活化磷矿粉对重金属污染土壤上莴苣生长与品质的影响

Effect of activated phosphate rocks on growth and quality of lettuce in heavy metal contaminated soils

用0.5 mol/L草酸与南漳和保康两地的两种低品位磷矿粉在一定条件下混合培养后,施于重金属污染的土壤,通过盆栽试验,研究草酸活化磷矿粉对重金属污染土壤上莴苣生长和品质的影响。结果表明,盆栽试验中,与对照相比,施加磷矿粉和活化磷矿粉后,莴苣的株高、叶片叶绿素SPAD值、叶片和茎的维生素C含量都有不同程度的提高,其效果为活化磷矿粉>磷矿粉>对照,而叶和茎的硝酸盐含量则降低。同时,施加磷矿粉和活化磷矿粉可以提高土壤有效磷、交换性钙、镁含量,降低交换态重金属含量,进而降低莴苣各部分对重金属元素的吸收,如施加活化磷矿粉后莴苣根中Cd、Cu的含量比对照最高可降低55.1%、55.24%,地上部分中Cd、Cu的含量比对照最高可降低59.3%、53.4%,降低重金属含量的效果依次为活化磷矿粉>磷矿粉>对照。

Two kinds of low-grade phosphate rock collected from Nanzhang and Baokang were mixed with 0. 5 mol/L oxalic acid and cultured under certain conditions. A pot experiment was conducted to study the effect of oxalic acid activated phosphate rocks on the quality of lettuce grown in heavy metal contaminated soils. The results show that compared with the control, the plant heights, chlorophyll SPAD values and vitamin C contents of lettuce are increased after applying the phosphate rocks and the activated phosphate rocks and the effect order is： the activated phosphate rocks 〉 the phosphate rocks 〉 the control, while the nitrate contents are reduced. At the same time, the contents of soil available phosphorus, exchangeable calcium and magnesium are increased, and the exchangeable heavy metal contents are decreased under the applications of the phosphate rocks and the activated phosphate rocks. The absorptions of heavy metals in various parts of lettuce are reduced, for example, compared with the control, applying activated phosphate rocks can reduce the Cd and Cu contents mostly by 55. 1% and 55.24% in lettuce roots, and 59.3% and 53.4% in the shoots of lettuce, respectively. The order of the reduced effects of heavy metals is： the activated phosphate rocks 〉 the phosphate rocks 〉 the control. These results indicate that the oxalic acid activated phosphate rocks have better effect for decreasing heavy metals uptake compared with the raw phosphate rocks.