Although there are several definitions of ‘soil’ depending upon the specific scientific or engineering discipline using it, I think the simplest answer in the context of pedology and agronomy is no, is it not soil since it does not participate in the processes, functions, or ecosystem services upon which we define concept of ‘soil’. In the case of soil mapping by the Natural Resources Conservation Service (NRCS) under the National Cooperative Soil Survey (NCSS) Program, map units who’s land surfaces were covered with man-made coherent materials such as asphalt and concrete (or structures) were described as miscellaneous areas and the further defined by a land type term providing a description of the nature of the surface. In the case of runways and parking lots, map unit would include a component called ‘urban land’. So, in the case of NCSS Soil Surveys, the land surface covered by coherent asphalt and concrete is not considered as soil even if underlying layers have recognizable pedogenic alteration or features.
To get back to another aspect of your question, which wasn’t asked, but perhaps alluded to by the phrase “has horizons different that the original material” is that from the standpoint of Soil Taxonomy, the material below coherent layers of asphalt or concrete would not be classified as if it were a soil currently. The 12th Keys to Soil Taxonomy clarifies the definition of buried soils allows for ‘surface mantle of naturally deposited new soil material’ (non-coherent and unconsolidated) covering soil horizons with pedogenic alteration to be called soil and classified. Depending upon the thickness of the surface mantle, the taxonomic class may or may not reflect buried diagnostic pedogenic features. This definition was further clarified and extended through recommendations of scientists working in urban and other significantly altered environments to allow for the new soil material to also include human transported and deposited earthy materials as opposed to only naturally deposited. However, in Soil Taxonomy, the material below root restrictive layers is not considered ‘soil’ in the true sense, but its nature and properties are described for consideration in the uses and management of the soil and soil landscapes.
As we extend ourselves in developing detailed soil surveys in urban areas and drastically disturbed landscapes (or subaqueous environments), perhaps this definition of ‘soil’ and what we classify should be reviewed for adequacy or completeness. It would be important to be mindful also in doing such to consider the purposes for which these surveys are made, how they are used, and for whom we perform such work. The original charge of the cooperative soil survey was to survey the lands of the US, produce maps of the soils, and to interpret the soils for their uses (generally understood to be the production of food, fiber, and timber). Almost all the lands of the US suitable for agricultural production have been surveyed to a level to meet this charge, and surveys have been expanded to meet additional and emerging uses and demands for information.
The information gathered in the soil survey is also useful for other purposes including engineering, urban development, hydrology, and ecological sciences in general. On natural or undisturbed landscapes, traditional soil survey techniques relying upon the predictive nature of the occurrence of soil based upon soil forming factors and soil forming process has allowed reliable prediction of properties and qualities across the soil landscape. In urban areas and drastically disturbed lands, the predictive models are not as reliable because of the superimposed anthropogenic manipulations, such as land surface shaping (cut and fill), addition of man-made materials, both integrated or on the surface, and the potential concentration of waste and other materials which pose hazardous to health or limit suitable uses. Such areas were initially skipped entirely or were assigned land unit terms indicating limited investigation, and therefore were not interpreted for their uses. In recent decades, more detailed surveys these areas have been conducted and interpretations developed to meet general planning needs of land uses on which they occur.
The investigation, mapping, and interpretation of anthropogenic landscapes might remais best conducted by the Soil Survey Program of the NCSS. Institutional skills and experience as well at established methods and protocols would serve the effort well. Having said that, however, there remain several considerations which scientists and policy makers need to address. Some of the considerations are as follows:
1) Is the investigation and mapping of anthropogenic landscapes which are not used for production of food, fiber, and timber within the intent authorized by the legislation? (16 U.S.C. 590a-590f U.S.C. 3271-3274.) Need to verify compliance with authorizing legislation, and amend, if needed.
2) Are the policies, protocols, and training in place to assure safety and health of investigators in environments which may be contaminated or otherwise pose hazards to health? An evaluation of such should be made before embarking on work that might endanger the short and long-term health of surveyors. Training and tools need to be acquired to assure safety.
3) Need to consider responsibilities and liabilities of the soil survey program should violations of law or serious human health threats be discovered (illegal waste dumping, hazardous spills, toxic waste sites, or other contaminations). At question might also need addressed regarding the public access or release and distribution of potentially controversial or litigious information discovered in such inventories.
4) Need to develop the procedures and protocols governing actions in conducting investigations in such environments, and development of supporting guidance in operating manuals, handbooks, classification systems, laboratory methods, and data publication and distribution systems. Specifically, the USDA-NRCS General Manual, National Soil Survey Handbook, Soil Survey Manual, Soil Taxonomy, Laboratory Methods Manual, and NASIS.
5) A final consideration might be whether the information gathered on anthropogenically created and altered lands should be folded into the traditional soil survey report, databases, and information systems. Consideration should be given to whether the investigative methods, scale of delineation, lack of predictability, and occurrence of man-made and potentially harmful materials warrants a separate system for the management and distribution if information. In addition, soil classification of such environments and materials might warrant separation and development additional taxa classes at higher levels in the classification system (Soil Taxonomy?) to appropriately separate naturally occurring and predictable soils from materials and land surfaces with significant anthropogenic alteration and unpredictable composition.
