Heavy Metal Content in Chinese Vegetable Plantation Land Soils and Related Source Analysis

According to the previous literature published since 1989, statistical analysis for reported data on the heavy metals in Chinese vegetable plantation soils was carried out systematically in this article. The purpose of this investigation was to study the status of heavy metal content in vegetable land soils systematically through objective assessment to promote the development of vegetable production with high quality and efficiency. It is concluded that Zn, Cr, Cu had relatively high concentrations while the mean concentrations of toxic metals, As, Hg, Cd were 8.03, 0.12, 0.28 mg kg−1, respectively with comparatively low concentrations in Chinese vegetable land. Comparing to Chinese Soil Quality Criterion GB 15618-1995 (6.5 < pH < 7.5), about 24.1, 10.3, and 9.2% of the total samples was contaminated by Cd, Hg, and As, respectively, and the descending order of heavy metals was Cd > Hg > As > Zn > Cu > Cr > Pb. When compared among different regions, the more serious heavy metal contamination was found in the vegetable land of eastern China and the main contamination elements were Cd, Hg, and Zn. In the mid region, vegetable plantation land soil was mainly polluted by As and Cd, as well as by Hg, Zn, and Cu, to some extent. In the west region of China, Cd and As contamination was also observed to some degree, along with few soil samples exceeding the grade II level of GB 15618-1995 (6.5 < pH < 7.5) for Cu, Cr, and Hg content. Compared to the five vegetable plantation land patterns, the highest concentration of As, Cd, Hg, and Zn occurred in the industrial/sewage irrigation vegetable land, especially for Hg with 2.36 mg kg−1 content averagely, which is 10.5-21.1 times higher than the other four types of vegetable lands. The highest concentration of Cu and Cr occurred in the greenhouse vegetable land soils, and urban vegetable land soil had the highest Pb content in comparison with the other types of vegetable plantation land patterns. By analyzing heavy metal content under different vegetable land patterns, it was found that soil in vegetable production base had relatively low heavy metal concentrations except for Pb with a slightly higher amount in the suburb area. The soil quality of common vegetable land was good with the lowest concentrations for most heavy metals. Under present utilization patterns of vegetable land, the soil quality in Chinese vegetable base land was good with comparatively low concentrations of heavy metals and mostly not exceeding the grade II level of Chinese Soil Quality Criterion GB 15618-1995 (6.5 < pH < 7.5). However, comparatively serious contamination was found in industrial/sewage irrigation and suburb vegetable land soils.