Evidence of DMS and other biogenic gases affecting iron bioavailability in remote marine aerosols

Anne M. Johansen, Lindsey M. Shank, Mari N. Sorey, Matthew J. Lenington, Zhen Zhang, Brittany Best, Department of Chemistry, Central Washington University, 400 East University Way, Ellensburg, WA 98926, johansea@cwu.edu

AbstractIron availability limits open-ocean phytoplankton growth, and because phytoplankton account for half of the Earth’s photosynthesis they are key players in modulating global climate. Atmospherically transported dust particles provide an important source of iron to remote regions, yet, the mechanisms that control iron speciation and thus its bioavailability remain ill-defined. The present study pertains to elucidating processes that occur on atmospheric dust particles before deposition into the ocean. Laboratory experiments have identified a chemical link between iron reductive dissolution of synthesized iron(oxy)hydroxides and methanesulfinic acid (MSIA), an oxidation product of dimethyl sulfide (DMS) emitted by iron-starved phytoplankton. We present evidence for the existence of this mechanism in aerosol particles collected over the equatorial Pacific Ocean. Furthermore, results suggest that biogenically emitted isoprene oxidation products also affect iron speciation. These findings support the hypothesis that phytoplankton can actively affect iron availability through a direct biogeochemical feedback cycle.

Introduction and MotivationIron (Fe) is an essential micronutrient necessary for the metabolic processes (e.g., photosynthesis and cellular respiration) of marine phytoplankton. In open-ocean environments, far from continental shelves and upwelling currents, iron availability is limited to the atmospheric deposition of crustal-derived aerosols that have been transported to sea by prevailing winds [Gao et al., 2003; Talbot et al., 1990; Tegen et al., 2004]. It has been suggested that iron present on these particles undergoes chemical processing during long-range transport, which ultimately leads to an increase in the more soluble Fe(II), which is also thought to be the more bioavailable fraction. Laboratory simulation results reveal significant Fe(II) and MSA increases from a ligand to metal charge transfer (LMCT) between MSIA and Fe(III) on the surface of ferrihydrite (Figures 1-3). MSIA, an oxidation product of biogenically emitted DMS, has an effect at concentrations that correspond to atmospheric levels lower than 0.12 pmol m-3, four orders of magnitude less than typical concentrations of its precursor DMSO [Lee et al., 1999] and three orders of magnitude lower than observed concentrations of its oxidation product MSA [Johansen et al., 2000]. For ferrihydrite, the proposed reaction is prevalent at pH values < 4.2, which coincide with model predictions for aerosol pH in the remote marine boundary layer [Fridlind and Jacobson, 2000]. Since DMS is released from phytoplankton when under oxidative stress, such as caused by iron limitation or increased UV radiation [Sunda et al., 2002; Toole and Siegel, 2004], the proposed mechanism suggests a mechanism by which phytoplankton can actively affect iron availability through a direct biogeochemical feedback cycle [Zhang et al., 2006; Zhuang et al., 2003]. The mechanism identified here will help explain current discrepancies in marine atmospheric iron and sulfur models, where sources of Fe(II) and MSA have remained unidentified, respectively [Hand et al., 2004; Lucas and Prinn, 2002; Luo et al., 2005; von Glasow and Crutzen, 2004].

[Johansen and Key, 2006; Key et al., 2008]

