Identifying evidence for past mining and metallurgy from a record of metal contamination preserved in an ombrotrophic mire near Leadhills,SW Scotland,UK

Abstract

This study presents a new 3600-year record of past metal contamination from a bog located close to the Leadhills and Wanlockhead orefield of southwest Scotland. A peat core, collected from Toddle Moss, was radiocarbon (¹⁴C) dated and analysed for trace metal concentrations (by EMMA) and lead isotopes (by ICP-MS) to reconstruct the atmospheric deposition history of trace metal contamination, in particular, lead. The results show good agreement with documented historical and archaeological records of mining and metallurgy in the region: the peak in metal mining during the 18th century, the decline of lead mining during the Anglo-Scottish war and lead smelting during the early medieval period. There may also have been earlier workings during the Late Bronze and Iron Ages indicated by slight increases in lead concentrations, the Pb/Ti ratio and a shift in ²⁰⁶Pb/²⁰⁷Pb ratios, which compare favourably to the signatures of a galena ore from Leadhills and Wanlockhead. In contrast to other records across Europe, no sizeable lead enrichment was recorded during the Roman Iron Age, suggesting that the orefield was not a significant part of the Roman lead extraction industry in Britain. These findings add to the various strands of archaeological evidence that hint at an early lead extraction and metallurgical industry based in southern Scotland. The results also provide further evidence for specific regional variations in the evolution of mining and metallurgy and an associated contamination signal during prehistoric and Roman times across Europe.

Keywords

lead Leadhills mining peat stable isotope analysis Wanlockhead

Introduction

Since its first use approximately seven millennia ago, lead has played an important role in human history, including aspects of art, medicine and technology (Hong et al., 1994; Nriagu, 1998). Lead became particularly important in the 5th millennium bc with the discovery of new smelting and cupellation techniques for lead–silver alloys, and by Roman times, the use of lead was widespread (Nriagu, 1983, 1996). At present, there is a paucity of archaeological evidence for lead mining in prehistoric Britain. It has been proposed that lead deposits in Wales, and by inference elsewhere in Britain, were exploited for lead and silver, since the location of most of the prehistoric mines (where copper was the main target) mostly occur in places with a long tradition of lead and zinc mining (Bick, 1999; Timberlake, 2009). Evidence of limited working of the lead veins and crushing of ores at the Bronze Age mine of Copa Hill in central Wales (Timberlake, 2003) provides some tentative evidence for the extraction of lead ore approximately 300–500 years before its use in metalwork, a phenomenon that might represent a period of metallurgical experimentation rather than actual production (Timberlake, 2003).

Lead in Bronze Age artefacts confirms that it was being used in Britain prior to 1500 bc and hints at the probable early exploitation of insular sources and trade in metal ore (Rohl and Needham, 1998). A smelted lead bead necklace in an Early Bronze Age grave was found in southeast Scotland (Hunter and Davis, 1994), and other early lead finds have been reported from Cornwall (Shell, 1979) and Co. Tipperary (Rafferty, 1961). Lead was also intentionally being alloyed with copper and tin to produce bronze by the Middle–Late Bronze Age (Rohl and Needham, 1998; Tylecote, 1986). Small pieces of lead have also been found in Late Bronze Age occupation sites (e.g. Needham and Hook, 1988). The precise sources of this lead remain a matter for speculation (Barber, 2003).

Archaeological evidence for lead extraction, objects and its wider use in later prehistory is also scant. Lead was a rare addition to northern British alloys during the Iron Age (Dungworth, 1996), and only a few examples of lead use in ornaments, or as solder to secure iron objects, exist in Scotland (Toolis, 2007). Roman lead extraction and smelting is more abundant, with known mines and/or smelting sites occurring at Charterhouse in the Mendips, SW Britain, Alderley Edge in Cheshire and sites in Wales (Timberlake et al., in press), but so far, there are no known sites in Scotland. One region that has been not fully investigated is the Leadhills and Wanlockhead orefield in SW Scotland. A study is therefore warranted, especially given the recent discovery of a stone hammer in Wanlockhead, which is indicative of early mining (Pickin, 2008).

The aim of this study was to reconstruct the history of exploitation of insular ore sources in the Leadhills/Wanlockhead orefield from prehistory to the present. To do so, we present an atmospheric metal contamination history from an ombrotrophic mire, Toddle Moss, for the last 3600 years using total concentrations, Pb/Ti ratios and lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb) contained in the peat.

Materials and methods

Location, sampling and sub-sampling strategy

The orefield of Leadhills and Wanlockhead, on the border of Dumfriesshire and Lanarkshire, SW Scotland (Figure 1), is rich in metalliferous deposits as a result of two phases of mineralization in Ordovician sediments: a quartz vein mineral phase of Carboniferous age and a possibly metallic one of lead and zinc, both of the Carboniferous era. This was followed by a later phase of secondary enrichment (Pattrick and Polkya, 1993).

Figure 1.

(a) Location of study area in Britain, (b) location of Leadhills, Wanlockhead and Toddle Moss and (c) evidence of early lead working after Pickin (2010). The place name ‘bail’ is considered to indicate a lead smelting site.

Toddle Moss is located approximately 4 km northwest of the village of Leadhills and 0.5 km east of Elvanfoot in the Elvan Water river valley (Figure 1). This area has a rich history of mining. Alluvial sediments have been worked in this valley for gold, and lodes rich in lead and copper have also been exploited, particularly in the ad 1700s (Chapman and Leake, 2005; Rowan et al., 1995). Toddle Moss is an ideal site for studying past records of metal pollution because the bog is ombrotrophic (‘rain fed’ only) and receives inputs, including pollutants, solely from the atmosphere via precipitation and dry fallout.

A 7.5-m-deep Sphagnum–Eriophorum-rich peat core was taken from Toddle Moss using a Russian corer with 30 cm × 10 cm chamber in 2004. The samples were placed in plastic guttering, wrapped in polythene and placed in cold storage. The top 3.5 m was analysed in this study.

Chronology

Radiocarbon dates were determined at Beta Analytic Ltd (Miami) and the Poznań Radiocarbon Laboratory using conventional and accelerator mass spectrometry (AMS) methods, respectively. The total carbon of one sample of fresh peat (Beta-15142) was dated using conventional radiometric dating. For AMS, a 1-cm-thick slice of peat (Poz-19215) and Sphagnum macrofossils (Poz-56748) were selected for dating (cf. Nilsson et al., 2001; Piotrowska et al., 2011).

To provide a highly resolved chronology for the last 100–150 years, the unsupported ²¹⁰Pb_un activity within samples towards the peat surface was ascertained by subtraction of the supported component (measured as ²¹⁴Pb at 295.22 and 351.93 keV) from the total ²¹⁰Pb activity measured at 46.54 keV (Wallbrink et al., 2002). ²¹⁰Pb and ²¹⁴Pb activities were measured using EG&G ORTEC hyper-pure Germanium detectors in a well configuration (11 mm diameter, 40 mm depth) housed at Coventry University. The method for calculating the depth–age relationship follows procedures described by Appleby and Oldfield (1978), Appleby (2001) and Walling et al. (2002). The CRS dating model was used to calculate ages as accumulation rates varied down core (Appleby, 2001; Appleby et al., 1988). The CLAM software package (Blaauw, 2010) was used to create an age–depth model, combining the ¹⁴C and ²¹⁰Pb ages, to infer approximate ages for all levels.

