Tim M. Mighall

Evidence for Mediaeval soil erosion in the South Hams region of Devon, UK:

A major theme of research into the causes of past and present soil erosion has been to determine the relative importance of climate and land-use change in influencing Holocene erosion rates. Previous work suggests that land-use change, especially the conversion of woodlands into agricultural land, is the main factor influencing long-term increases in soil erosion. A study of an extensive minerogenic sediment deposit in a wetland at Slapton Ley in Devon suggests that agricultural intensification occurred before the onset of sedimentation (a silty-clay layer c. 40 cm thick) in the valley-bottom wetland of the Slapton Sewage Works marsh. The base of the silty-clay layer lies at an altitude of between 2.2 and 2.6 m AOD and has been radiocarbon dated at two locations. Conventional radiocarbon ages (± 2 σ) were 910 ± 160 yr and 960 ± 140 yr BP. Successful radiocarbon dating of the upper surface of this minerogenic layer at one location yielded a conventional radiocarbon age of 730 ± 120 yr BP. Within the errors associated with radiocarbon dating, the onset of sedimentation appears to be associated with a period of climatic deterioration towards the end of the Mediaeval Climatic Optimum. While agriculture plays an important role in exposing unprotected soil at certain times of the year, an increase in the magnitude and frequency of wet and severe winters may have led to a substantial increase in the risk of erosion. Contemporary analogues serve to illustrate the complex relationships which may exist between agricultural practices, climate and weather conditions and to explain why erosion is often localized and episodic in nature.

Early atmospheric metal pollution provides evidence for Chalcolithic/Bronze Age mining and metallurgy in Southwestern Europe

Although archaeological research suggests that mining/metallurgy already started in the Chalcolithic (3rd millennium BC), the earliest atmospheric metal pollution in SW Europe has thus far been dated to ~3500-3200 cal.yr. BP in paleo-environmental archives. A low intensity, non-extensive mining/metallurgy and the lack of appropriately located archives may be responsible for this mismatch. We have analysed the older section (>2100 cal.yr. BP) of a peat record from La Molina (Asturias, Spain), a mire located in the proximity (35-100 km) of mines which were exploited in the Chalcolithic/Bronze Age, with the aim of assessing evidence of this early mining/metallurgy. Analyses included the determination of C as a proxy for organic matter content, lithogenic elements (Si, Al, Ti) as markers of mineral matter, and trace metals (Cr, Cu, Zn, Pb) and stable Pb isotopes as tracers of atmospheric metal pollution. From ~8000 to ~4980 cal.yr. BP the Pb composition is similar to that of the underlying sediments (Pb 15 ± 4 μg g(-1); (206)Pb/(207)Pb 1.204 ± 0.002). A sustained period of low (206)Pb/(207)Pb ratios occurred from ~4980 to ~2470 cal.yr. BP, which can be divided into four phases: Chalcolithic (~4980-3700 cal.yr. BP), (206)Pb/(207)Pb ratios decline to 1.175 and Pb/Al ratios increase; Early Bronze Age (~3700-3500 cal.yr. BP), (206)Pb/(207)Pb increase to 1.192 and metal/Al ratios remain stable; Late Bronze Age (~3500-2800 cal.yr. BP), (206)Pb/(207)Pb decline to their lowest values (1.167) while Pb/Al and Zn/Al increase; and Early Iron Age (~2800-2470 cal.yr. BP), (206)Pb/(207)Pb increase to 1.186, most metal/Al ratios decrease but Zn/Al shows a peak. At the beginning of the Late Iron Age, (206)Pb/(207)Pb ratios and metal enrichments show a rapid return to pre-anthropogenic values. These results provide evidence of regional/local atmospheric metal pollution triggered by the earliest phases of mining/metallurgy in the area, and reconcile paleo-environmental and archaeological records.

