土壤含水量对硝化和反硝化过程N_2O排放及同位素特征值的影响  

The Effects of Soil Water Content on N_2O Emissions and Isotopic Signature of Nitrification and Denitrification

作　　者：郑欠 丁军军[1] 李玉中[1,2] 林伟[1] 徐春英[1] 李巧珍[1] 毛丽丽[1] 

机构地区：[1]中国农业科学院农业环境与可持续发展研究所/农业部旱地节水农业重点实验室,北京100081 [2]中国农业科学院环境稳定同位素实验室,北京100081

出　　处：《中国农业科学》2017年第24期4747-4758,共12页Scientia Agricultura Sinica

基　　金：国家自然科学基金(41473004);国家自然科学青年基金(41301553)

摘　　要：【目的】通过室内培养试验,研究不同含水量对北京顺义潮褐土N_2O排放及同位素特征值(δ15Nbulk,δ18O和nitrogen isotopomer site preference of N_2O,简称SP)的影响,以期获得不同水分条件下土壤N_2O产生途径及变化规律,为农田土壤N_2O减排提供理论依据。【方法】结合稳定同位素技术与乙炔抑制法,以北京顺义潮褐土为试材,设置3个含水量梯度:67%、80%和95%WFPS(土壤体积含水量与总孔隙度的百分比或实际重量含水量与饱和含水量的百分比,简称WFPS),在此基础上设置无C2H2,0.1%(V/V)C2H2和10%(V/V)C2H2处理。将土壤装入培养瓶中培养2 h,之后收集培养瓶中的气体测定N_2O浓度及同位素特征值,并采集土样测定其NH+4-N和NO-3-N的含量。利用同位素二源混合模型计算硝化和反硝化作用对土壤N_2O排放的贡献率,对N_2O产生途径进行量化分析。【结果】根据室内土壤培养测定结果,高(95%WFPS)、中(80%WFPS)和低(67%WFPS)含水量土壤N_2O加权平均排放通量分别为1.17、0.27和0.08 mg N·kg-1·d-1,高含水量土壤N_2O排放量均显著高于中、低含水量处理,中含水量处理显著高于低含水量;整个培养周期,高、中和低含水量土壤N_2O+N_2累积排放量分别为培养初期总的无机氮含量的18.05%、5.27%和1.24%(N_2O+N_2累积排放量分别为19.61、5.72和1.35 mg N·kg-1;各处理NH+4-N+NO-3-N初始含量均为108.62 mg N·kg-1);与低含水量处理相比,高、中含水量土壤的N_2O+N_2累积排放量分别增加了13.53倍和3.24倍,高含水量土壤N_2O+N_2累积排放量比中含水量高2.43倍,表现为随着含水量的增加,土壤无机氮(NH+4-N+NO-3-N)以气态氮(N_2O+N_2)形式的损失量逐渐增加。3个含水量处理N_2O的δ15Nbulk加权平均值变化范围为-42.93‰—-4.07‰,且较高含水量处理显著低于较低含水量处理;10%(V/V)C2H2抑制土壤中N_2O还原成N_2的过程,各含水量土壤中,10%(V/V)C2H2处理组其N_2O的δ18O值显著低于0【Objective】 The objective of this paper is to understand the contribution of microbial processes to N2O production and its changing rules under different water contents to provide a theoretical basis for reducing agricultural N2O emissions. 【Method】A microcosm experiment was performed to investigate the effects of different water-filled pore space on N2O emissions and isotopic signatures（δ^15 N^bulk, δ^18O and nitrogen isotopomer site preference of N2O） of soil at Shunyi district, Beijing. The study combined stable isotope technique and gas inhibitor method to analyze N2O flux and its isotope signatures that emitted from soil. The experiment was set up three different water content levels, including 67%, 80% and 95% WFPS, and with three inhibitor levels,（without C2 H2, with 0.1%（V/V） C2 H2 and with 10%（V/V） C2 H2）. After two hours incubation, the soil samples were collected to determine the concentrations of NH4^＋-N and NO3^--N. The gas samples were collected to determine the isotope signatures, and the two end-members mixing model was applied to quantify the respective contributions of microbial processes to N2O production. 【Result】According to the incubation of the soil, the weighted average N2O flux of 95%, 80% and 67% WFPS were 1.17, 0.27 and 0.08 mg N·kg^-1·d^-1, respectively, and the N2O emissions of 95% WFPS were significantly higher than that of both 80% and 67% WFPS, as well as the N2O emissions of 80% WFPS were significantly higher than that of 67% WFPS. The cumulative emissions of（N2O＋N2） in 95%, 80% and 67% WFPS were 18.05%, 5.27%, and 1.24% of initial mineral nitrogen, respectively, over the entire incubation period. The cumulative emissions of（N2O＋N2） were 19.61, 5.72 and 1.35 mg N·kg^-1, respectively; the initial content of NH4^＋-N＋NO3^--N was 108.62 mg N·kg^-1. Compared with 67% WFPS, the cumulative（N2O＋N2） emissions of 95% and 80% WFPS increased 13.53 and 3.24 times, respectively. The cumulative emissions of（N2O＋N2） in 95% WFPS was 2

关 键 词：土壤孔隙含水量 N2O 硝化作用 反硝化作用 稳定同位素 同位素位嗜值 

分 类 号：S151.9[农业科学—土壤学]