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There is no unique way of mortar sample preparation that would always provide the true date. We propose a procedure of 14C age extrapolation from CO2 fractions obtained by sequential dissolution of mortar grain size 32 – 63 μm by phosphoric acid. The collection of CO2 fractions is deduced from kinetics of mortar- hydrolysis curve. The procedure was designed from data obtained from mortars prepared in laboratory and tested on mortar/plaster from three archaeological cases, with confirmed ages. The first fractions gave true result for historical mortars, but for laboratory ones only extrapolated values were true. When certain conditions regarding CO2 fraction collection were met, extrapolated values agreed with the first fractions for the historical mortars. Although the extrapolation procedure seems to eliminate the effect of dead carbon contamination, it is not effective against influence of delayed hardening or restoration.

Carbonization, i.e., turning organic sample to carbon, was validated for the benzene synthesis for the radiocarbon liquid scintillation measurement. Tests of sample preparation by combustion, carbonization followed by combustion and carbonization followed by a direct reaction with lithium were performed. Wood and charcoal samples were good for carbonization followed by direct reaction with lithium, while collagen obtained from bones had to be combusted. Direct reaction of carbonized sample with lithium required three times less amount of lithium than the combusted sample.

Between 1979 and 2003, a 35 cm thick layer of laminated tufa formed around a wooden pillar located at the beginning of the Korana River, which emerges from the Plitvice Lakes, Croatia. The laminated tufa structure allowed for the stratigraphic analysis of mineral, elemental and δ18O and δ13C isotope composition. Results are compared to other carbonate archives (lake sediments) from the Plitvice Lakes and to measured water physical–chemical data collected in the same time. An increase in water temperature and decrease in Mg/Ca ratio was observed during that period. Results showed that the tufa Mg/Ca ratio and δ18O could not be used as a temperature proxy, while an observed δ18O increase after 1990 was attributed to increase in evaporation rate. Furthermore, the constant increase in redox-sensitive elements (Mn) towards the external part of tufa may indicate periodic events of anoxia at the sediment/water interface. Local enrichment factors (LEFs) for potentially toxic elements were calculated using the background function and Al as the normalizing element. The LEFs showed an enrichment pattern of Cu and Pb in 1983 and 2001, which could indicate their anthropogenic origin and the sensitivity of the tufa to environmental changes.

Radiocarbon activity (a14C) and 13C composition (δ13C) were measured in hygrophyte and mesophyte (land) mosses collected in the natural habitat of the Plitvice Lakes and along the Zrmanja and Krupa Rivers (typical continental and Mediterranean climates, respectively), Croatia. a14C and δ13C values of mosses, of atmospheric CO2 and dissolved inorganic carbon (DIC) were compared for contemporary data and for data from 30 years ago at the Plitvice Lakes when 14C activity of atmospheric CO2 was ~30% higher. A positive 18 correlation between a14Cmoss and δ13Cmoss was observed for all data reflecting change of 19 carbon isotopic composition in DIC along the water flows and in atmospheric CO2 regardless of the climatic regions and historic period. Fraction of the atmospheric carbon in moss (ωatm. C) and carbon fractionation factor from aquatic CO2 (DIC) to moss tissue (εmoss/g-aq) were calculated for each individual moss. Three species of mosses had ωatm. C ~0 % implying that they turn to anabiosis during dry periods. The relation εmoss/g-aq vs. ωatm. C differentiates true aquatic and amphiphyte mosses. The first had a statistically significant negative correlation between εmoss/g-aq and ωatm. C. The amphiphyte mosses had lower εmoss/g-aq with higher water flow rates.

Carbon isotope composition of dissolved inorganic carbon (DIC) was studied at springs, lakes and tributaries of the Plitvice Lakes. The Plitvice Lakes are a unique and complex karst lakes system consisting of 16 flow- through lakes connected by waterfalls and streams and characterized by intense calcium carbonate precipitation in the form of tufa and lake sediments. Two main springs have different 14C concentrations due to different geology and their variations were controlled by flow rates. Further downstream, at lakes to the Korana River that outflows from the lakes, the 14C activity and δ13C consistently increased down the flow. Carbon isotope composition from 2010- 2015 was compared with the values measured 30 years earlier. The variation in δ13CDIC was accounted for seasonal change, while 14C activity of surface water DIC decreased 7 – 12 % during the 30 years. Using a semi-empiric model, it is calculated that the downstream increase in the carbon isotope values is controlled by the exchange of DIC and atmospheric CO2 carbon and by introduction of decomposed biogenic carbon from the top soil organic meter of the lakes surrounding area in almost equal proportions.

