Emission inventory of VOCs from mobile sources in a metropolitan region

Transcription

1 Korean J. Chem. Eng., 23(6), (2006) SHORT COMMUNICATION Emsson nventory of VOCs from moble sources n a metropoltan regon M-Sug Km, Jong Ho Km, Hyeon-Soo Park*, Yle Shk Sun**, Hong-Seok Km**, Kyung Hee Cho*** and Jongheop Y School of Chemcal and Bologcal Engneerng, Insttute of Chemcal Processes, Seoul Natonal Unversty, Seoul , Korea *To21 Co., Lotte-Tower 402, Dongjak Shndeabang-1, Seoul , Korea **Korea Testng and Research Insttute for Chemcal Industry, Gomak 7-6, Gmpo Wolgot, Gyeongg , Korea ***Natonal Insttute of Envronmental Research, Envronmental Research Complex, Kyungseo-dong, Seo-gu, Incheon , Korea (Receved 21 January 2006 accepted 3 July 2006) Abstract Based on methodologes developed by US EPA, European EMEP/CORINAIR, and Australan NPI, and the former emsson nventory n Korea, two methods were appled to 151 vllages n northeastern Seoul, Korea to estmate emsson of VOCs from lne and area vehcle sources dependng on vehcle types wth dfferent fuel types. A dscharge coeffcent method for the lne source on the Eastern man road was calculated by multplyng the emsson amounts per unt of mleage, and a fuel exhaust coeffcent method for the area vehcle sources on other roads was determned as multplyng the emsson rates by the actual consumpton of excess fuel. Results ndcated the methods could be adequate for estmatng the amounts of moble emssons when lmted nformaton on moble emsson s avalable. The methods can be used to develop the emsson model for all VOCs emsson sources (pont and non-pont sources), whch provdes nput data of atmospherc models. Key words: Moble, Vehcle, Emsson, Inventory, Metropols, Road, Toluene, VOCs, Benzene, Xylene, Styrene INTRODUCTION Ar polluton due to O 3 precursors, volatle organc compounds (VOCs) and NO x, has ncreased, prmarly as the result of the rapd ncrease n number of automobles. Moble sources are of concern n terms of developng strateges for reducng ground level ozone across the world. Aardenne et al. [1999] reported data for NO x emssons n Asa durng the perod due to anthropogenc actvty based on the RAINS-ASIA methodology. The rapd growth of NO x emsson was drectly related to the dynamc nature of energy use between road transport and non-road transport n Asa. In 1990 NO x emssons due to transport made up 80-65% of the total emsson n Bangkok, Delh, Jakarta, Manla, and Seoul. It has been known that moble emssons are also a major source of VOCs n urban areas away from ndustral sources [Chan et al., 2002]. Chan et al. [2003] reported on the characterstcs and concentratons of VOCs n roadsde mcroenvronments n metropoltan Hong Kong and compared ther data wth the most developed ctes n Chna, Germany, UK, Greece, Canada, and Brazl. Hong Kong was domnated by aromatc VOCs and VOC concentratons, especally toluene and, to a lesser extent, benzene. Chlornated VOCs n Hong Kong were a lttle hgher than those n other ctes. Tsa et al. [2003] and Bong et al. [2003] reported that sopentane, toluene, m,p-xylene, n-pentane, 2-methylpentane, 3-methylpentane, benzene, n-heptane, and methylheptane were the major VOC components n motorcycle engne exhaust. Snger and Harley showed that fuel use estmates and emsson factors measured from over 60,000 onroad vehcles could be used to calculate stablzed exhaust emssons of 550±90 metrc tons day 1 of VOC n Calforna s South coast Ar Basn durng the summer of These values were hgher To whom correspondence should be addressed. E-mal: jy@snu.ac.kr than offcal nventory estmates for the same perod by factors 3.5± 0.6 for VOC. Meanwhle, the hgh degree of uncertanty and a severe underestmaton of a VOC emsson nventory reported by the Natonal Research Councl [NRC, 1992] may be partally responsble for the lmted success of VOC control strateges across the U.S. durng the last two decades n solvng ground level ozone problems [McLaren and Sngleton, 1996]. To address these questons and to estmate the amounts of emtted VOCs from vehcles, a new emsson nventory technque was adopted on the bass of