A novel gel‐based technique for the high resolution, two‐dimensional determination of iron (II) and sulfide in sediment

Abstract

Many coastal marine sediments display highly heterogeneous biogeochemistry due to complex biological and chemical interactions. Existing measurement techniques are limited in their ability to characterize the distributions of reduced species at high resolution in two dimensions. To obtain more detailed information than existing methods, a novel technique for the simultaneous high-resolution (1 mm), two-dimensional determination of porewater iron (II), and sulfide using a gel-based diffusive sampler was developed. A diffusive equilibration in a thin-film (DET) hydrogel was colorized by Ferrozine reagent, imaged electronically, and analyzed using computer imaging densitometry. With the selected gel parameters, the method detection limit for iron (II) was 0.6 μmol L -1

Interactive influences of the marine yabby (Trypaea australiensis) and mangrove (Avicennia marina) leaf litter on benthic metabolism and nitrogen cycling in sandy estuarine sediment

“…Particle reworking results in the mixing of organic matter to depth and infauna burrows increase the area of the sediment-water interface favouring solute exchange with the overlying water (Welsh, 2003). Ventilation of these burrows by their residents transports oxygen-rich water to the deeper sediment, influencing the distribution of oxic, suboxic and anoxic sediment zones (Wenzhöfer & Glud, 2004;Robertson et al, 2008Robertson et al, , 2009. Therefore, burrow wall sediments and infauna can provide a substrate for colonising aerobic microbial communities, including nitrifying bacteria (Welsh & Castadelli, 2004;Laverock et al, 2010).…”

Two decades of chemical imaging of solutes in sediments and soils – a review

“…The most recent developments in 2D imaging include simple colorimetric DET techniques for measuring Fe(II) and phosphate [15,16,[35][36][37][38] as well as a 2D DET technique for the measurement of NO 3 À and N 2 isotopic composition [39]. These approaches are discussed in more detail below.…”

“…(1) and (2) M is the mass of analyte bound to the resin gel, Dg is the diffusive layer thickness, D is the diffusion coefficient in the hydrogel, A is the sampling area, and t is the sampling time [41,60]. DGT chemical imaging has so far been used to investigate sediment biogeochemistry as affected by plant roots and animal burrows [15,[36][37][38]53,61], solute dynamics in microbial microniches in sediments [13,16,36,[47][48][49]56,[62][63][64][65] as well as for investigating nutrient and contaminant uptake and solubilisation in the vicinity of terrestrial plant roots [12,50,59]. …”

“…For the investigation of sediment chemistry, typical DET and DGT imaging (and 1D profile) applications were done using flat ($0.5 cm) gel housings that have a sampling window of 2-5 Â 15 cm [11,14,34,49,62]. Recently, a larger and thicker (1.4 cm) gel holder with an 8 Â 17 cm window was used for dual-layer DET-DGT studies [16,36,37]. For sampling, these gel setups are pushed into the sediment, and left for a given period for equilibration or analyte uptake, respectively.…”

“…In early, gel-based methods (diffusive equilibration in thin films (DET), and diffusive gradients in thin films (DGT)), gel slices were inserted into sediments, and subsequently, 2D analysis was performed on the recovered gels [11][12][13][14]. Later, dyeing procedures of entrapped solutes were used for imaging the distribution of specific solutes or processes after gel recovery [15,16]. Parallel to the first DGT methods, real-time imaging of immobilized, luminescent dyes that were sensitive to different solutes, so-called planar optodes, were developed [17][18][19][20][21].…”