南昌地铁细颗粒物金属元素特征及其来源解析

Source apportionment Of PM_(2.5) in Nanchang subway station

为探明地铁细颗粒物(PM_(2.5))的金属元素特征及来源,在南昌地铁一号线瑶湖西站、八一馆站和双港站的售票处、站台、车厢及站外(背景值)采集了108个PM_(2.5)样品,进行元素特征分析。结果表明,除Al元素浓度在站外最高外,其它各金属元素含量皆在车厢中最高,其次是站外、售票处和站台。各采样点的Fe元素浓度变化较大,车厢中Fe浓度略高于站台,是售票处及站外平均浓度的3.5~3.7倍和10.9~11.5倍。八一馆Fe和Mn浓度最高,双港站As、Pb浓度最高,瑶湖西站和双港站的Hg浓度最高。富集因子法结果显示,八一馆富集程度最高、瑶湖西最低,站内3个采样点中PM_(2.5)受人为因素影响程度排序为:站台>售票处>车厢,其中Fe、Mn和Cu元素受人为影响最为严重。聚类分析发现17种元素中有3大组元素各组份间有较好的相关性,对应着不同类别的来源,而Co、Hg和Cd与其他元素之间的相关性较差,可能与前3组元素有着不同的来源。PMF和PCA解析地铁PM_(2.5)得到4个相同来源,分别为扬尘(含土壤、道路、施工)、室外交通源、室外工业源和车轮轨道摩擦源。在两种分析结果中,各源所占的比重有所不同,但室外源总贡献率都约占80%,具有较好的一致性。

PM_(2.5) in underground subways were usually several times higher than outdoor,it is critical to identify and quantify the source of PM_(2.5) which contributes improving indoor air quality.PM_(2.5) particles samples were collected at three specific sampling sites which were ticket counter,platform,subway carriage and outside the station entrance,from three stations in Nanchang metro.17 metal elements(Fe,Al,Mg,Na,K,Ca,Ba,Cu,Zn,Cd,Pb,Co,Cr,Mn,V,Ti,Hg and As)in 108 samples were analyzed by ICP-MS.Mean concentrations of metals in PM_(2.5)were the highest in the carriage,followed by outside the station,ticket office and platform,except for element Al which showed the highest concentration in the outside atmosphere around subway entrances.Fe concentrations varied considerably in three sampling sites,it was slightly higher in the carriage than in the platform,and it was 3.5~3.7 times and 10.9~11.5 times of at the ticket office and outside the station,respectively.The maximum values of Fe and Mn in PM_(2.5)were found in Bayi memorial,while As and Pb in Shuanggang,Hg in Yaohu Lake West and Shuangguang stations.High enrichment factors of elements in PM_(2.5) were obtained from Bayi memorial station and Shuanggang station.PM_(2.5) in platform was affected most seriously by anthropogenic impact,followed by in ticket counter and subway carriage.Furthermore,Fe,Mn,and Cu were of most severity by anthropogenic influence within 17 elements.Clustering analysis presented that there were three groups of metal elements which had great correlativity within groups,however,Co,Hg and Cd barely had correlation with others,which indicated diverse source from former-mentioned groups.Four physically interpretable factors contributed to the subway PM_(2.5) pollution at the sampling sites were resolved by PMF:traffic(27.1%),industry(49.1%),soil and road dust(2.2%)and rail,wheel and brake wear(21.6%).The PCA results confirmed the same four source factors which explained 91%of the total data variance,corresponding contribution rates were 39.1%,10.4%,22.7%and 18.8%,the total contribution of outdoor sources by PCA and PMF were both about 80%.