1Institute of Quality Safety and Standards of Agricultural Products, Jiangxi Academy of Agricultural Sciences, Nanchang, China;
2Key Laboratory of Quality and Safety of Agricultural Products of Jiangxi Province, Nanchang, China;
3Institute of Animal Husbandry and Veterinary Medicine, Jiangxi Academy of Agricultural Sciences, Nanchang, China
*Corresponding Author: Yaomin Zhou, Institute of Quality Safety and Standards of Agricultural Products, Jiangxi Academy of Agricultural Sciences, Nanchang, China; Key Laboratory of Quality and Safety of Agricultural Products of Jiangxi Province, Nanchang, China. Email: zhouyaomin666@163.com
The degree of pollution and potential ecological risk of heavy metals (HMs) in the soil of plastic-covered sheds in Jiangxi Province were evaluated by the Nemerow index and potential ecological risk index. The bioconcentration factor and total target hazard quotient (TTHQ) were used to evaluate the enrichment ability and health risk of HMs in vegetables. The mean contents of arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg) and lead (Pb) in soil were 5.99, 0.373, 17.8, 5.94E-02, and 28.9 mg kg–1, respectively; Cd exceeded the background value and the maximum limit. Most soils had no extremely strong ecological risk. The concentration of Pb in root vegetables was 0.204 mg kg-1, with the highest concentration of Cd (0.147 mg kg–1) in Ganzhou leafy vegetables. The Hg concentration of leafy vegetables in Jiujiang was 1.41E-02 mg kg–1, which exceeded the maximum limit. The bioconcentration factor of HMs was negatively correlated with pH (P ≤ 0.05). The migration ability of Cd in root vegetables was 1.7-fold to that of leafy vegetables, and was strongest. The TTHQ of all vegetables was less than 1.0, which indicated that there was no significant noncarcinogenic risk in adults. The TTHQ of root vegetables was highest, with Pb in vegetables being major health risk factors. In conclusion, fruit and solanaceous vegetables may be more suitable for planting in plastic-covered shed than root and leafy vegetables; Cd and Pb were identified as the priority control metals under plastic-covered sheds in Jiangxi Province.
Key words: plastic-covered shed, red soil, vegetable, heavy metal accumulation, evaluation
Received: 15 October 2022; Accepted: 11 May 2023; Published: 1 July 2023
© 2023 Codon Publications
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0). License (http://creativecommons.org/licenses/by-nc-sa/4.0/)
Vegetables are rich in nutrients and are one of the main sources of food for humans (Wang et al., 2022). Heavy metals (HMs) in vegetables can accumulate in the body through food, which leads to diseased attributes. HMs do not degrade naturally; therefore, they accumulate in the soil and may cause potential risks (Tariq et al., 2019). In recent years, HM pollution of agricultural products has increased rapidly due to human activities and related factors (Wang et al., 2021; Wen et al., 2020). Researchers are seriously concerned about HM pollution in the soil and vegetables. HM pollution in vegetables has been frequently reported globally, with arsenic (As), cadmium (Cd), chromium (Cr) and lead (Pb) often exceeding maximum limits. A high content of HMs in the soil and vegetables is a possible threat to human health (Tariq, 2021). Mercury (Hg), Cd, Pb, Cr and copper (Cu) have led to pollution in vegetables, HMs in vegetables exceed the critical levels, and there are obvious health risks (Cheshmazar et al., 2018; Gupta et al., 2021; Hossain et al., 2021; Ji et al., 2018; Liu et al., 2021; Quispe, 2021; Tomno et al., 2020). Cd is a ubiquitous and predominant pollutant in vegetables, and vegetable intake health risks are unacceptable (Su et al., 2023). Vegetables pose a noncarcinogenic health risk because of HMs (Sadee and Rasul, 2022).
China’s vegetable production and consumption is huge, and plastic-covered sheds have developed rapidly in south China. Although plastic-covered sheds can increase vegetable supply, they can cause the risk of environmental pollution. Plastic is composed of various types of polymers (Yuan et al., 2022). These are hard to degrade and can form particles by physical and biological processes (O’Kelly et al., 2021). They are carriers for organic pollutants and HMs (Bhagat et al., 2021). They affect the biophysical properties of the soil (Yang et al., 2021) and harm soil organisms, and animal growth, development, and reproduction. HMs and plastics in the soil negatively affect soil quality and show synergistic or antagonistic effects (Kumar, et al., 2022). At the same time, multiple cropping and excess chemical fertilization have led to pollution problems (Chen et al., 2021; Huang et al., 2018; Kianpoor Kalkhajeh et al., 2020), and HM pollution in the soil and vegetables is very serious in China (Hu et al., 2017). Concentrations of Cd and Pb being 72.4% and 35.5%, respectively, in the soil samples have exceeded maximum limits in northern China (Fan et al., 2017). Cd, Cu and zinc (Zn) were more than background values in Hebei Province, northern China (Meng et al., 2021). Cd content in some soil samples was more than the limits, with the maximum values being 3.77-fold higher than the limits in northwest China (Chen et al., 2021). Cr and Pb exceeded 1.86–2.63-fold higher than the limits of Chinese and World Health Organization (WHO)/Food and Agriculture Organization (FAO) in southwest China (Wang et al., 2022). Liu et al. (2021) studied the accumulation of eight HMs in plastic-covered shed soils and vegetables across Chinese provinces (except Jiangxi Province) and confirmed that HM accumulation is a serious question. Soil acidity in plastic-covered sheds is significant (Bai et al., 2020), and acidic soil promotes the enrichment of HMs (Meng et al., 2021).