Summary and Conclusions

ReferencesBerresheim, H., J.W. Huey, R.P. Thorn, F.L. Eisele, D.J. Tanner, and A. Jefferson, Measurements of dimethyl sulfide, dimethyl sulfoxide, dimethyl sulfone, and aerosol ions at Palmer Station, Antarctica, J. Geophys. Res., 103, 1629-1637, 1998.Boyd, P.W., A.J. Watson, C.S. Law, E.R. Abraham, T. Trull, R. Murdoch, D.C.E. Bakker, A.R. Bowie, and e. al., A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization, Nature, 407, 695-702, 2000.Charlson, R.J., J.E. Lovelock, M.O. Andreae, and S.G. Warren, Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate, Nature, 326, 655-661, 1987.Davis, D., G. Chen, P. Kasibhatla, A. Jefferson, D. Tanner, F. Eisele, D. Lenschow, W. Neff, and H. Berresheim, DMS oxidation in the Antarctic marine boundary layer: Comparison of model simulations and field observations of DMS, DMSO, DMSO2, H2SO4(g), MSA(g), and MSA(p), J. Geophys. Res., 103, 1657-1678, 1998.Draxler, R.R. (2002), HYPLIT-4 user’s guide, NOAA Tech Memo, ERL ARL-230, 35pp.Duce, R.A., and N.W. Tindale, Atmospheric transport of iron and its deposition in the ocean, Limnology and Oceanography, 36 (8), 1715-1726, 1991.Johansen, A.M., and M.R. Hoffmann, Chemical characterization of ambient aerosol collected during the northeast monsoon season over the Arabian Sea: Anions and cations, J. Geophys. Res., 109 (D5), 2004.Johansen, A.M., R.L. Siefert, and M.R. Hoffmann, Chemical characterization of ambient aerosol collected during the southwest-monsoon and inter-monsoon seasons over the Arabian Sea: Anions and cations, J. Geophys. Res., 104, 26325-26347, 1999.Johansen, A.M., R.L. Siefert, and M.R. Hoffmann, Chemical composition of aerosols collected over the tropical North Atlantic Ocean, J. Geophys. Res., 105, 15277-15312, 2000.Johansen, A.M.; Key, J.M. Photoductive dissolution of ferrihydrite by methanesulfinic acid: Evidence of a direct link between dimethylsulfide and iron-bioavailability. Geophys. Res. Lett. 2006, 33.Jourdain, B., and M. Legrand, Seasonal variations of atmospheric dimethylsulfide, dimethylsulfoxide, sulfur dioxide, methanesulfonate, and non-sea-salt sulfate aerosols at Dumont d'Urville (coastal Antarctica) (December 1998 to July 1999), J. Geophys. Res., 106 (D13), 14391-14408, 2001.Key, J.M., Paulk, N., and A.M. Johansen, Photochemistry of Iron in Simulated Crustal Aerosols with Dimethyl Sulfide Oxidation Products, 42 (1), 133-139, 2008.Lee, P.A., S.J. de Mora, and M. Levasseur, A Review of Dimethylsulfoxide in Aquatic Environments, Atmosphere-Ocean, 37 (4), 439-456, 1999.Legrand, M., C. Feniet-Saigne, E.S. Saltzman, and C. Germain, Spatial and temporal variations of methanesulfonic acid and non sea salt sulfate in Antarctic ice, J. Atmos. Chem., 14, 245-260, 1992.Nowak, J.B., D.D. Davis, G. Chen, F.L. Eisele, R.L. Mauldin III, D.J. Tanner, C. Cantrell, E. Kosiciuch, A. Bandy, D. Thornton, and A.D. Clarke, Airborne Observations of DMSO, DMS, and OH at Marine Tropical Latitudes, Geophys. Res. Lett., 28 (11), 2201-2204, 2001.Patroescu, I.V., I. Barnes, K.H. Becker, and N. Mihalopoulos, FT-IR product study of the OH-initiated oxidation of DMS in the presence of NOx, Atmos. Environ., 33, 25-35, 1999.Pehkonen, S.O., R. Siefert, Y. Erel, S. Webb, and M. Hoffmann, Photoreduction of iron oxyhydroxides in the presence of important atmospheric organic compounds, Environ. Sci. Technol., 27 (10), 2056-2062, 1993.Sciare, J., E.D. Baboukas, M. Kanakidou, U. Krischke, S. Belviso, H. Bardouki, and N. Mihalopoulos, Spatial and temporal variability of atmospheric sulfur containing gases and particles during the Albatross campaign, J. Geophys. Res., 105 (D11), 14,433-14,448, 2000.Sunda, W., D.J. Kieber, R.P. Kiene, and S. Hunstman, An antioxidant function for DMSP and DMS in marine algae, Nature, 418, 317-320, 2002.Turner, S.M., P.D. Nightingale, L.J. Spokes, M.I. Liddicoat, and P.S. Liss, Increased dimethyl sulphide concentrations in sea water from in situ iron enrichment, Nature, 383, 513-517, 1996.Turnipseed, A.A., S.B. Barone, and A.R. Ravishankara, Reaction of OH with Dimethyl Sulfide. 2. Products and Mechanism, J. Phys. Chem., 100, 14703-14713, 1996.von Glasow, R., and R. Sander, Variation of sea salt aerosol pH with relative humidity, Geophys. Res. Letters, 28 (2), 247-250, 2001.Zhuang, G., Z. Yi, R.A. Duce, and P.R. Brown, Link between iron and sulphur cycles suggested by detection of Fe(II) in remote marine aerosols, Nature, 355, 537-539, 1992.

