不同粒径生物质炭对水稻甲基汞富集的影响

Effect of biochar with different particle sizes on the enrichment of methylmercury in rice

【目的】研究生物质炭粒径的改变对其理化性质以及汞污染稻田土壤中修复能力的影响,以期为减少汞污染地区水稻Oryza sativa甲基汞富集量、保障粮食安全提供科学依据。【方法】以水稻秸秆为制备生物质炭的原料,通过筛分法制备不同粒径(<0.5、0.5~1.0、1.0~2.0 mm)的水稻秸秆生物质炭,利用元素分析仪、比表面分析仪、傅里叶红外光谱仪和扫描电镜仪分析不同生物质炭的结构特征变化,并结合盆栽试验研究施用不同粒径生物质炭对水稻甲基汞富集的影响。【结果】(1)随着粒径的减小,生物质炭的表面形貌变化明显,生物质炭比表面积增大,孔隙增多,C—O、—OH和—COO含氧官能团强度增加。(2)与对照相比,3种粒径生物质炭的施入均降低了土壤中甲基汞的生物有效性,水稻各组织中甲基汞富集量减少,其中小粒径生物质炭的降低效果最佳,添加粒径<0.5 mm的生物质炭组精米中的甲基汞质量分数降低了47.01%。(3)生物质炭的施入增大了水稻根际土壤甲基汞质量分数,且这种正向促进作用随着生物质炭粒径的减小而更加明显。【结论】生物质炭粒径的减小能够增强其在汞污染稻田土壤中的修复能力,减少水稻对甲基汞的积累,降低甲基汞暴露风险。

[Objective]The impact of different particle sizes of biochar on the physicochemical properties and its remediation efficacy in mercury-contaminated rice soil was investigated,aiming to establish a scientific foundation for mitigating methylmercury accumulation in rice within mercury-polluted regions and ensure food safety.[Method]Rice straw was utilized as the feedstock for biochar production.The rice straw biochar with different particle sizes(<0.5,0.5−1.0,1.0−2.0 mm)were obtained through sieving,and the structural characteristics of various biochar were analyzed using element analyzer,specific surface analyzer,FTIR spectrometer and scanning electron microscope.The impact of different biochar particle sizes on the accumulation of methylmercury in rice was investigated through a rice pot experiment.[Result](1)With the reduction of particle size,the surface morphology of biochar had significant changes.There was an increase in the specific surface area and pore volume of biochar,as well as an enhancement in the strength of C—O,—OH and—COO oxygen-containing functional groups.(2)Compared with the control group,the application of biochar with different particle sizes reduced the bioavailability of methylmercury in soil,and the enrichment of methylmercury in rice tissues decreased.The application of biochar with the smallest particle size demonstrated the most significant effect,the addition of biochar with particles<0.5 mm reduced the mass fraction of methylmercury in polished rice grain by 47.01%compared to the control.(3)The application of biochar increased the mass fraction of methylmercury in the rhizosphere soil of rice,and this positive promoting effect became more obvious with the decrease of the particle size of biochar.[Conclusion]The reduction of biochar particle size can enhance the remediation capacity of biochar in mercury-contaminated rice soil,decrease the accumulation of methylmercury in rice,and mitigate the exposure risk of methylmercury.