全生育期淹水联合钝化材料对重度Cd污染下水稻生长和镉富集的影响

为解决中重度污染农田利用问题,本研究采集Cd含量为3.41 mg·kg~(-1)的污染土壤,应用盆栽试验方法,研究了全生育期淹水条件下,赤泥、海泡石、凹凸棒石和腐植酸四种钝化材料16个单一及复合配方对水稻产量、净光合速率、精米和米糠中Cd含量、铁膜Fe和Mn含量、土壤pH值和土壤有效态Cd含量的影响,以期为联合调控的效果提供数据支持。结果表明,四种钝化材料单施及复配均能不同程度增加稻米的产量和叶片的净光合速率,稻米产量与净光合速率呈显著正相关。所有钝化处理均显著降低了精米和米糠中Cd含量,0.5%赤泥、1.0%赤泥、1.0%海泡石、0.5%海泡石+0.5%赤泥、1.0%海泡石+1.0%赤泥、1.0%凹凸棒石+1%赤泥、0.5%海泡石+0.5%赤泥+0.5%腐植酸、1.0%海泡石+1.0%赤泥+1.0%腐植酸等9个处理均能使精米中Cd含量达食品中污染物限量标准(GB 2762—2017)(0.2 mg·kg~(-1)),其中0.5%海泡石+0.5%赤泥处理不仅对稻米Cd含量的降幅最大,而且投入量和经济成本较低。除单施腐植酸外,其他14个钝化处理均提高了土壤的pH值,显著降低了土壤有效态Cd的含量。土壤有效态Cd含量与土壤pH呈显著负相关。精米Cd含量与土壤pH呈负相关,与土壤有效态Cd含量呈正相关。所有钝化材料显著降低了水稻根系铁膜上Fe、Mn和Cd的含量,且精米Cd含量与铁膜Fe、Mn和Cd含量呈正相关,铁膜Cd含量与Fe含量呈显著正相关。这说明,16种钝化处理均能促进水稻的光合作用,进而增加水稻的产量;均能通过提高pH,降低土壤Cd有效态含量来减少水稻籽粒对Cd的富集(除单施腐植酸外);均能通过减少铁膜上Fe和Mn的含量,阻止铁膜对Cd的吸收,进而减少水稻对Cd的吸收和富集。0.5%海泡石+0.5%赤泥处理最佳。

Effects of continuous flooding associated immobilizing treatments on growth and Cd accumulation in rice in heavy Cd polluted soil

The aim of this study is to better understand the problems associated with the utilization of heavy polluted farmland. A soil culture experiment was performed to examine the effects of continuously flooded soil that is heavily polluted with Cd on rice over the entire growth period. There were 16 single and compounded treatments in soil that was heavily polluted with Cd by using red mud, sepiolite, palygorskite, and humic acid to estimate grain yield, photosynthesis rate, Cd concentration in polished rice and rice bran, Fe and Mn concentration in the iron plaque on the root surface, soil pH, and the available Cd concentration. The 16 single and compounded immobilizing agents increased grain yield and leaf photosynthesis rate. There was a significant positive correlation between grain yield and net photosynthetic rate. All immobilizing treatments had a significant decrease in Cd concentration in the polished rice and rice bran. The Cd concentration in polished rice was below the contaminants limit for food (GB 2762-2017) (0.2 mg·kg^-1)for 9 of the immobilizing treatments, including 0.5% red mud, 1.0% red mud, 1.0% sepiolite, 0.5% sepiolite + 0.5% red mud, 1.0% sepiolite + 1.0% red mud, 1.0% attapulgite + 1.0% red mud, 0.5% sepiolite + 0.5% red mud + 0.5% humic acid, 1.0% attapulgite + 1.0% red mud + 1.0% humic acid and 1.0% sepiolite+1.0% red mud+1.0% humic acid. The largest decline of Cd concentration for polished rice was in the 0.5% sepiolite + 0.5% red mud treatment. The treatment used lower amounts, which reduced the economic cost. With the exception of the single treatments of humic acid, the other 14 immobilizing treatments increased soil pH and decreased the available Cd concentration in the soil. There was a significant negative correlation between soil pH and available Cd concentration in the soil. There was a significant negative correlation between Cd concentration in the polished rice and soil pH, and a significant positive correlation between Cd concentration in the polished rice and the available Cd concentration of the soil. Surprisingly, all immobilizing treatments had a decrease in Fe, Mn, and Cd concentration in the iron plaque. There was a positive correlation between the Cd concentration in the polished rice and the Fe, Mn, and Cd concentration in the iron plaque, and there was a positive correlation between the Fe and Mn concentration in the iron plaque. These results indicated that the 16 different immobilizing agents increased rice photosynthesis, which increased rice production. An increase in soil pH, then a decrease in available Cd concentration in the soil caused Cd to accumulate in the grain (except for the single humic acid treatments). There was a decrease in the Fe and Mn concentration in the iron plaque, then a decrease in Cd absorption in the iron plaque, which resulted in a decrease of Cd absorption and accumulation in rice. The combination of 0.5% sepiolite + 0.5% red mud treatment was the best immobilizing agent.