two parameters, a fuel exhaust coeffcent and a dscharge coeffcent of the dstance covered n a gven tme (mleage). The present study s a part of an ntegrated envronmental management (IEM) project supported by the Korean Mnstry of Envronment and ECO-Technopa-21 (Core Envronment Technology Development Project for Next Generaton) durng the perod The new EI technque was appled for the northeast of Seoul, over all of the Jung-Rang stream, n Korea. Based on the prevous studes cted above and the prorty substance lst developed n the frst step of the IEM project [Km et al., 2005; Chah et al., 2003; Y, 2002], Benzene, Toluene, Xylene, and Styrene (BTXS) were selected as the major aromatc compounds n the present study. 1. Methodology Durng the fuel combuston process of road vehcles, amounts of ar pollutants, emtted nto the ar, depend on the type of vehcle, speed, fuel use, etc. In order to estmate emssons of moble sources on two dfferent road types, the man road and other roads, ths study used two dfferent methodologes developed on the bass of the US EPA, European EMEP/CORINAIR, Australan NPI, and the prevous development of an emsson nventory n Korea. Two major methods, n estmatng the amounts of pollutants emtted from a vehcle, are the fuel exhaust coeffcent and the dscharge coeffcent of the dstance covered n a gven tme (mleage). The former s determned as multplyng the emsson rates (per unt fuel use) 919

2 920 M.-S. Km et al. by the actual consumpton of excess fuel, whle the latter s calculated by multplyng the emsson amounts per unt of mleage (unt dstance covered) by the actual dstance covered (mleage) Dscharge Coeffcent Method The dscharge coeffcent method uses the actual dstance covered (mleage) to estmate the emsson amounts of the pollutants when t s mpossble to determne the amount of the fuel consumpton by the lmted mleages over the target regon. Based on current traffc volume data, the multplcaton of the average traffc volume and the road extenson dstance (RL) wthn the target block determnes the annual total mleage of the vehcle model wthn the target area. Meanwhle, the mleage of the vehcle model s determned by dvdng the total mleages by the current regstered vehcles. Because emsson coeffcent data for each VOC for the total vehcle models are not currently avalable, the present study apples the European emsson coeffcent for each VOC. The followng equaton s used to determne the VOC emsson rate (Kg yr 1 ), E; 1 E = TV VN RL EF R 1000 tvn where, s the vehcle model, TV s the annual traffc volume (vehcles year 1 ), VN s the number of regstered vehcles by the vehcle model, tvn s total regstered vehcles, RL s the road extenson (Km vehcle 1 ), EF s the VOC emsson coeffcent due to the vehcle model (g km 1 ), and R s the mass composton rato of the VOCs. Note that EF s estmated by the average speed wthn the block as a functon of vehcle speed Fuel-exhaust-coeffcent Method Usng regstered vehcles due to the vehcle model related to the fuel type and ther fuel consumpton, the fuel-exhaust-coeffcent method estmates the moble emsson rates (kg yr 1 ) dependng on the fuel consumpton as follows: E =1000 VN DVN F d R tvn where, s the vehcle model related to the fuel type and busness use, DVN s the regstered vehcles for the vehcle model for each vllage n the target area, VN s the regstered vehcles for the vehcle model n the target area, tvn s the total regstered vehcles n the target area, F s the annual fuel consumpton (kl vehchle 1 yr 1 ), d s the fuel densty (kg L 1 ), and R s the mass composton rato of VOCs (kg kg 1 ). All nformaton for ths method was precsely gathered for each vllage. 