Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; University of Science and Technology of China, Hefei 230027, China.
Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China.
Sci Total Environ. 2020 Nov 25;745:140867. doi: 10.1016/j.scitotenv.2020.140867. Epub 2020 Jul 11.
An automated dynamic chamber system was first developed to simultaneously measure the HONO flux and NOx flux. The new dynamic chamber system was applied to field observation, and the HONO and NO exchange flux of farmland in the Huaihe River Basin was obtained for the first time. The performance of the dynamic chamber system was verified in the field. In the field observation, the diurnal variations of the HONO fluxes and NO fluxes before and after a rainfall event exhibited two different trends. Before the rainfall and in the latter stage after the rainfall, the maxima of the HONO fluxes and NO fluxes occurred in the morning, then decreased gradually. However, during the early stage after the rainfall, the HONO fluxes and NO fluxes gradually increased in the morning and reached their maximum values in the afternoon. During the measurement period, the maximum HONO flux was 7.69 ng N m s and the maximum NO flux was 34.52 ng N m s. There was no significant correlation between HONO flux and temperature before the rainfall and in the latter stage after the rainfall period, although the correlation coefficient (R) between HONO flux and temperature reached 0.78 in the early stage after the rainfall period, and the R between NO flux and HONO flux reached more than 0.6 before and after rainfall periods. The HONO flux of fresh soil samples were the same order of magnitude as that of field observations. The field results indicate that soil emissions are an important source of atmospheric HONO during the crop growth stage. Negative NO fluxes were found in most observation periods, and there were significant negative linear correlations between NO fluxes and atmospheric NO concentrations. The R between ambient NO concentration and NO flux was 0.79, and the compensation point of NO was 5 ppbv.
一个自动化的动态箱系统首次被开发出来，用于同时测量 HONO 通量和 NOx 通量。新的动态箱系统被应用于野外观测，首次获得了淮河流域农田的 HONO 和 NO 交换通量。在野外观测中，降水前后 HONO 通量和 NO 通量的日变化表现出两种不同的趋势。在降水前和降水后期，HONO 通量和 NO 通量的最大值出现在早晨，然后逐渐降低。然而，在降水初期，HONO 通量和 NO 通量在早晨逐渐增加，并在下午达到最大值。在测量期间，最大 HONO 通量为 7.69ngNms，最大 NO 通量为 34.52ngNms。在降水前和降水后期，HONO 通量与温度之间没有显著的相关性，尽管在降水初期，HONO 通量与温度之间的相关系数（R）达到 0.78，并且在降水前后，NO 通量与 HONO 通量之间的 R 超过 0.6。新鲜土壤样品的 HONO 通量与野外观测的水平相当。野外结果表明，在作物生长阶段，土壤排放是大气 HONO 的一个重要来源。在大多数观测期间发现了负的 NO 通量，并且 NO 通量与大气 NO 浓度之间存在显著的负线性相关性。环境 NO 浓度与 NO 通量之间的 R 为 0.79，NO 的补偿点为 5ppbv。
