生物炭及其老化对农田NH3挥发及N2O排放的影响

生物炭具有减缓农田NH₃挥发和N₂O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NH₃挥发和N₂O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(S_BET)、总孔容(V_t)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...

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

Biochar has an important potential to alleviate ammonia (NH₃) volatilization and nitrous oxide (N₂O) 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 NH₃ volatilization and N₂O 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 (S_BET), total pore volume (V_t), 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 NH₃ volatilization by 13.57%-29.50%. Compared with BC, OBC and KBC significantly reduced NH₃ volatilization by 14.71% and 9.38%, respectively (P<0.05), while MBC reduced NH₃ volatilization by 3.38% (P>0.05). On the contrary, WBC and FBC increased NH₃ volatilization by 4.55% and 2.72%, respectively (P>0.05). At the same time, the addition of biochar reduced N₂O 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 N₂O. Compared with BC, OBC and KBC significantly increased N₂O emissions by 30.34% and 26.36% (P<0.05), while MBC, FBC and WBC increased N₂O 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.