Abstract:

Different crops have great differences in heavy metal uptake capacity, and to understand their uptake capacity is helpful to select suitable planting crops for the safe utilization of contaminated farmland according to local conditions. In this study, 489 pairs of samples of both edible parts of different crops and corresponding plough soil were collected simultaneously from different areas of Zhuji City to test their Cd and Pb contents, calculate the enrichment factors of Cd and Pb in the edible parts, and formulate the soil Cd and Pb threshold for safe production of rice, melon-eggplant vegetables and leafy vegetables. The results showed that the Cd enrichment capacity of the crops was significantly higher than Pb. The pollution risk of Cd in the farmland soil of the city was higher than that of Pb. The enrichment factors of Cd varied greatly among different crops. The average enrichment factor of Cd in rice and peanut was higher than those in the vegetables. The Cd enrichment factor of leafy vegetables was higher than those of rhizome vegetables, legume vegetables and melon-eggplant vegetables. Maize and sweet potato could be planted instead of rice in the Cd-polluted farmland. For planting vegetables in the polluted farmland, the priority should be given to melon-eggplant, rhizome and legume vegetables. The results also showed that there was an obviously staggered phenomenon between the sanitary quality of Cd and Pb in agricultural products and the soil environmental quality. Below the screening value of soil environmental quality, there was still the risk of rice Cd exceeding the standard. However, the investigation results clarified that the threshold values of Cd and Pb for safe production of melon-eggplant vegetables and leafy vegetables were lower than their screening values. In acid, slightly acid and neutral soil, when the Cd content was below 1.00, 1.40 and 4.20 mg/kg respectively, and the Pb content was below 141, 448 and 1530 mg/kg respectively, there was no over-standard heavy metals in melon-eggplant vegetables, and when the Cd content in the three kinds of soil was below 0.32, 0.50 and 2.00 mg/kg respectively, and the Pb content was below 87.30, 121.00 and 164.00 mg/kg respectively, there was no over-standard heavy metals in leafy vegetables.

Key words: agricultural products, cadmium (Cd), lead (Pb), enrichment factor, threshold value, safe utilization