Yr BC Research Articles

Metal biogeochemistry in the Tinto–Odiel rivers (Southern Spain) and in the Gulf of Cadiz: a synthesis of the results of TOROS project

TOROS (Tinto–Odiel–River–Ocean Study) has been studying the biogeochemical processes which control metals and nutrients cycling in the mixing zone of the Tinto and Odiel rivers (SW Spain) and has established the fate of metals in the Gulf of Cadiz in relation to hydrodynamics and biological activity. The Tinto and Odiel rivers are small, with a combined mean discharge of 18 m 3/s. They drain the largest sulphide mineralisation in the world. Predominantly, Zn–Cu–Pb mineralisation has been worked since 2500 yr BC. The estuarine zone includes both an extensive area of salt marsh and an intensively industrialised urban area. As a consequence of pyrite oxidation, the Tinto and Odiel rivers are strongly acidic (pH<3) with extremely high and variable metal concentrations. Transition metals are poorly removed from the water column in the mixing zone. Moreover, drainage from large phosphogypsum waste deposits contributes to As, Hg, U and phosphate contamination of the estuary. The collapse of the tailing reservoir at los Frailes in 1998 had not impacted the chemistry of the coastal waters up to 6 months later. A large plume of metal-rich waters due to the Tinto and Odiel discharges occurs along the coast of the Gulf of Cadiz. This plume affects seasonally the Atlantic inflow through the Strait of Gibraltar. The dispersion of the metal discharges has been simulated by injection of a tracer in the 3-D hydrodynamical model. Both model and field study clearly show the inflow of metal contaminated Spanish Shelf Water through the Strait of Gibraltar.

Metal distribution and environmental problems related to sulfide oxidation in the Libiola copper mine area (Ligurian Apennines, Italy)

Metal mobility and distribution in water and sediments in the surroundings of the pyrite–chalcopyrite–sphalerite mine of Libiola, in the Gromolo Valley near Sestri Levante (Genova), are investigated to evaluate the environmental hazard in the area. The mineralisation, related to Apennine ophiolites, was already known in the Bronze Age (about 2500 yr bc), but economic exploitation started in the XVII century. Open galleries, waste dumps and acid drainage testified the past mining activities which ended in 1965. Mine waste material, covering an area of about 0.5 km 2, is reddish–yellowish, generally coarse-grained and stratified. The waste is a mixture of basalt, ultramafic-derived and iron-rich phases, with relatively high concentrations of S (mean 0.3% S) and Cu (mean 0.3% Cu), and significant contents of Zn, As, Mo and Se. Acid drainage, with pH values as low as 2.5, is quite rich in dissolved Fe, Al, Cu, Zn, Mn, Ni. Repeated sampling revealed marked chemical variations, particularly in the mine waste area, depending on water flow conditions. Where low-pH water mixes with normal (pH 8) surface water, reddish amorphous iron phases (e.g. ferrihydrite, schwertmannite) precipitate, favouring the scavenging of many elements carried by the acid waters and providing a natural way of remediation for the stream waters. The rapid flocculation causes anomalous contents of Fe, Cu, Zn, Co, Sc, Y, La, Ce, and to a lesser extent of Cr and Ni, in the sediments. Although the ochreous colloids are important components of the Gromolo River sediments for about 8 km from the mine, preliminary results indicate that, unless natural conditions change, remobilisation of heavy metals should not be expected.

Organic chemistry of embalming agents in Pharaonic and Graeco-Roman mummies.

Chemical treatments were an essential element of ancient Egyptian mummification. Although the inorganic salt natron is recognized as having a central role as a desiccant, without the application of organic preservatives the bodies would have decomposed in the humid environment of the tombs. The nature of the organic treatments remains obscure, because the ancient Egyptians left no written record of the process. Secondary textual evidence for mummification is provided by Herodotus, Diodorus Siculus, Strabo and Pliny. The most important account is that of Herodotus (about 450 yr bc), although archaeological evidence shows that by this time the process had declined significantly and the best results had been achieved centuries before. His account mentions myrrh, cassia, palm wine, 'cedar oil' (still widely disputed) and 'gum'; however, it is vague with respect to the specific natural products used. Here we report the results of chemical investigations of a substantial collection of samples of tissues, wrappings and 'resinous/bituminous' materials from provenanced and dated Egyptian mummies. We focused on examples of the 'classic' mummy-making culture of the Pharaonic or dynastic period, from which we can begin to track the development of mummification chronologically.