MethodsSample Collection

High volume cascade impactor (ChemVol 2000, R&P), 760 L/min, four size fractions: ultrafine (da≤0.1 μm), fine (0.1≤da<1 μm),

coarse (1≤da<10 μm) and large (da≥10μm). Sample pretreatment, handling and storage were performed following strict trace

metal clean procedures. Samples were stored at -20 oC until analysis was feasible.Analysis of 152 high-vol samples(i) Ion Chromatography (IC): acetate, MSIA, formate, MSA, pyruvate, Cl-, NO2

-, Br-, NO3-, malonate, SO4

2-, oxalate, and PO43-. Na+,

NH4+, K+, Mg2+, and Ca2+;

(ii) Long pathlength absorbance spectroscopy with a long waveguide capillary cell (LWCC, WPI, 200 cm) and portable spectrometer (TIDAS): labile iron species = Fe(II)(aq) and easily reducible Fe(III) (with hydroxylamine); and

(iii) Inductively Coupled Plasma Mass Spectrometry (ICPMS): 37 trace metals.(iv)Principle Component Analysis (PCA) was performed using SPSS v.15.0 and data was evaluated in the context of air mass back

trajectories (7.5 day AMBT, NOAA HYSPLIT model [Draxler, 2002] with GDAS database).

High volume cascade impactor

R/V Kilo Moana

Results Geographic area designation based on aerosol chemical characteristics

Labile Iron

Figure 4: The cruise track broken into three distinct regions based on characteristic air mass back trajectories (AMBTs), created using NOAA’s GDAS database using the HYSPLIT model.

2

1

3

Figure 5: Representative Air Mass Back Trajectories.

1 2

2 3

0

5

10

15

20

25

30

35

[Fe(

II)]

(M

)

1300

500750

250150

100

50

25100

1300, dark

a[MSIA]i,total (M)

0

200

400

600

800

1000

1200

1400

0 20 40 60 80 100 120 140 160

[Sul

fur

Sp

eci

es]

(M

)

Time (min)

legend same as in asolid symbols MSIAopen symbols MSA

b

pH 5.1-4.7

pH 4.8-4.5

pH 4.7-4.3

pH 4.4-4.2

pH 4.2-4.1

0

5

10

15

20

25

30

35

0 20 40 60 80

[Sul

fur

Sp

eci

es]

(M

)

Time (min)

pH 4.0-4.0

pH 4.1-4.1

pH 4.1-4.2

Figure 1: Proposed Reaction mechanism between MSIA and Fe(III)

Figure 2: Photochemical experiments with one batch of ferrihyrdrite synthesized from Fe(ClO4)3•6H2O in the presence of DMSO, DMSO2, MSIA, and MSA. a. Fe(II), b. Sulfur Species; MSIA (solid symbols) and MSA (corresponding open symbols), and c. H2O2. Initial and final pH values are noted near the end of each curve.

