Mixing state of oxalic acid containing particles in the rural area of Pearl River Delta, China: implications for the formation mechanism of oxalic acid
1Institute of Mass Spectrometer and Atmospheric Environment, Jinan
University, Guangzhou 510632, China
2Guangdong Provincial Engineering Research Center for on-line source apportionment system of air pollution,
Guangzhou 510632, China
3School of Energy and Environment, City University of Hong Kong, Hong
Kong, China
4Max Planck Institute for Chemistry, Multiphase Chemistry Department,
Hahn-Meitner-Weg 1, 55128 Mainz, Germany
5State of Environmental Protection Key Laboratory of the formation and
prevention of urban air pollution complex, Shanghai Academy of Environmental
Sciences, Shanghai 200233, China
6State Environmental Protection Key Laboratory of Regional Air
Quality Monitoring, Guangdong Environmental Monitoring Center, Guangzhou,
510308, China
7Guangzhou Hexin Analytical Instrument Limited Company, Guangzhou
510530, China
1Institute of Mass Spectrometer and Atmospheric Environment, Jinan
University, Guangzhou 510632, China
2Guangdong Provincial Engineering Research Center for on-line source apportionment system of air pollution,
Guangzhou 510632, China
3School of Energy and Environment, City University of Hong Kong, Hong
Kong, China
4Max Planck Institute for Chemistry, Multiphase Chemistry Department,
Hahn-Meitner-Weg 1, 55128 Mainz, Germany
5State of Environmental Protection Key Laboratory of the formation and
prevention of urban air pollution complex, Shanghai Academy of Environmental
Sciences, Shanghai 200233, China
6State Environmental Protection Key Laboratory of Regional Air
Quality Monitoring, Guangdong Environmental Monitoring Center, Guangzhou,
510308, China
7Guangzhou Hexin Analytical Instrument Limited Company, Guangzhou
510530, China
Correspondence: Mei Li (limei2007@163.com) and Zhen Zhou
(zhouzhen@gig.ac.cn)
Received: 01 Dec 2016 – Discussion started: 21 Dec 2016 – Revised: 06 Jul 2017 – Accepted: 10 Jul 2017 – Published: 08 Aug 2017
Abstract. The formation of oxalic acid and its mixing state in atmospheric particulate matter (PM) were studied using a single-particle aerosol mass spectrometer (SPAMS) in the summer and winter of 2014 in Heshan, a supersite in the rural area of the Pearl River Delta (PRD) region in China. Oxalic-acid-containing particles accounted for 2.5 and 2.7 % in total detected ambient particles in summer and winter, respectively. Oxalic acid was measured in particles classified as elemental carbon (EC), organic carbon (OC), elemental and organic carbon (ECOC), biomass burning (BB), heavy metal (HM), secondary (Sec), sodium-potassium (NaK), and dust. Oxalic acid was found predominantly mixing with sulfate and nitrate during the whole sampling period, likely due to aqueous-phase reactions. In summer, oxalic-acid-containing particle number and ozone concentration followed a very similar trend, which may reflect the significant contribution of photochemical reactions to oxalic acid formation. The HM particles were the most abundant oxalic acid particles in summer and the diurnal variations in peak area of iron and oxalic acid show opposite trends, which suggests a possible loss of oxalic acid through the photolysis of iron oxalato-complexes during the strong photochemical activity period. In wintertime, carbonaceous particles contained a substantial amount of oxalic acid as well as abundant carbon clusters and BB markers. The general existence of nitric acid in oxalic-acid-containing particles indicates an acidic environment during the formation process of oxalic acid. The peak areas of nitrate, sulfate and oxalic had similar temporal change in the carbonaceous type oxalic acid particles, and the organosulfate-containing oxalic acid particles correlated well with total oxalic acid particles during the haze episode, which suggests that the formation of oxalic acid is closely associated with the oxidation of organic precursors in the aqueous phase.
Oxalic acid is an abundant and ubiquitous constituent in secondary organic aerosol (SOA) and can be an effective tracer for the oxidative processes leading to the formation of SOA. In this work photochemical reactions have a significant contribution to oxalic acid formation in summer, while in winter the formation of oxalic acid is closely associated with the oxidation of organic precursors in the aqueous phase.
Oxalic acid is an abundant and ubiquitous constituent in secondary organic aerosol (SOA) and can...
