兰州市空气PM_(2.5)中四种水溶性无机盐含量及季节性变化分析

目的通过对兰州市空气中PM_(2.5)监测成分进行研究分析,目的是发现主要污染成分和污染季节,为政府防控措施的制定提供参考依据。方法 2015年分别在兰州市城关区和西固区2个监测点采集大气细颗粒物(PM_(2.5))样品,分析大气细颗粒物(PM_(2.5))及四种水溶性无机盐的含量,并对季节性变化趋势进行分析。结果城关区和西固区的PM_(2.5)的含量差异无统计学意义(Z=-1.932,P=0.053),再分别对各个区四个季度的四种离子含量进一步统计分析,城关区PM_(2.5)中硫酸盐在四个季度含量无统计学意义(HC=9.793,P=0.020),含量在10.9~15.5μg/m~3之间,其他3种离子含量有统计学意义,其中城关区硝酸盐冬季最高,为11.8μg/m~3,秋季最低,为2.80μg/m~3;氯离子春季最高,为4.62μg/m~3,夏季最低,为2.12μg/m~3;铵盐春季最高,为1.09μg/m~3,秋季最低,为0.099μg/m~3。西固区PM_(2.5)中硫酸盐在四个季度含量无统计学意义(HC=10.841,P=0.013),含量在11.5~15.7μg/m~3之间,其他3种离子含量有统计学意义,其中西固区硝酸盐冬季最高,为15.6μg/m~3,夏季最低,为2.32μg/m~3;氯离子冬季最高,为5.28μg/m~3,夏季最低,为2.10μg/m~3;铵盐春季最高,为1.13μg/m~3,夏季最低,为0.12μg/m~3。结论 2015年兰州市城关区和西固区PM_(2.5)中四种水溶性无机盐含量无明显差异,但是两个区中四种水溶性无机盐离子除硫酸盐外其他3种水溶性无机盐离子季节性变化明显,整体春冬季高于夏秋季,污染水平有差别。需要我们重视不同季节大气污染,制定相应的污染防控措施。

A cross-section study of the seasonal features of PM2.5and inorganic components in Lanzhou City

Objective To analyze the inorganic components of PM2.5 in Lanzhou,Gansu Province,and to identify the major pollutants and pollution seasons,in order to provide reference for the municipal government to control air pollution.Methods Air samples were collected from 2 surveillance sites in Chengguan District and Xigu District of Lanzhou in 2015.The PM2.5 and 4 types of inorganic components were detected to reveal their seasonal trends.Results No significant difference in the concentration of PM2.5 was observed between samples collected from the 2 sites(Z=-1.932,P=0.053).In samples collected from Chengguan District,the concentration of sulphate was not significantly different(HC=9.793,P=0.020)among 4 seasons,ranging from 10.9 to 15.5 μg/m3.The concentrations of nitrate salt,chloride ion and ammonium salt were significantly different(P<0.05)among 4 seasons.The concentration of nitrate salt was the highest in the winter(11.8 μg/m3),and the lowest in the autumn(2.80 μg/m3).The concentration of chloride ion was the highest in the spring(4.62 μg/m3),and the lowest in the summer(2.12 μg/m3).The concentration of ammonium salt was the highest in the spring(1.09 μg/m3),and the lowest in the autumn(0.099 μg/m3).In Xigu district,the concentration of sulphate was not significantly different(HC=10.841,P=0.013)among the 4 seasons,ranging from 11.5 to 15.7 μg/m3.There were significant differences in the concentrations of nitrate salt,chloride ion and ammonium salt(P>0.05).The concentration of nitrate salt was the highest in the winter(15.6 μg/m3),and the lowest in the summer(2.32 μg/m3).The concentration of chloride ion was the highest in the winter(5.28 μg/m3),and the lowest in the summer(2.10 μg/m3).The concentration of ammonium salt was the highest in the spring(1.13 μg/m3),and the lowest in the summer(0.12 μg/m3).Conclusions The concentrations of the 4 types of inorganic components in PM2.5 are not significantly different between the 2 districts.The concentrations of nitrate salt,chloride ion and ammonium salt have obvious seasonal trend through 2015.Hence,the measures to prevent air pollution should accord with the seasonal characteristics.