1. INTRODUCTION Soil is a vulnerable geological medium, which sustains the bulk of human activities including, among others, the food production as one of the most important. In the age of increasing pollution and devastation of human environment the soil protection deserves every respect and mindfulness, particularly because of its vital impor- tance not only to the human beings but also for the sus- tenance of each facet of life on this planet as a whole. In order to trace the increasing human contribution to Geochemical Baseline Mapping of Soils Developed on Diverse Bedrock from Two Regions in Croatia Slobodan MIKO, Josip HALAMI∆ , Zoran PEH and Lidija GALOVI∆ overall contamination of the planet, particularly by the chemical elements harmful to health, it is necessary to determine the natural content of major and trace ele- ments in soils on the regional scale. Up to the present time there was no methodical research in our country as regards finding a solution to this burning worldwide problem. In due time, this work was animated and sup- ported by the Ministry of Science under the project of Geochemical Map of The Republic of Croatia with the scope to detect a pollution problem on a regional scale and pinpoint some target areas in the country where adversities for its inhabitants threaten to become most pronounced. Geochemical research has shown a much greater natural variability among almost all elements in soil, irrespective of the soil type, when contrasted to the stream sediment (REIMANN, 1988). This is a fact that allows reduction of sampling density, fitting it more appropriately into the regional scope of investigation which can be implemented successfully either on car- bonate or non-carbonate geological bedrocks. Sampling design and analysis have been performed to be comple- ment with recommendations issued by IGCP (DARN- LEY et al., 1995) and FOREGS (SALMINEN et al., 1998), which classify soil into the first group of sample materials (regolith) with the widest geochemical applic - ability. This paper is aimed to establish the geochemical baselines for a set of chemical elements in the two geo- graphically separate parts of the country whose soils originated on different geological substrates: 1) on pre- dominantly non-carbonate (non-karstic) terrains (north- western Croatia); and 2) predominantly carbonate (kar- stic) terrains (southern Dalmatia). Geochemical base- lines, or natural background concentrations for a partic- ular element refer to the natural variability of its con- tents in the secondary (surficial) environment (soils, stream, overbank, floodplain or lake sediments). The geochemical baseline, which has been defined within the IGCP 360 project Global Geochemical Baselines, is of essential importance in environmental legislation, which prescribes limits for heavy metals in contaminat- ed land and other surficial materials such as defined by environmental authorities. This is additionally compli- cated by regional geochemical data showing that natur- al background concentrations vary widely due to the Geologia Croatica 54/1 53 - 118 14 Figs. 5 Tabs. 45 Pls. ZAGREB 2001 Key words: Geochemical baseline mapping, Soils, Environmental geochemistry, Heavy metals, Pollu- tion, Karst, Carbonate and non-carbonate bedrock, Factor analysis, Croatia. Institute of Geology, Sachsova 2, P.O.Box 268, HR-10000 Zagreb, Croatia. e-mail: igi-zagreb@zg.hinet.hr Abstract The comparison of contents and distribution maps for Al, As, Ba, Ca, Co, Cr, Cu, Fe, La, K, Na, Ni, Mg, Mn, P, Pb, Sc, Sr, Ti, Th, V, Y, Zn and Hg in the topsoil cover of two typical regions are given. One is a carbonate bedrock (karst) dominated region (southern Dalmatia) and the other a non-carbonate bedrock dominated region (NW Croat- ia). The results imply that the soils developed on carbonate bedrock have higher mean values of almost all elements excluding K, Na, Mg and Ba, which are lower in carbonate terrains. In comparison with the non-carbonate terrains, for the carbonate terrains the following ele- ments have higher mean concentrations: Al, As, Co, Cu, Fe, La, Mn, Pb, Ni, Mn, Th, V, Cr, Zn, Zr and Nb, while Sr, P and Ti have similar contents. Approximately 4% of the sites can be considered as moder- ately enriched (polluted) in Pb, either from mining activities or air- borne deposition. Only a limited number of sampling sites can be directly linked with mineralization. The derived factors are usually interpreted as associations of elements that imply a common source or behavior in regard to geogenic or anthropogenic influences. It was found that difference between the northwestern Croatia and southern Dalmatia is not expressed only by concentration differences but also by element associations. Five factor models accounting most of the data variability seemed appropriate to portray the geochemical vari- ability within the topsoil of both regions. 54 Geologia Croatica 54/1 differences in bedrock geology and the origin of the soil cover, as is the case in the Mediterranean region of Croatia. In the region of southern Dalmatia the geo- chemistry of the topsoil cover distinguishes between the two major environments; the southern Adriatic islands (Mljet, KorËula, Hvar, and BraË to some extent) and the mainland which consists of the two somewhat less pro- nounced environments: alluvial valleys-karst poljes and carbonate bedrock (PEH & MIKO, 1999). 