城市地表灰尘是污染物的“源”和“汇”的载体，在降雨时地表灰尘被雨水冲刷到周边水体，产生水体污染，干燥天气时地表灰尘在风及人类活动的作用下反复悬浮于低空中，对地表空气造成污染，因此，研究地表灰尘中污染物的分布特征具有重要意义。本研究选取我国北方典型城市：大庆（DQ）、哈尔滨（HEB）、吉林（JL）、北京（BJ）、天津（TJ）、唐山（TS）、太原（TY）、济南（JN）、青岛（QD）、洛阳（LY）、西安（XA）、银川（YC）和兰州（LZ）为研究对象，在干燥天气下用毛刷清扫采集地表灰尘样品，用加速溶剂萃取仪提取、气相色谱质谱法测定灰尘中的16种多环芳烃（Polycyclic Aromatic Hydrocarbons，PAHs）浓度，分析PAHs在各城市地表灰尘中的污染水平、PAHs组分及粒径分布特征，PAHs功能区分布特征，在此基础上用特征化和物比值法和主成分分析/多元线性回归法对北方典型城市地表灰尘中多环芳烃进行源解析。本研究主要结论如下：北方典型城市地表灰尘中16种PAHs总浓度（∑PAH16）在1.97-28.2μg/g之间，均值为6.9μg/g，各城市地表灰尘中∑PAH16平均浓度由高到低依次为太原、吉林、济南、兰州、洛阳、西安、哈尔滨、天津、唐山、北京、青岛、银川、大庆；∑PAH16单位面积负荷为76.3-2036.3μg/m2，均值722.9μg/m2，各城市地表灰尘中∑PAH16单位面积负荷量由高到低依次为吉林、太原、哈尔滨、济南、唐山、洛阳、青岛、天津、大庆、北京、西安、兰州、银川。研究地表灰尘中污染物污染程度时，不仅要重视单位质量灰尘中污染物的含量，更不能忽视灰尘质量负荷的贡献。地表灰尘PAHs组分中Acy浓度最低，均值在0.02-0.2μg/g之间，而Phe、Fla和Chr浓度比较高，均值分别为0.5-5.3、0.3-4.6和0.2-2.3μg/g。3、4环含量占总浓度的60%以上，表明北方典型城市地表灰尘中PAHs污染主要是由煤燃烧排放引起的。北方典型城市地表灰尘粒径分布呈现双峰值，双峰分别出现在120-300μm和40-74μm粒径范围。地表灰尘中∑PAH16浓度随着灰尘粒径的增大而呈现减小趋势。PAHs不同组分质量随粒径分布有所差异，可归为两种变化趋势，第1种为2-3环多环芳烃的质量随粒径分布呈双峰型，峰值分别出现在粒径74-120μm和<40μm范围颗粒物上；第2种为4-6环多环芳烃的质量随粒径分布呈单峰型，在粒径<40μm颗粒物上出现峰值。在粒径<40μm颗粒物上，多环芳烃浓度随着分子量的增大呈现增长趋势。∑PAH16质量负荷在各粒径灰尘上分布差异不大，既地表灰尘粒径分布对PAHs质量负荷产生一定影响。因此，在街道清扫时，不仅要提高技术，清除小颗粒物，同时大颗粒物的影响也不容忽视。北方典型城市工业区、商业区、交通主干道、街道、公园和居住区地表灰尘中PAHs浓度依次为2.7-18.3、2.5-38.9、2.0-41.8、1.3-26.8、1.4-7.96和1.3-26.6μg/g，功能区间分布差异性显著，工业区、商业区、交通主干道明显高于居住区和公园。工业区、商业区、交通主干道地表灰尘中PAHs差异不显著，说明工业燃煤源、焦炉源对PAHs的贡献与交通排放对PAHs的贡献相当，PAHs功能区分布差异主要可能是由于PAHs排放源引起的。在前人研究的基础上，本研究结合研究区实际情况，对Ant/(Ant+Phe)比值判源的界值进行了调整，将比值小于0.08判定为石油源，将比值在0.08-0.1之间判定为混合源，将比值大于0.1判定为燃烧源。特征化合物比值Ant/(Ant+Phe)、Fla/(Fla+Pyr)与IND/(IND+BghiP)计算结果显示，研究区地表灰尘PAHs主要来源于煤/生物质的燃烧，汽车尾气和石油泄漏也有不同程度的影响。利用主成分分析法将研究区域地表灰尘PAHs归为焦炉源、燃煤源、汽车尾气源和石油源，并用多元线性回归法计算各源的贡献率，该计算结果对PAHs主要来源的判定与特征化合物比值法判定结果是一致的。

Surface dust in cities is the source and sink of contaminants. It was flushed into the surrounding water bodies in rainy days and resuspended into the atmosphere driven by the wind and human activities in dry period. With the potential contamination to water bodies and atmosphere, it is important to investigation the pollution characteristics of the surface dust in urban area. In this study, 13 cities in north China were selected as the study area, which include Daqing (DQ), Haerbing (HEB), Jilin, Beijing (BJ), Tianjin (TJ), Tangshang (TS), Taiyuan (TY), Jinan (JN), Qingdao (QD), Luoyang (LY), Xi`an (XA), Yinchuan (YC) and Lanzhou (LZ). The dust samples were collected using a brush and a scoop in dry days. PAHs in dust samples were extracted using accelerated solvent extraction (ASE) method and the concentrations were determined by GC/MS. The characteristics of dust mass per unit area, particle size distribution, PAHs concentration in bulk sample, PAHs concentrations in different particle size and PAHs concentrations in different function areas were studied. The Diagnostic ratios and factor analysis followed by multiple linear regression methods were applied for source apportionment. The main results from this study are as follows:The ∑PAH16 concentrations in surface dust ranged from 1.97 to 28.2μg/g, with a mean value of 6.92μg/g. The ∑PAH16 concentrations were obviously different for different cities. The concentration order was TY> JL> JN> LZ> LY> XA> HEB> TJ> TS> BJ> QD> YC> DQ. The ∑PAH16 mass per unit area was in the range of 76.3-2036.3μg/m2, with an average of 722.9μg/m2 and an order of JL> TY> HEB> JN> TS> LY> QD> TJ> DQ> BJ> XA> LZ> YC. The results exhibited that the dust mass play an important role. In terms of the individual PAH composition, Acy concentration was the lowest, with mean concentration of 0.02-0.2μg/g， whereas Phe, Fla and Chr were abundant, the mean concentrations were 0.5-5.3、0.3-4.6 and 0.2-2.3μg/g, respectively. In addition, 3 and 4 ring PAHs were above 60% among the 16 PAHs. This indicated that the coal combustion was the major source of PAHs in surface dust. Dust mass versus diameter emerged bimodal distribution for ∑PAH16. The peak values appeared in 40-74 μm and 120-300 μm ranges. Bimodal distribution was found for 2 and 3-ring PAHs. The peak value appeared in 74-120 μm and <40μm size ranges. While for 4 and 5-ring PAHs, the concentration increased with decreasing dust size. The mass load of tatal PAHs for differents particle size fractions were similar due to the impact of the surface dust particle size distribution, therefore, the urban sweeping vehicles should update the dust sweeping devices to remove not only the fine particles but also the coarser particles.ΣPAH16 concentrations in surface dust at industrial area (2.7-18.3μg/g), commercial area (2.5-38.9μg/g) and Main-road (2.0-41.8μg/g) were much higher than those at park area (1.5-7.95μg/g) and residential area (1.3-26.6μg/g).ΣPAH16 concentrations at industrial area, commercial area and Main-road were in similarity, this indicated coal combustion and automotive combustion had the same contribution for PAHs. The PAHs concentrations in surface dust from different function areas were mainly affected by their source.By investigating the actual situation of the study area and previous study results, this study adjusted the sourse determination ration value of Ant / (Ant + Phe). An Ant / (Ant + Phe) ratio less than 0.08 is decided to be petroleum source. This ratio between 0.08-0.1 indicates mixed source, and this ratio higher than 0.1 means combustion source. Diagnostic rations of Ant / (Ant + Phe), Fla / (Fla + Pyr) and IND / (IND + BghiP) were applied for qualitative source apportionment. Coal and biomass combustions were the major source of PAHs in surface dust of north cities. Liquid fossil fuel combustion and petroleum also play an important role. The factor analysis method indicated that the sources of PAHs included coke, coal combustion, vehicle emission and petroleum. Multiple linear regression method was used for calculating source contribution ratios. The results from factor analysis were in agreement with the results from diagnostic analysis.