Twenty-four-hour PM2.5 and PM10 samples were collected simultaneously at a highly-trafficked roadside station in Hong Kong every sixth day from October 2004 to September 2005.Mass concentrations of PM2.5,PM10-2.5 (or PMcoarse,defined as PM10 – PM2.5),organic carbon (OC),elemental carbon (EC),water-soluble ions,and up to 25 elements were determined.Investigation on the chemical compositions and potential sources of aerosols shows distinct differences between PM2.5 and PM10-2.5.Annual average mass concentration was 55.4±25.5 μg m-3 and 25.9±15.5 μg m-3 for PM2.5 and PM10-2.5,respectively.EC,OM (OM=OC×1.4),and ammonium sulfate (NH4)2SO4 comprised over ~82% of PM2.5,accounting for ~29%,~27%,and ~25% of the PM2.5 mass,respectively.Low OC/EC ratios (less than 1) in PM2.5 suggested influence from fresh diesel-engine exhaust.Seven factors were resolved for PM2.5 data by Positive Matrix Factorization (PMF) Model,including vehicle emissions (~29%),secondary aerosol (~27%),waste incinerator/biomass burning (~23%),residual oil combustion (~10%),marine aerosol (~6%),industrial exhaust (~4%),and resuspended road dust (~1%).PM10-2.5 showed significant difference in chemical composition as compared to PM2.5,with geological material and trace elements being the most abundant components (~28%),followed by unidentified material (~26%),OM(~12%),sea salt (~10%),and ammonium nitrate (NH4NO3,~10%).EC and (NH4)2SO4,the major components (>54%) in PM2.5,each accounted for only ~7% of PM10-2.5.Average OC/EC ratio in PM10-2.5 was 7.8±14.2,suggesting the impact from combustion sources other than vehicular exhaust.The sources for PM10-2.5 comprised of ~20% vehicle-related resuspended dust (e.g.,tire dust/brake linear/petrol evaporation),~17% local resuspension road dust,~17% marine aerosol,~12% secondary aerosol/field burning,~11% vehicle emissions,and ~23% unidentified material.
PM2.5 PM10-2.5 roadside monitoring
Y. Cheng R.J.Zhang S.C.Lee Z.L.Gu K.F.Ho Y.W.Zhang Y.Huang J. C.Chow J.G. J.J.Cao
Department of Environmental Science and Technology, School of Human Settlements and Civil Engineerin Key Laboratory of Regional Climate-Environment Research for Temperate East Asia, Institute of Atmosp Department of Civil and Structural Engineering, Research Center for Environmental Technology and Man Department of Environmental Science and Technology, School of Human Settlements and Civil Engineerin School of Public Health and Primary Care, The Chinese University of Hong Kong Department of Environmental Science and Technology, School of Human Settlements and Civil Engineerin State Key Laboratory of Loess Quaternary Geology, Institute of Earth and Environment, CAS, Xi”an,Sha