Observations on the formation, growth and chemical composition of aerosols in an urban environment.
The charge and chemical composition of ambient particles in an urban environment were determined using a neutral particle and air ion spectrometer and an aerodyne compact time-of-flight aerosol mass spectrometer. Particle formation and growth events were observed on 20 of the 36 days of sampling, with eight of these events classified as strong. During these events, peaks in the concentration of intermediate and large ions were followed by peaks in the concentration of ammonium and sulfate, which were not observed in the organic fraction. Comparison of days with and without particle formation events revealed that ammonium and sulfate were the dominant species on particle formation days while high concentrations of biomass burning OA inhibited particle growth. Analyses of the degree of particle neutralization lead us to conclude that an excess of ammonium enabled particle formation and growth. In addition, the large ion concentration increased sharply during particle growth, suggesting that during nucleation the neutral gaseous species ammonia and sulfuric acid react to form ammonium and sulfate ions. Overall, we conclude that the mechanism of particle formation and growth involved ammonia and sulfuric acid, with limited input from organics.
International Laboratory for Air Quality and Health, Institute of Health and Biomedical Innovation, Queensland University of Technology , Brisbane, QLD 4001, Australia.
Leigh R
LR
Crilley
E Rohan
ER
Jayaratne
Godwin A
GA
Ayoko
Branka
B
Miljevic
Zoran
Z
Ristovski
Lidia
L
Morawska
D000336:Aerosols / Q000032:analysis* / Q000737:chemistry*; D000393:Air Pollutants / Q000032:analysis; D002947:Cities; D004785:Environmental Pollutants / Q000032:analysis* / Q000737:chemistry*; D007477:Ions; D013058:Mass Spectrometry; D008685:Meteorological Concepts; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry; D025341:Principal Component Analysis; D013997:Time Factors
D000336:Aerosols; D000393:Air Pollutants; D004785:Environmental Pollutants; D007477:Ions; D052638:Particulate Matter