CHEMICAL COMPOSITION OF SCOTS PINE BARK AS A BIOINDICATOR OF ENVIRONMENTAL QUALITY IN RIGA, LATVIA

The chemical composition of pine bark was used for the determination of environmental quality in Rîga. Bark samples were collected at 54 sites in Rîga differing in vegetation and building area characteristics (urban forests, parks and cemeteries, dwelling houses, and streets and railway zones) and at 52 sites from rural areas in Latvia (background level). Concentrations of Ca, Mg, Na, K, Fe, Mn, Zn, Ni, Cu, Cd, Pb, and pH was determined in the samples. The results showed significantly higher concentrations of chemical elements in pine bark collected in Riga, compared to background levels: Fe and Cu concentrations three times higher, and other elements — up to1.8 times. The highest element concentrations in Rîga were near streets (Sarkandaugava, Jaunmîlgrâvis, Daugavgriva, ciekurkalns, Imanta area, etc.). Element concentration and pH was significantly dependent on the distance from the closest street. The lowest element concentra- tions were found in urban forests (Jugla, Biíernieki, Beberbeíi) and parks and cemeteries (I Forest Cemetery, Jaunciema Cemetery). Mezaparks (forest), Sarkandaugava, Jaunmîlgrâvis, and Vecmîlgrâvis together formed the most polluted area in Rîga due to the close location near and downwind from the harbour.