Differences Between Weekday and Weekend Levels of Ozone, NO2,NOx, and Respirable Suspended Particulates in Hong Kong

摘要

Differences in ozone (O3), nitrogen oxides (NOx), and respirable suspended particulate (RSP) weekday andnweekend concentrations in Hong Kong were investigated. Data were collected hourly by the Hong KongnEnvironmental Protection Department from January 1999 to October 2007 at 14 sites: 9 urban, 4 newly developed,nand 1 rural station. Weekend O3 concentrations were 14% and 22% higher for the afternoon peak O3 timenand 8-h O3 average concentrations, respectively, at six urban stations, whereas NO2 and NOx concentrationsnwere 19% and 25% lower, respectively, during the afternoon O3 peak time on weekends. No significant differencesnin peak afternoon O3 concentrations were found at the newly developed or rural stations. Weekend RSPnconcentrations were lower at most urban stations. Urban RSP concentrations were lower on weekends thannweekdays, by 14% for the morning rush hour and 8% for the daily average RSP. O3 formation sensitivity tonvolatile organic compounds and lower weekend NOx emissions could explain the O3 weekend effect in urbannHong Kong. Lower weekend RSP concentrations are predominantly the result of fewer anthropogenic emissions,nprimarily due to decreased traffic flow.