Abstract
The CalNex 2010 (California Research at the Nexus of Air Quality and Climate Change) study was designed to evaluate the chemical composition of air masses over key source regions in California. During May to June 2010, air samples were collected on board a National Oceanic and Atmospheric Administration (NOAA) WP‐3D aircraft over the South Coast Air Basin of California (SoCAB) and the Central Valley (CV). This paper analyzes six effective greenhouse gases—chlorodifluoromethane (HCFC‐22), 1,1‐dichloro‐1‐fluoroethane (HCFC‐141b), 1‐chloro‐1,1‐difluoroethane (HCFC‐142b), 2‐chloro‐1,1,1,2‐tetrafluoroethane (HCFC‐124), 1,1,1,2‐tetrafluoroethane (HFC‐134a), and 1,1‐difluoroethane (HFC‐152a)—providing the most comprehensive characterization of chlorofluorocarbon (CFC) replacement compound emissions in California. Concentrations of measured HCFCs and HFCs are enhanced greatly throughout the SoCAB and CV, with highest levels observed in the SoCAB: 310 ± 92 pptv for HCFC‐22, 30.7 ± 18.6 pptv for HCFC‐141b, 22.9 ± 2.0 pptv for HCFC‐142b, 4.86 ± 2.56 pptv for HCFC‐124, 109 ± 46.4 pptv for HFC‐134a, and 91.2 ± 63.9 pptv for HFC‐152a. Annual emission rates are estimated for all six compounds in the SoCAB using the measured halocarbon to carbon monoxide (CO) mixing ratios and CO emissions inventories. Emission rates of 3.05 ± 0.70 Gg for HCFC‐22, 0.27 ± 0.07 Gg for HCFC‐141b, 0.06 ± 0.01 Gg for HCFC‐142b, 0.11 ± 0.03 Gg for HCFC‐124, 1.89 ± 0.43 Gg for HFC‐134a, and 1.94 ± 0.45 Gg for HFC‐152b for the year 2010 are calculated for the SoCAB. These emissions are extrapolated from the SoCAB region to the state of California using population data. Results from this study provide a baseline emission rate that will help future studies determine if HCFC and HFC mitigation strategies are successful.
Highlights
Barbara Barletta,1 Marc Carreras-Sospedra,2 Alex Cohan,2 Paul Nissenson,3 Donald Dabdub,2 Simone Meinardi,1 Elliot Atlas,4 Rich Lueb,4,5 John S
AB 32 will reduce Greenhouse gas (GHG) emissions down to 422 million metric tons of carbon dioxide equivalent (MMTCO2eq; amount of CO2 released into the atmosphere that would have the same warming influence as a given pulse emission of another greenhouse gas integrated over a specific time scale, commonly set to 100 years) by 2020, a 15% reduction from 2002 to 2004 levels (496 MMTCO2eq) and a 30% reduction from the “business-as-usual” scenario projected for 2020 (596 MMTCO2eq)
The difference between the background concentrations observed during the CalNex campaign and at Trinidad Head are less than 2% for HCFC-141b, ~7% for HFC-152a and HCFC-142b, and ~10% for HFC-134a and HCFC-141b
Summary
Emission rates of 3.05 Æ 0.70 Gg for HCFC-22, 0.27 Æ 0.07 Gg for HCFC-141b, 0.06 Æ 0.01 Gg for HCFC-142b, 0.11 Æ 0.03 Gg for HCFC-124, 1.89 Æ 0.43 Gg for HFC-134a, and 1.94 Æ 0.45 Gg for HFC-152b for the year 2010 are calculated for the SoCAB These emissions are extrapolated from the SoCAB region to the state of California using population data. In September 2006, Assembly Bill 32 (AB 32, the Global Warming Solutions Act of 2006) was signed into law to address GHG emissions from California [CARB, 2008]. This law requires the California Air Resources Board (CARB) to develop regulations to reduce California’s GHG emissions to 1990 levels by the year 2020. The main strategies California will employ to achieve the 2020 GHG emissions target are included in the scoping plan approved by CARB on December 2008 (http://arb.ca.gov/cc/scopingplan/scopingplan.htm) and are scheduled to be implemented by 2012
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