University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 2004 Recovery of the Mersey Estuary from Metal Contamination Watts, Sarah Jane http://hdl.handle.net/10026.1/2133 University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. Recovery of the Mersey Estuary from Metal Contamination By Sarah Jane Watts B.Sc. (Hons.), M.Sc. thesis-submitted'tonhcUniversity of Plymouth I in partiaKfuinimentfor_tfle degree of Doctor ofcPhilosophy School of Earth, Ocean and Environmental Science University of Plymouth Drake Circus Plymouth PL4 8AA In collaboration with: UK Environment Agency (North West Region) University of Plymouth Library Item No. Shelfmark Recovery of the Mersey Estuary from Metal Contamination Sarah Jane Watts B.Sc. (Hons,), M.Sc. Abstract The Mersey Estuziry has received significant quantities of industrial wastes and sewage over several decades. Although contaminant loads are reducing and the estuary is showing signs of recovery, the sediment reservoir remains a repository of historical contamination and still contains high concentrations of trace metals and organic compounds. A combination of hydrodynamic, sedimentary and geochemical processes are responsible for maintaining trace metal concentrations at present-day levels. The distributions of trace metals in bed sediments reflect changes in granulometry, differences in POC content and the magnitude of past inputs rather than the locations of point sources in the estuary. The association of contaminant metals with SPM varies not only with axial changes in salinity and particle concentration but also in response to the relative magnitudes of freshwater and tidal inflows and cyclic variations in water and particulate chemistry that occur on intratidal, intertidal and seasonal timescales. The most influential of these arise from axial changes in dissolved oxygen and the delivery of organic carbon from both external and internal sources which modify the relative degree of sorptive control exerted by Fe, Mn and organic C at different locations in the estuary and at different times. These factors, combined with the efficient trapping of sediments and possible salting out of neutral metal- organic complexes, assist in the retention and internal recycling of particles and associated metals between the bed and water column. Geochemical reactivity is suppressed in Mersey SPM and metal decontamination is not predicted to occur through the loss of particulate metals to the surrounding coastal zone. Rather, it is envisaged that sediment resuspension and the desorption of metals into fresh and low salinity waters, supplemented by the release of metals from tidally stirred diagenetically modified sediments, are more likely to be important long term cleansing mechanisms, v^th the latter occurring particularly during the summer months when bacterial numbers and the degradation of accumulated organic detritus becomes more pronounced. Future declines in metals from bed sediments have been estimated using two methods and two independent data sets. Resulting values are not only metal-dependent but also vary with sediment location. Losses of Cd, Co, Cu, Hg, Ni and Zn are predicted to take up to 40 years, whilst removal of substantially elevated concentrations of Pb in sediments in the upper estuary could span hundreds of years. iii Acknowledgements The author wishes to thank all those who assisted in the completion of this study. • My foremost thanks go to Professor Geoff Millward (Director of Studies, University of Plymouth) for his experience, encouragement, never-ending support and interest in all aspects of the project and my own well being, for which I am truly grateful. • Dr. Andrew Turner (Supervisor, University of Plymouth) for providing useful comments during the preparation of this thesis. • Dr. Peter Jones (North West Environment Agency) for help during the field campaigns, his considerable knowledge of the estuary and general enthusiasm for the project. • Dr. Manuela Martino for use of dissolved metals data and help with sample collection. • Technical staff from the Dept. of Environmental Sciences, University of Plymouth: Mr. Andy Arnold for training in the use of GFAAS, Mr. Andrew Tonkin for training in the use of the CHN analyser and Mr. Derek Henon for performing the particulate HF digests. • Dr. Mark R. Williams for initial training in general trace metal analytical techniques. • Friends and colleagues in the (former) Institute of Marine Studies and the Dept. of Environmental Sciences, particularly Drs. Tracey Jones-Hughes and Mark S. Williams for