Tritium presents a natural radioactive isotope which can be used as a tracer in hydrology. This paper presents the usage of tritium in hydrogeological research of the Zagreb aquifer, which presents the country`s strategic water reserves and is protected by the Republic of Croatia. In the research area, higher tritium content in surface water and groundwater is the result of releasing coolant water from the Nuclear power plant Krško. Tritium content was measured in 13 piezometers and one pumping well, in the wider area of the Petruševec and Kosnica well fields. It has been shown that tritium from cooling water is much more pronounced than its natural seasonal variability, and it can be very useful as a tracer. Also, results showed that the intensity and delay of responses in the aquifer depend on their distance from the Sava River and piezometer depth. Furthermore, the results suggest that variable hydrologic conditions can generate rapid change in the groundwater flow direction and affect tritium transport through the aquifer., Tricij je prirodni radioaktivni izotop koji se može koristiti kao traser u hidrologiji. Ovim radom prikazuje se korištenje tricija u hidrogeološkim istraživanjima zagrebačkoga vodonosnika koji je Republika Hrvatska zaštitila i uvrstila u strateške zalihe vode. Na istraživanome području povišen sadržaj tricija u površinskoj i podzemnoj vodi posljedica je ispuštanja rashladne vode iz nuklearne elektrane Krško u rijeku Savu. Sadržaj tricija mjeren je u 13 piezometara i u jednome zdencu na području crpilišta Petruševec i Kosnica. Pokazano je da je tricij podrijetlom iz rashladne vode naglašeniji od njegove sezonske varijabilnosti te može biti korišten kao traser. Također, rezultati su pokazali da intenzitet i zakašnjenje reakcije u vodonosniku izravno ovisi o udaljenosti od rijeke Save i dubini piezometra. Nadalje, rezultati upućuju na to da promjenjivi hidrološki uvjeti uzrokuju brze promjene u smjeru tečenja podzemne vode i utječu na transport tricija kroz vodonosnik.

Tufa is a fresh-water surface calcium carbonate deposit precipitated at or near ambient temperature, and commonly contains the remains of macro- and microphytes. Many Holocene tufas are found along the Zrmanja River, Dalmatian karst, Croatia. In this work we present radiocarbon dating results of older tufa that was found for the first time at the Zrmanja River near the Village of Sanaderi. Tufa outcrops were observed at different levels, between the river bed and up to 26 m above its present level. Radiocarbon dating of the carbonate fraction revealed ages from modern, at the river bed, up to 40 kBP ~20 m above its present level. These ages fit well with the hypothesis that the Zrmanja River had a previous surface connection with the Krka River, and changed its flow direction toward the Novigrad Sea approximately 40 kBP (Marine Isotope Stage 3). Radiocarbon AMS dating of tufa organic residue yielded a maximum conventional age of 17 kBP for the highest outcrop position indicating probable penetration of younger organic material to hollow tufa structures, as confirmed by radiocarbon analyses of humin extracted from the samples. Stable carbon isotope composition (δ13C) of the carbonate fraction of (−10.4 ± 0.6)‰ and (−9.7 ± 0.8)‰ for the Holocene and the older samples, respectively, indicate the autochthonous origin of the carbonate. The δ13C values of (−30.5 ± 0.3)‰ and (−29.6 ± 0.6)‰ for organic residue, having ages &lt, 500 BP and &gt, 5000 BP, respectively, suggest a unique carbon source for photosynthesis, mainly atmospheric CO2, with an indication of the Suess effect in δ13C during last centuries. The oxygen isotopic composition (δ18O) agrees well with deposition of tufa samples in two stages, the Holocene (−8.02 ± 0.72‰) and “old” (mainly MIS 3 and the beginning of MIS 2) (−6.89 ± 0.34‰), suggesting a ~4 °C lower temperature in MIS 3 compared to the current one.

This study combines radiocarbon (14C) analysis and sclerochronology research, an approach that to the best of our knowledge, has not yet been applied using bivalves from the Mediterranean Sea. We analyzed shells from the North Adriatic Sea: live- and dead-collected specimens of the infaunal bivalveGlycymeris pilosaand two dead-collected specimens ofGlycymerissp. According to crossdating results, growth increment time series obtained from acetate peels of the dead-collectedG. pilosa(S3FP11) indicate the potential for creating longer chronologies from live and dead-collected specimens. The greatest longevity was seen in the dead-collectedGlycymerissp. specimen S3F3, estimated to be ~130 years (started growing AD 1678–1742 and died AD 1826–1860), indicating the potential to extendGlycymerisgrowth increment chronologies to past centuries. The highest ∆14C values obtained corresponded to the calendar year 1974. The14C record obtained fromG. pilosacorrelates well with the modeled surface ocean (mixed-layer) bomb pulse curve (Reimer et al. 2009). Based on the results obtained from the shell growth increment assigned to AD 1950, the reservoir age and reservoir correction (ΔR) are 264±23 years and –6±32 years, respectively.

