Welcome to RR2307 GOA Transit’s documentation! ********************************************** CTDO and Hydrographic Analysis ============================== Technicians * Todd Martz * Ben Freiberger Post-Cruise Data Analysts * Allen Smith * Aaron Mau CTDO and Bottle Data Acquisition -------------------------------- A total of 5 stations (1 - 5) were occupied on RR2307. The CTD data acquisition system consisted of an SBE-11+ (V1) deck unit and a networked generic PC workstation running Windows 10. SBE SeaSave7 v.7.26.7.121 software was used for data acquisition and to close bottles on the rosette. +------------------+------------------+------------------+------------------+------------------+------------------+ | Equipment | Model | S/N | Cal Date | Stations | Group | |==================|==================|==================|==================|==================|==================| | CTD | SBE9+ | 0569 | | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ | Pressure Sensor | Digiquartz | | 07-Dec-2021 | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ | Primary | SBE3+ | 4907 | 14-Mar-2023 | 1-5 | STS/ODF | | Temperature | | | | | | +------------------+------------------+------------------+------------------+------------------+------------------+ | Primary | SBE4C | 4651 | 20-Jan-2023 | 1-5 | STS/ODF | | Conductivity | | | | | | +------------------+------------------+------------------+------------------+------------------+------------------+ | Secondary | SBE3+ | 4588 | 25-Oct-2022 | 1-5 | STS/ODF | | Temperature | | | | | | +------------------+------------------+------------------+------------------+------------------+------------------+ | Secondary | SBE4C | 4650 | 13-Dec-2022 | 1-5 | STS/ODF | | Conductivity | | | | | | +------------------+------------------+------------------+------------------+------------------+------------------+ | Transmissometer | Cstar | 0479DR | 02-Aug-2023 | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ | Fluorometer | WetLabs ECO-FL- | 4334 | 07-Jan-2022 | 1-5 | ODF | | Chlorophyll | RTD | | | | | +------------------+------------------+------------------+------------------+------------------+------------------+ | Dissolved Oxygen | SBE43 | 1508 | 07-Oct-2022 | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ | Altimeter | Valeport VA500 | 53821 | 28-Jan-2016 | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ | PAR | QCP2300 | 70444 | 06-Feb-2019 | 1-5 | STS/ODF | +------------------+------------------+------------------+------------------+------------------+------------------+ The transmissometer used on the CTD was tested with a light-dark test to acquire coefficients prior to the first station. +-----------------------------------+-----------------------------------+-----------------------------------+ | Transmissomter | M | B | |===================================|===================================|===================================| | 1814DR | 21.1461 | -1.2265 | +-----------------------------------+-----------------------------------+-----------------------------------+ CTDO Data Processing -------------------- Shipboard CTD data processing was performed after deployment using SIO/ODF CTD processing software “ctdcal” v. 0.1.4b. CTD acquisition data were copied onto a OS X system, and then processed. CTD data at bottle trips were extracted, and a 2-decibar downcast pressure series created. The pressure series data set was submitted for CTD data distribution after corrections outlined in the following sections were applied. CTDO/Bottle data were processed following the cruise by ODF, including discrete salinity, oxygen, and nutrient analyses. Discrete salinity and oxygen data were used for fitting of CTD conductivity and oxygen sensors. Pressure Analysis ----------------- The lab calibration coefficients provided on the calibration report were used to convert frequencies to pressure. Initial SIO pressure lab calibration slope and offsets coefficients were applied to cast data. A shipboard calibration offset was applied to the converted pressures during each cast. These offsets were determined by the pre and post- cast on-deck pressure offsets. ODF CTD #0569: +-----------------------------------+-----------------------------------+-----------------------------------+ | | Start P (dbar) | End P (dbar) | |===================================|===================================|===================================| | Min | 0.36 | 0.06 | +-----------------------------------+-----------------------------------+-----------------------------------+ | Max | 0.65 | 0.27 | +-----------------------------------+-----------------------------------+-----------------------------------+ | Average | 0.51 | 0.19 | +-----------------------------------+-----------------------------------+-----------------------------------+ On-deck pressure reading varied from 0.36 to 0.65 dbar before the casts, and 0.06 to 0.27 dbar after the casts. The pressure offset varied from -0.45 to -0.12, with a mean value of -0.33 dbar. Temperature Analysis -------------------- Laboratory calibrations of temperature sensors were performed prior to the cruise at the SIO Calibration Facility. Dates of laboratory calibration are recorded on the underway sampling package table and calibration documents are provided in the appendices. The pre-cruise laboratory calibration coefficients were used to convert SBE3plus frequencies to ITS-90 temperature. Additional shipboard calibrations were performed to correct systematic sensor bias. At each bottle closure, the primary and secondary temperature were compared with each other. [image]T1-T2 versus station. [image]Deep T1-T2 versus station (Pressure \geq 2000dbar). [image]T1-T2 versus pressure. The 95% confidence limits for the mean low-gradient (values -0.002 °C \leq T1-T2 \leq 0.002 °C) differences are ±0.00143 °C for T1-T2. The 95% confidence limits for the deep temperature residuals (where pressure \geq 2000 dbar) are ±0.00083 °C for for T1-T2. Sensor quality was consistent across the casts and no sensor substitutions were required. Conductivity Analysis --------------------- Laboratory calibrations of conductivity sensors were performed prior to the cruise at the Sea-Bird Calibration Facility. Dates of laboratory calibration are recorded on the underway sampling package table and calibration documents are provided in the appendices. The pre-cruise laboratory calibration coefficients were used to convert SBE4C frequencies to mS/cm conductivity values. Additional shipboard calibrations were performed to correct sensor bias. Corrections for both pressure and temperature sensors were finalized before analyzing conductivity differences. Two independent metrics of calibration accuracy were examined. At each bottle closure, the primary and secondary conductivity were compared with each other. Each sensor was also compared to conductivity calculated from check sample salinities (Autosalinometer samples) using CTD pressure and temperature. The differences between primary and secondary temperature sensors were used as filtering criteria to reduce the contamination of conductivity comparisons by package wake. The coherence of this relationship is shown in the following figures. [image]Coherence of conductivity differences as a function of temperature differences. [image]Corrected C_Bottle - C1 versus station. [image]Deep Corrected C_Bottle - C1 versus station (Pressure >= 2000dbar). [image]Corrected C_Bottle - C2 versus station. [image]Deep Corrected C_Bottle - C2 versus station (Pressure >= 2000dbar). [image]Corrected C1-C2 versus station. [image]Deep Corrected C1-C2 versus station (Pressure >= 2000dbar). [image]Corrected C_Bottle - C1 versus pressure. [image]Corrected C_Bottle - C2 versus pressure. [image]Corrected C1-C2 versus pressure. A functioning SBE4C sensor typically exhibit a predictable modeled response. Offsets for each C sensor were determined using C_Bottle - C_CTD differences in a deeper pressure range (500 or more dbars). After conductivity offsets were applied to all casts, response to pressure, temperature and conductivity were examined for each conductivity sensor. The response model is second-order with respect to pressure, second-order with respect to temperature, and second- order with respect to conductivity: C_{cor} = C + cp_2 P^2 + cp_1 P + ct_2 T^2 + ct_1 T + cc_2 C^2 + cc_1 C + \text{Offset} Fit coefficients for the ODF rosette are shown in the following tables. ODF Primary conductivity (C1) coefficients. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | Station | cp_2 | cp_1 | ct_2 | ct_1 | cc_2 | cc_1 | c_0 | |==============|==============|==============|==============|==============|==============|==============|==============| | 1-5 | 0.e+0 | -5.9137e-7 | 0.e+0 | 0.e+0 | 0.e+0 | 0.e+0 | 4.626e-3 | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ ODF Secondary conductivity (C2) coefficients. