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Atmosphere 2018, 9(10), 390; https://doi.org/10.3390/atmos9100390

An Integrated Method for Factor Number Selection of PMF Model: Case Study on Source Apportionment of Ambient Volatile Organic Compounds in Wuhan

1
National Climate Center, China Meteorological Administration, Beijing 100081, China
2
Department of Civil and Environmental Engineering, Politecnico di Milano, Milan 20133, Italy
3
National Institute for Environmental Studies, Ibaraki 305-8506, Japan
4
INET, Tsinghua University, Beijing 100084, China
5
Wuhan Municipality Environmental Monitoring Center, Wuhan 430015, China
6
Shanghai BAIF Technology Co., LTD, Shanghai 201202, China
*
Authors to whom correspondence should be addressed.
Received: 16 August 2018 / Revised: 1 October 2018 / Accepted: 2 October 2018 / Published: 8 October 2018
(This article belongs to the Section Air Quality)
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Abstract

The positive matrix factorization (PMF) model is widely used for source apportionment of volatile organic compounds (VOCs). The question about how to select the proper number of factors, however, is rarely studied. In this study, an integrated method to determine the most appropriate number of sources was developed and its application was demonstrated by case study in Wuhan. The concentrations of 103 ambient volatile organic compounds (VOCs) were measured intensively using online gas chromatography/mass spectrometry (GC/MS) during spring 2014 in an urban residential area of Wuhan, China. During the measurement period, the average temperature was approximately 25 °C with very little domestic heating and cooling. The concentrations of the most abundant VOCs (ethane, ethylene, propane, acetylene, n-butane, benzene, and toluene) in Wuhan were comparable to other studies in urban areas in China and other countries. The newly developed integrated method to determine the most appropriate number of sources is in combination of a fixed minimum threshold value for the correlation coefficient, the average weighted correlation coefficient of each species, and the normalized minimum error. Seven sources were identified by using the integrated method, and they were vehicular emissions (45.4%), industrial emissions (22.5%), combustion of coal (14.7%), liquefied petroleum gas (LPG) (9.7%), industrial solvents (4.4%), and pesticides (3.3%) and refrigerants. The orientations of emission sources have been characterized taking into account the frequency of wind directions and contributions of sources in each wind direction for the measurement period. It has been concluded that the vehicle exhaust contribution is greater than 40% distributed in all directions, whereas industrial emissions are mainly attributed to the west southwest and south southwest. View Full-Text
Keywords: PMF; factor number selection; volatile organic compounds; source apportionment; central China PMF; factor number selection; volatile organic compounds; source apportionment; central China
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Wang, F.; Zhang, Z.; Acciai, C.; Zhong, Z.; Huang, Z.; Lonati, G. An Integrated Method for Factor Number Selection of PMF Model: Case Study on Source Apportionment of Ambient Volatile Organic Compounds in Wuhan. Atmosphere 2018, 9, 390.

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