These authors contributed equally to this work
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.
As the basis of agricultural production and human survival, the soil plays a vital role in food and ecological security [
With the tremendous advancement of science and technology in recent years, the lifespan of electronic and electrical products has been shorter, thus forming a large amount of electronic waste. Electronic waste (e-waste) refers to discarded electronic products, consisting of all components and consumables that are part of the electronic products when they are disposed of [
Most of the related research focused on the pollution characteristics and health risks of rice and soil system surrounding the study area [
The study area is located in Luqiao District, Taizhou City, in the southeastern part of Zhejiang Province, China (121°13’ to 121°40’E, 28°20’ to 28°38’N,
The e-waste recycling industry in the region has highly developed since the 1990s, with numerous home-based e-waste disposal workshops and ubiquitous informal dismantling activities [
226 soil samples (0–20 cm) and their corresponding crop samples were collected based on a grid of 100 m × 100 m in this study, including 51 leaf vegetables (LV, including chard, amaranth, caper, hollow cabbage, mullein, green vegetables, lettuce, and fava leaves), 93 solanaceous vegetables (SV, including cauliflower, winter squash, red bean, cucumber, cucumber, cowpea, pepper, pumpkin, eggplant, loofah, string bean, tomato, and corn), 6 root vegetables (RV, including green onion and lotus root) and 76 fruits (orange, pear, grape, peach, and watermelon).
The samples of soils were air-dried and processed in an agate-made mortar to pass through 60 meshes sieves for available state and 100 meshes sieves for total-volume, respectively [
The single factor pollution index evaluation method was commonly used to evaluate the degree of soil contamination [
As an effective quantitative strategy to determining the human risks of multiple exposure pathways (hand-to-mouth intake, dermal contact, and inhalation), the health risk assessment model (USEPA, 2009, 2011) divides human risks into carcinogenic and non-carcinogenic risks for separate analysis, calculating ADD (chronic daily intake of heavy metals) under different exposure routes [
In this study, descriptive statistics, one-way ANOVA, and cluster analysis of data were performed by SPSS 21.0 software. One-way analysis of variance for total metal concentrations in soil among different crops with Duncan’s multiple comparison was performed (
The average contents of Cd, Cu, Pb, and Cr in soils were 0.94, 107.79, 80.28, and 78.14 mg kg-1 (
Element | Range | Mean | SE | CV/% | BV | Ratio/% | RV | Ratio/% | |
---|---|---|---|---|---|---|---|---|---|
pH | total | 5.24~7.39 | 6.06 | 0.05 | 13.70 | — | — | — | — |
leaf vegetables | 5.24~7.39 | 6.06a | 0.12 | 14.09 | — | — | — | — | |
solanaceous vegetables | 5.84~7.26 | 6.28a | 0.07 | 11.91 | — | — | — | — | |
root vegetables | 5.41~5.90 | 5.49b | 0.07 | 2.93 | — | — | — | — | |
fruits | 5.35~6.65 | 5.79ab | 0.09 | 14.58 | — | — | — | — | |
Cd | total | 0.11~7.66 | 0.94 | 0.07 | 117 | 0.13 | 99 | 0.30 | 89 |
leaf vegetables | 0.18~4.86 | 1.10a | 0.18 | 121 | 0.13 | 100 | 0.30 | 78 | |
solanaceous vegetables | 0.12~6.83 | 0.93a | 0.10 | 113 | 0.13 | 98 | 0.30 | 90 | |
