Dialeimmasol, urban soil of pavements

Abstract

Purpose

From technic materials and constructions, new types of soils develop. A widespread example is the soil of pavements in sidewalks and partially sealed sites. Their main characteristic is a surface layer of concrete slabs and cobbles which are arranged in regular intervals and the occurrence of breaks between pavement stones with narrow gaps which are filled with fine earth. We propose the term Dialeimmasols (from Greek dialeimma, break) to designate them. These soils were rarely noticed until now and not sufficiently described in terms of soil classification. The aim of the investigation was to determine the soil characteristics and soil formation of Dialeimmasols.

Materials and methods

Six Dialeimmasols were investigated. The examples covered the area from the fringe to the center and heavy industry sites of a city. They included an underpass. To identify particles and compounds of the loose material, samples were taken in thin layers from 0 to 0.2, 0.2–1.0, 1–2, and 2–5 cm in the gaps and in the deeper part. Soil color, texture, pH, carbonate content, organic carbon, C/N ratio, iron, and manganese content were determined.

Results and discussion

Value and chroma of moist soil color and organic carbon (OC) content indicated the formation of an Ah horizon in the gaps. A distinct accumulation of very fine sand (2–6 %), silt (11–20 %), OC (2–10 %), Fe (0.6–3.4 %), and Mn ( 350–1700 mg kg⁻¹) occurred in a matrix from mainly coarse and medium sand. The pH was neutral to alkaline (pH 6.6–8.9). Slabs and cobbles, and the sand beneath them, stayed unchanged. The narrow C/N ratio of the soil in the pavement gaps indicated, under open air, an origin of accumulated fine material from other soils and surrounding vegetation. In contrast, the soil example of an underpass had a wide C/N ratio that indicated an origin of fine material from traffic.

Conclusions

Dialeimmasols belong to the new soil group which could develop from materials of pavements and an urban environment. The formation of Dialeimmasols differs distinctly from that of other soils by the unique feature of migration of fine-sized particles into a soil matrix of coarse and medium sand. Therefore, Dialeimmasols are proposed as a separate soil group in soil taxonomies. In the system of World Reference Base for Soil Resources, they belong to the Technosols. It is proposed to distinguish them from Ekranic Technosols and designate them by the principal qualifier Dialeimmic (dl) as Dialeimmic Technosols.