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| Composition and properties of three organic materials and their effects on soil Cd speciation and Cd content in rice |
| Received:November 23, 2018 |
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| KeyWord:organic materials;soil;Cd;rice;Cd fractionation |
| Author Name | Affiliation | E-mail | | LIU Gao-yun | College of Resources and Environment, Southwest University, Chongqing 400716, China
Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China | | | BAI Hong-cheng | College of Resources and Environment, Southwest University, Chongqing 400716, China
Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China | | | YE Bi-ying | College of Resources and Environment, Southwest University, Chongqing 400716, China
Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China | | | WEI Shi-qiang | College of Resources and Environment, Southwest University, Chongqing 400716, China
Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China | sqwei@swu.edu.cn |
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| Abstract: |
| A pot experiment was conducted in a greenhouse from May 2017 to September 2017 to investigate the effects of organic materials on cadmium (Cd) fractionation in soil and Cd content in rice grains. For this experiment, bulk soil with a Cd content of 0.11 mg·kg-1 and soils with Cd contents artificially adjusted to 2.12 and 10.12 mg·kg-1 were supplemented with 2.5 g C·kg-1(based on C content of the materials) of pig manure (PM), sludge compost (CS), and humus soil (HM), respectively. The Cd content in rice grains and the fractionation of Cd in soils were compared, and the effects of these organic materials were analyzed with respect to their properties. The main results were as follows:The polarities and contents of oxygen-containing functional groups in the organic material followed the order HM > CS > PM. The application of the three organic materials helped alleviate the toxic effect of soil Cd on rice growth. PM, HM, and CS reduced the Cd content in rice grains by 17.24%, 32.41%, and 17.93%, respectively at a soil Cd concentration of 2.12 mg·kg-1. The maximum Cd content in rice grains was 0.19 mg·kg-1 after HM application, which met the criteria of China National Food Safety Standard (GB 2762-2017). However, when the soil Cd concentration reached to 10 mg·kg-1, only PM showed any Cd accumulation reduction effect in rice grains; at this concentration, the requirement of the food safety standard could not be met even with PM application. Significant positive correlations existed between the Cd content in rice grains and the contents of soil exchangeable Cd, Cd bound by Fe-Mn oxides, and Cd content in rice roots. This suggested that organic materials worked mainly by altering the soil Cd fractionation and by inhibiting soil Cd uptake by rice roots and its transfer to the grains. The organic substance that was rich in oxygen-containing functional groups and had high polarity showed better results in terms of the reduction in Cd accumulation in rice grains. |
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