Dose Recovery Tests Research Articles

Thermal stability of the bleachable and unbleachable components of the ESR signals in sedimentary quartz

The thermal stability of the bleachable and unbleachable components of the electron spin resonance signals in quartz grains from modern fluvial sediments were investigated. It was found that the unbleachable Al center is thermally more stable than the bleachable component, hence the unbleachable component can be extracted by heating. Protocols for equivalent dose evaluation with preheating are proposed, in which the procedure of bleaching is replaced by “partial annealing” (heating at 280 °C for 15 minutes) for the Al center and by “annealing” (heating at 400 °C for 1 hour) for the Ti-Li and Ti-H centers. The dose recovery test confirmed that the proposed protocol works practically, and that the regenerative protocol is better than the additive dose protocol in the aspect of the statistical errors. Appropriate partial annealing conditions to extract the unbleachable Al centers may need to be investigated for each sample.

Investigating luminescence signals of pharmaceuticals and dietary supplements for emergency dosimetry

This study investigates the potential use of dietary supplements and pharmaceuticals containing magnesium, calcium or potassium for emergency dosimetry applications using the phenomenon of optically stimulated luminescence (OSL). Signal measurements were carried out using different stimulation wavelengths, and blue light stimulation was found to be the most efficient. More than half of the samples exhibited a measurable OSL signal and relatively high radiation sensitivity compared to other previously measured emergency detectors. Moreover, samples generally demonstrated a linear dose response. Possible causes of their high zero-dose signal were investigated: mechanical processing and UV light excitation. As variability in sensitivity was observed, the test-dose protocol was used during measurements. Furthermore, the study showed a significant loss of OSL signal intensity within 24 h after irradiation, which suggests the necessity for a fading correction. Finally, a dose recovery test was performed to evaluate the materials and the test-dose protocol under realistic conditions. The findings indicate the potential for using pharmaceuticals and dietary supplements in the event of a radiation emergency due to their dosimetric properties and ease of obtaining.

Single grain pIRIR dating of glacigenic deposits in the Yuzhu Peak area of Kunlun Mountains of Tibetan Plateau revealed the glaciations during Holocene period

The variations of glaciers in the Kunlun Mountains of the northern Tibetan Plateau are influenced by the complex interaction of the East Asia summer monsoon (EASM), Indian summer monsoon (ISM) and Westerlies, as well as human activity during the Holocene period. Consequently there is ongoing debates regarding the evolution of glaciers and the factors driving their changes. The reconstruction of glacial evolutions in these regions has been hindered by insufficient chronological data for moraines and other glacial landforms. In this study, glacial sediment samples were collected from five moraine sequences located on the southern and northern slopes of the Yuzhu Peak in the Kunlun Mountains. These poorly bleached moraine samples were dated using the single-grain quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating methods. The luminescence characteristics analysis of quartz grains shows that single grain quartz OSL dating cannot be used to date Holocene moraine samples due to the low brightness of quartz OSL signals. Various tests were conducted to assess the reliability of K-feldspar pIR50IR170 dating, including anomalous fading tests, dose recovery, and residual dose tests. The K-feldspar pIR50IR170 ages, determined using the Minimum Age Model (MAM), indicate that during the early Holocene, glaciations have expanded by ∼800 m in length at ∼ 8 ka, and during the end of the Neoglacial period, they extended by ∼200 m in length at ∼ 1 ka. The strengthened ISM precipitation and northward movement of ISM boundary likely contributed to the glacial expansion in the early Holocene. During the end of the Neoglacial period, the increase in westerlies precipitation and cold events may have played a role in the advancement of glaciers.

