Investigation of the concentration and isotopic composition of inputs and outputs of Pb in waters at an upland catchment in NE Scotland

Abstract

As a consequence of the accumulation of anthropogenic Pb in upland catchments, there has been much recent concern about the potential mobilisation and transport of Pb from the soils to receiving waters and also the possible harmful effects that this might have on aquatic biota. This paper presents the findings of a two-year study of Pb behaviour in an organic-rich upland catchment at Glensaugh in NE Scotland. Pb inputs to the catchment were characterised by direct measurements of Pb concentration and (206)Pb/(207)Pb ratios in rain water and interception. Pb outputs from the catchment were calculated from measurements on stream water samples taken from the two main streams, the Cairn Burn and Birnie Burn. The relative contribution of Pb from groundwater and throughflow, under different flow conditions (base flow and high flow), to stream waters was investigated via analysis of springs sourced from groundwater and of waters flowing through the various soil horizons (S (surface), A, B, C, and D), respectively. The outcome of intensive sampling and analysis over the two-year time period was that, even with marked reduction in Pb inputs over the past two decades, the catchment was still acting as a net sink for the current atmospheric deposition. Although the Pb isotopic signature for stream water is very similar to that for the contemporaneous rain water ((206)Pb/(207)Pb approximately 1.15-1.16), only a small portion of the rain water is transferred directly to stream water. Instead, the Pb input is transferred to the stream waters mainly via groundwater and it was also confirmed that the latter had a similar Pb isotopic signature. From the Pb isotopic measurements on throughflow waters, however, Pb being removed via the streams contained some previously deposited Pb, i.e. mobilisation of a small portion of soil-derived anthropogenic Pb was occurring. These findings are important not only with respect to the source/sink status of the catchment but also for calculation of the extent of retention of the current atmospheric Pb inputs, which must take account of the release of previously deposited Pb from the catchment soils, a process occurring mainly under high flow conditions.

The isotopic evolution of atmospheric Pb in central Ontario since AD 1800, and its impacts on the soils, waters, and sediments of a forested watershed, Kawagama Lake

“…Given the intensity and extent of atmospheric Pb pollution, there is ongoing interest in the fate of anthropogenic Pb in forest soils throughout the temperate zone of the northern hemisphere (Siccama et al, 1980;Dö rr and Mü nnich, 1989;Dö rr et al, 1990;Friedland et al, 1992;Miller and Friedland, 1994;Johnson et al, 1995;Wang et al, 1995;Wang and Benoit, 1996;Wang and Benoit, 1997;Brännvall et al, 2001b;Semlali et al, 2001;Kaste et al, 2003;Semlali et al, 2004;Klaminder et al, 2008a,b;Kylander et al, 2008). One approach to understanding the transformations and fate of Pb in soils is to study the streams which drain their respective watersheds (LaZerte et al, 1989;Erel et al, 1990Erel et al, , 1991Patterson, 1992, 1994;Tarvainen et al, 1997;Outridge, 2000;Emmanuel and Erel, 2002;Vinogradoff et al, 2005;Graham et al, 2006;Klaminder et al, 2006;Bindler et al, 2008b;Bur et al, 2009;Landre et al, 2009). Concentrations of total dissolved Pb in natural waters may be very low (Hirao and Patterson, 1974;Erel et al, 1991), with values reported for surface waters (Field and Sherrell, 2003) and recent groundwaters (Shotyk et al, 2010) below 1 ng/L.…”

Quantifying hydrological budgets and pathways in a small upland catchment using a combined modelling and tracer approach

“…The sampling was carried out in conjunction with a regular 2-week sampling programme for Pb concentration and isotopic composition, . Time-series of daily precipitation, mean daily flow and mean daily temperature for ECN site at Glensaugh, together with dates of salt dilution gauging and spatial sampling survey as described in Vinogradoff et al (2005). Samples were taken from each of the six stream sites, three soil pits, precipitation, suction cup lysimeters sited close to the streams, and a number of surface water sources emerging from hillslope springs.…”

Sediment–Water Interactions in an Eroded and Heavy Metal Contaminated Peatland Catchment, Southern Pennines, UK

“…Dissolved lead values from the mixing experiment are very similar to the range of values measured during storm events at UNG (Table II). Dissolved lead levels in upland peatland streams have often been explained by the leaching of lead from catchment peats (e.g., Lawlor & Tipping, 2003;Vinogradoff et al, 2005). Although the mixing experiment was conducted under a worst-case scenario basis, where a large sample of contaminated peat was mixed with acidic stream water, the study establishes empirically that in-stream processing may be important in controlling dissolved lead levels in peatland streams, and can potentially account for the elevated stream water lead concentrations in these systems.…”

“…In a study of surface waters in the English Lake District by Lawlor and Tipping (2003), mean lead concentrations in three Suspended sediment concentration c mg kg −1 d mg l −1 e μg l −1 tributaries of the River Duddon, were 0.42, 0.23 and 0.70 μg l −1 . Vinogradoff et al (2005) measured dissolved lead concentrations over a two-year period at an upland stream at Glensaugh, NE Scotland. Dissolved lead concentrations ranged from 0.08 to 7.53 μg l −1 , with a mean of 0.60±0.71 μg l −1 .…”

“…Dissolved lead concentrations in upland peatland streams have been explained by leaching of dissolved heavy metals from catchments peats, as groundwater moves through contaminated layers of the peat into the fluvial system (e.g., Lawlor & Tipping, 2003;Vinogradoff et al, 2005). However, sedimentassociated heavy metals in fluvial systems are subject to adsorption and desorption processes, where heavy metals can move between particulate and dissolved phases (Foster & Charlesworth, 1996).…”