Emission and dispersion of PAHs from heavy traffic road N. Ozaki, K. Nitta, T. Sugihara, T. Fukushima & T. Komatsu

Background (1) Air pollution in urban area has been a special concern for many years. Group of polycyclic aromatic hydrocarbons (PAHs) are becoming the major concern because of their higher emission and toxicity. PAHs are generated mainly from combustion processes such as vehicle emmisions, industrial processes, heating processes, etc.

Background (2) Many researchers have been investigating the behavior of PAHs. Emission and dispersion from heavy traffic road is one of the important processes especially in atmospheric environment.

Objectives The atmospheric concentration and deposition of particulate matter and PAHs were measured in the vicinity of a heavy traffic road. The spacial and temporal variations in the atmospheric dispersion and ground surface loading due to the traffic sources were discussed. The analysis of origin was conducted.

What’s PAHs? PAHs: Polycyclic aromatic hydrocarbons Benzo(a)pyrene Fluoranthene Indeno(1,2,3-cd)pyrene PAHs are generated mainly through incomplete combustion processes of petroleum. Several of them has carcinogenicity. Anthracene

Roadside sampling Station In a suburban area Traffic density: 20,000~30,000 vehicles d-1

Sampling schedule Sampling was conducted every 24 hours. Sampling periods：2001/Nov./19~26 (Winter) 　　　　　　 2002/Aug./14~21 (Summer) In the sampling terms, the climate was mild and moderate, and no major precipitation occurred during the sampling and precedent several days of sampling.

Sampling items Dry deposited particulate matter Particulate matters 　Fine Particulate matter (7~0.6μm) 　Coarse Particulate matter (over 7μm) Dry deposited particulate matter 16 PAHs contents adsorbed on particulate matters Air temperature, Precipitation, Wind velocity and direction, and Traffic density なお、PAHsはすべて粒子付着態のみを対象としており、気相は対象としていない

解析に際しての3つの特性量 粉塵濃度 PAHs濃度 PAHs含量 粉塵の、大気単位体積当たりの重量 (降下粉塵の場合はフラックス)

(Winter sampling, 1m from the roadside)

Road Winter Fine Coarse Deposited 1m 16m LDV HDV

Winter Summer Fine Coarse Deposited LDV HDV LDV Traffic HDV

Patterns of PAHs contents (mg/gdw) Winter Summer

Source apportionment analysis •CMB(Chemical Mass balance) method •The less than four rings PAHs were excluded.

冬 夏 Source apportionment (for PAHs) Traffic HDV LDV Weekday Holiday 小径 大径 夏 Weekday Holiday Source apportionment (for PAHs) LDV HDV Traffic 降下

Winter Summer Fine Source apportionment (for PM) Coarse Dry deposited

Source apportionment for each PAH (fine PM) (μg•g-1) Workday Holiday (μg•g-1) Observed value

Conclusions The dispersion and deposition profile of PAHs were clarified from measurements and analysis of atmospheric concentration from a heavy traffic road. The contribution of each source of particulate matter was quantified using the CMB receptor model. Diesel and gasoline emissions were the main source of atmospheric particulate matter, and debris from tires was the main source of deposited particulate matter.

Future Perspectives Secondary generation process should be considered for applying the CMB method. Coagulation of particulate matters Photolysis