Lipid biomarkers and metal pollution in the Holocene record of Cartagena Bay (SE Spain): Coupled natural and human induced environmental history in Punic and Roman times.

We reconstructed the palaeoenvironmental conditions of Cartagena Bay during the Holocene after a multidisciplinary study to identify natural variations and the anthropic processes of this coastal area. A total of 119 samples were recovered for amino acid racemization dating, 3 for radiocarbon dating (14C), and four sets of 80 samples for sedimentological and palaeontological determination, mineralogical content, biomarker and trace elements quantification. Two natural scenarios were identified from the variations of n-alkane indices and palaeobiological content. The first period (6650-5750 yr cal BP) was marked by the development of euhaline marine conditions with strong inputs from aquatic macrophytes and high biodiversity. After a hiatus, the area underwent a profound change, becoming a paucispecific brackish marsh environment with increasing inputs from land plants, with possible episodes of emersion with a greater presence from terrestrial gastropods (3600-300 cal yr BP). By combining trace element abundance and stanol distributions, our study also provides a novel approach to identify the predominant influence of anthropogenic factors in the last three millennia in the coastal record of Cartagena Bay. Findings confirmed that Pb mining and metallurgy began during the Bronze Age, with considerable inputs of this heavy metal into the atmosphere during Phoenician, Punic and particularly Roman times compared to the Middle Ages. Pollution by Cu and Zn was also observed during Punic and Roman times, and was first documented in the Middle Ages. In addition, faecal stanols, such as coprostanol, derived mainly from humans, and 24-ethylcoprostanol from herbivores were present, thereby indicating for the first time a continuous presence of human populations and significant pollution input since 3600 yr cal BP, this being greater in the late Bronze Age and Phoenician, Punic and Roman times than during Late Antiquity and the Middle Ages, when the city was in decline.

Keys to discern the Phoenician, Punic and Roman mining in a typical coastal environment through the multivariate study of trace element distribution.

Trace element concentrations in the Cartagena Bay coastal record reveal a contribution of natural processes. However, the influence of anthropogenic factors predominates in the last three millennia, particularly aerosol deposition linked to mining and industrial activities in the area. The coastal record of Cartagena can be considered a preserved environment, suitable to search for regional human activity fingerprinting, specifically that related to the deposition of heavy metals such as Pb and Cu. A multivariate statistical analysis was carried out to clarify the geochemical behaviour of trace and major elements. Our study design represents a novel approach to assign natural contributions, such as eolian and riverine input, to coastal deposits, and organic matter preservation under anoxic environments. Therefore, synergies obtained by the simultaneous study of multivariate statistics and enrichment factors allow robust conclusions about palaeoenvironmental evolution and human activities. Anthropogenic influence suggested that Pb mining and metallurgy began during the Chalcolithic period, with considerable inputs of Pb and Cu to atmospheric pollution during Phoenician, Punic and Roman times.

A multivariate examination of the timing and accumulation of potentially toxic elements at Las Conchas bog (NW Spain).

The inorganic content of the well-preserved 3.2-m record of Las Conchas bog (NW Spain), covering 8000 cal yr BP., was analysed. To study natural vs. human contributions, we applied an innovative approach, namely the sequential study of multivariate statistics (factor analysis followed by clustering of the factor score matrix) and enrichment factors (EFs). The increasing weight of potentially toxic elements (PTEs) such as the geochemical association of Zn, Pb and Cd (EFs higher than 10, 20 and 40 in the last two centuries) was revealed, and corroborated by the contrast between the contents of anthropogenic Pb and total Rare Earth Elements (a suitable proxy for natural geogenic supplies). Furthermore, elements such as Hg, Tl and As also showed enrichment in the most recent samples of the study core. Some of them are commonly associated with global atmospheric transport; however, in this case, their increasing contents could also be explained by nearby industrial and mining activities. In summary, severe pollution was observed in the uppermost part of the record, thereby pointing to an important environmental concern. Given that local and regional sources of PTEs, such as mining and heavy industry, especially Zn smelting, were probably the main historical causes of this contamination and that some of these industries are still active, we consider that our findings deserve further attention.

Early metal pollution in southwestern Europe: the former littoral lagoon of El Almarjal (Cartagena mining district, S.E. Spain).A sedimentary archive more than 8000 years old.

A borehole drilling campaign has allowed the study of a former littoral lagoon located next to the harbour city of Cartagena in South-East Spain (close to the Sierra de Cartagena polymetallic ore deposits). This lagoon, which developed during the Holocene, was first a shallow sedimentary marine environment and later evolved into a swampy semi-endorheic basin named "Almarjal" (after the Arab term from the fourteenth century). The lagoon eventually dried out and at present forms part of the substratum of the modern sector of the city urban area. The basin representative sediments are sapropelic black silty facies forming a continuous sedimentary archive, accounting for more than 8000 years of depositional phenomena. The geochemical study of these sediments, together with their absolute calibrated dating by 14C, allows definition of successive stages of mining and metallurgical activities in the area. In turn, this information provides a more comprehensive perspective regarding metal pollution, particularly lead contamination during different periods of the Recent Prehistory and the Classical Age. The results indicate that the beginning of contamination by lead and other heavy metals occurred as early as 4500 years ago, when the Final Chalcolithic period was taking place in the South-East of the Iberian Peninsula. This finding provides further insights regarding the debate on the origins of lead mining and metallurgy in SE Spain.

