Evaluation of the Chelex-DGT technique for the measurement of rare earth elements in the porewater of estuarine and arine sediments

Jianyin Huang; Jodie Hills; Peter R Teasdale; Jared G Panther; Feiyue Wang; David T Welsh

doi:10.1016/j.talanta.2021.122315

Evaluation of the Chelex-DGT technique for the measurement of rare earth elements in the porewater of estuarine and arine sediments

Talanta. 2021 Aug 1:230:122315. doi: 10.1016/j.talanta.2021.122315. Epub 2021 Mar 18.

Authors

Jianyin Huang¹, Jodie Hills², Peter R Teasdale³, Jared G Panther², Feiyue Wang⁴, David T Welsh⁵

Affiliations

¹ Scarce Resources and Circular Economy (ScaRCE), STEM, University of South Australia, UniSA, SA, 5095, Australia; Future Industries Institute, University of South Australia, SA, 5095, Australia. Electronic address: Leslie.huang@unisa.edu.au.
² Environmental Futures Research Institute, School of Environment and Science, Griffith University, Gold Coast Campus, QLD, 4215, Australia.
³ Scarce Resources and Circular Economy (ScaRCE), STEM, University of South Australia, UniSA, SA, 5095, Australia; Future Industries Institute, University of South Australia, SA, 5095, Australia.
⁴ Centre for Earth Observation Science, Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada.
⁵ Future Industries Institute, University of South Australia, SA, 5095, Australia; Environmental Futures Research Institute, School of Environment and Science, Griffith University, Gold Coast Campus, QLD, 4215, Australia.

PMID: 33934780
DOI: 10.1016/j.talanta.2021.122315

Abstract

This study describes the validation of a diffusive gradients in thin film (DGT) technique for determining lanthanide rare earth elements (REEs) and in situ measurements of REEs in sediment pore waters. Laboratory experiments demonstrated that Chelex-100 binding layers had uptake efficiencies ranging from 78.0% to 92.3% for all REEs. An eluent of 1 mol L^-1 HNO₃ was optimal with elution efficiencies >80% for all REEs. Mass versus time experiments confirmed that DGT uptake was linear for all REEs at pH 8.1, 6.6 and 3.9 over a period of 3-4 days. Diffusion coefficients (D) for all REEs were derived from these experiments using the slopes of the linear regressions. D values varied with pH but were generally similar to values reported previously. The Chelex-100 DGT technique from this study is highly sensitive for the measurement of REE concentrations with detection limits ranging from 1.8 to 45 ng L^-1 based on 72 h deployments allowing measurements of natural trace REE levels. Chelex-100 DGT devices were deployed in estuarine and marine sediments over a period of 72 h and most REE porewater concentrations (50-10,410 ng L^-1) were successfully measured. Individual depth profiles of REEs showed a complex response, with many peaks and troughs suggesting a high degree of sediment heterogeneity. Depth-averaged REE concentrations showed a typical zig-zag distribution, although patterns varied between sediment types, after the REEs were normalised using the Queensland Mud Composite shale reference. The Chelex-100 DGT technique therefore shows promise for REE measurements in sediments.

Keywords: DGT method Development; Lanthanide rare earth elements (REEs); Sediment pore waters.