The Zagreb aquifer is the main source of potable water for the inhabitants of the City of Zagreb and Zagreb County. It presents a strategic water reserve protected by the Republic of Croatia. All previous studies related to the definition of the groundwater–surface interaction in the study area have been made based on the isotopic composition of the Sava River from the location of the Domovinski Most bridge, which is located downstream of most pumping well fields. In 2019, a new monitoring station was established at the Podsusedski Most bridge, at the entrance of the Sava River into the Zagreb aquifer, approximately 23 km upstream of the Domovinski Most bridge. Within this research, water isotope data (δ2H, δ18O, deuterium excess) from both Sava River and groundwater sites were used along with hydrologic data to examine the extent to which hydrologic conditions affect the isotope signature and whether the interaction between groundwater and the Sava River causes a change in the isotopic composition of the Sava River. In addition, δ18O amplitudes were estimated for different time periods, as well as the mean residence time for the hydrological year 2019/2020. For that purpose, different statistical methods were applied to the new monthly data for six years for the Domovinski Most bridge and two years for the Podsusedski Most bridge. The δ18O amplitudes vary from 0.22 to 1.86 depending on the time interval and hydrological conditions, while the mean residence time for the hydrological year 2019/2020 was estimated to be about 2.5 months.

During archeological excavations in the Lower Cerovačka Cave (Mt. Velebit, Croatia), the test trench penetrated to a depth of 1.8 m. An undisturbed sequence of sediments was exposed. Considering that caves represent highly efficient sediment traps it was possible to recognize changes in the depositional mechanisms during the Pleistocene–Holocene period. Using the multiproxy approach, the mineralogical, petrographic, and biostratigraphic characterization of the cave sediments was performed. Facies analysis revealed several stages in the development of the clastic filling of cave channels. Allochthonous origin of the sediment was assumed. Sedimentation took place under various conditions from pronounced cold and dry climate during Pleistocene stages in the base of the profile, to humid periods with anthropogenic influence during the Holocene at the very top of the profile. Although traditionally these sediments were believed to be of a Pleistocene age, here for the first time a stratigraphic calibration of the profile has been performed based on luminescence dating of detrital cave sediments and radiometric dating of speleothems.

The 14C method can be successfully applied for determination of biogenic component in any type of samples and different measurement techniques can be applied. For a special case of liquid fuels, direct method by measurement 14C activity of liquid fuel samples in liquid scintillation counter (the „direct LSC method“) has been recognized as a powerful and reliable method of determination of biogenic component (fbio). In the Ruđer Bošković Institute (RBI) Radiocarbon Laboratory we have been implemented our own data evaluation method based on the quench properties of fuels (SQP(E) – Standard Quench Parameter in LSC Quantulus 1220) [1]. We participated in the international intercomparison study ILC/2018 Content of biocomponent in liquid fuel samples, which was organized in 2018 by the Institute of Ceramics and Building Materials (Opole, Poland). Here we compare our fbio results with the fbio-ILC official results and report optimization of the direct LSC method. Laboratories obtained seven samples of diesel type of fuel having different colors. Consequently, the samples resulted in different SQP(E) values when the direct LSC methods was applied. Three samples were analyzed by the AMS (Accelerator Mass Spectrometry) method. The LSC results were quantitatively acceptable for four samples with SQP(E) values above 700 (Figure 1), which was taken as the lowest limit of quantitative fbio determination. Qualitatively acceptable, but quantitatively unacceptable results, were obtained for two samples with the SQP(E) values between 600 and 700, that was defined as the region of limited applicability. For one of the samples the quenching was high, SQP(E) < 600, and the direct LSC method did not give any result. However, all AMS results were acceptable (Figure 1) since AMS does not depend on the sample color. The obtained results have been used for further validation and optimization of the direct LSC method. We defined the limits of applicability of the direct-LSC method for both quantitative (SQP(E) > 700) and qualitative results (600 < SQP(E) < 700). A sample of used edible oil (UEO, laboratory code Z-7226) was used to test these limits. The UEO was a dark sample giving the SQP(E) value of 546 (below the limit of qualitative applicability), while the AMS revealed fbio = 97.9 ± 0.3 % (and δ13C = -29.6 ‰). We mixed the UEO with the (fossil) petrol (benzene) sample (laboratory code Z-6266), which we used as the background sample (fbio = 0 %) with good quenching properties (SQP(E) = 864). We monitored changes in the SQP(E) and fbio values in UEO-petrol mixtures in the concentration range 0 – 100 %. The total mixture volume was 10 mL and 10 mL of Ultima Gold F scintillation cocktail was added, i.e., the measurement was performed in the same manner as all other organic liquid samples [1]. Mixtures of 10 % and 20 % of UEO gave SQP(E) values of 773 and 759, and the fbio was calculated to be 104.0 ± 1.2 % and 101.1 ± 1.3 %, respectively, confirming the quantitative region of SQP(E) values above 700. Mixtures containing 30 – 50 % of UEO resulted in SQP(E) values between 671 and 609, while the fbio values were about 150 %, confirming qualitatively acceptable results. Mixtures containing more than 60 % of UEO had SQP values below 600 and fbio values had a large spread. The presented results showed that the direct LSC method with an evaluation method developed in our laboratory was suitable for determination of the fbio in liquid fuels, providing the correctly defined limits of applicability for highly quenched samples. The RBI Laboratory has a possibility of applying also AMS 14C measurement technique that can satisfactorily determine fbio also in highly quenched samples, but the AMS technique is more complicated and more expensive.

