Abstract
Abstract. The Pearl River Delta (PRD) region in South China is one of the most economically developed regions in China, but it is also noted for its severe air pollution due to industrial/metropolitan emissions. In order to continuously improve the understanding and quantification of air pollution in this region, an intensive campaign was executed in PRD during October–November 2008. Here, we report and analyze Aerodyne High-Resolution Aerosol Mass Spectrometer measurements at Kaiping, a rural site downwind of the highly-polluted central PRD area, to characterize the general features of submicron particulate pollution in the regional air. The mean measured PMsub>1 mass concentration was 33.1±18.1 μg m−3 during the campaign and composed of organic matter (33.8%), sulfate (33.7%), ammonium (14.0%), nitrate (10.7%), black carbon (6.7%), and chloride (1.1%), which is characterized by high fractions of inorganic ions due to huge emissions of SO2 and NOx in PRD. The average size distributions of the species (except BC) were all dominated by an accumulation mode peaking at ~450 nm in vacuum aerodynamic diameter. Calculations based on high-resolution organic mass spectra indicate that C, H, O, and N on average contributed 56.6, 7.0, 35.1, and 1.3% to the total organic mass, respectively, corresponding to an organic matter mass to organic carbon mass ratio (OM/OC) of 1.77±0.08. Based on the high-resolution organic mass spectral dataset observed, Positive Matrix Factorization (PMF) analysis differentiated the organic aerosol into three components, i.e., biomass burning (BBOA) and two oxygenated (LV-OOA and SV-OOA) organic aerosols, which on average accounted for 24.5, 39.6 and 35.8% of the total organic mass, respectively. The BBOA showed strong features of biomass burning emissions and has been mainly attributed to the open field burning of crop residues after the harvest in PRD rural areas. The LV-OOA and SV-OOA were found to correspond to more aged (and thus less-volatile) and fresher (and semi-volatile) secondary organic aerosol (SOA), respectively. Analysis of meteorological influence supported that regional transport from the central PRD area was the major origin of the PM1 observed at the Kaiping site.
Highlights
The Pearl River Delta (PRD) region lies in the southeastern coastal part of China and is noted for its flourishing manufacturing and export industries
A clear diurnal pattern of wind during the campaign can be observed in Fig. 2b: eastnortheasterly wind usually blew during the day, bringing pollution from the central PRD area to Kaiping, while during the night the wind usually became calm
A primary explanation for this high organic aerosol (OA) episode is that rice straw burning became prevalent in PRD after the rice harvest starting in mid November
Summary
The Pearl River Delta (PRD) region lies in the southeastern coastal part of China and is noted for its flourishing manufacturing and export industries. City-Cluster Region” launched by the Ministry of Science and Technology, China, was organized by Peking Univer- 2.2 HR-ToF-AMS operation sity in PRD during October–November, 2008 As part of this campaign, we deployed an Aerodyne high-resolution aerosol mass spectrometer for measurement of submicron aerosol particles downwind of the most polluted central PRD area, in order to better characterize the particulate pollution features in the well mixed and more aged regional air. It was the first application of a high-resolution aerosol mass spectrometer in PRD. An Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed in an air monitoring container settled at the Kaiping supersite from 12 October to 18 November 2008. Thermo) coupled with a PM2.5 cyclone was used for simultaneous measurement of refractory black carbon (BC), which cannot be detected by HR-ToF-AMS
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