Quantitative WD-XRF calibration for small ceramic samples and their source material

A wavelength-dispersive X-ray fluorescence (WD-XRF) calibration is developed for small powdered samples (300mg) with the purpose of analyzing ceramic artifacts that might be available only in limited quantity. This is compared to a conventional calibration using a larger sample mass (2g). The comparison of elemental intensities obtained in both calibrations shows that the decrease in analyzed sample mass results in a linear decrease in measured intensity for the analyzed elements. This indicates that the small- and large-sample calibrations are comparable. Moreover, the elemental contents of four ceramic sherds and two potential clay sources fall well within the range of the certified reference materials that are the basis of the calibration curves. The advantage with the analytical method presented here is that it is rapid and requires only a small amount of sample that can easily be re-used for further analyses. This method has great potential in ceramic provenance studies

Long-term development and trajectories of inferred lake-water organic carbon and pH in naturally acidic boreal lakes

Acknowledgements: Financial support was provided by the Swedish Research Council (Vetenskapsrådet; grants no.2008-03741, 2011-03638 and 2014-05219). We thank the many people in the research group who have contributed data over the years and the four anonymous reviewers whose comments significantly contributed to improving the manuscript. The authors declare no conflict of interestPeer reviewedPublisher PD

Assessment of the spatial distributions of total- and methyl-mercury and their relationship to sediment geochemistry from a whole-lake perspective

The aim of this study was to determine the spatial variability for total- and methylmercury in surface sediments (0–2 cm) across a single whole-lake basin, and to relate this variability to the sediment’s geochemical composition. 83 surface sediment samples from Stor-Strömsjön – a lake with multiple sub-basins located in northern Sweden – were analyzed for geochemical composition as well as total-mercury (total-Hg) and methylmercury (methyl-Hg; 35 samples) concentrations. Our results indicate that variations in fine-grained mineral matter (36%) and organic matter (34%) explain an equal amount of the total-Hg variation, but that their relative importance varies between different parts of the lake. Total-Hg concentrations were similar in locations controlled by organic matter or fine-grained mineral matter (average 109 ng g␣1); however, total-Hg inventories (mass per unit area) were significantly higher in the latter (35 and 53 mg m␣2, respectively). Methyl-Hg concentrations are largely (55% of variance) controlled by water depth and sulfur concentration, which supports the importance of within lake methylation reported from other studies. Both for concentrations and inventories the spatial distribution for methyl-Hg in surface sediments is patchy, and interestingly the highest methyl-Hg inventory (1.4 mg m␣2) was found in a shallow location with coarse-grained minerogenic sediment (very low organic matter). A large spatial variability, even within a single lake, is something that needs to be recognized, e.g., when studying processes affecting mercury cycling, mercury loadings and when using lake sediments to reconstruct historic mercury deposition

Holocene atmospheric dust deposition in NW Spain

Acknowledgements The authors would like to extend their thanks to the students of the EcoPast research group (GI-1553, Universidade de Santiago de Compostela, Facultade de Bioloxía) and colleagues who helped with fieldwork and laboratory analyses. Funding The author(s) disclosed receipt of the following financial support for the research, authorship and/or publication of this article: This research was partially funded by Consiliencia network (ED431D2017/08 Xunta de Galicia) and Funding for Consolidation and Structuration of Research Units (ED431B2018/20 Xunta de Galicia).Peer reviewedPostprin

Human bones tell the story of atmospheric mercury and lead exposure at the edge of Roman World

We thank Museo de Pontevedra and Dirección Xeral de Patrimonio Xuntade Galicia for providing access to skeletal collections. OLC is funded by ED481D 2017/014Xunta de Galicia. This work was supported bythe projects: Galician Paleodiet (ED481D 2017/014), Consiliencia network (ED 431D2017/08), GPC (ED431B 2018/20) all funded by Xunta de Galicia.Peer reviewedPublisher PD

