Ambient　coarse　particles　(diameter　1.8-10　mu　m),　fine　particles　(diameter　0.1-1.8　mu　m),　and　ultrafine　particles　(diameter　＜　0.1　mu　m)　in　the　atmosphere　of　the　city　of　Shanghai　were　sampled　during　the　summer　of　2008　(from　Aug　27　to　Sep　08).　Microscopic　characterization　of　the　particles　was　investigated　by　scanning　electron　microscopy　coupled　with　energy　dispersive　X-ray　spectroscopy　(SEM/EDX).　Mass　concentrations　of　Si,　P,　S,　Cl,　K,　Ca,　Ti,　V,　Cr,　Mn,　Fe,　Ni,　Cu,　Zn,　As,　Se,　Br,　Rb,　Sr,　and　Pb　in　the　size-resolved　particles　were　quantified　by　using　synchrotron　radiation　X-ray　fluorescence　(SRXRF).　Source　apportionment　of　the　chemical　elements　was　analyzed　by　means　of　an　enrichment　factor　method.　Our　results　showed　that　the　average　mass　concentrations　of　coarse　particles,　fine　particles　and　ultrafine　particles　in　the　summer　air　were　9.38　+/-　2.18,　8.82　+/-　3.52,　and　2.02　+/-　0.41　mu　g/m(3),　respectively.　The　mass　percentage　of　the　fine　particles　accounted　for　51.47%　in　the　total　mass　of　PM10,　indicating　that　fine　particles　are　the　major　component　in　the　Shanghai　ambient　particles.　SEM/EDX　results　showed　that　the　coarse　particles　were　dominated　by　minerals,　fine　particles　by　soot　aggregates　and　fly　ashes,　and　ultrafine　particles　by　soot　particles　and　unidentified　particles.　SRXRF　results　demonstrated　that　crustal　elements　were　mainly　distributed　in　the　coarse　particles,　while　heavy　metals　were　in　higher　proportions　in　the　fine　particles.　Source　apportionment　revealed　that　Si,　K,　Ca,　Fe,　Mn,　Rb,　and　Sr　were　from　crustal　sources,　and　S,　Cl,　Cu,　Zn,　As,　Se,　Br,　and　Pb　from　anthropogenic　sources.　Levels　of　P,　V,　Cr,　and　Ni　in　particles　might　be　contributed　from　multi-sources,　and　need　further　investigation.