The application of Diffusive Gradients in Thin Films (DGT) for improved understanding of metal behaviour at marine disposal sites

Ruth Parker; Thi Bolam; Jon Barry; Claire Mason; Silke Kröger; Lee Warford; Briony Silburn; Dave Sivyer; Silvana Birchenough; Andrew Mayes; Gary R Fones

doi:10.1016/j.scitotenv.2016.09.183

The application of Diffusive Gradients in Thin Films (DGT) for improved understanding of metal behaviour at marine disposal sites

Sci Total Environ. 2017 Jan 1:575:1074-1086. doi: 10.1016/j.scitotenv.2016.09.183. Epub 2016 Sep 30.

Authors

Affiliations

¹ Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK.
² Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK. Electronic address: thi.bolam@cefas.co.uk.
³ School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
⁴ School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK.

PMID: 27693155
DOI: 10.1016/j.scitotenv.2016.09.183

Abstract

Assessment of the effects of sediment metal contamination on biological assemblages and function remains a key question in marine management, especially in relation to disposal activities. However, the appropriate description of bioavailable metal concentrations within pore-waters has rarely been reported. Here, metal behaviour and availability at contaminated dredged material disposal sites within UK waters were investigated using Diffusive Gradient in Thin films (DGT). Three stations, representing contrasting history and presence of dredge disposal were studied. Depth profiles of five metals were derived using DGT probes as well as discrete analysis of total metal concentrations from sliced cores. The metals analysed were: iron and manganese, both relevant to sediment biogeochemistry; cadmium, nickel and lead, classified as priority pollutants. DGT time-integrated labile flux profiles of the metals display behaviour consistent with increasingly reduced conditions at depth and availability to DGT (iron and manganese), subsurface peaks and a potential sedimentary source to the water column related to the disposal activity (lead and nickel) and release to pore-water linked to decomposition of enriched phytodetritus (cadmium). DGT data has the potential to improve our current understanding of metal behaviour at impacted sites and is suitable as a monitoring tool. DGT data can provide information on metal availability and fluxes within the sediment at high depth-resolution (5mm steps). Differences observed in the resulting profiles between DGT and conventional total metal analysis illustrates the significance of considering both total metals and a potentially labile fraction. The study outcomes can help to inform and improve future disposal site impact assessment, and could be complemented with techniques such as Sediment Profile Imagery for improved biologically relevance, spatial coverage and cost-effective monitoring and sampling of dredge material disposal sites. Additionally, the application of this technology could help improve correlative work on biological impacts under national and international auspices when linking biological effects to more biologically relevant metal concentrations.

Keywords: Bioavailability; DGT (diffusive gradient in thin-films); Disposal; Dredge material; Labile; Metal profiles; Sediments.