Pedosphere 27(3): 475--481, 2017
ISSN 1002-0160/CN 32-1315/P
©2017 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Predicting cadmium safety thresholds in soils based on cadmium uptake by Chinese cabbage
LU Junhe1, YANG Xinping1, MENG Xuchao1, WANG Guoqing2, LIN Yusuo2, WANG Yujun3,ZHAO Fangjie1
1College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China)
2 Nanjing Institute of Environmental Science, Ministry of Environmental Protection of the People's Republic of China, Nanjing 210042 (China)
3 Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
      Cadmium (Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products.In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage ( Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd (0--4 mg kg-1) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions.The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil pH from 4.7 to 7.5.However, further increase in soil pH to $>$ 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg-1 for the tested soils.The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil pH in combination with soil organic matter or clay content.
Key Words:  clay content, soil pH, soil organic matter, soil quality standard, transfer coefficient
Citation: Lu J H, Yang X P, Meng X C, Wang G Q, Lin Y S, Wang Y J, Zhao F J. 2017. Predicting cadmium safety thresholds in soils based on cadmium uptake by Chinese cabbage. Pedosphere. 27(3): 475--481.
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