In this study, we estimated the aerosol pH in fine particulate matter () collected in HCMC, Vietnam using the thermodynamic equilibrium models (E-AIM Extended Aerosol Inorganics Model and ISORROPIA-II), and the phase partitioning of ammonia. Aerosol pHs estimated by different methods were – . Good correlations between the phasepartitioning approach and models in predicting the aerosol pH were observed with R 2 from to , suggesting that the assumption of equilibrium is valid at the HCMC site. | Vietnam Journal of Science and Technology 55 (4C) (2017) 72-77 AEROSOL pH IN HO CHI MINH CITY, VIET NAM Duong Huu Huy1*, To Thi Hien1, Norimichi Takenaka2 1 Faculty of Environment, University of Science, Vietnam National University, Ho Chi Minh City, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam 2 Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1–1 Gakuen–cho, Naka–ku, Sakai–shi, Osaka 599–8531, Japan * Email: dhhuy@ Received: 15 August 2017; Accepted for publication: 16 October 2017 ABSTRACT Aerosol pH is an important parameter that affects air quality, and the health of aquatic and terrestrial ecosystems. However, the lack of such data was reported in Ho Chi Minh City (HCMC), Vietnam. In this study, we estimated the aerosol pH in fine particulate matter () collected in HCMC, Vietnam using the thermodynamic equilibrium models (E-AIM Extended Aerosol Inorganics Model and ISORROPIA-II), and the phase partitioning of ammonia. Aerosol pHs estimated by different methods were – . Good correlations between the phasepartitioning approach and models in predicting the aerosol pH were observed with R2 from to , suggesting that the assumption of equilibrium is valid at the HCMC site. Keywords: aerosol pH, , AIM, ISORROPIA, Ho Chi Minh City. 1. INTRODUCTION Fine particulate matter with an aerodynamic diameter of equal or less µm (called ) could be related to adverse human health, visibility reduction and formation of acid rain and climate change. The property of is usually acidic because of its main components often being ammonium (NH4+), sulfate (SO42-) and nitrate (NO3-). Aerosol acidity is an important property because many heterogeneous atmospheric chemical processes are pH dependent; for instance, oxidation of SO2 to sulfate aerosol, hydrolysis of N2O5 on the aerosol [1, 2], formation of nitrate and secondary organic aerosol [2, 3], and trace metal .