Geochemical analyses

The core was cut into contiguous 1-cm-thick slices, oven dried at 40°C and homogenized to improve the efficiency of the chemical digest and to provide better representation of the total metal concentration within the samples. Calcium and magnesium were determined by inductively coupled plasma–optical emission spectrometry (ICP-OES). An estimation of the efficiency of the digestion method and of the accuracy of the analytical measurements was obtained through the use of replicate sub-samples, spiked blanks and certified reference materials (Ebdon et al., 1998; Fifield and Kealey, 2000). Spiked samples of known concentration (10 mg/L) were used to test the efficiency of the acid microwave digestion. Two certified reference materials were also used: Sphagnum energy peat (NJV 94-2) and Carex energy peat (NJV 94-1). The reference materials were imported from the Swedish University of Agricultural Sciences, Department of Agricultural Research for Northern Sweden, Laboratory for Chemistry and Biomass. Standards of known metal concentrations were used to calibrate the instrument and to ensure it was performing at its optimum efficiency (Holler et al., 1996). Total metal concentrations in each sample are expressed in units of microgram per gram.

Recovery of calcium and magnesium from the CRMs for Sphagnum and Carex was between 101% and 130%. Three spiked samples yielded recovery of between 101% and 114%. These results suggest that metal recovery using the microwave digestion was very efficient and that the ICP-OES provided reliable data.

The elemental composition of 89 dried, milled and homogenized samples between 0 and 300 cm depth were obtained by EMMA-XRF analyses (Cheburkin and Shotyk, 1996; Weiss and Shotyk, 1998) including concentrations of major and trace lithogenic elements (silicon, aluminium, titanium, gallium, yttrium and zirconium) and trace metals and metalloids (lead, chromium and arsenic). The instruments are hosted at the RIAIDT (Infrastructure Network for the Support of Research and Technological Development) facility of the University of Santiago de Compostela, Spain. Standard reference materials were used for the calibration of the instruments. Quantification limits were 0.001% for Ti, 0.01% for Al, 0.05% for Si, 0.5 µg/g for Pb and 1 µg/g for other trace elements. Replicate measurements were taken for one of every five samples in order to account for reproducibility; all replicates were within 5% agreement.

A total of 28 sub-samples of peat from the same core were selected for lead isotope analysis at the School of Geosciences, University of Edinburgh. Sub-samples (~0.25 g) were air-dried, then washed at 450°C for 4 h and finally digested using a modified US EPA Method 3052 Protocol microwave-assisted HF-HNO₃ digestion method (Yafa and Farmer, 2006; Yafa et al., 2004). Digests were evaporated to 1 mL on a hotplate and then made up to 25 mL with 2% (v/v) HNO₃. All reagents used in sample preparation were of the highest analytical quality available, that is, Aristar nitric acid (69%) and hydrofluoric acid (48%) and high purity water (18.2 MΩ cm) from a Milli-Q water system (Millipore, Watford, UK). Lead isotopic ratios were determined in the prepared 2% v/v HNO₃ solutions using a PlasmaQuad (PQ) 3 ICP-MS instrument (Thermo Electron, Winsford, UK), equipped with a Meinhard nebulizer, nickel sampler and skimmer cones, Gilson autosampler and a Gilson Minipuls 3 peristaltic pump (Anachem, Luton, UK). A solution of the National Institute of Standards and Technology (NIST) common lead isotopic reference standard SRM 981 (²⁰⁶Pb/²⁰⁷Pb = 1.093, ²⁰⁸Pb/²⁰⁶Pb = 2.168, ²⁰⁸Pb/²⁰⁷Pb = 2.370) was used for calibration and mass bias correction (Farmer et al., 2000). Analytical precision on these ratios was typically <±0.2%.

To ensure the quality of analytical procedures and data, an ombrotrophic peat reference material (NIMT/UOE/FM001) (Yafa et al., 2004) was analysed along with the samples. The mean values (n = 5) of 1.177 ± 0.001, 2.093 ± 0.002 and 2.463 ± 0.004 determined for the isotope ratios ²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁷Pb, respectively, in the reference material were in good agreement with corresponding ‘information only’ values of 1.176 ± 0.001, 2.092 ± 0.002 and 2.461 ± 0.003 reported in Yafa et al. (2004).

Statistics

Following the procedure described by Martínez Cortizas et al. (2013) and Hermanns and Biester (2013), we used factor analysis by principal component analysis (PCA) to identify sources and processes related to the distribution of the measured elements using the SPSS 20 software package. PCA of compositional data is usually undertaken on transformed variables (Baxter, 1995), particularly when the values cover several orders of magnitude and there are outliers (Baxter, 1999). Transformation also avoids any scaling effects (Eriksson et al., 1999). Thus, the PCA was done on log-transformed and standardized (z-scores) data, using varimax rotation to maximize the variance of the elements in the principal components (Eriksson et al., 1999). Similarly distributed elements will load on to the same principal component and are most likely to be controlled by the same environmental factor(s). Hence, interpretation of the signals with regard to the underlying cause or causes of variation of a group of elements should be more evident.

Results

Age–depth modelling

The results are shown in Table 1 with 2σ calibrated age ranges (in calibrated years bc/ad). A polynomial regression age–depth model is shown in Figure 2. All dates appearing in the following text are cited in calendar years bc/ad, unless otherwise stated, and are given within the 95% confidence intervals derived from the Calib 7.0 model (Reimer et al., 2009; Stuiver and Reimer, 1993), with end-points rounded to the nearest decade.

Table 1.

Radiocarbon dates from Toddle Moss.

Lab code	Sample	Depth (cm)	Uncalibrated age	Calibrated age range (2σ)
Poz-56748	Sphagnum leaves	102–103	1110 ± 30	Cal. ad 879–1013
Poz-19215	Peat	250–252	2530 ± 35	Cal. 797–539 bc
Beta-15142	Peat	345	3450 ± 50	Cal. 1890–1634 bc

Figure 2.

An age–depth model for Toddle Moss using Clam (after Blaauw, 2010).

Geochemistry

The calcium/magnesium ratio (Figure 3) is consistently below 1 and much lower than the measured value for rainwater (approximately 1.9) at Raeburn Flow, which is located approximately 74 km to the southeast of Toddle Moss (Küttner et al., 2014). These low values are sufficient to infer ombrotrophic conditions for the bog (cf. Shotyk, 1996). Notwithstanding a series of short-lived peaks, titanium concentrations remain relatively constant from the base of the profile to 101 cm. They then rise gradually with a sustained increase from 43 cm to the surface of the bog. Lead concentrations are generally low from the base of the core to 35 cm depth: thereafter, they increase dramatically to peak at 11 cm before decreasing to much lower concentrations at the bog surface. The Pb/Ti ratio follows a similar pattern. The ²⁰⁶Pb/²⁰⁷Pb profile shows more radiogenic ratios from 342 to 308 cm (SI Table 1, available online). A shift to less radiogenic values occurs between 308 and 222 cm (Figure 3). Thereafter, the ratios gradually rise from 222 to 24 cm before they become less radiogenic towards the bog surface.

Figure 3.

Calcium/magnesium ratio (by ICP-OES), titanium concentrations, lead concentrations (by EMMA; dashed line on a log scale), Pb/Ti ratio and ²⁰⁶Pb/²⁰⁷Pb ratios (by ICP-MS) from Toddle Moss.

