Search the data

Nutrient (Phosphate, Nitrate + Nitrite, Nitrite, Silicate), Helium, and Neon - CTD water samples for Cruise JC156

Originator's Protocol for Data Acquisition and Analysis

Nutrients

Acid clean 60 ml HDPE Nalgene bottles were used for all the nutrient sampling, these were initially aged, acid washed and cleaned, and then stored with a 10 % acid solution between samplings. Water column depth profile samples were taken from the OTE bottles from the Trace Metal CTD system and sub-sampled into the Nalgene nutrient bottles from within the trace metal clean laboratory onboard the RRS James Cook. The sample bottles were washed 3 times before taking the final sample, and being capped tightly. These were then taken immediately to the nutrient analysers in the chemistry lab and analysis was conducted as soon as possible after sampling. Nutrient free (Semperguard) gloves were used and other clean handling protocols were adopted as close as possible to the GO-SHIP protocols.

Analysis:

The micro-molar segmented flow colorimetric auto-analyser used was the PML 5- channel (nitrate, nitrite, phosphate, silicate, and ammonium) Bran and Luebbe AAIII system, using classical proven analytical techniques. The instrument was calibrated with home produced nutrient stock standards and then compared regularly against Nutrient Reference Materials, from KANSO Technos, Japan for quality control and checking of analytical standardisation. Batches CA and BU were used during the cruise. The analytical chemical methodologies used were according to Brewer and Riley (1965) for nitrate, Grasshoff (1976) for nitrite, Kirkwood (1989) for silicate and phosphate, and Mantoura and Woodward (1983) for dissolved ammonium. Nanomolar analysis was carried out for ammonium using a fluorimetric detection differential gas diffusion technique, based on Jones R.D, 1991. Nanomolar nitrate, nitrite, and phosphate were analysed using segmented flow colorimetric techniques with 2 metre Liquid waveguides as the analytical flow cells to improve the analytical detection limits. Nitrate and nitrite used the same colorimetric methods as for the micromolar system and for phosphate we used the Zhang and Chi (2002) method.

Helium and Neon

Helium isotope, and helium and neon concentrations were measured on samples drawn from Niskin bottles via tygon tubing and stored in crimped 5/8 " copper tubing using the technique described by Young and Lupton (1983). The gas samples were quantitatively extracted on shore using a water vapor extraction method into 25 ml aluminosilicate glass ampoules (Lott and Jenkins, 1998).

Analysis:

The noble gas abundance measurements were made on a custom designed and built automated cryogenic and vacuum system that incorporated a HIDEN quadrupole mass spectrometer (P/N PCI 1000 1.2HAL/3F 1301-9 PIC type 570309), equipped with an electron impact ion source, triple quadrupole mass filter, and a pulse counting secondary electron multiplier (SEM). As described by Jenkins et al (2019), helium and neon concentrations were determined by ion current peak-height manometry against a calibrated marine air standard and corrected quadratically for size-non-linearity. Helium was measured to 0.3 % and neon was determined to 0.55 %. Earlier methodological details (superseded by the later paper) were presented by Stanley et al, (2009). Helium isotope measurements were made on the same samples using a custom designed and built magnetic sector, dual-collecting mass spectrometer described by Lott and Jenkins (1984); referenced to marine air to an accuracy of 0.15 % or better, and corrected for instrumental non-linearity (dependence of isotope ratio determination on sample size). Similarly, the tritium measurements were made using the He-3 regrowth method devised by Clarke et al (1976) and a second, dedicated magnetic sector, dual-collecting mass spectrometer. All uncertainties were confirmed by replicate analyses of water samples and standards.

References Cited

Brewer P.G. and Riley J.P., 1965. The automatic determination of nitrate in seawater. Deep SeaResearch, 12, 765-72.

Clarke, W.B., Jenkins, W.J. and Top, Z., 1976. Determination of tritium by spectrometric measurement of 3He. International Journal of Applied Radiation and Isotopes, 27: 515-525.

Grasshoff K., 1976. Methods of seawater analysis. Verlag Chemie, Weinheim and New York,317pp.

Kirkwood D., 1989. Simultaneous determination of selected nutrients in seawater. ICES CM1989/C:29.

Lott, D.E., 2001. Improvements in noble gas separation methodology: a nude cryogenic trap. Geochemistry, Geophysics, Geosystems 2, doi: 10.129/2001GC000202.

Lott, D.E., Jenkins, W.J., 1984. An automated cryogenic charcoal trap system for helium isotope mass spectrometry. Review of Scientific Instruments 55, 1982-1988. doi: 10.1063/1.1137692

Lott, D.E., Jenkins, W.J., 1998. Advances in the analysis and shipboard processing of tritium and helium samples. International WOCE Newsletter 30, 27-30.

Mantoura, R.F.C and Woodward, E.M.S, 1983. Estuarine, Coastal and Shelf Science, 17, 219-224.

Jenkins, W.J., Lott, D.E., III and Cahill, K.L., 2019. A Determination of Atmospheric Helium, Neon, Argon, Krypton, and Xenon Solubility Concentrations in Water and Seawater. Marine Chemistry, 211(1): 94-107.

Jones, R. D. 1991. Limnology and Oceanography, 36(4), 814-819.

Jia-Zhong Z. and Jie C., 2002. Automated Analysis of Nanomolar Concentrations of Phosphatein Natural Waters with Liquid Waveguide. Environ. Sci. Technol., 36 (5), pp 1048-1053

Stanley, R.H.R., Baschek, B., Lott, D.E., III and Jenkins, W.J., 2009. A new automated method for measuring noble gases and their isotopic ratios in water samples. Geochemistry Geophysics Geosystems, 10(5): Q05008, doi:10.1029/2009GC002429.

Young, C., Lupton, J.E., 1983. An ultratight fluid sampling system using cold-welded copper tubing. EOS Transactions AGU 64, 735.

JC156 Cruise report

Further information can be found in the JC156 Cruise report.

BODC Data Processing Procedures

Data were submitted containing dissolved and low-level dissolved nutrient sample measurements of ammonium, phosphate, silicate, nitrate + nitrite, and nitrite data, as well as dissolved helium and neon and delta 3-helium measurements. Additional metadata such as station, position, date, time, CTD cast number, CTD bottle number and depth (m) were also included in the file. The data were reformatted and assigned BODC parameter codes. Quality control checks were made and BODC applied flags were applicable. The data were then loaded into the BODC database using established BODC data banking procedures.

A parameter mapping table is provided below:

Data Quality Report

BODC performed quality control checks on the data. Any data values deemed suspicious by the Originator were applied an 'L' flag. Any data values which were below the detection limit of the instrument were applied a '<' flag.