2. GEOLOGY AND PEDOLOGY The north-western part of Croatia (Æumberak Mt., Pokuplje, Posavina upstream of Sisak, Medvednica Mt., Hrvatsko Zagorje, Podravina to the east of Varaædin, and Meimurje) is bordered to the west and north by the Croatian-Slovenian borderline, to the south by the river Kupa, and to the east by the Gauss map Y coordi- nate line of 5612500 (approximately the line connecting the cities of »akovec and Sisak). The southern Croatian territory is bounded to the west by the line extending from Split to the PeruËa Lake. Its northern fringe is defined by the state boundary towards Bosnia and Herzegovina. To the east the area is narrowing against the Montenegro border at the cape of Oπtra (Fig. 1). The investigated territories belong to different geot- ectonic complexes. The northwestern Croatia fits into the Supradinaric palaeodynamic unit with elements of Alpine structures. This area is also known as the Inner Dinaride Belt (HERAK, 1986; HERAK et al., 1990). On the other side, recent tectonic setting of the southern Croatia is a consequence of the disintegration of car- bonate platform areas, which resulted in the extended, highly elevated karstic terrain, also known as the Outer Dinarides. The complex geotectonic evolution of these belts is reflected in prevalence of “non-carbonate” lithology in NW Croatia, while its southern portions are built chiefly of carbonate sedimentary rocks. In the former case a variety of rocks occurs ranging from Devonian (Silurian?) to Quaternary ages. The main bodies of the mountain ranges Æumberak, Med- vednica, Kalnik, IvanπËica, and some other smaller ranges, which are a minor part of the whole region of NW Croatia, consist mainly of Palaeozoic and Meso- zoic rocks (para-metamorphic rocks, ortho-metamor- phic rocks, carbonate sedimentary rocks, igneous rocks and clastic sedimentary rocks). A major portion of this territory consists of Tertiary rocks (limestones, marls, clastites, igneous rocks) and Quaternary rocks (mostly alluvium sediments of the rivers Sava, Drava, Mura, Kupa, and their tributaries) (Fig. 2). The geological setting of the southern part of Croat- ia area resulted from a vigorous tectonic activity since the Palaeozoic times. In its western part structures appear more compact, while to the east they display strong neotectonic faulting and partitioning into the minor blocks. Throughout the area limestones and dolo- mites prevail which, due to tectonics and later karstifi- cation, manifest various karstic phenomena. The clastic flysch-type sedimentary rocks, mostly marls, also occur, although in a rather limited quantity. The occur- rence of other siliciclastic rocks, outside the flysch complex, is extremely rare and related only to the Palaeozoic tectonic windows far to the northwest. The stratigraphic sequence can be traced from the Palaeo- zoic to the Quaternary (Fig. 2). The investigated areas are considerably contrasted not only by their geological settings but also in their cli- matic characteristics, which resulted in formation of the variety of soil types. Most soils in the northern part of Croatia (Fig. 3) are characterized by high moisture con- tent as a consequence of high precipitation, flooding and high groundwater levels. Water can saturate the upper part of the horizon inducing the waterlogged con- ditions, which induce the development of hydro-mor- phic soils (©KORI∆, 1986). In contrast, the southern parts of the country are covered by soils that are moist- ened only by the precipitation input, without additional saturation. Infiltration through the soil and into the ground is free and unimpeded. The major area of the NW Croatia is covered by soils from the group of gleys such as eutric, mollic and calcic gleysols (©POLJAR, 1999). These can be found in the valleys of the rivers (Sava, Drava, Mura, Sutla, Krapina, and Kupa). The second most frequent group of soils consists of stagnic and podzololuvisols, which cover the plains between Æumberak Mt., VukomeriËke Gorice and Zagreb as well as along the Sava River downstream to the town of Sisak. Besides, these soils are spread in the belt between the Sava river on the one side, and IvanπËica, Kalnik and MoslavaËka Mountains on the other. The third major soil group, represents the mollic and calcaric fluvisols, particularly in the wide valleys of the Sava and Drava rivers immediately along their course. More rarely other types of soils occur, such as rendzic, mollic, umbric and dystric leptosols; eutric, dystric, humic and chromic cambisols; and albic, gleyic and chromic luvisols. About 2% of the collected samples belong to the urban areas of Zagreb, Sisak and Varaædin. In contrast to the northern Croatia, the karst bedrock in the southern Dalmatia is dominantly covered by the coloured soils, terra rossa - chromic cambisols, which cover the largest part of the coastal terrain and most of the islands. The next important group of soils consists of rendzic and mollic leptosols, which can be traced in the highest mountain reaches of the Mosor, Biokovo and Dinara Mountains as well as on the most elevated areas of the island of BraË and the Peljeπac peninsula. Besides, these soil types cover a narrow strip of the coastal area from Split eastward to PloËe. Minor patch- es of the territory are overlain by the more rare soil varieties such as aric anthrosols (Sinjsko Polje, the zone along the Neretva river, and portions of the islands of BraË, Hvar and KorËula), mollic and calcaric fluvisols 55Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... Fig. 1 Map of Croatia with location of studied areas (northwestern Croatia and southern Dalmatia). 56 Geologia Croatica 54/1 Fig. 2 Geological map of Croatia (VELI∆ & VELI∆, 1993). 57Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... Fig. 3 The soil map of Croatia (modified from ©KORI∆, 1986). (Imotsko and VrgoraËko Polje together with the valley of Neretva), chromic luvisols (smaller area between the Imotsko and Sinjsko Polje); and fibric and terric his- tosols (the swampland along the Neretva River). Much of the soils on flysch bedrock, and more rarely, on car- bonate terrains are anthropogenized and transformed into rigosols. 