Pine pollen in intertidal sediments from Poole Harbour, UK; implications for late-Holocene sediment accretion rates and sea-level rise

Abstract Marked differences exist between long- and short-term estimates of sea-level rise in southern England. Crucial to resolving these differences is the development of dating techniques capable of bridging the gap between the late-Holocene radiocarbon chronology and the more recent 210 Pb and observational records of sediment accretion and sea-level change. In this paper we identify an increase in Pinus pollen in a sediment core collected from a saltmarsh in Poole Harbour, Dorset. This has been dated to ca. 1750 AD and reflects the historically documented spread of coniferous plantations across the region. This biostratigraphic age horizon, together with other pollen and radiocarbon data, is used to analyse long- and short-term rates of sediment accretion and sea-level change. A basal radiocarbon date indicates a rise in relative sea-level since 1510–1260 cal. yr BC (3130±60 14 C yr BP) of 1.99 m, at a rate of approximately 0.59 mm a -1 . Between ca. 1750 AD and ca. 1890 AD sediment accretion rates rose from 0.29 mm a -1 to 1.14 mm a -1 , perhaps reflecting an acceleration in relative sea-level rise. These rates increased further to 7.17 mm a -1 after ca. 1890 AD, following the development of a Spartina anglica dominated saltmarsh in Poole Harbour. These data demonstrate that caution should be exercised when using sediment accretion rates from saltmarshes recently colonised by S. anglica as proxy data for sea-level rise.

Archaeological and palaeoecological indications of an abrupt climate change in The Netherlands, and evidence for climatological teleconnections around 2650 BP

A sudden and sharp rise in the C-14 content of the atmosphere, which occurred between ca. 850 and 760 calendar yr BC (ca. 2750-2450 BP on the radiocarbon time-scale), was contemporaneous with an abrupt climate change. In northwest Europe (as indicated by palaeoecological and geological evidence) climate changed from relatively warm and continental to oceanic. As a consequence, the ground-water table rose considerably in certain low-lying areas in The Netherlands. Archaeological and palaeoecological evidence for the abandonment of such areas in the northern Netherlands is interpreted as the effect of a rise of the water table and the extension of fens and bogs. Contraction of population and finally migration from these low-lying areas, which had become marginal for occupation, and the earliest colonisation by farming communities of the newly emerged salt marshes in the northern Netherlands around 2550 BP, is interpreted as the consequence of loss of cultivated land. Thermic contraction of ocean water and/or decreased velocity and pressure on the coast by the Gulf Stream may have caused a fall in relative sea-level rise and the emergence of these salt marshes. Evidence for a synchronous climatic change elsewhere in Europe and on other continents around 2650 BP is presented. Temporary aridity in tropical regions and a reduced transport of warmth to the temperate climate regions by atmospheric and/or oceanic circulation systems could explain the observed changes. As yet there is no clear explanation for this climate change and the contemporaneous increase of C-14 in the atmosphere. The strategy of C-14 wiggle-match dating can play an important role in the precise dating of organic deposits, and can be used to establish possible relationships between changing C-14 production in the atmosphere, climate change, and the impact of such changes on hydrology, vegetation, and human communities.

Use of antagonists to assess PAF receptors heterogeneity

Big storm events represent a major risk for populations and infrastructures settled on coastal lowlands. In the Western Mediterranean, where human societies colonized and occupied the coastal areas since the Ancient times, the variability of storm activity for the past three millennia was investigated with a multi-proxy sedimentological and geochemical study from a lagoonal sequence. Mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal/marine origin of sediments deposited into the lagoon. The multi-proxy analysis shows that coarser material, low magnetic susceptibility, and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence. A comparison with North Atlantic and Western Mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods, suggesting a climatically-controlled mechanism for the occurrence of these storm periods. Besides, an in-phase storm activity pattern is found between the Western Mediterranean and Northern Europe. Spectral analyses performed on the Sr content revealed a new 270-year solar-driven pattern of storm cyclicity. For the last 3000 years, this 270-year cycle defines a succession of ten major storm periods (SP) with a mean duration of 96 ± 54 yr. Periods of higher storm activity are recorded from >680 to 560 cal yr BC (SP10, end of the Iron Age Cold Period), from 140 to 820 cal yr AD (SP7 to SP5) with a climax of storminess between 400 and 800 cal yr AD (Dark Ages Cold Period), and from 1230 to >1800 cal yr AD (SP3 to SP1, Little Ice Age). Periods of low storm activity occurred from 560 cal yr BC to 140 cal yr AD (SP9 and SP8, Roman Warm Period) and from 820 to 1230 cal yr AD (SP4, Medieval Warm Period).

High-Precision Decadal Calibration of the Radiocarbon Time Scale, AD 1950–2500 BC

The radiocarbon ages of dendrochronologically dated wood samples, each covering 10 years, are reported back to 2500 yr BC. The decadal calibration curve constructed from these data is an extension of the curve previously given for the AD interval (Stuiver, 1982). A major difference with the previous work, however, is the assessment of the error in the radiocarbon age determination. Whereas previously this error was only based on the Poisson counting statistics of the accumulated number of counts for the sample and standards, the current calibration error is based on an estimate of the reproducibility in the radiocarbon activity determination. As a consequence, the uncertainty in the current calibration curve is, on average, 1.6 times that of the AD curve previously given.