Elemental composition of Russula cyanoxantha along an urbanization gradient in Cluj-Napoca (Romania)

How far-reaching is the influence of the urban area over the mineral composition of the Russula cyanoxantha mushroom? We studied the metal uptake behavior of this fungus relying on the soil properties. We sampled mushroom and soil from six forests according to an urbanization gradient, and two city parks in Cluj-Napoca (Romania). The elements were quantified using inductively coupled plasma - optical emission spectroscopy (ICP-OES). The concentrations of some elements differed significantly (p < 0.05) in the samples from the city (0.39 ± 0.35 mg kg^-1 for cadmium (Cd), 0.40 ± 0.19 mg kg^-1 for chromium (Cr), 69.1 ± 29.9 mg kg^-1 for iron (Fe), 10.9 ± 1.3 mg kg^-1 for manganese (Mn), 0.76 ± 0.45 mg kg^-1 for titanium (Ti) compared with the samples from the forests (3.15-14.1 mg kg^-1 Cd, < 0.18 mg kg^-1 for Cr, 22.6-34.5 mg kg^-1 for Fe, 15.9-19.1 mg kg^-1 for Mn, 0.19-0.36 mg kg^-1 for Ti). We observed a definite negative trend in the mineral accumulation potential of this fungus along the urbanization gradient. The fungus turned from a cadmium-accumulator to a cadmium-excluder. This highlights a positive environmental influence of the urbanization over the toxic metal uptake of R. cyanoxantha. The hypothesis, that the urban soil pollution would increase the metal content of the mushroom was disproved. The possible explanation might be the elevated carbonate content of the urban soil, which is known to immobilize the metals in the soil.