Air CO 2 extraction and measurement Air sampler is fabricated following a design developed by CSIRO (Francey et al., 1996), (Guha and Ghosh, 2012, under review) Collection of air samples During 2008 -2009 Evacuation method During 2009 -2011 Flush fill method using air sampler Extraction of CO 2 from the air samples collected During 2008 -2009 Glass extraction line During 2009 -2011 Stainless steel extraction line designed following a prototype at MPI (Werner et al., 2003),(Guha and Ghosh, 2012, under review) Lower value refers to depletion- indicating contribution from more fossil fuel combusted CO 2 Working gas is first scaled to VPDB using NBS19 and MARJ1 (used as primary standards) and finally the air samples are represented in VPDB scale Measurement of isotopic ratios of the extracted CO 2 using isotope ratio mass spectrometer (IRMS MAT253) 44, 45 , 46, 47, 48 & 49 masses of the extracted CO 2 is measured in the dual inlet peripheral against the working gas CO 2. to get the d 13 C of CO 2 which is further corrected for N 2 O contribution (Guha and Ghosh, 2012, under review) Calibration of experimental set up with international air standard JRAS air reference material: Set of JRAS reference material (JRAS MAR-J1 and JRAS OMC-J1) comes with assigned value, we have measured them again using our set up, the difference between these two measurements define the offset of our set up from international scale which is corrected latter for all the samples to represent them in internationally accepted scale for air CO 2 measurement Precision of measurement of both mixing ratio and d 13 C of CO 2 : During 2008 -2009 evacuation method in glass extraction line –------------------ ±9.3mmol.mol -1 & ±0.09‰ During 2009 end evacuation method in stainless steel extraction line –------------- ±7.6mmol.mol -1 & ±0.09‰ During 2009 -2011 evacuation method in stainless steel extraction line –------------- 7mmol.mol -1 & 0.05‰ Guha and Ghosh, 2012, under review Steady rise in CO 2 concentration leads to global warming Atmospheric CO 2 monitoring stations throughout the world Bangalore- urban station in India for monitoring of atmospheric CO 2 Diurnal variation: higher mixing ratio with depleted d 13 C of air CO 2 in the morning compared to afternoon Identification of isotopic ratio of the source CO 2 for the diurnal variation using Keeling approach based on inverse relation between mixing ratio and d 13 C of air CO 2 Location of our sampling station Indian Monsoon controlling the effect of anthropogenic emission on the seasonal variation of air-CO 2 over Bangalore, India Tania Guha 1 * & Prosenjit Ghosh 1# 1 Centre for Earth Sciences, Indian Institute of Science, Bangalore -560012, India *presenting author: [email protected]; [email protected] # [email protected] Identification of isotopic ratio of the source CO 2 for the seasonal scale variation using Keeling approach based on inverse relation between mixing ratio and d 13 C of air CO 2 Diurnal variation: average d 13 C value of source CO 2 is found to be -25‰ indicating fossil fuel, biomass burning or car exhaust as major sources of CO 2 Seasonal variation: average d 13 C value of source CO 2 is found to be -14.6‰ Three years (2008 -2011) of observations on diurnal and seasonal variation of air CO 2 from an urban station According to International Energy Agency India is the 4 th largest emitting country of greenhouse gasses and is mainly from coal based thermal power plants and biomass burning The source value identified based on seasonal data (-14.6 ± 0.7‰) is enriched compared to the value estimated based on diurnal variation. It showed the possibility of involvement of CO 2 emission from cement industry, where the source of CO 2 is basically limestone which is isotopically enriched (2.0‰). Using a conceptual two component mixing model, the proportional contribution of CO 2 emission from cement industry is identified for individual years. On seasonal scale, mixing ratio is found higher for the dry seasons compared to the wet seasons. The d 13 C of air-CO 2 reaches maxima during the late phase of wet seasons (Oct) and drops to minima during dry seasons (April, May). A steady rise in d 13 C of air-CO 2 is seen in the samples collected as southwest monsoon (SWM) advances. Seasonal scale-similar trend seen all years-lower amplitude in 2011-La Nina year-explained with reduced biomass burning and increased productivity as a consequence of prominent La Nina condition. Higher amplitude of seasonal-variation- compared to global-coastal-station- Cabo de Rama and Seychelles Acknowledgements: Dr. Willi Brand and his research group at MPI for the JRAS air reference material CSIRO Marine and Atmospheric Research - GASLAB, Aspendale, Victoria, Australia for permitting us to use the monthly flask data of air- CO 2 measurement for the station Cabo de Rama Global Monitoring Division of NOAA's Earth System Research Laboratory for providing air-CO 2 data for Seychelles and we further thank Institute for Arctic and Alpine Research at University of Colorado for the isotopic ratio data of air-CO 2 for the same Ministry of Earth Science, Government of India, project MoES/ATMOS/PP-IX/09 for funding Divecha Centre for Climate Change, IISc for financial support and Department of Science and Technology for funding the OASIS AIRMIX cylinder and IAEA standards Guha and Ghosh, 2012, under review