A　comprehensive　investigation　was　conducted　to　the　urban　soil　in　the　megacity　Shanghai　in　order　to　assess　the　levels　of　PAHs　and　potential　risks　to　human　health,　to　identify　and　quantitatively　assess　source　contributions　to　the　soil　PAHs.　A　total　of　57　soil　samples　collected　in　main　urban　areas　of　Shanghai,　China　were　analyzed　for　26　PAHs　including　highly　carcinogenic　dibenzopyrene　isomers.　The　total　concentrations　ranged　from　133　to　8650　ng　g(-1),　for　Sigma(26)PAHs　and　83.3　to　7220　ng　g(-1)　for　Sigma(16)PAHs,　with　mean　values　of　2420　and　1970　ng　g(-1),　respectively.　DBalP　and　DBaeP　may　serve　as　markers　for　diesel　vehicle　emission,　while　DBahP　is　a　probable　marker　of　coke　tar　as　distinct　from　diesel　emissions.　Six　sources　in　Shanghai　urban　area　were　identified　by　PMF　model;　their　relative　contributions　to　the　total　soil　PAH　burden　were　6%　for　petrogenic　sources,　21%　for　coal　combustion,　13%　for　biomass　burning,　16%　for　creosote,　23%　for　coke　tar　related　sources　and　21%　for　vehicular　emissions,　respectively.　The　benzo[a]pyrene　equivalent　(BaPeq)　concentrations　ranged　from　48.9-2580　ng　g(-1)　for　Sigma(24)PAHs,　7.02-869　ng　g(-1)　for　Sigma(16)PAHs　and　35.7-1990　ng　g(-1)　for　Sigma(4)DBPs.　The　BaPeq　concentrations　of　Sigma(4)DBPs　made　up　72%　of　Sigma(24)PAHs.　Nearly　half　of　the　soil　samples　showed　concentrations　above　the　safe　BaPeq　value　of　600　ng　g(-1).　Exposure　to　these　soils　through　direct　contact　probably　poses　a　significant　risk　to　human　health　from　carcinogenic　effects　of　soil　PAHs.　The　index　of　additive　cancer　risk　(IACR)　values　in　almost　one　third　of　urban　soil　samples　were　more　than　the　safe　value　of　1.0,　indicating　these　urban　soil　PAHs　in　the　study　area　may　pose　a　potential　threat　to　potable　groundwater　water　quality　from　leaching　of　carcinogenic　PAH　mixtures　from　soil.　(C)　2013　Elsevier　B.V.　All　rights　reserved.