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| Effects of continuous flooding associated immobilizing treatments on growth and Cd accumulation in rice in heavy Cd polluted soil |
| Received:March 15, 2018 Revised:June 27, 2018 |
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| KeyWord:rice;Cd polluted soil;continuous flooding;immobilizing agents;yield;Cd accumulation |
| Author Name | Affiliation | E-mail | | CAO Yun-qing | College of Agriculture, Resources and Environmental Sciences, Tianjin Agriculture University, Tianjin 300384, China
Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | XU Xiao-yan | College of Agriculture, Resources and Environmental Sciences, Tianjin Agriculture University, Tianjin 300384, China | xuxy6699@163.com | | HAN Lei | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | WANG Rui-gang | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | 3761520835@sina.com | | FENG Ren-wei | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | | | XU Ying-ming | Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China | |
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| Abstract: |
| The aim of this study is to better understand the problems associated with the utilization of heavy polluted farmland. A soil culture experiment was performed to examine the effects of continuously flooded soil that is heavily polluted with Cd on rice over the entire growth period. There were 16 single and compounded treatments in soil that was heavily polluted with Cd by using red mud, sepiolite, palygorskite, and humic acid to estimate grain yield, photosynthesis rate, Cd concentration in polished rice and rice bran, Fe and Mn concentration in the iron plaque on the root surface, soil pH, and the available Cd concentration. The 16 single and compounded immobilizing agents increased grain yield and leaf photosynthesis rate. There was a significant positive correlation between grain yield and net photosynthetic rate. All immobilizing treatments had a significant decrease in Cd concentration in the polished rice and rice bran. The Cd concentration in polished rice was below the contaminants limit for food (GB 2762-2017) (0.2 mg·kg-1)for 9 of the immobilizing treatments, including 0.5% red mud, 1.0% red mud, 1.0% sepiolite, 0.5% sepiolite + 0.5% red mud, 1.0% sepiolite + 1.0% red mud, 1.0% attapulgite + 1.0% red mud, 0.5% sepiolite + 0.5% red mud + 0.5% humic acid, 1.0% attapulgite + 1.0% red mud + 1.0% humic acid and 1.0% sepiolite+1.0% red mud+1.0% humic acid. The largest decline of Cd concentration for polished rice was in the 0.5% sepiolite + 0.5% red mud treatment. The treatment used lower amounts, which reduced the economic cost. With the exception of the single treatments of humic acid, the other 14 immobilizing treatments increased soil pH and decreased the available Cd concentration in the soil. There was a significant negative correlation between soil pH and available Cd concentration in the soil. There was a significant negative correlation between Cd concentration in the polished rice and soil pH, and a significant positive correlation between Cd concentration in the polished rice and the available Cd concentration of the soil. Surprisingly, all immobilizing treatments had a decrease in Fe, Mn, and Cd concentration in the iron plaque. There was a positive correlation between the Cd concentration in the polished rice and the Fe, Mn, and Cd concentration in the iron plaque, and there was a positive correlation between the Fe and Mn concentration in the iron plaque. These results indicated that the 16 different immobilizing agents increased rice photosynthesis, which increased rice production. An increase in soil pH, then a decrease in available Cd concentration in the soil caused Cd to accumulate in the grain (except for the single humic acid treatments). There was a decrease in the Fe and Mn concentration in the iron plaque, then a decrease in Cd absorption in the iron plaque, which resulted in a decrease of Cd absorption and accumulation in rice. The combination of 0.5% sepiolite + 0.5% red mud treatment was the best immobilizing agent. |
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