硅酸钠对重金属污染土壤性质和水稻吸收Cd Pb Zn的影响

通过盆栽试验研究了Cd-Pb-Zn复合污染土壤(pH6.02,DTPA-Cd、DTPA-Pb和DTPA-Zn含量分别为3.70、650.6、147.9mg·kg-1)中施用硅酸钠对水稻吸收Cd、Pb和Zn的影响。结果表明,硅酸钠明显提高了分蘖期和成熟期土壤pH值,土壤DTPA-Pb分别降低40.34%~43.26%(分蘖期)、10.99%~18.14%(成熟期),土壤DTPA-Zn分别降低43.91%~58.92%(分蘖期)、4.16%~28.41%(成熟期),分蘖期土壤DTPA-Cd也显著降低,但成熟期土壤有效Cd反高于对照。硅酸钠使糙米Pb、Zn含量分别降低了20%~83%和6%~13%,但使糙米Cd含量增加了16%~145%。转移系数的测定表明,施用硅酸钠使分蘖期从根到茎、成熟期从茎到糙米、叶到糙米Pb的转移系数最多分别降低67%、70%和80%;使分蘖期从根到茎,成熟期从根到茎、叶到糙米Zn的转移系数最多分别降低60%、54.90%和59.38%;但使分蘖期从茎到叶、成熟期从茎到糙米、叶到糙米Cd的转移系数最多分别增加54.14%、64.29%和90.24%。以上结果表明,硅酸钠降低了土壤Pb、Zn的有效性和Pb从根到茎(分蘖期)、从茎和叶到糙米(成熟期)的转移及Zn从根到茎(分蘖期)、从根到茎成熟期和从叶到糙米(成熟期)的转移,但提高了成熟期土壤Cd的有效性,促进了Cd从茎到叶(分蘖期)、从茎和叶到糙米(成熟期)的转移。

Effects of sodium silicate on soil properties and Cd, Pb and Zn absorption by rice plant

Effects of sodium silicate(Na₂SiO₃) on the uptake of Cd, Pb, and Zn by rice from heavy metal contaminated soil were studied by pot experiments, using an Indica rice(Yiyou 673). Application of sodium silicate significantly increased soil pH in both tillering and mature stages. Consequently, DTPA-extractable soil Pb was decreased by 40.34%~43.26%(in tillering stage) and 10.99%~18.14%(in mature stage). DTPA-extractable soil Zn was also reduced by 43.91%~58.92%(in tillering stage) and 4.16%~28.41%(in mature stage), respectively. DTPA-extractable Cd was significantly decreased in tillering stage whereas it was increased in mature stage. After application of sodium silicate, Pb transfer factors of root-to-stem in tillering stage, stem-to-grain and leaf-to-grain in mature stage were reduced up to 67%, 70% and 80%, respectively. Zn transfer factors of root-to-stem in tillering stage, root-to-stem and leaf-to-grain in mature stage decreased up to 60%, 54.90% and 59.38%, respectively. However, the Cd transfer factors of stem-to-leaf in tillering stage, stem-to-grain and leaf-to-grain in mature stage were increased up to 54.14%, 64.29% and 90.24%, respectively. Thus, application of sodium silicate decreased the availability of soil Pb and Zn, depressed Pb transfer from root to stem in tillering stage, stem-to-grain and leaf-to-grain in mature stage. Zn transfer of root to stem in tillering stage, root-to-stem and leaf-to-grain in mature stage, thus, decreasing Pb and Zn concentrations in brown rice. On the contrary, sodium silicate raised the availability of Cd in the soil and promoted the transfer of Cd from stem to leaf in tillering stage, and from stem or leaf to grain in mature stage, increasing Cd concentration in brown rice.