Effect of traffic loading on particle-bound water-soluble ions and carbons collected near a busy road and at an urban site

Abstract

This study examines size-resolved particle-bound water-soluble ions and carbons (element carbon (EC) and organic carbon (OC)) collected near a busy road and at an urban site. The traffic-related fine and coarse particles were collected using two manual dichotomous samplers (Dichots) equipped with Quartz filters. The PM2.5/PM2.5−10 value during rush hour (3.57) exceeded that during slack time (2.72). During weekdays and weekends, although the roadside PM2.5 concentration correlated well with traffic flow (R2= 0.91 and 0.81, respectively), the roadside PM2.5−10 concentration did not. The lowest second aerosol concentrations were observed from 19:00 to 21:00 during weekdays and weekends. The average content of total water-soluble ions in PM2.5 was 30.7% and 35.7% for weekday and weekend samples, respectively (a total average of 33.2%). In PM2.5, the content of NO− 3 (8.95-11.0%) exceeded that of SO2− 4 (7.08–8.10%) at the roadside site. Conversely, the content of PM2.5-bound SO2− 4 was higher than that of PM2.5-bound NO− 3 at the urban site. The mean content of PM2.5-bound TC was 35.8%, while that of PM2.5−10-bound TC was 15.9%. Moreover, the R2 values of traffic flow versus PM2.5-bound EC concentration on weekdays and weekends were 0.89 and 0.56, respectively, and were 0.82 and 0.38, respectively, for those of traffic flow versus PM2.5-bound OC concentration.