A large number of studies have been carried out on HM pollution in the soil and vegetables. Fan et al. (2017) used the bioconcentration factor (BCF) and total target hazard quotient (TTHQ) to evaluate HM pollution in greenhouse vegetables in north China and found that the transport coefficients of As, Cr and Pb were higher in leafy and fruit vegetables than in tuber vegetables. The accumulation of HMs under greenhouse conditions could cause risk to human health through fruit and leafy vegetables. Sawut et al. (2018) used the Nemerow integrated pollution index to evaluate HM pollution in greenhouse soil in northwest China and used the TTHQ to evaluate the noncarcinogenic risk assessment of vegetables. The results showed that Cd and Hg were the primary pollutants, and the noncarcinogenic risk for adults was low. By collecting data, Meng et al. (2021) evaluated the soil and vegetables in Chinese greenhouses using transfer factor and target hazard quotient (THQ), and found that the relatively high transfer factor and hazard index values of Cd in spinach should be considered. Gupta et al. (2019) evaluated BCF and health risk of the soil and vegetables in northern India. The results showed that HM transport coefficient of leafy vegetable was higher than fruit vegetable, the TTHQ for Pb, manganese (MN), and Cd was more than 1 because of the consumption of fenugreek and spinach, and the THQ for all investigated metals was less than unity because of the consumption of eggplant and chilli. Jalali and Meyari (2022) evaluated the transfer factor and health risk of soil and vegetables in west Iran. The transfer factor values of the studied HMs were ordered based on the mean values: Cd > Zn > Pb > Cu > Mn > nickel (Ni) > iron (Fe), and the health risk index (RI) values for adults were less than 1, except for Cd and Pb. Birghila et al. (2023) evaluated the transfer factor and health risk of the soil and tomato in southeastern Romania. The BCF was less than 1, indicating that tomato did not accumulate HMs. The THQ and hazard index value were below the acceptable level. Laboni et al. (2023) evaluated vegetables grown in the industrial areas of Bangladesh, and found THQ < 1.0, indicating that it had no noncarcinogenic risk. The soil–vegetable system of historical wastewater irrigation in Kaifeng City, central China, was evaluated by the Nemerow integrated pollution index, BCF and heath risk assessment. The Nemerow pollution index of Cd was highest, and most soil samples were slightly or moderately polluted by HMs. The transfer factor of Cd was highest, and risk assessment revealed that local vegetable consumers suffered health risks (Ruan et al., 2023). Many studies evaluated the soil pollution status by using the geoaccumulation index (Liu et al. 2021; Meng et al. 2021; Su et al. 2023). It is a quantitative indicator to study HMs in the sediments of water environments based on the relationship between total concentration of HMs and background value.
With increasing awareness of human health, increasing attention has been given to HM pollution of plastic-covered shed vegetables. Thus, to protect the dietary safety and health of residents, it is essential to study the accumulation and potential risk of HMs in the soil and vegetables under plastic-covered sheds.
Jiangxi is located in southeastern China and is a typical red soil area. Owing to climate differences, hothouses are mainly plastic-covered sheds, and red soil is characterized by strong acidity and biological enrichment. No relevant studies have been reported about the soil and vegetables under plastic-covered sheds in Jiangxi. To provide a reference for the development of plastic-covered shed vegetables in Jiangxi Province and ensure vegetable consumption security, the pollution index, health risk, and probabilistic risk assessment were investigated.
The aims of this research were as follows: (1) to determine the content of HMs (Cd, Pb, Cr, As, Hg) in the soil and vegetables, evaluate the soil pollution degree by the Nemerow index and potential ecological RI, and study the HM safety status of planting soil; (2) to investigate the HM enrichment capacity of vegetables by BCF to explore differences in HM accumulation in different vegetables. We explored the relationship between pH in red soil and HM accumulation in vegetables under plastic-covered sheds to study the effect of red soil on HMs in vegetables; (3) we estimated the health risk of plastic-covered shed vegetables in adults and confirmed the safety of plastic-covered shed vegetables for consumption. This work would be useful for providing supervision and management for plastic-covered shed vegetable production and decreasing human health risks.
Jiangxi Province is located in southeastern China, bounded between 113°34’36”–118°28’58” E and 24°29’14”–30°04’ 41” N. In recent years, Jiangxi has made great efforts to speed up the development of vegetable bases and has become the main production base for vegetables in China’s southeast coastal region. The study area included parts of Jiujiang city, Shangrao city, Fuzhou city, Yichun city and Ganzhou city in Jiangxi Province (Figure 1). Jiujiang is located in northern, Shangrao city in northeastern, Fuzhou city in western, and Ganzhou city in southern Jiangxi Province.
Figure 1. Distribution of sampling locations in the study areas.
In all, 52 soil (surface 0–20 cm) and 119 vegetable samples were collected from plastic-covered sheds in mentioned five cities of Jiangxi Province. The sample quantity distribution is shown in Tables 1 and 2. A representative sample was collected from each site with five soil and vegetable subsamples.
Table 1. Soil properties, concentrations of HMs and background values in various regions.
HMs | As (mg kg–1) | Cd (mg kg–1) | Cr (mg kg–1) | Hg (mg kg–1) | Pb (mg kg–1) | pH |
---|---|---|---|---|---|---|
Jiujiang city | ||||||
Mean (n = 10) | 7.03 | 0.502 | 17.0 | 3.01E-02 | 45.3 | 6.33 |
Range | 2.19–11.1 | 8.93E-02–2.73 | 8.44–27.4 | 2.03E-03–758E-02 | 12.4–161 | 4.30–6.85 |
Standard deviation | 2.56 | 0.790 | 5.63 | 2.71E-02 | 46.5 | 0.83 |
Coefficient of variation (CV), % | 36.0 | 158 | 33.0 | 91.0 | 103 | 13.2 |
Shangrao city | ||||||
Mean (n = 15) | 6.56 | 0.221 | 15.0 | 0.0480 | 24.7 | 6.33 |
Range | 2.90–14.6 | 4.21E-02–0.537 | 7.93–21.7 | 1.46E-03–0.191 | 14.2–38.7 | 4.43–7.27 |
Standard deviation | 2.98 | 0.124 | 4.62 | 0.0631 | 8.56 | 0.91 |
Coefficient of variation (CV), % | 45.1 | 56.2 | 31.0 | 191.0 | 35.3 | 14.4 |
Fuzhou city | ||||||
Mean (n = 10) | 3.43 | 0.173 | 15.9 | 0.0912 | 27.9 | 6.33 |
Range | 2.10–4.93 | 4.58E-02–0.392 | 9.54–26.5 | 2.11E-03–0.351 | 16.0–48.6 | 4.63–6.28 |
Standard deviation | 1.00 | 0.114 | 4.67 | 0.121 | 9.43 | 0.64 |
Coefficient of variation (CV), % | 29.4 | 66.2 | 28.9 | 133 | 33.7 | 10.1 |
Yichun city | ||||||
Mean (n = 11) | 7.65 | 0.299 | 26.7 | 0.0392 | 21.4 | 6.33 |
Range | 2.93–13.1 | 3.59E-02–0.719 | 20.2–32.1 | 2.13E-03–0.120 | 15.8–27.1 | 5.17–6.87 |
Standard deviation | 2.95 | 0.220 | 3.82 | 4.73E-02 | 3.71 | 0.58 |
Coefficient of variation (CV), % | 38.7 | 73.2 | 14.3 | 120 | 17.4 | 9.10 |
Ganzhou city | ||||||
Mean (n = 9) | 4.07 | 0.178 | 12.8 | 0.116 | 27.2 | 6.33 |
Range | 3.00–6.45 | 8.17E-02–0.282 | 8.10–22.7 | 3.17E-03–0.276 | 20.3–37.7 | 4.75–6.62 |
Standard deviation | 1.32 | 8.67E-02 | 5.55 | 0.114 | 6.45 | 0.72 |
Coefficient of variation (CV), % | 32.4 | 48.6 | 43.2 | 97.6 | 24.5 | 11.4 |
Jiangxi province | ||||||
Mean | 5.99 | 0.373 | 17.8 | 5.94E-02 | 28.9 | 6.33 |
Range | 2.10–14.6 | 3.63E-02–1.73 | 7.93–32.1 | 6.28E-03–0.276 | 12.4–160 | 4.30–7.27 |
Standard deviation | 2.88 | 0.254 | 6.64 | 7.33E-02 | 22.2 | 0.762 |
Coefficient of variation (CV), % | 47.9 | 98.7 | 37.1 | 130 | 77.0 | 12.0 |
Limit level | 30 | 0.3 | 150 | 0.25 | 50 | |
Background values | 10.4 | 0.1 | 48.0 | 0.08 | 32.1 |
Table 2. Analysis results of heavy metal contents in various vegetables (mg kg–1).