2. Applcaton of Emsson Inventory Technque All 151 vllages (so called Dong ), over the Jung-Rang stream located n northeastern Seoul, were selected for developng the emsson nventory of a metropoltan regon. The Jung-Rang stream s the longest stream (45.3 km) n Seoul and flows nto the Han Rver. Fg. 1 shows the 3-dmensonal topography of the target area for ths study. The target area has the characterstcs of a local envronment causng ar polluton by non-pont emsson sources (lne and area sources) as well as by pont sources such as ncneraton. The road and the traffc condtons n ths area are a representaton of metropoltan Seoul. In Seoul, traffc actvty, vehcles and traffc volume have greatly ncreased, and road traffc volumes contnue to ncrease due to the avalablty of low cost fuel vehcles. Regstered LPG vehcles have ncreased from 126,948 n 1998 to 228,996 (1) (2) Fg. 1. The target area map: (a) a map of South Korea, (b) a pcture of Northeastern Seoul taken by Satellte, and (c) locatons of the Eastern Man road (sold lne), other roads n the 34 dstrcts of the seven countes ( ), VOCs measurement stes ( ), and the target area, seven countes, of the present study ( ). n 2000 [data, Seoul]. The traffc volumes of LPG vehcles are about 22.7% for prvate automobles. The moble sources n the target area nclude road moble emsson and ral-road moble emsson. In the case of a ralroad vehcle, hazardous compounds are emtted from the fuel combuston durng operaton. The ralroads nclude the Kyong-Won Track, the Kyong- Choon Track, the Jung-Ahng Track, and the Mang-U Track dstrbuted along Jung-Rang stream and aggregate from the Cheong- Ryang-R va the Hu-Kyong. However, the amounts of ralroad e- mssons are comparatvely much lower than those from road mobles. On that account, the focus of the present study was on road moble sources, whch were dvded nto two parts: the Eastern man road sources and other road sources as shown n Fg. 1. The Eastern man road s a representatve road n the area and runs from Yong-B Gyo (brdge) to Nok-Cheon Gyo along the Jung-Rang stream. Other roads are located n seven dstrcts (SungDong-Gu, GwangJn-Gu, Dong- DaeMoon-Gu, JungRang-Gu, SungBook-Gu, DoBong-Gu, and No- Won-Gu) ncludng 34 vllages (among all 151 vllages n the seven dstrcts) along the Eastern man road over the Jung-Rang stream. RESULT AND DISCUSSION The Eastern man road (through 25 vllages) was chosen and consdered as a lne source for the emsson nventory of mobles on the road over the Jung-Rang stream. For the man-road source, the dscharge coeffcent method of the dstance n Eq. (1) was appled to determne the emsson rate of VOCs because fuel consumpton or traffc volume n the target area was not known wth certanty. Table 1 shows the nformaton requred n Eq. (1) to determne the dscharge coeffcent as a functon of vehcles category; the vehcles nclude passenger cars (PC), duty-cars (DC), and duty-trucks (DT) wth three dfferent sze types (lght, medum, and heavy) and wth three dfferent fuel types (gasolne, desel, and LPG). Infor- November, 2006

3 Emsson nventory of VOCs from moble sources n a metropoltan regon 921 s Table 1. Emsson factors for calculatng emsson rates accordng to the two methods gven n Eqs. (1) and (2) Categores of vehcles Vehcle regstraton Fracton of vehcles Emsson coeffcent of Mass composton n Seoul regstraton n Seoul total VOC (g/km)* of VOCs kg/kg Passenger Gasolne 3,493, V = car Desel 4.61V LPG 103, V = Duty-car Lght Gasolne 9, V = Desel 181, V = LPG 63, V = Medum Gasolne V V Desel 7, V V = Heavy Gasolne Desel 12, V = Duty-truck Lght Gasolne 11, V V = Desel 237, V V = LPG 12, V = Medum Gasolne Desel 34, V = Heavy Gasolne Desel 27, V = ,194,443 data from The Mnstry of Constructon and Transportaton [1999]. *European EMEP/CORINAIR data: V s an average speed (km/hr) gven the dstrct, V=41.46 km/hr n the East man road n the year Table 2. Rato of VOC mass composton ( 10 2 ) (Europe EMEP/CORINAIR data) Chemcals Gasolne Desel LPG Chemcals Gasolne Desel LPG Ethane (1) 03 1-Hexene Propane (1) 44 1,3 Hexene n-butane (1) Alkanes C> (1) -Butane 1.5 Benzene n-pentane (1) Toluene Pentane 7.0 o-xylene Hexane 6.0 m,p-xylene Heptane 5.0 Ethylbenzene Octane 7.0 Styrene Nonane 2.0 1,2,3-Trmethylbenzene Alkanes C> (1) 1,2,4-Trmethylbenzene Ethylene (1) 15 1,3,5-Trmethylbenzene Acetylene (1) 22 Other aromatcs C Propylene (1) 10 Aromatcs C> (1) Propadene Formaldehyde Methylacetylene 0.2 Acetaldehyde Butene 1.5 Other Aldehydes ,3 Butadene (1) Acrolen Butene Butenal Pentene 0.5 Benzaldehyde Pentene (1) Acetone maton concernng vehcles was adopted from the Mnstry of Constructon and Transportaton n Seoul [1999]. Usng the European EMEP/CORINAIR data, the emsson coeffcents for total VOC (g km 1 ) were determned as a functon of average speed V for the man-road zone, whch was km hr 1 for the East man road n the year The ratos of VOC mass compostons n Table 2 nclude BTXS values (Benzene, Toluene, Xylene, and Styrene). The fuel-exhaust-coeffcent method n Eq. (2), for estmatng Korean J. Chem. Eng.(Vol. 23, No. 6)

