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Croot, Peter L; Heller, Maija I; Wuttig, Kathrin (2019): Redox speciation from water samples during METEOR cruise M77/1. PANGAEA, https://doi.org/10.1594/PANGAEA.907432, Supplement to: Croot, PL et al. (2019): Redox Processes Impacting the Flux of Iron(II) from Shelf Sediments to the OMZ along the Peruvian Shelf. ACS Earth and Space Chemistry, 3(4), 537-549, https://doi.org/10.1021/acsearthspacechem.8b00203

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Abstract:
Iron (Fe) is a limiting nutrient in many regions of the open ocean and can also play a key role in controlling primary productivity in Eastern Boundary Upwelling Systems (EBUS). In EBUS regions, where intense oxygen minimum zones (OMZs) contact the continental shelf, significant iron inputs can result from the supply of Fe(II) from reducing sediments. How much of this iron makes it to the photic zone depends on physical processes mixing over different time scales (minutes to decades) and the kinetics of redox and complexation processes impacting the biogeochemical cycling of iron. In this work we examine the controls on Fe(II) release from shelf sediments across the Peruvian OMZ by measuring Fe(II) and hydrogen peroxide (H2O2) in the water column and benthic boundary layer (BBL) and applying a simple 1D mixing model, with either 1 or 2 layers, where the flux of Fe(II) to the water column is treated as analogous to radon, that the decay rate is constant within the mixing layer. Our modeling approach then allows us to compare our estimated decay rate against published oxidation rates for specific oxidants of Fe(II) in OMZ waters and check the validity of our approach. Our data indicate that throughout the OMZ, Fe(II) decay rates may be partially influenced by H2O2, but it is most likely that nitrate-dependent anaerobic Fe(II) oxidizing (NDFO) bacteria are the main oxidizers. In the secondary nitrite maxima (SNM), abiotic NO2– or biotic-mediated processes may also be important. This work highlights the importance and uses of redox species in understanding biogeochemical cycles in the ocean.
Coverage:
Median Latitude: -11.843933 * Median Longitude: -77.622420 * South-bound Latitude: -17.783333 * West-bound Longitude: -78.886667 * North-bound Latitude: -10.265000 * East-bound Longitude: -71.853300
Date/Time Start: 2008-10-28T19:26:00 * Date/Time End: 2008-11-19T20:59:00
Minimum DEPTH, water: m * Maximum DEPTH, water: 2059 m
Event(s):
M77/1-CTD/RO15 (M77/1_436) * Latitude: -11.000500 * Longitude: -77.791333 * Date/Time: 2008-11-02T15:41:00 * Elevation: -85.9 m * Campaign: M77/1 * Basis: Meteor (1986) * Method/Device: CTD/Rosette (CTD-RO)
M77/1-CTD/RO16 (M77/1_438) * Latitude: -11.011467 * Longitude: -78.583750 * Date/Time: 2008-11-03T00:59:00 * Elevation: -1261.0 m * Campaign: M77/1 * Basis: Meteor (1986) * Method/Device: CTD/Rosette (CTD-RO)
M77/1-CTD/RO22 (M77/1_463) * Latitude: -11.000133 * Longitude: -78.747733 * Date/Time: 2008-11-04T22:24:00 * Campaign: M77/1 * Basis: Meteor (1986) * Method/Device: CTD/Rosette (CTD-RO)
Comment:
#Subsurface seawater samples were collected using Niskin Bottles on the CTD.
#All samples were run shipboard: Fe(II) and H2O2 simultaneously
#All work was performed under clean air conditions in a Class 5 (Old Class 100) laminar flow hood.
#CTD data (included here) from bottle files
#Quality Flag: WOCE Bottle Samples
# NaN denotes missing sample; 0.000 denotes below detection limit (varies by element)
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Event labelEventCroot, Peter L
2Date/Time of eventDate/TimeCroot, Peter L
3LATITUDELatitudeCroot, Peter LGeocode
4LONGITUDELongitudeCroot, Peter LGeocode
5DEPTH, waterDepth watermCroot, Peter LGeocode
6Bottle numberBottleCroot, Peter L
7Height above sea floor/altitudeHeightmCroot, Peter L
8Pressure, waterPressdbarCroot, Peter L
9Temperature, waterTemp°CCroot, Peter LTemp1
10Temperature, waterTemp°CCroot, Peter LTemp2
11SalinitySalCroot, Peter LSal1
12SalinitySalCroot, Peter LSal2
13OxygenO2µmol/lCroot, Peter LOxy1
14OxygenO2µmol/lCroot, Peter LOxy2
15Iron II, ferrous ironFe(II)nmol/lCroot, Peter L
16FlagFlagCroot, Peter LFe II
17Hydrogen peroxide, waterH2O2nmol/lCroot, Peter L
18FlagFlagCroot, Peter LH2O2
19IodideI-nmol/lCroot, Peter L
20FlagFlagCroot, Peter LI-
Size:
3825 data points

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