A High–Resolution Accumulation Record of Arsenic and Mercury after the First Industrial Revolution from a Peatland in Zoige, Qinghai–Tibet Plateau

The impacts of human activities on Zoige peatlands are poorly documented. We determined the concentrations and accumulation rates of As and Hg in a 210Pb-dated peat profile collected from this area and analyzed the correlations between accumulation rates of both As and Hg and other physicochemical properties. To reconstruct recent conditions of As and Hg, we analyzed peat sediments of Re’er Dam peatland in Zoige using 210Pb and 137Cs dating technologies. The concentrations of total As (86.38 to 174.21μg kg−1) and Hg (7.30 to 32.13 μg kg−1) in the peat profile clearly increased after the first industrial revolution. From AD 1824 to AD 2010, the average accumulation rates were 129.77 μg m−2 yr−1 for As and 18.24 μg m−2 yr−1 for Hg. Based on our results, anthropogenic emissions significantly affected the atmospheric fluxes of As and Hg throughout the past 200 years, and As was also likely to be affected by other factors than atmospheric deposition, which needs further identification by future studies. The historical variations in As and Hg concentrations in Re’er Dam peatland in Zoige mirror the industrial development of China.

Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging when the glacier is experiencing mass loss in the accumulation zone as result of climate warming, leading to an older ice surface of unknown age. In this context, we dated a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier in the locality Pian di Neve (3100 m a.s.l.). Here we present a timescale for the core obtained by integrating results from the analyses of the radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. For the period of 1995–2016 the mass balance at the drilling site (former accumulation zone) decreased on average of about 1 m w.e. a−1 compared to the period 1963–1986. Despite the severe mass loss affecting this glacier even in the former accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier using black carbon and pollen seasonality in combination with radionuclides 210Pb and 137Cs. Our results are therefore very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives.

Geochronological implications of 210Pb and 137Cs mobility in cave guano deposits

Some recent publications on the paleo- and historical environmental interpretation of bat guano sequences have relied on 210Pb and 137Cs distribution to establish age-depth models, even when these are at odds with radiocarbon models in the lower parts of the sequence. Here, we present both field and laboratory evidence for the unpredictable mobility of lead and cesium in decomposing bat guano deposits. We suggest that 210Pb- and 137Cs-based chronologies of bat guano deposits should only be used when independently supported, for example, by a robust radiocarbon age-depth model.

Radioactivity content surveillance on canned food products in Nigeria

The radionuclides surveillance on imported can food products in Nigeria market has been investigated using High purity Germanium detector. The radioactivity concentrations of 226Ra, 232Th, 40K, 210Pb and 137Cs in selected brands of imported canned food products categorized into staple foodstuffs, beef and seafood were analyzed. The results obtained for staple foodstuffs shows a mean activity value of 12.33±3.68, 12.35±4.62, 51.48±15.12, 2.65±0.18 and 0.61±0.27 Bq kg-1 for 226Ra, 232Th, 40K, 210Pb and 137Cs respectively, while in beef food products, it is 14.41±4.79, 14.12±4.83, 50.44±14.80, 1.11± 0.07 and 0.32±0.20 Bq kg-1 respectively, and for seafood products it is 17.95±5.71, 16.24±5.48, 61.65±18.07, 1.17±0.13 and ND Bq kg-1 respectively. The overall results indicate that the natural radioactivity in the three categories of canned foodstuffs examined are well below the UNSCEAR and other regulatory bodies recommended permissible limits. The presence of 137Cs in some samples potent some degree of heavy metal contamination of those foodstuffs. The computed dose to essential organs and tissues indicates a highest dose level of 0.2 mSvy-1 which is well within the 1mSvy-1 recommended permissible level of the public. The calculated collective effective dose equivalent revealed that 97,463,16 of the total population are exposed to radiation from ingestion of the canned foods with adults most impacted. The total health detriment indicates radiological risk ratio of 1:2238 for infants, 1:2583 for children and 1:4238 for adults. From the estimated costdetriment, it is obvious that the economic benefits which is directly proportional to cost of purchase and importation put at about nine billion US dollars annually derived from consuming these imported canned food products is far above the health detriment. Keywords: Radioactivity surveillance, canned food, health detriment, Nigeria

Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging when dating glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we dated a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier in the locality Pian di Neve (3100 m a.s.l.). Here we present a timescale for the core obtained by integrating results from the analyses of the radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. Despite the severe mass loss affecting this glacier even in the accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier. Our results are therefore very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives.

Combination of 137Cs and 210Pb Radioactive Atmospheric Fallouts to Estimate Soil Erosion for the Same Time Scale

Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210Pb and 137Cs fallouts for the same time scale by relaxing the constraint on 210Pb fallout from being used for 100 years’ time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is important to note that the proposed model has two main advantages. First, the complementarity between 210Pb and 137Cs fallouts is for the same time scale and not for different time scales, as usually considered and believed in this field. Second, 210Pb fallout is used for time scales less than 100 years. This makes the model useful to estimate soil erosion rates for two successive periods of cultivation. To the best knowledge of the authors, the combination of 210Pb and 137Cs fallouts for the determination of soil erosion rate variation due to change in cultivation practices for the same time scale has never been developed or applied in the past.

Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Chatyr Kol lake (Kyrgyz Republic)

Microfacies analysis of a sediment record from Chatyr Kol lake (Kyrgyz Republic) reveals the presence of seasonal laminae (varves) from the sediment base dated at 11 619±603 BP (years Before Present) up to ∼360±40 BP. The Chatvd19 floating varve chronology relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ±5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs gamma spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed maximum uncertainty of 10 %. Six varve types were distinguished, are described in detail, and show a changing predominance of clastic-organic, clastic-calcitic or clastic-aragonitic, calcitic-clastic, organic-clastic, and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to (1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to (2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains, and Ruppia maritima seeds reveals reservoir ages with a clear decreasing trend up core from ∼6150 years in the early Holocene, to ∼3000 years in the mid-Holocene, to ∼1000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Lake Chatyr Kol (Kyrgyz Republic)

A finely laminated lake sediment record with a basal age of 11,619 ± 603 years BP was retrieved from Lake Chatyr Kol (Kyrgyz Republic). Microfacies analysis reveals the presence of seasonal laminae (varves) from the sediment basis to ~ 360 ± 40 years BP. The Chatvd19 floating varve chronology covers the time span from 360 ± 40 years BP to the base and relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ± 5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs γ-spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed uncertainty of 10 %. Six varve types were distinguished, are described in detail and show a changing predominance of clastic-organic, clastic-calcitic or -aragonitic, calcitic-clastic, organic-clastic and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to 1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to 2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains and Ruppia maritima seeds reveal reservoir ages with a clear decreasing trend up core from ~ 6,150 years in the early Holocene, to ~ 3,000 years in the mid-Holocene, to ~ 1,000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.