their friendship, support and good times. • Friends and colleagues (past and present) at Westlakes Scientific Consulting for their encouragement and support during the writing of this thesis, in particular Drs. Adrian and Karen Punt and Paul McDonald. • My friends, for helping to keep me in the 'real world'. Special thanks here go to Kate, Paul and India. • Finally I wish to thank my family, for their love and support throughout all my academic endeavours. This thesis is dedicated to them and also to Mary Brown and Arthur Watts, who would have been so proud. "IVe have come a long way. We have a long way to go. In between we are somewhere. " (Rheinhold Messner's mantra on his solo and unassisted crossing of Antarctica). iv Declaration At no time during the registration for the degree of Doctor of Philosophy has the author been registered for any other University Award. The study was financed with the aid of a Natural Environment Research Council grant provided by the Environment Agency (award no. GST03/1567). This thesis is a holistic treatment of the trace metals component of the NERC Environmental Diagnostics project 'Fate and Impact of Persistent Contaminants in Estuaries and Coastal Waters' (Environment Agency project number 7261). The assistance of all those involved is duly and gratefully acknowledged (see acknowledgements section), in particular Dr. M. Martino for allowing me access to her dissolved metal data and Dr. P. Jones for allowing me to report the results of the Statutory Monitoring Programme for the Mersey Estuary. However, the thesis remains the sole work of the author. A programme of advanced study was undertaken that included: • Guided reading in topics relating to marine chemistry and oceanography. • Development of proficiency in the use of a variety of analytical techniques and instrumentation, particularly in the areas of spectroscopy and radiochemistry. • Further instruction in estuarine and coastal survey techniques, including successful completion of the RYA Level 4 power boat handling certificate. • Consultancy work for the Institute of Marine Studies, University of Plymouth. • Supervision and demonstration of practical field and laboratory techniques for graduate and postgraduate students. • Attendance and presentation of work at relevant scientific conferences and seminars. • Meetings with project co-workers from the universities of Liverpool and Cardiff and the Environment Agency for discussions on project findings and progress. • Production of annual reports for the University of Plymouth and the Environment Agency. Completed courses • 'Analytical Atomic Spectrometry' short course and M.Sc. module, University of Plymouth, 07-12 September 1997. • Research Councils' Graduate School, Otterbum Hall, Otterbum, Northumberland, 04-09 November 1999. • RYA Level 4 power boat handling, University of Plymouth, June 2000. Available Data The original data collected during this study is available as spreadsheets created using Microsoft Excel 97 and stored on the CD-ROM contained in an appendix to copies of this thesis held by the University of Plymouth hbrary. Conferences and Presentations • Attendance: 3"^** Annual LOIS Conference, University of East Anglia, 24-26 March 1998. • Attendance: Royal Society of Chemistry Radiochemical Methods Group Young Researchers Meeting, University of Loughborough, 08 July 1998. • Poster presentation: 'Distribution and reactivity of trace metals in the Mersey Estuary, UK', Challenger Society for Marine Science 8^ Biennial Conference, UK Oceanography '98, University of Southampton, 07-11 September 1998. • Poster presentation: 'The role of particle selection processes and particle reactivity in controlling trace metal transport in the Mersey Estuary', Environmental Diagnostics 2°^ Annual Meeting, Royal Institute of Chartered Surveyors Westminster Centre, London, 20 January 1999. • Oral presentation: 'The distribution and reactivity of trace metals in the Mersey Estuary', ECSA Local Meeting The Coast and Estuaries of North-West England, Edge Hill College of Higher Education, Ormskirk, 08-09 April 1999. • Poster presentation: 'Unreactive particles in the Mersey Estuary?', 3^^ Progress in Chemical Oceanography Conference, PICO III, University of Plymouth, September 1999. • Attendance: Royal Society of Chemistry Environmental Chemistry Group, Chemical Contaminants in Estuaries and Coastal Waters: Practical Applications of Models, Scientific Societies' Lecture Theatre, London, 19 November 1999. • Poster presentation: 'Trace metal reactivity in the Mersey Estuary, UK\ 3*"**