Surface concentration and vertical column density of NO2 at agricultural area

Abstract

Nitrogen dioxide (NO2) participates in photochemical reaction and is involved in the formation of nitric acid (HNO3), catalytic ozone (O3), nitrate (NO3-), and secondary particulate matter less than 2.5 µm in diameter (PM2.5). Also, NO2 has adverse effects on not only the human health, such as respiratory diseases, lung cancer, asthma, and mortality but also on the environment such as eutrophication, and acid rain. NO2 is mainly emitted into the atmosphere through anthropogenic activities such as combustion, vehicle emissions, and manufacturing activities. However, NO2 is also emitted into the atmosphere as a result of agricultural activities such as biomass burning, and microbiological activities in soil. In addition, since agricultural area is rich in ammonia (NH3) in the atmosphere, NO2 plays an important role in forming ammonium nitrate (NH4NO3) at agricultural area. In this study, to overcome the limitations of stationary measurements, mobile measurement and remote sensing were conducted simultaneously with stationary measurements. NO2 surface concentration was measured by using ultraviolet differential optical absorption spectroscopy (UV-DOAS) and NO2 vertical column density (VCD) was retrieved by multi-axis differential optical absorption spectroscopy (MAX-DOAS), respectively. Measurements were conducted near the livestock (swine and chicken) area (35.83°N, 126.98°E) in the summer of 2020 and winter of 2021, and cropland area (35.81°N, 126.78°E) in the summer of 2021 in Gimje, South Korea, respectively. NO2 surface concentration and NO2 VCD showed similar seasonal and spatial variations at both livestock and cropland area. In order to examine the transport of NO2 to upper mixing layer, bivariate polar plot of NO2 surface concentration and NO2 VCD with back trajectories were analyzed. As a result, different characteristics of transport of NO2 to upper mixing layer were shown for each measurement period. Correlation between PM2.5 chemical compositions related to combustion activity (Cl-), and NO2 surface concentration and NO2 VCD increased in winter compared to summer at livestock area. Also, correlation between PM2.5 chemical compositions related to biomass burning (WSOC, K+), and NO2 surface concentration and NO2 VCD increased at cropland area compared to livestock area in summer. There was no clear difference in the spatial distribution of NO2 VCD between upwind and downwind areas at livestock area in summer. However, at cropland area, there was a difference in spatial distribution of NO2 surface concentration and NO2 VCD between upwind and downwind areas. It may be due to the effect of biomass burning at cropland area. In addition, the possibility of transport of NO2 examined by comparing the difference in spatial distribution of NO2 surface concentration and NO2 VCD at cropland area in summer.