Iron solubility in mineral dust and aerosol generated from soil samples

Ironsolubilityinmineraldustand aerosolgeneratedfromsoil samples TesisdemásterrealizadaporVanesadelPilarJerezSarmiento Tutora:MaríaDoloresGelado Caballero MásterenOceanografía 19deDiciembrede2013 Index 1. Introduction 2. Methodology 2.1.Samplingsites 2.2.Method 2.3.Airmassclassification 2.4.DryDepositionsamplescharacteristics 3. Resultsanddiscussion 4. PreliminaryConclusions 1.Introduction Fe Biological role Essential nutrient Enzyme systems Photosynthesis Respiration Primary Production Nitrogen fixation (PP) [MorelandPrice,2003; Jickells etal.,2005] Other cycles interaction Carbon Sulphur Nitrogen Phosphorus Climate system influence Feavailability limiting factorfor PP e.g.HNLCregions carbon fixation/CO2 consumption [Martinetal.,1991] 1.Introduction TheIroncycle[Raiswell etal.,2012] Global iron fluxes to the ocean [Jickells et al., 2005] Source Flux (Tg Feyear‐1) Fluvialparticulate totaliron 625to 962 Fluvialdisolvediron 1.5 Glacialsediments 34to 211 Atmospheric 16 Coastal erosion 8 Hydrotermal 14 Authigenic 5 Atmospheric dust input  GlobalImpact 1.Introduction Conceptual diagram illustrating the main issues, processes and species relating to the SOLAS EBUSs and OMZs research programmes. Processes are indicated in italic. [Evolving Research Directions in Surface Ocean‐Lower Atmosphere (SOLAS) Science by Cliff Law et al. in Environmental Chemistry 2013, 10, 1‐16] Bioavailable FesolubleFe(FeS) [Journet etal.,2008] Predominant specie Fe(III):highly insoluble Solublespecie Fe(II):un‐stable 1.Introduction ImágenesdelsatéliteEarthProbe •generatedfromsoils •Chemicalandmineralogicalcompositionconditionedforplaceorigin Mainmineral:quartz,clay,calcilte,gibbsiteandFeoxides •Sizeparticleconditioneddistancetransport(meansize0.1‐10m) Mineralaerosol 1.Introduction Atmosphericprocesses  changeFesolubility •Gravitationalsettling •Mixingwithanthropogenic andbiomassburningaerosols •Uptakeofacidicgases •Photoreduction Fesolubility (FeS) pHCloudprocesses FeS insoils<0.1%vs 80%FeS inaerosolsoverremoteocean [BakerandJickells,2006:Maholwald etal.,2009;Shi etal.,2012] 1.Introduction http://fiji.ucsd.edu/~greg/streamwiseCCN.htm •Main mechanism for uptake: CO2,SOx,NOx,… [Seinfeld andPandis,2006] Dust particles ascloud condensation nuclei (CNN) •Several condensation andevaporation cyles pH •Evaporation step pH<3the highest Fesolubility dust/liquid ratio Ionic strength pH Objectives 1. FespeciationinaerosolscollectedintheCanaryIslands 2. FespeciationinAfricansoils 3. Reproduceaerosols“precursors”throughachemical processinsoils 4. Validate whethertheseaerosolprecursorshavethesame speciationthataerosolscollectedinCanaryIslands 2.Methodology 2.3.Airmass classification Airmassidentificationclassificationofdifferentbacktrajectoriesoftheair masseswithendpointatGranCanaria.Geographicsectors:(a)SH(Sahel:0°– 20°N,18°W–20°E),(b)WCS(WestandCentralSahara:20°N– 30°N,18°W– 20°E),(c)NS(NorthofSahara:38°N–30°N,18°W–15°E),(d)EUR(airmasses overcontinentalEuropeandtheAtlanticOcean)and(e)MAR(trajectories overtheAtlanticocean)[Gelado – Caballeroetal.,2012]. 