58 Geologia Croatica 54/1 3. MATERIALS AND METHODS 3.1. Sampling and sample preparation Soil samples from coastal and inland terrains were col- lected at a density of 1 site/25 km2 in a regular grid with the initial point of the grid for the whole country locat- ed in Istria near the city of Rovinj (PIRC et al., 1991). Detailed protocols of the sampling procedures to be applied for this region are given by PIRC et al. (1991), and PROHI∆ et al. (1997, 1998), as well as by MIKO et al. (1999), PEH & MIKO (1999), HALAMI∆ & GALOVI∆ (1999). All of the above protocols are sum- marized in the Guidelines for the Geochemical Map- ping of Croatia (HALAMI∆ et al., 2000), which only slightly differ from the recommendations given by DARNLEY et al. (1995). The tolerated dislocation of sampling from the sampling cell nodes was 5%. In northwestern Croatia a total of 293 soil samples were collected which is equivalent to a surface of approxi- mately 7,350 km2, in southern Dalmatia 404 (225 on the 5x5 km grid and 179 on the 1x1 km grid) soil sam- ples collected cover an approximate surface of 5,600 km2 (Fig 1). The soil samples were taken at each sampling site from 5 shallow pits (the Amo-mollic horizon, from the depth of 0 to 20 cm) and one composite sample was prepared from each sampling site. 3.2. Analytical procedures and quality assurance The dry soil samples were sieved to pass 63µm screen and were analyzed after near total (a hot acid mixture: H C l O4- H N O3-HCl-HF at 200°C) decomposition for 35 elements by ICP-AES in the ACME Labs in Vancou- ver. The following elements were analyzed: Ag, Al, As, Au, Ba, Bi, Be, Ca, Cd, Co, Cr, Cu, Fe, La, K, Na, Nb, Ni, Mg, Mn, Mo, P, Pb, Sc, Sb, Sn, Sr, Ti, Th, U, V, W, Y, Zn, and Zr. The analytical results for Ag, Au, Bi, Be, Mo, Sb, Sn, U and W were not used since more than 80% of the samples contained concentrations of these elements below the instrumental detection limits. Single element geochemical maps were constructed only for the remaining elements with concentrations above the detection limit (usually more than 90% of the analyzed samples). Accuracy of analyses was controlled with the aid of certified geological reference materials, i.e. soils from the USGS; GXR-2, GXR 5, and SJS-1. The accuracy for most elements analyzed in reference soil materials is in the range of ±10 % of the certified values (PEH & MIKO, 1999; HALAMI∆ & GALOVI∆, 1999). The precision of the analyses was determined by repeated analysis of both certified reference samples and ran- domly selected soil samples, the resulting coefficient of variation in average is approximately 5% (PEH & MIKO, 1999; HALAMI∆ & GALOVI∆, 1999). The field data and the chemical analyses are stored as a database, which besides the chemical data also contains 20 parameters that describe topographic, geo- logic, geomorphologic and pedologic features of the sampling sites and samples. All collected samples are preserved and stored for future use. The single-element geochemical maps were produced with the aid of the SURFER mapping software. Griding was performed by linear kriging (ISAAKS & SIRVASTAVA, 1989) with grid cell resolution of 2 x 2 km. 3.3. Evaluation of basic statistical parameters and multivariate statistics The evaluation of basic statistical parameters for all ele- ments was performed on the analytical data from the whole database. These parameters are given in Table 1, while others are displayed together with frequency dis- tribution histograms presented on each individual map. Also the nonparametric distributions of each element are given as the 10th, 25th, 50th, 75th, 90th, 95th, 98th and 99th percentile values, which are present as ele- mental concentration distribution contour boundaries on the maps. For decades both exploration and environ- mental geochemical studies frequently use R-mode fac- tor analysis as a multivariate mathematical technique to reveal the underlying structure of a specific set of data (DAVIS, 1986). As such, it is commonly used as a tool of data reduction, with a purpose of clearer insight into the basic relationships among variables (R-mode), or among samples (Q-mode). A simply structured factor model, which contains only a few heavily loaded fac- tors, is always indicative of the strong dependence among elements, and therefore as such, is used to com- pare the geochemistry of the studied regions. Factor analysis was performed for the data set of each region separately with the aim to observe similarites of geo- chemical behavior of the analyzed elements and to allow a more straithgfoward insight into the structure of the data. All statistical analyses were performed with the STATISTICA software. 4. RESULTS AND DISCUSSION 4.1. Element distributions In the secondary environments the geochemical back- ground varies regionally with the basic geology, as is indicated by the results of geochemical mapping per- formed in the Panonnian and the karst regions of Croat- ia. The results of the geochemical baseline mapping program together with the accompanying full data bases for NW Croatia and southern Dalmatia is summarized in atlases of single element maps (HALAMI∆ & GA- LOVI∆, 1999; PEH & MIKO, 1999; MIKO et al., 2001). The summary statistics for Croatian soil geo- chemical data obtained so far during the geochemical mapping program is given in Table 1. For comparison 59Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... the mean concentrations of elements in Slovenian soil (ANDJELOV, 1994) are also presented since the data were obtained in the same manner (sampling and ana- lytical procedures were the same). Also for a clearer insight a comparison of the distribution of both major and trace elements in the analyzed soils is given on box and whisker-plots in Figs. 4 (major elements) and 5 (trace elements). From the summary data in Table 1 it is visible that most of the elements (Al, As, Co, Cu, Fe, La, Pb, Ni, Mn, Th, V, Cr, Zn, Zr and Nb) have higher median values in soils developed on carbonate bedrock with the exception of Na, K, Fe and Ba, which have higher concentrations in soils of the northwestern part of Croatia. Sr, P, Mg, and Ti manifest a similar range of contents in both regions. The non-outlier ranges in Figs. 4 and 5 show that the trace elements have the largest variability of content in soils developed on carbonate bedrock in southern Dalmatia, while the variation