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | Station | cp_2 | cp_1 | ct_2 | ct_1 | cc_2 | cc_1 | c_0 | |==============|==============|==============|==============|==============|==============|==============|==============| | 1-5 | 0.e+0 | 7.2722e-7 | 0.e+0 | 0.e+0 | 0.e+0 | 0.e+0 | 1.2113e-3 | +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ Salinity residuals after applying shipboard P/T/C corrections are summarized in the figures of this section. Only CTD and bottle salinity data with “acceptable” quality codes are included in the differences. [image]Salinity residuals versus station. [image]Deep Salinity residuals versus station (Pressure >= 2000dbar). [image]Salinity residuals versus pressure. The 95% confidence limits for the mean low-gradient (values -0.002 ºC \leq T1-T2 \leq 0.002 ºC) differences are ±0.00471 mPSU for salinity- C1SAL, ±0.00459 mPSU for salinity-C2SAL and ±0.00308 mPSU for C1SAL- C2SAL. The 95% confidence limits for the deep salinity residuals (where pressure \geq 2000 dbar) are ±0.00147 mPSU for salinity-C1SAL, ±0.00147 mPSU for salinity-C2SAL and ±0.00033 mPSU for C1SAL-C2SAL. No issues affected conductivity and calculated CTD salinities during this cruise. CTD Dissolved Oxygen -------------------- Laboratory calibrations of the dissolved oxygen sensors were performed prior to the cruise at the SBE calibration facility. Dates of laboratory calibration are recorded on the underway sampling package table and calibration documents are provided in the appendices. The pre-cruise laboratory calibration coefficients were used to convert SBE43 frequencies to µmol/kg oxygen values for acquisition only. Additional shipboard fitting were performed to correct for the sensors non-linear response. Corrections for pressure, temperature, and conductivity sensors were finalized before analyzing dissolved oxygen data. Corrections for hysteresis are applied following Sea-Bird Application Note 64-3. The SBE43 sensor data were compared to dissolved O_2 check samples taken at bottle stops by matching the downcast CTD data to the upcast trip locations along isopycnal surfaces. CTD dissolved O_2 was then calculated using Clark Cell MPOD O_2 sensor response model for Beckman/SensorMedics and SBE43 dissolved O_2 sensors. The residual differences of bottle check value versus CTD dissolved O_2 values are minimized by optimizing the NOAA-PMEL DO sensor response model coefficients using the BFGS non-linear least- squares fitting procedure. The general form of the PMEL DO sensor response model equation for Clark cells follows Brown and Morrison [Mill82] and Owens [Owen85]. Dissolved O_2 concentration is then calculated: O_2 = S_{oc} \cdot (V + V_{\textrm{off}} + \tau_{20} \cdot e^{(D_1 \cdot p + D_2 \cdot (T - 20))} \cdot dV/dt) \cdot O_{sat} \cdot e^{T_{cor} \cdot T} \cdot e^{[(E \cdot p) / (273.15 + T)]} Where: * V is oxygen voltage (V) * D_1 and D_2 are (fixed) SBE calibration coefficients * T is corrected CTD temperature (°C) * p is corrected CTD pressure (dbar) * dV/dt is the time-derivative of voltage (V/s) * O_sat is oxygen saturation * S_oc, V_off, \tau_20, T_cor, and E are fit coefficients All stations were fit against post-cruise Winkler titrations together to get an initial coefficient estimate. Stations were then fit individually to refine the coefficients as the membrane does not deform the same way with each cast. If the fit of the individual cast had worse resdiuals than the group, they were reverted to the original group fit coefficients. ODF SBE43 group fit coefficients. Coefficients were further refined station-by-station. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +------------------+------------------+------------------+------------------+------------------+------------------+ | Station | S _oc | V _off | tau _20 | T _cor | E | |==================|==================|==================|==================|==================|==================| | 1-5 group | 5.8609e-1 | -5.2011e-1 | 9.4008e-1 | -3.6850e-4 | 4.0942e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ | 00101 | 5.2154e-1 | -4.9243e-1 | 9.4088e-1 | 2.339e-3 | 4.9013e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ | 00202 | 6.1597e-1 | -5.2899e-1 | 9.4079e-1 | -1.8902e-3 | 3.4814e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ | 00301 | 5.1095e-1 | -4.9235e-1 | 9.4013e-1 | 3.5923e-3 | 4.9584e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ | 00401 | 5.0694e-1 | -4.8706e-1 | 9.4045e-1 | 3.9501e-3 | 5.0410e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ | 00501 | 5.4219e-1 | -4.8161e-1 | 9.4009e-1 | 2.8786e-3 | 4.4413e-2 | +------------------+------------------+------------------+------------------+------------------+------------------+ CTD dissolved O_2 residuals are shown in the following figures O2 residuals versus station through Deep O2 residuals versus station (Pressure >= 2000dbar).. [image]O_2 residuals versus station [image]Deep O_2 residuals versus station (Pressure >= 2000dbar). [image]O_2 residuals versus pressure The 95% confidence limits of 1.218 (µmol/kg) for all acceptable (flag 2) dissolved oxygen bottle data values and 0.2529 (µmol/kg) for deep dissolved oxygen values are only presented as general indicators of the goodness of fit. CLIVAR GO-SHIP standards for CTD dissolved