The recent sedimentation history of Aqualate Mere (central England): assessing the potential for lake restoration

As part of English Natures Lakes Flagship Project to address adverse environmental impacts on selected, important lakes, a proposal has been made to dredge Aqualate Mere. The site has experienced rapid, recent sedimentation thought to be derived from a nearby canal. The aim of this study has been to determine the recent sedimentation history of the site in order to assess the possibility of the disposal to land of its sediments and the efficacy of this form of lake restoration. A predominantly clayey silt layer was found across the lake beneath which darker, organic-rich sediments were noted. This transition may represent the input of canal-derived sediments, although it may reflect other environmental changes at this time. The radiometric dating technique employed was unable to date this sediment boundary. A further change in the characteristics of the upper part of the clayey silt layer may represent an additional influence of the canal. Heavy metal levels were modest, whereas nutrient levels were relatively high and some pesticides were detected. Topsoil erosion supplying nutrients and other compounds associated with agriculture have been an important source of the lower layers of the clayey silt sediments in particular. The highest levels of most pollutants were found in the finer sediments in the uppermost (post-1950s) part of the sediment profile. These sediments appear to reflect a change in the characteristics of the sediments of the canal, which was associated with a change in the nature of its water supply. The key geochemical properties of the sediments should not preclude the land-based disposal of dredged materials under current UK regulations for waste management. Accurate estimation of sediment quantities was limited, as the interface between the recent and underlying sediments was not positively identified at all sample points.