A seven-year record (2006-2013) of nonmethane hydrocarbons (NMHCs) - PowerPoint PPT Presentation

A seven-year record (2006-2013) of nonmethane hydrocarbons (NMHCs) in the subtropical marine boundary layer at the Cape Verde Atmospheric Observatory (CVAO) S.Punjabi, K.A. Read, L.J. Carpenter, J.R. Hopkins, and A.C. Lewis - NCAS, University of York Steve Arnold - Earth and Environment, University of Leeds M.Heimann – Max-Planck -Institute for Biogeochemistry,Jena, Germany E.A Kozlova- College of Life and Environmental Sciences, Exeter Luis Mendes - INMG, Cape Verde NOAA ESRL GMAC Boulder, May 21, 2014

Cape Verde Observatory- A GAW Global status station • Eastern tropical North Atlantic (ETNA)- 16 ° 52' N, 24 ° 52' W • Long range transport and atmospheric - ocean exchange of trace chemicals • Remote marine boundary location • Measurement started Oct 2006 • Diverse trade winds arriving at site (North America, Arctic, European and African regions) https://www.ncas.ac.uk/index.php/en/cvao-home

Measurements and campaigns at site Ground based long term measurements Seasonal • Met data at 4m, 10m and 30m Oxidant Study • Solar radiation campaign 2009 • J O 1 D • O 3, • CO Aircraft based field • NO, NO 2 ,NOy campaign • C 2 -C 8 NMHCs and DMS • Methanol, acetone and acetaldehyde • Halocarbons Oceanic Reactive • Mercury Carbon 3 Project hosted international field projects June and Sep 2014 RHaMBLE 2007 staff at site Ship based measurements Ship based Met and data measurements logger/server

Instrument involved during measurement period (Oct 2006- May 2013) In-situ sampling from 10-m tower Water trap 50m PLOT Dual-bed FlD 1 column adsorbent trap 10m LOWOX FID 2 column Agilent 6890

Since June 2013 instrument upgrade Sterling coolers MARKES UNITY Preconcentration unit Agilent 7890 CIA8 Autosampler Commercial preconcentration and autosampler system : MARKES Thermal Desorbtion unit (TDU)

Calibration over time ethane and area per ppb per ml ethane R.F per ml by ben s.r AR 54 component, hydrogen gen trap/column/split ratio change Rezero MFCs NPL 30 component 2009 New restrictor for oVOC channel New restrictor and leak fixed NPL 30 component 2012 switch to hydrogen gas cylinder 0.0300 GC Werks automatic integration 0.0250 area per ppb per ml 0.0200 0.0150 0.0100 0.0050 0.0000 May-05 Oct-06 Feb-08 Jul-09 Nov-10 Apr-12 Aug-13 Dec-14 years

Results of WMO/GAW audit for VOC -2009

Comparison of calibration responses between old and new instrument NPL 2009 on Agilent 6890 2.50 Effective C atom response relative to butane NPL CV 2012 on Agilent 6890 NPL CV 2012 on Marks Unity agilent 7890 instrument avg ECR ethane to n pentane 2.00 1.50 1.00 0.50 0.00 propane propene iso-butane n-butane ethane ethene acetylene iso-pentane n-pentane

Data and time series ethane propane CO 2500 180 160 2000 140 [ethane] [propane] pptv 120 1500 [CO] ppbv 100 80 1000 60 40 500 20 0 0 Jul-06 Jul-07 Jul-08 Jul-09 Jul-10 Jul-11 Jul-12 Jul-13 Jul-14 Spring maxima and summer minima : in line with the Northern Hemisphere observations Rise in amplitude suggests a change in source strength or OH?

Ethane and CH 4 growth rate Ethane ∆ CH 4 (Monthly mean - 5 year running mean) Methane data from M. Heimann, Jena 2000 60 2500 50 methane growth rate ppbv per year 1800 50 methane growth rate ppbv per year 40 1600 40 2000 30 1400 30 20 [ethane] pptv ethane [ppt] 1200 20 1500 10 1000 10 0 1000 800 0 -10 600 -10 -20 500 400 -20 -30 200 -30 0 -40 0 -40 Oct-06 Feb-08 Jul-09 Nov-10 Apr-12 Aug-13 Dec-14 Jul-06 Nov-07 Mar-09 Aug-10 Dec-11 May-13 Sep-14 • Methane atomspheric growth rate is a sensitive indicator of fluctuations in methane ’ s emissions. • 1985-2010 saw global ethane decline of 190 pptv (24%) (Simpson et al., Nature, 2012) • Declining fugitive fossil fuel emissions Long-term decline of global atmospheric ethane concentrations and implications for methane , Simpson et al , Nature 488 , 490–494 (23 August 2012) doi:10.1038/nature11342

Model ( CAM- Chem) and measurment comparison and emission contributions The model suggests that alkanes at Cape Verde are dominated by Courtesy: Steve Arnold the anthro + biofuel sector (bioethanol is widely used in USA) Read K.A; Carpenter L.J; Hopkins J.R; Lewis A.C; Lee J.D; Arnold S.R ; Pickering S.J; Beale R; Nightingale P.D; Mendes L (2012) Multiannual observations of acetone, methanol, and acetaldehyde in remote tropical Atlantic air: Implications for atmospheric OVOC budgets and oxidative capacity, Environmental Science and Technology , 46 , pp.11028-11039. doi: 10.1021/es302082p

Constraining global benzene emissions using Cape Verde 1600 1400 1200 [Benzene] (pptv) 1000 800 600 400 y = 1.402x - 108.605 200 R 2 = 0.972 0 0 300 600 900 1200 [CO] (ppbv) Derive Emission Ratios of benzene to CO Starting point – boreal plume (plus use literature values) observations from aircraft GEOSChem Model – Tagged benzene (scaled to GFED3 CO) + RETRO anthropogenic benzene The influence of biomass burning on the global distribution of selected non-methane organic compounds, Lewis , A..C et al Atmos. Chem. & Phys . 13 , 851-867, 2013

Constraining global benzene emissions using Cape Verde • Cape Verde influenced by both biomass burning and anthropogenic benzene. • Model / measurement comparison shows overestimation. • Better fit using RETRO x 0.33 or 0.25 • Reducing RETRO is consistent with major reduction in fuel benzene since 2000. Biomass burning Biomass burning + RETRO 2000 + 0.25 RETRO 2000 Biomass burning + 0.33 RETRO 2000 Cape Verde Observations Biomass only The influence of biomass burning on the global distribution of selected non-methane organic compounds, Lewis , A.C et al Atmos. Chem. & Phys . 13 , 851-867, 2013

Impact of biomass burning on GAW stations • Estimated fraction of benzene from biomass burning / anthropogenic arriving at 27 GAW Global stations is calculated. • Most GAW stations affected significantly in at least one month of the year, biomass influence becomes more pronounced as anthropogenic emissions of benzene decline. The influence of biomass burning on the global distribution of selected non-methane organic compounds, Lewis , A.C et al Atmos. Chem. & Phys . 13 , 851-867, 2013

Further plans • Continuing with long-term measurements programme • Rigorous checks to ensure data quality