oxygen data are < 1% accuracy against on board Winkler titrated dissolved O_2 lab measurements. No issues arose with the acquisition and processing of CTD dissolved oxygen data. Post-Cruise Processing ---------------------- All casts from the ODF rosette were inspected and manually flagged using ctdcal. Bottle data were flagged as questionable (WOCE flag 3) in accordance with limits as a function of depth, as well as data which indicated a mistrip or otherwise were not believed to be accurate. Data were then reprocessed with updated flags to assess any changes to fitting residuals. Residual flagging limits. ^^^^^^^^^^^^^^^^^^^^^^^^^ +----------------------------------------------------+----------------------------------------------------+ | Residual tolerance | Depth (m) | |====================================================|====================================================| | 0.020 | 0-500 | +----------------------------------------------------+----------------------------------------------------+ | 0.010 | 500-1000 | +----------------------------------------------------+----------------------------------------------------+ | 0.005 | 1000-2000 | +----------------------------------------------------+----------------------------------------------------+ | 0.002 | 2000-6000 | +----------------------------------------------------+----------------------------------------------------+ Other discrete data, such as nutrients, were merged into the dataset for submission to the CCHDO. [Mill82] Millard, R. C., Jr., “CTD calibration and data processing techniques at WHOI using the practical salinity scale,” Proc. Int. STD Conference and Workshop, p. 19, Mar. Tech. Soc., La Jolla, Ca. (1982). [Owen85] Owens, W. B. and Millard, R. C., Jr., “A new algorithm for CTD oxygen calibration,” Journ. of Am. Meteorological Soc., 15, p. 621 (1985). Oxygen Analysis =============== 62 samples from 5 CTD/float stations were collected, fixed, and run during set up for the GO-SHIP I05/RR2308 expedition. Once the samples were fixed they were kept in the dark with a small amount of liquid in the neck of the flasks until analysis was performed. Methods used on I05 are described here. Equipment and Techniques ------------------------ Dissolved oxygen analyses were performed with an SIO/ODF-designed automated oxygen titrator using photometric end-point detection based on the absorption of 365nm wavelength ultra-violet light. The titration of the samples and the data logging were controlled by PC LabView software. Thiosulfate was dispensed by a Dosimat 665 buret driver fitted with a 1.0 ml burette. ODF used a whole-bottle modified-Winkler titration following the technique of Carpenter [Carpenter1965] with modifications by [Culberson1991] but with higher concentrations of potassium iodate standard (~0.012 N), and thiosulfate solution (~55 g/L). Pre-made liquid potassium iodate standards and reagent/distilled water blanks were run every day (approximately every 3-4 stations), with samples analysed within 24 hours of the last standard. Sampling and Data Processing ---------------------------- Niskin samples were collected soon after the rosette was secured on deck. Nominal 125 mL volume-calibrated biological oxygen demand (BOD) flasks were rinsed 3 times with minimal agitation using a silicone draw tube, then filled and allowed to overflow for at least 3 flask volumes, ensuring no bubbles remained. Pickling reagents MnCl2 and NaI/NaOH (1 mL of each) were added via bottle-top dispensers to fix samples before stoppering. Flasks were shaken twice (10-12 inversions) to assure thorough dispersion of the precipitate - once immediately after drawing and then again after 30-60 minutes. Sample draw temperatures, measured with an electronic resistance temperature detector (RTD) embedded in the draw tube, were used to calculate umol/kg concentrations, and as a diagnostic check of bottle integrity. Thiosulfate normalities were calculated for each standardization and corrected to 20°C. The 20°C thiosulfate normalities and blanks were plotted versus time and were reviewed for possible problems and were subsequently determined to be stable enough that no smoothing was required. Volumetric Calibration ---------------------- Oxygen flask volumes were determined gravimetrically with degassed deionised water to determine flask volumes at ODF’s chemistry laboratory. This is done once before using flasks for the first time and periodically thereafter when a suspect volume is detected. The 10 mL Dosimat buret used to dispense standard iodate solution was calibrated using the same method. Standards --------- Liquid potassium iodate standards were prepared in 6 L batches and bottled in sterile glass bottles at ODF’s