Migration of heavy metals in the soil-grape system and potential health risk assessment

The accumulation of heavy metals in soil may introduce them to the food chain and cause health risks for humans. In the present study, 43 pairs of soil and grape samples (leaf and fruit) were collected form vineyards in the suburbs of Kaifeng city (wastewater-irrigated area in Henan Province, China) to assess the heavy metal (Pb, Cd, Cu, Zn and Ni) pollution level in soil, heavy metal accumulation in different grape tissues and the potential health risk via consumption of grapes. The results showed that the average contents of Pb, Cd, Cu, Zn and Ni in vineyard soil were 42.27, 3.08, 62.33, 262.54 and 26.60 mg/kg, respectively. Some of these soil samples were severely contaminated with Cd and Zn, with an average pollution index (Pi) of 5.14 and 0.88, respectively. Most of these soil samples were severely polluted by heavy metals, with an average Nemerow integrated pollution index (PN) of 3.77. The bioavailable heavy metals were negatively correlated with soil pH and positively correlated with soil organic matter (OM). In addition, heavy metals were more likely to accumulate in grape leaves, and their contents in grape pulp were all within the maximum permissible limit set by China (GB 2762-2017). The average bioaccumulation factors (BFs) of Pb, Cd, Cu, Zn and Ni in grape pulp were 0.007, 0.096, 0.160, 0.078 and 0.023, respectively. Health risk assessment indicated that there was no noncarcinogenic risk for grape consumers (adults and children). However, the carcinogenic risk (CR) ranged from 4.95 × 10-7 to 2.17 × 10-4, and the CR value of three grape samples was higher than 10-4, indicating that a probability of carcinogenic disease existed for humans who regularly consumed the grapes from this region.