root vegetables | 0.49~3.51 | 1.29a | 0.59 | 112 | 0.13 | 100 | 0.30 | 6 | |
fruits | 0.11~7.66 | 0.82a | 0.10 | 111 | 0.13 | 99 | 0.30 | 94 | |
Cu | total | 13.20~526 | 107.79 | 4.98 | 72 | 30.54 | 99 | 50 | 85 |
leaf vegetables | 29.20~361 | 99.95ab | 8.65 | 64 | 30.54 | 98 | 50 | 81 | |
solanaceous vegetables | 29.30~526 | 118.59ab | 8.91 | 77 | 30.54 | 99 | 50 | 87 | |
root vegetables | 63.30~447 | 150.70a | 55.91 | 91 | 30.54 | 100 | 50 | 6 | |
fruits | 13.20~261 | 95.39b | 6.01 | 56 | 30.54 | 99 | 50 | 85 | |
Pb | total | 19.70~565 | 80.28a | 3.66 | 71 | 30.46 | 100 | 90 | 20 |
leaf vegetables | 40.10~144 | 63.17a | 2.43 | 28 | 30.46 | 100 | 90 | 6 | |
solanaceous vegetables | 33.40~565 | 81.82a | 6.95 | 87 | 30.46 | 100 | 90 | 17 | |
root vegetables | 46.80~94.40 | 72.15a | 6.91 | 23 | 30.46 | 100 | 90 | 33 | |
fruits | 19.70~489 | 90.52a | 5.88 | 58 | 30.46 | 99 | 90 | 34 | |
Cr | total | 29.10~213 | 78.14a | 1.41 | 28 | 95.91 | 12 | 150 | 2 |
leaf vegetables | 35.40~96.20 | 72.76a | 1.84 | 19 | 95.91 | 2 | 150 | 0 | |
solanaceous vegetables | 34.60~213 | 80.68a | 2.34 | 30 | 95.91 | 15 | 150 | 2 | |
root vegetables | 35.20~115 | 82.15a | 11.03 | 33 | 95.91 | 33 | 150 | 0 | |
fruits | 29.10~177 | 78.11a | 2.59 | 29 | 95.91 | 13 | 150 | 4 |
Note: CV: coefficient of variation; SE: standard error; BV: background value; SV: risk screening risk value. a The exceeding ratio of heavy metal based on the background values of soils in Zhejiang Province. b. The exceeding ratio of heavy metal based on the risk intervention values for soil contamination of agricultural land with pH < 5.5 of Environmental Quality Standards of Soils in China (2018). c. Different letters within each element of different crops indicate significant differences (
According to Zhao et al. [
The average contents (mg kg-1) of Cd, Pb, and Cu of different crops were followed as: leaf vegetables > root vegetables > solanaceous vegetables > fruits (
Element | Range | Mean | Se | CV/% | LV | Exceedances | |
---|---|---|---|---|---|---|---|
Cd | total | 0.001~0.390 | 0.024 | 0.003 | 200 | — | 10 |
leaf vegetables | 0.004~0.390 | 0.063 | 0.011 | 128 | 0.2 | 3 | |
solanaceous vegetables | 0.001~0.140 | 0.016 | 0.002 | 156 | 0.05 | 7 | |
root vegetables | 0.003~0.091 | 0.033 | 0.015 | 109 | 0.1 | 0 | |
fruits | 0.001~0.044 | 0.007 | 0.001 | 129 | 0.05 | 0 | |
Cu | total | 0.020~2.370 | 0.700 | 0.030 | 67 | — | — |
leaf vegetables | 0.198~2.360 | 1.016 | 0.066 | 48 | — | — | |
solanaceous vegetables | 0.020~2.370 | 0.588 | 0.041 | 72 | — | — | |
root vegetables | 0.426~4.510 | 0.961 | 0.131 | 33 | — | — | |
fruits | 0.128~1.720 | 0.613 | 0.046 | 66 | — | — | |
Pb | total | 0.020~0.230 | 0.041 | 0.003 | 106 | — | 1 |
leaf vegetables | 0.020~0.209 | 0.088 | 0.008 | 63 | 0.3 | 0 | |
solanaceous vegetables | 0.020~0.230 | 0.030 | 0.003 | 107 | 0.3 | 0 | |
root vegetables | 0.020~0.195 | 0.060 | 0.025 | 104 | 0.1 | 1 | |
fruits | 0.020~0.044 | 0.022 | 0.001 | 23 | 0.1 | 0 | |
Cr | total | 0.010~0.480 | 0.060 | 0.006 | 150 | — | 0 |
leaf vegetables | 0.034~0.460 | 0.155 | 0.014 | 67 | 0.5 | 0 | |
solanaceous vegetables | 0.010~0.480 | 0.036 | 0.006 | 187 | 0.5 | 0 | |
root vegetables | 0.010~0.380 | 0.169 | 0.059 | 86 | 0.5 | 0 | |
fruits | 0.010~0.180 | 0.020 | 0.003 | 135 | — | — |
Note: CV: coefficient of variation; SE: standard error; LV: limited value in food GB 2762-2017.
