In-situ Measurement of Aerosol Water Content in an Urban Area Using a Sequential Aerosol-Water Measurement System (SAWMS)

Abstract

Aerosol water content (AWC) significantly affects secondary aerosol formation and atmospheric visibility. Most ambient AWC values are obtained from models because the direct measurement is challenging. In this study, the sequential aerosol-water measurement system (SAWMS) was applied to measure AWC at the Xiaogang (XG) air-quality monitoring site of the Taiwan Environmental Protection Administration (TEPA), located in an industrialized seaport city. The relative humidity (RH) was set at 90% in the SAWMS during measurement, and the PM2.5 AWC was 39.0 ± 14.3 μg m -3 on average, which was 140% higher than the monitored PM2.5 average concentration. Water-soluble inorganic ions (WSIIs) were analyzed offline and used in ISORROPIA II to model the AWC. The modeled and measured AWC was wellcorrelated (R 2 = 0.85; n=39, p< 0.05), indicating that WSIIs contributed the most to AWC. During high AWC periods, NO3concentrations were relatively higher, suggesting that NO3was the predominant species contributing to AWC. Humidographs were constructed to analyze the AWC values under varying RH levels during the humidification and dehumidification processes for the three selected samples. The humidification results revealed a significant difference between the measured and

Spatial and Longitudinal Distributions of Total Carbon, Nitrogen and Sulfur Together With Water‐Soluble Major Ions in Marine Aerosols Collected From the Western Pacific and Southern Ocean

“…Variations in RH are the main challenges for real‐time measurements. Humidification showed a significant difference between the measured and modeled ALWC within 60%–80% RH (Sun et al., 2022). This might be due to deviations of aerosol combination types and the mixing state from atmospheric conditions.…”