Multivariate study of trace element distribution in the geological record of Roñanzas Peat Bog (Asturias, N. Spain). Paleoenvironmental evolution and human activities over the last 8000 calyr BP.

Trace element concentrations in the Roñanzas peat bog record reveal a contribution of natural processes but the influence of anthropogenic factors predominates in the last two millenniums, particularly aerosol deposition linked to mining and industrial activities in northern Spain. We observed that the Roñanzas record can be considered a preserved environment, suitable to search for local (<50 km), regional (50-150 km) and/or long-distance human activity fingerprinting, specifically that related to the deposition of heavy metals such as Pb, Zn and Hg. We also carried out a multivariate statistical study in order to clarify the geochemical behavior of trace and major elements. Our study design represents a novel approach to assign natural vs. human contributions in peatlands. Therefore, synergies obtained by the simultaneous study of multivariate statistics and enrichment factors allow robust conclusions about paleoenvironmental evolution and human activities. Anthropogenic influence has also been reported in similar records in other parts of Europe, thereby suggesting large-scale sources for atmospheric pollution. However, here we revealed remarkable particularities, such as the association of Cd, Zn and Pb, mainly linked to regional and local factors (mining and more recently the metallurgical industry), whereas we propose that the occurrence of Hg is associated with a combination of regional factors and global atmospheric pollution.

Enantioenrichment in sublimed amino acid mixtures.

A real amplification of an initial enantiomeric excess can be detected when two amino acids are sublimed at high temperature, even if one of the components is a racemic compound that does not convert into a conglomerate by sublimation.

Asymmetric amplification in amino acid sublimation involving racemic compound to conglomerate conversion.

A straightforward unprecedented sublimation protocol that reveals both conversion of a racemic compound into a racemic conglomerate and subsequent enantioenrichment has been developed for the proteinogenic amino acid valine. The phenomenon has been observed in closed and open systems, providing insight into asymmetric amplification mechanisms under presumably prebiotic conditions.

Solution-phase racemization in the presence of an enantiopure solid phase.

Solution-phase racemization drives the evolution of single chirality in the solid phase by the "chiral amnesia" process first described by Viedma. The current investigations lay the basis for a better understanding of the mechanism of the solid-phase deracemization by uncoupling the chemical rate processes associated with the interconversion of enantiomers in the solution phase from the physical processes associated with solution-solid phase transfer via dissolution and reaccretion of molecules onto crystals. In addition, the enantiomer concentration profiles presented in this work, together with an analytical treatment of the racemization process in the presence of excess enantiopure solid, unequivocally reconfirm the validity of the Meyerhoffer double solubility rule for systems under solution racemization conditions.

Evolution of solid phase homochirality for a proteinogenic amino acid.

The inexorable evolution of solid-phase single chirality is demonstrated for the first time for a proteinogenic amino acid. Enantioenrichment is observed both under attrition-enhanced conditions and without the aid of particle grinding. Differences in the form of the conversion profiles for the process under the two sets of conditions provide suggestions concerning the mechanism of the transformation.

Hominid exploitation of the environment and cave bear populations. The case of Ursus spelaeus Rosenmüller-Heinroth in Amutxate cave (Aralar, Navarra-Spain).

Cave bears (Ursus deningeri and U. spelaeus) and hominids (Homo heidelbergensis, H. neanderthalensis, and H. sapiens) were potential competitors for environmental resources (subterranean and open air). Here, we examined the age at death of cave bear (Ursus spelaeus Rosenmüller-Heinroth) specimens from Amutxate cave in order to shed light on the effect of resource sharing between cave bears and hominids. After studying dental wear of the deciduous and permanent dentitions, the ontogenetic development of mandibles, and incremental layers of cement (annuli), we defined five age groups differentiated by marked development and size gaps. Our findings indicate that after hibernating, bears abandoned the den, thereby leaving the subterranean environment (caves) free for temporary hominid occupation-this would explain the subtle traces of hominid presence in many dens. However, a simple calculation based on age at death of subadult and adult cave bear specimens in Amutxate cave, extrapolated to the whole cave area, showed that the area surrounding this cave hosted bears for at least 9,000 years. This length of habitation, quite similar to the time-span derived from amino acid racemization and electron spin resonance, indicates that bear populations in the Amutxate cave constituted a serious constraint for hominid exploitation of the environment.

Paleobiology and comparative morphology of a late Neandertal sample from El Sidron, Asturias, Spain.

Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample approximately 43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north-south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.