engleski

MAGNETIC PROPERTIES OF TOPSOILS IN CROATIA

Magnetic susceptibility (MS) of soils and paleosols indicates the formation of secondary ferrimagnetic minerals (SFM) and pedogenic processes. MS measurements can relatively fast and non-destructively characterize the concentration, mineralogy, and grain size of magnetic minerals present in samples (HATFIELD, 2014 ; PETERS & DEKKERS, 2003). The soil characteristics are influenced by variations in iron mineral forms, and it can give clue to the processes of pedogenesis (DEARING, 1996). Topsoil has been identified as an environment in which ferrimagnetic materials are actively produced. Secondary magnetic minerals (magnetite/maghemite) are mostly ultrafine grained and contain a significant superparamagnetic (SP) component (<0.03 µm). The analysis of surface (0-10 cm depth) and sub-surface soils (20-30 cm depths) in a dataset created from more than 750 locations in Croatia (MIKO et al., 2017) have been performed through measurements of low field mass specific MS (Xlf), mass specific and frequency-dependent MS (Xfd). The aim of the study was to determine the spatial distribution of MS. The MS data set is combined with data for geochemistry, geology and soil type in order to determine the main source of magnetic particles. Data can then be used for provenance studies of soil and erosional processes (HATFIELD & MAHER, 2008), climate reconstructions (MAHER, 2011 ; GEISS et al., 2008) as well as evaluation of historical landuse and anthropogenic soil pollution (HOFFMANN et al., 1999 ; MITCHELL et al., 2010). Measurements are also used in the landmine-affected regions because of the effect of soil MS on metal detectors (HANNAM & DEARING, 2008). Maps created with the soil MS data set in Croatia show two clearly differentiated distributions – Pannonian region versus Dinaric area of Croatia (Figure). Differences exist due to the geological sub- division of Croatia and its associated main soil types: the Mesozoic carbonate rocks of the Dinaric-Coastal karstic region with dominant red soils and calcocambisols versus the Pannonian region with dominant cambisols, luvisols and gleysols mostly developed on clastic Neogene and Quaternary sediments (HGI, 2009, BOGUNOVIĆ et al., 1996). Summary data shows that soils developed on carbonate rocks have higher MS values compared to soils of the Pannonian region (Figure). Anthrosols also have elevated MS values. Magnetic properties of soils in the karstic area are dominated by the presence of nanoscale SP SFM grains produced in situ. Soil-derived magnetite gives major contribution to the magnetic enhancement in red soils. Primary ferrimagnetic minerals derived from geological sources dominate magnetic properties in only a minority of localities (mountainous areas composed of magmatic and metamorphic rocks). This is the first attempt to produce a soil magnetic susceptibility map of Croatia that covers all dominant soil types in Croatia. This work was supported by the Project “Promjena zaliha ugljika u tlu izračun trendova ukupnog dušika i organskog ugljika u tlu te odnosa C:N” funded by Croatian Environment Agency and Project “Basic Geochemical Map of the Republic of Croatia”(181-1811096-118).

Magnetic susceptibility, Croatian topsoil, ferromagnetic minerals, karst, pedogenesis

nije evidentirano