Recent carbon sequestration dynamics in four temperate SE European peatlands using 210Pb dating.

The last two centuries' anthropogenically-accelerated climatic changes and elevated atmospheric levels of CO2 are influencing the recent carbon sequestration dynamics of peatlands, resulting in high variations of growth rates, and a general ascending trend in apparent carbon accumulation rates. In the present work, 210Pb high-resolution chronologies and 137Cs alternative markers were employed to study the recent carbon-related peat properties and their evolution throughout the last two centuries in four Sphagnum-dominated bogs in SE Europe (Romania). The results revealed a recent apparent carbon accumulation rate ranging from 9.5 to 437.5 g C m-2 yr-1, with a mean value of 144 ± 90.1 g C m-2 yr-1, that yielded an average increase of 18.25% of the rate from 1950 to the present period, suggesting an enhanced contemporaneous C uptake and storage in the peatlands. The mean C storage per unit area was 17.6 ± 7.6 kg C m-2. The periods of decreased peat growth rates were identified and attributed to significant drought events at the regional scale. The results found in the present study confirm the observations and trends remarked by other researchers in the literature, and further reinforce the relevance of studying recent carbon dynamics in peatland ecosystems. The obtained 210Pb chronologies were validated by 137Cs markers, highlighting the suitability of this technique for peat profile dating.

Investigation of sedimentation rates and sediment dynamics in Danube Delta lake system (Romania) by 210Pb dating method.

Being a dynamic environment associated with complex costal, fluvial and marine processes, only a few studies regarding the evolution of the Danube Delta and the human impacts on its ecosystem have been carried out. Being a sensible to all processes occurring in its catchment area, information is stored in the deposited sediments, which can be used as tracers for natural and anthropogenic processes. The aim of this study is to determine a detailed reconstruction of the sedimentation rates in the last century by applying the 210Pb dating method validated by 137Cs profiles. Additionally, the impacts of the construction of river-regulating structures (mainly the Iron Gates Hydro-Energetic Power Plants) are investigated, along with the assessment of natural phenomena (floods, storms etc.). To achieve this, 26 sediment cores from seven lakes were collected. 210Pbsup and 137Cs were determined using gamma spectrometry, while 210Pbtot was measured via alpha spectrometry (210Po), using the CRS model for age determination. From the assessed lakes, the most affected was the Matița Lake with a maximum sedimentation rate of 10.93 g cm-2 yr-1 and the least affected was the Isac Lake. Average sedimentation rates are: 0.95 g cm-2 yr-1 for Cruhlig Lake, 0.70 g cm-2 yr-1 for Uzlina Lake, 0.44 g cm-2 yr-1 for Isac Lake, 0.47 g cm-2 yr-1 for Cuibida Lake, 0.51 g cm-2 yr-1 for Iacob Lake, 1.00 g cm-2 yr-1 for Matița Lake and 0.76 g cm-2 yr-1 for Merhei Lake. Physical parameters (water content, porosity and bulk density) and LOI (organic matter and inorganic carbon content) were determined for each core to differentiate organic and non-organic sedimentation. Beside the natural influences, it is difficult to track the effects of the Iron Gates and not all analysed lakes were suitable for this task. The 1940-1970 period and the following ten years were compared in means of sedimentation: a decrease in sedimentation can be observed in four of the lakes: 59% in Cruhlig Lake, 16% in Uzlina Lake, 10% in Iacob Lake and 42% in Isac Lake, leading to an average 32% for the four lakes. The other three lakes show increasing tendencies of 39% in this period: 87% in Matița Lake, 6% in Merhei Lake and 24% in Cuibida Lake. Sedimentation rates show growths of 3 times after 1989, the most affected being the two northern lakes (3 times increase in both Matița Lake and Merhei Lake) and the four central lakes (2 times in case of Cuibida Lake, 3 times in Iacob Lake, 3 times in Isac Lake and 4 times in Uzlina Lake) with an average increase of 3 times, while the southern one (Cruhlig Lake) 2 times.

137Cs contamination over Transylvania region (Romania) after Chernobyl Nuclear Power Plant Accident.

