Effects of sample storage on microbial Fe-reduction in tropical rainforest soils

Fe2+ catalyzed iron atom exchange and re-crystallization in a tropical soil

“…They experience periodic O 2 fluctuations that generate intermittent anoxic conditions (Silver et al, 1999) that occur on the scale of days to weeks (Heartsill-Scalley et al, 2007;Liptzin et al, 2011;Hall et al, 2013) and their solid phase Fe is composed predominately of short-range-ordered Fe phases described in Peretyazhko and Sposito (2005) and expected to participate in Fe atom exchange based on pure mineral experiments. We collected the upper 10 cm of the soil from a floodplain location described elsewhere (Peretyazhko and Sposito, 2005;Ginn et al, 2014). Soils were placed in polypropylene ziplock bags, transported at field temperature to the University of Georgia and air-dried at 30°C for 12 h prior to dry sieving (<2 mm) and homogenizing.…”

“…The total soil elemental concentrations were measured by ICP-MS following Li-metaborate fusion (Hossner, 1996) (Acme Labs, Vancouver, BC Canada) with total organic carbon measured via a Carlo Erba Elemental Analyzer (Ginn et al, 2014). The total Fe content of the soil was measured separately for greater accuracy as follows: We added 10 mg of finely ground soil to a Teflon digestion bomb with $3 mL of H 2 O 2 and heated the mixture at 80°C for 30 min.…”

“…Data analysis was performed using the EVA software package (Bruker). The short-range-ordered Fe, Al and Si mineral abundance was measured via a citrate-ascorbate extraction (Ginn et al, 2014); organically-associated Fe, Al and Si were measured with using a sodium pyrophosphate extraction (Sparks, 1996). These extract solutions were analyzed on an ICP-MS (Perkin Elmer, model Elan DRC II).…”

“…Approximately 0.75 g of soil was added to a 125 mL flask in an anoxic glovebox (Coylabs, Grasslake, MI) with a 95%:5% N 2 :H 2 atmosphere and mixed with 75 mL of incubation buffer solution with or without 6.9 lM of HgCl 2 to create "sterile" and "live" treatment sets to prevent Fe II oxidation and suppress Fe reduction in our natural soil (Ginn et al, 2014). The incubation solution was prepared to contain 25 mM KCl and 25 mM of 2-(N-morpholino)ethanesulfonic acid (MES) buffer and $2.5 mM Fe 2+ (aq) .…”

Depth and character of rock weathering across a basaltic‐hosted climosequence on Hawai‘i

“…We monitored Fe II production in the aqueous phase and terminated the experiment once Fe II production began to increase substantially. Storaging tropical soils at 4°C has been recently shown to slow the recovery of Fe reducing organisms (Ginn et al, 2014) and that may have contributed to the slow emergence of aqueous Fe II . Following incubation, size-fractionated samples were isolated by differential centrifugation in an Eppendorf 5430 centrifuge with a F45- Fig.…”