Auckland soil geochemical baseline
Maps and quality assurance and quality control (QAQC) data of trace element concentrations in soil from the Auckland Region. Point source and interpolated maps of trace element concentration in soil samples taken over the Auckland Region are included for three depths: O-depth (0-2 cm); A-depth (2-20 cm); B-depth (50-70 cm). Trace concentrations for 65 elements were measured via ICPMS undertaken at Bureau Veritas Mineral Laboratories, Vancouver, Canada. A 0.5 g split of each sample was digested in 10 ml of 1:1:1 HCl-HNO3-deionized H2O aqua regia solution in glassware for one hour in a hot water bath. Five percent HCl was used to return each sample to a standard 10 ml volume post-heating. The entire sample set was run consecutively, in batches of 40, on a single machine to minimise time-dependant variation, using a PerkinElmer ELAN 9000 ICPMS instrument. In total 487 samples were run [336 unknown samples and 151 samples for QAQC].
Steps to reproduce
Individual element data were plotted spatially using two different methodologies. The point source plots use a 10-fold, quantile subdivision. These are accompanied by graphical plots showing a classical histogram, Tukey box plot and cumulative frequency plot coloured by depth (O, A, B). The gridded plots use an inverse distance weighted interpolation at 1.5 power, fixed 8 km counting radius and a minimum of 4 sample sites. The interpolation uses a 10-fold, quantile subdivision