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| Screening for factors affecting rice uptake of cadmium based on spatial clustering and random forests |
| Received:January 23, 2019 |
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| KeyWord:rice;cadmium;spatial cluster;random forest;correlation analysis |
| Author Name | Affiliation | E-mail | | GUO Xin-lei | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China
Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | ZHAO Yu-jie | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | yujiezhao@126.com | | LIU Xiao-wei | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | xwliu2006@163.com | | ZHOU Qi-wen | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | WANG Xia-hui | Chinese Academy of Environmental Planning, Beijing 100012, China | | | LI Zhi-tao | Chinese Academy of Environmental Planning, Beijing 100012, China | | | ZHU Zhi-wei | China National Rice Research Institute, Hangzhou 310006, China | | | ZHANG Tie-liang | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | WANG Zu-guang | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | ZHANG Fan | Key Laboratory for Environmental Factors Control of Agro-Products Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | SUN Yang | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | |
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| Abstract: |
| Understanding the main soil-related factors affecting the accumulation of Cd in rice samples is key to regulating rice Cd concentrations. Regression predictions based on point data often do not reflect regional differences, and most of the main controlling factors show clustering and spatial differences. Based on this principle, a county in Hunan Province was selected as an example and spatial clustering was used to screen hotspots for various soil factors. Soil samples screened in the hotspots were analyzed using multi-parameter detection and the main controlling factors affecting the accumulation of Cd in rice samples were determined through random forest regression. There was up to a 10 fold difference between the Cd enrichment coefficients of rice samples in the high-high and high-low clustering areas, and up to a 17 fold difference between the low-low and low-high clustering areas. In the study area, the critical factors affecting Cd accumulation in rice samples were Ca, pH, and Mn, followed by Fe and Si, and then Zn, DOC, Cl, K, P, Mg, S, Cd, Na, and Cu with a gradually decreasing degree of influence; the influence of SOM was lowest. Regulating the Ca concentration in the soil had a significant impact on soil pH values and subsequently on the uptake of Cd by rice. With an increase in Fe and Mn concentrations in the soil, the rice Cd concentrations decreased exponentially. The Si concentration in the soil was negatively correlated with soil pH values and Fe concentration, and positively correlated with Cd concentration in rice. Organic matter had no significant effect on Cd accumulation in rice. This study confirmed that the combination of bivariate spatial clustering and random forest regression can effectively determine the main factors of soils controlling Cd accumulation in rice samples. Such studies can provide fundamental support for the remediation and control of Cd accumulation in rice and hotspot screening of pollution sources. |
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