Nehézfémek eredetének elkülönítése városi kerti talajokban, Szeged példáján | Separating the origin of heavy metals in urban garden soils in the case of Szeged

Urban garden soils may become contaminated with toxic and potentially toxic heavy metals a consequence of their cultivation as well as from typical urban contamination sources (such as atmospheric deposition, the metal pollution effect of traffic, domestic heating, etc.). Therefore, determining the origin (lithogenic, pedogenic, anthropogenic) of the metal content measured in these soils is a major challenge for two reasons: 1) the diversity of possible contamination sources, and 2) the influence of anthropogenic ac-tivities on these soils. The research focused on the study of the cumulative effects of heavy metal pollution originating from urban environmental impacts and garden cultivation, using Szeged as an example. In addition to the assessment of the heavy metal pollution of suburban garden soils, various methods were combined in order to distinguish the group of metals accumulating in garden soils as a result of anthropogenic activities. The present study describes how the combined study of enrichment factors and the vertical distribution of metal concentrations helps to determine the origin (lithogenic, pedogenic, anthropogenic) of each element. Based on the vertical distribution of heavy metal concentrations measured in the garden soil profiles, none of the studied elements can be considered as of purely lithogenic origin in garden soils as certain soil properties play an important role in their distribution. The vertical distribution of Pb, Zn, Cu and Cd concentrations is modified by the organic matter content of the soil, while the vertical distribution of Ni, Cr and Co concentrations is modified by the mineral colloid content of the soil. Based on the enrichment factors (EF) calculated with the help of the reference horizon and the reference element (Ti), it can be stated that As, Ni, Co and Cr do not accumulate in garden top-soils (EF ∼ 1) and that the lithogenic background and pedogenic processes determine the topsoil concentrations of these elements. However, Cu (EF ∼ 4.2), Zn (EF ∼ 2.7) and Pb (EF ∼ 2.5) are significantly enriched in garden topsoil. In the case of Zn and Pb this can be attributed not only to natural, pedogenic processes but also to anthropogenic activities in almost every garden, while anthropogenically induced Cd enrichment is limited to only a few gardens.