The Vehicular Emission Characteristics Of PM_2.5 And Its Metal Elements In Guangzhou

With the rapid growth of vehicle quantity, vehicle emission has become one of the major pollution sources of atmospheric PM2.5 in Guangzhou, which is the main reason of local haze, reduction of visibility and other issues. PM2.5 composition of vehicle emissions is complicated with a lot of harmful metals. Analyze the characteristic of its specific metal composition, estimate its emission factor, calculate vehicle emission inventory of PM2.5 and its metals and calculate particulate matter pollution contributions of vehicle emission to the atmospheric to provide a scientific foundation for the reduction measures of vehicle emission. Therefore, selected the Pearl River tunnel in Guangzhou, vehicle emissions of PM2.5 and metals composition characteristics levels in Guangzhou is analyzed with the measurements of the motor vehicle emissions of PM2.5 and metal elements concentration levels in this paper. In addition, based on the environmental protection department of vehicle exhaust test bench, 7 types, a total of 163 units in Guangzhou vehicle exhaust emission of the mass concentration of different diameter particles and emission factors are studied. The main results are as follows:(1) The average synthesis emission factors of PM2.5 and PM10 in the pearl river tunnel(including tailpipe exhaust and non-tailpipe emission) respectively: in summer, 57.8 ± 40.7 mg·km-1·veh-1,97.2 ± 65.0 mg·km-1·veh-1; in autumn, 85.0 ± 84.8 mg·km-1·veh-1,137.5 ± 90.4 mg·km-1·veh-1.The sequence of PM2.5 synthesis emission factors of different vehicles: large duty vehicles >bus >taxi > light duty vehicles;The sequence of PM2.5 synthesis emission factors of different fuel vehicles: diesel vehicles> LPG vehicles > gasoline vehicles.(2) The sequence of total metals synthesis emission factors in PM2.5 of different vehicles: large duty vehicles >bus > light duty vehicles >taxi; the synthesis metal emission factor of large duty vehicle is about 1.7 times of buses and 7.4 times of light duty vehicles, 12.0 times of the taxi. According to the specific metal, the sequence of synthesis emission factor is Na > Sn > Fe > Ca > Zn > Mg > K > Ba > Cu > Pb > Mn > Sb > Cr > Ni > Se > Cd > Hg > As.(3) Using logistic Sigmoidal growth curve fitting and vehicle bench experiment method, 7 types of vehicle exhaust emissions of different diameter particles mass concentration distribution function and emission factor distribution function are obtained. Based on those functions, PM2.5 mass concentration and emission factors of single car can be estimated by vehicle bench experiment which are in the condition of the national motor vehicle exhaust emission test. And the sequence of PM2.5 mass concentration is as following: light duty diesel vehicle > light duty diesel truck > large duty diesel vehicle > large duty diesel truck > LPG bus > light duty gasoline vehicle> LPG taxis. The sequence of emission factor : large duty diesel truck > large duty diesel vehicle > light duty diesel vehicle >light duty diesel truck > LPG bus > light duty gasoline vehicle>LPG taxi; According to fuel types, diesel fuel vehicle emission factor is the highest, following the LPG fuel cars, then that with gasoline fuel.(4) The total vehicle emissions of PM2.5 is 10010 tons in Guangzhou 2013 with 7120 tons of tailpipe exhaust emissions of PM2.5 and 2880 tons of non tailpipe emissions. The sequence of different types of vehicle exhaust emission is: large duty diesel truck > large duty diesel vehicle > light duty diesel vehicle >light duty diesel truck > LPG bus > light duty gasoline vehicle>LPG taxi, of which, diesel vehicle emissions is higher than that of LPG and gasoline vehicles. Large duty vehicle annual emissions accounts for 68.14% of all vehicles emissions, and taxi emission accounts for 1.99%.(5) The total vehicle emissions of metals is 1300 tons in Guangzhou 2013, including 780 tons from large duty vehicles, 400 tons from light duty vehicles, 76 tons from buses, and 33 tons from taxis. It’s worth noting that, seven kinds of metal elements in order of priority control emissions in sequence: Cu(20 tons), Pb(11 tons), Cr(4.1 tons), Ni(1.6 tons), Cd(1.1 tons), As(0.2 tons), Hg(0.19 tons). Totally 37 tons of metal is collected, of which large duty vehicle emissions is 23 tons, accounting for 61%.