An underwater survey was conducted in September of 2020 on several locations in Kaštela Bay, mainly around the area of Pantan near Trogir, with the aim of assessing the potential of these locations for more detailed investigations. The limited survey gave positive results, as the collected prehistoric and Roman material pointed to a great potential of specific locations for further archaeological research.

Radiocarbon (14C) is both the cosmogenic and anthropogenic isotope. Anthropogenic 14C is produced (1) in atmospheric nuclear bomb tests, and (2) in various nuclear facilities. The bomb-produced 14C has been globally distributed across the planet and can be considered as a new-natural level (clean-air sites). Furthermore, combustion of fossil fuels that do not contain 14C causes increase of atmospheric CO2 concentration and consequently depletion of local 14C levels. Naturally produced CO2 and that formed by fossil fuel combustion are characterized by different content of the stable isotope 13C (d13C values). Therefore, the carbon isotopes (13C and 14C) of the atmospheric CO2 can indicate sources of CO2 at each location, if it is far from nuclear facilities. 14C activity in the atmospheric CO2 in Zagreb, Croatia, has been monitored since 1985. Recently we started monitoring at several other locations with the aim of determining influence of fossil fuel combustion on atmospheric 14C activity and d13C values at clean-air sites and urban sites supposing that the urban sites are affected by fossil fuel uses. A static sampling method has been used for monitoring 14C activity – concentrated NaOH is exposed in a tray for 3-4 weeks. The method is simple and requires neither electric power nor any control, so it can be used at remote sites. However, the method introduces large isotope fractionation in 13C due to high alkalinity of NaOH. Thus, it cannot be applied for monitoring 13C. For the new monitoring program we would like to have a method that can simultaneously deliver both δ13C and 14C activity data. A dynamic method of continuous CO2 collection on NaOH (3M) with a constant air-flow requires source of electricity for pumping and heating, and occasional control of sampler performances. Control of air flow velocity and temperature enables determination of the absorbed CO2 amount. Both static and dynamic sampling methods give an average 14C activity over the sampling period. The amount of collected sample allows benzene synthesis for liquid scintillation spectrometry (LSC-B) that requires about 4 g of carbon. We also developed an instant sampling of atmospheric air in 10-L bags. However, the amount of CO2 is enough for measurement by accelerator mass spectrometry (AMS) that requires about 2 mg of carbon. Comparison of LSC-B and AMS measurement methods resulted in good agreement of 14C activities for samples collected by the static method. The 14C activity of the instant sample revealed comparable results with the samples collected by the static method indicating that the two sampling methods could be combined. d13C values of samples collected by the dynamic method showed no fractionation in 13C and comparable 14C activities with the static method. Instant samples can provide simultaneously 14C activity and d13C values. All 14C activity and d13C data will be used to differentiate carbon of global origin and carbon from local fossil fuel combustion.

The isotope composition of precipitation has been monitored in monthly precipitation at Zagreb, Croatia, since 1976. Here, we present a statistical analysis of available long-term isotope data (3H activity concentration, 2H, 18O, and deuterium excess) and compare them to basic meteorological data. The aim was to see whether isotope composition reflected observed climate changes in Zagreb: a significant increase in the annual air temperature and larger variations in the precipitation amount. Annual mean 18O and 2H values showed an increase of 0.017 &permil, and 0.14 &permil, per year, respectively, with larger differences in monthly mean values in the first half of the year than in the second half. Mean annual d-excess remained constant over the whole long-term period, with a tendency for monthly mean d-excess values to decrease in the first half of the year and increase in the second half due to the influence of air masses originating from the eastern Mediterranean. Changes in the stable isotope composition of precipitation thus resembled changes in the temperature, the circulation pattern of air masses, and the precipitation regime. A local meteoric water line was obtained using different regression methods, which did not result in significant differences between nonweighted and precipitation-weighted slope and intercept values. Deviations from the Global Meteoric Water Line GMWL (lower slopes and intercepts) were observed in two recent periods and could be explained by changes in climate parameters. The temperature gradient of 18O was 0.33 &permil, /&deg, C. The tritium activity concentrations in precipitation showed slight decreases during the last two decades, and the mean A in the most recent period, 2012&ndash, 2018, was 7.6 &plusmn, 0.8 Tritium Units (TU).

The application of tritium, 2H, and 18O in the characterization of the precipitation, groundwater, and surface and lake water of the Plitvice Lakes (PL), Croatia, over the 1979&ndash, 2019 period is presented. An increase in the mean annual air temperature of 0.06 &deg, C/year and in the annual precipitation amount of 10 mm/year is observed. The good correlation of the tritium activity concentration in the PL and Zagreb precipitation implies that the tritium data for Zagreb are applicable for the study of the PL area. The best local meteoric water line at PL was obtained by the reduced major axis regression (RMA) and precipitation-weighted ordinary least squares regression (PWLSR) approaches: &delta, 2HPWLSR = (7.97 &plusmn, 0.12) &delta, 18O + (13.8 &plusmn, 1.3). The higher deuterium excess at PL (14.0 &plusmn, 2.2 &permil, ) than that at Zagreb reflects the higher altitude and influence of the Mediterranean precipitation. The &delta, 2H in precipitation ranges from &minus, 132.4&permil, to &minus, 22.3&permil, and &delta, 18O from &minus, 18.3 &permil, 4.1&permil, The much narrower ranges in the groundwater (&lt, 1&permil, in &delta, 18O, &lt, 10&permil, 2H) indicate the good mixing of waters in aquifers and short mean residence times. The higher average &delta, 2H in all three karst springs observed after 2003 can be attributed to the increase in the mean air temperature. The mean &delta, 2H and &delta, 18O values in the surface and lake water increase downstream due to the evaporation of surface waters. There is no significant difference between the surface water line and the lake water line (2011&ndash, 2014). The stable isotope composition of the surface and lake waters reacts to extreme hydrological conditions.