Concentrations of arsenic, chromium, gallium, yttrium, zinc and zirconium, determined using EMMA, are shown in Figure 4. Arsenic, gallium and yttrium have similar trends to lead: low concentrations from the base of the core until 35 cm, a sharp rise to peak in the top 10 cm, followed by a decline to much lower concentrations. Zinc and chromium are characterized by low but highly fluctuating concentrations from the base of the core until approximately 80 cm. They also peak in the uppermost 10 cm with other elements. Chromium concentrations also decline close to the peat surface, but zinc remains relatively high. Zirconium concentrations are more erratic with a series of peaks throughout the profile (e.g. 265, 237, 179, 135, 113, 63, 33 and 17 cm) but show a gradual increase in the upper metre of the profile.

Figure 4.

Concentrations of lead, arsenic, gallium, yttrium, zinc and chromium as determined by EMMA.

PCA

Two components explain 78% of the total variance (Table 2). The first component (Cp1, 44% of the total variance) is characterized by large-to-moderate positive loadings of metals typically associated with mining/metallurgy (namely, arsenic, zinc, lead and chromium; Table 2). Gallium and yttrium, which are usually considered to be lithogenic elements, show large loadings in Cp1 (Table 2) and thus can also be associated with atmospheric metal pollution, probably derived from dust emissions during mining. This is also supported by the extremely high metal concentrations in the upper section of the peat, which are only comparable with those found close to pollution sources (e.g. in the Harz mountains, Germany, where Pb concentrations exceed 1000 µg/g during medieval times (Kempter and Frenzel, 2000) and equivalent to Pb concentrations determined within several kilometres of a lead smelter (Mihaljevič et al., 2006)). Cp1 scores show a typical record of atmospheric metal pollution, with a large peak in the upper 30 cm of the core and a sharp decrease in the upper 8 cm (Figure 5). It also shows two minor increases in scores during the early medieval period: between 120 and 140 cm (5th–7th centuries ad) and from 90 to 100 cm (9th–11th centuries ad).

Table 2.

Loadings of the variables in the components extracted by PCA on the chemical composition of the peat.

	Cp1	Cp2	Com		Cp1-PI	Cp2-PI	Cp3-PI	Com
As	0.93	0.27	0.95	Si	0.83	0.08	0.15	0.71
Ga	0.93	0.26	0.93	Ti	0.83	−0.18	0.03	0.72
Y	0.90	0.33	0.91	Al	0.79	0.04	0.21	0.67
Zn	0.82	0.05	0.67	Y	0.71	0.15	0.06	0.53
Pb	0.82	0.43	0.85	Zr	0.69	−0.16	0.06	0.51
Cr	0.51	0.35	0.38	Zn	−0.27	0.75	0.25	0.69
Ti	0.29	0.86	0.83	As	0.04	0.74	0.13	0.56
Si	0.35	0.85	0.83	Cr	0.44	0.59	−0.54	0.83
Al	0.15	0.84	0.73	Ga	0.16	0.18	0.83	0.74
Zr	0.21	0.80	0.69	Pb	0.43	0.23	0.67	0.69
Eigv	4.40	3.37		Eigv	3.45	1.63	1.58
Var	44.0	33.7		Var	34.5	16.3	15.8

Cp1 and Cp2: components extracted using the whole data set; Cp1-PI to Cp3-PI: components extracted using data for pre-industrial peat sections; Eigv: eigenvalues; Var: percentage of total variance; Com: communality (proportion of variance of each element explained by the two principal components); PCA: principal component analysis.

Figure 5.

Records of scores of the extracted principal components.

The second component (Cp2, 33.7% of the total variance) is characterized by large positive loadings of the lithogenic elements (Ti, Si, Al and Zr; Table 2). This chemical association reflects the mineral content of the peat because of deposition of dust, probably derived from soil erosion. The record of scores shows a ‘see-saw’ pattern, with eight peaks in dust deposition (Figure 5): at 265 cm (c. 870 cal. bc), 237 cm (c. 560 cal. bc), 179 cm (c. 70 cal. bc), 133 cm (c. ad 570), 109 cm (c. ad 835), 85 cm (c. ad 1095), 63 cm (c. ad 1335) and 33 cm (c. ad 1660). Although most of the variation in the concentrations of the metals is related to the first component (i.e. atmospheric metal pollution), a small proportion of the changes in lead, arsenic, gallium and yttrium are also correlated to Cp2 (Table 2), and therefore, they indicate a geogenic contribution.

Due to the expected large effect on the PCA of the metal concentrations of the peat sections with ages younger than ad 1600, we performed a second PCA using only the data for peat sections with pre-industrial ages (below 38 cm). In this data set, the first component, Cp1-PI, is characterized by the large loadings of the lithogenic elements (silicon, titanium, aluminium, yttrium and zirconium; Table 2). Cp1-PI and Cp2 scores are highly correlated (r = 0.97). Most of the yttrium variance is now in this component, suggesting that in Toddle Moss, its association with the metals associated with pollution occurs only after the start of the Industrial Revolution. This is not the case for gallium, whose variance is still loaded into a metal component (Table 2).

Moreover, in the second analysis, the metal signal is divided into two components: Cp2-PI with zinc, arsenic and chromium which has a record of scores similar to that of Cp2 (r = 0.68) and Cp3-PI with gallium and lead (Table 2). Thus, the metal signature of the peat for pre-industrial times seems to indicate that there were differences in the accumulation of the metals in Toddle Moss. The record of Cp2-PI scores suggests that the history of zinc, arsenic and chromium enrichment is quite similar during late prehistory and early Middle Ages. However, the elevated scores of Cp2-PI between 250 and 236 cm, corresponding to the period c. 700–550 cal. bc, are not paralleled by lead.

Interpretation and discussion

Lead is essentially immobile once it becomes incorporated into ombrotrophic peat (MacKenzie et al., 1997; Shotyk et al., 1997), and there is a plethora of studies that have demonstrated that the pattern of lead is faithfully preserved in peat bogs which can be reliably matched with other archaeological and historical documentary records (e.g. Mighall et al., 2002b; Shotyk et al., 1997). Lead concentrations, lead–titanium ratios and isotopic ratios are now regularly used to identify evidence of anthropogenic forcing on the lead biogeochemical cycle. Lead–titanium ratios are used to identify non-silicate sources of lead (Görres and Frenzel, 1997; Shotyk, 1996), whereas isotopic ratios are also considered to reflect accurately anthropogenic lead emissions especially when the isotopic signature of potential sources is well known (Martínez Cortizas et al., 2002). The record of lead derived from Toddle Moss presented here should therefore provide a reliable chronological record for past lead deposition onto the bog surface. Notwithstanding the numerous complicating variables that can influence the dispersion of gaseous and particulate pollution from source, bogs located close to industrial sites should provide robust records of emissions from these sites as pollutants are deposited onto the mire surface (Mighall et al., 2002a, 2002b).