Testing the applicability of standardised growth curves for chemically heterogeneous single-grain feldspars from the Atacama Desert, Chile

The Atacama Desert is generally considered the driest non-polar desert on Earth and is therefore an ideal study area for exploring the water and biota free endmember of Earth's Critical Zone (ECZ). Single grain (SG) luminescence dating has successfully identified processes in the ECZ. However, SG luminescence dating of Atacama Desert feldspars is challenging and time consuming since only a small fraction of grains emits sufficient luminescence and their potassium (K) contents, needed for internal dose rate calculations, are highly variable. Here we present an adaption of the standardised growth curve (SGC) method adjusted to the conditions of Atacama Desert sediments and a correlation of single-grain geochemistry and luminescence properties.To evaluate if SGCs are suitable for our study site and to determine the influence of the K-content on our luminescence age calculations, we used a set of five samples from the Atacama Desert and five chemically and structurally different feldspar sediment extracts from various geological origins worldwide. We performed a dose recovery test (DRT) using a post-infrared infrared stimulated luminescence (pIRIR) protocol and measured nine major element concentrations, including K, on a single grain level using a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX). The DRT dataset was then used to test the application of SGCs. The accuracy of Atacama feldspar pIRIR measurements fitted onto SGCs frequently suffers from odd values in single measurement cycles, since the SGC approach developed for SG feldspar luminescence (Li et al., 2015b) uses one Lx/Tx measurement to project the Ln/Tn values onto a SGC. We investigate the influence of calculating a synthetic regenerative signal (sR) for SGC fitting, to reduce the effect of those odd values on individual grain measurements. Furthermore, we reduced the regenerative cycles used for our sR approach, to test if shorter protocols would result in equivalent dose (De) estimates in agreement with longer protocols. We then calculated Spearman rank correlations between the results obtained with our modified SGC and the SAR protocol, luminescence signal intensities, and the geochemical dataset.Finally, we present a new method of fitting data onto a SGC which significantly decreases measurement time, without risking the inclusion of outliers. We furthermore show that the luminescence signal intensities, the De values and their dose recovery ratios obtained with our SGC method and a SAR protocol, are independent of the sample geochemistry.

Holocene lake shrinkage on the northwestern Tibetan Plateau revealed by K-feldspar single-grain pIRIR dating of paleo-shorelines

As a vital component of the “Asian water tower”, lakes on the Tibetan Plateau (TP) significantly influence the regional ecosystems and economies and they are also an effective sentinel of climate change. However, the temporal and spatial patterns of lakes and the related hydroclimatic evolution on the northwestern TP (NWTP) remain unclear. We reconstructed the lake level variations of a non-glacier-fed lake, Longjue Co, on the NWTP, using optical dating of paleo-shorelines. The optically stimulated luminescence signals of quartz grains were unsuitable for dating due to high contributions of the medium component, and thus the post-infrared infrared stimulated luminescence signals (pIR50IR170, pIR50IR225) of K-feldspar single grains were used. Internal checks including dose recovery tests, residual dose tests, and anomalous fading tests showed that the pIR50IR170 signal was suitable for paleo-shoreline dating in Longjue Co. However, some of the samples were affected by the incomplete bleaching of pIRIR signals before deposition, and in this case the Minimum Age Model was used to constrain the ages. We also examined the dependence of the K-feldspar equivalent dose (De) on grain brightness and explored the possible mechanisms, and the brightest grains were then used for De calculations. The results show that Longjue Co reached its maximum Holocene level (+34 m) during the early Holocene (10.06 ± 1.39 ka), and then after ∼5 ka it commenced a shrinking trend, punctuated by two rapid lake level decreases. Reference to independent paleoclimate records suggests that the Holocene lake level variations of Longjue Co and the regional hydroclimate were mainly controlled by the Indian summer monsoon.

The post-IR IRSL dating of an ancient dammed lake upstream of the Ganglai gorge in the upper-middle reaches of Yarlung Tsangpo

