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ŠUMARSKI LIST 1-2/2016 str. 33     <-- 33 -->        PDF

horizon (0–10 cm) were collected at appropriate sampling places, according to Garcia et al. (2009). All samples were analysed in triplicate.
Analysis of heavy metals – Analiza teških metala
Collected specimens and samples of soil substrate were documented, oven dried (24 h; 103°C) milled with laboratory Retch SM2000 and pressed into tablets (r = 16 mm; d = 5 mm) with Chemplex press for further analysis. For analysis x-ray fluorescence spectroscopy was applied (XRF, TwinX, Oxford Instruments). In the first step qualitative analysis was performed. The most frequent pollutants were identified. For those elements calibration curves were prepared and in the second step quantitative analysis was carried out. Most of the measurements were performed on PIN detector (U = 26 kV, I = 115 µA, t = 300 s). The values of bioconcentration factors were calculated as a ratio between the heavy metal contents in the mushroom and the element concentrations in the growing substrate.
pH values and organic matter – Vrijednost pH i organska tvar
The pH value of the substrate soil samples was determined potentiometrically in the suspension of the substrate soil and distilled water in the ratio 1: 5. Measurement was carried out acording to methods adapted from „Methods of soil analasys” (Thomas, 1996). The pH value was determined using a pH meter IQ 150 (IQ Scientific Instruments, USA). Organic matter content was determined gravimetrically after combustion of soil (2g air-dried) at 550 °C during 16 h in a furnace horn (Select-Horn. Selecta) (Garcia et al., 2009).
Data analysis – Analiza podataka
Statistical analysis and chartings were performed within the R program (R Core Team, 2014) by using two integral and three external statistical packages. Descriptive statistics, calculation of bioconcentration factors and pair-wise comparisons (t-test) of means (concentrations of trace elements) between anatomical parts of the fruit body were obtained within the package „stats”, which is an integral package of R. Multiple pair-wise comparisons (TukeyHSD test) of means among species were obtained by the „agricolae” package (de Mendiburu, 2014). Extraction of the information required to create and plot compact letter displays of all pair-wise comparisons was performed within the „multcomp” package (Hothorn et al., 2008). Plotting of box-whisker plots was performed with the packages „graphics” (integral) and „lattice” (Sarkar, 2008).
Cluster analysis was performed within the „stats” package. The distance matrix was computed by using the „Euclidian” distance measure, and hierarchical cluster analysis was performed by using a method of complete linkage, which defines the cluster distance between two clusters to be at the maxi­mum distance between their individual components. At every stage of the clustering process, the two nearest clusters were merged into a new cluster, and this process was repeated until the whole data set was agglomerated into a single cluster. The results of cluster analysis were converted into a „phylo“ object within the „ape“ package (Paradis et al., 2004), and thereafter presented graphically as polar dendrograms.
RESULTS
REZULTATI
Heavy metals in soil substrate – Teški metali u supstratu tla
Soil properties (pH value and organic matter content) and average concentrations of iron, zinc and cooper in the area of Medvednica are summarized in Table 1. The mean pH value of the soil substrate at Medvednica was 7.22, within the range of min. 6.30 and max. 8.12. Organic matter content varied from 2.16% to 12.65%, with a mean value of 6.48%. The concentration of hevay metals in the soil substrate indicate that Fe concentration (7569.00 – 8322.00 mg kg–1) was the higest, followed by Zn (42.50 – 94.30 mg kg–1) and Cu (13.21 – 28.33 mg kg–1). The ratio between the highest and the lowest metal concentration (max/min) was highest in Zn (2.21), but only 1.10 in Fe.
Metal concentration and bioconcentration factors – Koncentracija metala i biokoncentracijski faktor u gljivama
Descriptive statistics on heavy metal concentration and factors of bioconcentration (BCF) are presented in Table 2.