不同磷肥对水稻根表铁膜及砷镉吸收的影响——以石灰岩黄壤性水稻土为例

为寻求砷(As) 镉(Cd)复合污染稻田安全利用的有效措施,以贵州石灰岩区As、Cd复合污染黄壤性水稻土为材料,采用盆栽试验,研究了6种磷肥对土壤As、Cd有效性、水稻根表铁膜及As、Cd吸收的影响.结果表明:与对照相比,羟基磷灰石(HAP)、生物酶活性磷肥(BCP)、钙镁磷肥(CMP)处理使土壤pH值显著提高,磷酸二氢钙(MCP)、磷酸二氢钾(MKP)、过磷酸钙(SSP)处理使土壤pH值显著降低.所有磷肥处理均降低了土壤有效Fe含量,其中HAP、MCP、CMP的降低效果显著.HAP显著降低了土壤有效Cd和有效As含量;MCP和BCP显著提高土壤有效Cd含量,但对土壤有效As无显著影响;SSP显著降低了土壤有效Cd含量,但显著提高土壤有效As含量.不同磷肥使水稻根表铁膜数量提升0.6%~27.1%,铁膜数量与铁膜中Cd、As含量分别呈极显著(R²=0.555**)和显著(R²=0.525*)正相关关系.MCP、MKP、BCP显著降低了糙米Cd、As含量,HAP、SSP、CMP显著降低了糙米Cd含量,但对糙米As含量无显著影响.磷肥均使Cd叶→颖壳的转运系数下降,MKP、MCP能抑制As从根到茎的转运,BCP能抑制As从叶到颖壳的转运.磷肥降低水稻糙米Cd、As含量与铁膜数量增加、水稻体内Cd、As转运变化有关.

Effects of different phosphate fertilizers on iron plaque amount on root surface and arsenic and cadmium uptake by rice grown in a limestone yellow loamy paddy soil

To find effective measures for safe utilization of arsenic (As) and cadmium (Cd) co-contaminated paddy soils, the effects of six phosphate fertilizers on the availability of As and Cd in a limestone yellow loamy paddy soil, the amounts of iron plaque on root surface and the uptake of As and Cd by rice were investigated using a pot experiment. The results showed that the values of soil pH increased significantly in the treatments of hydroxyapatite (HAP), bioenzyme active phosphate fertilizer (BCP) and calcium magnesium phosphate fertilizer (CMP), while they decreased significantly in the treatments of calcium dihydrogen phosphate (MCP), potassium dihydrogen phosphate (MKP) and calcium superphosphate (SSP), as compared with that of control. The application of HAP, MCP and CMP significantly reduced the availability of soil iron while the other three phosphate fertilizers had slight influence on it. The effect of phosphate fertilizers on the availability of As and Cd varied with fertilizers. HAP significantly decreased the contents of soil available Cd and As, while MCP and BCP significantly increased the content of soil available Cd but had no significant effect on soil available As, and SSP decreased the content of available Cd but increased the content of available As significantly. The amount of iron plaque in the root surface was increased by 0.6% -27.1% due to phosphate fertilizer application and was positively correlated with Cd and As in it (R²=0.555** and R²=0.525*, respectively). MCP, MKP and BCP significantly decreased the content of Cd and As, while HAP, SSP and CMP significantly reduced the content of Cd, but had no significant effect on the content of As in brown rice. Application of all phosphate fertilizers decreased the transfer coefficient of Cd from leaf to glume, MKP and MCP inhibited the transportation of As from root to stem, while BCP suppressed the transport of As from leaf to glume. It is concluded that the decrease of Cd and As in brown rice caused by phosphate fertilizers application was related to the increased iron plaque amount and the inhibition of Cd and As transportation within rice plant.