4 922 M.-S. Km et al. Table 3. Vehcles regstered n each county over the target area Passenger car Duty-car Duty-truck Gasolne Desel LPG Gasolne Desel LPG Gasolne Desel LPG Sung-Dong Kwang-Jn Dong-Dae-Moon Jung-Rang Sung-Book Do-Bong No-Won All Table 4. Annual Fuel consumpton (kl vehcle 1 ): Mnstry of Constructon and Transportaton n Seoul [1998] Passenger car Gasolne Desel LPG Non-busness Busness Non-busness Busness Non-busness Busness Duty-car Gasolne Desel LPG Non-busness Busness Non-busness Busness Non-busness Busness Duty-truck Gasolne Desel LPG Non-busness Busness Non-busness Busness Non-busness Busness Fg. 2. Regstered vehcles related to fuel types n selected countes near Jung-Rang stream. the moble emsson from other roads over Jung-Rang stream except the Eastern man road, was appled as a functon of emsson factors such as the number of regstered vehcles, annual fuel consumpton, and so on. Data for regstered vehcles and the annual fuel consumpton n the selected seven dstrcts were obtaned by usng the Seoul data, as reported by the Mnstry of Constructon and Transportaton [1998] and those data are gven n Tables 3 and 4. The vehcles, as gven n Table 4, can be classfed due to vehcle model related to the fuel type. Most vehcles are gasolne powered PC whch makes up almost 70%, whle the desel powered DVs comprse 20% of the total vehcles over the target area (see Fg. 2). To calculate the emsson rates on other roads, we used the regstered vehcles and the annual fuel consumpton as shown n Tables 3 and 4, respectvely. The annual fuel consumpton was obtaned by multplyng the fuel denstes (734.5 g L 1 for gasolne, for desel, and for LPG), and the rato of VOCs mass compostons shown n Table 2. Based on data from Table 1 to Table 4, Fg. 3 shows the emsson estmates of major VOCs, BTXS, emtted from moble sources on the Eastern man road (the lne source) and on other roads (the area sources). On the Eastern man road, PC makes up more than 80% of the total vehcles and the emsson rates from gasolne powered lght-pc are domnant factors. Fg. 3(a) shows values for BTXS emtted from all gasolne-powered PC, and are n the order; toluene, xylene, benzene, and styrene. The emsson rates for toluene are over 8 T yr 1, xylene emssons are over 7 T yr 1, those for benzene are about 4 T yr 1, and emtted styrene s very low. On other roads, the emssons from gasolne powered PCs are almost 87% of the total emssons and the BTXS from the gasolne powered PCs are ordered as shown n Fg. 3(a). When comparng the results wth those from the Eastern man road, the BTXS values are n the same order but the amounts of materal emtted are fve tmes greater. In Fg. 3(b), BTXS emsson rates from Duty-Vehcles (Duty- Car and Duty-Truck) are llustrated accordng to fuel type. The gasolne-powered DV has the same order of BTXS emsson as a gas- November, 2006

5 Emsson nventory of VOCs from moble sources n a metropoltan regon 923 Fg. 3. VOC emssons estmaton due to moble sources on other roads over all the target area usng fuel exhaust coeffcent as a functon of vehcle model and fuel type (a) Emsson rate (kg yr 1 ) from Gasolne powered Passenger Cars and (b) fracton of emsson rates from Duty-Vehcle. olne-powered PC, but the amounts of pollutants emtted are very low compared to a gasolne-powered PC. For the case of the Eastern man road, benzene and xylene are the man components due to desel-powered DV, whle styrene levels are largely dependent on gasolne and less so, about 30%, due to LPG. Toluene s contrbuted equally by gasolne-powered DV and desel-powered DV. Fg. 3(b) also shows that