Throughout the UK, peat soils act as reservoirs and archives of historical metal pollution from mining, smelting and other historical heavy industry. Evidence of modern pollutants such as tetraethyl-lead from petrol, that's use had been largely stopped by the end of the 20th century, is also present.
Through baseline geochemical surveying and process orientated research undertaken by different science programmes, the BGS has been examining the legacy of this contamination.
A large part of the research has been assessing the reactivity and sources of lead (Pb), Zinc (Zn) and Cadmium (Cd), the uptake into moorland plants and the leaching into surface and groundwater courses from the peat stores.
The Geochemical Baseline Survey of the UK (G-BASE) has sampled many areas of peat soils. It has reported baseline concentrations of metals in areas of peat and associated streams throughout the UK.
Through the survey, areas of metal-rich peat have been identified where there was no prior knowledge of contamination. These include the lowland peat deposits surrounding Manchester and Liverpool such as Chat and Halsall Moss.
The sources of contamination in these mosses were from the night soil and other industrial waste transported out to the drained fenland from the growing urban areas in the late 18th and early 19th centuries.
Peat soils when drained undergo oxidation and therefore lose thickness. The industrial waste and night soil were used to bulk the peat soils out. In particular, levels of Pb and Zn were found to be enriched.
Breward, N. 2003. Heavy Metal contaminated soils associated with drained fenland in Lancashire, England, UK revealed by BGS soil geochemical survey. Applied Geochemistry, 18, 1663–1670.
Contact: Dr Neil Breward
To complement the work published in Breward (2000), funding for a BUFI studentship between BGS and the University of Nottingham was obtained (Student: Nicola Atkinson; BGS Supervisors: Andrew Tye and Neil Breward; University of Nottingham Supervisors: Scott Young & Liz Bailey) with the focus on the bioavailability of Pb in these fenland soils.
The development of an Isotopic Dilution Technique to measure Pb reactivity found that Pb had a lability of ~ 40% in these soils.
Analysis of the potential increase in availability of metals under redox conditions was also examined.
The project also examined the uptake of metals into a range of potential vegetable crops as the land is ideally suited to vegetable production. With new demand for locally produced materials and the reduction of food miles it is anticipated that vegetable growing will again become viable in the peat soils around Manchester and Liverpool.
Atkinson, N.R. 2010. Heavy Metal geochemistry of contaminated fenland soils in NW England. PhD Thesis.
Atkinson, N R, Bailey, E H, Tye, A M, Breward, N, Young, S D. 2011. Fractionation of lead (Pb) in soil by isotopic dilution and sequential extraction. 'Environmental Chemistry.
Contact: Dr Andrew Tye
Various projects have been undertaken on aspects of contamination in the Rookhope Burn Catchment, Weardale. This area forms part of the North Pennines orefield, which has been subject to historic mining of lead and zinc for over two centuries.
The abandoned mine team at BGS has been working on the contamination of stream water in Rookhope Burn. In particular, Zinc concentrations are found to be high.
Sources of contamination include mine waste, old mine workings as well as contributions from the metals stored in the peat.
Banks, V J and Palumbo-Roe, B. 2010. Synoptic monitoring as an approach to discriminating between point and diffuse source contributions to Zinc loads in mining impacted catchments. Journal of Environmental Monitoring, 12, 1684–1698.
Contact: Dr Barbara Palumbo-Roe
Peat soils are archives of historical and recent metal contamination from mining, smelting and other industrial processes as well as the long range aerial deposition of lead from petrol.
These reservoirs of metals are a potential source for uptake into plants and for leaching into surface waters.
Current investigations are examining:
Chenery, S R, Izquierdo, M, Marzouk, E, Klink, B, Palumbo-Roe, B and Tye, A M. In press. Soil-Plant interactions and the uptake of Pb at abandoned mining sites in the Rookhope catchment of the N. Pennines, UK –A Pb isotope study. Science of the Total Environment.
An ongoing BGS–NIGL research collaboration is investigating the sulphur isotopic composition of pore water extracted from anoxic S-high peat, underlying a mine tailings lagoon in a former Pb-Zn mine in Central Wales, UK.
Many historical tailings impoundments have been placed directly on peat bogs; peat can be an excellent low permeability liner and it is also a significant sorbent of contaminants.
Furthermore, in anoxic conditions peat provides an abundant source of organic carbon favouring the reduction of sulphate to insoluble sulphide by sulphate reduction bacteria (SRB) and therefore, attenuating the sulphate contaminant release.
Bacterial sulphate reduction is accompanied by significant isotope fractionation, leaving residual sulphate with elevated δ34SSO4 values.
Measuring the sulphur isotope composition of dissolved sulphate can provide a powerful tool in recognising the signs of natural bioremediation and understanding the role of peat in attenuating mine drainage.
Rothwell, J J, Taylor, K G, Chenery, S R N, Cundy, A B, Evans, M G and Allott, T H E. 2010. Storage and behaviour of As, Sb, Pb and Cu in ombrotrophic peat bogs under contrasting water table conditions. Environmental Science and Technology, 44, 8497–8502.
Rothwell, J J, Taylor, K G, Ander, E L, Evans, M G, Daniels, S M and Allott, T H E. 2009. Arsenic retention and release in ombrotrophic peatlands. Science of the Total Environment, 407, 1405–1417.
For further information please contact Marieta Garcia-Bajo