广州地区不同粒径段大气颗粒物中水溶性有机碳的吸光贡献

对广州地区春季（2015年3~4月）、夏季（2015年6~7月）、秋季（2015年9~10月）、冬季（2015年12月~2016年1月）四个季节6个粒径段（<0.49、0.49~0.95、0.95~1.5、1.5~3.0、3.0~7.2以及7.2~10.0μm）的大气颗粒物样品中水溶性有机碳（WSOC）的浓度和光学性质等变化特征进行了研究.结果表明，WSOC的浓度水平呈现冬季（5.07±2.80）μg/m³]>秋季（3.87±1.51）μg/m³]>春季（3.60±1.16）μg/m³]>夏季（2.42±0.51）μg/m³]的季节变化特征；WSOC的质量平均直径（MMD）为0.57μm （春）、0.42μm （夏）、0.49μm （秋）和0.56μm （冬）.WSOC的质量吸收效率MAE₃₆₅差异较大，分布在0.18~1.42m²/g之间，冬季最高；吸收波长指数AAE值分布在3.6~9.8之间.细颗粒物（<3μm）中WSOC对PM₁₀WSOC总吸光的贡献达到了90%以上，其中<0.49μm颗粒物的贡献超过50%.在300~500nm之间，春季、夏季、秋季和冬季WSOC对颗粒物总吸光比例平均值分别为5.23%、2.95%、3.04%和6.92%；其中<0.49μm粒径段的贡献最高，分别为3.11%、1.79%、1.65%和3.45%.进一步通过特征紫外吸光度SUVA值的分析表明芳香性和分子量可能是影响WSOC吸光能力的重要因素.粒径越小颗粒物含有越多的不饱和键，使得MAE₃₆₅值较高.

The size-resolved light absorption contribution of water soluble organic carbon in the atmosphere of Guangzhou

The concentrations and optical properties of water-soluble organic carbon (WSOC) in the size-resolved aerosols of Guangzhou collected during spring (Mar. to Apr. 2015), summer (Jun. to Jul. 2015), autumn (Sept. to Oct. 2015), and winter (Dec. 2015 to Jan. 2016) were investigated. The results showed that the concentration levels of WSOC were in the order of winter(5.07±2.80)μg/m³] > autumn(3.87±1.51)μg/m³]> spring(3.60±1.16)μg/m³] > summer(2.42±0.51)μg/m³], and the mass mean diameter of WSOC in each season was 0.57μm (spring), 0.42μm (summer), 0.49μm (autumn), and 0.56μm (winter), respectively. The MAE₃₆₅ of WSOC varied in a wide range of 0.18~1.42m²/g, with the highest value observed in winter, and the Absorption Ångstr?m Exponent (AAE) varied in a wide range of 3.6~9.8. The light absorption of WSOC in fine particles (<3μm) contributed more than 90% to the total absorption of PM₁₀, and more than 50% was attributed to WSOC in the <0.49μm particles. Over the wavelength of 300~500nm, the average proportion of WSOC light absorption to total aerosol absorption in spring, summer, autumn, and winter was 5.23%, 2.95%, 3.04%, and 6.92%, respectively, and the <0.49μm particles represented the highest contribution, which was 3.11%, 1.79%, 1.65%, and 3.45%, respectively. Further analysis of the specific UV Absorbance (SUVA) indicated that the aromatic content and molecular weight of WSOC might be important components affecting their light-absorbing efficiencies. The higher MAE₃₆₅ values observed in the finer particles are associated with more unsaturated bonds.