宁波市大气挥发性有机物污染特征及关键活性组分

Pollution Characteristics and Key Reactive Species of Ambient VOCs in Ningbo City

于2010年冬、春、秋三季,在宁波市3个采样点(市区、镇海站、北仑站)进行大气VOCs(挥发性有机物)样品的采集与分析,并对36种大气VOCs组分进行测量,分析宁波市大气VOCs组分组成及其时空分布特征.用各组分的·OH反应速率表征其化学反应活性,以识别宁波市大气VOCs的关键活性组分.结果表明:宁波市ρ(VOCs)(36种大气VOCs组分的平均质量浓度)在3个季节的平均值为198.2μg/m3,主要成分为烷烃(48.6%)、芳香烃(33.6%)、烯烃(17.8%).ρ(VOCs)的季节变化表现为冬季(298.5μg/m3)>秋季(174.1μg/m3)>春季(122.0μg/m3),空间上表现为市区(161.3μg/m3)<镇海(225.0μg/m3)<北仑(208.2μg/m3).宁波市大气VOCs的化学组成相对稳定,·OH平均反应速率常数和乙烯相当,总化学反应活性较强;对化学反应活性贡献最大的是烯烃,其体积混合比约占VOCs体积混合比的22%,但对VOCs化学反应活性的贡献达64%以上;关键活性组分为1-丁烯、反-2-丁烯、间,对-二甲苯、乙烯和戊烯.

Ambient volatile organic compound （VOCs） samples were collected from three sites （urban area, Zhenhai and Beilun） in Ningbo during 2010. A total of 36 VOC species were determined. The chemical composition and spatiotemporM variations of ambient VOCs were investigated. Key reactive species of VOCs were identified based upon OH radical reaction rate （L^OH ）. The average mass concentration of the total VOCs （sum of 36 VOCs） was 198.2 μg/m^3, and the major components were alkanes （48.6%）, aromatics （33.6%） and alkenes （17.8%）. Seasonal concentrations of the total VOCs （p（VOCs）） were ordered as winter （298.5 μg/m^3） 〉 autumn （174. 1 μg/m^3） 〉 spring （122.0 μg/m^3）. p（VOCs） in the urban area （161.3 μg/m^3） was lower than those in Zhenhai （225.0 μg/m^3 ） and Beilun （208.2 μg/m^3 ）. The relative compositions of the total VOCs were stable. Having the similar L^OH to ethylene, the chemical reactivity of total VOCs was relatively strong. Alkenes, being only 22% of the mixing ratio of VOCs, contributed the most to L^OH and accounted for over 64% of chemical reactivity. The key reactive species of ambient VOCs were l-butene, trans-2-butene, m, p-xylene, ethylene and pentene.