Located at the heart of the Korean Peninsula, Seoul is surrounded by high mountains including Bukhansan, Dobongsan, and Gwanaksan, thus forming a sort of basin which inhibits air dispersion by weak winds. Recently, along with the population increase in the metropolitan area, air pollutants generated by China’s industrialization have affected the region. With regard to the condition of Seoul’s artificial environment, its population has increased sharply since 1965, with more than 10.36 million inhabitants as of 2014. Meanwhile, the number of automobiles, the main cause of air pollution, increased from 450,000 in 1985 to 3,010,000 in 2014, showing a 6.7-fold increase.

Aside for days when yellow dust storms occur, the annual PM10 concentration in Seoul has shown a decreasing trend since 2003, with a fine-dust concentration of 44 ㎍/m3 as of 2014. Fine dust shows a seasonal pattern: its concentration is highest in the spring due to frequent yellow dust storms, followed by winter, which is characterized by a highly stagnant atmosphere frequency caused by heating and radiative cooling. The concentration of fine dust is lowest in the summer, when there is a high amount of rainfall.

To prevent the environmental damages caused by fine dust, protect public health, and create a comfortable living environment, the national government has established air quality standards and ensured adequate maintenance of air quality in Seoul despite the ongoing changes in local environmental conditions. In 1993, fine dust (PM10) was included in the national air quality standards for the first time.

In addition, with the revision of the Environmental Policy Framework Act on December 4, 2006, an enhanced standard (compared to previous environmental standards) that has been applied since January 1, 2007, while ultra-fine dust (PM2.5) was added as a new evaluation item in 2015.

Table 1. National and Seoul Air Quality Standards

Regarding the atmospheric environment of the capital area, the concentration of fine dust, which could cause lung cancer and premature death, is twice that of Tokyo. The social costs due to air pollution amount to a staggering KRW 12 trillion per year, with the number of premature deaths caused by fine dust estimated to reach 20,000 per year by 2024. As fine dust - which, as mentioned earlier, is harmful to the human body - is mainly generated by diesel vehicles, it is necessary to implement measures aimed at reducing the level of fine dust in the atmosphere in Seoul by targeting diesel vehicles; therefore, measures targeting diesel vehicles with the aim of reducing fine dust levels have been promoted in air quality management areas such as Seoul, Gyeonggi, and Incheon, based on the Special Act on Seoul Metropolitan Air Quality Improvement.

According to the OECD, in 2002 the level of fine-dust (PM10) pollution in Seoul was the worst of all large cities in the OECD countries. To host the 2002 World Cup event in a more pleasant environment, the South Korean government actively promoted policies and research on the spread of non-pollutant or low-pollutant vehicles. The Seoul Metropolitan Government proceeded with projects to replace diesel buses with CNG buses and to transform medium- and large-sized old diesel vehicles into low-pollutant ones. A project for installing an emission reduction device to diesel vehicles was also included in the project of turning old diesel vehicles into low-pollutant ones.

Meanwhile, Seoul’s PM10 and NO2 concentrations in 2003 were 69 ㎍/m3 and 38 ppb, respectively, i.e. 1.9~3.6 and 1.4~1.9 times higher than in major OECD cities, respectively. The social costs incurred by the capital area as a result of damages caused by such air pollution were estimated at KRW 10 trillion in 2000, and the number of deaths in Seoul caused by fine dust was estimated to have amounted to 1,940 in the same year. To reduce the high fine-dust concentration in the city’s air, the Seoul Metropolitan Government established the Seoul Metropolitan Air Quality Control Master Plan, which comprises various improvement measures including the introduction of the Total Industrial Site Volume Control System (TISVCS) by the end of 2003, the spread of low-pollutant vehicles, and the management of exhaust gas emissions from vehicles.

Some years before 1995, the number of registered vehicles in Seoul showed a rising trend of more than 10% per year due to rapid industrialization and rising incomes, although the growth rate slowed down from 1995 onward. The total number of vehicles in South Korea was a miniscule 40,000 in 1965, yet by 1997 the number had surpassed 10 million, representing an increase of more than 250 times in just 30 years. As of 2014, the total number of vehicles in the city stood at 20.12 million, and the air pollution problem caused by exhaust gases continues to become increasingly serious. In particular, 8.96 million vehicles, i.e. about 44.5% of all vehicles in South Korea, are concentrated in the capital area (Seoul, Gyeonggi, Incheon). Notably, 15% of these vehicles are concentrated in Seoul, which also has a very high population density. As such, the air pollution caused by vehicle pollutants has become an extremely important issue in large cities.

