SUPPLEMENTARY INFORMATION

for

Mineral dust and NOx promote the conversion of SO2 to sulfate in heavy pollution days

Hong He*1, Yuesi Wang*2, Qingxin Ma1, Jinzhu Ma1, Biwu Chu1,3, Dongsheng Ji2, Guiqian Tang2, Chang Liu4, Hongxing Zhang1, Jiming Hao3

(1Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

2State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

3State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 10084, China

4Chinese Academy of Meteorological Sciences, Beijing 100081, China)

1. Locations of monitoring stations

FigureS1 and Table S1 provide the locationsand characteristics of the air quality monitoring stations.All air quality monitoring stations were selected and set up according to the US EPA methoddesignations1.

Table S1 Location and characteristics of monitoring stations selected for the study

site / Site
characteristics / Latitude / Longitude / Altitude
(m.a.s.l.)
Beijing / Urban / 116º22′21″E / 39º58′28″N / 44
Mangshan / Suburb / 116º16′10″E / 40º16′3″N / 587
Xinglong / Outer suburb / 117º34′34″E / 40º23′40″N / 879

Fig. S1 Map of northern China and locations of the monitoring sites (generated with ArcGIS V10.1)

Fig.S2 Comparison of the integral infrared peak area of sulfate when NO2+SO2was exposed to the surface of Al2O3, ZnO and TiO2 with pure N2 (black solid squares) and synthetic air (80% N2 + 20% O2) (red hollow squares) as carrier gas. Reaction conditions: Total flow = 100 mL/min. Concentrations of SO2 and NO2 both 200 ppm. T=303 K.

Fig. S3 In situ DRIFTS spectra of 500 ppbv SO2 and NO2 reaction in a flow of 100 mL·min-1 synthetic air (20% O2, 80% N2) on the surface of CaO as a function of time at 303 K.

Fig. S4Particle number size distributions and fractional contributions of organics, nitrate, sulfate, ammonium and chloride to the PM1 mass during thehaze episode from 6:00LT to 15:00LT, 12 January2.

Table S2 Chemical compositions of PM2.5 in Beijing during non-haze and haze episodes in Jan. 9th-14th, 2013 (unit: μg/m3)

Org / EC / sulfate / nitrate / ammonia / Sea salts / mineral / others
2013-1-9 12:00 / 46.3 / 7.6 / 11.9 / 13.0 / 9.3 / 6.5 / 9.8 / 6.9
2013-1-10 0:00 / 84.4 / 15.2 / 24.9 / 21.1 / 19.4 / 9.0 / 26.7 / 1.1
2013-1-10 12:00 / 117.6 / 19.7 / 56.8 / 42.0 / 37.0 / 14.3 / 20.9 / 24.0
2013-1-11 0:00 / 186.5 / 30.9 / 82.6 / 50.8 / 54.4 / 24.0 / 38.7 / 22.1
2013-1-11 12:00 / 120.8 / 15.2 / 60.2 / 46.8 / 39.7 / 12.9 / 18.6 / 30.3
2013-1-12 0:00 / 147.7 / 18.9 / 62.8 / 42.1 / 38.9 / 17.6 / 32.9 / 9.7
2013-1-12 12:00 / 261.6 / 27.9 / 155.4 / 89.3 / 71.5 / 33.0 / 101.5 / 10.9
2013-1-13 0:00 / 175.3 / 20.2 / 152.5 / 68.1 / 65.7 / 43.2 / 84.5 / 4.0
2013-1-13 12:00 / 111.1 / 13.6 / 81.7 / 52.9 / 45.9 / 23.6 / 54.6 / 12.3
2013-1-14 0:00 / 144.4 / 18.3 / 78.9 / 48.6 / 44.6 / 21.1 / 56.1 / 3.3
2013-1-14 12:00 / 98.0 / 11.0 / 63.5 / 44.2 / 39.0 / 15.6 / 29.5 / 21.9

Table S3. Experimental conditions in smog chamber experiments

Experiment / α-pinene
/ppm / NO
/ppb / NO2
/ppb / Al2O3 seed aerosol / SO2
/ppb / RH
/% / T
/K
number concentration
/ (# m-3) / volume concentration
/ (μm3 cm-3)
N50 (dry) / 0.21 / 48 / 48 / 0 / 0 / 145 / 12 / 303
N150 (dry) / 0.20 / 50 / 155 / 0 / 0 / 142 / 12 / 303
N50 / 0.20 / 49 / 46 / 0 / 0 / 136 / 50 / 303
Al-N50 / 0.20 / 52 / 47 / 7100 / 45.5 / 137 / 50 / 303
Al-N150 / 0.20 / 52 / 156 / 7800 / 54.4 / 139 / 50 / 303

Reference:

1. US EPA, 2007. ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 53 and 58 [EPA-HQ–OAR-2004-0018; FRL- ] RIN 2060-AJ25 /ttn/amtic/files/ambient/pm25/ 092706sign.pdf

2.Wang, Y. et al. Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China. Sci. China Earth. Sci.57, 14-25 (2014).

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