Slightly elevated lead concentrations (Figure 3) might well be attributed to Middle–Late Bronze Age metallurgical activities: centring on 272 and 247 cm (c. 940 to 670 cal. bc) and higher Pb/Ti ratios between 270 and 247 cm (Figure 3). Although the concentrations recorded in the core are low, they are elevated above those recorded below 280 cm, and so, the trends described here may hint at the possibility of early lead working in the area. The discovery of a stone hammer at Wanlockhead (Pickin, 2008) is indicative of prehistoric mining. This particular stone hammer is very similar typologically to the grooved hammerstones found at the prehistoric copper mine at Alderley Edge (Timberlake and Prag, 2005), which are thought to have been used as crushing and pounding implements. There is no contextual evidence for the stone hammer found at Wanlockhead as it was discovered by a mine manager and the exact location is unknown. Perhaps, the strongest evidence for an early insular mining/metallurgical industry in Scotland is provided by the isotopic analysis of Early Bronze Age lead beads from Peeblesshire and West Water Reservoir in the Borders. The data indicate that a Scottish Southern uplands source – possibly Leadhills – was exploited (Hunter in Toolis, 2007; Hunter et al., 2006). Taken together, these separate strands of archaeological evidence are suggestive of activities possibly ranging from experimental exploitation on a small scale to more significant activity, which could have produced sufficient amounts of pollution to be recorded in the bog more widely, and such activity would have taken place during the Middle–Late Bronze Age when lead is found in bronze alloys. However, the introduction of lead into bronzes or other copper alloys is rare in northern Britain (Dungworth, 1996), and while it points towards a demand for lead, it does not provide convincing evidence of an early insular lead industry in southern Scotland. Indeed, lead is found in the St Andrews Hoard, but an analysis of the impurities in the artefacts suggests that some of the metals may have been re-worked or produced from different metal sources that might originate from outside Scotland (Cowie et al., 1998).

For purposes of comparison, the lead isotope ratios of the Toddle Moss peat samples are plotted in Figure 6 besides selected lead ores from other locations in the British Isles and the major Spanish mines of Rio Tinto and Murcia (Rohl, 1996; Stos-Gale et al., 1995). Lead isotopic signatures from Flanders Moss and Lindow Moss (cf. Cloy et al., 2005; Le Roux et al., 2004) fall within the cluster of British ores from the Mendips, Alderley Edge, NE Wales and the mines at Leadhills and Wanlockhead. Because of the overlap of the isotopic ratios, it is not possible to attribute the origin of this lead to a particular British ore source (cf. Cloy et al., 2005; Le Roux et al., 2004). Nevertheless, the results clearly show that the lead is likely to be of British origin, as the isotopic values for the British ores are clearly separable from those of the heavily exploited Spanish sources (Shotyk et al., 1998).

Figure 6.

Plot of ²⁰⁸Pb/²⁰⁶Pb versus ²⁰⁶Pb/²⁰⁷Pb ratios from samples from the Toddle Moss core and galena from various British and Spanish ores.

The peat samples from Toddle Moss of the section between 296 and 224 cm clearly fall outside all of the clusters shown in Figure 6. An analysis of galena samples from Wanlockhead has established the isotopic signature for lead ore at this location. Cloy et al. (2005) reported a ²⁰⁶Pb/²⁰⁷Pb ratio of 1.172 ± 0.003, which is in close agreement with a value of 1.170 ± 0.003 for the Leadhills and Wanlockhead lead ore reported by Sugden et al. (1993). Rohl (1996) calculated the mean ²⁰⁶Pb/²⁰⁷Pb ratio from five ore samples from Wanlockhead plus six from Leadhills as 1.171 ± 0.001. All these values plot within the ‘British ore’ cluster (Figure 6). This suggests that the source of lead determined within the Toddle Moss peat samples between 296 and 224 cm does not originate from the main galena bearing lodes from the Leadhills or Wanlockhead orefield. However, one sample of galena from Wanlockhead has a ²⁰⁶Pb/²⁰⁷Pb ratio of 1.142, and it is plotted in Figure 6 as the ‘Wanlockhead outlier’. This ratio is in much better agreement with the Toddle Moss samples between 296 and 224 cm. If early miners and metallurgists did exploit lead at Wanlockhead, then they appear to have targeted lodes bearing a similar lead isotopic signature.

A more extensive analysis of the isotopic signatures of the mineralized zones in the orefield could resolve the apparent signature discrepancies between the peat samples, the Wanlockhead ‘outlier’ and the other Leadhills ore samples. Whether the two distinct phases of lead formation at Leadhills resulted in the different isotopic signatures is unknown. The natural lead isotope composition of rocks depends upon the age of the lithogenic system, the U/Pb and Th/Pb ratios of the system and mixing during remobilization and metamorphism (Keinonen, 1992). During the formation of lead ore deposits, lead is separated from the parent uranium and thorium isotopes, with the lead isotopic composition of hydrothermal fluids being ‘frozen’ into lead-bearing minerals (Church et al., 1993). Thus, the isotopic composition of a given ore deposit is a function of four parameters: (1) the decay rate of parent isotopes, (2) the initial ratio of the abundance of the parent to the abundance of Pb (²³⁸Pb/²⁰⁴Pb, ²³²Th/²⁰⁴Pb) in the source reservoir (e.g. mantle or continental crust), (3) the initial isotopic composition of reservoir Pb and (4) the duration of reservoir evolution prior to separation of Pb by geological processes (Sangster et al., 2000).

A second phase of increasing lead enrichment and relatively higher Pb/Ti ratios at Toddle Moss occurs during the late Iron Age c. cal. 365 bc–ad 70 (between 219 and 179 cm; Figures 3, 4 and 7). Whether this represents pollution generated from local lead extraction or metallurgy is still contestable as there is a lack of local archaeological evidence. However, the shift in the ²⁰⁶Pb/²⁰⁷Pb ratio towards values close to those determined from Leadhills and the average value for atmospheric lead in Scotland in the 19th century ad provides evidence of industrial activity within the region at this time. While the initial rise of lead concentrations does correlate quite closely with the suggested age of the Carghidown promontory fort lead beads dated c. cal 360 bc–ad 60 (Toolis, 2007), these finds are exceptional. Hunter et al. (2006) suggest that circumstantial evidence, such as described earlier including at West Water Reservoir (see above), points to the use of lead sources in prehistory at Leadhills and Tonderghie in Dumfries and Galloway, but in general, there is very little evidence of native lead use in the Iron Age.

Figure 7.

Comparison of lead records from selected peat bogs in Scotland. (a) Leadhills lead concentrations and Pb/Ti ratio; dashed line represents exaggerated values down the profile (scale at base of the graph). (b) Raeburn Flow lead concentrations and lead enrichment factor. Enrichment factor is calculated using the equation proposed by Shotyk (1996). Titanium was used as the reference lithogenic element (from, and full details in, Küttner et al., 2014). Dashed lines represent exaggerated values down the profiles (scale at base of the graph). (c) Flanders Moss lead concentrations (from, and full details in, Cloy et al., 2005).

Shifts in the ²⁰⁶Pb/²⁰⁷Pb ratios and/or increased lead have been regularly recorded in peat profiles dated to the Late Iron and Roman times (De Vleeschouwer et al., 2010; Martínez Cortizas et al., 1997; Renberg et al., 2001). This includes sites in the British Isles: northwest and southwest England (Le Roux et al., 2004; Meharg et al., 2012), central Wales (Mighall et al., 2002b, 2009), at Flanders Moss in central Scotland (Cloy et al., 2005, 2008) and Raeburn Flow in southern Scotland (Küttner et al., 2014). The results suggest that British ores were exploited at least two centuries before the Roman occupation (Cloy et al., 2005) and that Roman exploitation always followed an earlier indigenous (British) lead extraction industry. The equivalent time frame at Toddle Moss is contained between approximately 182 and 148 cm (ad 40–410; Figure 3). Across this part of the core lead concentrations and Pb/Ti ratios remain low: this is rather unusual. Lead concentrations initially fall and then rise slightly between 150 and 160 cm before declining once again. This small peak may represent small scale, episodic mining/metallurgical activity towards the end of the Roman occupation of Britain, but a clear phase of enrichment is not observed in contrast to the one recorded during across the Iron Age and Roman transition in peat bog records elsewhere in Scotland and further afield (e.g. Küttner et al., 2014, and references previously cited; Figure 7b). Notwithstanding the coarse resolution of the isotope data, there is an increase in ²⁰⁶Pb/²⁰⁷Pb ratio from 1.154 ± 0.0006 at 182–184 cm (c. ad 25) to 1.175 ± 0.0021 at 158–160 cm (c. ad 280) (Figure 3), which is consistent with the mean ratio derived by Rohl (1996) from six galena samples from Leadhills and five from Wanlockhead. However, the low concentrations recorded in the Toddle Moss peat core also imply that local lead ores remained unexploited or that any such activity was small in scale and may have only generated a pollution signal that is below the level of detection using current methods. Moreover, there is a lack of any definitive local archaeological evidence for lead mining and metallurgy for this period.

