Neolithic and Bronze Age topsoil relicts revealed enhanced extractable phosphorus (P) and plant available inorganic P fractions, thus raising the question whether there was targeted soil amelioration in prehistoric times. This study aimed (i) at assessing the overall nutrient status and the soil organic matter content of these arable topsoil relicts, and (ii) at tracing ancient soil fertilizing practices by respective stable isotope and biomarker analyses. Prehistoric arable topsoils were preserved in archaeological pit fillings, whereas adjacent subsoils served as controls. One Early Weichselian humic zone represented the soil status before the introduction of agriculture. Recent topsoils served as an additional reference. The applied multi-proxy approach comprised total P and micronutrient contents, stable N isotope ratios, amino acid, steroid, and black carbon analyses as well as soil color measurements. Total contents of P and selected micronutrients (I, Cu, Mn, Mo, Se, Zn) of the arable soil relicts were above the limits for which nutrient deficiencies could be assumed. All pit fillings exhibited elevated δ15N values close to those of recent topsoils (δ15N>6 to 7‰), giving first hints for prehistoric organic N-input. Ancient legume cultivation as a potential source for N input could not be verified by means of amino acid analysis. In contrast, bile acids as markers for faecal input exhibited larger concentrations in the pit fillings compared with the reference and control soils indicating faeces (i.e. manure) input to Neolithic arable topsoils. Also black carbon contents were elevated, amounting up to 38% of soil organic carbon, therewith explaining the dark soil color in the pit fillings and pointing to inputs of burned biomass. The combination of different geochemical analyses revealed a sufficient nutrient status of prehistoric arable soils, as well as signs of amelioration (inputs of organic material like charcoal and faeces-containing manure).

No abstract

No abstract

One major challenge in nanomaterial analysis, especially in complex environmental matrices, is the unambiguous differentiation between natural and engineered nanomaterials (ENMs). Particularly with regard to the investigation of ENM's/engineered nanoparticle's (ENPs) fate, analytical methods are needed allowing for tracing and sensitive quantification. Several ENPs are metal-based and contain elements being omnipresent in environmental matrices (e.g., Al, Ti, Zn, Fe and non-metal Si) - hence, high background levels of these elements are expected, compromising sensitive detection. In this work we developed successfully a combined approach of stable isotope labeling (tracing) and reverse postchannel species-unspecific on-line isotope dilution (quantification) in combination with AF4/sector-field ICP-MS (AF4/ICP-SFMS). The approach was successfully applied to iron oxide nanoparticles isotopically enriched in Fe-57 coated with a SiO2 shell (Fe-57@SiO2 ENPs). Upon method development and validation the Fe-57@SiO2 ENPs were spiked into a filtered re-suspended river sediment-slurry matrix for proof-of-concept. Our approach allowed for unambiguous tracing of the Fe-57@SiO2 ENPs among natural iron colloid fractions as well as simultaneous sensitive quantification via reverse on-line ID despite high "natural" iron background. A limit of detection of 2.4 mu g Fe L-1 and a limit of quantification of 7.8 mu g Fe L-1 in real matrix was achieved. Furthermore, a good reproducibility in terms of peak areas was obtained (0.4-3.0%); the RSDs for elution times vary between 0.1 and 0.7%. To the best of the authors' knowledge, for the first time a reverse post-channel on-line isotope dilution AF4/ICP-SFMS approach in combination with isotopically labeled Fe-57@SiO2 ENPs was developed, allowing for (i) unambiguous tracing, and simultaneous (ii) sensitive quantification of the Fe-57@SiO2 ENPs within a sediment slurry matrix in the presence of natural iron colloid fractions. Based on the experience gained in this work, we feel certain that the approach is deployable to further stable isotope labeled metal-and nonmetal-based ENMs and shows great potential in ENMs studies