the fracton of emsson by desel-powered DV on other roads s 80-90% of the total DV, and ths value can be compared to the 60-80% for the Eastern man road sources. The total moble emssons n the target area were obtaned by summng the Eastern man road vehcle emssons and other-road vehcle emssons. For both emssons rates from the Eastern man road sources and other road sources, toluene s the domnant compound, almost equvalent to xylene, followng benzene, and styrene, n that order. The amounts of pollutants emtted from other road sources are fve tmes greater when compared to those from the Eastern man road moble sources; the BTXS emsson from the Eastern man road sources s approxmately 14% of the total moble sources, and about 86% of the total moble sources are caused by other road emsson sources. Fg. 4 shows the fracton dfference between BTXS moble emssons and the fracton of BTXS concentraton. BYXS were measured under ambent condtons durng the project perod 2002 from 10 measurement stes located wthn the target area, as shown n Fg. 1, and these BTXS concentratons were used to estmate the dstrbuton of VOCs concentratons. Fg. 4(a) ndcates that the fracton of toluene emtted s 39% of the total BTXS emsson, whle Fg. 4. Comparson of BTXS between emsson estmaton and ambent concentraton measured durng the 2002 from the stes marked n Fg. 1(c). the fracton of ambent toluene concentraton s over 70% of the total ambent BTXS concentratons n Fg. 4(b). 1. Summary and Concluson Two emsson nventory (EI) technques were used to estmate the amounts of pollutant VOCs emtted from vehcles as a part of an ntegrated envronment management (IEM) project supported by the Mnstry of Envronment n Korea and ECO-Technopa-21 (Core Envronment Technology Development Project for Next Generaton). These methodologes for the moble emsson nventory were developed on the bass of the US EPA, European EMEP/ CORI- NAIR, Australan NPI, and usng the emsson nventory developed n Korea. The EI technques were also appled to the northern parts of Seoul, over the Jung-Rang stream. Aromatc compounds, benzene, toluene, xylene, and styrene (BTXS) were chosen as the major VOCs n an urban atmosphere based on the lterature. The two methods for estmatng the amounts emtted from moble sources are the fuel exhaust coeffcent and the dscharge coeffcent of the dstance covered n a gven tme (mleage). The former s determned by multplyng the emsson rates (per unt fuel use) by the actual excess fuel consumpton, and ts applcaton s carred out for VOCs emtted from mobles on other roads (roads except the Man-Road) n seven countes wth 34 dstrcts over Jung-Rang stream, whle the latter s calculated by multplyng the amounts emtted per unt mleage (unt dstance covered) by the actual dstance covered (mleage) and appled to the Eastern man-road emsson from moble sources. The EI technques depend on the vehcle type [passenger car (PC), duty-car (DC), and duty-truck (DT)] related to fuel type (gasolne, desel, and LPG). In the present study, PCs make up more than 80% of the total vehcles and the gasolne powered PCs are almost 70% of the total vehcles over the target area, whle the desel powered DVs comprse 20% of the total veh- Korean J. Chem. Eng.(Vol. 23, No. 6)

6 924 M.-S. Km et al. cles over the target area. The VOCs emssons by the gasolne powered PC are domnant. The total moble emssons of the target area as obtaned by the two methods ndcate that mostly toluene, almost equvalent to xylene, followed by benzene, and styrene, n that order. The amounts emtted from other road sources are fve tmes greater when compared to those from the Eastern man road moble sources; the BTXS emsson from the Eastern man road sources s approxmately 14% of the total moble sources, and about 86% of the total moble sources are caused by other road emsson sources. The present study estmates that moble emsson s manly dependent on fuel consumpton and the numbers of the vehcles. Ths study shows that the moble emsson s clearly the major source of VOC n urban areas away from ndustral sources and that the two methods appled n ths