Vegetable type | As | Cd | Cr | Hg | Pb | |
---|---|---|---|---|---|---|
Leafy vegetables | Mean (n = 39) | 2.74E-02 | 4.73E-02 | 0.177 | 1.46E-03 | 0.122 |
Range | 2.08E-03–0.126 | 4.06E-03–0.186 | 2.02E-02–1.36 | 3.05E-06–0.004 | 0.018–0.431 | |
Mean of Jiujiang | 3.72E-02 | 4.84E-02 | 0.216 | 1.41E-02 | 6.68E-02 | |
Mean of Shangrao | 2.49E-02 | 3.32E-02 | 0.264 | 1.37E-03 | 8.83E-02 | |
Mean of Fuzhou | 1.01E-02 | 3.43E-02 | 4.69E-02 | 1.28E-03 | 4.41E-02 | |
Mean of Yichun | 1.63E-02 | 5.10E-02 | 7.86E-02 | 5.63E-04 | 0.156 | |
Mean of Ganzhou | 9.22E-02 | 0.147 | 0.227 | 4.38E-03 | 0.296 | |
Fruit vegetables | Mean (n = 33) | 4.87E-03 | 8.61 E-03 | 4.77E-02 | 1.04E-04 | 5.11E-02 |
Range | 3.01 E-05–1.65E-02 | 6.85 E-04–3.88E-02 | 9.26 E-03–0.391 | 3.03 E-06–8.02 E-04 | 9.22 E-03–0.152 | |
Mean of Jiujiang | 5.27E-03 | 6.47E-03 | 1.33E-02 | 6.23E-02 | 0.115 | |
Mean of Shangrao | 4.36E-03 | 6.18E-03 | 7.64E-02 | 1.03E-04 | 4.87E-02 | |
Mean of Fuzhou | 5.11E-03 | 4.25E-03 | 2.09E-02 | 1.21E-04 | 2.91E-02 | |
Mean of Yichun | 7.04E-03 | 2.87E-02 | 5.01E-02 | 3.05E-06 | 0.101 | |
Mean of Ganzhou | 6.25E-03 | 1.61E-02 | 6.48E-02 | 1.52E-04 | 7.73E-02 | |
Solanaceo-us vegetables | Mean (n = 22) | 6.64 E-03 | 2.53E-02 | 7.41E-02 | 9.05E-05 | 0.183 |
Range | 8.93 E-04–3.79E-02 | 4.65 E-03–6.73E-02 | 8.94 E-03–0.286 | 3.02 E-06–2.94 E-04 | 7.48E-03–2.45 | |
Mean of Jiujiang | 8.17E-03 | 3.33E-02 | 2.80E-02 | 2.03E-04 | 3.66E-02 | |
Mean of Shangrao | 4.46E-03 | 2.01E-02 | 0.132 | 8.26E-05 | 8.48E-02 | |
Mean of Fuzhou | 2.25E-03 | 1.32E-02 | 2.41E-02 | 3.65E-5 | 2.21E-02 | |
Mean of Yichun | 1.32E-02 | 3.07E-02 | 8.84E-02 | 6.71E-5 | 0.106 | |
Mean of Ganzhou | 9.05E-03 | 3.61E-02 | 5.03E-02 | 6.34E-5 | 0.425 | |
Root vegetables | Mean (n = 5) | 1.61E-02 | 3.94E-02 | 0.133 | 1.32E-03 | 0.204 |
Range | 1.80 E-03–5.70E-02 |
3.85 E-03–9.65E-02 |
2.51 E-02–0.340 |
3.04 E-05–6.10 E-03 |
2.91 E-02–0.330 | |
Mean of Jiujiang | - | - | - | - | - | |
Mean of Shangrao | 3.06E-03 | 8.05E-03 | 0.183 | 1.12E-04 | 5.85E-02 | |
Mean of Fuzhou | - | - | - | - | - | |
Mean of Yichun | 3.24E-02 | 8.32E-02 | 0.119 | 3.05E-03 | 0.287 | |
Mean of Ganzhou | 1.19E-02 | 1.44E-02 | 6.17E-02 | 1.22E-04 | 0.330 | |
Limit levels | 0.5 | 0.05 (leafy vegetables 0.2; root vegetable 0.1) | 0.5 | 0.01 | 0.1 (leafy vegetables 0.3) |
Soil samples were dried at room temperature, finely ground, and passed through a 10-mesh sieve. A portion of soil that was passed through a 100-mesh sieve was used to determine the concentrations of HMs. Distilled water was used to wash vegetable samples, and vegetable samples were dried at room temperature. To determine the concentrations of HMs, samples (0.1 g) were digested with microwave digestion apparatus (CEM mars6, USA), soil samples were digested with HNO3-H2O2-HF (guaranteed reagent [GR]), and vegetable samples were digested with HNO3-H2O2 (GR) (Chen et al., 2021; Wang et al., 2022). Temperature rise program: 120°C, kept for 3 min, 150°C, kept for 3 min, 190°C, kept for 30 min, and heating at 105°C until the remaining 1 mL. The concentration of HMs was determined by ICP–MS (NexION2000, PerkinElmer, USA). The operating parameters of ICP-MS were as follows: argon as a carrier gas, methane as a reaction gas (purity >99.999%), flow rate of 0.1–1.0 mL/min, step length of 0.1 mL/min, RPq value of 0.45–0.80, RF power 400–1,600 W, lens voltage 6.25 V, analog stage voltage -3,000 V, and pulse stage voltage 2,500 V. Dynamic reaction cell (DRC) operating parameters were as follows: mode CPV-21V, mode QRO-6.5V, and mode CRO-1V. The soil pH was determined at a soil–water ratio of 1:2.5 using a pH meter (s470k, Mettler Toledo, China). Quality control was ensured with the use of reagent blanks and certified reference materials (GBW07405 [GSS-5]) for soil, spinach (GBW10015 [GSB-6] for vegetables), and certified reference materials produced by the Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences. Each sample was determined from three replicates of parallel experiments, and the mean value was the final determination.
