16 Jan 2023
 | 16 Jan 2023
Status: a revised version of this preprint is currently under review for the journal ACP.

Effects of Secondary Organic Aerosol Water on fine PM levels and composition over US

Stylianos Kakavas, Spyros Pandis, and Athanasios Nenes

Abstract. Water is a key component of atmospheric aerosol, affecting many aerosol processes including gas/particle partitioning of semi-volatile compounds. Water related to secondary organic aerosol (SOAW) is often neglected in atmospheric chemical transport models and is not considered in gas-to-particle partitioning calculations for inorganic species. We use a new inorganic aerosol thermodynamics model, ISORROPIA-lite, which considers the effects of SOAW, to perform chemical transport model simulations for a year over the continental United States to quantify its effects on aerosol mass concentration and composition. SOAW can increase average fine aerosol water levels up to a factor of two when secondary organic aerosol (SOA) is a major PM1 component. This is often the case in the south-eastern U.S where SOA concentrations are higher. Although the annual average impact of this added water on total dry PM1 concentrations due to increased partitioning of nitrate and ammonium is small (up to 0.1 μg m−3), total dry PM1 increases of up to 2 μg m−3 (with nitrate levels increases up to 200 %) can occur when RH levels and PM1 concentrations are high.

Stylianos Kakavas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-815', Anonymous Referee #1, 01 Feb 2023
    • AC1: 'Reply to Reviewer 1 Comments', Athanasios Nenes, 11 Apr 2023
  • RC2: 'Comment on acp-2022-815', Anonymous Referee #2, 10 Feb 2023
    • AC2: 'Reply to Reviewer 2 Comments', Athanasios Nenes, 11 Apr 2023

Stylianos Kakavas et al.

Stylianos Kakavas et al.


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Short summary
Water uptake from organic species in aerosol can affect the partitioning of semi-volatile inorganic compounds, but are not considered in global and chemical transport models. We address this with a version of the PM-CAMx model that considers such organic water effects and use it to carry out year-long aerosol simulations over the continental US. We show that such organic water impacts can have an important impact on dry PM1 levels when RH levels and PM1 concentrations are high.