image/svg+xml199XI/2/2020INTERDISCIPLINARIA ARCHAEOLOGICANATURAL SCIENCES IN ARCHAEOLOGYhomepage: http://www.iansa.euThematic reviewAdvances in Archaeological Soil Chemistry in Central EuropeRoderick B. Salisburya,b*aDepartment of Prehistoric and Historical Archaeology, University of Vienna, Franz-Klein-Gasse 1, 1190 Vienna, AustriabOREA Institute for Oriental and European Archaeology, Austrian Academy of Sciences, Hollandstrasse 11+13, 1020 Vienna, Austria1. IntroductionSoils and sediments are archaeological materials, archaeological resources that contain an archive of past events and cultural behaviours. For nearly one hundred years, archaeologists and soil scientists have accessed parts of this archive through applications in archaeological soil chemistry. Central Europe has been home to several key developments in archaeological soil chemistry, from the earliest applications of soil phosphate analysis to recent practical application of portable X-ray Fluorescence spectroscopy. Established methods, including phosphate analyses and multi-element ICP-MS/OES, have provided interpretations of the use of space within settlements and houses, and the function of specifc archaeological features. As archaeology continues to evolve as a discipline, micro-remains are becoming increasingly important sources of data about past human mobility, diversity, production, consumption, and human ecodynamics. These data come from a range of sources, including both human and animal remains, primarily bones and teeth (proteomics, Charltonet al., 2019; strontium isotopes, Giblinet al., 2013), and portable artefacts (e.g.starch grains on grinding stones and ceramics, Dukeet al., 2018; ceramic residue analysis Dunne,et al., 2019; residues on lithics, Rotset al., 2015).Chemistry of soils and sediments have been recognized, and utilized, for a longer time. In addition to soil phosphate analysis, soil chemical methods for archaeology traditionally include multi-element chemistry, soil pH, magnetic susceptibility, and soil organic carbon and nitrogen. Recently, research in the Central European Palaeolithic have combined these, for example, assessing carbon, nitrogen, and magnetic susceptibility at the Pod Hradem cave to aid in interpreting soil formation and potential climatic changes (Nejman et al.2018; 2020). Nevertheless, full exploitation of the soil archive remains sporadic.Cultural soilscapes (Salisbury, 2016; Wells, 2006) hold ancient human and environmental DNA (Slonet al., 2017; Willerslevet al., 2003), biomarkers (Kovaleva and Kovalev, 2015; Zocatelliet al., 2017), traces of pollution (Martínez Cortizaset al., 2016; Veron et al., 2014), evidence of ecological changes and the environmental impact of Volume XI ● Issue 2/2020 ● Pages 199–211*Corresponding author. E-mail: INFOArticle history:Received: 9thSeptember 2020Accepted: 27thNovember 2020DOI: words:archaeological soil chemistryarchaeological prospectionsettlement patternsactivity areasCentral EuropeABSTRACTAnalytical technologies for the evaluation of archaeological soils have developed rapidly in recent decades, and now support a range of innovative research and interpretations of archaeological sites and landscapes. Established methods, including phosphates and multi-element ICP-MS/OES, have provided interpretations of the use of space within settlements and houses, and the function of specifc archaeological features. Recently, portable X-Ray Fluorescence has been introduced to archaeological soil science, but published results have generated knowledge gaps. The correspondence between archaeological geochemical anomalies and specifc human activities is partly dependent on geology (including sediment type and relative acidity and permeability of the soil), topography, and formation processes, as well as infuence of human activities. At the same time, which elements, and fractions of elements, are measured is largely dependent on instrument parameters and extraction methods. This paper provides an overview of archaeological soil chemistry in Central Europe, and the current state-of-the-art, followed by an assessment of future developments in archaeological soil chemistry, molecular biogeochemistry, and the signifcance of geoarchaeology in multi-disciplinary research.