Methodology and Archaeometry (MetArh) is an annual scientific conference organized since 2013 by the Department of Archaeology of the Faculty of Humanities and Social Sciences of the University of Zagreb, and the Croatian Archaeological Society. The goal of the conference is to entice interdisciplinarity, critical thinking, new insights and approaches as well as new theoretical frameworks in contemporary archaeological science. This, second edition of the conference Proceedings contains eight scientific papers from the 6th MetArh conference which was held at the Faculty of Humanities and Social Sciences of the University of Zagreb, from 6th - 7th of December 2018. Papers are focused on different aspects of archaeological methodology and archaeometry, including case studies from Croatia, Slovenia, Serbia, Greece and Russia. In order to create a volume of high scientific quality, each of the conference paper was reviewed in the peer review process in which the identity of both reviewers and authors, as well as their institutions, are respectfully concealed from both parties.

Methodology and Archaeometry (MetArh) is an annual scientific conference organized since 2013 by the Department of Archaeology of the Faculty of Humanities and Social Sciences of the University of Zagreb, and the Croatian Archaeological Society. The goal of the conference is to entice interdisciplinarity, critical thinking, new insights and approaches as well as new theoretical frameworks in contemporary archaeological science. This, second edition of the conference Proceedings contains eight scientific papers from the 6th MetArh conference which was held at the Faculty of Humanities and Social Sciences of the University of Zagreb, from 6th - 7th of December 2018. Papers are focused on different aspects of archaeological methodology and archaeometry, including case studies from Croatia, Slovenia, Serbia, Greece and Russia. In order to create a volume of high scientific quality, each of the conference paper was reviewed in the peer review process in which the identity of both reviewers and authors, as well as their institutions, are respectfully concealed from both parties.

In this work, we present the results of radiocarbon (14C) dating of three historically important objects related to the period of the reign of the Ottoman Empire in Europe. The following objects from the museum collection of the Franciscan Monastery in Fojnica, Bosnia and Herzegovina were 14C dated: (1) paper from the Ahdname (Fojnička ahdnama); (2) textile of the mantel of Fra Anđeo Zvizdović; and (3) paper from the Fojnica Armorial (Fojnički grbovnik). It was assumed that the Ahdname was issued in AD 1463 by the Ottoman Sultan Mehmed II to the Catholic monks and that the Mantel had belonged to Fra Anđeo Zvizdović, who received the Ahdname. The Fojnica Armorial is an important source of the classical heraldry of the Balkans Peninsula, with various estimates of the age. The 14C calibrated ages of the Ahdname are as follows: lower part, cal AD 1430–1465, upper part, cal AD 1665–1808, proving that only the lower part of the Ahdname was original. The 14C calibrated age of the textile from the outer layer of the Mantel is cal AD 1492–1641, somewhat younger than expected, and inner lining even younger, cal AD 1652–1805. Good coincidence between the calibrated age span of the renewed part of the Ahdname and the lining material of the Mantel can suggest that both objects had been renewed around the same time. Two samples of the Fojnica Armorial were dated: thick paper, cal AD 1631–1667 and thin paper, cal AD 1809–1926, showing that the Armorial had been compiled during different periods.