Table SEQ 표 \* ARABIC2. Growth in the number of vehicles in the entire country and in Seoul

By the end of 2014, diesel vehicles accounted for 33.1% of all vehicles in Seoul, showing a relatively higher figure than in other countries. The main reason for this is that diesel oil is cheaper than gasoline oil due to the country’s industrial and energy policy, and the fuel efficiency of diesel vehicles is slightly superior. In other countries, such as the United States, Japan, and Germany, diesel vehicles account for only 3%, 13%, and 18% of all vehicles, respectively. Due to the continuous improvements made to engines and emission control technologies, however, the supply of diesel vehicles has increased due to their significant economic benefits.

Table SEQ 표 \* ARABIC3.  Number of registered vehicles by type

In 2011, air pollution emissions from vehicles amounted to 135,637 tons, including 52% of total emissions, 81% of CO2 emissions, 45% of nitrogen oxide (NOx) emissions, and 49% of fine-dust emissions.

Figure 1.  Pollutant emissions from vehicles

The 1st Special Measures for Seoul Metropolitan Air Quality aimed to secure a good degree of visibility of the open sea at Incheon from Namsan Mountain in the center of Seoul on a clear day. To that end, a budget of about KRW 4 trillion originating from both the National Treasury and local funds was executed over a period of ten years (2005-2014). Ninety percent of the total budget was allotted to an old-diesel-vehicle exhaust gas reduction project, and an action plan was formulated and implemented with the aim of turning old diesel vehicles into low-pollutant ones. The improvement target was set at 40㎍/m3 PM10 (Tokyo) and 22ppb NO2 (Paris).

The 2nd Special Measures for Seoul Metropolitan Air Quality sought to realize a healthy century of cleaner air, under which efforts would be made to achieve this goal from 2015 to 2024. The improvement targets were set at 20㎍/m3 PM2.5, 30㎍/m3 PM10, 21ppb NO2, and 60ppb O2, and the focus was expanded to include gasoline and gas cars in addition to diesel vehicles.

In the case of specific diesel vehicles, cars whose emission warranty period has expired in accordance with Article 46 of the Clean Air Conservation Act, light cars and passenger cars whose emission warranty period has expired in accordance with No. 3, Annexed Table 5 of the Enforcement Regulations of Clean Air Conservation Act, and vehicles whose emission warranty period has expired in accordance with No. 5, Title 4, were excluded from the enforcement regulations of the Clean Air Conservation Act, as shown below.

Table SEQ 표 \* ARABIC4. Enforcement Regulations of the Clean Air Conservation Act

<Annex Table 18> of the Enforcement Regulations of the Clean Air Conservation Act regulates the exhaust gas application period according to the production period of diesel vehicles.

Table 5. Enforcement Regulations of the Clean Air Conservation Act <Annex Table 18>

The rapid increase in the number of automobiles in Seoul accounts for 52% of the air pollution, and automobiles are currently considered the main source of air pollution. Fine dust, excluding the inflow from outside, is generated mostly by diesel-powered vehicles. The more fuel an automobile consumes, the more air pollutants it releases into the air, which inevitably has an adverse effect on the air quality in Seoul. Air pollutants from the transport sector account for more than 70% of all air pollutant emissions; and among such air pollutants, those originating from automobiles are increasing gradually.

Air pollution has a highly negative effect on people’s health and causes damage to properties and ecosystems. Furthermore, the damages caused by the increase in air pollutant emissions also tend to accumulate. As this problem cannot be contained within an individual city but spreads to the surrounding areas, the seriousness of the problem is increasing accordingly. It is only natural for the number of automobiles to increase as people’s incomes and the transportation of goods increase, but Diesel Particulate Filters (DPFs) must be installed in diesel vehicles in order to significantly reduce the emission of air pollutants from such vehicles.