Evaluation of the soil was carried out according to the evaluation parameters and calculation methods of the Chinese environmental standard (HJ 333-2006) (China National Environmental Protection Agency [CNEPA], 2006). The pollution index of the soil was calculated using Equations 1 and 2:
where Pi is the single factor index, Cs is the measured value of HM, and Cm is the maximum limit of HJ 333-2006; Pc is the comprehensive pollution index, is the average of the single factor index, and Pmax is the maximum of single factor index. According to HJ 333-2006, both Pi and Pc are classified into three levels: Pc ≤ 0.7 as safe; 0.7 < Pc ≤ 1.0 as clean; 1.0 < Pc ≤ 2.0 as slightly polluted; 2.0 < Pc ≤ 3.0 as moderately polluted; and Pc > 3.0 as heavily polluted (Li et al., 2018).
The potential ecological RI of the soil can reflect the content, sensitivity and toxicity of HMs in the soil environment according to the nature and behavioral characteristics of HMs in the soil. The RI of the soil was calculated as follows:
where Ti is the standard HM toxicity coefficient (Hakanson, 1980), As = 10, Cd = 30, Cr = 2, Hg = 40 and Pb = 5; Cs is the measured value of a HM; Cn is the background value of HM. Referring to Hakanson’s (1980) division criteria for HMs, Ei is the potential ecological RI of a single HM, Ei ≤ 40 indicates a slight ecological risk, 40 < Ei ≤ 80 indicates a moderate ecological risk, 80 < Ei ≤ 160 indicates a strong ecological risk, 160 < Ei ≤ 320 indicates a very strong ecological risk, and Ei > 320 indicates an extremely strong ecological risk. The RI is the sum of the potential ecological risk indices of various HMs, and RI ≤ 150 represents a slight ecological risk, 150 < RI ≤ 300 indicates a moderate ecological risk, 300 < RI ≤ 600 indicates a strong ecological risk, and RI > 600 indicates an extremely strong ecological risk (Gong et al., 2016; Wei et al., 2023).
The BCF is used to describe the transfer or mobility of metals from the soil to vegetables (Tariq, 2021; Zunaidi et al., 2023) and was calculated as shown in Equation 5,
where BCF is the bioconcentration factor, RV is the concentration of HMs in the edible part of vegetable, and RS is the concentration of HMs in the soil.
Health risks are measured by calculating chronic daily intake (CDI), THQ and TTHQ for HMs. Equations 6–8 were used to calculate THQ and TTHQ values:
where FIR is the daily vegetable consumption, which is assumed to be 0.345 kg d−1 person−1; EF is the rate of exposure (365 d year−1); and ED is the period of exposure (74.68 years); BW is the mean body weight of an adult (60 kg); TA is the average duration of exposure to HMs, which is assumed to be 365 days year−1×74.68 years (CNEPA, 2013); C is the content of HMs in vegetables; RfD is the reference daily allowed dose of HMs, and the RfDs of As, Cd, Cr, and Hg are 0.0003, 0.001, 1.5, 0.0003 mg kg−1 d−1, respectively (Chen et al., 2021; Sawut et al., 2018). Tolerable daily intake (TDI) is only applied in the THQ formula for Pb (0.0036 mg kg−1 d−1) (Mohammadpour et al., 2022a). TTHQ is the sum of THQs of various HMs. THQ <1 or TTHQ < 1 indicate no severe health risk from HM exposure, while values greater than or equal to 1 suggest adverse health effects of HMs (Chen et al., 2021; Machate, 2023).
SPSS 17.0 was used to process raw data and perform statistical analyses of survey results, such as minimum, maximum, mean, standard deviation, analysis of variance and correlation. Pearson correlation analysis was used to evaluate the relationship. A two-tailed P ≤ 0.05 was considered statistically significant. Oracle Crystal Ball V11 was used to process the Monte Carlo simulation (Mohammadpour et al., 2022a, 2022b). Part of the figure was drawn by OriginPro 8.
The plastic-covered shed soil properties and HM concentrations are shown in Table 1. The respective mean contents of As, Cd, Cr, Hg and Pb in different cities were as follows: Jiujiang city—7.03, 0.502, 17.0, 0.03.1 and 45.3 mg kg-1; Shangrao city—6.56, 0.221, 15.0, 0.0480 and 24.7 mg kg-1; Fuzhou city—3.43, 0.173, 15.9, 0.0912 and 27.9 mg kg-1; Yichun city—7.65, 0.299, 26.7, 0.0392 and 21.4 mg kg-1; and Ganzhou city—4.07, 0.178, 12.8, 0.116 and 27.2 mg kg-1. Based on the data for each of the mentioned cities, the mean contents of As, Cd, Cr, Hg and Pb in Jiangxi Province were 5.99, 0.373, 17.8, 0.0594 and 28.9 mg kg-1, respectively. The average pH of the soil in the five cities was 6.33, which was acidic, and only a few soil samples in Shangrao city were alkaline. The mean concentration of As in the soil of Yichun city was highest, but it was lower than both background value (10.4 mg kg-1) for Jiangxi Province and maximum limit (30 mg kg-1) in the environmental criteria for Chinese greenhouse soil (CNEPA, 2006). The mean Cd concentration in the soil of Jiujiang city was highest, and the mean Cd concentration of all soil samples exceeded both background value (0.1 mg kg-1) and maximum limit (0.3 mg kg-1). This means that Cd pollution is serious. The mean Cr concentration in the soil of Yichun city was highest, but it was lower than both background value and maximum limit. The Hg mean concentration in the soil of Ganzhou city was highest, and it was higher than the background value but lower than the maximum limit. The Pb mean concentration in the soil of Jiujiang city was highest, exceeded the background value but lower than the maximum limit. Among the mean contents of HMs in Jiangxi Province, only Cd and Hg exceeded the background value but only Cd exceeded the maximum limit; other HMs were lower than the background value and maximum limit. The factors influencing accumulation of HM are mainly human activity (such as excessive application of chemical fertilizers, manures and fungicides) and soil properties (Meng et al., 2021; Wang et al., 2022). The mean contents of Cd, As, Hg and Cr were lower than those reported by Liu et al. (2021), while the mean Pb content remained the same. The mean Cd content was higher than that in northwestern China (Chen et al., 2021) and northern China (Meng et al., 2021). Studies conducted by Ji et al. (2018) and Su et al. (2023) reported that Cd was a ubiquitous and predominant pollutant in the soils of southern China, which agreed with the results of this study.