The middle reaches of Yarlung Tsangpo, situated on the southern Tibetan Plateau, have experienced extensive river damming events due to glacier advances, resulting in the formation of several ancient dammed lakes. These palaeolakes offer invaluable insights into past hydrological and geomorphological dynamics on the Tibetan Plateau. In this study, we reported a newly identified ancient dammed lake, named the Xiaru palaeolake, located upstream of the Ganglai Gorge in the uppermost segment of the middle reaches of Yarlung Tsangpo, and conducted a pioneer chronological investigation of the lake using K-feldspar post-IR IRSL (pIRIR) dating. Quartz minerals from most lacustrine and fluvial sediments can not provide reliable ages characterized with low intensity and large inter-aliquot scatter in equivalent doses (De). In contrast, the K-feldspar exhibited much greater luminescence intensity and narrower De distribution using the pIRIR225 dating protocol. Residual, dose recovery, and fading tests demonstrated that the pIRIR225 signals are well bleached with a relatively low fading rate, making it a more suitable dosimeter for dating applications in the study area. The pIRIR225 ages, derived through single aliquots, standard growth curve (SGC), and single grain measurements, reveal a major phase of the Xiaru Lake between 24.1 ± 1.0 ka and 15.8 ± 1.1 ka, that commenced aligning with the global Last Glacial Maximum. Furthermore, one lacustrine sample dated to 29.9 ± 2.2 ka suggests the possibility of multiple damming events in Ganglai Gorge during the last glacial period, although further evidence is required for a comprehensive interpretation.

OSL signal of electronic components from portable radios for radiation accident dosimetry

The portable radio (hand-held device) is the preferred means of communication for the first responders from the homeland security forces and is systematically carried during intervention. This electronic device could therefore be a good candidate as a possible fortuitous dosimeter to estimate the dose received by the members of these security forces in the event of a radiological accident. For this purpose, the dosimetric properties of electronic components extracted from the circuit board of portable radios used by a French specialised intervention unit were investigated using the OSL technique. The dosimetric properties of such electronic components were compared to those of resistors extracted from mobile phones to determine whether an OSL protocol developed for mobile phone resistors could be applied also to these electronic components. The OSL dosimetric properties were generally similar and the results of a dose recovery test using these components removed from a portable radio were in good agreement with the nominal dose. Further experiments showed the importance of knowing the storage temperature conditions of these devices to accurately estimate the dose in case of a radiological accident.

Thermoluminescence dating of gypsum in loess deposits

Gypsum deposits within loess deposits are an important indicator of weathering processes and climate change. We conducted a thermoluminescence (TL) dating study of the gypsum from loess deposits of the Jiuzhoutai section in the western Chinese Loess Plateau. Determination of the equivalent doses (De) of gypsum samples was conducted using several protocols, including single-aliquot regenerative-dose (SAR-TL), multiple-aliquot additive dose (MAAD-TL), and Isothermal TL of SAR (SAR-ITL). The TL glow peak at 280 °C was targeted because of its reported stable signals. The test dose check, estimation of sensitivity changes, and the dose recovery test were applied to assess the applicability of the different protocols, and the characteristics of the thermoluminescence signals for gypsum were evaluated. The De results for the SAR-TL, MAAD-TL, and SAR-ITL protocols were within the error ranges. Among the three protocols, SAR-ITL did not involve high-temperature heating and it provided a more accurate De value, and thus it was used for De determinations for gypsum dating. With a dose rate of 1.74 ± 0.07 Gy/ka, the minimum TL age of the gypsum veins was ∼182 ± 7 ka. U-series dating was also applied to the same samples for comparison. However, the extremely low ratio of 230Th/232Th (≤4 × 10−6) of the gypsum veins deposited within the loess resulted in a large error of the U-series dates. We conclude that TL dating is more appropriate for the dating of gypsum in loess deposits.

Development of a prototype TL/OSL reader for on-site use in a large-scale radiological accident

This study presents the development and characterization of a prototype TL/OSL reader for the retrospective dose assessment of individuals in radiological emergencies. The reader is portable, semi-automatic, and capable of accurate measurements. The dimension of the reader is 25×25×37 cm3 and the weight is about 15 kg. The reader consists of a sample moving stage, a heating module, an optical stimulation module, a detection module, a data acquisition (DAQ) unit, a nitrogen gas control module, and a PC with a GUI program. The reader has three measurement modes: TL, CW_OSL, and custom mode. The reader was characterized using commercial thermal luminescence dosimeters (TLD, LiF:Mg,Cu,Si) and optically stimulated dosimeters (OSLD, Al2O3:C), as well as fortuitous materials, such as display glasses and resistors of mobile phone. The results showed that the reader is capable of measuring signals with a detection limit of up to 0.02 mGy using a commercial dosimeter. In the dose recovery test using fortuitous materials, the reconstructed doses obtained three days post-irradiation closely aligned with the initially administered doses. As a result, this study suggests that the developed TL/OSL reader is a promising instrument for emergency dose assessment at accident sites.

