Temporal variations of elemental carbon in Tokyo

摘要: [1] Mass concentrations of elemental carbon (EC) in fine mode and mixing ratios monoxide (CO) were measured at the University Tokyo campus different seasons 2003–2005. Measurements EC made using a semicontinuous thermal-optical analyzer. The mass nonvolatile aerosol by calibrated scanning mobility particle sizer combined with heated inlet agreed independent measurements systematic difference about 4%, demonstrating that well represent those for EC. A majority therefore concentration was volume equivalent diameters between 50 200 nm, peaking around 130 nm. correlation CO generally compact throughout measurement period because similarity sources. slope EC-CO (ΔEC/ΔCO) is useful parameter validating emission inventories. ΔEC/ΔCO showed distinct diurnal variation. On weekdays, reached maximum values 3 μg m−3 9 ng m−3/parts per billion volume, respectively, early morning (0400–0800 local time), when traffic density heavy-duty trucks diesel engines highest. In addition, these lower factor 2 on Sundays. heavy truck similar weekday/weekend variations, indicating exhaust from an important source Monthly mean seasonal variation, reaching broad spring-autumn minimum midwinter, following variation temperature, as observed Maryland, United States (Chen et al., 2001). This temperature dependence likely due to emissions intake air temperature. More stringent regulation particles cars started Metropolitan Area October 2003. did not change, however, exceeding natural variability (10%) after 1 year start new regulations, taken into account. indicates effective reducing year.