声音采集器中文摘要
目的：探讨兰州市城关区和西固区（以下简称两区）PM2.5的污染特征、化学组成特征、浓度变化规律及空间差异；初步解析PM2.5的主要污染来源。 方法：搜集兰州市2015年PM2.5质量浓度和日常气象监测资料；应用大气TSP智能中流量采样器采集和测定兰州市两区采样点PM2.5样品，应用离子谱法检测PM2.5中的水溶性离子，应用电感耦合等离子体质谱仪检测PM2.5中的重金属元素，应用高效液相谱法检测PM2.5中的多环芳烃（PAHs）；对收集到的PM2.5成分数据进行非参数检验和相关性分析，构建主成分分析-线性回归模型（PCA-MLR）。 肩扛式摄像机结果：
1. 兰州市2015年PM
2.5污染现状
PM2.5年平均质量浓度为51.71 μg/m3，超过国家二级标准限值0.48倍，变化范围在19~147 μg/m3。全年365 d中约有七分之一时间PM2.5污染浓度超标。PM2.5质量浓度有明显的时空分布特征：西固区>城关区（P <0.05），采暖期>非采暖期（P <0.01），冬季>春季>秋季>夏季（P <0.01）。
2. 兰州市两区采样点PM2.5化学组成特征及差异
（1）两区PM2.5污染特征。采样期间两区PM2.5质量浓度水平波幅较大，夏季和非采暖期表现为：城关区>西固区（P<0.01）。在同一地区，PM2.5的质量浓度水平在不同时期差异有显著性，表现为：冬季>春季>夏/秋季（P<0.01），采暖期>非采暖期（P<0.01）。
（2）两区PM2.5化学组成及整体变化特征。两区PM2.5化学组成浓度由高到低次序一致，为：水溶性离子>重金属>PAHs，其中PAHs的总质量浓度地区差异显著：城关区>西固区（P<0.05），而重金属和水溶性离子的总质量浓度无显著地区差异（P>0.05）。
（3）两区PM2.5水溶性离子污染特征。两区PM2.5中4种水溶性离子的平均
提花机质量浓度从高到低排序一致，表现为：SO2－
4>NO
3
>Cl－>NH+
4
，且离子之间呈显著楼顶钢筋如何防锈
正相关（P<0.01）；同一地区4种水溶性离子浓度的时间分布差异显著，表现为冬季高于其他季节（P<0.05），采暖期>非采暖期（P<0.01）。
防喷网
（4）两区PM2.5重金属污染特征。两区PM2.5中7种重金属元素含量由高到
低次序基本一致，为：Al>Pb>Mn>As>Sb/Cd>Tl；全年As污染超标严重，分别超过了国家年平均浓度限值的0.89倍（城关区）和0.88倍（西固区）；城关区Cd、Pb、Mn的质量浓度高于西固区（P<0.05）；同一地区7种重金属元素的质量浓度均存在季节差异（P <0.05），且不同种金属元素的季节变化趋势各不相同。
（5）两区PM2.5PAHs污染特征。两区PM2.5中14种PAHs的主要组分是：BbF、Flua、Ant、Pyr、Nap、Chr、DBahA和BaA；采样期间BaP超标严重，分别超过了年平均浓度限值的1.21倍（城关区）和0.85倍（西固区）；城关区Nap 和IcdP的质量浓度高于西固区（P <0.05）；在同一地区，大部分PAHs单体的质量浓度存在季节差异（P <0.05），且季节变化趋势各不相同。
3. 兰州市两区PM2.5污染来源初步分析
城关区主要污染来源是燃煤/交通混合污染，其次为土壤扬尘和生物质燃烧源；西固区的污染来源较为
复杂，除了燃煤/交通混合污染源和土壤扬尘污染源之外，工业污染源、工业/燃煤混合污染源及二次污染源也占有一定比例。
结论：
（1）兰州市PM2.5及其化学组成污染形势依然严峻，且存在明显的时空分布差异，应针对性地加强对突出源贡献以及采暖季节的PM2.5监测和预防控制，加强控制As污染和BaP污染，减少健康风险。
（2）兰州市城关区的主要污染来源是燃煤/交通混合污染，西固区的污染源较为复杂，有关政府部门应当进一步加大兰州市空气污染监测，重视机动车辆尾气排放和燃煤燃烧等问题的治理并出台相应的控排、限排措施，同时针对西固区复杂多变的PM2.5污染来源制定相适应的多措施污染防治策略，以确保兰州市空气质量较好较快地向绿城市转变。
关键词：PM2.5，化学组成，来源解析
Pollution Characteristics and Source Analysis of PM2.5 in Chengguan and Xigu Districts of Lanzhou City
Abstract
Objective: To study the pollution characteristics, the chemical compositions, the concentration varying patterns and spatial distribution of PM2.5in Chengguan and Xigu Districts (hereinafter referred to as two districts) of Lanzhou City. To preliminarily analyze the major sources of PM2.5 pollution.
