Handheld X-ray fluorescence geochemical data of geological and archaeological obsidian from Sonora, Mexico.

Geochemical detection using a portable XRF analyser is highly effective for nondestructive surface analysis in archaeological and geological obsidians. The data obtained in rock slabs, fragments, anhydrous nuclei, flaked and ground stone from Sonora, Mexico, were used to select certain analysed elements (Fe, Mn, Zr, Nb, Y, Th, Rb, Sr, Zn) that help to formulate geochemical variation diagrams to identify chemical trends and correlations between the samples. It proves to be an excellent analytical method for the provenance studies of archaeological artifacts. Subsequently, the integration of the obtained data here and their arrangement with the existing chemical analysis of obsidians for different localities of NW Mexico and the SW of the United States will allow for better knowledge of the primary sources of obsidian in the extraction and manufacture of archaeological artifacts.

Mercury and selenium concentrations in marine shrimps of NW Mexico: health risk assessment.

We determined total Hg and Se contents of hepatopancreas, exoskeleton, and muscle, and the Se:Hg molar ratios in the muscle of shrimps Farfantepenaeus californiensis and Litopenaeus stylirostris caught in NE Pacific Mexican waters. Total Hg mean values in muscle, hepatopancreas, and exoskeleton were 0.31 ± 0.26, 0.28 ± 0.29, and 0.24 ± 0.06 µg g-1, and 0.46 ± 0.46, 0.41 ± .034, and 0.24 ± 0.06 µg g-1 for F. californiensis and L. stylirostris, respectively. In all tissues, the mean concentrations of Se tended to be close to one order of magnitude higher than the respective Hg values. In F. californiensis, the hepatopancreas of the larger commercial size had significantly (p < 0.05) higher Hg content than smaller sizes, but correlations size-Hg concentration calculated for each tissue of either species were not significant. The Hg content of the muscle of all commercial sizes of both species was lower than the permissible limit and their Se:Hg ratios in all sizes were higher than 1, indicating low risk for human consumption.

Mercury content and their risk assessment in farmed shrimp Litopenaeus vannamei from NW Mexico.

The main objective of this study was to evaluate the total mercury content in hepatopancreas and edible muscle of the whiteleg shrimp Litopenaeus vannamei cultured along the NW coast of Mexico, and to evaluate the potential human health risk due to their consumption. Samples were obtained between May and June 2010 in 26 shrimp farms from the three most important shrimp-producing states of NW Mexico, and total Hg was analyzed after reduction with SnCl2 in a mercury analyzer. The ranges of Hg concentrations of the hepatopancreas were 0.101±0.03-0.184±0.13 µg g(-1) in Sonora, 0.077±0.055-0.813±0.363 µg g(-1) in Sinaloa and 0.139±0.037-0.791±0.33 µg g(-1) in Nayarit. In the muscle, values were from 0.078±0.02 to 0.539±0.09 µg g(-1) in Sonora, 0.154±0.03-0.861±0.423 µg g(-1) in Sinaloa and 0.121±0.041-1.48±0.44 µg g(-1) in Nayarit. Considering the concentrations of Hg in the muscle and the national consumption rate, shrimp farmed in NW Mexico does not represent a risk for human health (HQ<1).