Paddy Soil Contamination and Remediation Strategies in China.

Paddy Soil Contamination and Remediation Strategies in China Dongmei Zhou Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China ¡¡¡¡Rice is the major grain crop for Chinese people, especially for the population living in the South China. The quality and safety of rice are tightly related with the health of the local residence. China has the largest area of paddy fields and rice yield in the world. The contamination of paddy soil has become a common issue since 1970, when wastewater was applied as irrigation water in agriculture fields. The polluted wastewater from industries, mine sites and steel smelt factories causes serious soil pollution, and heavy contaminated paddy fields have been detected at some locations. Based on conservative estimation, there are more than 3.33 million ha paddy fields polluted and most of them are contaminated with heavy metals, including Cd, As, and Hg. ¡¡¡¡China starts remediating contaminated paddy soils at Zhangshi, Shengyang since 1980, where is used to be a wastewater irrigation zone. High levels of Cd were detected in rice gains from the location, and some of which even over the ¡°Cd rice¡± standard. These agriculture fields now have been converted into industrial utility. To remediate these fields, soil amendments were selected at the beginning to improve soil properties and inhibit bioavailability of heavy metals since 1980s. Then, we tried to find new rice cultivars with high heavy metal tolerance and low bioaccumulation in grain since 1990. At the same time, field managements are also considered, such as irrigation, tillage, and foliar resistance control agents. Non-food plants are suggested to grow on the fields with medium to heavily contaminated, such as linen, white mulberry, energy grasses, and hyper-accumulators for remediation. Now, we have developed some strategies on how to remediate contaminated soils. ¡¡¡¡The government of China has accorded very importance to agriculture soil contamination since 2000. There are soil surveys conducted by China Ministry of Agriculture, Environment Protection Agency and Ministry of Land and Natural Resources. We will start another new survey of soil contamination this year in order to have a comprehensive understanding about soil status in national wide. The Ministries of Agriculture and Finance of China have totally invested more than 4 trillion yuan (571 billion dollars) on 180000 ha demonstration fields in Hunan Province, China, and A remediation technology system has been developed, which called VIP+n (V: variety; I: irrigation; P: pH; n: amendment or leaf fertilizer). ¡¡¡¡There are other special funds on soil remediation of agriculture fields from National Environmental Protection Agency, China. The institute of Soil Science, CAS has already built 267 ha demonstration fields for agriculture soil remediation in Guixi, Jiangxi Province, Qichun, Hubei Province, and Lanping, Yunnan Province based on different technologies and combination. We have made great achievement on these projects. ¡¡¡¡To resolve the problem of agriculture soil contamination, we not only need advanced technology, economic support and environmental management, but also be patient because soil remediation is a long journey to wait. The most important thing is to control pollution resources in all aspects to avoid new pollution, or pollution while remediation. Only after this, we can keep agriculture field safe and make sure of food quality for human health. ¡¡¡¡ ¡¡¡¡Key words: soil; heavy metals; remediation; China ¡¡¡¡