SGU has a geochemical laboratory that primary supports the soil and till geochemistry mapping program as well as water chemistry and EU-mandated water quality monitoring.
SGU's headquarter in Uppsala houses a modern Inductively-Coupled Plasma Mass Spectrometer (ICP-MS) lab plus associated sample preparation facilities. This lab supports the mapping of soil, bedrock and water, but methods have been developed to support a wide range of SGUs in-house geochemistry requirements as well as special projects such as the Geochemical Atlas of Sweden. Methods are available for partial leach and total digestion analyses of soil, till and bedrock samples as well as water chemistry. Tailored routines can be developed to address specific geochemical questions. To provide quality control, SGU has developed its own in-house standards for both till and bedrock.
Three analytical methods have been developed for soil and till samples, two partial leach methods and a near-total digestion method. The same near total digestion method is available for bedrock samples. The partial leach methods provide enhanced concentrations of trace and accessible elements, providing important information for prospectors as well as the bio-availability of elements while the near total digestion method provides total concentration data. Comparison of the two types of data allows determination of where individual elements sit within the sample, important information for both the mining industry and environmental/agricultural assessments.
HNO3 Partial Leach
The HNO3 Partial Leach method is based on an old Swedish Standard method (SS 02 83 11), modified for large scale (multi-thousand sample) projects and for use with modern equipment. Samples are leached in Nitric Acid in open containers on a hotplate. Currently we analyse for 52 elements (Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Rb, Sr, Y, Ba, La, Ce, U, Li, Be, B, Sc, Co, Ni, Cu, Zn, Ge, As, Se, Zr, Nb, Mo, Ag, Cd, Sn, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Tl, Pb, Bi and Th.) This is the primary method for SGUs national geochemistry mapping program and has been certified by the Swedish National Accreditation board (SWEDAC) for the following elements: As, Ba, Cd, Cr, Co, Fe, Mn, Ni, Pb and V.
Aqua Regia partial leach
Some elements of particular interest to Swedish industry are hard to analyse with a simple HNO3 leach. As such we have developed an Aqua Regia partial leach method utilising the more aggressive blend of Nitric and Hydrochloric acid. Currently we analyse for the following elements with this method: Au, Ta, Te, Sb and Rh. As, Cu, Mo, Ag, Cd, Bi and U are analysed by both acid leach methods to provide an internal control on samples.
The Near-Total Digestion method, also known as the 4-acid digestion method provides a means to analyse almost all the elements in a sample to a high degree of accuracy. A combination of Nitric, Hydrochloric, Perchloric and Hydrofluoric acids are used to bring almost the entire sample into solution, where it can then be measured by the ICP-MS. While all of the above mentioned elements can potentially be analysed for, the method is currently only calibrated for the following 38 elements: Ti, Al, Fe, Mn, Mg, Ca, Na, K, P, Ni, Cr, Sc, V, Ba, Rb, Sr, Zr, Y, Nb, Cu, Zn, Pb, Th, Nd, U, La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.
We have methods to analyse the same suite of elements in ground and surface water samples down to parts per billion levels. By comparison with till and bedrock chemistry this data helps establish natural background levels of chemicals in groundwater. Potentially hazardous levels of elements can be identified and sources, natural or man-made, can be identified. This data contributes to SGUs Urban Geochemistry studies as well as routine EU mandated monitoring at a national scale.