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

We would like to thank Jesús R. Aboal (Universidade de Santiago de Compostela) and Kjell Billström (Naturhistoriska Riksmuseet) for access to the laboratory facilities; Antonio Rodríguez López helped with laboratory work. This research was done under the framework of the projects CGL2010-20672 (Plan Nacional I+D+i, Spanish Ministerio de Economía y Competitividad), R2014/001 and GPC2014-009 (Dirección Xeral I+D, Xunta de Galicia). The authors gratefully acknowledge the financial support of the UK Leverhulme Trust Footprints on the Edge of Thule programme award for core collection and associated environmental research.Peer reviewedPostprin

Inorganic geochemistry of lake sediments: A review of analytical techniques and guidelines for data interpretation

Inorganic geochemistry is a powerful tool in paleolimnology. It has become one of the most commonly used techniques to analyze lake sediments, particularly due to the development and increasing availability of XRF core scanners during the last two decades. It allows for the reconstruction of the continuous processes that occur in lakes and their watersheds, and it is ideally suited to identify event deposits. How earth surface processes and limnological conditions are recorded in the inorganic geochemical composition of lake sediments is, however, relatively complex. Here, we review the main techniques used for the inorganic geochemical analysis of lake sediments and we offer guidance on sample preparation and instrument selection. We then summarize the best practices to process and interpret bulk inorganic geochemical data. In particular, we emphasize that log-ratio transformation is critical for the rigorous statistical analysis of geochemical datasets, whether they are obtained by XRF core scanning or more traditional techniques. In addition, we show that accurately interpreting inorganic geochemical data requires a sound understanding of the main components of the sediment (organic matter, biogenic silica, carbonates, lithogenic particles) and mineral assemblages. Finally, we provide a series of examples illustrating the potential and limits of inorganic geochemistry in paleolimnology. Although the examples presented in this paper focus on lake and fjord sediments, the principles presented here also apply to other sedimentary environments

Norway spruce postglacial recolonization of Fennoscandia

Contrasting theories exist regarding how Norway spruce recolonized Fennoscandia after the last glaciation. Here, the authors provide evidences from sedimentary ancient DNA and modern population genomics to support that Norway spruce was present in southern Fennoscandia shortly after deglaciation and the early Holocene migration from the east. Contrasting theories exist regarding how Norway spruce (Picea abies) recolonized Fennoscandia after the last glaciation and both early Holocene establishments from western microrefugia and late Holocene colonization from the east have been postulated. Here, we show that Norway spruce was present in southern Fennoscandia as early as 14.7 +/- 0.1 cal. kyr BP and that the millennia-old clonal spruce trees present today in central Sweden likely arrived with an early Holocene migration from the east. Our findings are based on ancient sedimentary DNA from multiple European sites (N = 15) combined with nuclear and mitochondrial DNA analysis of ancient clonal (N = 135) and contemporary spruce forest trees (N = 129) from central Sweden. Our other findings imply that Norway spruce was present shortly after deglaciation at the margins of the Scandinavian Ice Sheet, and support previously disputed finds of pollen in southern Sweden claiming spruce establishment during the Lateglacial.Peer reviewe

Inferring past trends in lake water organic carbon concentrations in northern lakes using sediment spectroscopy

Changing lake water total organic carbon (TOC)concentrations are of concern for lake management because of corresponding effects on aquatic ecosystem functioning, drinking water resources and carbon cycling between land and sea. Understanding the importance of human activities on TOC changes requires knowledge of past concentrations; however, water-monitoring data are typically only available for the past few decades, if at all. Here, we present a universal model to infer past lake water TOC concentrations in northern lakes across Europe and North America that uses visible-near-infrared (VNIR) spectroscopy on lake sediments. In the orthogonal partial least squares model, VNIR spectra of surface-sediment samples are calibrated against corresponding surface-water TOC concentrations (0.5–41 mg L-1) from 345 Arctic to northern temperate lakes in Canada, Greenland, Sweden and Finland. Internal model-cross-validation resulted in a R2 of 0.57 and a prediction error of 4.4 mg TOC L-1. First applications to lakes in southern Ontario and Scotland, which are outside of the model’s geographic range, show the model accurately captures monitoring trends, and suggests that TOC dynamics during the 20th century at these sites were primarily driven by changes in atmospheric deposition. Our results demonstrate that the lake-water TOC model has multi-regional applications and is not biased by post-depositional diagenesis, allowing the identification of past TOC variations in northern lakes of Europe and North America over timescales of decades to millennia