A western route of prehistoric human migration from Africa into the Iberian Peninsula.

Being at the western fringe of Europe, Iberia had a peculiar prehistory and a complex pattern of Neolithization. A few studies, all based on modern populations, reported the presence of DNA of likely African origin in this region, generally concluding it was the result of recent gene flow, probably during the Islamic period. Here, we provide evidence of much older gene flow from Africa to Iberia by sequencing whole genomes from four human remains from northern Portugal and southern Spain dated around 4000 years BP (from the Middle Neolithic to the Bronze Age). We found one of them to carry an unequivocal sub-Saharan mitogenome of most probably West or West-Central African origin, to our knowledge never reported before in prehistoric remains outside Africa. Our analyses of ancient nuclear genomes show small but significant levels of sub-Saharan African affinity in several ancient Iberian samples, which indicates that what we detected was not an occasional individual phenomenon, but an admixture event recognizable at the population level. We interpret this result as evidence of an early migration process from Africa into the Iberian Peninsula through a western route, possibly across the Strait of Gibraltar.

In situ continuous monitoring of chloride, nitrate and ammonium in a temporary stream Comparison with standard methods.

A multi-parameter probe was used for in situ chloride, nitrate and ammonium measurements in a temporary stream (Ribeira da Pardiela, in the South of Portugal). Comparison with standard analytical methods was performed for all elements. For chloride, the results of the probe depicted the same behaviour as that obtained with the standard method, although it is clear that the matrix effects were present. For nitrate, the results obtained with the probe were in agreement with the other standard methods used, except for samples collected during drought, when the stream water became brownish and exhaled an offensive smell, due to the decomposition of organic matter. For ammonium, surprisingly the probe show to be the best option, the phenate method being affected by matrix effects. The results still suggest an interference of the bicarbonate ion on nitrate determination, but standard additions approach was shown to minimize most of the matrix effects. Recoveries were reasonable to good for all the three anions under scrutiny.

Fragmentation pathways of organoarsenical compounds by electrospray ion trap multiple mass spectrometry (MS6).

With its detection limit well below 30 pg microl(-1) LC-MS-MS has become a sensitive and thus popular analytical technique for organoarsenical compounds. Collision induced dissociation (CID) is a valuable tool for speciation and facilitates a positive identification of the species detected. However, it is not straightforward to understand the fragmentation pathways of organoarsenical compounds when only CID-MS-MS data is available. In the present paper we have investigated multiple mass spectrometry (MSn, n=1, 2, 3, 4, 5, 6) with electrospray CID fragmentation for a number of organoarsenical compounds likely to occur in the environment. The investigated compounds were tetramethylarsonium, trimethylarsinoxide, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, and dimethylarsinoylethanol. By CID of (protonated) organoarsenical cations mostly even-electron fragments are produced after neutral loss processes such as elimination of H2, H2O, CH4, C2H2, C2H4, C2H6, HCHO, CH3OH, C2H5OH, C2H4O, and CH2CO. However, abundant odd-electron fragments are also formed after elimination of radical species. Evidence for reduction of As(V) to As(III) as a driving force in the odd-electron ion formation is obtained.