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Coal mined in the shut-down Raša mine in Istria, Croatia had a high organic sulphur content. What has remained of its local combustion is a coal and ash waste (legacy site) whose trace element and radionuclide composition in soil has enduring consequences for the environment. The aim of this study was to follow up on previous research and investigate the potential impact on surrounding soil and local residents by characterising the site’s ash and soil samples collected in two field campaigns. Trace elements were analysed using particle induced X-ray emission (PIXE) analysis. Radionuclides, namely 232Th, 238U, 226Ra, 210Pb, and 40K, were analysed with high resolution gamma-ray spectrometry. PIXE analysis confirms previous findings, whereas radionuclide analysis shows higher activity concentrations of 238U, 226Ra, and 210Pb in ash samples than the worldwide average, and the absorbed dose rates for local residents are up to four times higher than background levels. Our findings confirm the need of investigating coal industry legacy sites and the importance of remediation of such sites.

The invasion of Ukraine and military operations around Ukrainian nuclear power plants and other nuclear facilities have prompted us to search for radiocaesium in mosses from the Kopački Rit Nature Park in Croatia, since mosses are known bioindicators of airborne radioactive pollution, and Kopački Rit is a known low radiocaesium background area. Sampling was finished in August 2023, and our analysis found no elevated radiocaesium levels. Kopački Rit therefore remains a suitable place for future detection of anthropogenic radioactive pollutants.

Official control of EU market foodstuffs repeatedly reports high nicotine levels in dried wild mushrooms without any clear scientific consensus about their origin. The advised constant monitoring calls for improvements to existing methods. For this purpose, our aim was to develop a headspace solid phase microextraction (HS-SPME) method coupled to gas chromatography with mass spectrometric detection (GC-MS) that would eliminate the need for extensive sample pre-treatment. The type of fiber coating, amount of sample, extraction temperature and time, desorption time and salt addition were investigated and optimized as parameters affecting the SPME procedure. The optimized conditions were used to validate a quantitative method for nicotine analysis by matrix-matched calibration and isotopically labelled internal standard correction. The method provided good linearity (r2= 0.9994) over the tested concentration range (0.025–1 mg kg−1), low detection limit (0.005 mg kg−1) and low quantification limit (0.017 mg kg−1) for nicotine, being below the EU foodstuff regulations. For both of the tested concentration levels (0.050 and 0.200 mg kg−1), precision expressed as relative standard deviation was below 10% (4.5% and 8.5%, respectively), while accuracy was 98.2% and 100.3%. The optimized method was then used to determine nicotine levels in 18 samples of dried Boletusmushrooms from southeastern European countries entering the EU market. We demonstrated our HS-SPME procedure to be fast, simple, sensitive, solvent-free, cost-effective and thus suitable for controlling consumer safety regarding nicotine level in dried mushrooms.

Papuk Nature Park, unlike most similar parks and preserves in the world, contains active quarries. Quarries dig stone from the ground, creating dust and exposing deeper, potentially more radioactive layers. Since the forest trails in the Park lead right up to the quarries, we believed it was important to determine the radiological impact of the quarries on the Park environment. We measured ambient dose rate equivalent H*(10) and sampled moss at 26 Park locations along two of four quarries, along the road between them, and near Lake Orahovac, a very popular tourist destination close to the quarries. Moss is a standard bioindicator of exposure to heavy metals, including radionuclides. Using-gamma ray spectrometry we determined the activity concentration of 137Cs and of representative naturally occurring radionuclides – 238U, 226Ra, 210Pb, 232Th, and 40K – in sampled moss. H*(10) at selected locations was similar to the background H*(10) measured continuously all over Croatia. The ranges of measured activity concentrations of 137Cs and naturally occurring radionuclides in moss did not differ significantly from other parts of Croatia and nearby countries.