in northwestern Croatia is far less expressed. The samples from western Croatia (the regions of Gorski Kotar, Lika and Kordun in general, MIKO et., al., 2001) have ele- ments of a transition zone since the soils that are devel- oped on the limestones on the Karlovac plateau are derived (as a result of aeolian transport) from material that originates from the northwestern Croatia. This is expressed by an intermediate variation between the oth- er two geographically distant and geologically different regions. The relatively small variation in the content of trace elements in soils of northwestern Croatia is proba- bly due to the relatively limited area that was sampled. The major elements (Fig. 4) in all regions show a simi- lar degree of variation. A short description of the indi- vidual elements presented and corresponding geochem- ical maps is given in the text that follows. Aluminium (Al) Aluminium content in soils (Plates 1 & 2) is mainly controlled by the clay content, the parent lithology and the content of carbonates, which is best illustrated on the plot CaO vs. Al2O3 in Fig. 6. The data for western Croatia are given for comparison (MIKO et al., 2000, 2001). Aluminum ranges from 1.46% to 10.84% with an arithmetic mean of 6.89% in northwestern Croatia whereas in southern Dalmatia its contents range from 0.82% to 14.04%. The lowest aluminum contents are found in soils that contain higher carbonate contents such as rendzinas on dolomites and limestones, soils developed on flysch bedrock and on carbonate rich NW Croatia S Dalmatia Croatia Slovenia (ANDJELOV, 1994) # samples median median median mean mean Al (%) 1143 7.33 7.94 7.32 7.23 6.69 As (mg/kg) 984 14 14 12 14 8.17 Ba (mg/kg) 1151 330 279 326 345 371 Ca (%) 1153 1.24 2.29 1.41 3.77 2.58 Co (mg/kg) 1152 14 18 15 15 28 Cr (mg/kg) 1153 94 112 96 104 90 Cu (mg/kg) 1153 34 45 34 49 28 Fe (%) 1153 3.67 4.13 3.67 3.68 3.75 Hg (mg/kg) 293 60 - 60 94 - K (%) 1024 1.21 1.21 1.36 1.34 1.23 La (mg/kg) 1151 49 50 43 45 31 Mg (%) 1152 0.68 0.82 0.75 1.09 1.35 Mn (mg/kg) 1153 780 1009 770 844 1044 Na (%) 1151 0.49 0.28 0.43 0.51 0.52 Ni (mg/kg) 1153 59 79 59 65 53 P (%) 1024 0.062 0.071 0.064 0.076 0.07 Pb (mg/kg) 1153 43 53 42 46 38 Sc (mg/kg) 1023 11 12 11 11 13 Sr (mg/kg) 1153 86 102 98 120 98 Th (mg/kg) 1024 13 17 13 14 11 Ti (%) 1153 0.40 0.41 0.41 0.39 0.38 V (mg/kg) 1153 118 143 117 125 118 Zn (mg/kg) 1153 91 109 94 101 113 Table 1 Summary statistics for the analyzed elements in topsoils from Croatia (data from Western Croatia from MIKO et al., 2001). 60 Geologia Croatica 54/1 alluvium deposits along the Sava River near Zagreb, or in karst poljes which contain lacustrine sediments. Higher contents of Al are found in soils overlying mag- matic and metamorphic rock complexes. In the region of southern Dalmatia the terra rossa soils regularly have more than 8% of Al as a consequence of high clay con- tent, while the alluvial and marsh soils due to dilution by carbonates have concentrations lower than 6%. The effect of carbonate dilution is best viewed on the plot CaO vs. Al2O3 (Fig. 6). Arsenic (As) The distribution and contents of arsenic (Plates 3 & 4), which is considered a potentially toxic element, ranges in northern Croatia from 1.8 to 52.7 mg/kg with an average of 10 mg/kg. The soils developed on carbonate bedrock in southern Dalmatia have a similar range of contents but in average contain 16 mg/kg of As. In gen- eral there is a high correlation of As with the Al content in soils indicating that the clay content controls the As content in the soils. Therefore alluvial soils and soils derived from flysch have low contents of arsenic, while terra rossa has elevated concentrations of As. Although most of the high concentrations of As can be linked with the underlying lithology in areas of intensive agri- culture (Meimurje), agrochemicals as a source cannot be excluded. In Æumberak Mt. the As can partly be derived from the sulphide mineralization that occurs in the region. Barium (Ba) The barium content (Plates 5 & 6) in the analyzed soils from both regions ranges from 40 to 3,000 mg/kg. Bari- um has a geochemical affiliation for potassium (Fig. 7), especially in feldspar, so the weathering products also retain this relationship. High concentrations of Ba were found in Æumberak Mt., where it is related to sulphide mineralization. In some parts of alluvial plains of the rivers Sava (near Sisak), Drava and Krapina the con- tents of Ba exceed 500 mg/kg. The mean Ba content of Fig. 4 Concentration ranges of major elements in soils from southern Dalmatia, western Croatia and northwestern Croatia, median; non-outlier minimum, non-outlier maxi- mum (data for W Croatia from MIKO et al., 2000, 2001). Fig. 5 Concentration ranges of minor and trace elements in soils from southern Dalmatia, western Croatia and north- western Croatia, median; non-outlier minimum, non- outlier maximum (data for W Croatia from MIKO et al., 2000, 2001). 61Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... soils from the Pannonian part of Croatia is 424 mg/kg, whereas from southern Dalmatia is 324 mg/kg. Soils developed on carbonate clastic rocks and alluvial and marsh soils in the karst regions have Ba contents below 200 mg/kg, which also reflect the effect of carbonate dilution. The analysis of Ba data of soils (MIKO et al., 2000) for the Adriatic Islands Mljet, KorËula, Hvar and BraË indicate enrichment of this element, as do the recent sediments from the southern part of the Adriatic Sea (DOLENEC et al., 1998). Barium together with K and Na, seems to be the key element that determines the geochemical provinces in Croatia, which are the karst region, with low contents of these elements, the transi- tion zone of the Karlovac plateau, and northwestern Croatia with high concentrations of Ba, K and Na. Calcium (Ca) Calcium (Plates 7 & 8) as a major element and nutrient ranges from 0.07 to 14.70% in northwestern Croatia, and from 0.39% to 35.09% in southern Dalmatia with mean