The pollution degree of the soil was evaluated by Equations 1 and 2, as shown in Figures 2 and 3. The respective mean single factor index of As, Cd, Cr, Hg, Pb and synthetic factor index in different cities were as follows: Jiujiang city—0.243, 1.667, 0.109, 0.119, 0.906 and 2.443; Shangrao city—0.224, 0.735, 0.096, 0.185, 0.494 and 0.59; Fuzhou city—0.114, 0.576, 0.106, 0.365, 0.558 and 0.585; Yichun city—0.267, 0.998, 0.166, 0.144, 0.428 and 0.796; and Ganzhou city—0.139, 0.594, 0.083, 0.465, 0.545 and 0.593. Based on the data for each city, the mean single factor index of As Cd Cr Hg Pb and the synthetic factor index in Jiangxi Province were 0.206, 0.859, 0.114, 0.223, 0.578 and 0.988, respectively. The soil single factor indexes of As, Cr, and Hg were less than 0.7 in all cities, which indicated that they were in safe levels. The single factor index of Cd in Jiujiang city was more than 1 but less than 2, which indicated that the soil was slightly polluted. The single factor index of Cd in Yichun and Shangrao cities was more than 0.7 but less than 1, which indicated that the soil was clean, and Cd was in safe levels in Fuzhou and Ganzhou. The single factor index of Pb in Jiujiang city was more than 0.7 but less than 1, which indicated that the soil was clean. The synthetic factor index of the soils in all cities was ranked in the following decreasing order: Jiujiang > Yichun > Ganzhou > Shangrao > Fuzhou. The synthetic factor index of Jiujiang was more than 2 but less than 3, which indicated that the soil in Jiujiang was moderately polluted. The synthetic factor index of soil in Jiangxi Province was more than 0.7 but less than 1, which indicated that the soil was clean. The single factor index of HMs in Jiangxi Province was ranked as Cd > Pb > Hg > As > Cr, and the single factor index of Cd was more than 0.7, which indicated that the soil was clean but polluted with Cd to a certain extent.
Figure 2. Evaluation results of HMs in the soils in different regions based on the Nerome index.
Figure 3. Diagram showing the proportion in the soil sample compared to the regional pollution.
The RI of the soil is presented in Figures 4 and 5. The order of the potential ecological RI for a single HM was Cd > Hg > As > Pb > Cr. The single potential ecological hazardous RI of Hg, As, Cr and Pb was less than 40, which indicated that these HMs were a slight ecological risk. The single potential ecological hazardous RI of Cd was maximum in the soils across all the cities, and a strong ecological risk occurred in Jiujiang and Yichun, and a moderate ecological risk occurred in other cities. We must consider Cd pollution in local soils to ensure that vegetables and fruits are not polluted by it. Figure 5 shows that 75% of the soil samples had a potential ecological RI of less than 150, indicating a slight ecological risk, 21.9% of the soil samples had a potential ecological RI between 150 and 300, indicating a medium ecological risk, and only one soil sample had an extremely strong ecological risk.
Figure 4. Mean of single potential ecological hazard index values for the soil in each region.
Figure 5. Number distribution map of soil samples with different potential risk intensities.
Many studies have confirmed that the contents of As, Cd, Cr and Pb in leafy vegetables are significant higher than those in other vegetables (Liu, 2021; Wang et al., 2022). The HM contents in vegetables are shown in Table 2. The respective mean contents of As, Cd, Cr, Hg and Pb in different types of vegetables are as follows: leafy vegetables—2.74E-02, 4.73E-02, 0.177, 1.46E-03 and 0.122 mg kg-1; fruit vegetables—4.87E-03, 8.61E-03, 4.77E-02, 1.04E-04 and 5.11E-02 mg kg-1; solanaceous vegetables—6.64E-03, 2.53E-02, 7.41E-02, 9.05E-05 and 0.183 mg kg-1; and root vegetables—1.61E-02, 3.94E-02, 0.133, 1.32E-03 and 0.204 mg kg-1. The contents of As Cd and Cr in vegetables followed the following decreasing sequence: leafy vegetables > root vegetables > solanaceous vegetables > fruit vegetables. The content of Hg followed the following decreasing sequence: root vegetables > leafy vegetables > fruit vegetables > solanaceous vegetables, and Pb followed the following decreasing sequence: root vegetables > solanaceous vegetables > leafy vegetables > fruit vegetables. The mean content of As (9.22E-02 mg kg-1) and Cd (0.147 mg kg-1) in Ganzhou leafy vegetables was maximum but less than the maximum limit assigned by the China National Food Safety Standards (Chinese Ministry of Health [CMH], 2017). The mean concentration of Cr in leafy vegetables in Shangrao, Ganzhou and Jiujiang was higher than in other cities and other vegetables but less than the maximum limits of China National Food Safety Standards. The mean concentration of Hg in fruit vegetables (6.23E-02 mg kg-1) and leafy vegetables (1.41E-02 mg kg-1) in Jiujiang was highest, exceeding the maximum limit of China standards. The respective mean concentration of Pb in solanaceous vegetables and root vegetables exceeded by 1.8- and 2.0-fold than the maximum limits of China standards. The mean concentration of Pb (0.425 mg kg-1) in solanaceous vegetables in Ganzhou was highest, with a 4-fold increase than the maximum limit of China.
Liu et al. (2021) reported on the accumulation of HMs in root vegetables, leafy vegetables, and fruit vegetables produced in China plastic greenhouses. Their study showed that the Pb content in root vegetables was higher than that reported by Liu et al. (2021), while the HM content in other vegetables was lower than that reported by Liu et al. (2021). The As content in vegetables was significantly correlated in a positive manner with Cd, Cr and Hg contents (r = 0.411, 0.302, 0.413, respectively; P ≤ 0.01). The higher the accumulation of As in vegetables, the higher the corresponding content of Cd, Cr and Hg, and vice versa. The Cd content in vegetables was significantly correlated in a positive manner with the Hg content (r = 0.584, P ≤ 0.01), that is, the higher the accumulation of Cd, the higher the accumulation of Hg in vegetables. This result demonstrated that HMs had synergistic effects.
The BCF values of HMs in vegetables are shown in Figure 6. The BCF of HMs in different vegetables followed the following decreasing sequences:
Leafy vegetables: Cd (0.166) > Hg (0.1401) > Pb (0.0049) > As (0.0048) > Cr (0.0100); fruit vegetables: Cd (0.0689) > Hg (0.0246) > Cr (0.0035) > Pb (0.0023) > As (0.0011); solanaceous vegetables: Cd (0.1646) > Hg (0.0298) > Pb (0.0078) > Cr (0.0054) > As (0.0013); and root vegetables: Cd (0.2873) > Hg (0.0719) > Pb (0.0075) > Cr (0.0059) > As (0.0016).
Figure 6. BCFs of HMs in variety vegetables.
