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Reducing cadmium pollution in present-season leafy vegetable by calcium formate application through irrigation.

CAI Ke-hang1,2, HUANG Bin1*, CHEN Xin1, SHI Yi1#br#   

  1. (1Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; 2University of Chinese Academy of Sciences, Beijing 100049, China).
  • Online:2017-06-10 Published:2017-06-10

Abstract: Soil pH controlbased approaches are often adopted for remediation of Cdlightly and moderately contaminated agricultural soils, but their overall effects are generally not good in pHcircumneutral soils. In this study, enhancing the conversion from exchangeable Cd to carbonatebounded Cd in rhizosphere soil with little soil pH change by calcium formate solution irrigation during vegetable growth period was proposed for reducing Cd uptake by vegetable from pHcircumneutral soil. The laboratory experiment showed that lowconcentration calcium formate (1.3-3.9 g·L-1) promoted the dissolution of exchangeable Cd. Meanwhile, soil alkalinity increased with little pH change after formate biodegradation within 24 hours, favoring further conversion of the dissolved Cd into less bioavailable carbonatebounded Cd. The results from the subsequent pot experiment with brown soil (total Cd 1.03 mg·kg-1, pH 7.3) planted with cole showed that addition of calcium formate at 76, 152 or 228 mg·kg-1 soil through irrigation twice in the middle and late growing period decreased Cd level in the edible part of cole by 31.6%, 32.7% and 39.4%, respectively, while soil pH changed little compared with the control. Such differences among different treatments disappeared in the subsequent cropping season. The reduction of Cd uptake by presentseason leafy vegetable by calcium formate application is attributed to its enhanced conversion of exchangeable Cd into carbonatebounded Cd in soil. Nevertheless, its effectiveness needs to be further assessed with consideration of impacting factors such as the composition and content of soil exchangeable cations, soil ironmanganese oxides and organic matter.