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JOUR NAL O F E NVI R ONM E NT AL S C I E NC ES 87 (202 0) 1 – 9       3
































                                      Fig. 1 – Location of sampling site (https://map.baidu.com/).



           plasma-mass spectrometry (ICP-MS, Agilent 7700X, USA) was  crustal elements). The average concentrations of crustal
           used for analysis of elements. Strict quality control was  elements (Al, Fe, Ca, Mg, Na, Ti, Ba, and Sr) accounted for
           performed throughout the experimental process, and a  23.8% of PM 10 mass. Crustal elements are mainly from fugitive
           collision cell and shield torch were used to ensure the  dust influenced by the overall level of urban sanitation,
           accuracy of the measurement elements. Another part of filter  greening cover, human earthmoving activities, and dust
           was used for extraction with de-ionized water for an hour,  control. The crustal elements had strong correlations (almost
           then water-soluble inorganic ions were analyzed by ICS-90 ion  more than 0.8). Considering the maturity of research at home
           chromatography (Dean, USA). The carbon fractions were  and abroad, eight heavy metal elements such as Zn, Pb, Mn,
           measured by a thermo-optical carbon analyzer (DRI-2001A,  Cu, As, V, Cr and Cd were selected to be discussed. During the
           Atmoslytic, USA), following the IMPROVE protocol (Chow et  experimental period, the average concentrations of the eight
           al., 2007).                                         heavy metals were 415.413, 183.587, 105.227, 82.368, 16.098,
                                                                                      3
                                                               7.998, 49.795 and 4.529 ng/m . Zn and Pb were the most
           1.3. Meteorological condition and PM concentration  abundant heavy metals in PM 10 in Beijing.
           PM 2.5 and PM 10 hourly mass concentrations were collected by
           Quartz fiber on iron tower (next to the office building; 1 m above
           ground) at IAP campus. Meteorological hourly data at Beijing
           Olympic Sports Center (temperature (T), visibility (M) and
           relative humidity (RH), etc.) were from the Beijing Meteorolog-
           ical Bureau. The distance between two sites is 1.5 km.

           1.4. Air mass back trajectories

           Air mass backward trajectories were conducted by the Hybrid
           Single Particle Lagrangian Integrated Trajectory (HYSPLIT) 4.0
           Model to generate backward trajectories at three altitudes of
           100, 500 and 1000 m above ground level (AGL).



           2. Results and discussion

           2.1. Metals in atmospheric particles
                                                               Fig. 2 – Mass distribution of non-crustal elements in
           As shown in Fig. 2, Zn, Pb, Mo, Mn, and Cu are elements with  particles.
           high abundance among all tested elements (expected for
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