Anthropogenic Forcings on the Surficial Osmium Cycle

Osmium is among the least abundant elements in the Earths continental crust. Recent anthropogenic Os contamination of the environment from mining and smelting activities, automotive catalytic converter use, and hospital discharges has been documented. Here we present evidence for anthropogenic overprinting of the natural Os cycle using a ca. 7000-year record of atmospheric Os deposition and isotopic composition from an ombrotrophic peat bog in NW Spain. Preanthropogenic Os accumulation in this area is 0.10 +/- 0.04 ng m(-2) y(-1). The oldest strata showing human influence correspond to early metal mining and processing on the Iberian Peninsula (ca. 4700-2500 cal. BP). Elevated Os accumulation rates are found thereafter with a local maximum of 1.1 ng m(-2) y(-1) during the Roman occupation of the Iberian Peninsula (ca. 1930 cal. BP) and a further increase starting in 1750 AD with Os accumulation reaching 30 ng m(-2) y(-1) in the most recent samples. Osmium isotopic composition ((187)Os/(188)Os) indicates that recent elevated Os accumulation results from increased input of unradiogenic Os from industrial and automotive sources as well as from enhanced deposition of radiogenic Os through increased fossil fuel combustion and soil erosion. We posit that the rapid increase in catalyst-equipped vehicles, increased fossil fuel combustion, and changes in land-use make the changes observed in NW Spain globally relevant.

Influence of climate change and human activities on the organic and inorganic composition of peat during the ‘Little Ice Age’ (El Payo mire, W Spain):

The study of environmental change during the ‘Little Ice Age’ (‘LIA’) offers a great potential to improve our current understanding of the climate system and human–environment interactions. Here, a high-resolution multiproxy investigation of a Mediterranean mire from central-western Spain, covering the last ~700 years, was used to reconstruct peat dynamics and land-use change and to gain further insights into their relationship with ‘LIA’ climate (temperature and moisture). To accomplish this, concentrations and accumulation rates of major and minor lithogenic (Si, K, Ti, Rb and Zr) and biophilic (C and N) elements, as well as humification indices (UV-absorbance and Fourier-transform infrared spectroscopy (FTIR)) and pollen and non-pollen palynomorphs, were determined. Peatland dynamics seems to have been coupled to changes in solar irradiance and hydrological conditions. Our results point to wetter conditions after the mid-16th century, although with high intra-annual fluctuations. At the late 18th century, when solar activity was systematically higher than before, peat carbon accumulation rates (PCAR) showed a continuous increase and the humification indices suggest a change towards more humified peat. Enhanced soil erosion occurred at ~AD 1660–1800 (SE1), ~AD 1830–1920 (SE2) and ~AD 1940–1970 (SE3), although a minor increase in Si fluxes was also detected by ~AD 1460–1580. All phases coincided with higher abundances of fire indicators, but the changes recorded during the ~AD 1460–1580 event and SE1 coincide with the Spörer and Maunder minima, so a climatic influence on soil erosion cannot be discounted. Changes in the sources of mineral matter to the catchment between ~AD 1550 and ~AD 1650 and since the mid-17th century were likely related to modifications of tree cover and/or variations in wind strength.

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

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.

Industrial-era lead and mercury contamination in southern Greenland implicates North American sources

To study the long-range transport of atmospheric pollutants from lower latitude industrial areas to the Arctic, we analysed a peat core spanning the last ~700cal.yr (~1300-2000CE) from southern Greenland, an area sensitive to atmospheric pollution from North American and Eurasian sources. A previous investigation conducted in the same location recorded atmospheric lead (Pb) pollution after ~1845, with peak values recorded in the 1970s, and concluded that a North American source was most likely. To confirm the origin of the lead, we present new Pb isotope data from Sandhavn, together with a high-resolution record for mercury (Hg) deposition. Results demonstrate that the mercury accumulation rate has steadily increased since the beginning of the 19th century, with maximum values of 9.3μgm-2yr-1 recorded ~1940. Lead isotopic ratios show two mixing lines: one which represents inputs from local and regional geogenic sources, and another that comprises regional geogenic and pollution sources. Detrending the Pb isotopic ratio record (thereby extracting the effect of the geogenic mixing) has enabled us to reconstruct a detailed chronology of metal pollution. The first sustained decrease in Pb isotope signals is recorded as beginning ~1740-1780 with the lowest values (indicating the highest pollution signature) dated to ~1960-1970. The 206Pb/207Pb ratio of excess Pb (measuring 1.222, and reflecting pollution-generated Pb), when compared with the Pb isotopic composition of the Sandhavn peat record since the 19th century and the timing of Pb enrichments, clearly points to the dominance of pollution sources from North America, although it did not prove possible to further differentiate the emissions sources geographically.