The Roman occupation of Scotland was short and intermittent, spanning approximately 150 years between the late 1st century and early 3rd century ad, with actual occupation by the Roman army occurring over as few as 40 years (Breeze and Dobson, 1987). There is evidence that the Romans were present in the area around Toddle Moss as a Roman road – with associated forts and temporary camps – extended northwards from Carlisle up to Crawford (Fairhurst, 1955; Figure 1). The road passes the Elvanfoot valley which runs westwards to Leadhills and Wanlockhead. There was also a fortlet at Sanquhar to the southwest of Leadhills and Wanlockhead. Such a transient occupation may not have allowed or encouraged the development of any large scale mining operation although both Wilson and Flett (1921) and MacDonald et al. (2005) have suggested that lead extraction may have occurred during Roman times. If the gradual rise in lead concentrations between 219 and 176 cm at Toddle Moss does indicate the existence of a local Iron Age lead extraction industry at Leadhills or Wanlockhead, another unknown factor possibly acted as a disincentive to further, more expansive Roman exploitation. The rarity of silver in Scotland and northern Britain lead ores may have depreciated its importance. This is in contrast with the record from Raeburn Flow, approximately 74 km to the southeast, and at Flanders Moss to the north, where small but more discernible lead contamination occurred during the pre-Roman and early part of the Roman period (Cloy et al., 2005; Küttner et al., 2014) (Figure 7b and c). However, Raeburn Flow is much closer to the Northern Pennine orefield, the lead and zinc mines in the Caldbeck fells and Carlisle, where there is evidence for lead smelting: all of which could have been pollution sources (Murphy, 2011). While lead artefacts have been found in both native and Roman contexts during the Roman Iron Age in Scotland, and although the finds suggest some interaction between the Romans and natives, it is still unclear where the objects originated from and who manufactured them (e.g. Hunter, 1996).

Martínez Cortizas et al. (2013) note that records from mires, lakes and lagoons do not always show metal enrichment during the Late Iron Age and Roman period. For example, some studies, such as those from southern France (Labonne et al., 1998), the Eifel area and Ireland (Schettler and Romer, 2006) do not show any evidence of contamination during the Iron Age while mires from Bavaria (Küster and Rehfuess, 1997), central and southeastern France (Baron et al., 2005; Monna et al., 2004) also show no metal enrichment during the Roman period. The Toddle Moss record provides additional evidence for specific regional variations in the evolution of mining and metallurgy during prehistoric and Roman times across Europe (cf. Martínez Cortizas et al., 2013).

The results suggest that phases of enhanced chromium accumulation occurred between 191 and 161 cm (c. 60 cal. bc–ad 225) and from 135 to 79 cm (c. ad 550–1150) Chromium was first discovered in the 18th century, so it is unlikely to have been intentionally exploited until then (Jacobs and Testa, 2005). Its occurrence in the Toddle Moss record is possibly as a by-product of mining, although lead concentrations were low at this time, suggesting that little or no mining took place locally, or it is deposited as dust produced from wider land-use changes as a proportion of the changes in chromium is also correlated to Cp2 indicating a geogenic contribution. Chromium is relatively enriched in bedrock regionally (MacDonald et al., 2005).

Despite the low concentrations, the lead record between ad 400 and 1610 appears to document the rise of the extraction and metalworking industry. The ²⁰⁶Pb/²⁰⁷Pb ratios initially drop to 1.163 ± 0.0010 at 126–128 cm (c. ad 655) but then return to more radiogenic values thereafter: values of 1.17 and 1.18 from 112 (c. ad 800) to 25 cm (c. ad 1750) (Figure 5) are consistent with the isotopic values determined for galena at both Leadhills and Wanlockhead. The pollution component identified by PCA (Cp1) shows three peaks in the period ad 400–1610, supported by increased lead concentrations and Pb/Ti ratios, pointing to small-scale mining/metallurgical activity at Leadhills/Wanlockhead during the 5th–7th and 9th–11th centuries ad (Figures 3, 4 and 6). The first peak occurs at 133 cm (c. ad 572), with a short-lived peak in Cp1 and Cp1-PI cores, lead concentrations and Pb/Ti ratio. Lead shows a sustained rise after c. ad 900 (103 cm) as the ²⁰⁶Pb/²⁰⁷Pb ratio increases to 1.173 ± 0.0010 (106–108 cm, c. ad 855). Lead peaks at 93 cm (c. ad 1010) along with a peak in the Pb/Ti ratio subsequently fall (to 85 cm) before increasing again to 65 cm (c. ad 1310). Charcoal, taken from a lead slag scatter at Glennkip in the Leadhills, has been radiocarbon dated to the early 11th century ad, while smelting sites date to the late 10th and 11th centuries at Manor Valley (Pickin, 2010). While the first record for lead mining in the Leadhills district is provided by the Monks of Newbattle dated to ad 1239 (Wilson and Flett, 1921), the series of small but discernible peaks occur throughout the early medieval period.

After ad 1310, there is a gradual decrease in the Toddle Moss lead concentrations. This trend continues up the core to 50 cm (c. ad 1475). This coincides with the timing of the Anglo-Scottish war, a period for which there are no documentary accounts of lead mining in Leadhills/Wanlockhead. Written records recommence from ad 1466. After this date, the lead concentrations in the peat slowly begin to rise, possibly in response to the establishment of post-medieval smelting mills in the upper reaches of Glengonnar and Wanlockhead Water (Pickin, 2010).

Lead, arsenic, chromium and zinc concentrations all increase above 38 cm (c. ad 1610) (Figures 3 and 4). The expansion in lead mines at Leadhills and Wanlockhead is well documented for the 17th century, with peak activity occurring between ad 1850 and 1920. Through this part of the peat record (24 cm and above), the ²⁰⁶Pb/²⁰⁷Pb ratio generally falls within the range 1.17–1.18. This range is consistent with the isotopic signature of indigenous lead ore smelting from Leadhills and Wanlockhead (Figure 6) and coal combustion (²⁰⁶Pb/²⁰⁷Pb ratio of 1.181) as recorded elsewhere in Scotland (e.g. Cloy et al., 2005; Farmer et al., 2005). A double peak in lead concentrations, dated to the latter part of the 18th and late 19th/early 20th centuries, respectively, is shown. The date of the uppermost peak is consistent with total lead concentrations measured in a channel bank in Glengonnar Water and average production figures from Leadhills (Rowan et al., 1995).