OSL at elevated temperature of smart chip cards for retrospective dosimetry

Smart chip cards are a promising material in retrospective dosimetry due to their high collectability with low replacement cost. In this study, dose reconstruction using OSL at elevated temperatures for various chip cards was investigated. The approximate spectral emission of the chip cards was determined through a comparison of radiation-induced and intrinsic background TL signals using different detection filters. In the OSL decay curve, a fast component (0.0–0.4 s) was integrated to avoid high intrinsic background signals. To minimize sensitivity changes due to heat treatment, a protocol to measure OSL at 100 °C was developed and the data were compared with those from a similar protocol for OSL measured at room temperature. In the 0.1 - 5 Gy range, linear and power functions were fitted for room temperature and 100 °C OSL protocols, respectively. The minimum detectable dose was evaluated immediately after exposure, with values of 25 mGy for room temperature and 240 mGy for 100 °C OSL being determined. Signal fading was measured up to 30 days after irradiation for the investigated protocols. A dose recovery test was made 10 days after irradiation using various chip cards, and the 100 °C OSL protocol produced more reliable results than the room temperature OSL protocol. As a result, the study emphasizes the necessity of further investigation of OSL at high temperatures using chip cards.

Testing infrared radiofluorescence dating on polymineral fine-grains from the Luochuan loess-palaeosol sequence, Chinese loess plateau

In the past infrared radiofluorescence (IR-RF) dating has been focused on coarse-grain potassium feldspar (K-feldspar). However, polymineral fine-grains (4–11 μm) have proven to be successful dosimeters when dating using conventional infrared stimulated luminescence (IRSL). In this study, we investigated the potential of IR-RF signals generated from polymineral fine-grains for dating on 6 loess samples (∼30–480 ka) from the well documented Luochuan loess-palaeosol sequence on the Chinese Loess Plateau. Both the natural and regenerated IR-RF signals from the polymineral fine-grains were uncharacteristically flat with little or no dynamic range using either a bleaching duration of 1500 s or 20000 s between the measurements. X-ray fluorescence (XRF) analyses showed that the polymineral fine-grains were dominated by quartz and Na-feldspars. K-feldspar and Na-feldspar mid-grain (38–63 μm) sample sets were further prepared, measured and compared. The IR-RF signals from the K-feldspar mid-grains exhibited the characteristic exponentially decaying signal, while the IR-RF signals from the Na-feldspar mid-grains were flat with little dynamic range, indicating that the Na-feldspar dominates the polymineral fine-grain IR-RF signal. The polymineral fine-grain ages (both bleaching settings) were consistent with reference ages up to 300 ka (∼1000 Gy), however, due to the flat nature of the curves the uncertainties were large. The consistency of the results using the two bleaching durations indicates that the bleaching duration has a less significant role in the IR-RF dating with polymineral fine-grains than in the coarse grains. Of the mid-grain ages, the IR-RF ages of Na-feldspar mid-grains were consistent with the reference ages up to 360 ka (∼1200 Gy) while those of the K-feldspar mid-grains were consistent with the reference ages up to 200 ka (∼600 Gy). Dose recovery tests were undertaken on all samples, however, where the dose recovery ratios were considered the most successful (K-feldspar mid-grains) the dating results were the least successful, suggesting that dose recovery tests in this way may be a less useful predictor of the dating performance of the IR-RF dating. IR-RF dating of polymineral fine-grains was possible up to 300 ka for Chinese loess, despite the uncharacteristically flat signals.