Phosphogypsum (PG) is a waste by-product (residue) originating from the production of phosphoric acid and phosphate fertilisers. PG contains chemical and radioactive impurities, which is why it is mostly stockpiled in controlled areas. Worldwide, only about 15 % of PG is recycled or reused. Today, policies and business strategies prioritise sustainable development through circular economy, which certainly includes PG. This provides new opportunities for Croatia to manage its PG and make an effort to use it as an additive in different industries, such as agriculture and construction. Due to its chemical and radiological properties, PG can potentially cause problems for the environment and human health. Hence, before using PG, detailed knowledge of potential hazards is necessary to protect people and the environment. The aim of this review is to summarise available data on Croatian PG, compare them with other countries, and to identify knowledge gaps and the lack of data on potential hazardous substances in PG in order to assess the opportunities of using PG in Croatia.

We took samples of uncultivated soil from the surface layer (0–10 cm) at 138 sites from all over Croatia and measured their radionuclide activity concentrations with high-resolution gamma-ray spectrometry. This second part of our report brings the results on 40K and 137Cs to complement those on the 232Th and 238U decay chains addressed in the first part. Together they give the most complete picture of radioactivity of Croatian soil so far. Activity concentrations of 40K were the highest in the Pannonian region, and there was an opposite trend for 137Cs. We found that the concentrations of 137Cs tended to increase with altitude, annual precipitation, and vegetation density. The concentration ratio of 137Cs and K in soil, which indicates the potential for 137Cs entering food chains via uptake by plants, was the lowest in agriculturally important areas in the east of the Pannonian region. In addition, we used the obtained results on activity concentrations to calculate the related absorbed dose rate as a measure of external exposure to ionising radiation from soil. The sum of the absorbed dose rates for naturally occurring radionuclides and 137Cs showed that external exposure was generally the highest in the Dinaric region and Istrian Peninsula.

The assessment of environmental radioactivity much relies on radionuclide content in soil. This stems from the significant contribution of soil to both external and internal exposure to ionising radiation via direct emission of gamma radiation and soil-to-plant radionuclide transfer, respectively. This motivated us to carry out a systematic research on the radioactivity of soil in Croatia to obtain relevant data that can be used as a basis for understanding the related effects of geomorphological, biogeographical, and climatological properties of the environment. We collected samples of the surface layer of uncultivated soil (0–10 cm) at 138 sites from all over the country and measured them for radionuclide activity concentrations by means of high-resolution gamma-ray spectrometry. This resulted in radioactivity maps containing data on activity concentrations of representative radionuclides in the environment. In this paper, which is the first in our two-part presentation, we focus on the naturally occurring 232Th and 238U decay chains and their correlations with the diversity of Croatian regions. For both of the chains, activity concentrations were the highest in the Dinaric region, the lowest in the Pannonian region, and intermediate in the Adriatic region. Relatively high concentrations of 226Ra in the soil of the Dinaric region implied a possibility of an enhanced emanation of its progeny 222Rn into the air. Activity concentrations of 210Pb were additionally elevated in areas with dense vegetation, most probably due to an atmospheric deposition of airborne 210Pb onto the surface of plants and their eventual decomposition on the ground.

In situgamma ray spectrometry was developed to quickly measure large areas of land following nuclear accidents. However, a proper calibration of detectors for in situmeasurements is a long and complicated process. One tool designed to make this calibration quick is the InSiCal software. We compared 5,000 s in situmeasurements with two different HPGe detectors calibrated using the InSiCal software and laboratory measurements of samples collected at the same locations. Our findings suggest that in situgamma spectrometry using InSiCal software can provide reasonably accurate data, but some improvements are needed.

