生物质炭对土壤N2O消耗的影响及其微生物影响机理

Biochar’s effect on soil N2O consumption and the microbial mechanism

生物质炭在温室气体减排方面具有很大的发展前景,它不仅能实现固碳,对于在大气中停留时间长且增温潜势大的N2O也能发挥积极作用。本研究采用室内厌氧培养试验,按照生物质炭与土壤质量比(0、1%和5%)加入一定量生物质炭,土壤重量含水率控制在20%。利用Robotized Incubation平台实时检测N2O和N2浓度变化,通过测定土壤中反硝化功能基因丰度(nirK、nirS、nosZ)分析生物质炭对N2O消耗的影响及其微生物方面的影响机理。结果表明:经过20 h厌氧培养后,0生物质炭处理的反硝化功能基因丰度(基因拷贝数g^-1)分别为6.80×10^7(nirK)、5.59×10^8(nirS)和1.22×10^8(nosZ)。与0生物质炭处理相比,1%生物质炭处理的nirS基因丰度由最初的2.65×10^8基因拷贝数g^-1升至7.43×10^8基因拷贝数g^-1,nosZ基因丰度则提高了一个数量级,由4.82×10^7基因拷贝数g^-1升至1.50×10^8基因拷贝数g^-1,然而nirK基因丰度并无明显变化;5%生物质炭处理的反硝化功能基因丰度并未发生显著变化。试验结束时,添加生物质炭处理的N2/(N2O+N2)比值也明显高于0生物质炭处理。相关性分析结果表明,nirS基因丰度和nosZ基因丰度均与N2O浓度在0.01水平上显著相关。试验末期nirS基因丰度和nosZ基因丰度均随着N2O浓度的降低而升高。因此在本试验中,添加1%生物质炭可显著提高nirS和nosZ基因型反硝化细菌的丰度,增大N2/(N2O+N2)比值,促进N2O彻底还原成N2。生物质炭对于N2O主要影响机理是增大了可以还原氧化亚氮的细菌活性,促进完全反硝化。

Biochar is a promising material for mitigating greenhouse gas emissions.In addition to carbon sequestration,it has positive effect on the ozone-depleting gas nitrous oxide(N2O),which is with long residence time and strong warming potential.In this research effort,an anaerobic incubation experiment was conducted.Three treatments with different biochar application rates were set,taking account of biochar to soil ratio(w/w):0(0BC),1%(1%BC)and 5%(5%BC).Soil gravimetric water content was controlled at 20%.According to the robotized incubation platform providing real-time determination of N2O and N2 concentrations and soil denitrification functional gene abundance measurement,we analyzed the impact of biochar on N2O consumption and biological mechanisms.The main results indicated that after a 20-hour anaerobic incubation,the denitrification functional gene abundance of 0BC treatment was 6.80×10^7(nirK),5.59×10^8(nirS),1.22×10^8(nosZ)gene copies per gram soil,respectively.Compared with 0BC treatment,the nirS gene abundance of 1%BC treatment increased from the initial 2.65×10^8 to 7.43×10^8 gene copies per gram soil,while,the nosZ gene abundance increased by an order of magnitude from 4.82×10^7 to 1.50×10^8 gene copies per gram soil.However,there was no significant change in nirK gene abundance.And the denitrification functional gene abundance of 5%BC treatment did not show marked variations.In conclusion,the N2/(N2O+N2)ratio of treatments with biochar application was clearly higher than 0BC treatment.The results of correlation analysis showed that nirS and nosZ gene abundance was significantly correlated with the N2O concentration at 0.01 level,and the abundance of nirS and nosZ genes all increased as N2O concentration declined at the end of the experiment.Therefore,in the present trial,a 1%biochar addition significantly increased the abundance of denitrifying bacteria with nirS and nosZ genotypes and N2/(N2O+N2)ratio,and promoted the complete reduction of N2O to N2.The main mechanism of the biochar effect on N2O emission was the enhanced reduction activities and gene expression of nosZ-containing microorganisms,resulting in complete denitrification.