The EuroGeoSurveys geochemical mapping of agricultural and grazing land soils project (GEMAS) - Evaluation of quality control results of aqua regia extraction analysis
Rigorous quality control (QC) is one of the keystones to the success of any regional geochemical mapping programme. For the EuroGeoSurveys (EGS) GEMAS (Geochemical mapping of agricultural and grazing land soils) project 2211 samples (including field duplicates) of agricultural soil (Ap, Ap-horizon, 0-20cm) and 2118 samples (including field duplicates) from land under permanent grass cover ("grazing land" - Gr, topsoil 0-10 cm) were collected from a large part of Europe, centrally prepared (air dried, sieved to <2 mm, homogenised and split into sub-samples) and randomised prior to being sent out to contract laboratories. QC consisted of (1) collection of a field duplicate at a rate of 1 in 20 field samples, (2) preparation of two large project standards ("Ap" and "Gr") for insertion between the routine project samples, (3) preparation of ananalytical replicate from each field duplicate and (4) randomisation of all samples prior to analysis. Here QC-results covering analysis of 53 chemical elements (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Pd, Pt, Rb, Re, S, Sb, Sc, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn, Zr), following an aqua regia extraction on a 15 g aliquot per sample of both sample materials, are reported. Practical detection limits and precision, as well as the analytical results for the two project standards Ap and Gr are provided for all 53 elements. All analyses were carried out within twenty days at ACME laboratories in Vancouver, Canada. No serious quality problems, other than a few occasional outliers for a number of elements (B, Ca, Cu, S and Sn) were detected, and the analytical results were accepted after investigating the reasons for these outliers.
GEMAS - Geochemical Mapping of Agricultural Soils