Samples were collected from 3 sites: Big Strytan, Arnarnasstrytan, and Hrisey (see lat/lon below). SCUBA diving was utilized to collect vent fluids and hydrothermal precipitates. Vent fluids for geochemistry were sampled in sterile 60 ml syringes. The first 20 ml was discarded to decrease the amount of seawater contamination during sampling. Vent fluid sampling for dissolved gases consisted of 2 methods: 1) the “syringe-to- syringe” method (STS), and 2) the “syringe-to-bottle” method (STB). The STS method consisted of pulling 40 ml of vent fluid at the end of a dive, transporting it back to the lab, and equilibrating the fluid with 20 ml of purified N2. The gas was then injected into Cali-5-Bond gas sampling bags for transport prior to analysis by GC. The STB method consisted of pulling a known volume of vent fluid (typically 40 ml) into a syringe, and immediately injecting into a 60 ml N2-flushed, evacuated, serum bottle.
Temperatures were measured in situ using a temperature probe. The pH/ORP/Conductivity/TDS were measured on shore using a Myron-L field pH meter. Aliquots for H2S measurements were preserved in the field by precipitation of ZnS following the addition of 1 ml of a 50 mM zinc acetate solution to a 3 ml sample, placed on dry ice, and analyzed in the laboratory with a spectrophotometer at a wavelength of 670 nm. Samples for anion analysis (Br, Cl, and SO4) were filtered in the field (0.2 um), placed on dry ice, and kept frozen until measurement in the laboratory using ion chromatography. Samples for analysis of major cations and trace elements (Na, B, Mg, Si, K, Ca, Al, As, V, Cr, Cu, Zn, Sr, Mo, and W) were preserved in the field by filtering (0.2 um) and acidification with 0.1% ultrapure HNO3, and measured by inductively coupled plasma-mass spectrometry (ICP-MS). Dissolved gases (H2, CH4, and CO), as well as organic acids and DIC, were analyzed at NASA Ames in the lab of Tori Hoehler. D13C-CH4 was measured at Montana State University by Eric Boyd.
Detection Limits:
Lactate 0.067
Acetate 2.754
Formate 2.791
Propionate 0.000
Butyrate 2.862
Valerate 0.000
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