5geographicsectors: •SHsector(Sahel:00‐200N,180W‐ 200E) •WCS(WestandCentralSahara: 20‐300N,180W‐200E) •NS(NorthernSahara:380‐300N, 180W‐150E,NorthMorocco,North AlgeriaandTunisia) •EUR(Europeanandmaritime aerosol,trajectoriesthatcrossthe EuropeancontinentandAtlantic ocean) •MAR(maritimeaerosol, trajectoriesovertheAtlantic ocean) 2.Methodology 2.4.Dry Deposition samples characteristics 0 10 20 30 40 50 60 70 80 90 100 DD1 DD2 DD3 DD4 DD5 DD6 DD7 Days/airmassinDDsamples(%) AFRICAN EUR MAR Percentageofdaysforeachoriginoftheairmassesinthedrydepositionsamples(African,Europeanandmarine) 2.Methodology 2.4.Dry Deposition samples characteristics 04 05 06 07 08 09 10 11 12 13 Flux (mg m-2 d-1) 0 100 200 300 400 TSP (g m-3) -300 -200 -100 0 100 200 300 Dry flux Wet flux Average TSP DD5 DD2 DD3 DD1 DD7 DD4 DD6 FeT(mgg‐1)FeS(mgg‐1)%FeS DD1 43.59 0.19 0.44 DD2 46.74 0.28 0.60 DD3 36.77 0.08 0.23 DD4 61.01 0.28 0.46 DD5 47.81 0.25 0.53 DD6 54.80 0.36 0.65 DD7 39.90 0.27 0.68 L23' 31.57 0.21 0.67 L23 31.75 0.06 0.19 Hematite 469.14 0.03 0.01 Illite 41.67 0.75 1.79 Vermiculite 48.87 0.23 0.46(n=1) Muscovite 22.42 0.003 0.001(n=1) 3.Results anddiscussion FeS % Fe Total 110100 % Fe Soluble 0 1 2 3 L23 L23´ DD Illite Vermiculite Hematite Muscovite Aerosols-Tafira Aerosols-Pico de la Gorra % S ol. Fe Total Al (µg m -3) 02468101214 0 5 10 15 20 25 MAR EUR African dust FeS DDFeS 0.49%(±0.18) 3.Results anddiscussion Sample FeT (mgFe/g sample) FeA (mgFe/g sample) Fe–NaOAc (mgFe/g sample) FeD (mgFe/g sample) FeA/FeT (%) Fe‐ NaOAc/FeT (%) FeD/FeT (%) (FeA+FeD)/ FeT (FreeFe Ratio) FeA/(FeA + FeD) (%) DD1 43.59 (±0.25,n=3) 0.23 (±0.03,n=3) 0.15 (±0.01,n=3) 35.20 (±7.97,n=3) 0.53 (±0.06,n=3) 0.34 (±0.03,n=3) 80.75 (±18.30,n=3) 0.81 (±0.18,n=3) 0.65 (±0.05,n=3) DD2 46.74 (±1.15,n=2) 0.56 (± 0.01,n=3) 0.10 (±0.02,n=3) 14.85 (±0.93,n=3) 1.20 (±0.02,n=3) 0.21 (±0.04,n=3) 31.78 (±1.99,n=3) 0.33 (±0.02,n=3) 3.65 (±0.29,n=3) DD3 36.77 (n=1) 0.25 (±0.03,n=3) 0.13 (±0.02,n=3) 5.26 (±0.81,n=3) 0.68 (±0.08,n=3) 0.35 (±0.04,n=3) 14.30 (±2.20,n=3) 0.15 (±0.02,n=3) 4.61 (±0.63,n=3) DD4 61.01 (n=1) 0.85 (±0.04,n=3) 0.23 (±0.02,n=3) 6.64 (±0.51,n=3) 1.39 (±0.06,n=3) 0.37 (±0.03,n=3) 10.89 (±0.83,n=3) 0.12 (±0.01,n=3) 11.36 (±1.09,n=3) DD5 47.81 (n=1) 0.59 (±0.03,n=3) 0.24 (±0.04,n=3) 17.90 (±2.54,n=3) 1.24 (±0.06,n=3) 0.51 (±0.08,n=3) 37.45 (±5.32,n=3) 0.39 (±0.05,n=3) 3.24 (±0.54,n=3) DD6 54.80 (n=1) 0.52 (±0.19,n=3) 0.50 (±0.16,n=3) 15.82 (±1.93,n=3) 0.94 (±0.34,n=3) 0.91 (±0.28,n=3) 28.87 (±3.51,n=3) 0.30 (±0.03,n=3) 3.26 (±1.40,n=3) DD7 39.90 (n=1) 0.21 (n=1) 0.27 (n=1) 9.91 (n=1) 0.52 (n=1) 0.68 (n=1) 24.84 (n=1) 0.25 (n=1) 2.05 (n=1) L23’ 31.57 (±5.63,n=3) 0.59 (±0.37,n=3) 0.06 (±0.02,n=3) 7.16 (±0.31,n=3) 1.88 (±1.16,n=3) 0.19 (±0.05,n=3) 22.67 (±0.98,n=3) 0.25 (±0.003,n=3) 7.62 (±4.64,n=3) L23 31.75 (±6.36,n=3) 0.12 (±0.02,n=3) 0.08 (±0.02,n=3) 11.99 (±0.62,n=3) 0.37 (±0.05,n=3) 0.27 (±0.07,n=3) 37.77 (±1.94,n=3) 0.38 (±0.02,n=3) 0.97 (±0.08,n=3) Fespeciation 3.Results anddiscussion 4.72%(±0.84)inDDsimilarresults inaerosols collected in GranCanaria[Gelado‐Caballeroetal.,2012] FeS 0.49%(±0.18) FeA/FeT 0.97%(±0.50) 0,10 1,00 10,00 100,00 DD1 DD2 DD3 DD4 DD5 DD6 DD7 L23' L23 DifferentFespecies(Fe/FeT%) FeA/FeT Fe‐NaOAc/FeT FeD/FeT Feothers/FeT