chemistry laboratory prior to the expedition. The normality of the liquid standard was determined by calculation from weight. The standard was supplied by Alfa Aesar and has a reported purity of 99.4-100.4%. All other reagents were “reagent grade” and were tested for levels of oxidising and reducing impurities prior to use. Narrative --------- The oxygen analytical rig was setup in the main lab of the Revelle. Batches of reagents were prepared as needed during the cruise. No major analytical issues were encountered. A few high end points occurred and were corrected for. Only one sample was lost due to a LabView error. The Dosimat base used to deliver liquid potassium iodate standard malfunctioned after station 11 and was replaced with a spare unit. The analytical computer would freeze occasionally, but never while doing analysis. The thiosulfate stability was considered in 6 batches and showed remarkable stability throughout the entire cruise. No trends were observed or corrected for. No data updates are expected. [Carpenter1965] Carpenter, J. H., “The Chesapeake Bay Institute technique for the Winkler dissolved oxygen method,” Limnology and Oceanography, 10, pp. 141-143 (1965). [Culberson1991] Culberson, C. H., Knapp, G., Stalcup, M., Williams, R. T., and Zemlyak, F., “A comparison of methods for the determination of dissolved oxygen in seawater,” Report WHPO 91-2, WOCE Hydrographic Programme Office (Aug 1991). Discrete Salinity Sampling ========================== Samples from 5 CTD/float stations were collected and sorted for analysis prior to the GO-SHIP I05/RR2308 expedition. Methods used on I05 are described here. Equipment & Techniques ---------------------- Two Guildline Autosals were on board and operational, SIO-owned 8400A S/N 57-526 and 8400A S/N 55-654. S/N 57-526 was used for all salinity measurements during this cruise. The salinity analysis was run in the ship’s Climate Controlled Chamber, a refrigerator, port and amidships between the Computer Lab and Bioanalytical Lab. The chamber temperature varied between about 21 and 24 degrees Celsius around 3 times each hour, with an average (based on measuring temperatures of items in the chamber) of about 22.5°C. IAPSO Standard Seawater Batch P166 was used for all calibrations: K15 = 0.99987, Practical salinity = 34.995, expiration 2025-04-06. A LabView program developed by Carl Mattson was used for monitoring temperatures, logging data, and prompting the operator. Salinity analyses were performed after samples had equilibrated to a laboratory temperature of 23°C, 8 hours or more after collection. Samples were placed under fans to speed their acclimatization to the set room temperature The salinometer was standardized for each group of samples analyzed (up to 3 casts, or up to 108 samples) using two bottles of standard seawater: one at the beginning and one at the end of each set of measurements. For each calibration standard and sample reading, the salinometer cell was initially flushed at least 2 times before a set of conductivity ratio readings was recorded. Standardization conductivity offsets did not exceed 0.00005 mS/cm for all casts. Between runs, the water from the last standard was left in the cell. Sampling & Data Processing -------------------------- The salinity samples were collected in 200 ml Kimax high-alumina borosilicate bottles that had been rinsed at least three times with sample water prior to filling. The bottles were sealed with plastic insert thimbles and Nalgene screw caps. This assembly provides very low container dissolution and sample evaporation. Prior to sample collection, inserts were inspected for proper fit, and loose inserts were replaced to ensure an airtight seal. Laboratory temperature was also monitored electronically throughout the cruise. PSS-78 salinity [UNESCO1981] was calculated for each sample from the measured conductivity ratios. The offset between the initial standard seawater value and its reference value was applied to each sample. Then the difference (if any) between the initial and final vials of standard seawater was applied to each sample as a function of elapsed run time. The corrected salinity data was then incorporated into the cruise database. 