The BCF of different HMs in vegetables followed the following decreasing sequences:
As: leafy vegetables > root vegetables > solanaceous vegetables > fruit vegetables; Cd: root vegetables > leafy vegetables > solanaceous vegetables > fruit vegetables; Cr: root vegetables > solanaceous vegetables > fruit vegetables > leafy vegetables; Hg: leafy vegetables > root vegetables > solanaceous vegetables > fruit vegetables; and Pb: solanaceous vegetables > root vegetables > leafy vegetables > fruit vegetables.
The migration ability of Cd from the soil to vegetables was strongest, which corroborated the previous research (Chen et al., 2021; Meng et al., 2021) whereas Hg, As and Cr showed weak migration ability. The migration ability of Cd in root vegetables was 1.7-fold of leafy vegetables and solanaceous vegetables. Research conducted by Chen et al. (2021) and Jalali and Meyari (2022) reported that the migration ability of Cd in leafy vegetables was highest, which was different from the results of the present study.
The difference in HM accumulation in different types of vegetables was attributed to the ability of plants in the uptake and transport of HM (Zunaidi et al., 2023). Transpiration and roots play significant roles in HM accumulation in vegetables. Available HMs in the soil are absorbed by the roots; some HMs are retained in the roots, which leads to more accumulation of HMs in root vegetables than in other vegetables. The remaining HMs are transported and accumulated in the aboveground parts of vegetables by transpiration. The strong vegetable enrichment capability leads to accumulation of more HMs and stronger transpiration. Leafy vegetables can accumulate more HMs than other vegetables because of higher translocation and transpiration rates (Chen et al., 2021; Gupta et al., 2021). BCF was negatively correlated with pH (P ≤ 0.05), which indicated that the accumulation capacity of vegetables for HMs did not change significantly with change in pH. This is different from the common belief that with decrease in soil pH, the availability of HMs in the soil can be improved (Liu et al., 2021), leading to an increase in the accumulation of HMs in vegetables.
The THQ and TTHQ values of HMs in vegetables are shown in Figure 7. The THQ of HMs in different vegetables followed the following decreasing sequences:
Leafy vegetables—Cd (0.2689) > Pb (0.1745) > Hg (0.0082) > As (0.0031) > Cr (0.0007); fruit vegetables—Pb (0.0730) > Cd (0.0493) > Hg (0.0008) > As (0.0006) > Cr (0.0002); solanaceous vegetables—Pb (0.2618) > Cd (0.1430) > As (0.0008) > Hg (0.0007) > Cr (0.0003); and root vegetables—Pb (0.2918) > Cd (0.2231) > Hg (0.0106) > As (0.0018) > Cr (0.0005).
Figure 7. THQ and its proportion of different heavy metal in various vegetables.
The respective THQ of different HMs in leafy vegetables, fruit vegetables, solanaceous vegetables and root vegetables accounted for the following values: Cd: 59.06%, 39.80%, 35.18%, 42.27%; Pb: 38.32%, 58.94%, 64.38%, 55.28%. The THQ of Pb in root vegetables was highest, followed by Cd in leafy vegetables, and Cr in all vegetables was lowest. Cd and Pb are major factors for THQs, and local residents should focus on the risks of Pb and Cd when consuming vegetables.
The TTHQ of HMs in vegetables followed the following decreasing sequence: root vegetables > leafy vegetables > solanaceous vegetables > fruit vegetables. The TTHQ of HM in root vegetables was highest, reaching 0.53, and the intake of root vegetables should be controlled in moderation. The TTHQ of all vegetables was less than 1.0, which indicated that there was no significant noncarcinogenic risk to adults.
The 5%, 95% confidence level and mean of THQs are shown in Figure 8 (A, C, E and G) , sensitivity of adults are shown in Figure 8 (B, D, F and H). As shown in Figure 8 (A, C, E and G), the probability estimation proved that TTHQ levels in adults followed the following sequence: root vegetables (mean = 0.53) > leafy vegetables (mean = 0.46) > solanaceous vegetables (mean = 0.41) > fruit vegetables (mean = 0.12). The values of 0.47–0.59, 0.40–0.51, 0.36–0.46 and 0.11–0.14 were observed for the 5th and 95th percentiles in vegetables, respectively. The results proved that TTHQ < 1 for all vegetables, which intends that the probability of noncarcinogenic risks was not enhanced. Figure 8 (B, D, F and H) presents the sensitivity analysis of effective factors in TTHQ. The mean body weight (BW), the average duration of exposure to HMs (TA) and the tolerable daily intake (TDI) had a negative value in sensitivity analysis for adults. It demonstrated that BW, TA and TDI were inversely related to health risks. The period of exposure (ED), the rate of exposure (EF), the daily vegetable consumption (FIR) and concentration of Pb had significant influence (above 10%) on the TTHQ of adults, with other parameters having the lowest (<1%) influence. However, ED, EF and FIR values are fixed, with concentration of Pb being prominent. Therefore, Pb was identified as the priority control metal in Jiangxi plastic-covered sheds. This result was consistent with the results of the China plastic-shed vegetable production area (Meng et al., 2021).
Figure 8. (A) Probability analysis of leafy vegetables TTHQ in adults; (B) sensitivity analysis of leafy vegetables TTHQ in adults; (C) probability analysis of fruit vegetables TTHQ in adults; (D) sensitivity analysis of fruit vegetables TTHQ in adults; (E) probability analysis of solanaceous vegetables TTHQ in adults; (F) sensitivity analysis of solanaceous vegetables TTHQ in adults; (G) probability analysis of root vegetables TTHQ in adults; and (H) sensitivity analysis of root vegetables TTHQ in adults.
The soil and four different vegetables of plastic-covered sheds were collected from the study area, and the degree of HM pollution and the human health risk assessment were analyzed. Cd and Hg in the soil exceeded the local background value, and Cd also exceeded the maximum limit levels of China. Evaluation of the Nerome index showed that the soil of the plastic-covered shed in Jiangxi Province was clean, but some of the soil in the area was moderately polluted by Cd. Evaluation of the potential ecological RI showed that most soils had no extremely strong ecological risk except the soils of Jiujiang and Yichun cities. As the contents of As Cd and Cr were highest in leafy vegetables, and that of Pb and Hg were highest in root vegetables, fruit and solanaceous vegetables could be more suitable for planting in plastic-covered shed than root and leafy vegetables. The results of the health risk assessment and the Monte Carlo simulation showed that Cd and Pb were major factors affecting THQ. The TTHQ of root vegetables was highest, so the intake of root vegetables should be controlled. The contribution of Cd and Pb to THQ was highest among the noncarcinogenic risk contributions of all HMs; therefore, Cd and Pb were identified as the priority control metals in the Jiangxi plastic-covered sheds.
