Source apportionment of carbon monoxide over India: a quantitative analysis using MOZART-4.

Abstract

MOZART-4 chemistry transport model has been used to examine the contribution of carbon monoxide (CO) from different source regions/types by tagging their emissions in model simulations. These simulations are made using tagged tracer approach to estimate the relative contribution of different geographical regions and different emission sources, such as anthropogenic or biomass burning to the CO concentration at the surface, in the planetary boundary layer (PBL), and in the free troposphere (FT) over the Indian sub-continent. The CO budget analyses highlight the significant contribution of the Indian emissions on surface CO and influence of chemical production on the free tropospheric CO concentration. The total CO mixing ratio is estimated as 263 ± 139 parts per billion by volume (ppbv) for surface, 177 ± 71ppbv for PBL, and 112 ± 14ppbv for FT. The percentage contributions of primary sources are found to be 80%, 68%, and 53% at the surface, in the PBL, and in the FT, respectively. The sub-regional analysis of India shows that anthropogenic and photochemical processes contribute 41-75% and 15-46% CO, respectively, at the surface. Maximum percentage contribution of anthropogenic CO is observed over Indo-Gangetic Plain and Eastern India (75%). CO contribution from local anthropogenic and biomass burning emissions and transported from other global source regions are analyzed over the Indian region at the surface, in the PBL, and in the FT. The local anthropogenic sources contribute largest to the surface CO over India with 108ppbv, followed by China with 98ppbv, Europe with 55ppbv, North America (NA) with 46ppbv, and South-east Asia (SEA) and Middle East (ME) with 23ppbv each. India's PBL (FT) CO is mostly influenced by China's anthropogenic emissions with 12ppbv (8ppbv) followed by SEA with 7ppbv (6ppbv). Surface biomass burning CO over India (6ppbv) is much lower than in other regions such as SEA (32ppbv), Africa (24ppbv), and South America (11ppbv). In the PBL (FT), SEA and Africa's BB emissions show major impact on CO over India with 6ppbv (5ppbv) and 5ppbv (4ppbv), respectively.