Increased concentrations of zinc, arsenic and, to a lesser extent, gallium are most likely to be associated with lead mining, coal combustion (Oremland and Stolz, 2003; Rothwell et al., 2009; Shotyk et al., 1996) and/or plant uptake (Zaccone et al., 2008). Coal was used as fuel for lead smelting from ad 1727, and small amounts of copper and zinc were also extracted locally (Wilson and Flett, 1921). Chromium is also used as an alloy in steel making (Jacobs and Testa, 2005).

The marked reduction of lead, arsenic, chromium and gallium concentrations in the top 10 cm reflects the demise of the Leadhills and Wanlockhead mines in the 1930s and the subsequent phasing out of leaded gasoline. Less radiogenic ²⁰⁶Pb/²⁰⁷Pb ratios once again fall close to the isotopic ratio of the Wanlockhead outlier (Figure 6).

These values reflect a change in the source of the lead deposited onto the bog, with the final closure of the mines and the loss of the main Leadhills isotopic signature, the increasing influence of imported Australian lead (²⁰⁶Pb/²⁰⁷Pb ratio = 1.04) and other alkyl lead additives in petrol which are also phased out in the recent past. These sources would dilute any remnant lead deposition from the Leadhills galena ores. These trends are commonly recorded in bogs across the British Isles (e.g. Cloy et al., 2008; Farmer et al., 1997; Le Roux et al., 2004; Mighall et al., 2002b, 2004, 2009; West et al., 1997). The acrotelm is also affected by ongoing peat forming processes such as decomposition, plant uptake/recycling, element mobility and fluctuations at the acrotelm/catotelm transition (e.g. Martínez Cortizas et al., 2007). These processes may also have played a role in influencing the distribution of elements through the peat such as zinc (Biester et al., 2012; Espi et al., 1997; Jones, 1987; Shotyk, 1988).

Conclusion

The Toddle Moss record provides evidence of three major phases of atmospheric metal contamination which accord well with historical and archaeological records of mining and metallurgy from medieval times to present: 5th–7th centuries ad, 9th–11th centuries ad and the latter part of the 18th and late 19th/early 20th centuries, respectively. No evidence of major Roman activity was discovered, which provides further evidence for specific regional variations in the evolution of mining and metallurgy and an associated contamination signal in Roman times across Europe.

Patterns of lead might reflect earlier activity during the Bronze and Iron Ages, but further analysis will be required to confirm whether the Leadhills/Wanlockhead was an early source of metals as part of an insular metal mining industry.

Footnotes

Acknowledgements

Thanks to Nathan Pittam, Claire Devonport and Alice Humphries for help with fieldwork. We thank Joanna Cloy and John Farmer for provision of lead isotope data and for helpful comments. Jason Jordan prepared some of the material for analysis. Thanks to David Cranstone for information about lead sources. We thank Alison Sandison and Jenny Johnson at the University of Aberdeen for cartographical support. Peter Gayford (Hopetoun Estates) and James C. E. Hodge kindly gave permission to take a core from Toddle Moss. We would like to thank the two anonymous reviewers for their considered and useful comments.

Funding

Coventry University and Society of Antiquaries of Scotland kindly provided funding for this research.

References

Appleby

(2001) Chronostratigraphic techniques in recent sediments. In: Last

Smol

(eds) Tracking Environmental Change Using Lake sediments. Volume 1: Basin Analysis, Coring and Chronological Techniques. Dordrecht: Kluwer, pp. 171–204.

Appleby

Oldfield

(1978) The calculation of Pb-210 dates assuming a constant rate of supply of unsupported Pb-210 to the sediment. Catena 5: 1–8.

Appleby

Nolan

Oldfield

. (1988) ²¹⁰Pb dating of lake sediments and ombrotrophic peats by gamma essay. Science of the Total Environment 69: 157–177.

Barber

(2003) Bronze and the Bronze Age. London: Tempus.

Baron

Lavoie

Ploquin

. (2005) Record of metal workshops in peat deposits: History and environmental impact on the Mont Lozère Massif, France. Environmental Science and Technology 39: 5131–5140.

Baxter

(1995) Standardization and transformation in principal component analysis, with applications to archaeometry. Applied Statistics 44: 513–527.

Baxter

(1999) Detecting multivariate outliers in artefact compositional data. Archaeometry 41: 321–338.

Bick

(1999) Bronze Age copper mining in Wales – Fact or fantasy? Historical Metallurgy 33: 7–12.

Biester

Hermanns

Y-M

Martínez Cortizas

(2012) The influence of organic matter decay on the distribution of major and trace elements in ombrotrophic mires – A case study from the Harz Mountains. Geochimica Cosmochimica Acta 84: 126–136.

10.

Blaauw

(2010) Methods and code for ‘classical’ age-modelling of radiocarbon sequences. Quaternary Geochronology 5: 512–518.

11.

Breeze

Dobson

(1987) Hadrian’s Wall. London: Pelican.

12.

Chapman

Leake

(2005) Evidence for the historical exploitation of possible bedrock gold in the upper Mennock Water, Wanlockhead, Dumfries and Galloway. Scottish Journal of Geology 41: 135–140.

13.

Cheburkin

Shotyk

(1996) An energy-dispersive miniprobe multi-element analyzer (EMMA) for direct analysis of Pb and other trace elements in peats. Fresenius Journal of Analytical Chemistry 354: 688–691.

14.

Church

Holmes

Briggs

. (1993) Geochemical and lead-isotope data from stream and lake sediments, and cores from the upper Arkansas River drainage: Effects of the mining at Leadville, Colorado on heavy-metal concentrations in the Arkansas River. USGS Open-file Report, No. 93–534. Denver, CO: US Geological Survey.

15.

Cloy

Farmer

Graham

. (2005) A comparison of antimony and lead profiles over the past 2500 years in Flanders Moss ombrotrophic peat bog, Scotland. Journal of Environmental Monitoring 7: 1137–1147.

16.

Cloy

Farmer

Graham

. (2008) Historical records of atmospheric Pb deposition in four Scottish ombrotrophic peat bogs: An isotopic comparison with other records from Western Europe and Greenland. Global Biogeochemical Cycles 22: GB2016. DOI: 10.1029/2007GB003059.

17.

Cowie

Northover

O’Connor

(1998) The St Andrews, Fife, Hoard: Context and chronology in the Scottish Late Bronze Age. In: Mordant

Pernot

Rychner

(eds) L’Atelier du bronzier en Europe du XXe au VIIIe siècle avant notre ére. Actes du colloque international Bronze’96, Neuchâtel et Dijon III: Production, circulation et consummation du bronze. Paris: CTHS, pp. 141–154.

18.

De Vleeschouwer

Le Roux

Shotyk

(2010) Peat as an archive of atmospheric contamination and environmental change: A case study of lead in Europe. PAGES 18: 20–22.

19.

Dungworth

(1996) The production of copper alloys in Iron Age Britain. Proceedings of the Prehistoric Society 62: 399–421.

20.

Ebdon

Evans

Fisher

. (1998) An Introduction to Analytical Atomic Spectrometry. Chichester: Wiley.

21.

Eriksson

Johansson

Kettaneh-Wodl

. (1999) Introduction to Multi- and Mega-Variate Data Analysis Using Projection Methods (PCA & PLS). Umea: Umetrics AB.

22.

Espi

Boutron

Hong

. (1997) Changing concentrations of Cu, Zn, Cd and Pb in a high altitude peat bog from Bolivia during the past three centuries. Water Air and Soil Pollution 100: 289–296.

