize and rice grains was established based on bioconcentration factor (BCF) and the bioavailable Cd content determined by DGT method, with R2 0.986 and root mean square error (RMSE) 0.128. This result suggests that the DGT method can be good tool for predicting heavy metals uptake in crops.