The study on vertical variability of PM10 and the possible sources on a 220 m tower, in Tianjin, China

In this study, PM10 samples were collected at a meteorological tower in Tianjin, China. Four height levels (10 m, 40 m, 120 m and 220 m) were selected as the sampling sites. During the measurement campaign, the highest PM10 and species concentrations were obtained at 10 m, while lower concentrations were obtained at higher sampling sites. According to the vertical variability analysis of species concentrations and fractions (%), significant differences between different heights were found for certain species, such as Al, Si, Ca, OC and EC, while such differences for NO3- and SO42- were insignificant. In addition, the source contributions at each sampling site were calculated by a chemical mass balance (CMB) model. In all sampling sites, secondary sulfate accounted for the largest contributions (24.11-30.96%). The other estimated contributions were secondary nitrate (16.19-20.95%), crustal dust (10.74-11.37%), coal combustion (12.47-14.39%), vehicle exhaust (13.92-14.78%) and cement dust (4.60-9.89%). Finally, the conditional probability function (CPF) plots and potential source contribution function (PSCF) maps show that the ambient samples might be from local potential sources at lower sampling heights as well as regional potential sources at higher sampling heights during this measurement campaign. (C) 2011 Elsevier Ltd. All rights reserved.