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

Characteristics and emission budget of carbonaceous species from two distinct post-harvest agricultural-waste (paddy- and wheat-residue) burning emissions have been studied from a source region (Patiala: 30.2°N, 76.3°E; 250 m amsl) in the Indo-Gangetic Plain (IGP), Northern India. The PM_2.5 mass concentration varies from 60 to 390 µg m⁻³ during paddy-residue burning (October–November) with dominant contribution from organic carbon (OC≈33%), whereas contribution from elemental carbon (EC) centres at ~4%. Water-soluble organic carbon (WSOC) accounts for about 50% of OC. In contrast, mass concentration of PM_2.5 during the period of wheat-residue burning (April–May) is significantly lower, varies from 18 to 123 µg m⁻³ and mass fractions of EC and OC are 7 and 26%, respectively. The diagnostic ratios of OC/EC (11±2), WSOC/OC (0.52±0.02), nss-K⁺/OC (0.06±0.00) and ΣPAHs/EC (4.3±0.7 mg/g) from paddy-residue burning emissions are significantly different than those from wheat-residue burning (OC/EC: 3.0±0.4; WSOC/OC: 0.60±0.03; nss-K⁺/OC: 0.14±0.01 and ΣPAHs/EC: 1.3±0.2 mg/g). The emission budget of OC, EC and ΣPAHs from post-harvest agricultural-waste burning in the IGP are estimated to be 505±68 Gg/y, 59±2 Gg/y and 182±32 Mg/y, respectively. From a global perspective, crop-residue burning in Northern India contributes nearly 20% of both OC and EC to the total emission budget from the agricultural-waste burning.