Concept
C1 — Crust: CRC Handbook C2 — Crust: Kaye and Laby C3 — Crust: Greenwood C4 — Crust: Ahrens (Taylor) C5 — Crust: Ahrens (Wänke) C6 — Crust: Ahrens (Weaver) U1 — Upper crust: Ahrens (Taylor) U2 — Upper crust: Ahrens (Shaw) The established abundances of chemical elements in urban soils can be considered a geochemical (ecological and geochemical) characteristic, the accumulated impact of technogenic and natural processes at the beginning of the 21st century. The figures estimate average concentrations of chemical elements in the soils of more than 300 cities and settlements in Europe, Asia, Africa, Australia, and America. Regardless of significant differences between abundances of several elements in urban soils and those values calculated for the Earth's crust, the element abundances in urban soils generally reflect those in the Earth's crust. With the development of technology the abundances may be refined. Mass fraction, in mg/kg (ppm). W1 — CRC Handbook W2 — Kaye & Laby Mass per volume fraction, in kg/L. (The average density of sea water in the surface is 1.025 kg/L) S1 — Sun: Kaye & Laby Y1 — Solar system: Kaye & Laby Y2 — Solar system: Ahrens, with uncertainty s (%) Atom mole fraction relative to silicon = 1. Due to the estimate nature of these values, no single recommendations are given. All values are normalized for these tables. Underlined zeroes indicate figures of indeterminable significance that were present in the source notation.
