In the atmosphere, inorganic aerosols are very important species typically accounting for more than 50% of PM_2.5 mass. NH₄⁺, SO₄^2-, and NO₃^- are the most abundant inorganic ions and all have important water-soluble gases as precursors. Therefore, analysis of inorganic ions in aerosols can be conducted through investigation of their variability and in relationship to their precursor water-soluble gas concentrations together with meteorological. In this study, a real-time instrument Monitor for AeRosols and GAses (MARGA) was utilized for the analysis giving an hourly time resolution of S₄^2-, NO₃^-, Cl^-, NH₄⁺, Ca²⁺, Mg²⁺, K⁺ (aerosol) and HNO₃, NH₃, and HCl (gas) all at a low detection limit (0.01-0.09 μgm^-3). Monitoring data from an urban (Yuen Long, YL) and suburban (HKUST) site in Hon...[ Read more ]

In the atmosphere, inorganic aerosols are very important species typically accounting for more than 50% of PM_2.5 mass. NH₄⁺, SO₄^2-, and NO₃^- are the most abundant inorganic ions and all have important water-soluble gases as precursors. Therefore, analysis of inorganic ions in aerosols can be conducted through investigation of their variability and in relationship to their precursor water-soluble gas concentrations together with meteorological. In this study, a real-time instrument Monitor for AeRosols and GAses (MARGA) was utilized for the analysis giving an hourly time resolution of S₄^2-, NO₃^-, Cl^-, NH₄⁺, Ca²⁺, Mg²⁺, K⁺ (aerosol) and HNO₃, NH₃, and HCl (gas) all at a low detection limit (0.01-0.09 μgm^-3). Monitoring data from an urban (Yuen Long, YL) and suburban (HKUST) site in Hong Kong (Oct-Nov, 2016) was analyzed for compositional and diurnal variation differences in PM_2.5 inorganics and water-soluble gases between the two sites. An NH₃ episode was observed in the HKUST supersite due to the application of fertilizer followed by torrential rains from a typhoon. The ammonium-to-sulphate ([NH₄⁺]/[SO₄^2-]) ratio and the threshold of the ammonium poor (AP) and ammonium rich (AR) regimes were found to be quite different at both sites indicating a discrepancy in the formation mechanism of the PM_2.5NO₃^-. Apart from that, eight high NO₃^- episodes were also observed at the YL site and were fed by enhanced NO_x oxidation in the urban conditions and favorable H₃/HNO₃ homogeneous gas phase reaction conditions.