0

25

50

75

100

125

150

0 50 100 150 200 250 300 350

[H2O

2] (

M)

Time (min)

clegend same as in a

0

300

600

900

12001300 M MSIA, MSIA1300 M MSIA, MSA620M MSA, MSA1300 M MSIA + 35 mM DMSO, MSIA1300 M MSIA + 35 mM DMSO, MSA

[Sul

fur

Spe

cies

] (M

)

b

0

25

50

75

1300 M MSIA620 M MSA7400 M DMSO

235 mM DMSO1300 M MSIA+35 mM DMSOno sulfurdark average with sulfur

[Fe(

II)]

(M

)

a

pH 5.4-5.2

pH 3.4-3.8

pH 4.7-4.2

pH 4.8-4.3

pH 4.2-4.0

pH 4.1-4.1

pH 5.4-4.8

Reaction order with regard to adsorbed MSIA, a ≈ 1.Reaction constant, k = 1.4 x 10-4 s-1

Figure 3: Photochemical experiments with one batch of ferrihyrdrite in the presence of varying amounts of MSIA.

AcknowledgementsThis research was supported by National Science Foundation Grant ATM-0137891 and Central Washington University. People: Dr. Jim Murray, CWU Atmospheric Chemistry Group

Organic Acids

Sulfur Containing Compounds

Region% Fe

Solubility% Fe(II)

in Total Fe

% Fe(II)

in Fe Soluble

1

(N/S American)4.9

(0.7 -65.9)

1.2

(0.1 - 9.9)

21

(0 - 86)

2

(Pristine)3.0

(0.7 – 20.0)

3.0

(0.7 - 16.4)

89

(72 - 100)

3

(Bismarck Sea)3.0

(0.2 - 47.3)

2.5

(0.9 - 13.1)

53

(0 - 100)

0

0.2

0.4

0.6

0.8

1

1.2 coarse Fe(II)FZ

coarse Fe(III)hydrox

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

Fe

(II)

(ng

m-3)

Sample ID

0

5

10

15

20

25

30

Fe coarse (ICPMS)

coarse Fetotal (IC

PM

S) (ng m

-3)

0

0.5

1

1.5

2

2.5

3

3.5

4 fine Fe(II)FZ

fine Fe(III) hydrox

Fe

(II)

(ng

m-3

)

0

5

10

15

20

25

Fe fine (ICPMS)

fine Fe

total (ICP

MS

) (ng m-3)

0

0.2

0.4

0.6

0.8

1

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

Fe(II)

Fe(III)hydrox

Fe(

II)

(ng

m-3

)

Sample ID

0

10

20

30

40

50

60

70

large Fe (ICPMS)

large Fe

total (ICP

MS) (ng m

-3)

Table of Geometric Means excluding samples with mixed characteristics in adjacent regions.

  Equatorial Pacific Ocean Region, Large Aerosol Fraction  

 Parameters\Components

1 Marine-

ss

2 Biomass?

3 Crustal

4 Crustal

5 Anthrop

 