study are possble for estmatng moble emssons from the lne and/or area sources. For further study, real world vehcular estmaton factors (EF) are requred for the accurate vehcular emsson estmaton of non-methane hydrocarbons (NMHC) such as Na et al. [2002] n Seoul. When comparng the moble emsson and ambent concentratons obtaned durng the project perod, the moble emsson does not explan the ambent concentraton. In other words, the ambent concentraton of toluene s sgnfcantly affected by other sources as well as the moble sources. To explan the uncertanty or the accuracy of the VOCs emsson nventory requres consderng not only the moble sources but also all other sources ncludng pont and non-pont emsson sources. It s mportant to estmate emssons accurately because t provdes detaled data of source nformaton, helps to understand the current stuaton of the ar polluton, and reduces the uncertanty of model predcton. NOMENCLATURE d : the fuel densty [kg L 1 ] DVN : the regstered vehcles due to the vehcle model for each dstrct n the target area E : the VOC emsson rate [kg/year] EF : the VOC emsson coeffcent due to the vehcle model [g km 1 ] F : the annual fuel consumpton [kl vehchle 1 yr 1 ] : the vehcle model related to the fuel type and busness use R : the mass composton rato of VOCs kg kg 1 RL : the road extenson [km vehcle 1 ] TV : the annual traffc volume [vehcles year 1 ] tvn (=tvn) : the total regstered vehcles n the target area VN (=VN) : the number of regstered vehcles due to the vehcle model n the target area ACKNOWLEDGMENT We are grateful to the ECO-Technopa-21 project of Mnstry of Envronment, Korea, for fnancal support, and ths research was conducted through the Engneerng Research Insttute (ERI) at Seoul Natonal Unversty, Korea. REFERENCES Aardenne van, J. A., Garmchael, G. R., Levy II, H., Streets, D. and Hordjk, L., Anthropogenc NO x emssons n Asa n the perod , Atmospherc Envronment, 33, 633 (1999). Bong, C.-K., Yun, J.-S., Hwang, I.-J., Km, C.-R. and Km, D.-S., Estmaton of quanttatve source contrbuton of VOCs n Seoul area, J. KOSAE, 19(4), 387 (2003). Chah, S. W., Joo, C. K., Park, H. S., Park, S. J., Km, P. J., Lee, S. M., Cho, K. H. and Y, J. H., Methodology to determne the order of prorty for envronmental pollutants and selecton of major pollutants for metropoltan and ndustral areas, Korean J. Chem. Eng., 41, 357 (2003). Chan, C. Y., Chan, L. Y., Wang, X. M., Lu, Y. M., Lee, S. C., Aou, S. C., Sheng, G. Y. and Fu, J. M., Volatle organc compounds n roadsde mcroenvronments of metropoltan Hong Kong, Atmospherc Envronment, 36, 2039 (2002). Europe. EMEP/CORINAIR Emsson Inventory Gudebook; avalable at Km, M. S., Joo, C. K., Lee, S. M., Km, P. J. and Y, J., Development of a prorty substances lst for ntegrated envronmental management, Korean J. Chem. Eng., 22, 238 (2005). Korea. The Mnstry of Envronment. Emsson Inventory Gudebook for non-pont sources Volume I and II; avalable at McLaren, R. and Sngleton, D. L., Analyss of motor vehcle sources and ther contrbuton to ambent hydrocarbon dstrbutons at urban stes n toronto durng the southern ontaro oxdants study, Atmospherc Envronment, 30(12), 2219 (1996). Na, K. S., Moon, K.-C. and Km, Y. P., Determnaton of non-methane hydrocarbon emsson factors from vehcles n a tunnel n Seoul n May 2000, Korean J. Chem. Eng., 19, 434 (2002). Natonal Research Councl, Rethnkng the ozone problem n urban and regonal ar polluton, Natonal Academy Press, Washngton, Dstrct of Columba (1992). Snger, B. C. and Harley, R. A., A fuel-based nventory of motor vehcle exhaust emssons n the Los Angeles area durng summer 1997, Atmospherc Envronment, 34, 1783 (2000). Tsa, J.-H., Chang, H.-L., Hsu, Y.-C., Weng, H.-C. and Yang, C.-Y., The specaton of volatle organc compounds (VOCs) from motorcycle engne exhaust at dfferent drvng modes, Atmospherc Envronment, 37, 2485 (2003). U.S.EPA.EIIP Document Seres Volumes I- (EPA-454/R ); avalable at Y, J., ICP (Insttute of Chemcal Processes), Seoul Natonal Unversty, Inventory development for ntegrated envronmental management, Seoul, Korea (2002). November, 2006