生物炭及其老化对农田NH_(3)挥发及N_(2)O排放的影响

Effects of biochar and its aging on ammonia volatilization and nitrous oxide emission from farmland

生物炭具有减缓农田NH_(3)挥发和N_(2)O排放的重要潜力,但在施入环境后常常存在“老化”现象,这为其缓解全球变暖的长期有效性带来了不确定性。为了探明生物炭的长期效应,人工加速模拟了自然界中水分、温度、氧气、土壤矿物质及微生物多种老化因素,结合多元表征手段对比不同老化方式对生物炭性质的影响,利用主成分分析法建立新的生物炭性质综合指标来反映老化强度。再通过大田控制试验,采用原位通气法和静态箱-气相色谱法监测夏玉米生长周期内老化前后生物炭施用对农田NH_(3)挥发和N_(2)O排放的影响,为生物炭的可持续应用提供科学依据。结果表明,老化过程增加了原生物炭(BC)的氧含量、比表面积(SBET)、总孔容(Vt)及含氧官能团数量,降低了灰分、碱性、碳含量、平均孔径及其芳香性,各老化作用强度排序为:氧化老化生物炭(OBC)>矿化老化生物炭(KBC)>微生物老化生物炭(MBC)>干湿循环老化生物炭(WBC)>冻融循环老化生物炭(FBC)>BC。生物炭的添加减少了13.57%-29.50%的NH_(3)挥发量。与BC相比,OBC和KBC分别显著降低了14.71%和9.38%的NH_(3)挥发(P<0.05),MBC降低了3.38%的NH_(3)挥发(P>0.05)。相反,WBC和FBC分别增加了4.55%和2.72%的NH_(3)挥发(P>0.05)。同时,生物炭的添加降低了22.36%-40.43%的N_(2)O排放量。其中,BC减排效果最优,老化作用均削弱了原生物炭对N_(2)O的减排效应。与BC相比,OBC和KBC显著增加了30.34%和26.36%的N_(2)O排放量(P<0.05),MBC、FBC和WBC分别增加了19.96%、18.29%和10.92%的N_(2)O排放量(P>0.05)。综上,不同老化方式会对生物炭的理化性质造成不同改变,进而影响土壤气态氮释放。通过对比不同的老化方式,OBC影响最为显著,其次为KBC,MBC居中,WBC和FBC的影响最弱。

Biochar has an important potential to alleviate ammonia(NH_(3))volatilization and nitrous oxide(N_(2)O)emission from farmland,but there is often an“aging”phenomenon after biochar enters the environment,which brings uncertainty to the long-term effectiveness in alleviating global warming.To explore the long-term effect of biochar,a variety of aging factors such as water,temperature,oxygen,soil minerals,and microorganisms in nature were artificially accelerated,combined with multiple characterization methods to compare the effects of different aging methods on the properties of biochar,and used the principal component analysis(PCA)method to establish new comprehensive indicators of biochar properties to reflect the aging intensity.Through field experiment,the effects of aged biochar application on NH_(3) volatilization and N_(2)O emission from summer maize planting farmland were monitored by in-situ ventilation and static chamber-gas chromatographic techniques,providing scientific evidence for the sustainable application of biochar.The results showed that the aging process increased the oxygen content,specific surface area(SBET),total pore volume(Vt),and the number of oxygen-containing functional groups of biochar(BC),while reduced the ash,pH,carbon content,average pore diameter,and aromaticity.The aging intensity was ranked as follows:oxidation aging biochar(OBC)>mineralized aging biochar(KBC)>microbial aging biochar(MBC)>wet-dry cycle aging biochar(WBC)>freeze-thaw cycle aging biochar(FBC)>BC.The addition of biochar reduced the NH_(3) volatilization by 13.57%-29.50%.Compared with BC,OBC and KBC significantly reduced NH_(3) volatilization by 14.71%and 9.38%,respectively(P<0.05),while MBC reduced NH_(3) volatilization by 3.38%(P>0.05).On the contrary,WBC and FBC increased NH_(3) volatilization by 4.55%and 2.72%,respectively(P>0.05).At the same time,the addition of biochar reduced N_(2)O emissions by 22.36%-40.43%.Among them,BC had the best emission reduction effect,and aging has weakened the emission reduction effect of raw biochar on N_(2)O.Compared with BC,OBC and KBC significantly increased N_(2)O emissions by 30.34%and 26.36%(P<0.05),while MBC,FBC and WBC increased N_(2)O emission by 19.96%,18.29%and 10.92%,respectively(P>0.05).In summary,different aging methods can cause different changes in the properties of biochar,thereby affecting the release of soil gaseous nitrogen.By comparing different aging methods,OBC had the most significant impact,followed by KBC,with MBC in the middle,and WBC and FBC had the weakest impact.