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研究报告

Diurnal variation of ambient PM_2.5 and PM₁₀ compositions in autumn in Langfang City

基金项目：国家科技支撑计划项目（No.2014BAC16B03）；科技部科技基础性工作专项项目（No.2013FY112700-02）；中央高校基本科研业务费专项资金项目

摘要：为研究廊坊市区秋季环境空气中颗粒物浓度及其组分昼夜变化特征，于2015年9月12—21日在廊坊市进行PM_2.5和PM₁₀采样，并对采集的样品无机元素、水溶性离子和碳组分（OC和EC）分析.结果表明，夜间PM_2.5和PM₁₀浓度比白天高，且下半夜出现大幅上升.PM_2.5/PM₁₀比值为0.49~0.62，下半夜最高.碳组分、Ba、Cr、Cl^-、NO₃^-、SO₄^2-、NH₄⁺等主要富集在PM_2.5中，而Ca、Al、Si、Mg²⁺和Ca²⁺等主要富集在PM₁₀中.通过昼夜颗粒物组分对比发现，夜间EC、Cu、Zn、Cr、Pb、Cl^-、NO₃^-和NH₄⁺等浓度明显上升.同时，下半夜OC/EC比值明显变小，Cl^-、NO₃^-和NH₄⁺浓度明显增大，同时段CO和NO₂浓度上升，而SO₂浓度变化平缓.以上表明采样期间廊坊夜间可能存在移动源和部分工业污染源排放.

Abstract：In order to investigate the characteristics of diurnal variation of ambient particulate matter compositions, PM_2.5 and PM₁₀ were sampled at environmental monitoring and supervision center in Langfang City on 12—21 September 2015. Inorganic elements, water-soluble ions, OC and EC were analyzed. The results showed that the concentrations of PM_2.5 and PM₁₀ at night were higher than in the daytime, and significant increase was observed after midnight. The range of PM_2.5/PM₁₀ ratio was between 0.49~0.62. The PM_2.5/PM₁₀ ratio was the highest after midnight. OC, EC, Ba, Cr, Cl^-, NO₃^-, SO₄^2- and NH₄⁺ were mainly concentrated in PM_2.5, while Ca, Al, Si, Mg²⁺ and Ca²⁺ were mainly concentrated in PM₁₀. By contrast, the concentration of EC, Cu, Zn, Cr, Pb, Cl^-, NO₃^- and NH₄⁺ increased significantly at night. The OC/EC ratio was much smaller after midnight, while Cl^-, NO₃^- and NH₄⁺ concentrations increased significantly. Within the same period, CO and NO₂ concentrations increased, while SO₂ concentration changed slightly. Results from this study indicated possible emissions from vehicle and industrial sources at night.