title: Monitoring and source apportionment of trace elements in PM2.5: Implications for local air quality management.
abstract: Fine particulate matter (PM2.5) samples were collected simultaneously every hour in Beijing between April 2014 and April 2015 at five sites. Thirteen trace elements (TEs) in PM2.5were analyzed by online X-ray fluorescence (XRF). The annual average PM2.5concentrations ranged from 76.8 to 102.7 μg m-3. TEs accounted for 5.9%-8.7% of the total PM2.5mass with Cl, S, K, and Si as the most dominant elements. Spearman correlation coefficients of PM2.5or TE concentrations between the background site and other sites showed that PM2.5and some element loadings were affected by regional and local sources, whereas Cr, Si, and Ni were attributed to substantial local emissions. Temporal variations of TEs in PM2.5were significant and provided information on source profiles. The PM2.5concentrations were highest in autumn and lowest in summer. Mn and Cr showed similar variation. Fe, Ca, Si, and Ti tended to show higher concentrations in spring, whereas concentrations of S peaked in summer. Concentrations of Cl, K, Pb, Zn, Cu, and Ni peaked in winter. PM2.5and TE median concentrations were higher on Saturdays than on weekdays. The diurnal pattern of PM2.5and TE median concentrations yielded similar bimodal patterns. Five dominant sources of PM2.5mass were identified via positive matrix factorization (PMF). These sources included the regional and local secondary aerosols, traffic, coal burning, soil dust, and metal processing. Air quality management strategies, including regional environmental coordination and collaboration, reduction in secondary aerosol precursors, restrictive vehicle emission standards, promotion of public transport, and adoption of clean energy, should be strictly implemented. High time-resolution measurements of TEs provided detailed source profiles, which can greatly improve precision in interpreting source apportionment calculations; the PMF analysis of online XRF data is a powerful tool for local air quality management.
authors.affiliation: Division of Environmental Management & Policy, School of Environment, Tsinghua University, Beijing 100084, China; iSoftStone Information Technology (Group) Co., Ltd, Beijing 100193, China.
authors.forename: Yueyan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Environmental Management & Policy, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: changmiao@tsinghua.edu.cn.
authors.forename: Miao
authors.initials: M
authors.lastname: Chang
authors.affiliation: Division of Environmental Management & Policy, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Ding
authors.affiliation: Institute of Quantitative & Technical Economics, Chinese Academy of Social Sciences, Beijing 100732, China.
authors.forename: Shiwen
authors.initials: S
authors.lastname: Wang
authors.affiliation: iSoftStone Information Technology (Group) Co., Ltd, Beijing 100193, China.
authors.forename: Dun
authors.initials: D
authors.lastname: Ni
authors.affiliation: iSoftStone Information Technology (Group) Co., Ltd, Beijing 100193, China.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Hu
mesh_terms: D000393:Air Pollutants; D000068476:Beijing; D004784:Environmental Monitoring; D052638:Particulate Matter; D014131:Trace Elements
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D014131:Trace Elements
keywords: Air quality management; PMF; Source apportionment; Trace element; XRF