Page 81 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

(PVC 3/8 in discharge, Thermo Fisher Scientific, Scoresby VIC, Australia) deployed with a stainless-steel drop tube and a low refill ratio of 40:20 to avoid the removal of dissolved gases in the formation water. The drop tube was lowered to a depth of 75-78 m. The pump and connecting tubes were drained between the wells to avoid carriage of water between well sampling. Formation water for chemical and microbiological analyses was sampled monthly over the 25-month operation period. Samples were immediately processed as described below.
Ionic composition of the well water
Analyses of cation and anion concentrations were carried out at the Mark Wainwright Centre (University of New South Wales, Sydney NSW, Australia). Briefly, cation (B, Ca, Fe, K, Mg, Mn, Na, P, S, Si) concentrations were analyzed using inductive coupled plasma optical emission spectroscopy (ICP-OES, Optima7300DV, Perkin Elmer, Waltham MA, USA) with a Segmented-array Charged-coupled Device (SCD, Perkin Elmer). The setting of the instrument was as follows: forward power 1200 – 1400 W, reflected power 20.0 W, nebulizer gas flow of 0.7 L min-1, plasma gas flow of 10.0 – 15.0 L min-1, aux gas flow of 0.3 L min-1. Anion (F, Cl, Br, NO2-, NO3-, PO43-, SO42-) concentrations were analyzed using ion chromatography (IC, Dionex ICS1000, Dionex Corporation, Sunnyvale CA, USA) with conductivity detection using an Ion Pac AS14-4 mm column (Dionex Corporation) and a mobile phase of 0.8 M Na2CO3/0.1 M NaHCO3. The instrument detection limits were 0.02 mg L-1 for B, Si and Mn, 0.2 mg L-1 for Fe and P, 0.5 mg L-1 for Ca, K, Mg, Na and S, 2 mg L-1 for F, NO2-, NO3- and Br, and 5 mg L-1 for Cl and PO43-.
Total methane and acetate analyses
Total methane (headspace and dissolved) and acetate concentrations were monitored monthly over a period of 25 months. Gas samples were taken from the well-head apertures and were transferred directly into 10 ml gastight serum vials using a gastight glass syringe. Dissolved methane in 100 ml sampled coal formation water was analyzed according to Kampbell and Vandegrift (1998), Since several of these microbial groups are so far impossible to obtain in pure cultures and often even to enrich with modifications. Briefly, formation water was sampled anoxically into 120 ml nitrogen degassed serum vials containing 1 ml of formic acid (Sigma Aldrich, Castle Hill NSW, Australia). Subsequently, samples were equilibrated to room
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