Koncentracija aktivnosti 226Ra, 210Pb, 7Be i 40K u uzorcima listova i grančica listopadnog drveća gradskih parkova

Abstract

U ovom radu ispitivana je koncentracija aktivnosti 226Ra, 210Pb, 7Be i 40K u uzorcima lišća (n = 18) i grančica (n = 12) dve vrste širokolisnog drveća, kestena (Aesculus hippocastanum L.) i lipe (Tilia spp.) sakupljanim u proleće i jesen u tri gradska parka: Botanička bašta, Studentski park i Karađorđev park. Uzorci biljnih tkiva kestena i lipe grupisani su zajedno po vrsti i sezoni: lišće u proleće (LP) i jesen (LJ) i grančice u proleće (GP) i jesen (GJ). Ovaj rad se nastavlja na prethodnu studiju istih parkova koja je pokazala da se koncentracije aktivnosti pomenutih prirodnih radionuklida u zemljištu ne razlikuju od parka do parka zbog čega je bilo moguće ispitati odnose koncentracija aktivnosti samo u biljnim tkivima i to iste vrste uzoraka u različitim sezonama (LJ/LP, GJ/GP) i različitih uzoraka u istoj sezoni (LP/GP, LJ/GJ). Rezultati ispitivanja su pokazali da je 226Ra bio uskladišten u grančicama u proleće i do kraja vegetativnog perioda koncentracija aktivnosti je rasla tako da je u lišću u jesen dostignuta ravnoteža sa onom u grančicama. Koncentracija aktivnosti 210Pb bila je ≈ 2 puta veća u lišću nego u grančicama nezavisno od biljne vrste i sezone. Od proleća do jeseni primećen je porast koncentracija aktivnosti 7Be u listovima kestena i lipe (LJ/LP > 1) i, suprotno tome, u grančicama je primećen pad (GJ/GP < 1). Kao šte je i očekivano, koncentracija aktivnosti 40K listova i grančica opadala je sa zrelošću biljnog tkiva, ali je ≈ 2 puta bila veća u lišću nego u grančicama nezavisno od biljne vrste i sezone.

In this work, the activity concentration of 226Ra, 210Pb, 7Be and 40K was investigated in the samples of leaves (n = 18) and twigs (n = 12) of the two broadleaf tree species, chestnut (A. hippocastanum L.) and linden (Tilia spp.), collected in spring and autumn in the three city parks: Botanical Garden, Student Park and Karađorđev Park. The tissue samples from chestnut and linden trees were grouped by type and season: leaves in spring (LP) and autumn (LJ), and twigs in spring (GP) and autumn (GJ). This work follows on from a previous study in the same parks, which showed that the activity concentrations of the mentioned natural radionuclides in soil do not differ from park to park, so it was possible to study the relationships between the activity concentrations in plant tissues: those of the same type of samples in different seasons (LJ/LP, GJ/GP) and those of different samples in the same season (LP/GP, LJ/GJ). The results showed that 226Ra was stored in the twigs in spring and the activity concentration increased towards the end of the vegetative season, reaching an equilibrium between leaves and twigs in autumn. The 210Pb activity concentration was ≈2 times higher in leaves than in twigs, regardless of plant species and season. From spring to autumn, an increase in 7Be activity concentration was observed in chestnut and linden leaves (LJ/LP > 1), while in contrast a decrease was observed in twigs (GJ/GP < 1). As expected, the concentration of 40K activity in leaves and twigs decreased with plant tissue maturity, while it was ≈ 2 times higher in leaves than in twigs, regardless of plant species and season.