Increased cloud activation potential of secondary organic aerosol for atmospheric mass loadings
Increased cloud activation potential of secondary organic aerosol for atmospheric mass loadings
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DOI：
10.5194/acp-9-2959-2009
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发表时间：
2009-01-01
影响因子：
6.3
通讯作者：
Martin, S. T.
中科院分区：
文献类型：
--
作者：
King, S. M.;Rosenoern, T.;Martin, S. T.
在哈佛环境舱中研究了有机颗粒物质量浓度从1到≥100μg/m³对混合有机 - 硫酸盐颗粒的云凝结核（CCN）特性的影响。混合颗粒是在α - 蒎烯的暗臭氧分解过程中有机分子凝结到硫酸铵颗粒上而产生的。环境舱的连续流动模式在长时间内提供了稳定的条件，允许信号积分，从而在代表大气条件的低有机质量浓度下提高了测量精度。对在50nm硫酸盐种子上生长的80nm和100nm颗粒，在八种质量浓度下测量了CCN活性。使用了一个两组分（有机/硫酸盐）科勒模型来预测CCN活性，该模型包括因差分迁移率分析仪（DMA）尺寸选择以及所选80nm和100nm颗粒的有机体积分数而产生的颗粒不均匀性。对于2.9μg/m³及更高的有机质量浓度，使用一组有机组分的物理化学参数能很好地预测所观测到的活化曲线。对于1.74μg/m³及更低的质量浓度，使用相同参数时所观测到的CCN活性超出了预测值，这意味着有机组分的物理化学性质发生了变化。敏感性分析表明，必须引入表面张力的下降来定量解释在低二次有机气溶胶（SOA）颗粒质量浓度下的CCN观测结果。其他因素，如分子量降低、密度增加或范特霍夫因子增加，有助于解释但在定量上不足以作为完整的解释。
The effect of organic particle mass loading from 1 to >= 100 mu g m(-3) on the cloud condensation nuclei (CCN) properties of mixed organic-sulfate particles was investigated in the Harvard Environmental Chamber. Mixed particles were produced by the condensation of organic molecules onto ammonium sulfate particles during the dark ozonolysis of alpha-pinene. A continuous-flow mode of the chamber provided stable conditions over long time periods, allowing for signal integration and hence increased measurement precision at low organic mass loadings representative of atmospheric conditions. CCN activity was measured at eight mass loadings for 80- and 100-nm particles grown on 50-nm sulfate seeds. A two-component (organic/sulfate) Kohler model, which included the particle heterogeneity arising from DMA size selection and from organic volume fraction for the selected 80- and 100-nm particles, was used to predict CCN activity. For organic mass loadings of 2.9 mu g m(-3) and greater, the observed activation curves were well predicted using a single set of physicochemical parameters for the organic component. For mass loadings of 1.74 mu g m(-3) and less, the observed CCN activity increased beyond predicted values using the same parameters, implying changed physicochemical properties of the organic component. A sensitivity analysis suggests that a drop in surface tension must be invoked to explain quantitatively the CCN observations at low SOA particle mass loadings. Other factors, such as decreased molecular weight, increased density, or increased van't Hoff factor, can contribute to the explanation but are quantitatively insufficient as the full explanation.