Comprehensive evaluation of metal pollution in urban soils of a post-industrial city—a case of Łód´ z, Poland

Abstract

The pollution of urban soils by metals is a global problem. Prolonged exposure of habitants who are in contact with metals retained in soil poses a health risk. This particularly applies to industrialized cities with developed transport networks. The aim of the study was to determine the content and spatial distribution of mobile metal fractions in soils of the city of Łód´ z and to identify their load and sources. Multivariate statistical analysis (principal component analysis (PCA), cluster analysis (CA)), combined with GIS, were used to make a comprehensive evaluation of the soil contamination. Hot-spots and differences between urban and suburban areas were also investigated. Metals were determined by atomic absorption spectrometry (AAS) after soil extraction with 1 mol L−1 HCl. In most sites, the metal content changes in the following order: Zn > Pb > Cu > Ni > Cd. About one-third of the samples are considerably (or very highly) contaminated, (contamination factor, CF > 3) with Cu, Pb, or Zn. In almost 40% of the samples, contaminated soils were found (pollution load index, PLI > 1). All metals have a strong influence on the first principal component (PC1), whereas second principal component (PC2) is related to pH. Polluted soils are located in the downtown, in the south and east part of the city. The distribution of contamination coincides with the urban layout, low emission sources and former industrial areas of Łód´ z.