Search

14C and 210Pb methods are regularly used to determine ages and accumulation rates of peat, fen and lake sediments. The overall aim is to estimate the age of discrete layers, which were analysed for environmental proxies. Ideally, the age-depth models should fit the investigated proxy in terms of resolution and give precise results. Nevertheless, the differences in the nature of dating methods and statistical treatment of data need to be considered.Both 14C and 210Pb signals are integrated over a considerable period. Moreover, they originate from different sources. 210Pb is bound to aerosols and trapped by peat while 14C is bound from atmospheric CO2 by photosynthesis. Hence, 210Pb gives the time span during which the aerosol has been buried, whereas the 14C date gives the time of death of a plant.After the analysis, the results are usually combined into an age-depth model. This process involves statistical treatment of data during which specific assumptions and simplifications are made. Depending on the algorithm, they lead to alterations in modelled ages compared to unmodelled data. Principally it is a desired result–increasing the robustness and decreasing the uncertainty of the age-depth model. In worse cases models alter the modelled ages to an unacceptable extent, which may be overlooked if the results are treated automatically.We test the performance of various age-depth modelling algorithms (OxCal P_Sequence, Bacon, clam, MOD-AGE) on a selected true dataset where 14C and 210Pb data overlap and are used simultaneously. Afterwards, a point estimate is selected and used for proxy analysis on a time scale and for calculation of the accumulation rates. We also check the influence of 210Pb calculation method (CRS, ModAge, extrapolation technique) on derived age-depth models.Together with the thickness of analysed samples the age model provides an information about the time resolution of proxy analysis. While the age-depth curves, except outstanding circumstances, give relatively similar answers within 95% uncertainty ranges, the differences are observed in point estimates and accumulation rate, and they may be relevant for the palaeoenvironmental studies. With this exercise we attempt to assess the uncertainty beyond simple age errors reported from the measurements and age-depth modelling.

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.

The accumulative fan was formed at the mouth of a well-developed system of erosive cuts in the lower Serteyka River valley in western Russia. The length of the fan reaches 70 m, and its thickness is up to 2 m. The erosive cuts (gullies) were formed on the steep and short slopes of the tunnel valley (transformed later into the river valley) and dissect the surface of the glaciofluvial plain for a length of ca. 110 meters. The absolute chronology of the development of that relief form was determined based on 14C and 210Pb data set. It was started at the earliest in the second half of the 17th century, and finished before the mid-19th c. AD. These processes can be correlated therefore with palaeoenvironmental changes during the pessary of the Little Ice Age (LIA), as well as with human impact during the agrarian and industrial revolution in Eastern Europe. Studied accumulative fan is formed of deluvium with the insertion of the proluvium and an agricultural diamikton which is developed in ceiling part. The research based on the results of analysis of depth diversity of textural features (mean grain-size diameter, sorting index, skewness and kurtosis), geochemical features (chemostratigraphy determined on the basis of X-ray fluorescence spectroscopy – XRF) of the fan’s sediments and palaeoecological features (palynology analysis, subfossil Chironomidae and Cladocera analysis, plant macrofossil analysis) of biogenic deposits from under the fan.

In the region of the Serteyka River, an extensive accumulative fan was studied. The main goal of the research is an attempt to reconstruct the palaeogeographic development of erosive cuts in Western Russia. The geological structure of the fan and its surroundings was recognized. The fan is built by deluvium sediments, which can be divided into: lower diluvium unit, middle diluvium unit and upper diluvium unit. The top of the fan is built by tillage diamicton. The fan was formed at the earliest from the 2nd half of the 17th century (during the Little Ice Age pessimum). Samples were taken for AMS, OSL, Pb210 dating to determine the phases of fans development. The AMS dating produced mixed results. This was due to the redeposition of the material. Using the OSL method, two samples were dated from the bottom of the clastic fan deposits. Dates from the Neolithic period were obtained, additionally in inversion. It was caused by inaccurate bleaching of the quartz grains. The top part of the fan was dated using the Pb210 method. Slope sediments can be extremely difficult to dating. This may be due to the redeposition of the material, the presence of hiatuses and inaccurate bleaching of samples. The individual units of deluvium sediments differ in colour, structural and textural features.

We reconstruct palaeoenvironmental changes since the Late Holocene in the Orava–Nowy Targ Basin, with an emphasis on anthropogenic influence (Walker et al., 2018). This reconstruction employs multiproxy analyses of the Otrebowskie Brzegi poor fen. We combined radiocarbon and 210 Pb dating with elemental geochemistry, stable lead isotopes, and palaeobotanical analyses. The core we investigated covers a period from 4200 ± 100 BC to the present, with a peat accumulation rate varying between 0.001 and 0.243 cm y –1 . Heavy metal concentrations, Pb isotopic ratios, and a palynological analysis revealed a significant impact of human activities in the past. The highest concentration and accumulation rate of Pb, were found around 1950 AD. The 206 Pb/ 207 Pb quotient ranged between 1.168 and 1.223, with average value around 1.198. Most of the interpretation was based on Pb and its stable isotopes; however, other elements were also important indicators of natural and anthropogenic environmental changes. Our results revealed similarities between the geochemical composition of the peatland studied and other peatlands from the Orava–Nowy Targ Basin.

