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Abstract: Aerosol optical properties were continuously measured at an urban site in Shanghai of China from December 2010 to March 2011, and aerosol scattering (σscat) and absorption (σabs) coefficients and single scattering albedo (SSA) were examined. During the entire period, mean σscat, σabs, SSA were 293Mm−1, 66Mm−1 and 0.81, respectively. Higher σscat and σabs occurred in December while relatively lower values were observed in March, and SSA was just opposite to them. σscat and σabs coefficients behaved an apparent bi-peak pattern in diurnal variation: maxima of 319, 76Mm−1 at 8:00 LT during traffic rush hours and sub-maxima of 280, 71Mm−1 at 20:00 LT. SSA also behaved a bi-peak diurnal cycle with maximum 0.85 at 13:00 LT and sub-maximum 0.82 at 4:00 LT. σscat and σabs coefficients showed a clear negative correlation with atmospheric visibility. PM2.5 and black carbon were major contributors to large optical parameters because their concentrations were 2 times higher during haze episode than in clean days. σscat and σabs were low in magnitude when northeasterly winds bring “clean” air from the China Yellow Sea arriving the observation site, and were relatively high when air masses from the north or northwest pass through continental areas or/and industrial regions, indicating impacts of various aerosol origins on aerosol optical properties. [Copyright &y& Elsevier]

Black carbon (BC) aerosol was measured continuously at an urban site in Shanghai (31°18′N, 121°30′E) from January 2011 to January 2012, and the characteristics and relevant remote sources of BC were examined. Daily BC concentrations varied within the range of 0.3–11.4μgm−3 with an annual average of 2.3μgm−3. Comparably, monthly BC concentrations were usually high in the dry season (November–April) but low in the wet season (May–October). Hourly BC showed a similar diurnal pattern with two peaks, one at 7:00–9:00 LT and another at 19:00–21:00 LT, in the four seasons. BC level was always relatively higher during daytime than nighttime. There also existed a workday/weekend difference of BC due to anthropogenic activities. The correlation analyses between BC and meteorological factors indicated that (1) wind speed was an important contributor to BC diffusion in the boundary atmosphere, (2) atmospheric visibility was not highly sensitive to BC, and (3) northwesterly, westerly and southwesterly wind directions related closely to BC. The increase of BC is likely associated with fossil fuel combustion during the winter heating period and agricultural waste burning over the surrounding areas during the summer harvest period, as well as the air masses originating from and/or transiting through these regions. [ABSTRACT FROM AUTHOR]