This paper presents the results of the preliminary testing of the selected trace elements in the soils of several parks in the city of Zagreb, Republic of Croatia. In each park, the samples were taken from several points-at various distances from the roads. The samples were taken at two different depths: 0-5 and 30-45 cm. Composite samples were done for each sampling point. Microwave-assisted wet digestion of the soil samples was performed and the determination by ICP-AES technique was done. Results obtained for Al, As, Ba, Mn, Ti, V, and K are in a good agreement with the results published in the scientific literature so far. The mass fraction values of Cd, Cr, Cu, Ni, Pb, and Zn are somewhat higher than the maximum values given in the Croatian Directive on agricultural land protection against pollution. Be, Mo, Sb, Se, and Tl in the samples were present in the concentrations that are lower than their method detection limit values.

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Research on oil residuals in lowland forest soil was carried out in 6 sample plots in the lowland forest ecosystem located in an oil field. Four plots were differently affected in terms of discharged oil and the time lapsed after the accident, as well as in terms of micro-relief terrain features. One plot was established in a reclaimed mud ditch site, while the control plot was set up in a micro-relief elevation outside the influence of oil pollution.Total petroleum hydrocarbon (TPH) concentrations were measured at three soil depths at the beginning and the end of the vegetation period. The analysis of the results revealed significant differences in petroleum hydrocarbon concentrations among the sites. Increased TPH concentrations were recorded in several plots, while the values measured in some other plots indicated very low quantities of residual TPH in the soil. The highest average TPH concentrations (200-400 mg kg −1 ) were recorded in the mud ditch site. In one of the plots exposed to oil pollution after an oil pipe rupture, there was the constant presence of increased TPH concentration in the surface soil part (>200 mg kg −1 on average). The sporadic presence of increased TPH concentrations in micro-depressions that cannot be attributed to a local accident indicates seasonal soil pollution with petroleum carbohydrates from floodwater.The soil in the sample plots is not contaminated with soluble salts or heavy metals. Low values of TPH concentrations in the soil water eluate indicate that the soil does not represent a source of hydrospheric pollution with petrol hydrocarbons.

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There are many various environmentally hazardous substances, but researchers around the world are especially interested in heavy metals. Heavy metals are naturally occurring elements that have a high atomic weight and a density at least 5 times greater than that of water [1]. From a biological point of view, Nieboer and Richardson [2] have classified heavy metals into three groups: (i) elements essential to some organisms (V, Cr, Mn, Fe, Co, Zn, and Mo), (ii) elements necessary for growth and development of plants (Mn, Fe, Cu, Zn, Mo, and Ni), and (iii) phytotoxic elements (Cd, Hg, and Pb). World Health Organization (WHO) has classified As, Cd, Hg, and Pb among 10 groups of hazardous chemicals. Those are elements which have toxicological characteristics. Moreover, when their concentrations increase, Mn, Co, Ni, Cu, Zn, Se, Ag, Sb, and especially Cr and Ti are also considered toxic [3]. Since the pollution of soil by heavy metals is one of the possible causes of a decrease in forest ecosystem vitality and degradation of the whole habitat, there is a significant scientific interest in research of the connection of heavy metal concentration values in the environment to their degradation effect [4]. In higher concentrations heavy metals

ABSTRACT:Like in other types of forests the greatest changes in the soil of floodplain forest stands occur during their regeneration. These changes are manifested as changes in the content and dynamics of organic matter in the soil. Research was conducted in oak and ash floodplain forests in the eastern part of Croatia and in southern Moravia in the Czech Republic. The results showed that the type and extent of these changes depended, in addition to environmental factors, also on the technology of forest regeneration. The natural regeneration of oak in floodplain forests of Spačva (eastern Croatia) protects soil from dramatic changes in soil by successive regeneration felling and that it retains the plant cover permanently. The weight of organic matter on the soil surface is increased after regeneration till the period when the effect of thinning becomes evident (about 70 years). In the surface mineral layer of soil the pH value increases after shelterwood felling. Stand regeneration with clear-cutting results in a rapid change in the conditions of surface humus accumulation and decomposition. The process of organic residue accumulation is interrupted in the clearings. In the preparation of soil/site by ploughing, the concentrations of nitrogen and carbon slightly decrease. The management impact depends on the method of site preparation for the establishment of a new stand. The selection of a method of the floodplain forest regeneration (particularly of oak) is markedly dependent on actual ecological conditions and on ecological and historical experience of the given region. Matić (1996, 2003a,b), Oršanić and Drvodelić (2007) consider natural regeneration of oak to be a method which preserves the uninterrupted development of forest sites and biocoenoses being realized during 3 stages (preparatory felling, seed felling and final felling). In addition to this, Houšková et al. (2007) drew a conclusion: "Natural regeneration of pedunculate oak cannot be fully relied on in the Czech Republic due to the long-term absence of rich mast years and it is, therefore, necessary to continue the planning of artificial regeneration. "Farm forestry (alternate forest and farm crops) as one of the methods of clear-felling regeneration shows potential negative impacts on the soil environment (Libus et al. 2007), particularly decreasing porosity and water retention capacity at a depth of 25 to 35 cm. Soil/site preparation by ploughing shows also negative impacts due to decreased accumulation of carbon.From the aspect of the ecosystem approach in the floodplain forest management, attention is also paid (in addition to maintaining the high production level of the ecosystem tree layer) to other components, such as preserving and increasing biodiversity at the level of communities and species, nature and water resources protection and the function of forests in the landscape and socioeconomic consequences.Problems of these functions were also dealt with by the last ministerial conference held in Warsaw at the beginning of 2007. Resoluti...

V jamskem sistemu Velebita (Severni Velebit, Hrvaška), smo do globine 1000 m merili klimatske in hidrološke parametre ter koncentracijo radona. Rezultate smo interpretirali z ozirom na globino in morfološke značilnosti jame. V jami smo izmerili dva različna temperaturna gradienta, ki jih povezujemo z jamsko morfologijo in kroženjem zraka v zgornjem delu brezna. Fizikalno-kemični parametri vode kažejo na nizko mineralizacijo sicer šibko alkalne vode. Kemija vode je v glavnem odvisna od petrografskih značilnosti kamnine (apnenec) in morfologijo jame oz. vodnih poti. Voda v jami ni onesnažena. Povprečna vrednost koncentracije radona je nizka, vsekakor nižja od drugih jam na Hrvaškem..

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