Stable carbon and nitrogen isotopic compositions of tropical atmospheric aerosols: sources and contribution from burning of C₃ and C₄ plants to organic aerosols

Figures & data

Fig. 1 Map showing the location of the sampling site of Morogoro, Tanzania.

Fig. 2 Typical examples of 5-day backward air mass trajectories arriving at Morogoro during the May–August 2011 sampling period.

Fig. 3 Trends of aerosol mass concentrations (µg m⁻³) in PM_2.5 and PM₁₀ during the May–August 2011 sampling period at Morogoro.

Table 1. Concentrations of TC and TN (µg m⁻³), their isotope ratios (‰), TC/TN and TC/PM (%) in PM_2.5 from Morogoro, Tanzania (n=21)

Date	δ^13C	δ^15N	TC	TN	TC/TN	TC/PM	TN/PM
30/5/2011	−25.4	NA	6.1	BDL	NA	22.4	NA
31/5/2011	−25.8	16.1	7.2	0.5	13.9	21.8	1.6
1/6/2011	−25.1	13.5	3.7	0.6	6.3	12.9	2.0
2/6/2011	−25.9	NA	6.0	BDL	NA	26.4	NA
4/6/2011	−24.8	13.4	3.9	0.4	10.4	11.6	1.1
5/6/2011	−24.3	15.3	4.5	0.4	11.5	17.8	1.6
6/6/2011	−25.6	NA	7.4	BDL	NA	20.3	NA
7/6/2011	−25.6	14.1	5.3	0.4	12.8	22.1	1.7
9/6/2011	−26.1	NA	3.1	BDL	NA	19.0	NA
12/6/2011	NA	NA	4.5	BDL	NA	17.5	NA
13/6/2011	NA	NA	7.9	0.6	13.7	20.6	1.5
28/7/2011	−22.6	20.3	8.0	0.9	9.2	21.9	2.4
29/7/2011	−22.0	13.5	10.4	1.4	7.6	34.7	4.6
1/8/2011	−21.8	22.1	9.7	0.9	11.4	30.0	2.6
2/8/2011	−20.6	17.2	9.7	1.5	6.3	23.7	3.8
3/8/2011	−21.2	17.9	8.3	0.6	12.8	27.3	2.1
4/8/2011	NA	NA	6.6	0.7	10.2	10.8	1.1
5/8/2011	−22.4	14.2	6.9	0.7	9.6	14.5	1.5
6/8/2011	−21.3	NA	4.2	BDL	NA	9.6	NA
7/8/2011	−21.7	16.4	5.5	0.7	8.1	17.5	2.2
8/8/2011	−21.8	16.8	7.7	0.6	13.5	20.8	1.5
Mean±SD	−23.6±1.9	16.2±2.7	6.5±2.1	0.7±0.3	10.5±2.6	20.8±6.4	2.2±1.0

BDL: below detection limit, DL: ca. 0.02 µg m⁻³ for TC and 0.05 µg m⁻³ for TN. NA: not available.

Table 2. Concentrations of TC and TN (µg m⁻³), their isotope ratios (‰), TC/TN and TC/PM (%) in PM₁₀ from Morogoro, Tanzania (n=21)

Date	δ^13C	δ^15N	TC	TN	TC/TN	TC/PM	TN/PM
30/5/2011	−24.0	10.4	6.0	0.7	9.2	13.3	1.4
31/5/2011	−24.1	11.6	8.2	0.7	11.0	ND	NA
1/6/2011	−24.4	NA	6.8	BDL	NA	11.8	NA
2/6/2011	−24.4	NA	8.3	BDL	NA	16.1	NA
4/6/2011	−23.4	13.0	4.2	0.6	6.9	11.8	1.7
5/6/2011	−23.0	12.9	6.4	0.7	9.3	17.7	1.9
6/6/2011	−23.7	12.7	9.7	0.8	12.0	20.1	1.7
7/6/2011	−23.9	13.4	7.5	0.7	10.3	18.2	1.8
9/6/2011	−23.8	10.7	6.4	0.7	8.7	15.2	1.8
12/6/2011	−23.8	11.2	9.3	0.8	11.6	16.8	1.4
13/6/2011	−23.4	15.4	11.4	1.0	11.9	19.9	1.7
28/7/2011	−23.9	13.4	5.9	0.6	10.2	12.0	1.2
29/7/2011	−23.5	16.5	10.5	0.9	11.1	28.7	2.6
1/8/2011	−22.7	17.0	16.0	1.2	13.2	20.3	1.5
2/8/2011	−22.6	18.7	18.0	1.6	11.4	18.1	1.6
3/8/2011	−22.4	14.6	12.6	0.9	14.1	21.3	1.5
4/8/2011	−23.9	NA	11.7	BDL	NA	14.6	NA
5/8/2011	−23.8	12.9	8.8	0.8	11.2	15.5	1.4
6/8/2011	−23.7	13.9	5.3	0.5	11.5	12.2	1.1
7/8/2011	NA	NA	9.8	0.8	12.1	17.8	1.5
8/8/2011	−23.4	14.7	11.2	0.8	14.1	20.1	1.4
Mean±SD	−23.6±0.5	13.7±2.2	9.2±3.5	0.8±0.2	11.1±1.8	17.0±4.2	1.6±0.3

BDL: below detection limit, DL: ca. 0.02 µg m⁻³ for TC and 0.05 µg m⁻³ for TN. NA: not available.

Table 3. Isotope ratios (‰) of carbon and nitrogen in the fine and coarse fractions of Morogoro, Tanzania, during 2011 wet and dry season campaigns

	Wet season		Dry season		Wet season		Dry season
	δ^13Cfine	δ^13Ccoarse	δ^13Cfine	δ^13Ccoarse	δ^15Nfine	δ^15Ncoarse	δ^15Nfine	δ^15Ncoarse
Min.	−26.1	−23.8	−22.6	−30.8	13.4	7.1	13.5	5.8
Max.	−24.3	−17.8	−20.6	−23.4	16.1	12.5	22.1	19.7
Mean±SD	−25.4±0.6	−21.5±2.1	−21.7±0.7	−26.5±3.0	14.7±1.2	9.1±2.9	17.4±3.1	12.1±5.1

Fig. 4 Temporal variation of TC and δ¹³C in (a) PM_2.5 and (b) PM₁₀ during the May–August 2011 sampling period at Morogoro.

Fig. 5 Relation between TC with levoglucosan and nss-K⁺ in PM_2.5 (a, b) and PM₁₀ (c, d) during the sampling period.

Fig. 6 Temporal variation of TN and δ¹⁵N in (a) PM_2.5 and (b) PM₁₀ during the May–August 2011 sampling period at Morogoro.

Fig. 7 Relation between -N, -N and (+)-N with TN in (a) PM_2.5 and (b) PM₁₀ during the sampling period.

Fig. 8 Linear relation between δ¹³C of TC with nss-K⁺ and levoglucosan in (a, b) PM_2.5 and (c, d) PM₁₀ during the sampling period in tropical aerosols from Tanzania.

Fig. 9 Biomass burning active fire spots detected by MODIS satellite images (from NASA website) over southern and eastern Africa and Madagascar in July 2011.