23.

Fairhurst

(1955) The roads of Scotland. 1. Roman roads. Scottish Geographical Magazine 71: 77–82.

24.

Farmer

Eades

Graham

. (2000) The changing nature of the ²⁰⁶Pb/²⁰⁷Pb isotopic ratio of Pb in rainwater, atmospheric particulates, pine needles and leaded petrol in Scotland, 1982–1998. Journal of Environmental Monitoring 2: 49–57.

25.

Farmer

Graham

Bacon

. (2005) Isotopic characterisation of the historical lead deposition record at Glensaugh, an organic-rich, upland catchment in rural N.E. Scotland. Science of the Total Environment 346: 121–137.

26.

Farmer

Mackenzie

Sugden

. (1997) A comparison of the historical lead contamination records in peat and freshwater lake sediments in central Scotland. Water Air and Soil Pollution 100: 253–270.

27.

Fifield

Kealey

(2000) Principles and Practices of Analytical Chemistry. London: Blackwell Science.

28.

Görres

Frenzel

(1997) Ash and metal concentrations in peat bogs as indicators of human activity. Water Air and Soil Pollution 100: 355–365.

29.

Hermanns

Biester

(2013) A 17,300-year record of mercury accumulation in a pristine lake in southern Chile. Journal of Paleolimnology 49: 1–15.

30.

Holler

Skoog

West

(1996) Fundamentals of Analytical Chemistry. 7th Edition. Philadelphia, PA: Saunders College Publishing.

31.

Hong

Candelone

J-P

Patterson

. (1994) Greenland Ice evidence of hemispheric lead pollution two millennia ago by Greek and Roman Civilisations. Science 265: 1841–1843.

32.

Hunter

(1996) Recent Roman Iron age metalwork finds from Fife and Tayside. Tayside and Fife Archaeological Journal 2: 113–125.

33.

Hunter

Davis

(1994) Early Bronze Age lead – A unique necklace from southeast Scotland. Antiquity 68: 824–830.

34.

Hunter

Cowie

Heald

(2006) Research priorities for archaeometallurgy in Scotland. Scottish Archaeological Journal 28: 49–62.

35.

Jacobs

Testa

(2005) Overview of chromium (VI) in the environment: Background and history. In: Guertin

Jacobs

Avakian

(eds) Chromium (VI) Handbook. Boca Raton: CRC Press, pp. 1–21.

36.

Jones

(1987) Chemical fractionation of copper, lead and zinc in ombrotrophic peat. Environmental Pollution 48: 131–144.

37.

Keinonen

(1992) The isotopic composition of lead in man and the environment in Finland 1966–1987 – Isotope ratios of lead as indicators of pollutant source. Science of the Total Environment 113: 51–268.

38.

Kempter

Frenzel

(2000) The impact of early mining and smelting on the local tropospheric aerosol detected in ombrotrophic peat bogs in the Harz, Germany. Water Air and Soil Pollution 121: 93–108.

39.

Küster

Rehfuess

K-E

(1997) Pb and Zn concentrations in a southern Bavarian bog profile and the history of vegetation as recorded by pollen analysis. Water Air and Soil Pollution 100: 379–386.

40.

Küttner

Mighall

De Vleeschouwer

. (2014) A record of trace metal contamination as recorded by a raised bog from south west Scotland. Journal of Archaeological Science 44: 1–11.

41.

Labonne

Othman

Luck

J-M

(1998) Recent and past anthropogenic impact on a Mediterranean lagoon: Lead isotope constraints from mussel shells. Applied Geochemistry 13: 885–892.

42.

Le Roux

Weiss

Grattan

. (2004) Identifying the sources and timing of ancient and medieval atmospheric lead pollution in England using a peat profile from Lindow Bog, Manchester. Journal of Environmental Monitoring 6: 502–510.

43.

MacDonald

Fordyce

Shand

. (2005) Using geological and geochemical information to estimate the potential distribution of trace elements in Scottish groundwater. Groundwater Programme Commissioned Report CR/05/238N. Nottingham: British Geological Survey.

44.

MacKenzie

Farmer

Sugden

(1997) Isotopic evidence of the relative retention and mobility of lead and radiocaesium in Scottish ombrotrophic peats. Science of the Total Environment 203: 115–127.

45.

Martínez Cortizas

Biester

Mighall

. (2007) Climate-driven enrichment of pollutants in peatlands. Biogeosciences 4: 905–911.

46.

Martínez Cortizas

Garćia-Rodeja Gayoso

Weiss

(2002) Peat bog archives of atmospheric metal deposition. Science of the Total Environment 292: 1–5.

47.

Martínez Cortizas

López Merino

Bindler

. (2013) Atmospheric contamination in Northern Spain in late Iron Age/Roman times reconstructed using the high-resolution record of La Molinia (Asturias). Journal of Palaeolimnology 50: 71–86.

48.

Martínez Cortizas

Pontevedra-Pombal

Nóvoa-Muños

. (1997) Four thousand years of atmospheric Pb, Cd and Zn deposition recorded by the ombrotrophic peat bog of PenidoVello. Water Air and Soil Pollution 100: 387–403.

49.

Meharg

Edwards

Schofield

. (2012) First comprehensive peat depositional records for tin, lead and copper associated with the antiquity of Europe’s largest cassiterite deposits. Journal of Archaeological Science 39: 717–727.

50.

Mighall

Abrahams

Grattan

. (2002a) Geochemical evidence for atmospheric contamination derived from prehistoric copper mining at Copa Hill, Cwmystwyth, mid-Wales. Science of the Total Environment 292: 69–80.

51.

Mighall

Dumayne-Peaty

Cranstone

(2004) A record of atmospheric contamination and vegetation change as recorded in three peat bogs from the Northern Pennines Pb-Zn orefield. Environmental Archaeology 9: 13–38.

52.

Mighall

Grattan

Lees

. (2002b) An atmospheric contamination history for Pb-Zn mining in the Ystwyth Valley, Dyfed, mid-Wales, UK. Geochemistry: Exploration, Environment, Analysis 2: 175–184.

53.

Mighall

Timberlake

Foster

IDL

. (2009) Ancient copper and lead contamination records from a raised bog complex in Central Wales, UK. Journal of Archaeological Science 36: 1504–1515.

54.

Mihaljevič

Zuna

Ettler

. (2006) Lead fluxes, isotopic and concentrations profiles in a peat deposit near a lead smelter (Příbram, Czech Republic). Science of the Total Environment 372: 334–344.

55.

Monna

Petit

Guillaumet

J-P

. (2004) History and Environmental impact of mining activity in Celtic Aeduan territory recorded in a peat bog (Morvan, France). Environ Science and Technology 38: 665–673.

56.

Murphy

(2011) Evidence for metalworking processes. In: Newman

(ed.) Carlisle: Excavations at Rickergate, 1998-9 and 53-55 Botchergate, 2001. Cumbria Archaeological Reports No 2. Carlisle: Cumberland & Westmorland Antiquarian & Archaeological Society, pp. 108–113.

57.

Needham

Hook

(1988) Lead and lead alloys in the Bronze Age. In: Slater

Tate

(eds) Science and Archaeology, Glasgow, 1987. Oxford: British Archaeological Reports 196, pp. 259–274.

58.

Nilsson

Klarqvist

Bohlin

. (2001) Variation in ¹⁴C age of macrofossils and different fractions of minute peat samples dated by AMS. Holocene 11: 579–586.

