Description/methods for parameters measured:
C parameters performed by Dr. Wei-Jun Cai’s group for:
TA - Open cell Gran titration with semi-automatic AS-ALK2 Apollo Scitech titrator;
pH - glass electrode, NBS buffers;
DIC - infrared CO₂ analyzer (AS-C3, Apollo Scitech).
Use Dickson CRM for calibration. DIC/TA samples were filtered (0.45um) and fixed with 100 ul of saturated mercury bichloride.
Use the methods of Gran (1952) and Huang, et al. (2012).

Fe parameters:
The method of Stookey (1972) is used to determine dissolved Fe(II) and on addition if hydroxylamine Fe total. Fe(III) is determined by difference. Modified and calibrated by many including Lewis et al (2007) and MacDonald et al (2014). Typically, triplicate measurements performed.

Dissolved Mn parameters:
The porphyrin spectrophotometric method of Madison et al (2011) measures dissolved Mn(II), Mn(III) bound to weaker ligands and total Mn. Method includes calibration and intercomparison of totals with other instrumentation (ICP, AA). Detection limit is 0.050 micromolar. Detection limit (DL) is 50 micromolar with a 1 cm path length cell.

Modification of Madison for Mn(III) bound to strong ligands by adding a reducing agent to a separate subsample with the porphyrin to obtain total Mn. Mn(III) bound to strong ligand complexes is determined by difference. Typically, triplicate measurements performed. Detection limit is 3.0 nanomolar.

MnO_x on unfiltered samples:
The leucoberbelein blue method is that of Altmann (1972) and Krumblein and Altmann (1973) in 1 cm cells, but can be modified for longer path length cells.

S parameters:
O₂, H₂S and polysulfides by the voltammetry method of Luther et al (2008).
A flow cell was also used to collect in situ O₂ and H₂S data as well as some additional samples. Analysis by voltammetry (Luther et al, 2008).
Solid and nanoparticulate S₈ (Yücel et al 2010 and Findlay et al 2014).
Typically, triplicate measurements performed.

In situ pump profiler cast refers to profiling with a pump profiler for O₂ and H₂S using solid state gold-amalgam electrodes for voltammetry (Luther et al, 2008; Analytical Instrument Systems DLK-60) along with a temperature and salinity sensor from YSI. Water was pumped aboard to make measurements on discrete samples for Mn and Fe speciation as well.

Methods papers used in this project (full citations in Related Publications section)
Dissolved Mn speciation parameters:
Madison et al. (2011)

Madison et al. (2013)

Oldham et al. (2015)

Oldham et al. (2017)
[[ Here, we modified the method of Madison et al. (2011) for water column samples to achieve a detection limit of 3.0 nM (3 times the standard deviation of a blank) by using a 100-cm liquid waveguide capillary cell and the addition of a heating step as well as a strong reducing agent for Mn Speciation [Mn³⁺ = Mn_T – Mn²⁺]. See Table 1 in this paper for recovery tests. As weak Mn(III)-L complexes could not be measured in our previous work (Oldham et al, 2015; paper above), this method was used throughout this cruise. ]]

MnO_X solids:
Altmann (1972)

Krumbein & Altmann (1973)

Dissolved Fe speciation parameters:
Stookey (1970)

Lewis et al. (2007)

O₂ and H₂S, polysulfides:
Luther et al. (2008)

Luther et al. (2013)

S₈:
Yücel et al. (2010)

pH and inorganic carbon parameters:
Gran (1952)

Huang & Cai (2012)