• 关键词：细颗粒物(PM_2.5)  散射系数  能见度  化学组分  内江

• 基金项目：环境保护部公益项目（No.201009001）；北京市组织部优秀人才培养资助（No.2014000020124G119）；2015年首都经济贸易大学中青年教师科研提升基金

• 陈源
• 首都经济贸易大学安全与环境工程学院, 北京 100070

• 谢绍东
• 北京大学环境科学与工程学院, 北京 100871

• 罗彬
• 四川省环境监测中心, 成都 610041

• 摘要：2012-2013年在内江市环境监测站楼顶采集了PM₁₀和PM_2.5样品，并分析了颗粒物中金属无机元素、水溶性离子和碳质组分的质量浓度，以研究颗粒物的污染水平及其消光特性.采样期间，内江市的PM₁₀和PM_2.5浓度分别为（116.3±54.7）μg·m^-3和（78.6±36.8）μg·m^-3；颗粒物污染冬季较重，其次为秋季，春季和夏季污染水平相当.内江市PM_2.5中以二次无机离子（SNA，42.5%）和有机物（OM，35.0%）污染最为突出，其次为地壳元素（Soil，11.4%）、元素碳（EC，5.2%）和微量元素（Trace，0.3%）.高相对湿度和细颗粒物浓度是导致内江灰霾频发的主要原因，10 km能见度对应的PM_2.5浓度界值为72.2 μg·m^-3.采用IMPROVE模型计算，内江市PM_2.5的平均散射系数为（504.6±293.2）Mm^-1，吸光系数平均为（41.0±20.6）Mm^-1；PM_2.5中硫酸盐对消光系数贡献最大，占40.0%；其次为有机物和硝酸盐，贡献率分别是29.2%和15.3%；EC的贡献率为7.3%.PM_2.5质量浓度与散射系数呈现出较强的线性关系（r=0.88），通过回归方程得到PM_2.5的质量散射效率为4.2 m²·g^-1.

• Abstract：PM samples were collected on the building roof of Neijiang Environmental Monitoring Centre in Sichuan Province of Southwest China during 2012 to 2013. The mass concentrations of inorganic elements, water-soluble ions and carbonaceous aerosols were analyzed to study the chemical compositions of PM and its light extinction effect. During the sampling period, the annual average PM₁₀ and PM_2.5 levels in Neijiang were (116.3±54.7) μg·m^-3 and (78.6±36.8) μg·m^-3, respectively. PM loadings were highest in winter, medium in autumn and lowest in spring and summer. Secondary inorganic ions (SNA) and organic matter (OM) were the most abundant components in PM_2.5, contributing 42.5% and 35.0% to the total mass, followed by soil elements (11.4%), elemental carbon (EC, 5.2%), and trace elements (0.3%). Both high relative humidity and high levels of PM_2.5 were the key factors for the frequent haze occurrence in Neijiang, and the threshold PM_2.5 mass corresponding to atmospheric visibility lower than 10 km was 72.2 μg m^-3. Calculated by the IMPROVE formula, the particulate scattering and absorption coefficient in Neijiang was (504.6±293.2) Mm^-1 and (41.0±20.6) Mm^-1, respectively. Among the PM_2.5 chemical components, sulfate was the largest contributor to its light extinction (40.0%), followed by OM (29.2%), nitrate (15.3%) and EC (7.3%). High correlation was found between PM_2.5 mass and scattering coefficient (r=0.88), and the scattering efficiency of PM_2.5 was 4.2 m²·g^-1.

• Key words：fine particle (PM_2.5)  scattering coefficient  visibility  chemical composition  Neijiang

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