复合污染土壤中水稻根际元素特性及效应研究

【目的】以广东大宝山重金属复合污染农田为生长介质,通过研究水稻不同部位生长量、 金属含量、 对金属的富集系数,及其与根际、 非根际土金属含量、 形态变化的相关关系,探讨根际效应可能对水稻体内金属积累转运以及生物量的影响。【方法】选取了广东大宝山稻田重金属复合污染(As、 Pb、 Fe、 Cu、 Zn)土壤及当地常见的20个水稻品种进行根际袋试验,即将根际袋内的土视为根际土,根际袋外的土视为非根际土,将供试水稻品种种植于根际袋土壤中60天后收获,测定水稻各部位的生长量、 不同金属的含量,根际土和非根际土中各金属有效态的含量。【结果】Fe、 Cu、 Pb、 Zn、 As在根部的富集系数均大于其在茎叶的富集系数,各金属在茎叶和根部的富集能力排序分别为Zn Cu As ≈ Pb ≈ Fe和Fe Zn As Cu Pb。根际土和非根际土中各种金属有效态含量均为Fe Cu Pb Zn As。研究还发现,有效态Fe、 Cu和Zn浓度对整株干重的影响显著,作用强弱顺序为Cu Zn Fe,对水稻生长影响作用显著的三种有效态金属Fe、 Cu和Zn均为植物生长所必需的元素。供试土壤中有效态Cu浓度对水稻的生长所起的作用最强。根际土有效态Fe浓度对根系Fe的积累作用效果显著,有效态As浓度显著抑制了根系Fe的积累,且有效态As浓度的作用强于有效态Fe。【结论】根际土中有效态Fe对株高、 根干重、 茎叶干重和整株干重均起着抑制作用,有效态Cu对水稻生长起到了促进作用。根际土有效态As和非根际土有效态Zn对根部Fe的积累起到了抑制作用,根际土有效态Fe和非根际土有效态Cu则起到了促进作用。非根际土有效态Fe和有效态Zn对水稻根长的增加均起到了促进作用。

Characteristics and impacts of elements in rhizosphere in multiple heavy metals polluted rice paddy soil

【Objectives】 The concentrations of heavy metals in the paddy soils and rice seed exceeded remarkably the standard of soil and food quality of China in the Dabaoshan, Shaoguan city, Guangdong province. This influenced the health of local people and social security. The experimental objective was to investigate the biomass, metal accumulation in different parts of rice in the rhizosphere in paddy soils polluted by combined heavy metals. The correlations between metal concentrations, speciation and transformation could help understanding the potential influence of rhizosphere soil on accumulation, transformation of heavy metals and rice biomass.【Methods】 A pot trial was conducted and 20 rice cultivars were grown in the polluted soils. The rhizosphere soils and non-rhizosphere soils were separated by rhizo-bag. The experimental rice cultivars were planted in the soils of rhizo-bag and harvested after 60 days. The root length, shoot height, metal contents in the different parts of rice, available metal contents in the rhizosphere and non-rhizosphere soils were measured. 【Results】 The accumulation factors of Fe, Cu, Pb, Zn and As were greater in roots than those in stems and leaves. The accumulation ability of heavy metals was in the order: Zn Cu As≈Pb≈ Fe and Fe Zn As Cu Pb in shoots and roots of rice, respectively. The concentrations of available metals in the rhizosphere and non-rhizosphere were in the order: Fe Cu Pb Zn As. Available Fe, Cu and Zn concentrations restrained the dry weight of whole plant with the effect followed the order of Cu Zn Fe. These elements had the strongest influence on rice growth, due to the fact that they are the essential elements for plant, with the available Cu concentrations accelerated plant growth. The available As and Fe concentrations had great influence on Fe accumulation in rice roots where As concentrations restrained, while available Fe concentrations accelerated Fe accumulation. The effect was stronger at available As concentrations than of available Fe concentrations. 【Conclusions】The available Fe concentrations had negative effects on the plant height, dry weight of shoot and root. The available Cu concentrations in rhizosphere soil had the remarkably positive effect on the rice growth. The available As concentrations in rhizosphere and the available Zn concentrations in non-rhizosphere had negative effects on the Fe accumulation in roots, while the available Fe concentrations in rhizosphere and the available Cu concentrations in non-rhizosphere had positive effect on Fe accumulation in rice root. In non-rhizosphere soil, the available Fe and Zn concentrations enhanced the root length.