Effect of biochar with different particle sizes on the enrichment of methylmercury in rice
[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.[Ch,5 fig.1 tab.34 ref.]
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