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The paper presents the results of measurements the specific concentration of lead-210 for six peat profiles representing four peat bogs from two regions of Poland and the problem of creating age-depth models. For the construction of age-depth models, it is proposed to use mathematical functions, the best fit to the measured activity. The F-statistics were used as a measure of the match quality. The obtained models are visualized in two ways – showing the age calculated on the basis of direct measurements of activity and indicating points that are the results of the used approximation. Such visualization is important to clearly distinguish the places of the age-depth model that result from the measurements of activity from those places that are the result of the approximation used. This paper proposes and tests the application of activity modelling for the cores shorter than the range of the lead method. The paper also outlines the limitations and potential dangers related to the interpretation of core dating results i) obtained by using the activity approximation resulting in the smoothing of the age-depth profile, and ii) for the cores of a length smaller than the depth of the presence of the unsupported lead. Additionally, the proposed models were compared with the models obtained by using SIT, Mod-Age, OxCal, Clam, and Bacon programs.

A one-meter long peat core was taken from the peatland in Wolbrom (Silesian-Cracovian Upland, southern Poland). The analysis of the botanical composition showed that Wolbrom is a fen. Vegetation species such as Carex rostrata and Phragmites australis have been found. An age-depth model was constructed using 12 conventional radiocarbon dates and 13 lead-210 dates from the upper part of the deposit. In this work, the results of radiocarbon dating are presented. According to the model, we can estimate the age of the fen. The oldest part comes from a depth of 1.05 meter and its conventional age is 5940 ± 95 BP (modelled date 5000–4790 BC, 68.2% probability interval). The accumulation rate varies between approximately 0.53 mm·yr-1 and 6.48 mm·yr− 1. The core has been also tested for the presence of trace elements (Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) using ICP-OES. There are considerable variations in the concentrations of the tested metals – in many cases the concentration starts to rise at about 40 cm and may be connected with the human activity. This depth corresponds to the modelled age intervals 355–300 BC (17.4%) and 205–45 BC (50.7%).

Fens are underestimated carbon sinks. Knowledge about their role in the sequestration of CO2 in the past is limited. The research reported here focused on identifying long-term carbon accumulation rates (CARs) in a drained fen (Bagno Bruch) and a waterlogged fen (Bagno Mikołeska) in southern Poland. On the basis of 210Pb and AMS 14C dates and age–depth modeling, 7000- and 2000-year records of changes in bulk composition and carbon and sulfur content are presented and discussed. Strong human impact is detected, especially in Bagno Bruch. However, minor climatic signals linked to the ‘Little Ice Age’ and to the influence of wind-blown sands are also evident. The sand may have influenced the plant composition, peat accumulation rates (PARs), and CARs, in addition to the bulk composition at Bagno Mikołeska. The mean value of the CAR in the youngest peat layers spanning the last 200 years is generally lower in two cores from Bagno Bruch ( c. 85 and 86 g/m2/yr) than in two cores from Bagno Mikołeska ( c. 140 and 142 g/m2/yr). The fens are characterized by higher CARs compared with boreal peatlands. The reproducibility of the CAR values is the most promising result, suggesting the low mobility of 210Pb and the reliability of this method in assessing the chronology of fens.

The mineralogical composition of a 40 cm subsurface layer of transitional mire ‘Bagno Bruch’ (southern Poland) polluted with atmospheric dust was studied using scanning electron microscopy. The mire is located 9 km to the east of a zinc smelter on the northern limit of industrial Upper Silesia in southern Poland. Concentrations of zinc, lead and cadmium reach values of 494, 238 and 16 mg kg −1 , respectively, in the peat layer. Inorganic particles in the peat were grouped into two main categories based on their origin: air dust particles of anthropogenic- and natural sources, and authigenic minerals that originated within the mire. Anthropogenic particles comprise an important part of the inorganic particles in the peat. As they are typically enriched in heavy metals, their stability is critical to controlling metal mobilities. Spheroidal aluminosilicate fly-ash particles are the most common- and most stable anthropogenic pollutants. Partially dissolved Pb-bearing particles (sulphides, chlorides and oxides) and ZnS occur as trace components throughout the peat profile. The prolonged existence of the particles made them susceptible to gravitational relocation in the peat and limits the biogeochemical cycling of the constituent elements. The least resistant Fe (hydro)oxides release Zn and minor amounts of Mn, Mg and Sn due to reductive dissolution. The released Zn is immobilized in the form of ZnS spherules, 1–3 μm in diameter, approximately 10 cm further down in the profile. The investigation shows that the behaviour of trace elements in polluted peatland is controlled by mineral dissolution/precipitation processes. The formation of authigenic minerals (ZnS, barite, gypsum) indicates complex redox conditions and element redistribution in the transitional mire.

Application of α and γ Spectrometry in the 210Pb Method to Model Sedimentation in Artificial Retention Reservoir The paper describes the application of the 210Pb method for creating a comprehensive model of sedimentation in the retention reservoir Kozłowa Góra during the 60 years of its use. The model takes into account the temporal and spatial change in the sedimentation conditions. Because of the specific conditions of the young artificial lake, the techniques available to date are not sufficient and it was necessary to modify the 210Pb method. The paper describes such modification of the method and its application to dating the sediments in the reservoir. For a young lake it is impossible to estimate the activity of authigenic 210Pb with the application of alpha spectrometry because even the oldest sediments contain allochthonous 210Pb. The determination of the activity of authigenic 210Pb in the sediments of the studied reservoir was possible only thank to gamma spectrometry. The gamma ray spectrometry consists of measurements of gamma photons emitted by 210Pb, 214Pb and 214Bi isotopes. Analysis of the 210Pb gamma spectrum line yields information about total activity of 210Pb, while the assessed activity of 214Pb and 214Bi equals to the activity of authigenic 210Pb.

Drawing the Optimal Depth-Age Curve on the Basis of Calibrated Radiocarbon Dates The radiocarbon determination of age has the form of a complicated probability density function. In some cases however it is possible to exploit it in a precise way, in drawing the depth-age curve when a stratigraphic sequence of 14C ages is available. It is also possible to use this function in drawing the depth-age curve by hand. The necessary additional constraint on the depth-age curve adopted here is the simplicity of its shape, namely the low curvature.