Comparison of methods of functional group analysis using results from laboratory and field aerosol measurements

Figures & data

Table 1. Experiments and conditions used to form SOA for analysis of functional group composition using the Deriv-Spec and FTIR methods.

Exp.	VOC	Oxidant/Precursor	Seed	RH (%)	Lights^a	Mixing Ratio (ppm)^b
						VOC	Oxidant/Precursor
1	α-pinene	O3	–	0	–	1	2
2	α-pinene	H2O2	(NH4)2SO4	50	90 min/100%	2	11
3	isoprene	CH3ONO/NO	–	0	40 min/100%	5	10/10
4	α-pinene	CH3ONO/NO	(NH4)2SO4	50	12 min/50%	1	10/10
5	pentadecane	CH3ONO/NO	–	0	60 min/50%	1	10/10
6	limonene	N2O5	(NH4)2SO4	50	–	1	0.33
7	β-pinene	N2O5	(NH4)2SO4	50	–	1	0.33
8	α-pinene	N2O5	(NH4)2SO4	50	–	1	0.33
9	β-pinene	N2O5	(NH4)2SO4/H2SO4	50	–	1	0.33

^a Light intensities of 50% and 100% correspond to J_NO2 values of about 0.37 and 0.61 min⁻¹.

^b A mixing ratio of 1 ppm = 2.03 × 10¹³ molecules cm⁻³ at ambient pressure in Boulder, CO.

Figure 1. Functional group composition of SOA formed in environmental chamber experiments designed to mimic daytime reaction conditions observed during the SOAS field campaign and analyzed using the Deriv-Spec (CU) and FTIR (SIO) methods. These correspond to experiments 1–4 in Table 1.

Figure 2. Functional group composition of SOA formed in environmental chamber experiments designed to mimic nighttime reaction conditions observed during the SOAS field campaign and analyzed using the Deriv-Spec (CU) and FTIR (SIO) methods. These correspond to experiments 6–9 in Table 1. Note that reactions with O₃ (experiment 1, Figure 1) can also occur at night.

Figure 3. Functional group composition of SOAS samples collected at (a,b) Look Rock, TN and (c,d) Centerville, AL measured using the Deriv-Spec (CU) and FTIR (SIO) methods. (a) and (b) were combined daytime + nighttime samples collected under low NO_x conditions and high NO_x conditions, respectively, (c) was a nighttime sample collected under low NO_x conditions and (d) was a daytime sample collected under high NO_x conditions.