Characteristics and emission budget of carbonaceous species from post-harvest agricultural-waste burning in source region of the Indo-Gangetic Plain

Figures & data

Fig. 1 Map of study locations: Patiala, Hisar and Kanpur in the Indo-Gangetic Plain (shown as yellow shaded area), at Barapani near Shillong in NE-Himalaya and at Ahmedabad and Mt Abu in semi-arid western India. MODIS derived fire-counts (plotted on the right) during the paddy- and wheat-residue burning period in the source region; sampling site at Patiala (shown by open star) is located downwind of major field-fires.

Table 1. Concentrations of carbonaceous species and characteristic ratios (Av±sd given in parenthesis) from biomass burning emissions and fossil-fuel combustion in the Indo-Gangetic Plain (IGP)

Aerosol species	Paddy-residue burning(Oct–Nov; n=59)	Wheat-residue burning(April–May; n=31)	Difference^a(two-tailed t-test)	Fossil-fuel and bio-fuel emissions(Dec–March; n=51)
PM2.5 (µg m^−3)	60–391	18–123		19–244
	(195±87)	(50±23)		(124±58)
OC/PM2.5 (%)	21–50	19–36	S (t=4.9)	12–31
	(33±7)	(26±5)		(22±4)
EC/PM2.5 (%)	2–6	4–12	S (t=9.0)	2–9
	(3.5±1.1)	(6.9±2.5)		(4.6±1.8)
OC/EC^b	4–26	2.0–6.5	S (t=26)	1.9–10.1
	(10.6±1.6)	(3.0±0.4)		(4.2±0.8)
EC/TC^b	0.04–0.18	0.13–0.33	S (t=58)	0.09–0.35
	(0.04±0.00)	(0.19±0.02)		(0.15±0.01)
WSOC/OC^b	0.41–0.91	0.43–0.79	S (t=15)	0.45–0.86
	(0.52±0.02)	(0.60±0.03)		(0.62±0.03)
nss-K^+/OC^b	0.03–0.16	0.04–0.15	S (t=62)	0.01–0.13
	(0.06±0.01)	(0.14±0.01)		(0.06±0.01)
ΣPAHs (ng m^−3)	3.2–59.1	1.2–17.0		2.1–47.9
	(27.1±16.7)	(4.1±3.5)		(16.9±10.4)
ΣPAHs/OC (mg g^−1)^b	0.07–0.96	0.22–1.22	S (t=5.5)	0.12–0.82
	(0.37±0.04)	(0.30±0.08)		(0.65±0.07)
ΣPAHs/EC (mg g^−1)^b	0.80–10.19	0.69–2.35	S (t=22.3)	1.32–9.58
	(4.25±0.72)	(1.30±0.20)		(3.41±0.66)
PAHs isomer ratios
3-ring
ANTH/(ANTH+PHEN)	(0.19±0.08)	(0.11±0.04)	S (t=5.2)	(0.15±0.05)
4-ring
FLA/(FLA+PYR)	(0.46±0.02)	(0.50±0.03)	S (t=7.5)	(0.48±0.02)
BaA/(BaA+CHRY+TRIPH)	(0.25±0.05)	(0.24±0.09)	IS (t=0.6)	(0.28±0.04)
5-ring
BaP/(BaP+B[b,j,k]FLA)	(0.25±0.05)	(0.26±0.06)	IS (t=0.8)	(0.27±0.05)
6-ring
IcdP/(IcdP+BghiP)	(0.49±0.03)	(0.45±0.05)	S (t=4.7)	(0.50±0.05)

^aComparison between paddy- and wheat-residue burning emissions.

^bCorrelation analysis. S (significant difference for p<0.05) and IS (insignificant difference for p>0.05).

ΣPAHs (PM_2.5-bound) include: NAPH, naphthalene; ACY, acenaphthylene; 2-BrNAPH, 2-bromonaphthalene; ACE, acenaphthene; FLU, fluorene; PHEN, phenanthrene; ANTH, anthracene; FLA, fluoranthene; PYR, pyrene; BaA, benzo[a]anthracene; CHRY+TRIPH, chrysene/triphenylene; B[b,j,k]FLA, benzo[b+j+k]fluoranthene; BaP, benzo[a]pyrene; IcdP, indeno[1,2,3-cd]pyrene; D[ah,ac]ANTH, dibenzo[a,h+a,c]anthracene}; BghiP, benzo[g,h,i]perylene.