This paper presents the results of long-term investigations of 137Cs and 134Cs activity concentrations in drinking water in the city of Zagreb for the period 1987–2018. The highest activity concentrations of both radio-nuclides were measured in 1987, decreasing exponentially ever since, while 134Cs in several subsequent years fell under the detection limit. After the Fukushima Daiichi accident in 2011, the presence of 134Cs in drinking water was detected again. The environmental residence time for 137Cs was estimated to be 8.1 years in drinking water and 5.7 years in fallout. The correlation between 137Cs in fallout and in drinking water is very good, and this indicates that fallout is the main source of water contamination. The observed 134Cs/137Cs activity ratio in drinking water for the post-Chernobyl period was similar to the ratio found in other environmental samples. The estimation of annual effective doses received by the adult members of the Croatian population due to the intake of radiocaesium in drinking water showed quite small doses of 0.28 μSv in 1987 decreasing to 2.5 nSv in 2018, which indicated that drinking water was not a critical pathway for the transfer of radiocaesium to humans.

This article gives an overview of physical concepts important for radioecology and radiotoxicology to help bridge a gap between non-physicists in these scientific disciplines and the intricate language of physics. Relying on description and only as much mathematics as necessary, we discuss concepts ranging from fundamental natural forces to applications of physical modelling in phenomenological studies. We first explain why some atomic nuclei are unstable and therefore transmute. Then we address interactions of ionising radiation with matter, which is the foundation of both radioecology and radiotoxicology. We continue with relevant naturally occurring and anthropogenic radionuclides and their properties, abundance in the environment, and toxicity for the humans and biota. Every radioecological or radiotoxicological assessment should take into account combined effects of the biological and physical half-lives of a radionuclide. We also outline the basic principles of physical modelling commonly used to study health effects of exposure to ionising radiation, as it is applicable to every source of radiation but what changes are statistical weighting factors, which depend on the type of radiation and exposed tissue. Typical exposure doses for stochastic and deterministic health effects are discussed, as well as controversies related to the linear no-threshold hypothesis at very low doses.

For years, the town of Slavonski Brod in Croatia has been facing serious problems with air pollution, which is usually attributed to an oil refinery across the Sava River in Bosnia and Herzegovina. While the air quality is being monitored rigorously with regard to nonradioactive matter, no attention has been paid to the possibility of a coincidental radioactive pollution. This study is the first to have addressed this issue. We measured ambient dose rate equivalents at 150 sites and found that none exceeded 120 nSv h-1, while the average was 80 nSv h-1. Gamma-ray spectrometry of the collected river water and soil samples did not reveal any unusual radioactivity either. In other words, we have found no evidence of radioactive pollution that would endanger the health of the residents of Slavonski Brod.

This paper tackles the issue of interpreting the number of airborne particles adsorbed on a filter through which a certain volume of sampled air has been pumped. This number is equal to the product of the pumped volume and particle concentration in air, but only if the concentration is constant over time and if there is no substance decomposition on the filter during sampling. If this is not the case, one must take into account the inconstancy of the concentration and the decay law for a given substance, which is complicated even further if the flow rate through the filter is not constant. In this paper, we develop a formalism which considers all of these factors, resulting in a single, compact expression of general applicability. The use of this expression is exemplified by addressing a case of sampling airborne radioactive matter, where the decay law is already well known. This law is combined with three experimentally observed time dependence of the flow rate and two models for the time dependence of the particle concentration. We also discuss the implications of these calculations for certain other situations of interest to environmental studies.

Phosphogypsum (PG) is a waste product (residue) from the production of phosphoric acid characterized by technologically enhanced natural radioactivity. Croatia’s largest PG deposition site is situated at the edge of Lonjsko Polje Nature Park, a sensitive ecosystem possibly endangered by PG particles. This field study investigates two aspects relevant for the general radiological impact of PG: risk assessment for the environment and risk assessment for occupationally exposed workers and local inhabitants. Activity concentrations of natural radionuclides (238U, 235U, 232Th, 226Ra, 210Pb, and 40K) were measured in the PG (at the deposition site), soil, and grass samples (in the vicinity of the site). The ERICA Assessment Tool was used to estimate the radiological impact of PG particles on non-human biota of the Lonjsko Polje Nature Park. The average annual effective dose for occupationally exposed workers was 0.4 mSv which was within the worldwide range.