赤泥颗粒和赤泥对污染土壤镉形态分布及水稻吸收的效应

赤泥能促进土壤中镉形态转化(离子交换态向残渣态转化),但赤泥碱性很强,对土壤的功能有一定的破坏,为此采用盆栽试验研究了赤泥粉和改性赤泥颗粒对酸性潮泥田土壤镉形态分布及水稻生长的影响.结果表明,同比例(5％ W/W)赤泥颗粒的pH值较赤泥粉下降2.4个单位,但随着时间的推移,改性后赤泥颗粒中OH-有缓释的趋势；同比例(5％ W/W)赤泥颗粒对镉污染土壤的形态分布影响在修复前期比赤泥粉小,在修复后期与赤泥粉基本相同甚至稍大,但两者对水稻生长影响不同:添加赤泥颗粒导致水稻增产18.3％,添加赤泥粉导致水稻减产33.3％；赤泥粉和赤泥颗粒均能抑制水稻对土壤中镉的吸收,添加量越高,抑制效果越明显；添加合适的赤泥颗粒能促进水稻的生长,反之抑制水稻的生长,通过试验,初步确定水稻生长状况最好的赤泥颗粒添加量为3％( W/W),此时离子交换态最大降幅为32.1％,残渣态最大增幅为13.7％,水稻增产37.35％,糙米镉含量减少43.8％,低于国家食品卫生标准限值(Cd≤0.2 mg·kg-1).

Effects of Red Mud Granules and Red Mud on the Distribution of Cd Fractions and Cd Uptake by the Paddy Rice in a Contaminated Soil

Red mud can promote fractions transformation of Cadmium(Cd) in contaminated soil(ion-exchangeable into the residual fraction), however, the function of soil was destructed by its strongly alkaline(pH 12~13). The effects of red mud and modified red mud particles on rice growth and distribution of Cd fractions in acid moist mud field soil by the way of pot experiments was studied in this paper. The results showed that the pH value of granulated red mud decreased 2.4 units in the same proportion(5% W/W) compare to red mud, but as time went on, the OH- of modified red mud particles had the slow releasing trend. The effect of granulated red mud on Cd morphology distribution in contaminated soil was less than red mud in earlier repairing stage and equal or more in later stage in the same proportion(5% W/W). The effects between adding granulated red mud and red mud were different that the former increased production of rice by 18.3% and the latter decreased by 33.3%. Cadmium uptake by paddy rice was inhibited by adding granulated red mud and red mud, and the higher addition of granulated red mud, the better effect of the inhibition. Adding the appropriate granulated red mud can promote the growth of rice, on the contrary, inhibit the growth of rice. Thus we could determine initially that the optimal dose of granulated red mud adding to Cd polluted soil was 3%(W/W), at the same time, the decrease of exchangeable, increase of residual and yield were 32.1%, 13.7% and 37.5% respectively. The Cd contents of the unpolished rice decreased 43.8%, which is lower than the maximum permissible concentration of the national food hygiene standards(Cd≤0.2 mg·kg-1).