The pollution history of two urban lakes in Coventry, UK

    Student thesis: Doctoral ThesisDoctor of Philosophy


    Human society has influenced the environment for at least the
    last 15000 years but, since the Industrial Revolution, the
    resultant environmental impacts have become more widespread.
    Lake and reservoir bottom-sediments have been widely used in
    many studies for reconstructing this impact over medium
    timescales (tens to hundreds of years). Few long-term studies
    of hydrological change exist and sediments are useful as
    surrogates for direct monitoring since they are sensitive to
    change within the catchment. This study uses the properties of
    urban lake sediments in order to reconstruct environmental
    pollution history.
    The two principal objectives of this study were the
    reconstruction of historical atmospheric, point source and
    diffuse heavy metal pollution in an urban environment and the
    evaluation of the lake-sediment record as a source of proxy
    hydrological data over the last 100-150 years.
    A paired lake-catchment study was undertaken by comparing
    the records contained in a closed and an open lake. The closed
    lake (Swanswell Pool) is situated in the centre of the city of
    Coventry where the main source of pollution is atmospheric.
    This site provides a contrast to an open basin (Wyken Pool)
    with a multi- source catchment in addition to an atmospheric
    Trends in urban lake sediment cores indicate increasing
    heavy metal concentrations upcore, with cultural enrichment
    factors for individual heavy metals of between 55.4 and 2.6.
    Storage of heavy metals in the catchment of the closed basin
    were significant, although it was found that up to 85% of the
    zn and 90% of the Pb were actually stored in the lake
    sediments. Catchment sources contributed up to 5 times more
    than the atmosphere in the Wyken Slough catchment. Heavy
    metals budgets were calculated, and these showed that loadings
    of metals have increased by up to 7.5 times between 1850 and
    the present day. Sequential digestion of the lake sediments at
    both sites showed that the important fractions containing
    heavy metals were Fe and Mn oxides and organic matter. The
    heavy metals associated with these fractions could be
    remobilised with changing environmental conditions, but an
    analysis of contemporary water quality indicated that, at
    present, suitable Eh and pH conditions for remobilisation did
    not occur.
    It was concluded that these urban lakes do preserve the
    heavy metals record and can provide surrogate data on medium
    term environmental change. However, the complex mixture of
    materials associated with urban sedimentation resulted in a
    lack of correlation between heavy metals and mineral magnetic
    properties in either lake, and in the catchment of Wyken
    Slough. Hence mineral magnetic properties of sediments in
    urban catchments do not appear to be a suitable surrogate for
    heavy metals analysis.
    Urban lakes appear to provide a much-neglected opportunity
    for palaeolimnological reconstruction over a period when
    little directly monitored data exists.
    Date of Award1994
    Original languageEnglish
    Awarding Institution
    • Coventry University

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