image/svg+xmlIANSA 2020 ● XI/2 ● 199–211Roderick B. Salisbury: Advances in Archaeological Soil Chemistry in Central Europe200cultural behaviour (Schumacheret al., 2016; Sprafke, 2016), archaeological site formation processes (Nicoll and Murphy, 2014), raw material provenance for components of ceramic matrices (Riebe and Niziolek, 2015), and the contamination of cultural heritage and artefacts by modern pollution (Nordet al., 2005). Continued development of archaeological biogeochemistry is beginning to recognize the archaeological potential of proteomics, genomics, and other biomarkers in the soil archive.Several reviews of archaeological sol chemistry have been published (Oonket al., 2009a; Wilsonet al., 2008); of especial import was the detailed summary of soil phosphate methods in archaeology by Holliday and Gartner (2007). A vast body of literature exists for archaeological soil chemistry (Table 1). This review of the history and development of archaeological soil chemistry focuses on examples from Central Europe, and the current state-of-the-art, followed by an assessment of future developments in molecular biogeochemistry and the signifcance of geoarchaeology in multi-disciplinary research. Currently, trends are changing from the traditional roles of archaeological soil chemistry – site prospection and delimiting habitation areas – into a complex, multi-disciplinary endeavour integrating various strands of Table 1.Selected references for archaeological soil chemistry, with focus on Central Europe (arranged chronologically).Type of studyReferencesSoil chemistry & soil scienceFeigl, 1960; Bowen, 1979; Füleky, 1983; Kabata-Pendias and Pendias, 1984; Sposito, 1998; Sparks 1996; 2003; Holliday 2004.Early archaeological investigationsArrhenius, 1929; 1931; Lorch, 1930; 1940; 1941; 1951; Schnell, 1932; Christensen, 1935; Bandi, 1945; Stoye, 1950; Lutz, 1951; Dauncy, 1952; Pelikán, 1954; Dietz, 1957.Methdological reviews and historiesSjoberg, 1976; Eidt, 1977; Keeley, 1981; Bethell and Máté, 1989; Zölitz and Heinrich, 1990; Walker, 1992; Kondratiuk and Banaszuk, 1993; Bjelajac et al., 1996; Aston et al., 1998; Klamm et al., 1998; Leonardi et al., 1999; Haslam and Tibbett, 2004; Wells 2004a; Holliday and Gartner, 2007; Wilson et al., 2008; Oonk et al., 2009a; Pastor et al., 2016.Applications in Central Europe PhosphateGundlach, 1961; Schwarz, 1967; Grimm, 1971; Sjöberg, 1976; Kiefmann, 1979; Zölitz, 1980; 1982; 1983; 1986; Gebhardt, 1982; Majer, 1984; Zimmermann, 1995; 2001; 2008; Stäuble and Lüning, 1999; Majer, 2004; Sarris et al., 2004; Ernée, 2005; Ernée and Majer, 2009; Hlavica et al., 2011; Schreg and Behrendt, 2011; Petřík et al., 2012; Salisbury, 2012; Lauer et al., 2013; Salisbury et al., 2013; Weihrauch et al., 2017; Weihrauch and Söder, 2020; Weihrauch et al., 2020.Multi-elementHejcman et al., 2011; 2013a; 2013b; Gauss et al., 2013; Salisbury, 2013; Pető et al., 2015; Lubos et al., 2016; Salisbury, 2016; Dreibrodt et al., 2017; Smejda et al., 2017; 2018; Horák et al., 2018; Janovský and Horák, 2018; Pankowská et al., 2018; Pető et al., 2019; Dreslerová et al., 2020.Future directionsLipid biomarkersBull et al., 2000; Bull et al., 2002; Schwark et al., 2002; Killops and Killops, 2005; Zech et al., 2010; Schatz et al., 2011; Sistiaga et al., 2014; Prost et al., 2017; Zocatelli et al., 2017; Harrault et al., 2019; Schirrmacher et al., 2019; Patalano et al., 2020; Portillo et al., 2020.Isotopes Bogaard et al., 2007; D’Anjou et al., 2012; Abell et al., 2019; Bataille et al., 2020; Snoeck et al., 2020.Sediment aDNAHebsgaard et al., 2009; Giguet-Covex et al., 2014; Madeja, 2015; Thomsen and Willerslev, 2015; Parducci et al., 2017; Slon et al., 2017; Brunson and Reich, 2019; Epp et al., 2019; Nejman et al., 2020.ProteomicsOonk et al., 2012.geoarchaeology, bioarchaeology, and environmental studies. This trajectory needs geoarchaeologists to contribute to diachronic and synchronic examinations of archaeological landscapes and human-ecodynamics.2. Archaeological soil phosphates in Central EuropeThe history of archaeological soil chemistry extends over a century (Arrhenius, 1931) and across the globe, from Alaska (Knudsonet al., 2004) to the Levant (Šmejdaet al., 2018) and to Australia (Fanninget al., 2018). The link between ancient human occupation and increased soil phosphate content were frst noted in late 19thor early 20thcentury agricultural soil surveys (Russell, 1915). Publication of methods and results began when Swedish agronomist Olaf Arrhenius recognized and recorded the relationship between surface fnds, human occupation, and soil phosphate levels while conducting agricultural soil testing, and posited a causal correlation between enhanced soil phosphates and human settlements (Arrhenius, 1929; 1931). The method was applied to Swedish habitation sites by Schnell (1932), who sampled along transects radiating outward from an assumed
