NOx emissions from biomass burning of shifting cultivation areas from tropical deciduous forests of India - estimates from ground-based measurements

Biomass burning in the tropics is an important source of trace gases. Shift ing cultivation in India is one of the major sources of biomass burning act ivities, during which due to combustion, several trace gases are emitted in to the atmosphere. NOx emissions are relatively important as they affect th e tropospheric photochemistry. In the present study, an attempt has been ma de to quantify the NOx emissions from shifting cultivation areas of tropica l dry deciduous forests of India, at two sites. Fuel load, fuel characteris tics, and nutrients with respect to carbon and nitrogen have been analyzed. Emission ratios have been calculated relative to CO2. Results of the study suggested that fuel load ranged from 12-15.3 t ha(-1). Fire intensity at t he first site was 3207 kcal s(-1) m(-1) and 2882 kcal s(-1) m(-1) at the se cond site. The differences in the fuel moisture were found to be less than 10% at both of the sites. The CO/CO2 ratio at the two sites did not vary mu ch due to the low variation in moisture content. The carbon and nitrogen lo ads for the two sites ranged from 5603 t C ha(-1) to 286 t N ha(-1) and 636 4 t C ha(-1) and 239 N ha(-1), respectively. Using the relation of estimati ng the emission factor (EF) for estimating the NOx emissions EF(NOx)= - 1.5 +/- 3.9(nf), where, (r = 0.95) EF(NOx) is the emission factor for NOx in g rams of nitrogen per kilogram of dry matter (g N kg(-1) dm) burned and 'nf' is the percent of nitrogen bound within the plant matter, for tropical dec iduous forests, suggests an emission rate of 7.0 (g N kg(-1) dm) for the fi rst site, and 4.7 (g N kg(-1) dm) for the second site when compared to actu al measured emission rates of 4.8 (g N kg(-1) dm) for the first site and 3. 5 (g N kg(-1) dm) for the second site, indicating a higher estimate for the global regression relation used by Dignon and Penner. The emission factors computed from nitrogen content of the fuel material for tropical dry decid uous forests are nearer to the relation obtained for African Savanna fires. Comparison of the measured emission factors for the tropical deciduous for ests with other ecosystems has been made in the paper. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.