Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 523, Issue -, Pages 152-160Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2015.03.119
Keywords
Vertical variability; Diurnal distribute; Clear day; Heavy pollution day; Chemical mass balance; Pollution sources
Categories
Funding
- Tianjin Science and Technology projects [14JCYBJC22200]
- Science and Technology Support Program [13ZCZDSF02100]
- National Natural Science Foundation of China (NSFC) [41205089, 21207069, 21407081]
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In this study, PM2.5 samples were collected at four heights (10 m, 40 m, 120 m and 220 m) at a meteorological tower in the daytime and nighttime during the heating season in Tianjin, China. The vertical variation and diurnal variability of the concentrations of PM2.5 and main chemical compositions were analyzed in clear days and heavy pollution days. Generally, mass concentrations of PM2.5 and the chemical compositions showed a decreasing trend with increasing height, while mass percentages of SO42-, NO3- and OC showed an increasing trend with increasing height. Concentrations of ion species and carbon compound in PM2.5 samples in the daytime were higher than those collected at night, which was due to intense human activities and suitable meteorological condition in the daytime. The ratios of NO3-/SO42- and OC/EC were also considered, and we have observed that their levels on heavy pollution days were higher than those on clear days. In addition, source apportionments were identified quantitatively using the CMB-iteration model. The results indicated that contributions of secondary ion species increased with increasing height, while contributions of other pollutant sources decreased, and contributions of vehicle exhaust were relatively high on clear days. (C) 2015 Elsevier B.V. All rights reserved.
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