Mapping particulate pollution loads using soil magnetometry in urban forests in the Upper Silesia Industrial Region, Poland

Abstract

The central part of the Silesian Province, Upper Silesian Industrial Region (USIR), is the most urbanized region of Poland and one of the largest urban and industrial areas of Central Europe. The area is surrounded by a protective forest belt with some smaller urban forests, woods and parks, which are commonly used by the local population for daily and weekend recreation. Long-term exploitation of the natural resources of this land together with industrialization and urbanization has caused its physical and chemical degradation, which has in turn resulted in large geochemical and magnetic anomalies. The aim of this study was to apply the method of field magnetometry to quickly and efficiently obtain proxy data for ecological quality assessment of urban forests in the USIR. Surface measurements of magnetic susceptibility ( κ) were performed in two areas of urban forest. The first, “Makoszowy Wood” located in Zabrze (the western part of USIR) and the second area, comprised of two forests “Panewnik Forests” and “Kochlowice Forests” (in the central part of USIR), located in the city regions of Katowice, Chorzow and Ruda Slaska. The spatial variability of κ values measured in the topsoil were large (10–120 × 10 −5 SI units), requiring a relatively dense measurement network when pollution screening is undertaken. In both study areas, some local magnetic anomalies were observed, mostly located close to housing areas or local industrial or urban sources of emission. In sites of enhanced κ values, the content of some heavy metals was considerably high, often exceeding the national threshold values. Study of the vertical distribution of κ values in topsoil profiles, based on 30 cm cores, indicated that contaminants deposited over many years of industrial and urban activity have persisted in the organic horizon of forest soils, which function as an “irreplaceable environmental filter”. Such vast concentrations of contaminants in a relatively small area may be an “ecological time bomb” that may represent a true ecological hazard. Very low soil pH usually favors the release of heavy metals and other toxic elements into the soil environment, and through the soil, directly into the forest ground flora and underground water system.