高速公路沿线PM2.5中重金属污染特征

Pollution Characteristics of Heavy Metals in PM2.5 Near Highway

为研究高速公路沿线PM2.5中重金属的污染特征,于2018年3~8月分3次集中采集南昌市周边3条高速公路(昌樟、昌铜和温厚)的服务区、收费站、隧道和公路沿线的PM2.5样品,运用电感耦合等离子体质谱联用仪(ICP-MS)监测了PM2.5中6种重金属(Cu、Zn、Pb、Cd、Cr和Ni)浓度,分析其污染状况和分布情况,并利用地累积指数法、潜在生态风险指数法评价其污染特征、潜在生态危害程度.结果表明,3条高速公路服务区和收费站的PM2.5和PM2.5中重金属均未表现出显著差异.高速公路沿线中PM2.5和PM2.5中的重金属显示为特长隧道>长隧道>公路沿线、服务区和收费站,重金属浓度从高到低依次为Zn(3.8μg·m^-3)、Pb(10.2×10^-2μg·m^-3)、Cr(6.8×10^-2μg·m^-3)、Cu(3.5×10^-2μg·m^-3)、Ni(1.5×10^-2μg·m^-3)和Cd(0.1×10^-2μg·m^-3).不同月份PM2.5及PM2.5中重金属浓度的显著差异可归结为温度和降水的影响.其中PM2.5的浓度与温度呈反相关,而PM2.5中Zn浓度与温度呈极显著正相关,主要是由于温度升高加重轮胎磨损和金属腐蚀.高速公路PM2.5中重金属污染程度和潜在生态危害程度表现为Zn和Cd>Pb>Cu>Ni和Cr,其中Zn和Cd污染及危害程度是评价标准中最严重的等级,大气污染防治计划应着重考虑交通源的Zn和Cd污染.

In this study,we evaluate the pollution characteristics of heavy metals in particulate matter with diameters less than 2.5 μm (PM2.5 ) near highways.Three rounds of cluster sampling of PM2.5 were conducted on three highways,Changzhang,Changtong,and Wenhou,in peri-urban areas near Nanchang from March to August 2018.The sampling sites included service areas,toll stations, tunnels,and areas near the highway.The concentrations of six heavy metals including Cu,Zn,Pb,Cd,Cr,and Ni in PM2.5 were analyzed using inductively coupled plasma mass spectrometry (ICP-MS).The pollution and distribution of heavy metals in PM2.5 near the highway were analyzed,and that pollution characteristics and the level of possible ecological jeopardy were assessed by using the Geoaccumulation Index and Potential Risk Index methods.No significant difference was observed in PM2.5 or in heavy metals in PM2.5 along highways with different traffic flow,but they differed significantly in among highway settings in the following order:super-long tunnels > long tunnels and area near the highway > service areas and toll stations.The heavy metal concentration in highways decreased in the following order:Zn (3.8 μg·m^-3 )> Pb (10.2 × 10^-2μg·m^-3 )> Cr (6.8 × 10^-2μg·m^-3 )> Cu (3.5 × 10^-2μg·m^-3 )> Ni (1.5 × 10^-2 μg·m^-3 )> Cd (0.1 × 10^-2 μg·m^-3 ).In accordance with the influence of temperature and precipitation,PM2.5 and heavy metals in PM2.5 showed significant variations among the monitoring months.The PM2.5 concentration had a significant negative correlation with atmospheric temperature.We observed that PM2.5 concentration was significantly lower from May to August than from March to April.The Zn concentration in PM2.5 was more significant from May to August than from March to April.Pearson analysis showed a significant positive correlation between Zn in PM2.5 with atmospheric temperature because elevated temperatures could aggravate wear and tear and metallic corrosion,which then prompts the emission of Zn.According to the Geoaccumulation Index and Potential Ecological Jeopardy Index,the level of pollution associated with heavy metals of PM2.5manifested in the following order:Zn and Cd > Pb > Cu > Ni and Cr.The pollution and degree of jeopardy associated with Zn and Cd were the most severe in the assessment criteria;therefore,the pollution by these elements and the sources of traffic should be noted in air pollution control plans.Super long tunnels,long tunnels,and areas near highways showed greater levels of pollution and higher potential ecological jeopardy than service areas and toll stations.The degree of pollution in densely populated service areas and toll stations was consistent across partially urban areas.