西安市城区持久性有机污染物的干湿沉降

Persistent organic pollutants in dry and wet atmospheric deposition of Xi'an

为了确定大气干湿沉降中持久性有机污染物的主要特征及干、湿沉降对大气中污染物去除的相对贡献,选择西安市城区为研究对象,于2014年4—10月在东、西、南、北各区域的一环路和二环路均设采样点,共采集了302个大气干、湿沉降样品。降雨样品经过液液萃取,降尘样品经过超声萃取,使用气相色谱法测定了36种POPs的含量,仅PCB157未检出。结果表明,干、湿沉降样品POPs沉降通量分别为458.78 kg/a和1846.90 kg/a,其中的多环芳烃（PAHs）、多氯联苯（PCBs）和有机氯农药（OCPs）分别占总量的47%-77%、16%-42%和5%-12%。就POPs的空间分布而言,南郊〉北郊〉东郊〉西郊,大气中POPs主要由燃油污染贡献。就POPs的存在特征而言,降雨〉降尘〉径流,湿沉降是大气环境中POPs的主要排除方式。经SPSS分析晴天数、TOC与POPs的相关性得到r〉0.7,因此晴天数和TOC是大气中POPs干湿沉降的主要影响因素。

Xi＇an City was used to investigate the characteristics of POPs in atmospheric deposition,and the contribution to pollutant removal made by dry and wet deposition. At the north,south,east,and west of the first and second ring,302 atmospheric deposition samples were collected from April to October,2014,including dry and wet deposition samples. Wet deposition was extracted using liquid-liquid extraction and dry deposition was extracted using an ultrasound. A total of 36 kinds of POPs were analyzed by gas chromatography,and only PCB157 was not detected. The results showed that the deposition flux consisted of 458. 78 kg / a of dry deposition,and 1 846. 90 kg / a of wet deposition. The concentrations of PAHs,PCBs,and OCPs made up 47% to77%,16% to 42%,and 5% to 12%,respectively,of the total POPs. The spatial distribution of POPs was in the order south〉 north〉 east 〉west,which was mainly due to fuel oil. Rainfall is the main pathway for POP removal. The order of importance was wet deposition 〉dry deposition〉 run-off. The relationship between the antecedent dry weather days,TOC,and POPs was r 〉0. 7 after using SPSS,so they are main factors affecting POP depositions in the atmosphere.