The transfer factor (TF) is the ratio of heavy metal content in crops to the corresponding heavy metal content in the soil, which reflects the absorption and transfer capacity of different crops for heavy metals [
Mean of transfer factor | Cd | Cu | Pb | Cr |
---|---|---|---|---|
leaf vegetables | 0.0955 | 0.0131 | 0.0015 | 0.0022 |
solanaceous vegetables | 0.0252 | 0.0073 | 0.0004 | 0.0004 |
root vegetables | 0.0496 | 0.0095 | 0.0001 | 0.0026 |
fruit | 0.0120 | 0.0084 | 0.0003 | 0.0003 |
For transfer capacities of Cd, the differences among leaf vegetables, root vegetables, and fruits were significant (
Based on the background value of soil elements in Zhejiang Province, the single-factor pollution index indicated that the soils in the study area have been contaminated by different heavy metals to varying degrees. As shown in
Mean | Background value | Risk screening value | ||||||
---|---|---|---|---|---|---|---|---|
Cd | Cu | Pb | Cr | Cd | Cu | Pb | Cr | |
total | 7.22 | 3.53 | 2.64 | 0.81 | 3.13 | 2.16 | 0.89 | 0.52 |
leaf vegetables | 8.47 | 3.27 | 2.07 | 0.76 | 3.67 | 2.00 | 0.70 | 0.49 |
solanaceous vegetables | 7.14 | 3.88 | 2.69 | 0.84 | 3.10 | 2.37 | 0.91 | 0.54 |
root vegetables | 9.94 | 4.93 | 2.37 | 0.86 | 4.31 | 3.01 | 0.80 | 0.55 |
fruit | 6.28 | 3.12 | 2.97 | 0.81 | 2.72 | 1.91 | 1.01 | 0.52 |
The
Vegetable types | |||||
---|---|---|---|---|---|
Cd | Cu | Pb | Cr | ||
total | range | 25.15~1767.69 | 2.16~86.12 | 3.24~92.74 | 0.61~4.44 |
mean | 216.72 | 17.65 | 13.18 | 0.52 | |
ecological risk | high | slight | slight | slight | |
leaf vegetables | range | 40.85~1121.54 | 4.78~59.10 | 6.58~23.64 | 0.74~2.01 |
mean | 254.14 | 16.36 | 10.37 | 1.52 | |
ecological risk | extremely high | slight | slight | slight | |
root vegetables | range | 27.23~1576.15 | 4.79~86.17 | 5.48~92.74 | 0.72~4.44 |
mean | 214.27 | 19.42 | 13.43 | 1.68 | |
ecological risk | high | slight | slight | slight | |
solanaceous vegetables | range | 113.31~1040.77 | 10.36~73.18 | 7.68~15.50 | 0.68~2.40 |
mean | 298.23 | 24.67 | 11.84 | 1.71 | |
ecological risk | extremely high | slight | slight | slight | |
fruit | range | 25.15~1767.69 | 2.16~42.73 | 3.23~80.27 | 0.61~3.69 |
mean | 188.25 | 15.62 | 14.86 | 1.63 | |
ecological risk | high | slight | slight | slight |
The carcinogenic risk of several heavy metals in various crops was much higher in youngsters than in adults (
Element | Adults | Children | |||||||
---|---|---|---|---|---|---|---|---|---|