Towards the optically stimulated luminescence dating of unheated flint

Flint tools are important archaeological finds, but unheated specimens remain challenging to date. The optical luminescence properties of the microcrystalline flint differ from sedimentary quartz grains, and optically stimulated luminescence (OSL) has, therefore, only occasionally been used to date heated flint specimens. However, if OSL dating could be used on unheated samples, this should expand the number of dateable flint samples from the archaeological record. This study investigates the luminescence sensitivity to blue, green, and infrared stimulation in flints collected from four sites in eastern Denmark. While stimulations at each wavelength yielded some luminescence emissions, blue OSL provided the strongest emission, and subsequent investigations here focus on measurements using this signal. The shape of the decay curves and the photo-ionising cross-sections for the blue OSL signal components are similar between natural and irradiated OSL and are also comparable to decay curves from calibration quartz. Dose–response curves show characteristic doses of ∽400 Gy, and dose recovery tests demonstrate that a SAR protocol can recover laboratory doses. The measured laboratory fading rates are considerable, where flint slices stored for up to six weeks provide average g-values of up to 9 % per decade. Also, the flint is less thermally stable compared to calibration quartz. However, a natural OSL signal remains in Cretaceous flints (albeit at 50 % or less of laboratory saturation), showing that signal loss did not outpace the electron trapping rate. The presence of a dose-dependent, natural OSL signal and acceptable dose recovery indicate that optical dating of flint surfaces could be feasible, at least in the flints from eastern Denmark, and that flint from other regions should be investigated.

Feasibility study of using earbuds and wireless headphones for retrospective dosimetry

Luminescence dosimetry could be an essential tool in retrospective dosimetry for assessing an absorbed dose after a radiological overexposure. Mobile phone components could be useful proxies for measuring the amount of dose an individual has received. Different research groups have extensive experience in characterising different elements of mobile phones (i.e. electronic components, display or touch screen glass) for physical retrospective dosimetry. However, so far these techniques are frequently destructive and alternative materials need to be sought for further research on cheaper electronic devices.Earbuds and wireless headphones have become quite popular and are often carried closely to the body or may be found in personal bags. These low-budget electronic devices might potentially be better accepted by the general population compared to high-price objects, such as an expensive smartphone.On the circuit boards of these items, electronic components (SMDs) were found. The results of a dose recovery test after x-ray irradiation using a standardized luminescence measurement protocol developed for resistors extracted from mobile phones are presented. The estimated doses from the sampled SMDs were overestimated by a factor up to 2.1 following this initial experiment. Further investigations showed that the signal stability of some SMDs was significantly different from that of mobile phone resistors. The use of a fading correction specific to these SMDs improved the dose reconstruction results. Generally, these low-budget electronic devices are potentially suitable for dose assessment and an alternative fortuitous retrospective dosimeter.

Detection of baby food sterilized with ionizing radiation using thermoluminescence

AbstractFood sterilization with ionizing radiation is a well-established technology, which is constantly extending to several products due to its numerous advantages. However, radiosterilization is prohibited to several food categories, such as baby food products since it could cause nutrient degradation of such foods with significant effects on the infants’ health. As a result, any governmental agency responsible for the detection of irradiated products should first focus on products consumed by babies/children. To this respect, the present work explores whether TL can be employed as a method for post-sterilization dosimetry on baby food, by studying the properties of their glass containers since they would be equally and jointly exposed to the ionizing radiation during the sterilization process. Two different reputable brands, i.e., Hipp® and Nestle®, are used for this purpose. Both glass containers exhibit a linear TL dose response for doses up to 3 kGy, while no sensitization of the main peaks is observed. Though their behavior is not very stable with time (strong fading) yet fading correction is possible. Dose recovery tests were successfully conducted, calculating the administered dose with high accuracy. A computerized curve deconvolution analysis (CCDA) was also performed revealing that all glow curves can be fitted with one peak of continuous trap distribution and three discrete-energy peaks, which also demonstrate a linear dose response over the range 50–3000 Gy. Thus, findings are very promising towards the post-sterilization dosimetry of baby food through their glass containers.