concentrations of 2.08% and 6.02% respectively. The lowest concentrations of Ca were determined in soils developed on loess deposits and gleyic soils in northwestern Croatia and in southern Dalmatia in terra rossa and brown soils developed on limestones. Rendzi- nas developed on limestone, dolomite and flysch due to the large amount of fine carbonate detritus regularly contain more than 3% of Ca. The effect of dilution by carbonates is illustrated by the scatter plot CaO-Al2O3 in Fig. 6. High calcium contents characterize soils developed on floodplain sediments of the rivers Sava, Drava, Neretva and the karst poljes Imotsko Polje and VrgoraËko Polje that are also flooded in spring periods and whose floors contain lacustrine type of sediment. Cobalt (Co) The distribution of cobalt (Plates 9 & 10) is in high cor- relation with the distribution of Al, Fe and Mn, indicat- ing the effects of coatings of iron and manganese hydroxides on clay mineral surfaces. The content of Co Fig. 6 The relationship between the contents of CaO and A l2O3 (data for W Croatia from MIKO et al., 2000, 2001). Fig. 7 The relationship between the contents of K and Ba (data for W Croatia from MIKO et al., 2000; 2001). 62 Geologia Croatica 54/1 ranges from 2 to 38 mg/kg in both regions and the mean contents in northern Croatia is 12 mg/kg and in south- ern Dalmatia 17 mg/kg. The highest contents of cobalt occur in terra rossa with high iron and manganese con- tent in southern Dalmatia. In northern Croatia the high concentrations of cobalt are also controlled by bedrock lithology with elevated values in soils developed on basic and ultrabasic magmatic rocks as well as on Cre- taceous flysch deposits. Chromium (Cr) The concentration of chromium (Plates 11 & 12) in soils ranges from 32 to 524 mg/kg with a mean value of 83 mg/kg in northwestern Croatia, whereas in southern Dalmatia range from 15 to 2,200 mg/kg with a mean value of 126 mg/kg. The higher (>83mg/kg) concentra- tions of Cr in fluvisols and gleys can be attributed to deposition on reducing geochemical barriers and high organic matter content in NW Croatia while the high anomalies of over 500 mg/kg near Zelina can be a con- sequence of chromite bearing ultramafic magmatic rocks and clastic rocks derived from older basic mag- matic rocks. The highest concentrations of Cr in the karstic regions are confined to three general environ- ments: to terra rossa soils which contain redeposited bauxite fragments (wider region of Sinjsko Polje and Imotski), the soils developed on Eocene flysch and the soils developed on Quaternary sands (Mljet Island and KorËula Island). Both the Eocene flysch and Quater- nary sands are probably partly derived from basic or ultrabasic rocks. The influence of clays on Cr distribu- tion is shown on the Cr vs. Al2O3 plot on Fig 8. Copper (Cu) The content of copper (Plates 13 & 14) in soils ranges from 5 to 248 mg/kg with a mean value of 26 mg/kg in northwestern Croatia, while in southern Dalmatia it ranges from 6 to 923 mg/kg, with the mean value of 67 mg/kg. Copper is a potential risk element and most of the elevated concentrations cannot be correlated with a certain soil type but more to agricultural activity espe- cially the vicinity of vineyards (the application of pesti- cides based on copper sulphate). The anthropogenic influence on Cu distribution is shown on the Cu vs. A l2O3 plot on Fig. 9 indicating a divergence of data from the general Cu/Al trend. Iron (Fe) Iron content in soils (Plates 15 & 16) is mainly con- trolled by its clay content, the parent lithology and the content of carbonates just as in the case of Al. This link is stressed by high correlation (r=0.92, Tables 2 and 3) of the two elements and the similarity of distribution maps (see Plates 1 & 2). Iron contents range from 0.60% to 6.43%, with a mean value of 3.28% in north- western Croatia while in southern Dalmatia its contents range from 0.43% to 35.0%, with a mean value of 3.94%. The lowest Fe concentrations, just as in the case of Al, are found in soils that contain higher carbonate contents such as rendzinas on dolomites and lime- stones, soils developed on flysch bedrock and on car- bonate rich alluvium deposits along the Sava River near Zagreb, or in karst poljes which contain lacustrine sedi- ments. In the region of southern Dalmatia the terra rossa soils regularly have the highest Fe contents >4.5%, while the alluvial and marsh soils due to dilu- tion by carbonates have concentrations lower than 3%. Lanthanum (La) The La content in soils (Plates 17 & 18) seems to be mainly controlled by its clay content, and it correlates well with elements of geochemically similar behavior such as Th, and Sc (r=0.6). The correlation (r=0.45) with Al is rather low but the general trend indicates the importance of Al. The concentration of La in soils ranges from 9 to 54 mg/kg with a mean value of 34 Fig. 8 The relationship between the contents of Cr and Al2O3 (data for W Croatia from MIKO et al., 2000, 2001). 63Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... mg/kg in NW Croatia, whereas in southern Dalmatia ranges from 4 to 109 mg/kg and the mean value of 48 mg/kg. The effect of dilution by carbonates is also evi- dent in the distribution of this element; and the contents of La are highest in terra rossa and have mean values of 60 mg/kg which is similar to the values given by DURN (1996) for Istrian terra rossa. Lead (Pb) The concentration of lead (Plates 19 & 20) in soils ranges from 15 to 382 mg/kg with a mean value of 34 mg/kg in northwestern Croatia, whereas in southern Dalmatia range from 9 to 220 mg/kg and the calculated mean value is 52 mg/kg. There is a significant differ- ence in the content of Pb in soils developed on carbon- ate terrain and those on non-carbonate terrains. In car- bonate terrains the rendzina types of soil have higher than average contents (>60mg/kg). The effect of car- bonate dilution is obvious in soils developed on clastic rocks and alluvial sediments