Monitoring of ambient ammonia in an agricultural area using diffusive passive air samplers

Abstract

Ammonia (NH3) is a well-known basic gas in the atmosphere, which significantly contributes to fine particle (PM2.5) formation. NH3 is emitted mainly from agricultural activities, especially livestock farming and composting livestock waste, which have received much attention as major sources of NH3 in South Korea. Diffusive passive air samplers (PAS) have been widely used in the monitoring of ambient NH3 because of their advantages such as easy installation and cost-effectiveness. However, it is necessary to ensure the accuracy of PAS in the agricultural area due to high concentrations in farmlands and cattle sheds. In this study, the performance of PAS was verified, and the monitoring using PAS was conducted in an agricultural area with farmlands and cattle sheds. The cartridge adsorbent containing NH4+ was extracted using deionized water and analyzed with an ion chromatograph (IC). For quality assurance/quality control (QA/QC), blank samples were analyzed and the PAS were deployed in duplicate. Moreover, linearity between sampling periods and concentrations was evaluated to ensure the maximum adsorbent capacity of PAS. The sampling periods were varied from 2 to 28 days, and the linearity of NH4+ uptake during the sampling period was satisfactory (R2 > 0.95). The absorbent capacity of PAS was estimated to apply in the agricultural area with high levels of NH3. After the verification of PAS, real samples were deployed for two weeks at a farmland and nearby cattle sheds. The levels of NH3 at 11 sites in the agricultural area were compared with those in rural areas, and the spatial distribution was investigated. Finally, the influence of sources and meteorological conditions were evaluated.