In situ evaluation of DGT techniques for measurement of trace metals in estuarine waters: a comparison of four binding layers with open and restricted diffusive layers

Abstract

Four different DGT binding layers were used to make selective measurements of trace metals in coastal waters within The Broadwater (Gold Coast, Queensland). Chelex and PAMPAA (polyacrylamide-polyacrylic acid) binding layers were used to measure cations (Cd, Co, Cu, Mn, Ni, Pb, Zn), and Metsorb was used to measure anions (Al, As, Mo, Sb, V, W). A mixed binding layer (MBL) containing both Chelex and Metsorb was used to measure each of the trace metals and determine diffusive boundary layer (DBL) thicknesses. DGT measurements that were not corrected for the DBL thickness (0.049-0.087) were underestimated by 70% on average. Good agreement was observed between DGT-MBL and DGT-Chelex for measurement of Cd, Co, Cu, Ni, Pb and Zn, and between DGT-MBL and DGT-Metsorb for As, Sb and V. DGT-MBL measured significantly higher concentrations for Mn (compared with DGT-Chelex) and Al (compared with DGT-Metsorb). DGT-Chelex measured only 6-8% of Al species measured by either DGT-MBL or DGT-Metsorb. DGT-PAMPAA measurements of Cu, Pb and Al were lower than those of either DGT-MBL or DGT-Chelex varying from 74-81% for Cu to 54-70% for Pb and 51-55% for anionic Al(OH)4(-), suggesting that this binding layer may make more selective measurements. All measured trace metal concentrations were well below ANZECC water quality guidelines, except for Cu which was 2 to 10 times higher than trigger values. Each of the DGT techniques was deployed using both open and restricted diffusive layers (ODL and RDL). Most trace metal measurements were not significantly different with ODL and RDL for all binding layers. However, concentrations of Cu (CRDL/CODL = 0.68-0.75) and Al (CRDL/CODL = 0.73-0.79) were significantly different with DGT-MBL, DGT-Chelex and DGT-Metsorb.

Developing Autonomous Observing Systems for Micronutrient Trace Metals

“…There are several types of passive sampling devices that have been developed over the past 30 years. Among these, Diffusive Gradient Thin (DGT) Gels and, more recently, Polymeric Inclusion Membranes (PIMs) have been deployed in coastal and inland waters (Twiss and Moffett, 2002;Shiva et al, 2016;Almeida et al, 2017), and appear to have the most potential for micronutrient metal determinations. DGTs were also used successfully (analyzing a suite of trace metals at sub-nanomolar level) on discrete samples from the Southern Ocean (Baeyens et al, 2011) and more recently aboard a SeaExplorer glider in the Mediterranean Sea (Baeyens et al, 2018).…”

Fly Ash Modified Coalmine Solid Wastes for Stabilization of Trace Metals in Mining Damaged Land Reclamation: A Case Study in Xuzhou Coalmine Area

“…Several kinds of methods have been developed for study of occurrence state, such as chemical sequential extraction, diffusive gradients in thin-films (DGT), spectral analysis, low temperature ignition, etc. Methods like DGT, which was commonly used in detection of trace metals in water and sediments, it is not suitable for analysis of trace metals in solid materials like coal gangue [ 36 , 37 ]; spectral analysis like nuclear magnetic resonance (NMR), electronic spectroscopy, were direct methods for trace metal detection, which were suitable for determining trace metal contents in coal with high precision; however, for occurrence states it was not accurate enough [ 38 ]; low temperature ignition was also a common method, which has similar limitation to spectral analysis in detection of occurrence states [ 39 ]. Therefore, for rock materials coming from coalmines in this research, we need to study series of substances and minerals combined with trace metals in different occurrence states, the method of sequential extraction is the most appropriate one.…”

Evaluation of Discrete and Passive Sampling (Diffusive Gradients in Thin-films – DGT) Approach for the Assessment of Trace Metal Dynamics in Marine Waters – a Case Study in a Small Harbor

“…[10,11,18] According to European Water Framework Directive [19] some trace metals (Cd, Pb, Hg and Ni) are considered as of priority concern and measurement of their bioavailability is suggested either indirectly by modeling of their speciation or directly by utilizing specific measurement methodology. [6,[20][21][22] Due to the generally very low concentrations of trace metals in natural waters, techniques for their determination and speciation need to have high sensitivity, precision and accuracy. Passive sampling is an alternative and promising approach for trace metals monitoring and operational speciation.…”

“…It has a satisfactory detection limit, and allows measurement of free ions and labile organic/inorganic complexes in water, soil or sediment. [7,8,10,11,21,23] Since DGTs can be deployed in water over a defined period of time (from a few days to approximately two months), the resulting concentration represents the time weighted average (TWA) concentration of reactive species. [7,24] Concentrations determined by this technique are known as DGT-labile and represent potentially bioavailable metal forms.…”