城市环境空气非甲烷总烃浓度特征及其与气象要素的关系--以烟台为例

Characteristics of Total Non-Methane Hydrocarbon Concentration in Urban Ambient Air and Its Relationship with Meteorological Elements:A Case Study of Yantai

非甲烷总烃(non-methane total hydrocarbons,NMHCs)作为挥发性有机物(volatile organic compounds,VOCs)的重要组成部分,具有强烈的光化学活性,在一定程度上可以反映城市环境空气VOCs的总体污染情况。为研究烟台市区NMHCs特征,在深入探讨2021年烟台市芝罘区NMHCs日浓度随时间变化特征的基础上,系统分析了NMHCs浓度时空分布特征以及不同气象要素对NMHCs浓度的影响。结果表明:甲烷日浓度数值稳定,NMHCs(以碳计)日均浓度年度变化呈典型单峰型,高浓度值出现在5—7月。春、夏两季NMHCs浓度约为秋、冬两季浓度2.5倍,具有明显的季节特征。NMHCs浓度与日均温度、相对湿度、气压呈现较高相关性,首次考察了日均温度和相对湿度对NMHCs浓度的综合影响。风向、风速对局部地区NMHCs的扩散补充具有很大的影响。各因素对NMHCs浓度的影响为气压>相对湿度>气温。在周五至周一、高日均温度、低相对湿度、低气压等情况下易出现相对较高浓度NMHCs。通过本研究可以达到对城市环境空气NMHCs浓度时空分布特征的初步了解,为进一步开展大气污染物防治工作奠定基础。

As an important component of volatile organic compounds(VOCs),non-methane total hydrocarbons(NMHCs)have strong photochemical activity,which can simply reflect the overall pollution of VOCs in urban air to a certain extent.The temporal and spatial distribution characteristics of NMHCs concentration and the influence of different meteorological factors on NMHCs concentration were systematically analyzed based on the discussion of the temporal variation characteristics of the daily NMHCs concentration in Zhifu district,Yantai City in 2021.The results show that the daily methane concentration is stable,and the annual variation of daily NMHCs concentration(measured in carbon)shows a typical unimodal pattern with higher values appearing from May to July.NMHCs concen-tration in spring and summer is about 2.5 times of that in autumn and winter,showing obvious seasonal characteristics.NMHCs con-centration is highly correlated with daily temperature,relative humidity and pressure,and the combined effects of average daily temper-ature and relative humidity on NMHCs concentration were investigated for the first time.Wind direction and wind speed show great in-fluences on the diffusion and replenishment of NMHCs in local areas.The influence of each factor on NMHCs concentration is pressure>relative humidity>daily temperature.A relatively high NMHCs concentration is likely to occur under conditions of from Friday to Monday,high daily temperature,low relative humidity and low atmospheric pressure.This study can achieve a preliminary understand-ing of the spatial and temporal distribution characteristics of NMHCs concentration in urban air environment,and lay a foundation for further air pollutant prevention and control work.