Conceptualization, methodology, investigation, editing, writing and original drafting were done by Genxin Nie. Resources, supervision, writing, reviewing and editing were done by Yaomin Zhou. Analysis and data collection were done by Tianhua Tu. Lifang Hu was responsible for sample collection. Ling Wu did methodology, reviewing and editing. All authors read and agreed to the published version of the manuscript.
This study was financially supported by the Jiangxi Vegetable Industry Technical System (Grant No.: JXARS-06).
This work had received grant from Jiangxi Provincial Department of Agriculture and Rural Affairs, China.
The authors declared that they had no known competing financial interests or personal relationship that could influence the research conducted in this paper.
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Bai, X., Gao, J., Wang, S., Cai, H., Chen, Z. and Zhou, J., 2020. Excessive nutrient balance surpluses in newly built solar greenhouses over five years leads to high nutrient accumulations in soil. Agriculture, Ecosystems & Environment 288: 106717. 10.1016/j.agee.2019.106717
Bhagat, J., Nishimura, N. and Shimada, Y., 2021. Toxicological interactions of microplastics/nanoplastics and environmental contaminants: current knowledge and future perspectives. Journal of Hazardous Materials 405: 123913. 10.1016/j.jhazmat.2020.123913
Birghila, S., Matei, N., Dobrinas, S., Popescu, V., Soceanu, A. and Niculescu, A., 2023. Assessment of heavy metal content in soil and Lycopersicon esculentum (tomato) and their health implications. Biological Trace Element Research 201: 1547–1556. 10.1007/s12011-022-03257-9
Chen, Z., Muhammad, I., Zhang, Y., Hu, W., Lu, Q., Wang, W., et al. 2021. Transfer of heavy metals in fruits and vegetables grown in greenhouse cultivation systems and their health risks in Northwest China. Science of the Total Environment 766: 142663. 10.1016/j.scitotenv.2020.142663
Cheshmazar, E., Arfaeinia, H., Karimyan, K., Sharafi, H. and Hashemi, S.E., 2018. Dataset for effect comparison of irrigation by wastewater and ground water on amount of heavy metals in soil and vegetables: accumulation, transfer factor and health risk assessment. Data in Brief. 18: 1702–1710. 10.1016/j.dib.2018.04.108
Chinese Ministry of Health (CMH), 2017. National standards for food safety limit of contaminants in food. GB2762-2017. CMH, Beijing, China.
China National Environmental Protection Agency (CNEPA), 2006. Environmental quality evaluation standard for farmland of greenhouse vegetables production. HJ333–2006. CNEPAC, Beijing, China.
China National Environmental Protection Agency (CNEPA), 2013. Exposure factors handbook of Chinese population. CNEPAC, Beijing, China.
Fan, Y., Li, H., Xue, Z., Zhang, Q. and Cheng, F., 2017. Accumulation characteristics and potential risk of heavy metals in soil-vegetable system under greenhouse cultivation condition in Northern China. Ecological Engineering 102: 367–373. 10.1016/j.ecoleng.2017.02.032
Gong, M., Zhu, W-Q., Gu, Y-Q., and Li, S-y., 2016. Evaluation on heavy metal pollution and its risk in soils from vegetable bases of Hangzhou. Environmental Science 37(6): 2329–2337. 10.13227/j.hjkx.2016.06.042
Gupta, N., Yadav, K.K., Kumar, V., Krishnan, S., Kumar, S., Nejad, Z.D., et al. 2021. Evaluating heavy metals contamination in soil and vegetables in the region of North India: levels, transfer and potential human health risk analysis. Environmental Toxicology and Pharmacology 82: 103563. 10.1016/j.etap.2020.103563
Gupta, N., Yadav, K.K., Kumar, V., Kumar, S., Chadd, R.P. and Kumar, A., 2019. Trace elements in soil-vegetables interface: Translocation, bioaccumulation, toxicity and amelioration-A review. Science of the Total Environment 651(2): 2927–2942. 10.1016/j.scitotenv.2018.10.047
Hakanson, L., (1980). An ecological risk index for aquatic pollution control. A sedimentological approach.Water Research 14(8): 975–1001. 10.1016/0043-1354(80)90143-8
Hossain, M.M., Chowdhury, M.A., Hasan, M.J., Rashid, M.H-Ar., Acterossain, T., Chowdhury, M.A., et al. 2021. Heavy metal pollution in the soil-vegetable system of Tannery estate. Environmental Nanotechnology, Monitoring & Management 16: 100557. 10.1016/j.enmm.2021.100557
Hu, W., Huang, B., Tian, K., Holm, P.E. and Zhang, Y., 2017. Heavy metals in intensive greenhouse vegetable production systems along Yellow Sea of China: levels, transfer and health risk. Chemosphere 167: 82–90. 10.1016/j.chemosphere.2016.09.122
Huang, Y., Deng, M., Wu, S., Japenga, J., Li, T., Yang, X., et al. 2018. A modified receptor model for source apportionment of heavy metal pollution in soil. Journal of Hazardous Materials 354: 161–169. 10.1016/j.jhazmat.2018.05.006
Jalali, M. and Meyari, A., 2022. Heavy metal contents, soil-to-plant transfer factors, and associated health risks in vegetables grown in western Iran. Journal of Food Composition and Analysis 106: 104316. 10.1016/j.jfca.2021.104316
Ji, Y., Wu, P., Zhang, J., Zhang, J., Zhou, Y., Peng, Y., et al. 2018. Heavy metal accumulation, risk assessment and integrated biomarker responses of local vegetables: a case study along the Le’an river. Chemosphere 199: 361–371. 10.1016/j.chemosphere.2018.02.045
Kianpoor, KY., Huang, B., Hu, W., Ma, C., Gao, H., Thompson, M.L., et al. 2020. Environmental soil quality and vegetable safety under current greenhouse vegetable production management in China. Agriculture, Ecosystems & Environment 307: 107230. 10.1016/j.agee.2020.107230
Kumar, R., Ivy, N., Bhattacharya, S., Dey, A. and Sharma, P., 2022. Coupled effects of microplastics and heavy metals on plants: uptake, bioaccumulation, and environmental health perspectives. Science of the Total Environment 836: 155619. 10.1016/j.scitotenv.2022.155619
Laboni, F.A., Ahmed, M.W., Kaium, A., Alam, M.K., Parven, A., Jubayer, M.F., et al. 2023. Heavy metals in widely consumed vegetables grown in industrial areas of Bangladesh: a potential human health hazard. Biological Trace Element Research 201: 995–1005. 10.1007/s12011-022-03179-6