Fig. 2 Temporal variability in PM_2.5 and mass fractions of OC, EC and nss-K⁺ associated with different emissions from source region (Patiala, Fig. 1) in the Indo-Gangetic Plain. The nss-K⁺=K⁺ _aerosol – 0.037*Na⁺ _aerosol; where K⁺/Na⁺ mass ratio of 0.037 is used for sea-salt contribution of K⁺ (Keene et al., 1986).

Fig. 3 Scatter plots of (a) EC vs. OC; (b) OC vs. non-sea-salt: nss-K⁺; and (c) OC vs. WSOC during different emissions in the IGP.

Fig. 4 Cross plots of PAH isomers showing distinct differences for the biomass burning emission vis-à-vis fossil-fuel combustion in the IGP: (a) FLA/(FLA+PYR; 4-ring on X-axis) vs. ANTH/(ANTH+PHEN; 3-ring on Y-axis); and (b) FLA/(FLA+PYR; 4-ring on X-axis) vs. IcdP/(IcdP+BghiP; 6-ring on Y-axis). Other data source: wood-fuel burning (Bari et al., 2009); (Vehicular+Coal) combustion (Sharma et al., 2008); vehicular emission (Khillare et al., 2005a, b; Rajput and Lakhani, 2008); coal combustion (Kirton et al., 1991; Khalili et al., 1995; Li et al., 2010); savanna fire (Masclet et al., 1995).

Table 2. Spatial distribution of OC/EC ratio in ambient aerosols from the Indo-Gangetic Plain (IGP) and different locations during wintertime (December–March)

			OC	EC
Location	N	Concentration (µg m^-3)	(%)		OC/EC
IGP
Patiala	51	124±58 (PM2.5)	22±4	4.6±1.8	4.2±0.8	This study
Hisar	42	177±64 (TSP)	17	2.1	8.5±2.2	Rengarajan et al., 2007
Kanpur	17	141±73 (TSP)	18	3.4	6.2±3.7	Ram and Sarin, 2010
Allahabad	19	300±90 (TSP)	16	2.1	8.1±1.7
Western India
Ahmedabad	16	85±37 (PM2.5)	33±6	6±1	6.1±1.2	This study
Mt Abu	15	22±9 (PM2.5)	10±6	3.3±1.6	3.0±1	This study
Mumbai	4	128±27 (PM10)	20	10	2.0±0.3	Venkataraman et al., 2002
Southern India
Chennai	29	(PM10)^a			1.5±0.5	Pavuluri et al., 2011
Himalaya
NE-Himalaya	51	97±50 (PM2.5)	36±8	6±3	6.8±3.2	Rajput et al., 2013
NCO-P	28	(PM10)^a			11±2	Decesari et al., 2010
Manora peak	38	66±18 (TSP)	16	3	6.3±2.2	Ram et al., 2010
Ocean
Northern-BoB	31	38±20 (PM2.5)	16	5	3	Srinivas et al., 2011
Southern-BoB		22.3±9.9 (PM2.5)	12	5	2.2

^aPM₁₀ concentration is not reported (NR).

TSP refers to total suspended particulate matter.

Table 3. Emission budget of carbonaceous species from post-harvest agricultural-waste burning in the Indo-Gangetic Plain (IGP)

Open biomass Paddy-residue burning (October–November)	Emission factor^a (g/kg)	Fuel load^b (Kg/sq. km)	Area burnt^c (sq. km/y)	Emission budget^d
OC	7.6±1.2	11.8×10^5	48 400	436±68 Gg/y
EC	0.72±0.03			41±2 Gg/y
ΣPAHs	2.8±0.5^e			161±31 Mg/y
Wheat-residue burning (April–May)
OC	1.2±0.03	5.94×10^5	48 400	69±2 Gg/y
EC	0.31±0.02			18±1 Gg/y
ΣPAHs	0.4±0.1^e			21±6 Mg/y

^aEF modified, after (Kanokkanjana et al., 2011) for paddy-residue burning and, after (Hays et al., 2005) for wheat-residue burning.

^bAdopted from a study in the IGP (Badarinath et al., 2006).

^cInferred from MODIS (Aqua/Terra) satellite data (Resolution: 1°×1° lat.–long. grid).

^dEmission factor×fuel load×area.

^eEmission factor in mg/kg.

Fig. 5 Emission budgets of aerosol OC (primary) and EC from different biomass burning over the globe. Our data put together with a recent emission inventory suggest that OC and EC produced from agricultural-waste burning in the IGP (Northern India; shown as inset) contributes to ~22% [primary OC: 252±34 Gg/y] and 21% [EC: 59±2 Gg/y], respectively, on the global agricultural-waste burning emission scale.

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