Izneseni su rezultati arheoloških istraživanja provedenih uz utvrdu Sokol u Konavlima 2012. i 2013. godine, te rezultati antropološke analize i analize radioaktivnim ugljikom 14C. Lokalitet Sokol ima dugi kontinuitet u naseljavanju počevši od prapovijesti do ranog novog vijeka. Istraživanje prostora uz utvrdu podijeljeno je na četiri velike sonde od kojih je najkompleksnija ona uz njezinu južnu stranu. Višefazno groblje smješteno je uz južnu i istočnu stranu utvrde s manjim brojem grobova uz njezinu sjevernu stranu. U svim sondama pronađeni su duboki slojevi formirani potresima koji su bili česti na dubrovačkom području. Ti slojevi su osim grobova i ostataka arhitekture sadržavali i kamene gromade koje su se urušile s utvrde tijekom potresa te mnoštvo raznovrsnih nalaza širokog vremenskog raspona, od prapovijesti do novog vijeka. Utvrda je napuštena 1672. godine. Antropološkom analizom obuhvaćeni su svi pronađeni kosturni ostaci iz bolje i slabije sačuvanih grobnih cjelina, čime su definirani ostaci 92 osobe, od čega 57 odraslih i 35 djece. Pregledom osteološkog materijala također su dokumentirane patološke promjene nastale za života osoba. Određivanje starosti kosturnih ostataka provedeno je metodom 14C. Određena je starost kostura u rasponu od 5. do 19. stoljeća. Istom metodom provedeno je i mjerenje starosti karboniziranih badema koji su datirani u starije željezno doba (750. – 400. cal BC)., This paper presents the results of the archaeological excavations conducted next to Fort Sokol in Konavle in 2012 and 2013, as well as the results of the anthropological analysis and radiocarbon (14C) dating. The site of Sokol has a long occupation continuity starting from prehistory until the Early Modern Period. The excavation of the area adjoining the fort was divided into four big probes, the one next to its southern side being the most complex. Multiphase cemetery is located along the southern and eastern side of the fort, with a smaller number of graves along its northern side. All probes revealed deep layers formed in earthquakes that were common in the Dubrovnik region. In addition to graves and architecture remains, these layers contained stone boulders that fell off the fort in earthquakes and an abundance of diverse finds dating to a broad time span, from prehistory to the Modern Period. The fort was deserted in 1672. Anthropological analysis encompassed all recovered skeletal remains from preserved grave units regardless of the state of preservation, whereby the remains of 92 individuals were identified, of which 57 adults and 35 children. Analysis of osteological material also documented pathological changes developed antemortem. Radiocarbon (14C) dating was applied on skeletal remains resulting in chronological range from the 5th to the 19th century. The same method was used for dating carbonized almonds that were dated to the Early Iron Age (750 – 400 cal BC).

The Aqueduct is one of the city landmarks of Skopje, Republic of North Macedonia. It was part of a water-supply system, with a total original length of about 10 km, while its surface remains are about 385 m long. The age of the Aqueduct is not known—several hypotheses place it to periods between the 6th and 16th centuries. Six mortar samples from different positions of the eastern façade were taken for radiocarbon (14C) dating. In order to extract only the carbon associated to the time of building, three strategies for sample preparation were used: (1) mechanical separation of lime lumps formed during mortar hardening (2) selection on the basis of particle size and the ability to suspend in water induced by ultrasonic shock, and (3) collection of two gas CO2 fractions produced from the same bulk in reaction with acid. Characterization of fractions was performed by isotopic carbon composition and FTIR-ATR analyses. The most plausible results were obtained from lime lump fractions that were dated in the timeframe of 15th to 17th century.

Six sediment cores, the top 30–40 cm, from two lakes of different sizes, Lake Prosce and Lake Kaluđerovac, situated in the karst region of the Plitvice Lakes system, Croatia, were studied by mineralogical and structural, C/N and total organic carbon (TOC) and isotopic analyses (a14C and δ13C of carbonate and organic fractions). The study of the two karst lakes where sediment composition is mainly calcite, showed that organic matter (OM) also plays an important role, and that both fractions analysed simultaneously give a good overview of the processes in the lakes. The morphological and structural properties of the calcite particles at micron and submicron levels indicate that the calcite mineral phase is formed by active authigenic precipitation in the studied lake systems. In the small Lake Kaluđerovac, the measured distributions of carbonate and OM fractions, C/N, TOC, and a14C and δ13C values of both fractions along the sediment depth showed similar values for all three cores, with small variations in each core indicating very homogenous precipitation of autochthonous calcite inside the lake, without allochthonous fraction. In the bigger Lake Prosce, the large difference in sediment composition of the three cores indicated different conditions of sediment precipitation inside the lake. Significant fractions of land-derived carbonate and OM were recognized by mineralogical, C/N, a14C and δ13C values in the shallow, coastal area indicating that the sediment was a mixture of allochthonous and autochthonous fractions. In contrast, the composition of the deep-water sediment in the same lake indicated in-situ calcite precipitation and aquatic OM produced in the lake. Sedimentation rates of 0.7 cm/yr and from 0.3 to 0.7 cm/yr for Lake Prosce and Lake Kaluđerovac, respectively, were determined based on the a14C of macrofossils. Extreme hydrological events in 1981 and 2010 were identified by disturbances in carbon isotopes distributions in sediment profiles. No evidence of anthropogenic influence in either lake on the local level was found, but the response to the global 14C contamination was observed by a14C peaks in both, carbonate and organic fractions. Increased bioproductivity in the recent decades was observed in Lake Prosce which can be correlated with a slight increase in lake water temperature in the last three decades. This process can be associated with enhanced eutrophication in Lake Prosce.

The fraction of biogenic component within various types of materials that can be used as fuels for energy production and transport can be determined by measuring their 14C activity. The method is based on different 14C signatures of the biogenic and the fossil components: while the biogenic component reflects the modern atmospheric 14C activity, no 14C is present in fossil fuels. A direct measurement of the 14C content in liquid fuel by liquid scintillation counter is a simple and fast technique but has a main disadvantage: different liquid colors cause different quenching properties and affect the measurement efficiency. We propose a new evaluation technique that uses liquids of different colors to construct modern and background calibration curves. Various binary mixtures of biogenic liquids have been used to verify the relation between the count rate and the quenching parameter. Mixtures of a biogenic and a 14C-free liquid demonstrated the potential of the proposed technique for determining the biogenic fraction of a mixture.

