壳聚糖改性生物炭对水稻土甲基汞生成及其稻米积累的影响

研究发现稻米易富集甲基汞（MeHg），汞污染区稻米的食用也是人体MeHg暴露的一个重要途径.因此，如何抑制MeHg在稻田中的生成及其在稻米中的富集，是亟需解决的重要问题.为此，本文采用盆栽试验，通过对间隙水、土壤及水稻植株各组织汞含量的分析，探讨了添加壳聚糖改性生物炭对水稻生长期土壤MeHg生成及籽粒MeHg富集的影响.结果表明，添加壳聚糖改性生物炭后能明显降低土壤及间歇水中的总汞（THg）及MeHg含量，与对照相比，土壤中汞的甲基化率降低了51.1%~79.1%；水稻成熟时，添加壳聚糖改性生物炭处理（CMBC）水稻根部MeHg含量比未添加生物炭处理（CK1）低73.1%，比添加未改性生物炭处理（CK2）低62.0%；稻米MeHg含量比CK1低75.8%，比CK2低72.9%；添加生物炭能促进水稻生长，CMBC和CK2处理的植株生物量分别是CK1的1.6倍和1.7倍.盆栽模拟试验结果表明，壳聚糖改性生物炭在促进水稻生长的同时，可以抑制MeHg在稻米中的富集，有一定的推广应用价值.

Effects of Chitosan-modified Biochar on Formation of Methylmercury in Paddy Soils and Its Accumulation in Rice

Rice is well known to accumulate methylmercury (MeHg) and the consumption of rice in mercury (Hg) polluted areas has been confirmed to be a primary source of MeHg exposure. Therefore, how to inhibit the formation and accumulation of MeHg in the paddy field system needs to be solved urgently. Chitosan modified biochar, a potential inhibitor, was selected in this study to explore its effect on MeHg production and accumulation in the paddy field system by analyzing the mercury content of interstitial water, soil, and rice plant tissues. The results showed that the addition of chitosan modified biochar could significantly reduce MeHg concentration in the soil with the decreased methylation rate of 51.1%-79.1%, and could also decrease the total mercury (THg) and MeHg content of interstitial water. At the maturation stage of rice, the MeHg content of rice roots treated with chitosan modified biochar (CMBC) was 73.1% lower than without biochar (CK1) and 62.0% lower than with unmodified biochar (CK2), and the rice MeHg was 75.8% lower than that of CK1 and 72.9% lower than that of CK2. In addition, the application of biochar could promote the growth of rice with the plant biomass of CMBC and CK2 of 1.6 and 1.7 times higher than that of CK1. Generally, the application of chitosan modified biochar into paddy soil could not only promote the growth of rice, but also inhibit the accumulation of MeHg in rice, suggesting that the chitosan modified biochar has a certain application value in the inhibition of the MeHg formation and accumulation in paddy field system.