59.

Nriagu

(1983) Lead and Lead Poisoning in Antiquity. New York: Wiley.

60.

Nriagu

(1996) A history of global metal pollution. Science 272: 223–224.

61.

Nriagu

(1998) Tales told in lead. Science 281: 1622–1623.

62.

Oremland

Stolz

(2003) The ecology of arsenic. Science 300: 939–944.

63.

Pattrick

RAD

Polkya

(1993) Mineralisation in the British Isles. London: Chapman and Hall.

64.

Pickin

(2008) A grooved stone tool from Wanlockhead – Loom weight or prehistoric mining hammer? Transactions of the Dumfriesshire and Galloway Natural History and Antiquarian Society 82: 141–144.

65.

Pickin

(2010) Early lead smelting in southern Scotland. Historical Metallurgy 44: 81–84.

66.

Piotrowska

Blaauw

Mauquoy

. (2011) Constructing deposition chronologies for peat deposits using radiocarbon dating. Mires and Peat 7: 1–14.

67.

Rafferty

(1961) National Museum of Ireland archaeological acquisitions in 1959. Journal of the Royal Society of the Antiquaries of Ireland 91: 43–107.

68.

Reimer

Baillie

MGL

Bard

. (2009) Quaternary Isotope Laboratory, Radiocarbon Calibration Program, University of Washington. Available at: http://radiocarbon.pa.qub.ac.uk/calib/calib.html.

69.

Renberg

Bindler

Brännvall

M-L

(2001) Using the historical lead-deposition record as a chronological marker in sediment deposits in Europe. Holocene 11: 511–516.

70.

Rohl

(1996) Lead isotope data from the isotrace laboratory, Oxford: Archaeometry data base 2, Galena from Britain and Ireland. Archaeometry 38: 165–180.

71.

Rohl

Needham

(1998) The Circulation of Metals in the British Bronze Age: The Application of Lead Isotope Analysis (Occasional Paper 102). London: British Museum Press, 234 pp.

72.

Rothwell

Taylor

Ander

. (2009) Arsenic retention and release in ombrotrophic peatlands. Science of the Total Environment 407: 1405–1417.

73.

Rowan

Barnes

SJA

Hetherington

. (1995) Geomorphology and pollution: The environmental impacts of lead mining, Leadhills, Scotland. Journal of Geochemical Exploration 52: 57–65.

74.

Sangster

Outridge

Davis

(2000) Stable lead isotope characteristics of lead ore deposits of environmental significance. Environmental Reviews 8: 115–147.

75.

Schettler

Romer

(2006) Atmospheric Pb-contamination by pre-medieval mining detected in the sediments of the brackish karst lake An Loch Mór, western Ireland. Applied Geochemistry 21: 58–82.

76.

Shell

(1979) The early exploitation of tin deposits in SW England. In: Ryan

(ed.) The Origins of Metallurgy in Atlantic Europe. Dublin: The Stationery Office, pp. 251–263.

77.

Shotyk

(1988) Review of the inorganic geochemistry of peats and peatland waters. Earth Science Reviews 25: 95–176.

78.

Shotyk

(1996) Peat bog archives of atmospheric metal deposition: Geochemical evaluation of peat profiles, natural variations in metal concentrations, and metal enrichment factors. Environmental Reviews 4: 149–183.

79.

Shotyk

Cherburkin

Appleby

. (1996) Two thousand years of atmospheric arsenic, antimony and lead deposition recorded in an ombrotrophic peat bog profile, Jura Mountain, Switzerland. Earth and Planetary Science Letters 145: E1–E7.

80.

Shotyk

Norton

Farmer

(1997) Summary of the workshop on peat bog archives of atmospheric metal deposition. Water Air and Soil Pollution 100: 213–219.

81.

Shotyk

Weiss

Appleby

. (1998) History of atmospheric lead deposition since 12,370 ¹⁴C yr BP from a peat bog, Jura Mountains, Switzerland. Science 281: 1635–1640.

82.

Stos-Gale

Gale

Houghton

. (1995) Lead isotope data from the isotrace laboratory, Oxford: Archaeometry data base 1, ores from the western Mediterranean. Archaeometry 37: 407–415.

83.

Stuiver

Reimer

(1993) Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35: 215–230.

84.

Sugden

Farmer

MacKenzie

(1993) Isotopic ratios of lead in contemporary environmental material from Scotland. Environmental Geochemistry and Health 15: 59–65.

85.

Timberlake

(2003) Excavations on Copa Hill, Cwmystwyth (1986-1999). BAR British Series 348. Oxford: Archeopress, 127 pp.

86.

Timberlake

(2009) The origins of metal mining in Britain. In: Linton

(ed.) The Lode of History. Llanaber: The Welsh Mines Society, pp. 3–16.

87.

Timberlake

Prag

AJNW

(2005) The Archaeology of Alderley Edge. British Archaeological Report 396. Oxford: John and Erica Hedge Ltd. 309 pp.

88.

Timberlake

Mighall

Kidd

(in press) New evidence of Roman mining in Britain. In: Wilson

Bowman

(eds) Mining, Metal Supply and Coinage in the Roman Empire. Oxford: Oxford University Press.

89.

Toolis

with contributions from Duffy

Engl

Evans

. (2007) Intermittent occupation and forced abandonment of an Iron Age promontory fort at Carghidown, Dumfries and Galloway. Proceedings of the Society of Antiquaries of Scotland 137: 265–318.

90.

Tylecote

(1986) The Prehistory of Metallurgy in the British Isles. London: Institute of Metals.

91.

Wallbrink

Walling

(2002) Radionuclide measurement using Hpge Gamma Spectrometry. In: Zapata

(ed.) Handbook for the Assessment of Soil Erosion and Sedimentation Using Environmental Radionuclides. Dordrecht: Kluwer, pp. 67–96.

92.

Walling

Appleby

(2002) Conversion models for soil-erosion, soil-redistribution and sedimentation investigations. In Zapata

(ed.) Handbook for the Assessment of Soil Erosion and Sedimentation Using Environmental Radionuclides. Dordrecht: Kluwer, pp 111–164.

93.

Weiss

Shotyk

(1998) Determination of Pb in ashed peat plants using an energy-dispersive miniprobe multi-element analyzer (EMMA). Analyst 123: 2097–2102.

94.

West

Charman

Grattan

. (1997) Heavy metals in Holocene peats from south west England: Detecting mining impacts and atmospheric contamination. Water Air and Soil Pollution 100: 343–353.

95.

Wilson

Flett

(1921) The lead, zinc, copper and nickel ores of Scotland. Special reports on the mineral resources of Great Britain (Memoirs of the Geological Survey, Scotland). Edinburgh: HMSO.

96.

Yafa

Farmer

(2006) A comparative study of acid-extractable and total digestion methods for the determination of inorganic elements in peat material by inductively coupled plasma-optical emission spectrometry. Analytica Chimica Acta 557: 296–303.

97.

Yafa

Farmer

Graham

. (2004) Development of an ombrotrophic peat bog (low ash) reference material for the determination of elemental concentrations. Journal of Environmental Monitoring 6: 493–501.

98.

Zaccone

Cocozza

Cheburkin

. (2008) Distribution of As, Cr, Ni, Rb, Ti and Zr between peat and its humic fraction along an undisturbed ombrotrophic bog profile (NW Switzerland). Applied Geochemistry 23: 25–33.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.01 MB