which have low Pb con- tents ranging from 20 to 30 mg/kg. Higher contents of lead are also linked to higher altitudes; a similar distrib- ution pattern impact is also encountered in mountain regions of western Croatia (MIKO et al., 2000, 2001). The anomalous lead concentrations in southern Dalma- tia can be attributed partly to traffic but the influence of war activities at the beginning of the 1990s cannot be excluded. The anomalous lead concentrations were found in soils developed on the floodplain sediments of the Drava River. The source of the lead can be traced to the Pb-Zn mining regions (Meæica, Bleiburg) located in the upper coarse of the Drava River in neighbouring Slovenia and Austria. Most of the other areas in north- western Croatia that display elevated contents of Pb can be mainly traced to past mining activities and Pb-Zn- ore occurrences; possible car traffic influences cannot be unequivocally recognized on a regional scale. Potassium (K) Potassium content in soils (Plates 21 & 22) ranges from 0.33% to 3.28%, with a mean value of 1.66% in north- western Croatia, whereas in southern Dalmatia its con- tents range from 0.12% to 2.89%, with a mean value of 1.20%. The content of potassium in soils is besides Na and Ba the major element that discriminates the soils developed in the karst region and the soils from north- western Croatia. In Fig 10, a S-N profile from the Adri- atic coast (Loπinj and Cres Islands, through the regions of Gorski kotar to Meimurje in the north, shows a northward increasing trend in the content of these two elements. The increase is most evident to the north from the Sava River, which is also very similar with K distribution in Slovenian soils (ANDJELOV, 1994). In southern Dalmatia the highest K contents are present in terra rossa and soils developed on flysch, and in soils developed on the southern/southwestern parts of the islands Hvar, KorËula and Mljet. High K contents were also found in recent marine sediments (DOLENEC et al., 1998) in the region of these islands. Sodium (Na) The contents of the sodium (Plates 23 & 24) are higher in NW Croatia and range from 0.11% to 3.21%, with a mean value of 0.83%; in southern Dalmatia its contents range from 0.01% to 1.04%, with a mean value of 0.29%. The content of sodium together with Ba and K is the major element that discriminates the soils devel- oped in the karst region and the soils from the Pannon- ian basin. Although the distribution pattern of sodium in soils (Plates 21 & 22) is similar to potassium in northwestern Croatia (a trend increase towards the north from the Sava River) there is an absence of sig- nificant correlation between the two elements (r=0.1), whereas in southern Dalmatia the correlation (Table 3) is significantly higher (r=0.63). The lowest concentra- tions of Na in the karst terrains are found in soils devel- Fig. 9 The relationship between the contents of Cu and Al2O3 (data for W Croatia from MIKO et al., 2000, 2001). 64 Geologia Croatica 54/1 oped on marls, while the highest accumulations are pre- sent in marsh sediments. In general the drained soils (developed on limestone) have the lowest Na contents in both regions. The highest concentrations of Na occur on soils developed on ortho-greenshists and spilitized basic rocks (Medvednica Mt.) in NW Croatia, these rocks seem to be an important source for Pliocene sedi- ments that occur on the slopes of Mt. Medvednica, because the soils developed on these rocks have a simi- lar distribution pattern as Ti (the correlation coefficient for NW Croatia is 0.62). Elevated Na contents are pre- sent in all soils that lie between the rivers Mura and Drava. The differences in contents of Na between the regions are presented in the Na vs. K plot in Fig. 11. Magnesium (Mg) Magnesium (Plates 25 & 26) as a major element and nutrient plays an important role in the chemistry of the Table 2 The correlation matrix for the geochemical soil data from northwestern Croatia (n=293). 65Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... analyzed soils. Its contents range from 0.23 to 7.52% in northwestern Croatia and from 0.82% to 9.24% in southern Dalmatia, with mean concentrations of 1.44% and 1.19% respectively. The lowest concentrations of Mg were determined in soils developed on loess depo- sits and gleyic soils in northwestern Croatia and in southern Dalmatia in terra rossa and brown soils devel- oped on limestones. Rendzinas developed on dolomite due to the large amount of fine dolomitic detritus regu- larly contain more than 1.5% of Mg. The scatter plot CaO-MgO (Fig. 12) shows the variation of these ele- ments in the analyzed soils in accordance with their dolomite and calcite content (compositions of norma- tive dolomite from EBENS & CONNOR, 1980). High magnesium contents characterize soils developed on floodplain sediments with abundant dolomite of the rivers Sava, Drava, and Neretva. Table 3 The correlation matrix for the geochemical soil data from southern Dalmatia (n=404). 66 Geologia Croatica 54/1 Manganese (Mn) The concentration of manganese (Plates 27 & 28) in soils ranges from 131 to 5,619 mg/kg with a mean val- ue of 622 mg/kg in NW Croatia, and from 96 to 2,563 mg/kg in southern Dalmatia with the mean value of 971 mg/kg. In southern Dalmatia higher than 1,000 mg/kg concentrations of Mn occur in terra rossa, brown soils and rendzinas on limestones, as well as in soils devel- oped on marls. The content of Mn in this region is low- est (<500 mg/kg) in soils, which are for some periods saturated with water and where mobilization of Mn in the soil profile is present. These are soils in large karst poljes and the floodplain of the Neretva River. Man- ganese hydroxides together with iron hydroxides play an important role in concentration of metals (McKEN- ZIE, 1989) and in the case of soils developed on car- bonate bedrock there is a high correlation of Mn with Co (r=0.76) while elements such as Cr, V, Ni, Pb and Zn are preferentially concentrated by