Li, X., Li, Z., Lin, C.-J., Bi, X., Liu, J., Feng, X., et al. 2018. Health risks of heavy metal exposure through vegetable consumption near a large-scale Pb/Zn smelter in central China. Ecotoxicology and Environmental Safety 161: 99–110. 10.1016/j.ecoenv.2018.05.080
Liu, X., Gu, S., Yang, S., Deng, J. and Xu, J., 2021. Heavy metals in soil-vegetable system around e-waste site and the health risk assessment. Science of the Total Environment 779: 146438. 10.1016/j.scitotenv.2021.146438
Liu, J., Wang, Y., Liu, X., and Xu, J., 2021. Occurrence and health risks of heavy metals in plastic-shed soils and vegetables across China. Agriculture, Ecosystems and Environment 321: 107632. 10.1016/j.agee.2021.107632
Machate, D.J., 2023. Anthropogenic hyperactivity for natural resources increases heavy metals concentrations in the environment: toxicity of healthy food and cancer risks estimated. Journal of Trace Elements and Minerals 4: 100057. 10.1016/j.jtemin.2023.100057
Meng, M., Yang, L., Wei, B., Cao, Z., Yu, J. and Liao, X., 2021. Plastic shed production systems: the migration of heavy metals from soil to vegetables and human health risk assessment. Ecotoxicology and Environmental Safety 215: 112106. 10.1016/j.ecoenv.2021.112106
Mohammadpour, A., Emadi, Z., Samaei, M.R., Ravindra, K., Hosseini, S.M., Amin, M., et al. 2023a. The concentration of potentially toxic elements (PTEs) in drinking water from Shiraz, Iran: a health risk assessment of samples. Environmental Science and Pollution Research. 30: 23295–23311. 10.1007/s11356-022-23535-2
Mohammadpour, A., Emadi, Z., Keshtkar, M., Mohammadi, L., Motamed-Jahromi, M., Samaei, M.R., et al. 2022b. Assessment of potentially toxic elements (PTEs) in fruits from Iranian market (Shiraz): a health risk assessment study. Journal of Food Composition and Analysis 114(2022): 104826. 10.1016/j.jfca.2022.104826
Brendan, CO., Abbas, E-Z., Xiaoli, L., Anjan, P., Xunchang, F., Susmita, S., et al., 2021. Microplastics in soils: an environmental geotechnics perspective. Environmental Geotechnics 8 (8): 586–618. 10.1680/jenge.20.00179
Quispe, N., Zanabria, D., Chavez, E., Cuadros, F., Carling, G. and Paredes, B., 2021. Health risk assessment of heavy metals (Hg, Pb, Cd, Cr and As) via consumption of vegetables cultured in agricultural sites in Arequipa, Peru. Chemical Data Collections 33: 100723. 10.1016/j.cdc.2021.100723
Ruan, X., Ge, S., Jiao, Z., Zhan, W. and Wang, Y., 2023. Bioaccumulation and risk assessment of potential toxic elements in the soil-vegetable system as influenced by historical wastewater irrigation. Agricultural Water Management 279: 108197. 10.1016/j.agwat.2023.108197
Sadee, B.A. and Rasul, J.A., 2023. Determination of heavy metals in edible vegetables and a human health risk assessment. Environmental Nanotechnology, Monitoring & Management 19: 100761. 10.1016/j.enmm.2022.100761
Sawut, R., Kasim, N., Maihemuti, B., Hue, L., Abliz., Abdujappar, A., et al. 2018. Pollution characteristics and health risk assessment of heavy metals in the vegetable bases of northwest China. Science of the Total Environment 642: 864–878. 10.1016/j.scitotenv.2018.06.034
Su, C., Wang, J., Chen, Z., Meng, J., Yin, G., Zhou, Y., et al. 2023. Sources and health risks of heavy metals in soils and vegetables from intensive human intervention areas in South China. Science of the Total Environment 857(1): 159389. 10.1016/j.scitotenv.2022.159389
Tariq, F.S., 2021. Heavy metals concentration in vegetables irrigated with municipal wastewater and their human daily intake in Erbil city. Environmental Nanotechnology, Monitoring & Management 16: 100475. 10.1016/j.enmm.2021.100475
Tariq, F.S., Samsuri, A.W., Karam, D.S., Aris, A.Z., Jamilu, G., 2019. Bioavailability and mobility of arsenic, cadmium, and manganese in gold mine tailings amended with rice husk ash and Fe-coated rice husk ash. Environmental Monitoring and Assessment 191(4): 232. 10.1007/s10661-019-7359-6
Tomno, R.M., Nzeve, J.K., Mailu, S.N., Shitanda, D. and Waswa, F., 2020. Heavy metal contamination of water, soil and vegetables in urban streams in Machakos municipality, Kenya. Scientific African 9: e00539. 10.1016/j.sciaf.2020.e00539
Wang, Z., Chen, X.M., Yu, D.Q., Zhang, L.X., Wang, J.N., Lv, J.S., 2021. Source apportionment and spatial distribution of potentially toxic elements in soils: a new exploration on receptor and geostatistical models. Science of the Total Environment 759(2): 143428. 10.1016/j.scitotenv.2020.143428
Wang, C.-C., Li, M.-Y., Yan, C.-A., Tian, W., Deng, Z.-H., Wang, Z.-X., et al. 2022. Refining health risk assessment of heavy metals in vegetables from high geochemical background areas: role of bioaccessibility and cytotoxicity. Process Safety and Environmental Protection 159: 345–353. 10.1016/j.psep.2022.01.003
Wei, M., Pan, A., Ma, R. and Wang, H., 2023. Distribution characteristics, source analysis and health risk assessment of heavy metals in farmland soil in Shiquan county, Shaanxi province. Process Safety and Environmental Protection 171: 225–237. 10.1016/j.psep.2022.12.089
Wen, Y.B., Li, W., Yang, Z.F., Zhuo, X.X., Guan, D.X., Song, Y.X., et al. 2020. Evaluation of various approaches to predict cadmium bioavailability to rice grown in soils with high geochemical background in the karst region, Southwestern China. Environmental Pollution 258: 113645. 10.1016/j.envpol.2019.113645
Yang, L., Zhang, Y., Kang, S., Wang, Z., Wu, C., 2021. Microplastics in soil: a review on methods, occurrence, sources, and potential risk. Sci. Total Environ. 780: 146546. 10.1016/j.scitotenv.2021.146546
Yuan, Y., Qin, Y., Wang, M., Xu, W., Chen, Y., Zheng, L., et al. 2022. Microplastics from agricultural plastic mulch films: a mini-review of their impacts on the animal reproductive system. Ecotoxicology and Environmental Safety 244: 114030. 10.1016/j.ecoenv.2022.114030
Zunaidi, A.A., Lim, L.H. and Metali, F., 2023. Comparative assessment of the heavy metal phytoextraction potential of vegetables from agricultural soils: a field experiment. Heliyon, 9(2): e13547. 10.1016/j.heliyon.2023.e13547