Changes in mixing ratio and isotopic composition of CO₂ in urban air from the Los Angeles basin, California, between 1972 and 2003

Abstract

Atmospheric CO2 mixing ratios and C and O isotopic compositions are reported for the Los Angeles basin in southern California, a region renowned for its air pollution. Air samples collected midday on the Caltech campus in Pasadena, California, contained ∼30 ppm more CO2 in 1998–2003 than in 1972–1973 (averaging 397 ppm in 1998–2003 and 366 ppm in 1972–1973) compared to a 47 ppm change in background air CO2, yet the ranges of the carbon and oxygen isotopic compositions remained essentially constant. Because the 1998–2003 data show a significant progression through time, analysis was done on data from 2002 to 2003 complete calendar years (CO2 mixing ratios increased 41 ppm between 1972 and 1973 and 2002–2003). Both 1972–1973 and 2002–2003 data sets display significant correlation between δ13C and 1/[CO2] with local CO2 source end‐member δ13C values of −30.9 ± 0.5‰ for 1972–1973 and −29.9 ± 0.2‰ for 2002–2003 (1σ errors). Mass balance calculations explain that this apparently coincidental similarity reflects a change in the relative proportion of natural gas and petroleum products burned in the region combined with a change in the origin, and thus isotopic composition, of the petroleum burned. The δ13C of the average CO2 inventory in Pasadena can be explained by local addition to background air of 38 ± 4 ppm CO2 in 1972–1973 and 29 ± 3 ppm in 2002–2003 from anthropogenic sources, in seeming contradiction to the known increase in CO2 emissions between these two time periods.

Mixing ratio and carbon isotopic composition investigation of atmospheric CO 2 in Beijing, China

“…On the diurnal time scale, δ 13 C S variability can be affected by the atmospheric mixing condition variation and the distribution of CO 2 sources (Wada et al, 2011;Sturm et al, 2006). In Wrocław, Poland and the Los Angeles basin, USA, the δ 13 C S differences over different time periods indicate changes in energy usage patterns (Gorka and Lewicka-Szczebak, 2013;Newman et al, 2008). In this study, the consistent δ 13 C S values of heating seasons I and II indicate that local energy consumption did not change during this period.…”

“…Measurements of δ 13 C only have been performed at 4 sites: Dallas, Texas, USA (Clark- Thorne and Yapp, 2003); Paris, France (Lopez et al, 2013;Widory and Javoy, 2003); Bangalore City, Karnataka State, India (Guha and Ghosh, 2010); and Wrocław, Poland (Gorka and Lewicka-Szczebak, 2013). Both δ 13 C and δ 18 O observations have been conducted at another 4 sites: Kraków, Poland (Zimnoch et al, 2012, Zimnoch et al, 2004; Bern, Switzerland (Sturm et al, 2006); and Los Angeles Basin, California, USA (Djuricin et al, 2010;Newman et al, 2008). Only 3 urban sites have had long-term continuous observations of the mixing ratio and isotopic composition by IRIS technology.…”

Surface observations for monitoring urban fossil fuel CO2 emissions: Minimum site location requirements for the Los Angeles megacity

“…[20] Observations have been made discontinuously at Caltech since the early 1970s [Newman et al, 2008]. Analysis of carbon isotopes from whole air flask samples has been performed to assess the observed CO 2 attributable to local emissions, and it was found that~10 ppm more CO 2 was attributable to local emissions in the 1970s than the early 2000s, in seeming contrast to the known emissions increase in that time frame [Newman et al, 2008].…”

“…Analysis of carbon isotopes from whole air flask samples has been performed to assess the observed CO 2 attributable to local emissions, and it was found that~10 ppm more CO 2 was attributable to local emissions in the 1970s than the early 2000s, in seeming contrast to the known emissions increase in that time frame [Newman et al, 2008]. This finding can possibly be explained by analysis of the footprint of the Caltech site, seen in Figure 2a.…”

Carbon Dioxide in the Free Troposphere and Boundary Layer at the Mt. Bachelor Observatory

“…Numerous types of sites have been used to measure atmospheric CO 2 , such as: surface observatories (Idso et al, 2001;Newman et al, 2008;Ramonet et al, 2010;Rice and Bostrom, 2011;Pérez et al, 2012), balloon soundings (Bischof et al, 1980;Li et al, 2014), aircraft measurements (Bischof et al, 1980;Lloyd et al, 2002;Machida et al, 2002;Sidorov et al, 2002;Gurk et al, 2008;Shashkov et al, 2011;Sun and De Wekker, 2011;Sweeney et al, 2015), tall towers (Bakwin et al, 1995;Haszpra et al, 2005;Haszpra et al, 2012), and mountain-top observatories (Goldman, 1974;Thoning et al, 1989;Sturm et al, 2005;De Wekker et al, 2009;Ramonet et al, 2010;Brooks et al, 2012). Even though there are numerous methodologies for the measurement of CO 2 and data on atmospheric CO 2 concentrations have been available since the late 1950s, atmospheric chemistry models still have difficulty estimating CO 2 concentrations in conditions other than in a well-mixed planetary boundary layer (Haszpra et al, 2012).…”