The analyses of radioactive isotopes 14C, 137Cs and 210Pb, and stable isotope 13C were performed in the sediment cores, top 40 cm, taken in 2011 from karst lakes Prosce and Kozjak in the Plitvice Lakes National Park, central Croatia. Frozen sediment cores were cut into 1 cm thick layers and dried. 14C activity in both carbonate and organic fractions was measured using accelerator mass spectrometry technique with graphite synthesis. 137Cs, 210Pb, 214Pb and 214Bi were measured by low level gamma spectrometry method on ORTECHPGe detector with the efficiency of 32%. Distribution of 14C activity from both lakes showed increase of the 14C activity in the top 10–12 cm in both carbonate and organic fractions as a response to thermonuclear bomb-produced 14C in the atmosphere in the sixties of the 20th century. Anthropogenically produced 137Cs was also observed in sediment profiles. Sedimentation rates for both lake sediments were estimated based on the unsupported 210Pb activity. Different 14C activity of the carbonate fraction (63–80 pMC, percent of modern carbon) and organic fraction (82–93 pMC) is the result of geochemical and biological processes of the sediment precipitation in the lake waters. This is also confirmed by the δ 13 C values of both fractions. Carbon isotope composition, a 14 C and δ 13 C, was compared with the lake sediments from the same lakes collected in 1989 and 2003.

We present a new sea-level reconstruction for the past 1500 years based on biological indicators from the Central Adriatic islands. Biogenic littoral rims built by the coralline rhodophyte Lithophyllum byssoides were found on the particularly exposed sites on the rocky coasts of the islands of Vis, Ravnik and Bisevo in Croatia. The presence of thick and well-developed Lithophyllum rims, considered to be precise (± 10 cm) sea-level indicators, points directly to the rising sea-level environment. Biogenic rims were mapped, measured and sampled for 14C dating. The obtained results point to four phases of sea-level changes. The sea-level was near stable from around 550 till 770 cal AD, in the Dark Ages Cold Period (DACP), then during the Medieval Climate Anomaly (MCA) (770 till 1330 cal AD) the sea-level increased at a rate of 0.71 mm/yr. During the Little Ice Age (LIA) (1330 till 1640 cal AD) it was near stable again. Later, the sea-level started to rise at a much higher rate particularly during the Current Warm Period (CWP). These data were compared with local predictions derived from a glacio-hydro-isostatic models associated with the Last Glacial cycle. If the isostatic–eustatic component is separated, this area seems to have almost stable tectonic conditions during the past 1500 years. Our results show that the large algal rims most likely grew during near-stable sea-level conditions that occurred during two relatively colder periods in the past 1500 years. They also reveal that well-developed (up to 1.8 m wide) upper levels of algal rims were formed during ~ 300 years of stabilisation throughout the LIA.

A new line for preparation of the graphite samples for 14C dating by Accelerator Mass Spectrometry (AMS) in the Zagreb Radiocarbon Laboratory has been validated by preparing graphite from various materials distributed within the Fifth International Radiocarbon Intercomparison (VIRI) study. 14C activity of prepared graphite was measured at the SUERC AMS facility. The results are statistically evaluated by means of the z-score and u-score values. The mean z-score value of 28 prepared VIRI samples is (0.06 ± 0.23) showing excellent agreement with the consensus VIRI values. Only one sample resulted in the u-score value above the limit of acceptability (defined for the confidence interval of 99%) and this was probably caused by a random contamination of the graphitization rig. After the rig had been moved to the new adapted and isolated room, all u-score values laid within the acceptable limits. Our LSC results of VIRI intercomparison samples are also presented and they are all accepted according to the u-score values.

Radiocarbon is a cosmogenic radioisotope equally distributed throughout the troposphere and biosphere. This fact enables its most common application—radiocarbon dating. Natural equilibrium of radiocarbon has been disturbed by diverse anthropogenic activities during the last ∼150 years, enabling also the use of 14C in various environmental applications. Here we present three types of studies by using 14C that were performed in the Zagreb Radiocarbon Laboratory. 14C in atmospheric CO2 has been monitored at several sites with various anthropogenic influences and the difference between the clean-air sites, the industrial city and the vicinity of a nuclear power plant has been established. 14C has been applied in geochronology of karst areas, especially in dating of tufa, speleothems and lake sediments, as well as in studies of geochemical carbon cycle. 14C has been used in various archaeological studies, among which the dating of the early Neolithic settlements in Croatia is presented. In these studies 14C was measured by radiometric techniques, i.e., by gas proportional counting and more recently by liquid scintillation counting (LSC). Two sample preparation techniques for LSC measurement were used: benzene synthesis for archaeological dating and other applications that require better precision, and direct absorption of CO2 for monitoring purposes. The presented results show that various studies by using 14C can be successfully performed by the LSC technique, providing a large enough sample (>1 g of carbon).

