CO/FFCO 2 RATIOS DERIVED FROM RADIOCARBON OBSERVATIONS - THE ROLE OF BIOSPHERIC COMPONENT KAZIMIERZ ROZANSKI AGH University of Science and Technology Krakow, Poland Krakow, Poland CarboEurope-IP Annual Meeting Poznan,

WP2.6 Objectives:  Continue the existing 14 CO 2 observation network in Europe to derive the monthly mean in Europe to derive the monthly mean fossil fuel CO 2 component at polluted fossil fuel CO 2 component at polluted and background sites and background sites  Ongoing calibration of CO as a proxy for fossil fuel CO 2 at 4 sites in Eastern and Western Europe CO 2 at 4 sites in Eastern and Western Europe (Heidelberg, Krakow, Trainou Tower and Lutjewad) (Heidelberg, Krakow, Trainou Tower and Lutjewad)

METHODOLOGY: BALANCE EQUATIONS: CO 2mix = CO 2bgd +  CO 2bio) +  CO 2fossil (1) CO 2mix (  14 CO 2mix +1000) = CO 2bgd (  14 CO 2bgd +1000) CO 2mix (  14 CO 2mix +1000) = CO 2bgd (  14 CO 2bgd +1000) +  CO 2bio (  14 CO 2bio +1000) +  CO 2bio (  14 CO 2bio +1000) +  CO 2fossil (  14 CO 2fossil +1000) (2) +  CO 2fossil (  14 CO 2fossil +1000) (2) FFCO 2 = CO 2mix [(  14 CO 2bgd -  14 CO 2mix )/(  14 CO 2bgd )] FFCO 2 = CO 2mix [(  14 CO 2bgd -  14 CO 2mix )/(  14 CO 2bgd )]ASSUMPTIONS: (1)  14 C fossil = (2)  14 C bio =  14 C bgd (3) Regional background: Jungfraujoch (  14 C bgd, CO bgd ) BALANCE EQUATIONS: CO 2mix = CO 2bgd +  CO 2bio) +  CO 2fossil (1) CO 2mix (  14 CO 2mix +1000) = CO 2bgd (  14 CO 2bgd +1000) CO 2mix (  14 CO 2mix +1000) = CO 2bgd (  14 CO 2bgd +1000) +  CO 2bio (  14 CO 2bio +1000) +  CO 2bio (  14 CO 2bio +1000) +  CO 2fossil (  14 CO 2fossil +1000) (2) +  CO 2fossil (  14 CO 2fossil +1000) (2) FFCO 2 = CO 2mix [(  14 CO 2bgd -  14 CO 2mix )/(  14 CO 2bgd )] FFCO 2 = CO 2mix [(  14 CO 2bgd -  14 CO 2mix )/(  14 CO 2bgd )]ASSUMPTIONS: (1)  14 C fossil = (2)  14 C bio =  14 C bgd (3) Regional background: Jungfraujoch (  14 C bgd, CO bgd ) I. DERIVING LOCAL FFCO 2 (  CO 2fossil )

II. LOCAL  CO:  CO = CO mix - CO bgd III. LOCAL  CO/FFCO 2 RATIOS

Monthly  CO/FFCO 2 ratios in Krakow: 1992 – 1996 and  5.3 (ppb/ppm) 29.9  1.6 (ppb/ppm)

filter molecular diaphragm sieve pump CO 2 flowmeter silica gel Radiocarbon content of soil CO 2 flux ? Is the assumption  14 C bio =  14 C bgd valid ? Monthly ”composite” samples

Three sites with different soil characteristics: - mixed forest - mixed forest - agriculture field - agriculture field - grassland (not cultivated) - grassland (not cultivated)

Grassland site (Krakow)

CAB SDBFDB F f (1) F out FrFr FofFof FosFos F f (2) F f (n) FfFf F cw F in F s (1) F s (2) F s (n) FsFs TERRESTRIAL BIOSPHERE RRB ATMOSPHERE MODEL: F out (t) = F fast (t) + F slow (t) + F r (t) 14 A out (t) =  1 (t)  14 A fast (t) +  2 (t)  14 A slow (t) +  3  14 A r (t)

MODEL RESULTS: MRT fast = 14 years MRT slow = 1500 years Forest: M slow /M fast = 40 Grassland: M slow /M fast = 22

 14 C bio   14 C mix NEW ASSUMPTION: FFCO 2 = CO 2bgd [(  14 CO 2bgd -  14 CO 2mix )/(  14 CO 2mix )]  14 C bio =  14 C bgd X

Differences between FFCO 2 estimates

No a priori assumption about  14 C bio : FFCO 2 = CO 2mix [(  14 CO 2bio -  14 CO 2mix )/(  14 CO 2bio )] + CO 2bgd [(  14 CO 2bgd -  14 CO 2bio )/(  14 CO 2bio )] + CO 2bgd [(  14 CO 2bgd -  14 CO 2bio )/(  14 CO 2bio )] For  14 CO 2bio =  14 CO 2bgd + 40

SUMMING UP:  R adiocarbon content of soil CO 2 flux introduce additional uncertainty in the estimates of FFCO 2 which is difficult to eliminate.  However, it turnes out that radiocarbon-based FFCO 2 estimates are relatively insensitive to actual radiocarbon content of the biospheric component. For the current levels of FFCO 2 this additional uncertainty is in the order of ppm.  The modified formula for calculating FFCO 2 (assumption:  14 C bio   14 C mix ) opens up attractive possibilities for monitoring FFCO 2 variations with relatively good precision, even without regular high-precision observations of CO 2 concentations at those sites.

FFCO 2 KRAKOW