复合污染下Cu、Cr、Ni和Cd在水稻植株中的富集特征

掌握水稻对污染土壤中重金属的吸收和富集特征，为科学认识水稻中重金属的残留问题、健康风险提供理论依据。采用田间试验，研究了4个不同处理量Cu、Cr、Ni、Cd复合污染下水稻的富集特征及其随生育期的变化规律。结果表明，重金属在水稻植株各部位中吸收富集系数的大小依次为：Cd〉Cu〉Ni〉Cr，根部重金属吸收富集系数是地上各部位的吸收富集系数的2~100倍。各重金属在水稻植株不同部位的积累分布明显不同，成熟期水稻植株中Cu在水稻不同部位的质量分数为根〉茎≥叶〉米粒〉谷壳，Ni的分布规律为根〉叶〉茎〉米粒〉谷壳，Cr的分布规律为根〉叶〉谷壳≥茎〉米粒，Cd的分布规律为根〉茎〉叶〉米粒〉谷壳；且随着重金属处理量的增加，水稻植株不同部位的重金属质量分数也呈上升趋势。成熟期米粒中Cu、Ni、Cr和Cd的质量分数范围分别为：4.50~6.19、1.86~4.63、0.72~0.76和0.08~0.39 mg·kg-1，与无公害食品标准（GB15199-94、GBT2762-2005）相比，米粒中Cu和Cr的质量分数均未超标，而Ni和Cd（Cd高剂量处理时）的质量分数均超标，存在食用安全风险。重金属在水稻植株不同部位的质量分数随生育期均呈现先升后降的趋势，灌浆中期达到最大，而到成熟期又明显降低。不同重金属在水稻植株中的富集能力和分布规律均呈现明显差异，不同生育期水稻植株中重金属的质量分数明显不同但其质量分数变化呈明显规律性。

Enrichment of Heavy Metals in Rice under Combined Pollution of Cu,Cr, Ni and Cd

Absorption and Accumulation Characteristics of heavy metals by rice in the heavy-metal polluted soils were analyzed to provide theoretical basis for recognizing heavy metals residue in rice, health risk. The enrichment characteristics and changes of Cu, Cr, Ni and Cd integrated effects in rice during their growing were studied through field experiment. The results showed that the enrichment sequence of four heavy metals was Cd 〉 Cu 〉 Ni 〉 Cr, and Cu, Cr, Ni and Cd enrichment coefficients of roots was 2~100 times than that of aerial parts. The distribution of Cu, Cr, Ni and Cd in paddy plant was significantly different.Cu concentration in different parts of the rice plant at mature period was root 〉 stem≥ leaf 〉 grain 〉 chaff, the distribution order of Ni was root 〉 leaf 〉 stem 〉 grain 〉 chaff, the distribution order of Cr was root 〉 leaf 〉 chaff≥ stem 〉 grain, and the distribution order of Cd was root 〉 stem 〉 leaf 〉 grain 〉 chaff. With the heavy metal pollution intensity increasing, the concentration of Cu, Cr, Ni and Cd in different part of rice increased obviously. The concentration of Cu, Ni, Cr and Cd in the grains under maturity stage were 4.50~6.19 mg·kg-1, 1.86~4.63 mg·kg-1, 0.72~0.76 mg·kg-1and 0.08~0.39 mg·kg-1, respectively. Cu and Cr concentration in grain of rice at mature period did not exceed the standard （10 mg·kg-1 and 1.0 mg·kg-1, GB15199-94）, while Ni and Cd concentration in grain exceeded the unpolluted food standard （0.4 mg·kg-1 and 0.20 mg·kg-1, GBT2762-2005）, Ni and Cd ingestion from this rice may pose a health risk to human. The variation of accumulation of Cu, Cr, Ni and Cd in different part of rice along with growing time was similar. The concentration of heavy metal in root, stem and leaf were all increased first, then decreased as rice growing, and reached the highest levels at filling stage, but decreased sharply at maturing stage. The accumulation and distribution of different heavy metals by rice was significant difference, the c