Composition characteristics of PM_2.5 metals and metalloids in a sampling point of Shanghai in winter from 2014 to 2017

Objective To explore the composition and distribution of metal and metalloids in fine particulate metter in a certain area of Shanghai through four consecutive years of dynamic monitoring.

Methods The sampling point was on the roof of a community health service center in Shanghai, with a height of 12.5 meters.In the four winters of 2014-2017 from Dec. to Feb. next year, samples were continuously collected for 7 days(from 10^th to 16^th) a month and 22 hours for each day.Inductively coupled plasma-mass spectrometry (ICP-MS) was used for the determination of metals and metalloids in collected samples.

Results The pairwise comparisons between the total metals, Al, Be, Cr, Hg, Pb, Mn, Ni, Se and Tl in any two years were statistically different through the rank sum test.In the Cochran-Armitage trend test, Al showed an upward trend in the whole periods, while Cr, Pb and Ni was on a downward trend.In factor analysis, factor 1 in each year had relatively stable component elements (As, Cd, Pb, Mn, Se), while the internal components of the remaining factors were relatively unstable.

Conclusions There may be relatively stable sources of pollution locally.Al, Cr, Pb and Ni have a significant tendency to increase or decrease.