6340 salinity samples were collected and run during I05, using approximately 194 bottles of standard seawater. There were 2 crates (62 total samples) of samples run at the beginning of the cruise that had been collected from CTD casts done during the transit from Goa, India to Fremantle, Australia. These were used for training salinity analysts but are not included in the data for RR2308. Problems -------- 10 sample bottles were broken or chipped during this cruise, and all were replaced during sampling. During various points of the cruise, it was noted that some sample bottles had red algae growing in them. To clean the bottles, they were rinsed with acid (10% HCl) and then rinsed with fresh water prior to being added back into the crates for sampling. To help with cell filling, capillary tubes were carefully cleaned with MilliQ, followed by air, once during the cruise, to help with cell filling. Within the first 24 stations, the climate-controlled chamber lost temperature control 3 times due to a bad valve in the condenser line. Engineers from the ship’s crew worked to fix this issue and the room maintained its after their work. Towards the last 3 weeks of the cruise, the air temperature probe connected to LabView began to show some extremely unrealistic values (air temperatures between 500-1200 degrees Celsius). The air temperature probe that is used is old and both the connection prongs and the contacts in the electronics are oxidized. To combat unrealistic readings the prongs were cleaned which worked temporarily but continuous upkeep was unrealistic because of the placement. In tandem with the external temperature probes throughout the chamber, the temperature range between 21 and 24 degrees Celsius was maintained. Nutrients ========= * 62 samples from 5 CTD/float stations were frozen and run during GO- SHIP I05/RR2308. Nutrient samples were drawn into 30 ml polypropylene screw-capped centrifuge tubes. The tubes and caps were rinsed 2-3 times with sample before filling. Samples were frozen in the scientific freezer. Prior to analysis, the samples were thawed in a warm water bath set to 50C for 30 minutes. Once completely thawed samples were shaken to ensure homogeneity and then allowed to come back to room temperature before being analyzed. Methods used on I05 are described here. Equipment and Techniques ------------------------ Nutrient analyses (phosphate, silicate, nitrate+nitrite, and nitrite) were performed on a Seal Analytical continuous-flow AutoAnalyzer 3 (AA3). The methods used are described by Gordon et al [Gordon1992] Hager et al. [Hager1972], and Atlas et al. [Atlas1971]. Details of modification of analytical methods used in this cruise are also compatible with the methods described in the nutrient section of the updated GO-SHIP repeat hydrography manual (Becker et al., 2019, [Becker2019]). Nitrate/Nitrite Analysis ------------------------ A modification of the Armstrong et al. (1967) [Armstrong1967] procedure was used for the analysis of nitrate and nitrite. For nitrate analysis, a seawater sample was passed through a cadmium column where the nitrate was reduced to nitrite. This nitrite was then diazotized with sulfanilamide and coupled with N-(1-naphthyl)-ethylenediamine to form a red dye. The sample was then passed through a 10mm flowcell and absorbance measured at 520nm. The procedure was the same for the nitrite analysis but without the cadmium column. **REAGENTS** Sulfanilamide Dissolve 10g sulfamilamide in 1.2N HCl and bring to 1 liter volume. Add 2 drops of 30% Brij-35 surfactant. Store at room temperature in a dark poly bottle. Note: 30% Brij-35 is 30% Brij-35 dissolved in 100 mL DIW. N-(1-Naphthyl)-ethylenediamine dihydrochloride (N-1-N) Dissolve 1g N-1-N in DIW, bring to 1 liter volume. Add 2 drops 30% Brij-35 surfactant. Store at room temperature in a dark poly bottle. Discard if the solution turns dark reddish brown. Imidazole Buffer Dissolve 13.6g imidazole in ~3.8 liters DIW. Stir for at least 30 minutes to completely dissolve. Add 60 ml of CuSO4 + NH4Cl mix (see below). Add 4 30% Brij-35 surfactant. Let sit overnight before proceeding. Using a calibrated pH meter, adjust to pH of 7.83-7.85 with 10% (1.2N) HCl (about 10 ml of acid, depending on exact strength). Bring final solution to 4L with DIW. Store at room temperature. NH4Cl + CuSO4 mix Dissolve 2g cupric sulfate in DIW, bring to 100 m1 volume (2%). Dissolve 250g ammonium chloride in DIW, bring to 1l liter volume. Add 5ml of 2% CuSO4 solution to this NH4Cl stock. This should last many months. Phosphate Analysis ------------------ Ortho-Phosphate was analyzed using a modification of the Bernhardt and Wilhelms (1967) [Bernhardt1967] method. Acidified ammonium molybdate was added to a seawater sample to produce phosphomolybdic acid, which was then reduced to phosphomolybdous acid (a blue compound) following the addition of dihydrazine sulfate. The sample was passed through a 10mm flowcell and absorbance measured at 820nm. **REAGENTS** Ammonium Molybdate H2SO4 sol’n Pour 420 ml of DIW into a 2 liter Ehrlenmeyer flask or beaker, place this flask or beaker into an ice bath. SLOWLY add 330 ml of conc H2SO4. This solution gets VERY HOT!! Cool in the ice bath. Make up as much as necessary in