Fespeciation LogscalegraphicalrepresentationofthevariousFespeciesinthesamples 3.Results anddiscussion FeD 32.15%(±20.45) FeA andFe‐NaOAc one to two orders lower than FeD CollectedinShietal., 2012 Numberof samples Sources FeA/FeT(%) FeD/FeT(%) (FeA+FeD)/Fe TFeT(%) FeA/(FeA+FeD) (%) References Sahara:dust precursors 2 Tibest Mountains, SouthLibya: WesternSahara 0.5(±0.2) 35.3(±3.4) 0.36(±0.04) 4.7(±0.1) 1.4 Shi etal., 2011b Paleolakes:dust precursorsorpotential dustprecursors 4 Bodele Depression, Chad;Chott el Djerid,Tunisia; Wadi alHyatt,Libya; Wadi AshSatti,Libya 1.5(±1.1) 18.8(±10.1) 0.2(±0.11) 1.6(±1.3) 7.4 Bejjing:drydeposition dust 1NotKnown 1.7 22.3 0.24 3.5 7.1 Shietal., 2011a E.Mediterranean:dry depositiondust 1NotKnown 0.9 35.1 0.36 2.81 2.5 Shietal., 2009 W.Mediterranean:wet depositiondust 1 Not Known 2.4 35.6 0.38 3.58 6.3 Canary Island: aerosol 12 Saharanorigin byback trajectory NM NM 0.35 (±0.07) NM NM Lazaroet al.,2008 2Saheloriginby backtrajectory NM NM 0.58 (±0.03) NM NM This study L23(african soil, potential dust precursors) 3WesternSahara 0.37 (±0.05) 37.77 (±1.94) 0.38 (±0.02) 3.17 (±0.01) 0.97(±0.08) L23'(dust precursors) 3WesternSahara 1.88 (±1.16) 22.67 (±0.98) 0.25 (±0.03) 3.17 (±0.01) 7.62(±4.64) DD,GranCanaria 7 SaharaNS/WSC 0.93 (±0.36) 32.70 (±23.18) 0.34 (±0.23) 4.72 (±0.84) 4.08(±3.42) Table.SummaryofresultsofthespeciationofFeinthisstudyandcomparedwithotherscompiledinthereviewofShietal.,2012 (NMisnotmeasured) 3.Results anddiscussion Fluxesforelements(µgm‐2d‐1) Thisstudy Johansenetal.,2000 Samples DD1 DD2 DD3 DD5 DD6 Coarse Fine Averange F‐0.13 0.04 0.04 0.03 0.02 0.27 0.01 0.22 Cl‐29.33 2.73 4.13 5.98 3.92 90.43 2.39 62.21 Br‐<0.01 <0.01 <0.01 0.01 <0.01 0.14 0.004 0.10 NO3 ‐1.27 0.15 0.44 0.24 0.45 9.22 0.52 8.16 SO42‐38.07 11.51 9.73 19.32 11.83 18.72 1.73 23.59 C2O42‐2.58 0.84 0.86 0.31 0.59 0.54 0.05 0.68 Na+17.46 1.85 2.92 3.84 2.21 57.60 1.79 41.99 NH4+2.73 0.05 0.50 0.06 0.06 0.99 0.20 2.27 K+<0.01 <0.01 1.62 0.76 0.53 2.61 0.13 2.36 Mg2+ 4.47 0.59 1.11 1.08 1.05 7.11 0.23 5.21 Ca2+ 77.29 9.92 24.48 9.32 6.27 10.97 0.32 7.84 Ca2+ areinagreement with the African origin ofsamples Dry Deposition Fluxes for major elements from IC Table.DrydepositionFluxesformajorelementsinthisstudyandcomparewithestimatedfluxesfromJohansenetal.,2000 dates. 3.Results anddiscussion 4.Preliminary Conclusions 1. The amounts of aerosol collected by deposition systems are very low. For this reason, “ prepared aerosols ” from soils, to mimics the chemical properties of mineral aerosol, is so important. 2. Sequential extraction process results have demonstrated that the Fe speciation in dry deposition samples is similar to aerosol precursors from African soils collected in the source regions. 3. The solubility of the more labile Fe fractions is on average 0.97% (±0.49) of the total Fe content in the samples. The highly reactive Fe (FeA+FeD) corresponds to a significant fraction of the FeT in the samples, an average of 33.10% (±20.27). This Fe can be readily dissolved at low pH. 4. The high variability in the speciation of Fe in dry deposition samples suggest that atmospheric transport may be an important factor controlling aerosol solubility.