Two Decades of Environmental Isotope Records in Croatia: Reconstruction of the Past and Prediction of Future Levels

Abstract

A two-decade-long record of environmental isotopes (2H, 3H, 14C, 18O) in Croatia is presented and the data are statistically analyzed. The atmospheric 14C activity for the period before the actual measurements started is reconstructed by measuring tree rings from the clean-air sites, and the past tritium activity in precipitation is estimated by the correlation of our data with the Vienna station record. The long-term 3H record helped to determine a locally contaminated sampling site, and new clean sites are put into operation. The 14C data were fitted by an analytical function and the prediction of future levels is given assuming that the rate of the 14C releases remains constant. From the long-term stable isotope data record, the local meteoric water line and the temperature gradient of δ18O in precipitation are determined.

Isotopic composition of precipitation at the station Ljubljana (Reaktor), Slovenia – period 2007–2010

“…The seasonal fluctuations of tritium activity observed for the present short period (Vre^a et al, 2008). However, the long-term data show a seasonal structure superposed on the basic decrease in mean annual tritium activities (krajcar BronI] et al, 1998Vre^a et al 2008), while data recorded since 1998 show no significant decrease of mean annual values. The mean tritium activity for the period 1998-2010 is 9.1 TU while, in the studied period, it is 8.3 TU (Table 2).…”

“…The data constitute an important input into isotope investigations and were used in evaluations of GNIP data (e. g. rozanskI et al, 1993;IchIyanagI, 2007;hughes & crawford, 2012), and in many hydrological and hydrogeological investigations (e. g. krajcar BronI] et al., 1998;PezdI^, 1999PezdI^, , 2003Bren^I^ & Vre^a, 2006;Vre^a et al, 2006Vre^a et al, , 2008ogrInc et al, 2008;VodIla et al, 2011;kandu^ et al, 2012;zaVadlaV et al, 2012;cerar & urBanc, 2013;MarkoVI] et al, 2013;Mezga et al, 2014).…”

Radiocarbon method in monitoring of fossil fuel emission

“…To compare, the Δ 14 C values found in tree rings were 108.7±3.5‰, 99.8±3.6‰ and 85.3±3.5‰ for years 1994, 1995 and 1996, respectively. These values are lower than the yearly mean values in atmospheric CO 2 at Schauinsland (117‰, 111‰ and 102‰; Levin and Kromer, 2004), but higher than those measured in Zagreb (annual average -81‰, 88‰ and 56‰; Krajcar-Bronić et al, 1998) Linacre and Greets (1997). After Hua and Barbetti (2004).…”

Isotopic composition of precipitation in Portorož (Slovenia)

“…The natural atmospheric tritium concentration increased about 10 3 times (inGrahaM, 1998) after the nuclear weapon tests in the early 1960s. Since 1963 it has been constantly decreasing, partly due to radioactive decay of tritium and partly due to its redistribution in other water reservoirs, such as the oceans (inGrahaM, 1998;Gat et al, 2001 Broni} et al, 1998;PezDi~, 2003;vre~a et al, 2005, 2006, 2007 and along the River Sava (OGrinc et al, 2008). The data obtained are partly reported to the International Atomic Energy Agency (IAEA) and included in the Global Network of Isotopes in Precipitation (GNIP) and the Global Network of Isotopes in Rivers (GNIR).…”

“…Since the ban of atmospheric nuclear and thermonuclear bomb-tests, the tritium activity in preci pitation showed a basic decreasing trend with a superimposed seasonal structure. However, during the last two decades (approximately), the mean annual values in Zagreb and Ljubljana (krajcar Broni} et al, 1998;vre~a et al, 2006 remai ned stable/constant, at va lues of about 9 TU. The values observed at Portorož are lo wer than for Ljubljana and are typical of stations close to the sea (vre~a et al, 2006, 2008).…”