Air CO2 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 CO2 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

CO2

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 CO2 using isotope ratio mass

spectrometer (IRMS MAT253)

44, 45 , 46, 47, 48 & 49 masses of the extracted CO2 is measured in the dual inlet peripheral against the working

gas CO2. to get the d13C of CO2 which is further corrected for N2O 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 CO2 measurement

Precision of measurement of both mixing ratio and d13C of CO2 :

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

CO2

concentration

leads to global

warming

Atmospheric CO2

monitoring stations

throughout the

world

Bangalore-

urban station

in India for

monitoring of

atmospheric

CO2

Diurnal variation: higher mixing ratio

with depleted d13C of air CO2 in the

morning compared to afternoon Identification of isotopic ratio of the

source CO2 for the diurnal variation

using Keeling approach based on

inverse relation between mixing ratio

and d13C of air CO2

Location of our sampling station

Indian Monsoon controlling the effect of anthropogenic emission on the seasonal variation of air-CO2 over Bangalore, India

Tania Guha1* & Prosenjit Ghosh1#

1Centre for Earth Sciences, Indian Institute of Science, Bangalore -560012, India

*presenting author: guha.tania@gmail.com; tania@ceas.iisc.ernet.in # pghosh@ceas.iisc.ernet.in

Identification of isotopic ratio of

the source CO2 for the seasonal

scale variation using Keeling

approach based on inverse

relation between mixing ratio and

d13C of air CO2

Diurnal variation: average d13C value

of source CO2 is found to be -25‰

indicating fossil fuel, biomass burning

or car exhaust as major sources of

CO2

Seasonal

variation:

average d13C

value of source

CO2 is found to

be -14.6‰

Three years (2008 -2011) of observations on diurnal and seasonal variation of air CO2

from an urban station According to International Energy Agency India is the 4th 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 CO2 emission from cement

industry, where the source of CO2 is basically limestone which is

isotopically enriched (2.0‰).

Using a conceptual two component mixing model, the proportional

contribution of CO2 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

d13C of air-CO2 reaches maxima during the late

phase of wet seasons (Oct) and drops to minima

during dry seasons (April, May). A steady rise in

d13C of air-CO2 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-

CO2 measurement for the station Cabo de Rama

Global Monitoring Division of NOAA's Earth System Research Laboratory for providing air-CO2 data for Seychelles and we further thank

Institute for Arctic and Alpine Research at University of Colorado for the isotopic ratio data of air-CO2 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