Study On The Characteristics Of Changes Of VOCs During Haze Process In Shanghai

(1) Atmospheric particulates and VOCs have important influence on the global natural environment and human health, haze pollution process is related to the VOCs classification and the concentration of the atmosphere. Based on constructing the vehicle-mounted experimental system of on-line monitoring VOCs, a continuous month(from Nov. 1st to 30 th of 2013) of on-line monitoring is performed on 72 types of VOCs(the standard atmosphere is the TO-15 standard atmosphere of Linde company and the sulfur-containing organic stink mixed gas produced by Dalian Date Gas Co., Ltd., mainly including alkane, olefin and arene) in Shanghai atmosphere in order to discuss the VOCs change feature in the haze pollution process and comparative analysis is conducted with the meteorological parameter(wind direction, wind speed and rainfall), 5 kinds of common pollutants in atmosphere(CO, O3, nitrogen oxide, PM2.5 and PM10) and traffic condition; finally the PMF model is applied to perform analysis on the sources of VOCs on haze and non-haze days. The results as follow:(2) A set of positive pressure vehicle-mounted laboratory system equipped with table type TD-GCMS is established in this paper, and the on-line monitoring platform of VOCs is explored in the system. The detected 72 kinds of VOCs quality concentration is the system is in linear relation with the corresponding peak area, which is limited at 0.094-0.800μg/m3, the precision degree(high, middle and low) is lower than 10%, conforming to the relevant detection method requirements.(3) The VOCs types don’t have much difference in the detect atmosphere of haze and non-haze period, mainly including alkane, olefin and arene, the average concentration of VOCs in the monitoring ability during the haze period is 294.8μg/m3; the average at non-haze period is 108.9μg/m3; in all of the VOCs, isoprene has the most obvious characteristics in the haze and non-haze period: the concentration at non-haze day can’t be detected, the concentration is 0.23μg/m3; the concentration at haze day is 0.81μg/m3. The VOCs of 2- methyl amylene, 3- methyl amylene, methyl benzene and normal octane produced by motor vehicles are not obvious in t he haze and non-haze days, which shows that the vehicles has stable contribution for the VOCs in atmosphere. The VOCs concentration is related to the traffic flow at non-haze days, the highly polluted VOCs at haze days are in instantaneity, the average concentration of VOCs is not high, so it’s not scientific for using average daily pollutant concentration to perform characteristic research at the haze and non-haze days.(4) The total VOCs concentration at haze and non-haze days is not strongly related to the wind direction, but the air pollution degree, atmosphere particulate pollutant concentration is highly related to the weather conditions; the VOCs concentration in atmosphere is in negative relation with the wind speed(the relevant coefficient is 0.430), but the atmosphere particulate(PM 2.5, PM10) is in obvious negative relation with the wind speed(the relevant coefficient is respective 0.649 and 0.666); the VOCs concentration at the rainfall period is in the trend of descent, but the concentration of PM2.5 and PM10 is in obvious decease. Therefore, we can know that the influence of wind speed, wind direction and rainfall on the VOCs in the atmosphere is weak than its influence on the particulate concentration in the atmosphere.(5) The VOCs at haze period has small change scope and comparative stability at the peak traffic hour compared to the non-peak traffic hour, which is mainly due to the worse air diffusion condition at haze period and the pollutants from the surrounding enterprises and environment can’t timely diffuse out; therefore, the VOCs pollutant at haze period is mainly from the surrounding enterprises and environment, and the vehicle exhaust is the secondary source for the VOCs pollutants. The concentration of 2- methyl amylene, 3- methyl amylene, benzene, methyl benzene compound in peak traffic hour at non-haze period is obviously higher than the concentration at non-peak traffic hour, which shows that the VOCs in atmosphere at non-haze day is mainly from the vehicle exhaust.(6) Through the PMF source apportionment model we can see that: the largest contribution source in the VOCs at haze day is petrochemical industry, the secondary one is vehicle exhaust; the largest contribution source of the VOCs in atmosphere at non-haze day is vehicle exhaust, and the secondary is petrochemical industry. It’s possibly related to the air diffusion conditions, which are worse at haze day, VOCs pollutants produced by the nearby petrochemical enterprises at the monitoring point can’t be well diffused, so they become the main pollutants; the air diffusion conditions are excellent at non-haze day, the VOCs pollutants produced by the nearby petrochemical enterprises at the monitoring point can be timely diffused, but the point is adjacent to the commercial center, the nearby traffic flow is large, and the exhausted VOCs pollutants become the main pollutants of this area at the period.