水稻土镉形态分布特征及其生物效应研究

摘要

作物籽粒中镉来源于土壤,土壤中镉形态的含量与作物吸收量密切相关.本文旨在找出作物籽粒中镉与土壤镉形态之间的相关性,探究小麦/水稻籽粒中镉的来源,为阻断镉吸收提供理论依据.采用调查采样方法,对成都平原镉污染区冲积性水稻土耕作层土壤镉形态及对应的作物秸秆和籽粒镉含量进行了测试分析,研究镉超标水稻土不同形态镉的分布特征及其生物效应.结果表明:水稻土不同形态镉的平均含量高低排序为:铁锰氧化物结合态＞残留态＞水溶交换态＞有机质结合态＞碳酸盐结合态,各形态分布极不均衡,生物可利用形态所占比例较大.铁锰氧化物结合态镉与土壤pH值呈极显著正相关(r=0.712**,P＜0.01).小麦、水稻籽粒与秸秆中镉含量均呈极显著正相关,相关系数分别为0.854* (P ＜0.01)和0.872**(P＜0.01).小麦秸秆和籽粒中镉含量与土壤中水溶交换态镉呈极显著正相关(r =0.677*和0.867*,P ＜0.01),与其他形态相关性不显著;水稻籽粒中镉含量仅与土壤中水溶态镉含量呈显著正相关(r =0.573*,P＜0.05),与其他形态相关性不显著.镉污染区水稻土种植水稻和小麦农产品的镉含量超标风险较大.%Cadmium(Cd) in grains came from the soil.The form of cadmium in soil was closely related to the amount absorption of crops.The purpose of this paper was to find out the correlationship between the form of cadmium in soil and cadmium in grains,aimed to explore the source of cadmium in wheat / rice grain,which provided theoretical basis for blocking-up cadmium absorption.Through investigating and sampling method,Cd content in paddy soil of tillage layer on Chengdu plain cadmium polluted area and the corresponding crop straw and grain were analyzed,which used to research the distribution characteristics and biological effects of different forms cadmium in these paddy soils.The results showed that the order of average content of different Cd forms in paddy soil was:O-FeMn ＞ RE ＞ EX ＞ OM ＞ CAB.The content distribution of different forms of Cd were extremely uneven,and the proportion of bio-available form was larger.There was a significant positive correlation between O-FeMn and pH,(r =0.712 * *,P ＜ 0.01).The Cd content in wheat and rice were significantly positive correlated with wheat straw (r =0.854 * *,P ＜ 0.01) and rice straw (r =0.872 * *,P ＜ 0.01) respectively.The EX-Cd in soil correlated with wheat straw and seed,respectively (r =0.677 * * and 0.867 * *,P ＜ 0.01),but not other forms of Cd in soil.The EX-Cd content in soil was only correlated with Cd in rice grain (r =0.573 *,P ＜ 0.05).The risk of Cd-exceed the standard in the grain of the crops which was grown on the polluted soil was high.