iron oxides (for Mn r<0.5, for Fe r>0.5). In NW Croatia the highest concentrations of Mn are found in the eastern parts of IvanπËica Mt. and Kalnik Mt. probably as a reflection of Mn deposits and occurrences. The alluvial soils in the valleys of the Drava and Mura Rivers also have ele- vated contents of Mn. Nickel (Ni) The distribution of nickel (Plates 29 & 30) is similar to the distribution pattern of Co and is in high correlation with the distribution of Al, Fe and Mn, indicating the effect of coatings of iron and manganese hydroxides on clay mineral surfaces. The content of Ni ranges from 13 mg/kg to 427 mg/kg, with a mean value of 42 mg/kg in NW Croatia and in southern Dalmatia its contents range from 7 to 288 mg/kg, with a mean value of 84 mg/kg. The high concentrations near Zelina are a consequence of basic and ultrabasic magmatic bedrocks. These rocks are probably sources of Ni in alluvial soils that occur in floodplains of rivers (central northwestern Croatia) that drain this region. The highest concentrations of Ni in Fig. 10 The relationship between the contents of Na+K and latitude. Fig. 11 The relationship between the contents of Na2O and K2O (data for W Croatia from MIKO et al., 2000, 2001). 67Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... the karstic regions are confined to three soil types, the terra rossa soils, the soils developed on Eocene flysch (the wider region of Dubrovnik) and the soils devel- oped on Quaternary sands (Mljet Island and KorËula Island). Both the Eocene flysch sedimentary rocks and Quaternary sands are probably partly derived from weathering products of basic magmatic rocks. Phosphorus (P) Phosphorus (Plates 31 & 32) contents range from 0.02% to 0.19%, with a mean value of 0.064% in north- western Croatia; in southern Dalmatia its contents range from 0.012% to 0.68%, with a mean value of 0.08%. The lowest concentrations of P are found in soils of the islands KorËula, Hvar and Mljet in southern Dalmatia. The type of soil seems to have little influence on the content of P in the karst region since the variation and means are similar for all soil types; only soils on flysch (sandstones and marls) have in general lower P contents (<0.06%). In NW Croatia there is also obvious correla- tion of P content and soil type but in general forest soils have the lowest (median = 0.04%) content and the arable soils the highest (median = 0.09%) content. The anthropogenic influence on the distribution of this nutrient is evident since highest concentrations are found in agricultural regions. Scandium (Sc) The Sc content in soils (Plates 33 & 34) is mainly con- trolled by its clay content, and it shows a high correla- tion with Al and Fe (r=0.9). Geochemically it is consid- ered a conservative element similar to Al and is also often used for normalization procedures. The concen- tration of Sc in soils ranges from 2 to 18 mg/kg with a mean value of 9 mg/kg in NW Croatia, and in southern Dalmatia it ranges from 4 to 34 mg/kg, with the mean value of 12 mg/kg. The effect of dilution by carbonates is also evident in the distribution of this element; the contents of Sc are highest in terra rossa while the soils developed on marls and carbonate alluvial sediments have the lowest contents. Strontium (Sr) The distribution of strontium (Plates 35 & 36) is similar in some aspects to the distribution pattern of Ca. The dissimilarity occurs in soils developed on dolomite, since these soils contain high Ca contents but lack strontium whose concentrations are low in dolomite and alluvial sediments containing dolomite. The content of Sr ranges from 45 mg/kg to 1,090 mg/kg, with a mean value of 118 mg/kg in NW Croatia; in southern Dalma- tia its contents range from 40 mg/kg to 476 mg/kg, with a mean value of 127 mg/kg. The high content of stron- tium is found in both regions in soils developed on Ter- tiary lacustrine marls, on flysch bedrock, soft lime- stones and in alluvial valleys in the karst regions that during flooding have features of intermittent lakes (VrgoraËko polje). Soils on dolomitic bedrock and terra rossa on limestone have low Sr contents (<90 mg/kg). Titanium (Ti) Titanium content (Plates 37 & 38) ranges from 0.08% to 1.09%, with a mean of 0.39% in northwestern Croat- ia, whereas in southern Dalmatia its content ranges from 0.05% to 0.87%, with a mean of 0.37%. The low- est Ti contents are found in soils that contain higher carbonate contents such as rendzinas on dolomites and limestones, soils developed on flysch bedrock and on carbonate rich alluvium deposits along the Sava River near Zagreb, or in karst poljes which contain lacustrine sediments. The high correlation (r=0.9) of Ti with Al and Fe in soils from southern Dalmatia (Table 3) is indicative of similar processes of enrichment. In soils from NW Croatia there is an absence of such relation- Fig. 12 The relationship between the contents of MgO and CaO. Dolomite = normative dolomite from EBENS & CONNOR, 1980) (data for W Croatia from MIKO et al., 2000, 2001). 68 Geologia Croatica 54/1 ships (Al vs. Ti r=0.37; Fe vs. Ti r=0.24; Table 2), and the highest contents of Ti are confined to gleys devel- oped on loess, and in marshlands. The highest contents of Ti are found in soils overly- ing basic magmatic and ortho-greenschist metamorphic complexes on Medvednica Mt. The distribution differ- ences between the karst region and the Pannonian region is illustrated on the plot Ti vs. Al2O3 in Fig. 13. Thorium (Th) The concentration of Th in soils (Plates 39 & 40) ranges from 2 to 17 mg/kg with a mean value of 11 mg/kg in NW Croatia, whereas in southern Dalmatia it ranges from 2 to 29 mg/kg, with the mean value of 16 mg/kg. The thorium content in soils has a high correla- tion with Al and Fe (r=0.8 in southern Dalmatia, r=0.7 in NW Croatia). The effect of dilution by carbonates is also evident in the distribution of this element, and the contents of Th are highest in terra rossa while the soils developed on marls and carbonate