不同粒径贝壳粉对水稻吸收镉与硒的影响

为明确不同粒径贝壳粉对土壤镉、硒有效性及水稻吸收累积镉与硒的影响差异,采用田间试验,设置等量不同粒径贝壳粉施用处理,通过测定水稻植株各部位镉和硒含量,结合土壤pH、土壤有效态镉和有效态硒及其价态含量,对比分析不同粒径贝壳粉对水稻吸收累积镉和硒的影响。结果表明:施用贝壳粉可显著提高稻田土壤pH,降低土壤有效态镉含量,且贝壳粉粒径越小,效果越显著,10、60、200目贝壳粉处理的土壤有效态镉含量分别比对照(常规种植)降低8.68%、10.84%和17.50%,同时稻田土壤有效态硒含量得以提高,并以交换态硒为主,贝壳粉粒径越小,越利于交换态硒向+6价硒转化;施用贝壳粉可促进水稻降镉富硒,糙米镉含量比对照降低9.62%～49.02%,硒含量提高4.31～5.58倍,且水稻体内镉含量与硒含量呈显著的负相关性,其中60目和200目贝壳粉处理的糙米镉含量均符合《食品安全国家标准食品中污染物限量》(GB 2762—2017)的要求。研究表明,在实际生产中可选用粒径60目以上的贝壳粉作为镉污染农田稻米降镉富硒的修复材料。

Effects of adding shell powder with different particle sizes to soil on selenium and cadmium uptake in rice

Shell is a passivating material that can be used for the remediation of heavy metals pollution. The purpose of this study is to clarify effects of different particle sizes of shell powder on the availability of cadmium and selenium in soil and on the absorption and accumulation of cadmium and selenium in rice. A plot field experiment was conducted by adding equal amounts of shell powder with different particle sizes to measure the contents of cadmium and selenium in different parts of rice plants. We further measured the soil pH, content of available cadmium, and the available selenium and valence contents. We aimed to thereby find the optimal shell particle size for rice cultivation. The results showed that the application of shell powder could significantly increase soil pH and reduce the available soil cadmium content; the particle size was inversely proportional to this effect. The available soil cadmium content after the incorporation of 10 mesh, 60 mesh, and 200 mesh shell powders decreased by 8.68%, 10.84% and 17.50% respectively, as compared to that of the control. Meanwhile, the available selenium content increased, and the exchangeable selenium was dominant. The smaller the particle size of shell powder, the more conducive it was for the conversion of exchangeable selenium to + 6 valence. The application of shell powder could facilitate a decrease in cadmium and an increase in selenium in rice. Compared with the control, the cadmium content in brown rice decreased by 9.62%~49.02%, while the selenium content increased by 4.31~5.58 times. The cadmium content in rice was significantly negatively correlated with the selenium content, among which the cadmium content in the brown rice treated with 60 mesh and 200 mesh shell powders met the National Pollution Standards of Food Safety(GB 2762-2017). Therefore, shell powders with a particle size of more than 60 mesh can be used as the remediation material to reduce the cadmium content and enrich selenium in rice contaminated by cadmium in practical production.