MODALITĂŢI DE APRECIERE A RISCURILOR DE POLUARE A SOLURILOR CU METALE GRELE
N. FLOREA, GH. IANOŞ
ABSTRACT. – Methods of evaluation of the risks of soil pollution with heavy metals. The soil capacity to retain heavy metals in an inactive form and implicitly the soil vulnerability to heavy metals are influenced especially by the soil properties specified in table 1. But practically, for the assessment at small scale, only the following properties are taken into account: cation exchange capacity (CEC), physiologically useful volume of soil and soil reaction (pH), and to these ones the redox potential is added. The other characteristics (texture, humus content, nature of colloids, etc) can be used as alternative criteria or as supplemental criteria of evaluation; a special attention has to be payed to topographical position of soil area in territory, lower areas being generally more affected by pollution than others if all the rest of conditions are the same. The classes and subclasses of soil vulnerability to heavy metals pollution were established by combination of criteria regarding sorption and storage capacity of soil (that depends on CEC and soil depth) and heavy metals mobility or availability (that depends on soil pH and redox potential). Five classes of soil vulnerability were established from the least to the most vulnerable soil. These classes are: the higher and higher CEC and pH, very low, low, moderate, high and very high. Subclasses of soil vulnerability were defined depending on pH; three subclasses have been separated: strongly acid (a), acid to slightly alkaline (n), alkaline (b). An apart category is represented by soils having predominantly anoxic conditions, in which heavy metals sulphides may accumulate.Taking into account the criteria mentioned above, the soils of Romania were framed in different classes and subclasses of vulnerability to pollution with heavy metals, according to the properties of each soil. Based on this framing, the map of soil vulnerability to heavy metals pollution for Romania at small scale was made. It was estimated that very slightly and slightly vulnerable soils are spread on about 26% of Romania’s territory (of which 1% also with permanently anoxic conditions), the moderately vulnerable soils on 42%, the strongly vulnerable soils on 10% and the very strong vulnerable soils on 21%.