alluvial sediments have the lowest contents. Vanadium (V) The content of vanadium in the analyzed soils (Plates 41 & 42) ranges from 22 to 238 mg/kg, with a mean value of 101 mg/kg in NW Croatia; whereas in southern Dalmatia its contents range from 16 mg/kg to 386 mg/kg, with a mean value of 142 mg/kg. The distribu- tion of V similar to the distribution patterns of Al and Fe (r=0.9) indicates the role played by coatings of iron hydroxides on clay mineral surfaces (SCHWERTMAN & TAYLOR, 1989). The highest contents of V similar to Ti are found in soils overlying basic magmatic and ortho-greenschist metamorphic rock complexes on Medvednica Mt. The highest concentrations of V in the karstic regions characterize the terra rossa, while soils developed on Eocene flysch (the wider region of Dubrovnik) and the soils developed on Quaternary sands (Mljet Island and KorËula Island) as well as allu- vial (with carbonates) soils have low concentrations of vanadium. Zinc (Zn) The content of Zn (Plates 43 & 44) ranges from 28 mg/kg to 974 mg/kg, with a mean value of 92 mg/kg in NW Croatia; in southern Dalmatia its contents range from 16 to 491 mg/kg, with a mean value of 113 mg/kg. There is a significant difference in the behavior of Zn in soils developed on carbonate terrain and those on non- carbonate terrains. In carbonate terrains Zn is controlled by the clay content (Zn-Al correlation coefficient r= 0.48, Table 3) and higher contents are the characteristic of rendzina type of soils as well as of soils developed at higher altitudes (<140 mg/kg), which is similar to the distribution of Pb (r=0.47). The effect of carbonate dilution is obvious in soils developed on clastic rocks and alluvial sediments, which have low Zn contents (<75 mg/kg). Anomalous lead concentrations in NW Croatia are found in soils developed on the floodplain sediments of the Drava River. The sources of the Zn, as in the case of Pb (r=0.96, Table 2) can be traced to the Pb-Zn mining regions (Meæica, Bleiburg) located in the upper course of the Drava River in neighbouring Slove- nia and Austria. Most of the other areas in northwestern Croatia that display elevated contents of Pb can be mainly traced to past mining activities and Pb-Zn ore occurrences, although other possible anthropogenic influences cannot be unequivocally recognized, espe- cially in the lower course of the Sava River. Mercury (Hg) The content of mercury at this stage of investigation was determined only in soils from northwestern Croatia (Pl. 45). The Hg concentrations range from values below 10 µg/kg to 4,535 µg/kg, with a mean value of Fig. 13 The relationship between the contents of Ti and Al2O3 (data for W Croatia from MIKO et al., 2000, 2001). 69Miko, HalamiÊ, Peh & GaloviÊ: Geochemical Baseline Mapping of Soils... 94 µg/kg. The highest concentration of 4,535 µg / k g was measured in soils developed on limestone from a location on Kalnik Mt. The sources of this high Hg con- tents, as well as the high contents on the neighboring IvanπËica Mt. are probably a consequence of mineral- ization occurrences. Urban soils in general have higher Hg contents especially in the cities of Zagreb and Varaædin. High contents of Hg in urban soils of Zagreb were also determined by NAMJESNIK et al. (1992) and PALINKA© et al. (1996); in a study by MIKO et al. (1992) it was determined that the Hg is derived from fossil fuel consumption (coal). The elevated Hg con- tents in soils developed on the Sava River floodplain sediments is a consequence of material derived from the Litija mining region which produced 150 t of Hg from 1880 to 1965 (MLAKAR, 1993). The soils of the region of Samoborska gora Mt. (Rude) also contain ele- vated Hg contents as a response of base metal sulphide mining and occurrences of mineralization. 4.2. Geochemical associations and environmental applications Geochemical baselines are principally useful for the determination of environmentally significant contents of elements for the evaluation of pollution sources. Since the variation of geology at a regional scale influ- ences the geochemical background considerably the definition of these values must be performed in a cor- rect manner. There are various approaches in use depending on the type of data, media, and analytical techniques (DARNLEY, 1995; SALMINEN & TAR- VAINEN, 1997; BODI© & RAPANT, 2000). The leg- islative approach uses the geochemical data for compar- ison with defined environmental thresholds as in the Netherlands (VAN LIENEN et al., 2000) or the inter- vention criteria in Italy as used by De VIVO et al. (1998). Today in Croatia only agricultural thresholds for ten potentially toxic elements (Pb, As, Cd, Co, Ni, Zn, Cu, Hg, Mo and Cr) (NARODNE NOVINE, 1992) exist which were derived from a small data set and compiled from regulations of other countries. The human impact on soils can be also evaluated by calculation of enrichment factors (HASSAN & ISMA- IL, 1993). The enrichment factor (EF) is the concentra- tion ratio of an element in each individual sample ( Cn s a m p l e) and the conservative element (usually Al, Ti, Sc) in the sample (C cons.sample), in respect to same ratio of element and the conservative element in a reference material Cn ref./ Ccons. ref. (FÖRSTNER & WITTMANN, 1981; LI, 1981): EF = (Cnsample/Ccons.sample ) / (Cn ref./Ccons. ref.) The definition of the enrichment factor indicates that this parameter depends on the choice of reference element and the choice of reference material. The influence of referent element choice upon the value of enrichment factor is discussed in papers of numerous authors, but Al is the commonest in use and its correlation with the clay content in sediments and soils, is well established (WINDOM et al., 1989; DURN et al., 1999) and has been quite frequently applied in the karst regions of Croatia (PROHI∆ et al., 1995, 1998; MIKO et al., 1999). According to the crite- ria of GOLCHERT et al. (1991) who distinguish three categories of the enrichment factors: EF≤2, 2