image/svg+xmlIANSA 2020 ● XI/2 ● 199–211Roderick B. Salisbury: Advances in Archaeological Soil Chemistry in Central Europe201central point in a given site and constructed isopleth maps of the phosphate values to delimit site boundaries. Following this, archaeologists in Central Europe and elsewhere have conducted soil phosphate analyses for archaeological survey and site interpretations for nearly a century, with continuing methodological developments.Early archaeological soil chemistry focused primarily on phosphates for four reasons: First, it was the frst element explicitly connected to prehistoric human habitation, and subsequent studies exploited this discovery. Second, it is essential to life and therefore can be found in and deposited by anything organic, as primary, secondary, or in siturefuse. Inputs include food preparation wastes such as bone, meat, fsh, and plants, wood ash, human or animal burials, and urine and faeces of humans and animals. Therefore, human habitation areas will have higher levels of soil P than surrounding areas with no habitation. Conway (1983) demonstrated that human occupation could result in annual increases in concentrations of P from 1–10%. Third, phosphates tend to accumulate quickly, have low solubility and a strong ability to fx within the soil profle. In favourable soil conditions, P remains stable and is likely to be retained, even in disturbed soils, for millennia without appreciable leaching. Fourth, in its most basic form, phosphate testing is fast and inexpensive compared with almost every other analytical technique, and can be conducted in the feld during survey or excavation.2.1 The frst 60 years of archaeological soil phosphate analysisArrhenius’s methods were quickly applied to prehistoric and medieval sites in Central Europe by German geographer Walter Lorch (1940; 1941; 1951). Lorch sampled along regular transects across and around ancient settlements, used a laboratory colorimetric method to measure phosphate content, and graphed the results. By comparing graphs of density and distribution, and interpreting the diferent profles, Lorch persuasively argued that variability in phosphate was due to diferent subsistence economies in the Palaeolithic, Neolithic, and metal ages. Other research projects soon followed. Bandi (1945) used Lorch’s method to locate a medieval site in Switzerland. Dietz (1957) used a method of sulphuric acid in test tubes visually compared to standards to examine a small plot of land with surface material indicating prehistoric activity, looking for evidence of organic waste deposits.The next major advance in archaeological soil phosphate studies came with the development of a spot-test, or ring-chromatography test, by Friedrich “Fritz” Feigl in Vienna. In his comprehensive two-volume compendium on chemical spot-tests, Feigl (1960) recommended the highly toxic and corrosive nitric acid (HNO3) to prepare an ammonium molybdate solution, and the toxic and fammable benzidine as a reducing agent to measure inorganic phosphate from geological samples. Gundlach (1961) modifed Feigl’s method to increase the speed and safety when testing soil from boreholes at prehistoric sites. Gundlach retained the nitric acid for digestion, but switched to the organic and relatively harmless ascorbic acid (C6H8O6) for reduction, making it more stable and eliminating the need for fame and ammonia in feld conditions. In any acid-molybdate method, PO4reacts with molybdate to form phosphomolybdic acid (yellowish in colour); in Gundlach’s method, phosphomolybdic acid is reduced by ascorbic acid to form a blue complex. Gundlach conducted his tests in the feld, with the flter paper and drop bottles attached to a pole stuck in the ground next to his borehole (depicted in Gundlach, 1961 p.736, Figure 1), and noted that the entire process takes approximately 90 seconds. Gundlach ranked the results on a scale of 1–5, from none to very high levels of P.Schwarz (1967) used the Gundlach method and established a feld methodology for sample collection, collecting samples in plastic bags, collecting enough soil to run multiple tests and to determine colour and grain size, and collecting samples by layer. Schwarz conducted large-scale surveys near the San Bernardino Pass in southern Switzerland, taking samples at 30– 50 m intervals. Two suggestions regarding research methodology are of note from the Schwarz’s paper. First, he observed that some information about land-use, previous archaeological investigations, and geomorphology are essential to planning a chemical survey campaign. Second, he suggested that phosphate surveys would be more useful when complemented by geophysical surveys or test trenching, and warned that carrion pits, where local villagers dispose of diseased animals, should not be mistaken for prehistoric habitations (Schwarz, 1967, pp.58–61). Schwarz’s sampling approach has been criticized (Sjöberg, 1976, p.449) because of his suggestion that samples be taken along natural lines, such as feld boundaries, rather than on a regular grid or transect system.Kiefmann (1979) conducted large-scale phosphate mapping in East Holstein and arrived at two signifcant conclusions. First, soil phosphate content is infuenced by both changing land-use and pedogenesis. That is, archaeological soil chemistry requires some understanding of both cultural and non-cultural formation processes, including soil formation. Second, Kiefmann found that diferent extraction methods yielded diferent P concentrations and distributions.Zölitz (1980) pioneered the use of variogram modelling as a statistical method for analysing soil phosphate results. Majer (1984) developed a 3-point relative scale for measuring results, and noted that archaeologists were most interested in the anthropogenic enhancement of soil phosphate, rather than the total quantity of P. Phosphate surveys successfully identifed residential areas in both prehistoric and medieval sites (Grimm, 1971; Zölitz, 1982; 1983; 1986).Eidt refned Gundlach’s method further, frst by replacing nitric acid with hydrochloric acid (HCl) (Eidt, 1973) and then by developing a bath to stop the chemical reaction, so that results could be archived (Eidt, 1977). Eidt found that HCl is superior to both nitric acid and sulphuric acid when extracting P in laboratory tests, and observed that the use of HCl for both feld and lab analyses would improve comparability of results. He also noted that the question of
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