Latitudinal limits to the predicted increase of the peatland carbon sink with warming

The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around ad 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.Analysis of peatland carbon accumulation over the last millennium and its association with global-scale climate space indicates an ongoing carbon sink into the future, but with decreasing strength as conditions warm.

Investigating molecular changes in organic matter composition in two Holocene lake-sediment records from central Sweden using pyrolysis-GC/MS†

Organic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long-term (millennial) changes in ...

Vegetation Changes and Woodland Management Associated with a Prehistoric to Medieval Burnt Mound Complex at Ballygawley, Northern Ireland

ABSTRACT This paper examines the impact on woodlands associated with burnt mound use from floodplain sediments and peats, using a combination of pollen, non-pollen palynomorphs, micro- and macro-charcoal and worked wood for the first time. We present this data from a multi-period burnt mound complex, dating from the Late Neolithic to the Medieval period, at Ballygawley, Co. Tyrone, Northern Ireland, to reconstruct vegetation changes from the Neolithic onwards and establish the significance of these changes, in particular on woodlands whilst the burnt mounds were in use. The findings from the macroscopic charcoal suggests the most abundant trees were commonly, but not exclusively, exploited. Local woodland was seemingly unaffected by use of burnt mounds during the Neolithic and early Bronze Age based on pollen evidence. A sustained increase in microscopic charcoal coincides with a permanent decrease in alder-carr woodland during a period of near continuous burnt mound use between 1725 and 530 BC, and a second phase of high microscopic charcoal values, c. AD 880, corresponds to the end of the penultimate phase of burnt mound use. Evidence from the worked wood suggests that some form of woodland management was used for hazel from the Neolithic onwards.

Editorial: Scottish Geographical Journal (126)

Welcome to issue 126.2 of the Scottish Geographical Journal (SGJ). We would like to use this editorial to introduce you to the new editorial board. Editorial Boards play an important role in the wellbeing of academic journals. Scottish Geographical Journal (and the Scottish Geographical Magazine before it) has been lucky to have had the support of a number of high profile academic geographers, some of whom have given freely of their time to serve on the Editorial Board. In tandem with the reorganisation that has taken place at the Royal Scottish Geographical Society under the stewardship of the new Chief Executive, Mike Robinson, we felt it was time to review the membership of the SGJ Editorial Board. As such we are delighted to invite several new members onto the Editorial Board. The new board has representatives from all of the Scottish University Geography Departments. Alongside the editorial team of ourselves, David Evans and Andrea Nightingale we are joined by the previous editors Jim Hansom and Jo Sharp (Glasgow), Colin Ballantyne (St Andrews), Allan Findlay (Dundee and a former editor of this journal) Jane Jacobs (Edinburgh) and Michael Pacione (Strathclyde) The revised board also has representation from other UK and overseas Geography departments: Giles Foody (Nottingham) Ian Whyte (Lancaster), Paul Knox (Virginia Tech, US), Neil Smith (City University, New York, US), John Agnew (UCLA, US) and Pushkar K. Pradhan (Tribhuban University, Nepal) With the support of our publishers, Taylor & Francis, and the Royal Scottish Geographical Society (RSGS) we will holding regular meetings of the Editorial Board and we hope that all members of the board will be able to help us in our ambition to improve the international standing of the journal. Finally, we wish to express our sincere thanks to those members that have stood down from the Editorial Board and look forward to working with the new board to ensure the ongoing success of the Scottish Geographical Journal.