CHARACTERISTICS OF PARTICULATES AND GASEOUS-POLLUTANTS IN A HIGHWAY TUNNEL

Characteristics of air pollutants in a highway tunnel were studied in Osaka, Japan. The size distributions and concentrations of elemental c arbon (EC) and organic carbon (OC) were measured. The results demonstr ated that EC was the predominant constituent of particulates in the tu nnel, which accounted for 71% by mass of the particulate matter (PM) o f less than 2 mu m in aerodynamic diameter. EC concentration increased linearly with increase in diesel traffic volume and the coefficient o f correlation was found to be at a significant level (r = 0.93, p < 0. 001). In contrast, OC size distribution was bimodal with peaks in the size ranges of less than 1 and 2-10 mu m and not clearly dependent on diesel traffic volume. For the gaseous matter, nitrogen monoxide (NO) was found to de the major component of NOx (over 90%) and its concentr ation was proportional to the traffic volume of diesel vehicles (r = 0 .82, p < 0.001). The concentrations of carbon monoxide (CO) and carbon dioxide (CO2) in the tunnel were found, by multiregression analysis, to be dependent on both diesel and gasoline-powered vehicles. (C) 1998 Elsevier Science Ltd. All rights reserved.