Measurement report: Surface exchange fluxes of HONO during the growth process of paddy fields in the Huaihe River Basin, China
Year: 2024
Type: article
Abstract: . Significant amounts of nitrous acid (HONO) released from soil affect the tropospheric atmosphere, as a major precursor of hydroxyl radical. However, the scarcity of soil–atmosphere HONO exchange flux has constrained the comprehension of emission processes and reactive nitrogen budget. Herein, we performed measurements of HONO and NOx fluxes over paddy fields in the Huaihe River Basin for the first time. The entire experiment experienced various agricultural management activities, including rotary tillage, flood irrigation, fertilization, paddy cultivation and growth, and top-dressing. HONO and NO exhibited upward fluxes, while NO2 deposited to the ground, with average hourly fluxes of 0.07 ± 0.22, 0.19 ± 0.53 and -0.37 ± 0.47 nmol m-2 s-1, respectively. During paddy cultivation, the flooded environment with a higher water-filled pore space (~80 %) significantly suppressed the HONO emission, and the fertilization did not have a significant promoting impact on HONO fluxes. During the rotary tillage, continuous peaks were observed in HONO and NO flux, which exhibited a significant correlation (R = 0.77). Moreover, a significant correlation (R = 0.60) between HONO flux and the product of J(NO2) × NO2 was also observed during the daytime. The results suggest that both soil release mechanisms from biological processes and light-driven NO2 conversion are likely active, and together influence the diurnal pattern of HONO flux. Source analysis revealed that the unknown HONO source (Punknown) exhibited a diurnal pattern with higher daytime and lower nighttime values. Sensitivity tests demonstrated that photo-enhanced NO2 conversion on the ground could effectively explain Punknown, and the nighttime HONO flux rates ranging from 0.32 ppbv h-1 to 0.79 ppbv h-1 were fully capable of explaining the nighttime Punknown. Our study emphasized the variability of HONO fluxes across various agricultural management activities, as well as the importance of heterogeneous NO2 conversion on the ground surface and soil emissions in HONO production.
Authors: Fanhao Meng, Baobin Han, Min Qin, Wu Fang, Ke Tang, Dou Shao, Zhitang Liao, Jun Duan, Yan Feng, Yong Huang, Ting Ni, Pinhua Xie
Institutions: National University of Defense Technology, Chinese Academy of Sciences, Hefei Institutes of Physical Science, Anhui Institute of Optics and Fine Mechanics, State Key Laboratory of Pulsed Power Laser Technology, University of Science and Technology of China, West Anhui University, China Meteorological Administration, Institute of Urban Environment
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $1,725
OpenAlex ID: W4405651695