The Effect of Nano Zero-valent Iron, Lime, and Compost Application on Cadmium Uptake by Rice Grown in CdContaminated Soils

• Main Authors: Yi-Ting Lee, 李依庭
• Other Authors: 陳尊賢
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/98128761678114711890

碩士 === 國立臺灣大學 === 農業化學研究所 === 102 === Cadmium（Cd）contamination of paddy soils has been reported for several Asian countries. Compared to other trace metals, Cd is rather mobile in soils. Consequently, Cd is more readily taken up by rice plants, which it can be translocated into the brown rice, and might cause serious human health problems. In-situ chemical stabilization is one of the most efficient and cost-effective remediation techniques for heavy metal contamination sites. Nano zero-valent iron（NZVI）is characterized by their small particle, large specific surface and high reducing power, and it can effectively degraded the organic pollutants or stabilized inorganic toxic heavy metals. Therefore, NZVI has been widely used as one of the remediation techniques for groundwater pollution sites. However, few studies have been evaluated as the stabilization of Cd-contaminated paddy soils by using NZVI. The objectives of this study are (1) to examine the effects of NZVI application on the Cd uptake by rice grown in Cd-contaminated soil and (2) to compare the remediation effectiveness with other soil amendments (by applying lime or compost). The pot experiments were conducted with 3 levels of soil Cd concentrations (2, 10 and 20 mg/kg, sampled from the Cd-contaminated sites) and five soil amendment treatments, including (1) control, (2) by applying lime materials to control the soil pH to 6.8, (3) by applying livestock manure compost at the rate of 40 ton/ha, (4) by applying 0.1% of NVZI and (5) by applying 0.2% of NVZI. The study results showed that the high concentration of soil Cd didn’t cause toxicity of rice productivity. However, the application of NZVI had severe effects on the growth of rice plants and decreased the tiller numbers of rice and also the yields of straw and grains by 15-75%. The possible reasons were proposed as the bioavailability of soil nutrition was affected by applying NZVI or NVZI was toxic to rice production. In all 3 levels of soil Cd concentration, only applying lime materials treatment can reduce the Cd concentration of rice straws. The compost and NZVI treatments can’t significantly decrease the Cd concentration of rice straws. In this study, even the soil Cd concentration is high as 10 mg/kg, the Cd concentration of brown rice was lower than the regulation of brown rice in Taiwan (0.4 mg/kg) announced by Department of Health and Welfare of Taiwan, due to the longer period of soil flooding than farmer conventional treatment. When soil Cd concentration was high as 20 mg/kg, the Cd concentration of brown rice might exceed 0.4 mg/kg and might have high human risk. The effect of soil amendment application was similar to the results of rice straw, only the application of lime treatment can significantly decrease the Cd concentration of brown rice. The Cd concentration of brown rice in compost and NZVI treatments were all higher than the regulation of brown rice. In conclusions, the application of NZVI had toxic effects on the growth of rice plants and it might produce the Cd uptake in rice plant. Therefore, the remediation by NVZI was not effective compared with by applying lime materials.