A study finds signatures of biogenic CO2 emissions in the Los Angeles area showing the contributions of the biological system to CO2 flux in an urban setting. Although megacities such as Los Angeles are significant sources of CO2, little is known about the relative contributions of fossil fuel combustion and biogenic CO2 from sources such as turf and trees. John B. Miller and colleagues tracked CO2 emissions and atmospheric carbon-14 isotope ratios, given that the latter is a signature of fossil fuel combustion, from 2014 to 2016. The authors found a seasonally variable cycle of biogenic CO2 emissions equivalent to 33% of fossil fuel emissions. Although the cycle was not synchronized with seasonal events such as wintertime rainfall, it was in phase with urban water usage, suggesting that irrigation of turf, trees, and other plants in the urban environment may be the main driver of the seasonal emissions cycle. According to the authors, the study reveals the presence of a previously unidentified and significant seasonal biogenic cycle of CO2 in the dry climate of Los Angeles and suggests that carbon emissions accounting for other cities in wet and dry climates should separate fossil and biogenic sources of carbon to better inform policy.
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Article #20-05253: "Large and seasonally varying biospheric CO2 fluxes in the Los Angeles megacity revealed by atmospheric radiocarbon," by John B. Miller et al.
MEDIA CONTACT: John B. Miller, NOAA Global Monitoring Laboratory, Boulder, CO; e-mail: < John.B.Miller@noaa.gov >
Proceedings of the National Academy of Sciences