Recent sediments in Lake Kozjak, in the Plitvice Lakes National Park, Croatia, were used to study the impact of the material delivered to the lake sediment via Rjecica Brook. Sediment cores, top 40 cm, were taken near the mouth of the Rjecica Brook at three locations in the lake at different distances from the shore, water depth 2-9 m and analyzed using different isotopic and chemical methods. Sediment depth profiles of the following parameters were obtained: organic and carbonate fraction, C/N analyses of organic fraction, 14C activity (a14C) and d13C values of carbonate (d13Ccarb) and organic fraction (d13Corg) and d15N of total nitrogen. The results were compared with sediment core collected in the middle of Lake Kozjak, water depth 21 m. Distribution of organic matter, C/N values, d13Corg and d13Ccarb in sediment profiles showed strong influence of terrestrial organic and carbonate fraction run-off via Rjecica Brook which decreased rapidly in the direction of the open lake. The sedimentation rate as well as the ratio of allogenic and authigenic fraction in sediments was estimated. Lower d13Corg values in surface sediments might be a consequence of the increase in algal productivity but might also be a contribution of fossil fuel combustion. The anthropogenicaly induced 14C in the atmosphere in 1963/64 is visible though shadowed in sediments.

In the Zagreb Radiocarbon Laboratory radiocarbon dating has been performed by a gas proportional counting and a liquid scintillation counting techniques. Recently, we implemented a graphite target production for 14C measurement by accelerator mass spectrometry (AMS). The graphite preparation rig was constructed with the help of Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Laboratory within the EU FP6 project AMS-14C and the IAEA project CRO/8/006. Pre-treated organic samples (AAA method) are combusted to CO2 at 850°C over night in pre-combusted, evacuated and sealed quartz tubes in presence of CuO and Ag. The amount of CO2 corresponding to 1.5 mg of carbon is transferred from the cracked tube to the reduction line. Graphite is obtained by the reduction of CO2 with zink and iron as catalyst at 450°C. During the reduction reaction, pressure is monitored on PC and the reduction yield is calculated. The graphitization line consists of 4 units for simultaneous preparation of 4 samples. The graphite targets were measured at the SUERC Accelerator Facilities. The operation of the rig was tested by preparation of graphite from samples of known 14C activities. The graphitization yield was high (>95%) for all 4 graphitisation units. The borehole gas (CO2) activities were within the background range normally measured at SUERC, showing that our graphitization rig can satisfactory produce background samples. Here we present the first results of about 100 graphite samples prepared on a new graphitization line (and measured at SUERC): various background samples (anthracite, marble, borehole CO2), standard activity samples, and samples from the VIRI intercomparison. Use of several radiocarbon measurement techniques in our Laboratory initiated a need for development of a new relational database ZAGRADA (Zagreb Radiocarbon Database) since the existing software package could not support parallel processing of several techniques. Some characteristics of the new database will be presented.

Prirodna ravnotežna 14C aktivnost u atmosferskom ugljikovu dioksidu i u biosferi narušena je na globalnoj razini ljudskom djelatnošću. Intenzivni termonuklearni atmosferski pokusi sredinom 20. stoljeća uzrokovali su naglo povišenje 14C aktivnosti u atmosferi na razinu gotovo dvostruko višu od prirodne, a nakon zabrane pokusa 14C aktivnost se smanjuje i danas je gotovo dosegla prirodnu ravnotežnu vrijednost. U ovom su radu prikazani rezultati praćenja 14C aktivnosti u atmosferskom CO2, godovima drveća i biološkim uzorcima na nekoliko karakterističnih lokacija na području Hrvatske i Slovenije. Globalne promjene 14C aktivnosti opažaju se i na “čistim” lokacijama u zaštićenim područjima. U urbanim sredinama opažaju se lokalni efekti sniženja 14C aktivnosti u atmosferi zbog povećanog izgaranja fosilnih goriva, što je posebno izraženo u zimskim mjesecima. U okolici nuklearne elektrane opaža se povišenje 14C aktivnosti u atmosferskom CO2 za vrijeme i neposredno nakon izmjene gorivih elemenata, a ako se remont provodi početkom vegetacijskog razdoblja, tada se opaža povišena 14C aktivnost i u biljkama iz neposredne okolice., The natural equilibrium of 14C activity in atmospheric CO2 and in the biosphere has been disturbed globally by various anthropogenic activities. Intensive atmospheric thermonuclear bomb tests in the mid 20th century doubled the natural 14C activity in the atmosphere. Since the bomb test ban, this activity has constantly been decreasing and has almost reached its natural level. This article presents the results of 14C activity monitoring in atmospheric CO2, tree rings and biological samples at several locations in Croatia and Slovenia. Global changes in 14C activity have been observed at “clean-air” sites. In urban areas, lower atmospheric 14C activity is owed to intense fossil fuel combustion, especially in the winter. Higher 14C activity is observed in near the nuclear power plant during and immediately after refuelling outage. If refuelling is performed in the spring, when plants start to vegetate, increased 14C activity is also refl ected on them.