Methods: Collecting PM2.5 concentrations and routine meteorological data of Lanzhou city in the year 2015. PM2.5 samples were gathered and determined from Chengguan and Xigu Districts; The water-soluble ions in PM2.5 samples were determined by ion chromatography; The heavy metal elements in PM2.5 samples were determined by inductively coupled plasma mass spectrometer; The polycyclic aromatic hydrocarbons in PM2.5were detected by high performance liquid chromatography. The data collected were analyzed by nonparametric test and correlation analysis. The sources of PM2.5 were analyzed by principal component analysis-linear regression model (PCA - MLR).
Results:
1. The overall variation characteristics of PM
2.5 in Lanzhou, 2015
The annual average PM2.5 concentration was 51.71 μg/m3, which was 0.48 times over than the secondary standard limited value of our country. It’s range of variation was between 19~147 μg/m3. One seventh of 365 days in 2015 failed to meet the standards of PM2.5 daily mean value. The average PM2.5 concentration of Lanzhou varied in different areas and different time, that was Xigu District > Chengguan District(P<0.05), and heating period > normal period (P<0.01), and Winter > Spring > Autumn > Summer (P<0.01).
2. The chemical compositions and characteristics of PM2.5 in two districts
(1) The pollution characteristics of PM2.5 in two districts. During the sampling time, PM2.5 concentrations of two districts changed deeply. PM2.5concentration in Chengguan District was higher than Xigu District during Summer and Non-heating period (P< 0.01). In the same district, PM2.5concentration varied in different periods, usually Winter > Spring > Autumn/Summer (P<0.01), and heating period > normal period (P<0.01).
(2) The chemical compositions and the overall variation characteristics of PM2.5 in two districts.
The average concentrations of different chemical constituents in PM2.5 showed the same order, water soluble ions > heavy metals > polycyclic aromatic hydrocarbons (PAHs). The total mass conce
ntrations of PAHs in PM2.5 had an obvious spatial distribution, Chengguan District > Xigu District (P<0.05). While the total mass concentrations of the other two kinds of chemical constituents in PM2.5 had no difference of spatial distribution (P>0.05).
(3) The pollution characteristics of water soluble ions in PM2.5. The average concentrations of
4 kinds of water soluble ions in PM2.
5 from high to low were: SO2－
4>NO
3
>Cl－>NH+
4
. In the same
area, there was a significantly positive correlation among 4 kinds of water-soluble ions (P<0.01), and
the pollution of water soluble ions were most serious in winter (P<0.05) and heating period (P<0.01).
(4) The pollution characteristics of heavy metal elements in PM2.5. The contents of 7 heavy metal elements in PM2.5 were Al > Pb > Mn > As > Sb/Cd > Tl. During sampling period, As was a standard exceeded pollutant whose average mass concentrations were 0.89 and 0.88 times higher than national limits in Chengguan District and Xigu District respectively. The mass concentrations of Cd, Pb and Mn were higher in Chengguan District than Xigu District (P<0.05). In the same area, the mass concentrations of 7 PM2.5 heavy metal elements had seasonal differences (P<0.05), and each kind of metal elements had a different seasonal changing trend.
(5) The pollution characteristics of PAHs in PM2.5. The key components of PAHs were BbF, Flua, Ant, Pyr, Nap, Chr, DBahA and BaA. During sampling period, BaP exceeded bid badly. The average mass concentrations of BaP were 1.21 and 0.85 times higher than national limits in Chengguan District and Xigu District respectively. The mass concentrations of Nap and IcdP were higher in Chengguan District than Xigu District (P<0.05). In the same area, the mass concentrations of some PAHs had seasonal differences (P<0.05), and each kind of PAHs had a different seasonal changing trend.
3. The preliminary analysis of PM2.5 pollution source
The primary pollution source in Chengguan District was a mixed pollution of coal and traffic, followed by soil dust and biomass burning source; The pollution sources of Xigu District were relatively complex, including the mixed pollution of coal combustion, traffic emission, and soil dust pollution, while the industrial pollution, as well as a secondary pollution sources also played a big part.
Conclusion:
(1) The pollution of PM2.5 as well as its chemical compositions were still grim in Lanzhou, and they varied in different time and space. The government should strengthen the PM2.5 monitoring and
preventing of Xigu District during the heating period. Meanwhile, the government should pay special attention to control As pollution and BaP pollution, to reduce health risks.
(2) The primary pollution source in Chengguan District was a mixed pollution of coal combustion and traffic emission, while the pollution sources of Xigu District was relatively complex. So the relevant government departments should further strengthen the monitoring of air pollution in Lanzhou city, attach great importance to the governance of issues like motor vehicle emissions and coal combustion, etc. And some emission control and limitation measures should be introduced. At the same time, in view of the complex PM2.5 pollution sources in Xigu District, more measures should b
e designed to meet the needs, and to ensure that the air quality could change better, and make Lanzhou city soon become a green city.
大灯清洗装置Key words: PM2.5，Chemical composition，Source apportionment
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