Tracing lake pollution, eutrophication and partial recovery from the sediments of Windermere, UK, using geochemistry and sediment microfabrics

Abstract

Many lakes undergo anthropogenically driven eutrophication and pollution leading to decreased water and sediment quality. These effects can enhance seasonally changing lake redox conditions that may concentrate potentially toxic elements. Here we report the results of a multi-method geochemical and sediment microfabric analysis applied to reconstruct the history of cultural eutrophication and pollution of the North and South Basins of Windermere, UK. Eutrophication developed from the mid-19th to the earliest 20th centuries.Enhanced lake productivity is indicated by increased sedimentary δ 13 C, and increased pollution by a higher concentration of metals (Pb, Hg, and As) in the sediment, likely enhanced by incorporation and adsorption to settling diatom aggregates, preserved as sedimentary laminae. In the South Basin, increasing sediment δ 15 N values occur in step with Zn, Hg, and Cu, linking metal enrichment to isotopically heavy nitrate (N) from anthropogenic sources. From around 1930, decreases in Mn and Fe-rich laminae indicate reduced deep-water ventilation, whereas periods of sediment anoxia increased, being most severe in the deeper North Basin. Strongly reducing sediment conditions promoted Fe and Mn reduction and Pb-bearing barite formation, hitherto only described from toxic mine wastes and contaminated soils. From 1980 there was an increase in indicators of bottom water oxygenation, although not to before 1930. But in the South Basin, the continued impacts of sewage is indicated by elevated sediment δ 15 N. Imaging and X-ray microanalysis using scanning electron microscopy has shown seasonal-scale redox mineralisation of Mn, Fe, and Ba related to intermittent sediment anoxia. Elevated concentrations of these metals and As also occur in the surficial sediment and provide evidence for dynamic redox mobilisation of potentially toxic elements to the lake water. Concentrations of As (up to 80 ppm), exceed international Sediment Quality Standards. This process may become more prevalent in the future with climate change driving lengthened summer stratification.

Current perspectives on the capabilities of high resolution XRF core scanners

“…Another major storm surge led to significant coastal damage in low lying areas of countries Figure 5) also demonstrate that diffusion of reduced mobile Mn and Fe occurred from the anoxic sediment and was precipitated at the redox boundary near the sediment-water interface (Fielding et al, 2019).…”

“…The onset of the organic rich sediment at ~ 25 cm depth is equivalent to 1850 and reflects the initial impact of cultural eutrophication in the lake caused by significant increases in population, tourism, pastoral farming and sewage inputs. The red continuous lines represent Itrax data and are compared with quantitative WDXRF data (green continuous line with red filled circles; adapted from Fielding et al, 2019). The WDXRF concentration maxima are Mn 9.6 wt%, Fe 9.03 wt%, Ti 0.47 wt%, P 0.80 wt%, Ba 2000 ppm, Cu 109 ppm, Zn 1680 ppm, As 81 ppm and Pb 590 ppm.…”

Past Metal(loid) Pollution Records Inferred from the Sediments of Bukit Merah Reservoir Perak, Malaysia

“…Sediments contaminated by toxic metals are major threats and can directly affect the sediment-dwelling biotas, wildlife, and human health due to their harmful nature [6][7][8][9][10]. What's more is that under changing lake environmental conditions, for example, changing redox conditions caused by seasonal eutrophication, sedimentary toxic metals can be released into the above water column, increasing bioavailability [11][12][13][14].…”

Feasibility Analysis of the Sustainability of the Tres Palos Coastal Lagoon: A Multifactorial Approach

“…Eutrophication is identified as a process that causes the growth of plants due to the enrichment of nutrients disposed into a waterbody, which has been considered one of the main problems in coastal ecosystems [17][18][19][20][21]. The eutrophication process may occur either through natural causes or as a result of human activities and/or events, such as human settlements, which generate activities that damage the trophic state of water bodies [18,[22][23][24][25][26][27][28][29]. The concept of cultural eutrophication has been incorporated as a process mainly derived from human activities, such as deforestation [30], the use of fertilizers in agriculture [31], and nitrogen emissions [32], among the most important, all of which contribute to trophic state changes in water bodies.…”