A combined sensor for simultaneous high resolution 2‐D imaging of oxygen and trace metals fluxes

Abstract

A new sandwich sensor, consisting of an O 2 planar optode overlain by a thin (90 μm) DGT layer is presented. This sensor can simultaneously resolve 2-D O 2 dynamics and trace metal fluxes in benthic substrates at a high spatial resolution. The DGT layer accumulates metals on a small particle size (0.2 μm) chelating resin and records the locally induced trace metal flux during the deployment, whereas the planar optode resolves the O 2 dynamic in near real time at the same location in the sediment. Despite its ultrathin composition, the DGT layer has high carrying capacity for trace metals with no saturation problems during application to typical coastal-or contaminated sediments. Combined with laser ablation, accumulated metal fluxes could be resolved at a resolution of ~200 μm, whereas the O 2 images had a resolution of ~100 μm. A 2-D diffusion-reaction model showed that the enhanced smearing and reduced response time of the O 2 signal associated with the additional DGT layer were marginal. To test sensor performance at realistic conditions, it was applied to an artificial burrow system consisting of permeable dialysis tubing flushed with oxygenated seawater. The measurements demonstrated localized mobilization of Ni, Cu, and Pb close to the burrow wall, where O 2 was elevated. The latter was also confirmed for Cu and Pb in natural sediments irrigated by the polychaete Hediste diversicolor. The sandwich sensor has great potential for investigating interrelations between O 2 dynamics and metal mobilization in complex benthic systems such as burrows, rhizospheres, permeable sands, and microbial mats.

Radiolarian tests as microhabitats for novel benthic foraminifera: Observations from the abyssal eastern equatorial Pacific (Clarion–Clipperton Fracture Zone)

“…Future studies focussing on the variability of environmental parameters in relation to these and other sources of fine-scale heterogeneity of deep-sea sediments might lead to a better understanding of abyssal foraminiferal ecology. For example, it might be possible to examine the effect of radiolarian tests on the micro-distribution of oxygen using planar optode techniques (Glud et al, 2009;Stahl et al, 2012 Table 2. Quantitative counts (MC02 and MC04), and qualitative records (MC07 and MC11) of the morphotypes inhabiting radiolarian tests (0-1 cm, >150 µm size fraction).…”

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

“…Recently, dual-layer 'sandwich' sensors that combine planar optodes and DGT gels were applied for the simultaneous imaging of trace metals and pH/O 2 [55,59]. In this assembly, the DGT gel serves as diffusive layer for the overlying optode sensor (Fig.…”

“…In this assembly, the DGT gel serves as diffusive layer for the overlying optode sensor (Fig. 1), therefore very thin DGT gels are required to minimize blurring of the optode image [55]. Ultrathin DGT gels ( 100 mm) have been developed using polyacrylamide [52] and polyurethane [51] hydrogels.…”

“…The DGT technique has since been adopted as an analytical tool for the determination of the availability of nutrients and contaminants to terrestrial [42,43] and aquatic organisms [44], complex dissociation kinetics [45] and also for 2D chemical imaging of the distribution of labile chemical species in both, soils and sediments [11][12][13]15,36,[46][47][48][49][50][51][52][53][54][55][56][57][58][59].…”

“…Solute dynamics around (artificial) animal burrows have been investigated with a similar experimental setup, i.e. DGT-planar optode double layer sensors taped to the wall of an aquarium across the sediment-water interface [55].…”