SEGH Articles

# Urban soil of Athens, Greece: Local geology beats human pollution on trace elements

04 June 2014
Bearing in mind the historical absence of heavy industry within the Greater Athens and Piraeus area, the tested hypotheses was that local geology is important in controlling the distribution of potentially harmful trace elements in urban soil.

Bearing in mind the historical absence of heavy industry within the Greater Athens and Piraeus area, the tested hypotheses was that local geology is important in controlling the distribution of potentially harmful trace elements in urban soil.

The first geochemical baseline study of surface soil in Athens, based on a systematic sampling survey covering the Greater Athens and Piraeus area, was recently performed by the Laboratory of Economic Geology and Geochemistry, University of Athens. In the study, the contents of the major elements Fe, Al, K and Ca, and potentially harmful elements Ni, Cr, Co, Mn, As, Pb, Zn, Cu, Cd, Sb and Sn were determined.

Athens, Greece is a European city with a very long history. The area has been continuously inhabited for more than 7,000 years and provides an example of early urbanization in the ancient world. However, unlike most European capitals, the urbanization of modern Athens was not related to the Industrial Revolution. The city experienced rapid population growth from ~400,000 people in 1925 to > 1,000,000 by 1950.  The population increase of modern Athens is marked by the return of Greek refugees from Asia Minor in the 1920s after World War I, and extensive internal migration after World War II. Today, the urban area of Greater Athens and Piraeus has a population of ~ 3.2 million over an area of 412 km2. This constitutes ~ 1/3rd of the Greek population. In addition, this area is the center of economic and commercial activities for the country.

Principle Component Analysis and Cluster Analysis, combined with analysis of soil heterogeneity and spatial variability, were implemented in order to distinguish the sources of elements and their classification as geogenic or anthropogenic. It was found that the major factor controlling variability of the chemical composition of surface soil was the bedrock chemistry, resulting in a significant enrichment in concentrations of Ni, Cr, Co and possibly As. Greek soil is naturally enriched in Cr, Ni, Co and Mn as a result of the widespread occurrence of basic and ultrabasic rocks. Furthermore, elevated As concentrations in soil and natural waters have been linked to metamorphic rocks in Greece.

Anthropogenic influences were also significant, controlling a spectrum of elements that are typical of human activities, i.e. Pb, Zn, Cu, Cd, Sb, and Sn. The highest concentrations of the classical urban contaminants were observed in the surface soil from roadside verges and in the older parts of the city, as well as the densely populated areas. Spatial distribution patterns of PHEs demonstrated an increase in concentrations of the anthropogenically induced metals towards the city core and the port of Piraeus. On the contrary, the naturally derived Ni, Cr and Co are mainly enriched in the periphery of Athens Basin.

Taking into account the salient enrichment of geogenic PHEs in Athens soil, comparing with concentrations measured in other cities around the world, this study provides base for further research into PHE mobility and bioaccessibility. This work is also important for under the current economic conditions the development of urban agriculture is an emerging initiative of several municipalities. The results of the study are presented in a publication in the Science of the Total Environment: http://dx.doi.org/10.1016/j.scitotenv.2014.02.133

Dr. Ariadne Argyraki, Assistant Professor in Geochemistry, University of Athens (argyraki@geol.uoa.gr)

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