开放式空气CO_2浓度增高试验中的NO和NO_2地气交换观测研究

Field measurement of NO and NO_2 exchanges between cultivated lands and the atmosphere in a FACE study.

介绍了农田FACE(free airCO2 enrichment)试验中的NO和NO2 地 气交换观测方法 ,即静态暗箱采样—NO和NO2 化学发光分析法 ,并对观测结果进行了分析讨论 .此观测方法简单、易于操作 ,并可获得可靠的NO和NO2 净交换通量观测结果 .在稻麦轮作农田的旱地阶段 ,无论FACE还是对照处理 ,NO主要表现为地面净排放 ,NO2 主要表现为地面净吸收 .逐日的NO净排放不依赖于土壤温度 ,但却与土壤含水量呈线性负相关 (R2 =0 .82 ,P <0 .0 0 1) .NO2 净吸收具有明显的季节变化特征 ,逐日的净吸收通量随土壤温度和土壤含水量的变化可分别用抛物线方程拟合 (温度 :R2 =0 .74 ,P <0 .0 0 1;含水量 :R2 =0 .6 9,P <0 .0 0 1) .大气CO2 浓度升高 2 0 0± 4 0 μmol·mol-1使NO净排放减弱 19% (t 检验P =0 .0 96 ) ,NO2 净吸收减弱 10 % (t 检验P =0 .2 6 ) ,这主要是植物生长受到促进的缘故 .

A method for measuring NO and NO 2 exchanges between cultivated lands and the atmosphere in a FACE (free-air CO 2 enrichment) study is described. With this method, gas is sampled with a technique of static-opaque-chamber and the fluxes of NO and NO 2 exchanges are determined by analyzing the NO and NO 2 concentrations with a chemiluminescent NO x analyzer. Application of this method in the FACE study of a rice-wheat ecosystem has indicated that reliable data on the exchange fluxes could be obtained. Over the non-waterlogged period of a rice-wheat rotation, net emission of NO from the fields was observed, while net uptake of NO 2 occurred. The daily net emission of NO did not correlated with the soil temperature, but negatively depended upon soil moisture (R^2=0.82,P<0.001). A significant seasonal variation in the net uptake of NO 2 was observed, which was regulated by wheat growth status. The daily uptake of NO 2 depended upon both soil temperature and soil moisture. The dependence for each could be described with a parabola function (for soil temperature:R^2=0.74,P<0.001;for soil moisture:R^2=0.69,P<0.001). An elevation of atmospheric CO 2 by 200±40μmol·mol~ -1 mitigated the net emission of NO by 19% (t-test P=0.096) and might be possible to reduce the net uptake of NO 2 by 10% (t-test P=0.26), which was likely due to the stimulated wheat growth.