The Derwent Estuary is highly enriched in potentially toxic elements, such as Zn, Pb, Cu, As, Hg and Cd, owing to inputs from historical industrial activity adjacent to the river, predominantly prior to strict environmental protections introduced in the 1970s. Contaminants are now buried at shallow depths within the sediment profile, in one or two highly concentrated layers decreasing in concentration away from an electrolytic zinc refinery, regarded as the main source of the contaminants. Enriched metals (Zn, Pb, Cu, Cd and As) in the estuary were estimated from data collected from 37 sediment cores using a portable X-ray fluorescence spectrometer that was validated against inductively coupled plasma mass spectrometer analyses. The thickness of the metal and metalloid enriched layers ranges from 32.5 to 107.5 cm, with an average thickness of 63 cm. Sedimentation rates based on this layer and the time since the start of zinc processing are approximately 0.46 cm/year. Sedimentation rates based on the thickness since maximum metal and metalloid concentrations are between 0.17 and 1.64 cm/year. Based on these sedimentation rates, the average time it will take for surface sediments to return to background metal and metalloid concentrations, if left undisturbed, is approximately 123 years.

Item Type:	Refereed Article
Keywords:	Derwent, contamination, portable X-ray fluorescence, sediment, heavy metals, Derwent Estuary, Tasmania, contamination, sediment cores, sedimentation, rehabilitation time frame
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Marine geoscience
Objective Division:	Environmental Management
Objective Group:	Marine systems and management
Objective Field:	Marine systems and management not elsewhere classified
UTAS Author:	Meffre, S (Dr Sebastien Meffre)
UTAS Author:	Chase, Z (Professor Zanna Chase)
ID Code:	149301
Year Published:	2022
Deposited By:	CODES ARC
Deposited On:	2022-03-24
Last Modified:	2022-04-26
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