Study of trace gases and aerosol emissions due to biomass burning at shifting cultivation sites in East Godavari District (Andhra Pradesh) during INDOEX IFP-99

Biomass burning in the tropics is a source of trace gas emissions and parti culate matter. The present study reports the results of the first field cam paign conducted over the two sites of shifting cultivation areas of tropica l dry deciduous forests in Eastern Chats, Andhra Pradesh, India, Trace gase s, viz. CO, CH4, NO, NO2, NOx, N2O and O-3 with respect to CO2 have been qu antified using online measurements and grab sampling in stainless steel can isters. Hand-held sun-photometer synchronous with satellite data have been used for studying the optical characteristics of the atmospheric aerosols e mitted from the biomass burning. The optical characteristics of the aerosol s had been used for correction of satellite data. The UV-B erythemal probe and UV-B biometer were used to measure the intensity of UV-B radiation and minimum erythemal dose. Results of the study suggested emission ratios for CO, CH4, NO,, and N2O during the burning to be about 12.3%, 1.29%, 0.29% an d 0.07% at the first site and 12.5%, 1.59%, 0.29% and 0.05% at the second s ite, suggesting low inter-fire variability among the sites. The variation h as been attributed to the fuel load, vegetation characteristics, site condi tions and local meteorological parameters affecting the relative amounts of combustion. The aerosol optical depth in five spectral bands have been fou nd to increase from 0.2-0.5 range to 2.0 during flaming and then came back to the normal range of 0.2-0.5. The maximum density of the aerosol particle s over the biomass burning sites is found to be in the range of 0.17-0.33 m um Comparison of the diurnal variation of the UV-B intensity over the burni ng sites with the ambient level reveals that there is reduction in the UV-B intensity peak during biomass burning phases. This reduction in UV-B inten sity had been found to be 35% and 53% over the two different sites selected . An attempt has been made to deduce the fluctuations in the selective abso rption of ozone at 297.5 nm in terms of the variability of UV-B intensity a t 297.5 nm. The total atmospheric ozone varied from 256 DU to 270 DU which were in accordance with the values for these latitudes. The relationship be tween UV-B intensity and aerosol optical depth values suggested a correlati on coefficient for ambient level (R-2 = 0.614) and (R-2 = 0.7387, R-2 = 0.5 88) for the two sites of biomass burning areas.