USE OF THE SEQUENTIAL-ANALYSIS FOR THE AS SESSMENT OF TRACE-ELEMENTS BONDS IN SOILS

Sequential analysis by Zeilen and Brummer was used to characterise spe cific bonds of single trace elements in soils and especially specific bonds in different soil units and their expressive anthropogenic loads and extreme geogenic concentrations. Single trace elements bonds are charactarised as follows: Cd by mobile and slightly mobilizable specie s; Mn additionally to the previous ones by occluded forms; Cu and Pb b y organic and free-Fe-oxides bonds; Mn, Zn, Be, Pb, Cu, Co and especia lly As and Cr by free-Fe-bond; As, Cr, Be, Co and Ni by prevailing res iduum. Specific features of trace elements speciation in different soi ls manifest themselves: in the prevailing of residuum in soils from th e geogenic extremes; in increased amount of Fe-oxides bonds of Zn and Cr in Fluvisols and As and Be in soils with geogenic loads; in the hig h ratio of organic bonds of Cd, Mn, Co, Zn, Ni and Cu in Chernozems, F luvisols and Cu and Pb in soils with geogenic extremes. From the ecolo gical standpoint the most important is the fraction of mobile and slig htly mobilizable species. The mobile form of Cd is negatively pi-I-dep endent and also high in soils (horizons) with absence of colloids (Are nosols, Luvisols). Negative pH-dependence is also reflected for Mn, Co , Ni and Zn. The slightly mobilizable forms indicate the intensity of anthropogenic loads of Zn especially in Fluvisols. Participation of mo bile and potentially mobilizable fractions of As and Cu is low and pos itively pi-I-dependent, which is reflected in Chernozems and Fluvisols . Mobile and slightly mobilizable species are lacking for Pb, where th e most mobile fraction is the occluded form and for Cr where it is org anically bond species. In artificially loaded soils we found out that the incorporation of trace elements into less mobile species reflects the soil vulnerability, the buffering potential of soil to immobilise the trace elements (Arenosols < Luvisols < Cambic Podzols < Chernozems ). The features of artificial contamination in the mentioned sequence were found even after five years. This proves that the process of inco rporation of mobile forms into less mobile is very slow.