Rauch, J.N. (2011), Global distributions of Fe, Al, Cu and Zn contained in Earth's derma layers

Journal of Geochemical Exploration, 110 (2), pg. 193-201. doi: dx.doi.org/10.1016/j.gexplo.2011.05.008

Recent efforts to understand Earth's elemental metal cycles have produced estimates for the integrated human-natural system metal mass reservoir stocks and inter-reservoir metal mass flows. These globally comprehensive metal cycles, called anthrobiogeochemical cycles, have been generated for Al, Fe, Cu, Zn, Ni, Pb, Ag, and Cr. While useful in visualizing the totality of Earth's metal cycle system, these global cycles lack the specificity that spatial resolution of these cycles can provide. Spatial resolution both informs global value estimation and provides a deeper understanding of the heterogeneity underlying the global estimate. SedDB was among many geochemical databases utilized to improve the accuracy and usefulness (via spatial disaggregation) of quantifying the natural metal stock reservoirs of Earth's anthrobiogeochemical cycles. This particular publication focuses upon the global maps at 1° × 1° that were produced to estimate the concentrations and masses of Fe, Al, Cu, and Zn contained in Earth's sediments and soils. The global maps were generated by inverse distance weighting (IDW) and cokriging, allowing geospatially weighted mean global concentrations for these metallic micronutrients to be estimated. These geostatical techniques were applied as follows: IDW of sediment samples produced sediment metal concentration maps; cokriging upon an underlying parent rock dataset composed of both surface bedrock and sediment samples produced global soil maps. The resulting information contained in these maps was utilized to produce new, independent estimates for the global mean concentrations in continental sediments (Fe = 3.1 wt.%, Al = 6.1 wt.%, Cu = 45 μg/g, Zn = 86 μg/g) and soils (Fe = 2.5 wt.%, Al = 3.9 wt.%, Cu = 17 μg/g, Zn = 50 μg/g). While Fe, Al, and Cu concentrations in continental sediments confirm previous estimates, Zn concentrations are found to be relatively higher, ~ 20 μg/g above prior estimates. The maps also highlight those areas of the globe for which little to no readily accessible, public data are yet available to help constrain sediment and soil metal concentration estimates.

-J. Rauch