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.

International audience; A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD,1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 < Sum REE/Sc < 25) and the eNd variability (-13 to -9) are interpreted by a mixing between dust particles from local soils and long-range transport of desert particles. Three periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD,600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

International audience; The objective of our study was to determine the trace metal accumulation rates in the Misten bog, Hautes-Fagnes, Belgium, and assess these in relation to established histories of atmospheric emissions from anthropogenic sources. To address these aims we analyzed trace metals and metalloids (Pb, Cu, Ni, As, Sb, Cr, Co, V, Cd and Zn), as well as Pb isotopes, using XRF, Q-ICP-MS and MC-ICP-MS, respectively in two 40-cm peat sections, spanning the last 600 yr. The temporal increase of metal fluxes from the inception of the Industrial Revolution to the present varies by a factor of 5e50, with peak values found between AD 1930 and 1990. A cluster analysis combined with Pb isotopic composition allows the identification of the main sources of Pb and by inference of the other metals, which indicates that coal consumption and metallurgical activities were the predominant sources of pollution during the last 600 years.

Development of Lead-210 Measurement in Peat Using Polonium Extraction. A Procedural Comparison Two chemical treatments for lead-210 measurement were compared on the sub-surface samples of a core from an ombrotrophic bog from East Belgium. The classical procedure involves a concentrated acid extraction of polonium. However, this treatment represents substantial health risks together with unknowns regarding both the degree of cleanliness and the Po extraction rate, and most importantly, is rather time consuming. We developed here an improved procedure involving an ashing step prior to acid extraction. This allows substantial improvements such as: 1/ the use of a relatively small amount of acid compared to the classical procedure and 2/ the substantial reduction of a total sample digestion time. Measurements of 210Pb concentrations were conducted by alpha spectrometry. Results show a good agreement of unsupported 210Pb activity obtained for both procedures, although some unknowns remain concerning the adsorption of 210Po on the plastic test tube, the volatilization of a small amount of ash, or the absorption of alpha particle at the alpha source surface. This however should not affect the 210Pb measurement as all the samples are spiked prior to ashing (i.e. the recoveries are fully monitored). Through this study, we are suggesting researchers to follow this new procedure in order to increase safety, cleanliness, better recovery and substantial time gain.

Radiocarbon and 210Pb were measured on the uppermost 40 cm of a Wardenaar peat core retrieved from a Baltic raised bog at Słowińskie Błota (Pomerania, North Poland). This site is the subject of ongoing multiproxy studies covering the last 1300 years. Radiocarbon age model was constructed on the basis of 14 AMS dates obtained on selected Sphagnum spp. fragments, with use of P_Sequence tool. We present here a comparison of this model with the age model obtained using CRS model classically applied to 210Pb measurements.

International audience; Lead pollution history over Northern Poland was reconstructed for the last ca. 1300 years using the elemental and Pb isotope geochemistry of a dated Polish peat bog. The data show that Polish Pb-Zn ores and coal were the main sources of Pb, other heavy metals and S over Northern Poland up until the industrial revolution. After review of the potential mobility of each element, most of the historical interpretation was based on Pb and Pb isotopes, the other chemical elements (Zn, Cu, Ni, S) being considered secondary indicators of pollution. During the last century, leaded gasoline also contributed to anthropogenic Pb pollution over Poland. Coal and Pb-Zn ores, however, remained important sources of pollution in Eastern European countries during the last 50 years, as demonstrated by a high 206Pb/207Pb ratio (1.153) relative to that of Western Europe (ca. 1.10). The Pb data for the last century were also in good agreement with modelled Pb inventories over Poland and the Baltic region.

International audience; 'Little Ice Age' (LIA) climatic deteriorations have been abundantly documented in various archives such as ice, lake sediments and peat bog deposits. Palaeoecological analyses of peat samples have identified these climatic deteriorations using a range of techniques, for example palynology, plant macrofossils, testate amoebae or carbon isotopic analyses. The use of inorganic geochemistry and the reconstruction of dust fluxes has remained a challenge in tracing the nature of LIA climatic changes. Although the idea of enhanced erosion conditions and storminess is commonly discussed, the conditions for dust deposition in peatlands over Europe during the LIAare rarely favourable, because the natural forest cover over Europe was much more important than nowadays, preventing dust deposition. This intense forest canopy masks the deposition of dust in peatlands. In northern Poland, near the Baltic shore, the Słowin'skie Błota area was deforested around AD 1100, ie, just before the LIA, and therefore constitutes a key area for the reconstruction of LIA climatic change. With the support of a well-constrained chronology, climatic fluctuations are recorded in an ombrotrophic bog using inorganic geochemistry, plant macrofossils and carbon isotopic analyses. The reconstruction of LIA climatic changes is in good agreement with other records from Poland and NE Europe. However, a c. 50-year discrepancy can be observed between various records. This discrepancy is possibly due to progressive time-dependent cooling gradient from north to south Europe.