METALES PESADOS EN SUELOS DE LA PLANICIE COSTERA DEL RÍO DE LA PLATA, PARTIDOS DE ENSENADA Y BERISSO

Heavy metal records from different soil horizons within the Planicie Costera from the locality of Gran La Plata, do not show, in general terms, a great dispersion or values that are greater than the regional reference values given by other authors. The maximum concentration levels, considered ecotoxic in soils of the Pampean region, are 50 mg kg-1 for Copper, 100 mg kg-1 for Lead and 150 mg kg-1 for Zinc. If we consider the averages for all the studied topsoils and subsoils, we find the following values: Cu: 45.73 mg kg-1, Zn: 105.8 mg kg-1 and Pb: 34.38 mg kg-1, with decreasing values of standard deviation in the order Zn-Pb-Cu of 130.81- 51,12- 24.75, respectively. The few exceptions are located close to the urban areas with intense industrial activity, as in the area of proximity of the Dona Flora stream in the locality of Ensenada with striking high values of Cu: 155 mg kg-1, Zn: 283 mg kg-1 and Pb: 134 mg kg-1. The soils of the Coastal Plain have two main textural types, sandy soils close to the coastal line and smectite-clayey dominant soils within the inner muddy Plain. In both cases, there is almost no vertical variation of the concentration of these elements among horizons. For the sandy soils, this observation may be explained by the sandy composition and relative young age of the soils developed close to the coast line with low metal retention. In the second case, the lack of variability is explained by the clay dominant composition of the soil substrate and the presence of organic matter that favours high metal retention.