the above proportions. Dissolve 27g ammonium molybdate in 250ml of DIW. Bring to 1 liter volume with the cooled sulfuric acid sol’n. Add 3 drops of 15% DDS surfactant. Store in a dark poly bottle. Dihydrazine Sulfate Dissolve 6.4g dihydazine sulfate in DIW, bring to 1 liter volume and refrigerate. Silicate Analysis ----------------- Silicate was analyzed using the basic method of Armstrong et al. (1967). Acidified ammonium molybdate was added to a seawater sample to produce silicomolybdic acid which was then reduced to silicomolybdous acid (a blue compound) following the addition of stannous chloride. The sample was passed through a 10mm flowcell and measured at 660nm. **REAGENTS** Tartaric Acid Dissolve 200g tartaric acid in DW and bring to 1 liter volume. Store at room temperature in a poly bottle. Ammonium Molybdate Dissolve 10.8g Ammonium Molybdate Tetrahydrate in 1000ml dilute H2SO4. (Dilute H2SO4 = 2.8ml conc H2SO4 or 6.4ml of H2SO4 diluted for PO4 moly per liter DW) (dissolve powder, then add H2SO4) Add 3-5 drops 15% SDS surfactant per liter of solution. Stannous Chloride stock: (as needed) Dissolve 40g of stannous chloride in 100 ml 5N HCl. Refrigerate in a poly bottle. NOTE: Minimize oxygen introduction by swirling rather than shaking the solution. Discard if a white solution (oxychloride) forms. working: (every 24 hours) Bring 5 ml of stannous chloride stock to 200 ml final volume with 1.2N HCl. Make up daily - refrigerate when not in use in a dark poly bottle. Data Collection and Processing ------------------------------ Data collection and processing was done with the software provided with the instrument from Seal Analytical (AACE). After each run, the charts were reviewed for any problems during the run, any blank was subtracted, and final concentrations (micro moles/liter) were calculated, based on a linear curve fit. Once the run was reviewed and concentrations calculated a text file was created. That text file was reviewed for possible problems and then converted to another text file with only sample identifiers and nutrient concentrations that was merged with other bottle data. Standards and Glassware Calibration ----------------------------------- Primary standards for silicate (Na2SiF6), nitrate (KNO3), nitrite (NaNO2), and phosphate (KH2PO4) were obtained from Johnson Matthey Chemical Co. and/or Fisher Scientific. The supplier reports purities of >98%, 99.999%, 97%, and 99.999 respectively. All glass volumetric flasks and pipettes were gravimetrically calibrated prior to the cruise. The primary standards were dried and weighed out to 0.1mg prior to the cruise. The exact weight was noted for future reference. When primary standards were made, the flask volume at 20C, the weight of the powder, and the temperature of the solution were used to buoyancy-correct the weight, calculate the exact concentration of the solution, and determine how much of the primary was needed for the desired concentrations of secondary standard. The new standards were compared to the old before use. All the reagent solutions, primary and secondary standards were made with fresh distilled deionized water (DIW). Standardizations were performed at the beginning of each group of analyses with working standards prepared every 12-16 hours from a secondary. Working standards were made up in low nutrient seawater (LNSW). Multiple batches of LNSW were used on the cruise. The first batch of LNSW was treated in the lab. The water was re-circulated for ~8 hours through a 0.2 micron filter, passed a UV lamp and through a second 0.2 micron filter. The actual concentration of nutrients in this water was empirically determined during the standardization calculations. The concentrations in micro-moles per liter of the working standards used were: +-----+-------+-------+-------+-------+ | - | N+N | PO_4 | SIL | NO_2 | | | (uM) | (uM) | (uM) | (uM) | |=====|=======|=======|=======|=======| | 0 | 0.0 | 0.0 | 0.0 | 0.0 | +-----+-------+-------+-------+-------+ | 3 | 15.50 | 1.2 | 60 | 0.50 | +-----+-------+-------+-------+-------+ | 5 | 31.00 | 2.4 | 120 | 1.00 | +-----+-------+-------+-------+-------+ | 7 | 46.50 | 3.6 | 180 | 1.50 | +-----+-------+-------+-------+-------+ Quality Control --------------- All final data was reported in micro-moles/kg. NO_3, PO_4, and NO_2 were reported to two decimals places and SIL to one. Accuracy is based on the quality of the standards the levels are: +-------+-----------------------------+ | NO_3 | 0.05 uM (micro moles/Liter) | +-------+-----------------------------+ | PO_4 | 0.004 uM | +-------+-----------------------------+ | SIL | 2-4 uM | +-------+-----------------------------+ | NO_2 | 0.05 uM | +-------+-----------------------------+ Reference