View the explorer below:
https://experience.arcgis.com/experience/4e6e25842cc6427ca850bdf644010922/
The Predicted Background Trace Element shapefile contains spatial information on predicted background concentrations of selected naturally occurring trace elements - arsenic, boron, cadmium, chromium, copper, lead, nickel and zinc – across New Zealand. These concentrations were developed through statistical modelling using over 2000 data points to assess the influence of land use and three explanatory data layers – parent material, soil order and land environments of New Zealand (level 1 categories) – on the concentration of the key trace elements. From this model, estimates of the rural ambient (background) concentrations (i.e., inclusive of sites where anthropogenic activities may occur although there is expected to be minimal anthropogenic additions of trace elements to the soil and no difference from true, naturally occurring concentrations) across New Zealand were made, providing a nationally consistent approach to determining background concentrations. The predicted concentrations are displayed as filled contour plots to enable visualisation of the variation in concentrations across the country. Specifically, the median, 90th, 95th, and 99th percentile of the predicted concentrations are used as the ‘cut-offs’ for concentrations within different locations. Areas identified as being at or above the 95th percentile of predicted concentrations are considered to be areas that may contain naturally elevated concentrations that may also vary significantly at smaller scales than captured in the current study, and may warrant site-specific investigations to better determine background concentrations. These data are intended to provide an assessment of background soil concentrations at locations that are being assessed for use as clean-fills, for the assessment of contaminated land or the development of site-specific ecological soil guideline values.