Air quality in Seoul has improved substantially considering that the concentration of PM10 decreased from 60 ㎍/㎥ in 2004 to 45 ㎍/㎥ in 2015. More recently, however, it has been increasing slightly due to the influx of air pollutants from neighboring countries in Northeast Asia, including China. The NO2 concentration has decreased slightly or shown no change since 2008. The implementation of Phase 1 of the Seoul Action Plan on Air and Environmental Improvement is considered to have lowered the pollution level near the city streets, and to have increased visibility.

The visibility (distance) data show a significant improvement owing to the better PM10 concentration in Seoul’s air. Visibility improved from 12.3 km in 2004 to 13.1 km in 2013 on average. The number of days with over 20 km of visibility have also increased significantly - from 76 days in 2007 to 202 days in 2010, 274 days in 2012, and 205 days in 2013.

Seoul, however, still needed to get the owners of diesel vehicles to follow the emissions reduction plan. Since January 2011, the authorities have implemented a series of administrative measures including the imposition of fines on diesel vehicle owners who failed to follow the plan within six months of notification, with the aim of inducing their participation in the effort.

1) Promotion of the pilot project

Seoul carried out the In-Use Diesel Vehicle Emission Reduction Pilot Project in 2004, installing 280 DPFs and 150 DOCs (diesel oxidation catalysts) in its official vehicles and public transit buses, and converting 450 vehicles into LPG (liquefied petroleum gas) vehicles, for a total of 880 units. The costs of DPF installation were fully shouldered by the government, while those for DOC installation and LPG conversion were shouldered evenly by the government and the city.

2) Full-scale implementation

After the pilot project period, the full-scale project began in earnest in 2005. With 50% of the project expense shouldered by the government and 50% by the city, the project has thus far covered a total of 12,130 diesel vehicles, including the installation of 7,789 DPFs and 1,490 DOCs, the conversion of 2,814 vehicles into LPG vehicles, and the early disposal of 37 vehicles. In addition, around 70-95% of the installation costs have been supported since 2006.

3) Mandatory installation

In 2008, the city made it mandatory to install low-emission devices in all diesel vehicles over seven years old and weighing over 3.5 tons. The policy included support for 70-95% of the installation costs, with 50% coming from the government and 50% from the city.

In 2009, the city extended the coverage of the In-Use Diesel Vehicle Emission Reduction Project to diesel vehicles over seven years old and weighing over 2.5 tons. It shouldered 70-95% of the installation costs, with 50% provided by the government and 50% by the city.

Table 6. Seoul Air Quality Improvement Targets

Figure 2. Status of vehicle travel restriction system installations

Table 7. Status of DPF devices and  subsidy (amount, effects)

Table 8. Type of diesel emission control devices

1) First-class emission control device (DPF: diesel particulate filter)

Figure 3.  How DPF works?

(Source: Korea Automobile Environmental Association, http://www.aea.or.kr/main_business/technology.php)

Figure 4. DPF regeneration method

(Source: Korea Automobile Environmental Association, http://www.aea.or.kr/main_business/technology.php)

Table  9. Heat supply system by generative method

Figure 5. p-DPF structure

 

Figure 6. How p-DPF  works?

 

3) Third-class emission control device (DOC: diesel oxidation catalyst)

Figure 7. How DOC device controls emission

Figure 8. DOC structure

Figure 9.  Reduction of pollutants by emission control devices (2007-2009) (Unit: ton)

Source: Analysis of the air quality improvement effects of pollution control measures (2011)

Table 10. Average exhaust gas reduction ratio through the implementation of the NO_x reduction pilot project

The project to install an emission control device to diesel vehicles, conducted with the aim of reducing fine-dust emissions, was evaluated as having been somewhat effective in reducing diesel vehicles’ fine-dust emissions. The level of carbon dioxide (CO2) pollution in Seoul, however, continued to exceed the environmental standards without showing a clear trend of improvement. Given that a significant portion of the NOX emissions in Seoul was still being discharged by diesel vehicles, it was judged necessary to execute a low-pollution diesel vehicle project that would take into account not only the reduction of fine dust but also of NOX.

In this regard, the Seoul Metropolitan Government proceeded with the project of installing PM-NOX simultaneous-reduction devices to 444 vehicles in 2013, including old construction machinery and large trucks, and has been expanding and promoting the project after the verification of its effects since 2015.