Following the radionuclide releases due to Chernobyl Nuclear Power Plant accident, various studies were completed by researchers all over the world in order to measure the surface contaminations by artificial radionuclides. The aim of this study was to evaluate 137Cs surface contamination and to create an inventory distribution for Transylvania region (Romania) after the Chernobyl event using γ spectrometric measurements on soil samples collected from 153 locations. The results were compared to measured data from the Danube Delta and Moldova Republic, as well as to 137Cs concentrations from the rest of Europe reported by literature. The 137Cs surface concentrations in soil samples ranged between 0.4±0.1kBqm-2 and 301.1±3.0kBqm-2, having an average of 8.3±0.2kBqm-2, with more elevated values in the mountain areas (18.3±0.6kBqm-2) compared to the hills and plains (2.6±0.1kBqm-2). Taking into consideration the cardinal regions, the northern and western regions received the least amount of 137Cs (2.9±0.1kBqm-2), while the southern part received 16.3±0.6kBqm-2. Sampling points with eastern slope exposure received the highest average (27.8±0.5kBqm-2), while southern, north-western and north-eastern ones received less than 8kBqm-2. Two hotspots are reported at Iezer-Ighiel (72.7±5.9kBqm-2) and Tulgheș areas (51.5±0.6kBqm-2).

Atmospheric flux, transport and mass balance of (210)Pb and (137)Cs radiotracers in different regions of Romania.

This study focuses on the determination of (210)Pb and (137)Cs fluxes from different areas in Transylvania, Romania and on the determination of transport and mass balance within the lacustrine system of Red Lake. In order to achieve this, samples were taken from six different locations (Bihor County area, Ighiel area, Red Lake area, Mluha Peatbog, Mohos Peatbog and Zanoaga Rosie Peat bog in the Semenic Mountains) throughout Romania, these being compared to the values of the Danube Delta area. The activity concentrations of the soil samples were measured by gamma spectrometry (HPGe detector) for both (210)Pbtotal, (210)Pbsup ((226)Ra) and (137)Cs, while peat samples were measured by both alpha ((210)Po) spectrometry (PIPS detectors) as well. The mean value for the (210)Pb flux was measured in the Danube Delta region (42±8Bqm(-2) yr(-1)), while the highest was measured in the Semenic Peatbog (227±54Bqm(-2) yr(-1)); the average being 132±8Bqm(-2) yr(-1). In case of (137)Cs the mean was 298±3Bqm(-2) yr(-1), maximum being 1683±15Bqm(-2) yr(-1) in case of Ighiel area and minimum being 32±1Bqm(-2) yr(-1) in the Danube Delta region. In case of the Red Lake, from the total inventory of 410±23Bqm(-2) yr(-1) in the sediments, the loss by outflows is 100±12Bqm(-2) yr(-1), the catchment to lake transfer factor being 0.84%.

The activity concentration of 210Po in Romanian commercial cigarettes and the radiation exposure estimation derived from their regular consumption.

Due to the relatively high activity concentrations of (210)Po that are found in tobacco, cigarette smoking has been found to be the principal pathway of the intake of this radionuclide. The (210)Po concentrations in the lung tissues may contribute significantly to an increase in the internal radiation dose and in the number of instances of lung cancer observed among smokers. The study of (210)Po in tobacco is required due to its potential for human radiation exposure through ingestion and inhalation. The risk factor caused by (210)Po in Romanian commercial cigarettes is not yet evaluated. Ten of the most frequently smoked brands of cigarettes sold in Romania were investigated in this work for this purpose. The activity concentration of (210)Po was determined by alpha spectrometry using a PIPS detector after chemical leaching and spontaneous deposition of (210)Po on a stainless steel disc from diluted HCl solution. The samples were spiked with (209)Po for chemical recovery calculation. The (210)Po activity concentrations of the measured types of cigarettes ranged from 4.65 to 10.22 mBq sample(-1) and the resulted average concentration of (210)Po isotopes is 8.35±0.80 mBq cigarette(-1) (the errors form a 2σ interval of confidence). When comparing the results of this study with the activity concentration values reported by other countries it was found that the results of this study are in the lower end of the world range. The estimation of this study shows that cigarette smokers, who are smoking one pack (20 cigarettes) per day, are exposed to an effective dose of 75.51 µSv y(-1).