title: Continued emissions of carbon tetrachloride from the United States nearly two decades after its phaseout for dispersive uses.
abstract: National-scale emissions of carbon tetrachloride (CCl4) are derived based on inverse modeling of atmospheric observations at multiple sites across the United States from the National Oceanic and Atmospheric Administration's flask air sampling network. We estimate an annual average US emission of 4.0 (2.0-6.5) Gg CCl4 y(-1) during 2008-2012, which is almost two orders of magnitude larger than reported to the US Environmental Protection Agency (EPA) Toxics Release Inventory (TRI) (mean of 0.06 Gg y(-1)) but only 8% (3-22%) of global CCl4 emissions during these years. Emissive regions identified by the observations and consistently shown in all inversion results include the Gulf Coast states, the San Francisco Bay Area in California, and the Denver area in Colorado. Both the observation-derived emissions and the US EPA TRI identified Texas and Louisiana as the largest contributors, accounting for one- to two-thirds of the US national total CCl4 emission during 2008-2012. These results are qualitatively consistent with multiple aircraft and ship surveys conducted in earlier years, which suggested significant enhancements in atmospheric mole fractions measured near Houston and surrounding areas. Furthermore, the emission distribution derived for CCl4 throughout the United States is more consistent with the distribution of industrial activities included in the TRI than with the distribution of other potential CCl4 sources such as uncapped landfills or activities related to population density (e.g., use of chlorine-containing bleach).
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305; leihutx@gmail.com Stephen.A.Montzka@noaa.gov.
authors.forename: Lei
authors.initials: L
authors.lastname: Hu
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305; leihutx@gmail.com Stephen.A.Montzka@noaa.gov.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Montzka
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Ben R
authors.initials: BR
authors.lastname: Miller
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Arlyn E
authors.initials: AE
authors.lastname: Andrews
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: John B
authors.initials: JB
authors.lastname: Miller
authors.affiliation: Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO 80309;
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Lehman
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Colm
authors.initials: C
authors.lastname: Sweeney
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford University, Stanford, CA 94305;
authors.forename: Scot M
authors.initials: SM
authors.lastname: Miller
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Kirk
authors.initials: K
authors.lastname: Thoning
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Carolina
authors.initials: C
authors.lastname: Siso
authors.affiliation: Rosenstiel School of Marine & Atmospheric Science, University of Miami, Miami, FL 33149;
authors.forename: Elliot L
authors.initials: EL
authors.lastname: Atlas
authors.affiliation: School of Physical Sciences, University of California, Irvine, CA 92697;
authors.forename: Donald R
authors.initials: DR
authors.lastname: Blake
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Joost
authors.initials: J
authors.lastname: de Gouw
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Jessica B
authors.initials: JB
authors.lastname: Gilman
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Geoff
authors.initials: G
authors.lastname: Dutton
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: James W
authors.initials: JW
authors.lastname: Elkins
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Bradley
authors.initials: B
authors.lastname: Hall
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Center for Isotope Research, Energy and Sustainability Research Institute Groningen, University of Groningen, 9747 AG, Groningen, The Netherlands;
authors.forename: Huilin
authors.initials: H
authors.lastname: Chen
authors.affiliation: Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Marc L
authors.initials: ML
authors.lastname: Fischer
authors.affiliation: Atmospheric and Environmental Research, Lexington, MA 02421;
authors.forename: Marikate E
authors.initials: ME
authors.lastname: Mountain
authors.affiliation: Atmospheric and Environmental Research, Lexington, MA 02421;
authors.forename: Thomas
authors.initials: T
authors.lastname: Nehrkorn
authors.affiliation: Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Sebastien C
authors.initials: SC
authors.lastname: Biraud
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309; Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Fred L
authors.initials: FL
authors.lastname: Moore
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Pieter
authors.initials: P
authors.lastname: Tans
keywords: United States; carbon tetrachloride; emissions; greenhouse gases; ozone-depleting substances