Multivariate correlation analysis of bio-accumulation with soil properties and potential health risks of cadmium and lead in rice seeds and cabbage in pollution zones, China.

A total of 475 representative cultivated land and 435 crop samples from 11 provinces of China were collected, and lead and cadmium in 6 polluted areas by wastewater irrigation and metallurgy industry were analyzed. Rice is the major cash crop and staple food of Chinese residents. Cabbage is also a common food in Chinese daily life. Pollution levels and spatial distribution of soil, rice, and cabbage samples were illustrated on the map. In individual or multiple areas, the multivariate correlation of heavy metal's (cadmium and lead) bio-accumulation in two kinds of plants (rice seed and cabbage) and soil properties (pH, cation exchange capacity, and organic matter) was also investigated. Spearman correlation analysis showed that soil pH values and organic matter (OM) had significant effects on the uptake of Cd and Pb in rice seed: the correlation between lg Cd BCF and pH values is -0.148* (p = 0.026), and the correlation between lg Pb BCF and pH values is -0.339** (p = 0.000). The cation exchange capacity (CEC) and pH significantly impact the Cd and Pb uptake in cabbage: the correlation between lg Cd EF and pH values is -0.199* (p = 0.040), and the correlation between lg Pb EF and pH values is -0.203** (p = 0.009). The Cd and Pb bio-concentration factor BCFs of rice and cabbage decreased with the increase of pH, CEC, and OM, except that Pb BCFs increased with the increase of OM in certain areas. The BCF of Cd varied positively from Pb in cabbage, but inversely with Pb in rice significantly at the 0.01 level (two-tailed Spearman correlation analysis). For the first time, the health quotient (HQ) of Cd and Pb in different regions was also calculated and illustrated on the map. In the soil samples of different areas, average HQ values of Cd and Pb in maturity varied from 0.0003-0.0023 to 0.0051-0.0460; average HQ values of immaturity were 0.0011-0.0103 and 0.0222-0.2014. In the rice samples of different areas, average HQ values of Cd and Pb in maturity varied from 0.305-1.360 to 0.027-0.321; average HQ values of immaturity were 0.601-2.678 and 0.053-0.633. Average HQ values orders of magnitude in the cabbage samples of different areas are the same as that of rice samples, and it is 2-4 orders higher than those in soil. Average HQ values of Cd and Pb in maturity varied from 0.152-1.354 to 0.006-0.506; average HQ values of immaturity were 0.510-4.192 and 0.022-0.207. The total HQ values ingested by children were all higher than those in adults. After investigation, it was found that the total HQ value of mature plants was also higher than that of immature plants. The results of this study would be of great help to future soil remediation with similar types.