Data report: quantification of potential drilling contamination using perfluorocarbon tracer at IODP Expedition 329 sites

Contamination tracer testing with seabed drills: IODP Expedition 357

“…The use of synthetic tracers in drilling fluids to monitor for potential contamination of drill core samples for microbiological analysis has become fairly routine during microbiology-focused expeditions (Inagaki et al, 2015;Lever et al, 2006Lever et al, , 2013Smith et al, 2000;Friese et al, 2017;Sauvage et al, 2016). Perfluoromethylcyclohexane (PFC) has been identified as an ideal tracer because of the large range of concentrations that are detectable (i.e., across 6 orders of magnitude) with a gas chromatograph equipped with an electron capture detector (GC-ECD) (Smith et al, 2000;Lever et al, 2006;Sauvage et al, 2016). Recent reports have also demonstrated the use of other fluorescent solutions (Friese et al, 2017;.…”

“…During seafloor drilling with a drillship such as the JOIDES Resolution or Chikyu, drilling fluids (muds) are prepared at the sea surface and injected into the drill pipe, and the concentration of PFC tracer delivered into the flush water can be closely monitored and adjusted to reach saturating conditions (roughly 1 mg L −1 ), as described in detail elsewhere (Sauvage et al, 2016;Lever et al, 2006). Similar approaches were also recently used for platform drilling in the relatively shallow waters of the Baltic Sea on IODP Expedition 347, where PFC tracer was added to drilling muds at the platform prior to injection into the borehole (Andrén et al, 2015).…”

“…Shipboard PFC tracer analysis followed established protocols (Smith et al, 2000;Lever et al, 2006;Sauvage et al, 2016). Using a heated (70 • C) disposable plastic 3 mL syringe fitted with a two-way stopcock and a 51 mm, 22-gauge Hamilton needle, a 2 mL headspace sample from either sample or standard vials was injected into the splitless injector on Agilent 7890A GC system GC-ECD, kindly provided by Douglas Connelly of the University of Southampton.…”

“…It is important to note that all sample processing, as well as steam-and flame-sterilization of implements, occurred in the same laboratory, which lead to a buildup in ambient PFC concentrations in the atmosphere as assessed by collection of regular laboratory air blank samples. All of the frozen core subsamples were analyzed on a Shimadzu GC-17A system GC-ECD with a splitless injector, kindly provided by Steven D'Hondt at the University of Rhode Island Graduate School of Oceanography, following methods described elsewhere (Sauvage et al, 2016). The GC-ECD was equipped with a 15 m length × 53 µm inner diameter × 15 µm coating thickness HP PLOT Al/M column run with ultrahigh-purity nitrogen carrier gas at 30 mL min −1 with an initial column temperature of 120 • C for 3.0 min, followed by a 20 • C min −1 ramp to 150 • C and held for 1 min.…”

IODP Technical Note

“…It also produces sediment cores with the least amount of visual disturbance relative to the other coring systems, and therefore has the lowest likelihood of microbiological contamination when coring soft to semiconsolidated sediments. When sediments are recovered without disruption, they generally have a lower potential for contamination from seawater circulated in the borehole and/or drilling mud (House et al, 2003;Lever et al, 2006;Sauvage et al, 2017). In addition to a lower likelihood of contamination during drilling, piston-cored sediments can easily be sampled after sectioning on the catwalk from the center of the whole-round (WR) sediment section (i.e., no contact with the plastic core liner), where the likelihood for contamination is lower.…”