title: Tropospheric GOM at the Pic du Midi Observatory-Correcting Bias in Denuder Based Observations.
abstract: Gaseous elemental mercury (GEM, Hg) emissions are transformed to divalent reactive Hg (RM) forms throughout the troposphere and stratosphere. RM is often operationally quantified as the sum of particle bound Hg (PBM) and gaseous oxidized Hg (GOM). The measurement of GOM and PBM is challenging and under mounting criticism. Here we intercompare six months of automated GOM and PBM measurements using a Tekran (TK) KCl-coated denuder and quartz regenerable particulate filter method (GOMTK, PBMTK, and RMTK) with RMCEMcollected on cation exchange membranes (CEMs) at the high altitude Pic du Midi Observatory. We find that RMTKis systematically lower by a factor of 1.3 than RMCEM. We observe a significant relationship between GOMTK(but not PBMTK) and Tekran flushTKblanks suggesting significant loss (36%) of labile GOMTKfrom the denuder or inlet. Adding the flushTKblank to RMTKresults in good agreement with RMCEM(slope = 1.01, r2= 0.90) suggesting we can correct bias in RMTKand GOMTK. We provide a bias corrected (*) Pic du Midi data set for 2012-2014 that shows GOM* and RM* levels in dry free tropospheric air of 198 ± 57 and 229 ± 58 pg m-3which agree well with in-flight observed RM and with model based GOM and RM estimates.
authors.affiliation: Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université de Toulouse, 14, avenue Édouard Belin, 31400 Toulouse, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Marusczak
authors.affiliation: Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université de Toulouse, 14, avenue Édouard Belin, 31400 Toulouse, France.
authors.forename: Jeroen E
authors.identifier: 0000-0001-7146-3035
authors.initials: JE
authors.lastname: Sonke
authors.affiliation: Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université de Toulouse, 14, avenue Édouard Belin, 31400 Toulouse, France.
authors.forename: Xuewu
authors.initials: X
authors.lastname: Fu
authors.affiliation: Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université de Toulouse, 14, avenue Édouard Belin, 31400 Toulouse, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Jiskra
mesh_terms: D000393:Air Pollutants; D004784:Environmental Monitoring; D005740:Gases; D008628:Mercury; D010084:Oxidation-Reduction
chemical_list: D000393:Air Pollutants; D005740:Gases; D008628:Mercury