LV | SV | RV | Fruit | LV | SV | RV | Fruit | ||
Cd | 3.94E–06 | 3.32E–06 | 4.62E–06 | 2.92E–06 | 1.07E–05 | 9.01E–06 | 1.25E–05 | 7.92E–06 | |
4.34E–10 | 3.66E–10 | 5.09E-10 | 3.21E–10 | 6.26E–10 | 5.28E–10 | 7.34E–10 | 4.64E–10 | ||
1.40E–08 | 1.18E–08 | 1.64E–08 | 1.04E–08 | 5.51E–08 | 4.65E–08 | 6.47E–08 | 4.08E–08 | ||
7.62E–04 | 1.88E–04 | 3.99E–04 | 8.09E–05 | 1.23E–03 | 3.02E–04 | 6.43E–04 | 1.30E–04 | ||
Cr | 2.13E–05 | 2.36E–05 | 2.41E–05 | 2.29E–05 | 5.79E–05 | 6.42E–05 | 6.54E–05 | 6.22E–05 | |
1.91E–07 | 2.12E–07 | 2.16E–07 | 2.05E–07 | 2.76E–07 | 3.06E–07 | 3.11E–07 | 2.96E–07 | ||
3.03E–06 | 3.36E–06 | 3.42E–06 | 3.25E–06 | 1.19E–05 | 1.32E–05 | 1.35E–05 | 1.28E–05 | ||
1.53E–04 | 3.52E–05 | 1.67E–04 | 2.01E–05 | 2.47E–04 | 5.67E–05 | 2.69E–04 | 3.24E–05 |
Note:
For children, their non-carcinogenic risk assessment of heavy metals was both significantly greater than those for adults, implying that the same contaminants were more likely to cause non-carcinogenic hazards for children under the same exposure pathway (
Element | Adults | Children | |||||||
---|---|---|---|---|---|---|---|---|---|
LV | SV | RV | Fruit | LV | SV | RV | Fruit | ||
Cd | 1.86E–03 | 1.57E–03 | 2.18E–03 | 1.38E–03 | 2.10E–02 | 1.77E–02 | 2.47E–02 | 1.56E–02 | |
1.98E–05 | 1.67E–05 | 2.33E–05 | 1.47E–05 | 1.19E–04 | 1.01E–04 | 1.40E–04 | 8.83E–05 | ||
2.64E–04 | 2.23E–04 | 3.10E–04 | 1.96E–04 | 4.34E–03 | 3.66E–03 | 5.09E–03 | 3.21E–03 | ||
3.60E–01 | 8.86E–02 | 1.89E–01 | 3.82E–02 | 2.41E+00 | 5.95E–01 | 1.27E+00 | 2.56E–01 | ||
Cu | 4.22E–03 | 5.01E–03 | 6.36E–03 | 4.03E–03 | 4.77E–02 | 5.66E–02 | 7.19E–02 | 4.55E–02 | |
4.48E–07 | 5.31E–07 | 6.75E–07 | 4.27E–07 | 2.69E–06 | 3.19E–06 | 4.06E–06 | 2.57E–06 | ||
1.50E–05 | 1.78E–05 | 2.26E–05 | 1.43E–05 | 2.46E–04 | 2.92E–04 | 3.71E–04 | 2.35E–04 | ||
1.45E–01 | 8.36E–02 | 1.37E–01 | 8.72E–02 | 9.70E–01 | 5.61E–01 | 9.17E–01 | 5.85E–01 | ||
Pb | 3.05E–02 | 3.95E–02 | 3.48E–02 | 4.37E–02 | 3.45E–01 | 4.46E–01 | 3.94E–01 | 4.94E–01 | |
3.25E–06 | 4.21E–06 | 3.71E–06 | 4.66E–06 | 1.95E–05 | 2.53E–05 | 2.23E–05 | 2.80E–05 | ||
7.15E–04 | 9.26E–04 | 8.16E–04 | 1.02E–03 | 1.17E–02 | 1.52E–02 | 1.34E–02 | 1.68E–02 | ||
1.42E–01 | 4.91E–02 | 9.68E–02 | 3.54E–02 | 9.56E–01 | 3.30E–01 | 6.50E–01 | 2.37E–01 | ||
Cr | 4.09E–02 | 4.54E–02 | 4.62E–02 | 4.40E–02 | 4.63E–01 | 5.14E–01 | 5.23E–01 | 4.97E–01 | |
5.14E–04 | 5.69E–04 | 5.80E–04 | 5.51E–04 | 3.09E–03 | 3.42E–03 | 3.49E–03 | 3.32E–03 | ||