materials for nutrients in seawater (RMNS) were used as a check sample run with every station. The RMNS preparation, verification, and suggested protocol for use of the material are described by Aoyama [Aoyama2006] [Aoyama2007] [Aoyama2008], Sato [Sato2010], and Becker et al. [Becker2019]. RMNS batch CM was used on this cruise, with each bottle being used for all runs in one day before being discarded and a new one opened. Data are tabulated below. +-----------+---------------+---------+---------------+ | Parameter | Concentration | stddev | assigned conc | |===========|===============|=========|===============| | - | (umol/kg) | - | (umol/kg) | +-----------+---------------+---------+---------------+ | NO_3 | 33.12 | 0.17 | 33.2 | +-----------+---------------+---------+---------------+ | PO_4 | 2.40 | 0.02 | 2.38 | +-----------+---------------+---------+---------------+ | Sil | | 0.49 | 100.5 | +-----------+---------------+---------+---------------+ | NO_2 | 0.020 | 0.005 | 0.02 | +-----------+---------------+---------+---------------+ Analytical Problems ------------------- There were issues with columns losing efficiency quicky at the start of the cruise. These issues were resolved by cleaning, treating and repacking new columns. There were no other analtical errors. [Armstrong1967] Armstrong, F.A.J., Stearns, C.A., and Strickland, J.D.H., “The measurement of upwelling and subsequent biological processes by means of the Technicon Autoanalyzer and associated equipment,” Deep-Sea Research, 14, pp.381-389 (1967). [Atlas1971] Atlas, E.L., Hager, S.W., Gordon, L.I., and Park, P.K., “A Practical Manual for Use of the Technicon AutoAnalyzer in Seawater Nutrient Analyses Revised,” Technical Report 215, Reference 71-22, p.49, Oregon State University, Department of Oceanography (1971). [Aoyama2006] Aoyama, M., 2006: 2003 Intercomparison Exercise for Reference Material for Nutrients in Seawater in a Seawater Matrix, Technical Reports of the Meteorological Research Institute No.50, 91pp, Tsukuba, Japan. [Aoyama2007] Aoyama, M., Susan B., Minhan, D., Hideshi, D., Louis, I. G., Kasai, H., Roger, K., Nurit, K., Doug, M., Murata, A., Nagai, N., Ogawa, H., Ota, H., Saito, H., Saito, K., Shimizu, T., Takano, H., Tsuda, A., Yokouchi, K., and Agnes, Y. 2007. Recent Comparability of Oceanographic Nutrients Data: Results of a 2003 Intercomparison Exercise Using Reference Materials. Analytical Sciences, 23: 1151-1154. [Aoyama2008] Aoyama M., J. Barwell-Clarke, S. Becker, M. Blum, Braga E. S., S. C. Coverly,E. Czobik, I. Dahllof, M. H. Dai, G. O. Donnell, C. Engelke, G. C. Gong, Gi-Hoon Hong, D. J. Hydes, M. M. Jin, H. Kasai, R. Kerouel, Y. Kiyomono, M. Knockaert, N. Kress, K. A. Krogslund, M. Kumagai, S. Leterme, Yarong Li, S. Masuda, T. Miyao, T. Moutin, A. Murata, N. Nagai, G.Nausch, M. K. Ngirchechol, A. Nybakk, H. Ogawa, J. van Ooijen, H. Ota, J. M. Pan, C. Payne, O. Pierre-Duplessix, M. Pujo-Pay, T. Raabe, K. Saito, K. Sato, C. Schmidt, M. Schuett, T. M. Shammon, J. Sun, T. Tanhua, L. White, E.M.S. Woodward, P. Worsfold, P. Yeats, T. Yoshimura, A.Youenou, J. Z. Zhang, 2008: 2006 Intercomparison Exercise for Reference Material for Nutrients in Seawater in a Seawater Matrix, Technical Reports of the Meteorological Research Institute No. 58, 104pp. [Becker2019] Becker, S., Aoyama M., Woodward M., Baaker, K., Covery, S., Mahaffey, C., Tanhua, T., “GO-SHIP Repeat Hydrography Nutrient Manual, 2019: The Precise and accurate determination of dissololved inorganic nutrients in seawater;Continuos Flow Analysis methods. Ocean Best Practices, August 2019: http://dx.doi.org/10.25607/OBP-555 [Bernhardt1967] Bernhardt, H., and Wilhelms, A., “The continuous determination of low level iron, soluble phosphate and total phosphate with the AutoAnalyzer,” Technicon Symposia, I,pp.385-389 (1967). [Gordon1992] Gordon, L.I., Jennings, J.C., Ross, A.A., Krest, J.M., “A suggested Protocol for Continuous Flow Automated Analysis of Seawater Nutrients in the WOCE Hydrographic Program and the Joint Global Ocean Fluxes Study,” Grp. Tech Rpt 92-1, OSU College of Oceanography Descr. Chem Oc. (1992). [Hager1972] Hager, S.W., Atlas, E.L., Gordon L.I., Mantyla, A.W., and Park, P.K., ” A comparison at sea of manual and autoanalyzer analyses of phosphate, nitrate, and silicate ,” Limnology and Oceanography, 17,pp.931-937 (1972). [Sato2010] Sato, K., Aoyama, M., Becker, S., 2010. RMNS as Calibration Standard Solution to Keep Comparability for Several Cruises in the World Ocean in 2000s. In: Aoyama, M., Dickson, A.G., Hydes, D.J., Murata, A., Oh, J.R., Roose, P., Woodward, E.M.S., (Eds.), Comparability of nutrients in the world’s ocean. Tsukuba, JAPAN: MOTHER TANK, pp 43-56. Calibration Documents =====================