  % variance 39.3 18.2 14.2 8.8 6.8  

  Na, large 0.897 0.233 0.265 -0.202 -0.039  

  Mg, large 0.915 0.196 0.254 -0.155 -0.030  

  K, large 0.568 0.759 -0.153 -0.093 0.087  

  Ca, large 0.445 0.196 0.851 -0.007 0.041  

  V, large -0.367 0.759 0.692 0.080 0.023  

  Cr, large 0.033 0.194 0.099 0.883 0.118  

  Fe, large 0.389 -0.132 -0.145 0.833 0.108  

  Ni, large 0.072 -0.515 0.289 0.696 0.149  

  Cu, large 0.093 -0.209 0.204 0.320 0.857  

  Sr, large 0.829 0.090 0.504 -0.076 -0.048  

  Pb, large 0.152 -0.157 -0.241 0.322 0.830  

  Cl-, large 0.919 0.186 -0.120 0.297 0.003  

  Malonate, large 0.017 0.744 -0.132 0.204 -0.406  

  Na+, large 0.925 0.180 -0.110 0.267 0.016  

  NH4+, large 0.367 0.761 0.048 0.068 -0.133  

  Mg2+, large 0.909 0.155 -0.105 0.330 0.016  

  nssCa2+, large -0.688 -0.139 0.602 -0.277 0.007  

  nssK+, large 0.403 0.837 -0.148 -0.184 0.098  

  FeII, large 0.067 -0.269 0.879 0.151 -0.033  

  FeIIIhydrox, large -0.404 0.257 0.014 -0.300 0.766  

               

• Fine ferrous iron predominates in the pristine equatorial Pacific Ocean• This ferrous iron correlates with

• MSA and malonate, (PC 3) and• Oxalate (PC 5).

• These findings indicate that iron solubility in pristine areas is controlled by oxidation products of biogenically emitted gases thereby further supporting the hypothesis that phytoplankton and aerosol iron solubility are involved in a biogeochemical control cycle.

0

20

40

60

80

100

120

140

160

0

0.5

1

1.5

2

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

largecoarsefineultrafine

Oxa

late

(ng

m-3

)

Sample ID

Oxalate (nm

ols m-3)

0

100

200

300

400

500

600

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

Malonate largeMalonate coarseMalonate fineMalonate ultrafine

0

0.8

1.6

2.4

3.2

4

4.8

5.6

Mal

onat

e (n

g m

-3)

Sample ID

Malonate (nm

ols m-3)

0

5

10

15

20

25

30

35

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

largecoarsefineultrafine

MS

A (

ng m

-3)

Sample ID

MS

A (nm

ols m-3)

0

1000

2000

3000

4000

5000

0

10

20

30

40

50

2320

623

306

2340

623

506

2360

623

806

2390

624

306

2440

624

806

2490

625

206

2530

625

906

2610

626

306

2640

626

506

2660

626

706

2680

626

906

2700

627

106

2720

627

306

2780

627

906

2800

628

106

2810

6.02

2820

628

306

2840

628

506

2860

628

706

2880

6

ss-SO4

2- large

nss-SO4

2- large

ss-SO4

2- coarse

nss-SO4

2- coarse

ss-SO4

2- fine

nss-SO4

2- fine

ss-SO4

2- ultrafine

nss-SO4

2- ultrafine

SO

42- (

ng m

-3)

Sample ID

SO

4 2- (nmols m

-3)

