Sources and transport of Δ 14 C in CO 2 within the Mexico City Basin and vicinity

摘要: Abstract. Radiocarbon samples taken over Mexico City and the surrounding region during MILAGRO field campaign in March 2006 exhibited an unexpected distribution: (1) relatively few (23%) were below North American free tropospheric background value (57±2‰) despite fossil fuel emissions from one of world's most highly polluted environments; (2) frequent enrichment well above was observed. Correlate source tracer species air transport characteristics examined to elucidate influences on radiocarbon distribution. Our analysis suggests that a combination sources biased "regional background" thereby decreasing apparent signature. Likely include release 14C-enhanced carbon bomb 14C sequestered plant pools via ubiquitous biomass burning as direct CO2 other "hot" sources. Plausible perturbations local point hazardous waste cement kilns; medical incineration; Laguna Verde Nuclear Power Plant. These observations provide insight into use Δ14CO2 constrain megacity environment, indicating underestimation contribution flux is likely wherever coexists with urban unaccounted for elevated observed background. findings increase complexity required quantify fuel-derived source-rich environments characteristic megacities, have implications evaluating bottom-up emission inventories their reliability tool validating national claims within framework Kyoto Protocol.