Defining urban soil geochemical backgrounds: A review for application to the French context
Abstract
Urban soil is the “memory” of cities, as the sequence of deposited materials originates from the various stages of a city's life cycle, through a complex process of urban soil pedogenesis. This soil may consist of natural soil but also of a large variety of backfill materials, ranging from excavation materials to demolition wastes. This heterogeneous composition makes urban soil a particularly difficult object to study, for both geologists and applied geochemists. A literature review of methods used to establish the urban soil geochemical background of 77 cities in 38 countries was performed. It highlights an astonishing variety of techniques, which vary (i) from country to country (legislation, capacity of research organizations), (ii) from one project to another (budget, use of innovative techniques) and (iii) according to lead researchers and their adherence to a specific school of thought. The review raises scientific questions regarding in particular the treatment of uncertainties, and provides insight for improved methods of spatial interpolation, with special reference to the inherent uncertainty of the urban soil geochemical data.