  Equatorial Pacific Ocean Region, Fine Aerosol Fraction  

 Parameters\Components

1 Crustal

2 Marine-ss

3 Marine-bio

4 Crustal

5 Marine-bio, Anthrop?  

  % variance 32.2 21.0 17.8 9.7 4.9  

  Na, fine -0.287 0.806 0.099 0.225 -0.246  

  Mg, fine 0.023 0.906 0.023 0.338 -0.039  

  Ca, fine 0.912 -0.159 -0.182 0.242 0.026  

  Sc, fine 0.776 0.351 0.048 0.180 -0.385  

  Ti, fine -0.081 0.205 0.399 0.312 -0.557  

  Cr, fine 0.326 0.040 -0.086 0.881 0.231  

  Fe, fine 0.520 0.249 -0.092 0.633 -0.133  

  Ni, fine 0.050 0.305 -0.069 0.897 0.004  

  Cu, fine 0.470 -0.038 -0.149 0.655 -0.078  

  Se, fine 0.798 -0.111 -0.254 0.467 0.106  

  Pb, fine 0.906 -0.089 0.111 0.046 0.050  

  MSA, fine -0.292 0.328 0.827 -0.139 0.256  

  Cl-, fine -0.133 0.503 0.671 -0.261 0.187  

  NO3-, fine -0.142 0.339 0.844 -0.090 0.145  

  Oxalate, fine -0.050 -0.313 0.223 0.179 0.798  

  Malonate, fine 0.473 -0.337 0.620 -0.137 0.048  

  nssSO42-, fine 0.124 0.168 0.386 0.049 0.829  

  Na+, fine -0.083 0.870 0.333 -0.016 0.204  

  NH4+, fine -0.143 0.265 0.195 0.023 0.856  

  nssCa2+, fine 0.866 -0.320 -0.235 0.228 -0.016  

  FeII, fine -0.096 -0.298 0.678 0.002 0.506  

               

  Equatorial Pacific Ocean Region, Coarse Aerosol Fraction  

 Parameters\Components

1 Marine

2 Marine

3 Crustal

4 Anthrop?

5 Labile Fe  

  % variance 46.2 15.9 12.3 9.9 6.1  

  Na, coarse 0.964 0.166 -0.114 0.071 -0.037  

  Mg, coarse 0.952 0.255 -0.089 0.052 -0.007  

  K, coarse 0.894 0.131 -0.161 0.153 -0.054  

  Ti, coarse 0.927 0.032 0.015 -0.035 0.068  

  Cr, coarse -0.275 0.061 0.934 0.047 -0.014  

  Fe, coarse 0.237 -0.175 0.831 0.255 -0.133  

  Ni, coarse -0.103 0.101 0.860 0.009 -0.014  

  Cu, coarse -0.173 -0.034 0.783 -0.434 -0.039  

  Se, coarse 0.917 0.178 0.088 -0.023 0.013  

  Sr, coarse 0.960 0.213 -0.092 0.041 -0.029  

  Pb, coarse -0.101 -0.141 0.202 -0.842 -0.130  

  MSA, coarse 0.815 0.413 -0.216 0.168 -0.051  

  Cl-, coarse 0.855 0.374 -0.112 0.173 -0.100  

  NO3-, coarse 0.671 0.151 0.070 0.650 0.020  

  Oxalate, coarse -0.070 -0.027 0.477 0.737 0.142  

  nssSO42-, coarse 0.263 -0.790 -0.049 0.370 -0.160  

  Na+, coarse 0.427 0.892 0.025 0.107 -0.017  

  K+, coarse 0.452 0.854 -0.051 0.172 -0.047  

  Mg2+, coarse 0.436 0.883 0.008 0.129 -0.040  

  Ca2+, coarse 0.439 0.876 0.011 0.156 -0.023  

  FeII, coarse -0.041 -0.194 -0.350 0.164 0.823  

  FeIIIhydrox, coarse -0.010 0.154 0.115 0.076 0.941  

               

Principal Component Analysis Output for Equatorial Pacific

Ocean Samples

1Regions 2 3 1

OH•

NO3•

Feedbackcycles

Fe2O3 (s)

FeO(OH) (s)Fe(OH)3 (s)

DMS (aq)

DMS (g)

DMSP (aq)

DMSO (g)

MSIA (g)MSA (g)

SO2 (g)

SO42-

CCN

Fe(III)(aq) + Fe(II)(aq)

PhytoplanktonISOPRENE (aq)

ISOPRENE (g)

HOCCH2OR (g)

HCOCHO (g)

H3CCOCHO (g)

Relevant aqueous phase reactions:CH3COCH0aq +2 HO˙ → (COO)2

2-aq

(COO)22-

aq + Fe(III)aq → Fe(II)aq+ CO2

MSIA + Fe(III)aq→ MSA(aq) + Fe(II)aq

(Barone et al., 1996; Boyd et al., 2000; Charlson et al., 1987; Davis et al., 1998; Patroescu et al., 1999; Sunda et al., 2002; Turner et al., 1996; Turnipseed et al., 1996; Zhuang et al., 1992)