南京二次PM2.5来源解析

论文总字数：17566字

目 录

1前言············································································································1

2方法············································································································2

2．1 模式描述·····························································································2

2．2 模型应用·····························································································3

3 研究结果··································································································4

3．1 污染物浓度的时间变化规律····································································4

3．2 污染物排放源解析·················································································8

4 结论··········································································································17

参考文献······································································································18

致谢··············································································································20

南京二次PM_2.5来源解析

黄海涛

（,China

Abstract: This study applied a source-oriented model (CMAQ) to determine the source contribution of Nanjing gas pollutants and secondary PM_2.5: sulfate and nitrate. There are five main sources of secondary PM_2.5 in Nanjing: Power emissions, Residents living emissions, Industrial sources, Traffic emissions and Open burning. Correlation between the concentration of NO and NO₂ and the concentration of nitrate particles is found, but the correlation between SO₂ and sulfate particles is low. There is a negative correlation between O₃ and nitrate particles. Industrial activities on nitrate particles contribution rate is very high in autumn and winter, with the contribution of 40-42%. Industrial activity of sulfuric acid particles was the highest in summer and autumn (69-70%). Industrial activity’s contribution rates of NO and NO₂, which are nitrate precursors, are 50-51% and 47-48% respectively in summer and autumn. As sulfate precursor, industrial activity’s contribution rate to SO₂ was highest for 85-86%. Power and transportation are the two major emission sources of secondary PM_2.5 in Nanjing. Summer open combustion (26%), industrial sources (45%) and transportation (26%) also have high contributions to ozone. Ozone also presents the "weekend effect", which means weekend's ozone concentration is higher than the daily average concentration of working days.

Key Words: Nanjing, Source-oriented model, Secondary PM_2.5, Source apportionment

1. 前言：

改革开放后，随中国经济规模的扩大，经济活动不断增多，越来越多的环境问题开始凸显。尤其是近年来越来越受关注的空气污染问题，其中“PM_2.5”一词更是进入大众视野，为越来越多的民众所了解。与此同时，对于PM_2.5的研究也是火热了起来。

PM_2.5可分为一次和二次PM_2.5。一次PM_2.5是由天然污染源和人为污染源释放到大气中直接造成污染的PM_2.5组分，主要包括矿物气溶胶、黑碳和一次有机组分。二次PM_2.5是由大气中某些污染气体组分（如SO₂、NO_X、碳氢化合物等）之间，或这些组分与大气中的正常组分（如O₂）之间通过光化学氧化反应、催化氧化反应或其他化学反应转化生成的PM_2.5组分，主要包括SO₄^2-、NO₄^-、NH₄ 和二次有机组分。E．Mantas等^【1】通过对临近地中海的某大学校园进行系统监测，利用PMF模型分析数据得出：二次无机气溶胶和有机物对PM_2.5质量浓度的贡献率分别约为30.6%和30%，包括交通引起的扬尘对PM_2.5的贡献率为3-5%。黄晓峰等^【2】对2009年深圳大气的PM_2.5来源解析的工作中得出二次硫酸盐和二次硝酸盐对总PM_2.5的贡献率分别为30%和9.3%。任丽红等^【3】对2012年重庆主城区的研究中也得出二次粒子对大气中PM_2.5的贡献比例也达到了30．1%。二次PM_2.5对颗粒物污染的贡献有目共睹，不仅表现在其组分在总PM_2.5的占比的重要性，其危害性也不容小觑^【4】。导致PM_2.5来源多而复杂，主要的大气污染物排放源有分为天然源（自然尘和森林植物释放）和人为源，而人为源中主要有燃料燃烧、工业生产过程排放、交通运输过程中排放、农业活动排放，而黄辉军等^【5】总结在南京主要有地面扬尘、建筑尘、煤烟尘、冶炼尘、汽车尘和二次气溶胶(以硫酸盐气溶胶为代表)。南京的研究发现二次PM_2.5有重要贡献，以代表性的二次气溶胶硫酸盐的贡献率就占总PM_2.5的10.54%。开展南京PM_2.5源解析的工作将为控制治理南京的空气污染，保护南京民众健康提供重要科学依据。由此，展开对二次PM_2.5的来源解析工作迫在眉睫。

南京作为长三角区域重要的经济重镇，是连接苏南和苏北，安徽和江苏的重要交通枢纽和经济中心，其具有代表江南地区经济发展程度的经典性。而近年来南京发生的空气污染事件也是触目惊心。因此，国内对于南京的PM_2.5的源解析研究工作也越来越成熟。然而在南京的二次PM_2.5的源解析工作方面，国内甚至国外都鲜有研究。因此，本文的中心就在于南京市二次PM_2.5的来源解析上面。关于本文的研究目的和内容，第一，重申二次PM_2.5在总PM_2.5中的重要性（2009年1月和8月中国的硫酸盐和硝酸盐的源贡献已经利用源分流示踪法进行了量化测量）^{【6】【7】}。这两个研究展示了二次无机成分在总PM_2.5中的重要性。；第二，研究一次组分对二次组分之间浓度的关系；第三，也是最重要的，对此次二次PM_2.5进行来源解析，分析几大来源对二次PM_2.5的贡献，以明确哪一类或者哪几类污染来源是较为严重的二次PM_2.5贡献源。明确贡献源之后，可以使得政府或相关决策单位更方便做出决策，来平衡好经济发展和污染控制之间的关系，以得到经济-环境效益的最大化。

在这份研究中，我们选取了五种来源类别，分别是能源生产排放源（power）、生活排放源（residential）、工业排放源（industry）、交通运输排放源（transportation）和露天燃烧（open burning）。忽略自然过程的排放，只研究人为活动的贡献，以上五类基本是基本囊括了颗粒物污染的主要产生过程。可以知道，二次污染颗粒是经过一次污染颗粒的再次反应生成的，所以一次颗粒在形成二次PM_2.5的过程中是起到十分重要的“源头”作用的。因此，在研究二次PM_2.5的源解析的同时也应该关注一次污染物的源贡献状况。由此选用的空气质量模型不仅应该能够评估污染物浓度的贡献，也应该兼顾污染物在城市大气中的相互影响过程和各种互相转化过程，包括液相化学过程、非均相过程、气溶胶过程和干湿沉降过程对污染物浓度分布的影响^【8】。

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