Radioactivity of some natural and artificial radionuclides in coastal seawater at Ninh Thuan, Ba Ria - Vung Tau and Ca Mau provinces in 2018

Radioactivities of some natural (Ra-226, Th-232, U-238, Po-210) and artificial (Cs-137, Sr-90 and Pu-239,240) radionuclides in coastal seawater at monitoring points of Ninh Thuan, Ba Ria - Vung Tau and Ca Mau provinces were analyzed quarterly in the year of 2018. Radioactivities of Ra-226, Th-232, U-238, and Cs-137 had been determined by simultaneous precipitation method and measured on low-level background gamma spectrometer; the radioactivities of Po-210 and Pu- 239,240 had been analyzed by radiochemical separation method and measured on alpha spectrometer; the radioactivity of Sr-90 had been analyzed by radiochemical separation method and measured on low-level background beta counting system. The ranges of radioactivities of Ra-226, Th-232, U-238, Po-210, Cs-137, Sr-90, and Pu-239,240 were 2.71 ÷ 15.91, 3.45 ÷ 35.93, 3.02 ÷ 21.47, 1.51÷ 6.74, 0.88 ÷ 1.68, 1.08 ÷ 1.86 and 0.0026 ÷ 0.0062 mBq/L, with the average values of 6.37, 12.67, 8.34, 3.29, 1.36, 1.46 and 0.0043 mBq/L, respectively. The results shown that the radioactivities of theabove-mentioned radionuclides varied between the seawaters at Ninh Thuan, Ba Ria - Vung Tau and Ca Mau seawater. Additionally, physicochemical parameters in seawater were also surveyed to assess their impact on the fluctuations of the above radionuclides.

Review of the analysis of 234Th in small volume (2–4 L) seawater samples: improvements and recommendations

The short-lived radionuclide 234Th is widely used to study particle scavenging and transport from the upper ocean to deeper waters. This manuscript optimizes, reviews and validates the collection, processing and analyses of total 234Th in seawater and suggests areas of further improvements. The standard 234Th protocol method consists of scavenging 234Th from seawater via a MnO2 precipitate, beta counting, and using chemical recoveries determined by adding 230Th. The revised protocol decreases sample volumes to 2 L, shortens wait times between steps, and simplifies the chemical recovery process, expanding the ability to more rapidly and safely apply the 234Th method.

Internal dose rate in quartz grains: Implications for luminescence dating

<div> <p>This study assesses how internal dose rate in quartz grains impacts luminescence dating.  In 2018, the Gliwice Luminescence Laboratory implemented innovative μDose system which combines advantages of alpha and beta counting measurement techniques with additional radioactive identification capabilities. The device allows measurements of small samples and results verification with an independent high-resolution gamma spectrometry method. </p> </div><div> <p>All measurements of internal dose rate were made on  pure quartz grains after standard chemical pretreatment. Grains with diameters between 125 and 200 μm were selected for measurements. This material was dried and grounded to approx. 20 μm using a planetary ball mill prior to measurements on the μDose systems.  </p> </div><div> <p>Internal dose rate reported here is particularly important because of low (about 0.8-0.9 Gy/ka) or very low (0.4-0.6 Gy/ka) external dose rates. Internal dose rate in quartz grains in our measurements is a significant fraction of the total dose rate, often exceeding 10%. Ignoring this correction would make luminescence ages in our study artificially older.</p> <p><span xml:lang="EN-US" data-contrast="auto"><span>Presented results were obtained with support of Polish National Science Centre, contract number 2018/30/E/ST10/00616</span></span><span> </span></p> </div>

THE ABRI CASSEROLE (DORDOGNE, FRANCE): REASSESSING THE 14C CHRONOLOGY OF A KEY UPPER PALEOLITHIC SEQUENCE IN SOUTHWESTERN FRANCE

ABSTRACTDiscovered at the beginning of the twentieth century, the Abri Casserole (Dordogne, France) was the subject of salvage excavations in the early nineties. The fieldwork revealed a sequence of 13 archaeological levels that document human occupations from the Gravettian to the Magdalenian, including very rare and poorly known assemblages (e.g. Early Badegoulian, Protosolutrean) that afford a particular importance to this sequence. Results of a previous dating program that focused on the Badegoulian levels were obtained in 1994 but were neither extensively published nor discussed. Five AMS 14C ages obtained for the Gravettian and Solutrean assemblages in the early 2010s served to complement the site’s chronology. However, since the beta counting ages for the Badegoulian levels were in conflict with the accepted AMS chronology for the region’s late Pleniglacial archaeological record, a new AMS dating program was implemented to renew the radiometric framework of this specific portion of the sequence. Compared to the previous beta counting measurements, the seven newly obtained AMS ages are about 1000 years older (23.3–20.5 cal ka BP) and congruent with other AMS-dated Badegoulian sequences. These results thereby restore the inter-site chronological coherence of the Solutrean–Badegoulian and Badegoulian–Magdalenian transitions.