8 7 7 6 6 5 5 4 4 3 3 2 Ethane ppbv Acetylene ppbvAcetylene 2 1 2 R2=0.417 R =0.3304 1 0 0.51.01.52.02.53.03.5 0.5 1.0 1.5 2.0 2.5 3.0 3.5 SO (μg/m3) SO (μg/m3) 2 2

Figure S1. Relationship between ethane or acetylene and SO2 for sampling period.

(a) Percentage % 0 20406080100 1,2,3-Trimethylbenzene 1,2,4-Trimethylbenzene o-Ethyltoluene 1,3,5-Trimethylbenzene p-Ethyltoluene m-Ethyltoluene n-Propylbenzene Isopropylbenzene o-Xylene Styrene m/p-Xylene Ethylbenzene Toluene Benzene 1-Hexene 4-Methyl-1-pentene 2-Methyl-2-butene cis-2-Pentene trans-2-Pentene 2-Methyl-1-butene 1-Pentene 3-Methyl-1-butene cis-2-Butene trans-2-Butene 1,3-Butadiene 1-Butene Propene Ethylene Acetylene n-Decane n-Nonane n-Octane 3-Methylheptane 2-Methylheptane 2,3,4-Trimethylpentane n-Heptane 2,2,4-Trimethylpentane 3-Methylhexane 2,3-Dimethylpentane 2-Methylhexane 2,4-Dimethylpentane Methylcyclopentane n-Hexane 3-Methylpentane 2-Methylpentane 2,3-Dimethylbutane 2,2-Dimethylbutane n-Pentane i-Pentane n-Butane i-Butane Propane Ethane

Oil volatilization Industrial processes Coal combustion Vehicle exhaust Industrial solvent

(b) Percentage % 0 20406080100 1,2,3-Trimethylbenzene 1,2,4-Trimethylbenzene o-Ethyltoluene 1,3,5-Trimethylbenzene p-Ethyltoluene m-Ethyltoluene n-Propylbenzene Isopropylbenzene o-Xylene Styrene m/p-Xylene Ethylbenzene Toluene Benzene 1-Hexene 4-Methyl-1-pentene 2-Methyl-2-butene cis-2-Pentene trans-2-Pentene 2-Methyl-1-butene 1-Pentene 3-Methyl-1-butene cis-2-Butene trans-2-Butene 1,3-Butadiene 1-Butene Propene Ethylene Acetylene n-Decane n-Nonane n-Octane 3-Methylheptane 2-Methylheptane 2,3,4-Trimethylpentane n-Heptane 2,2,4-Trimethylpentane 3-Methylhexane 2,3-Dimethylpentane 2-Methylhexane 2,4-Dimethylpentane Methylcyclopentane n-Hexane 3-Methylpentane 2-Methylpentane 2,3-Dimethylbutane 2,2-Dimethylbutane n-Pentane i-Pentane n-Butane i-Butane Propane Ethane

Industrial solvent Coal combustion Vehicle exhaust Oil volatilization Industrial processes

(c) Percentage % 0 20406080100 1,2,3-Trimethylbenzene 1,2,4-Trimethylbenzene o-Ethyltoluene 1,3,5-Trimethylbenzene p-Ethyltoluene m-Ethyltoluene n-Propylbenzene Isopropylbenzene o-Xylene Styrene m/p-Xylene Ethylbenzene Toluene Benzene 1-Hexene 4-Methyl-1-pentene 2-Methyl-2-butene cis-2-Pentene trans-2-Pentene 2-Methyl-1-butene 1-Pentene 3-Methyl-1-butene cis-2-Butene trans-2-Butene 1,3-Butadiene 1-Butene Propene Ethylene Acetylene n-Decane n-Nonane n-Octane 3-Methylheptane 2-Methylheptane 2,3,4-Trimethylpentane n-Heptane 2,2,4-Trimethylpentane 3-Methylhexane 2,3-Dimethylpentane 2-Methylhexane 2,4-Dimethylpentane Methylcyclopentane n-Hexane 3-Methylpentane 2-Methylpentane 2,3-Dimethylbutane 2,2-Dimethylbutane n-Pentane i-Pentane n-Butane i-Butane Propane Ethane

Industrial processes Oil volatilization Coal combustion Industrial solvent Vehicle exhaust Figure S2. apportionment of VOCs in the non-heating (a), heating (b) and sandstorm (c) sampling periods.