5.82E–03 | 6.45E–03 | 6.57E–03 | 6.25E–03 | 9.56E–02 | 1.06E–01 | 1.08E–01 | 1.03E–01 | ||
2.95E+00 | 6.76E–01 | 3.20E+00 | 3.87E–01 | 1.98E+00 | 4.53E–01 | 2.15E+00 | 2.60E–01 |
Note: a:
This research revealed the contamination status of Cd, Pb, Cu, and Cr in the soil-crop system. The study area has been polluted by Cd, Pb, Cu, and Cr as a result of irrational e-waste dismantling activities, especially for Cd. Leaf vegetables suffer more serious heavy metal pollution in the area, which may be due to their high transfer capabilities. The results of the health risk assessment showed that residents in the area faced potential health hazards. Therefore, it is suggested that decrease the intake of these toxic elements and decrease planting high accumulators like leaf vegetables in heavy metal polluted farmland to reduce heavy metal accumulation in crops. Local governments must closely monitor the situation and take steps to address e-waste-related pollution, then ensure that local residents can safely consume the agricultural product.
We thank Luyao Zhang for her help in the laboratory analysis and the figure production. Particularly thanks to Prof. Fu for his supervision to our study.
Meaning | Unit | Adults | Children | ||||
---|---|---|---|---|---|---|---|
IngR | daily intake of soil | mg d−1 | 100 | 200 | |||
InhR | daily intake of air | m3 d−1 | 14.5 | 7.5 | |||
IR | daily intake of crops | kg d−1 | 0.337 | 0.24 | |||
EF | exposure frequency | d a−1 | 350 | 350 | |||
ED | exposure duration | a | 25 | 6 | |||
BW | body weight | kg | 56.8 | 15.9 | |||
AT | exposure time | d | 2628(carcinogenic) | 2628(carcinogenic) | |||
9125(non-carcinogenic) | 2190(non-carcinogenic) | ||||||
PEF | dust emission factor | m3 kg−1 | 1.36 × 109 | 1.36 × 109 | |||
SA | exposed surface area | cm2 | 5074.98 | 2247.56 | |||
SL | skin adhesion coefficient | mg d cm−2 | 0.07 | 0.2 | |||
ABS | skin absorption factor | 0.001 | 0.001 | ||||
exposure pathways | Cd | Cu | Pb | Cr | |||
SF | slope factor | mouth intake | kg d mg−1 | 6.1 | – | – | 0.5 |
dermal contact | 6.1 | – | – | 20 | |||
inhalation | 6.3 | – | – | 42 | |||
RfD | consumption of heavy metals | mouth intake | mg d kg−1 | 1.0 × 10−3 | 4.0 × 10−2 | 3.5 × 10−3 | 3 × 10−3 |
dermal contact | 2.5 × 10−5 | 4.0 × 10−2 | 5.3 × 10−4 | 7.5 × 10−5 | |||
inhalation | 1.0 × 10−5 | 4.02 × 10−2 | 3.5 × 10−3 | 2.55 × 10−5 |
Note: a: “-” means that there is no related data in the article.
where
where
where
where HI (Hazard Index) is the sum of