Thermoluminescence characterization and kinetic parameters of eyeglass lenses for applications in retrospective/accidental dosimetry

Many researchers study the luminescence properties of objects consisting of glass, aiming to applications for retrospective/accidental dosimetry. In this context, eyeglass lenses are used globally and be worn by large portion of the population. In a case of an accident with radiation release, they can be recovered to assess the exposure dose of the general population in the vicinity of the accident.The scope of the present study is to conduct, for the first time, a detailed study of the thermoluminescence properties of eyeglass lenses along with computerized curve deconvolution analysis which would shed light on the kinetics involved to explore their suitability as dosimeters. The dose range under study is between 0.1 and 16 Gy.Results, which appear independent of the chemical composition of the lenses, indicate that the glow curves of the eyeglass lenses have overlapping peaks, while an inherent signal (zero-dose) may also appear, probably produced during the manufacturing process. The materials do not exhibit sensitization effects, and they present linear dose response for doses up to 16 Gy. A dose recovery test predicts with high accuracy an “unknown” delivered dose. The remaining signal after one-month post-irradiation is sufficient for conducting post-radiation measurements.A computerized curve deconvolution analysis (CCDA) indicates the co-existence of at least two discrete-energy traps and one continuous-distribution trap. After the TL deconvolution of the glow curves, for all doses and all eyeglass lenses, the kinetic parameters were determined for all the components.A preliminary study is also conducted towards the elimination of the unwanted inherent signal. Hydrofluoric acid presents the most promising treatment method, among two chemical methods that were applied in the present work.The results of the current study enhance the potential use of the eyeglass lenses as dosimetric probes in the case of an accident that involves radiation release and exposure of the general population.

Luminescence studies in touch screen protective glass of mobile phones for its possible application as retrospective dosimeter

Thermoluminescence (TL) properties of display glass from three mobile phone brands were investigated for its application as a dosimeter in accident situation. The glow curves show TL peak between 520 and 550 K and have broad emission spectrum from 300 to 650 nm with a maximum at about 460 nm and a minor shoulder at about 590 nm. Thermal quenching studies of all three display glasses show that there is no thermal quenching. Fading studies show that the decay of the signal is purely thermal in nature and the rate of fading is different from that reported in the literature. A suitable protocol in order to minimise the effect of fading and the inherent background signal was used for dose recovery. Dose recovery tests carried out show that the glass can be used from a few mGy up to the studied dose of 5 Gy.

Thermoluminescence characterization of minerals extracted from dried oregano for retrospective and/or sterilization dosimetry

Silicate minerals extracted by dried herbs are broadly used for the determination of food products that are sterilized by means of radiation. At the same time, it is necessary to calculate the applied sterilization dose for these products, since there are certain pre-defined dose limits for the variant food categories.In addition, researchers seek for materials that can be used in retrospective/accidental dosimetry, in the cases that there is no available data from personal dosimeters. In this perspective, dried oregano is used worldwide and is a popular herb for most households.The purpose of this study is twofold; the evaluation of the extracted minerals for the assessment of the post-sterilization dose and the estimation of the accidental dose that certain population might have been exposed to. In order to succeed this purpose, a thorough characterization of the thermoluminescence (TL) properties of the silicate minerals was conducted. Two dose ranges were studied, for the two different applications mentioned above, namely a range between 0.050 and 4 kGy and a range between 1 and 20 Gy. ResultsData reveal that the glow curve of the silicate minerals has at least three overlapping peaks in the dosimetric spectrum. The material exhibits strong sensitization effects, which can be suppressed by including a sensitization correction within the applied protocols. All three peaks demonstrate linear dose response for doses up to 20 Gy, while for the range of 0.050 Gy–4 kGy a saturation curve is used for the fitting.An unknown delivered dose is successfully estimated by a dose recovery test, when the applied dose belongs to the lower dose range. The stability of the signal with respect to the storage time differs for the three peaks and the remaining signal is appreciable for 1 month post irradiation.Finally, a Computerized Curve Deconvolution Analysis (CCDA) was conducted, based on the equations of the general order kinetics. The TL glow curves of all doses were successfully deconvoluted using eight discrete-energy curves and the corresponding kinetic parameters were also calculated.The findings of the present study support the potential use of the silicate minerals, extracted by dried oregano for accidental/retrospective dosimetric applications.

Optically stimulated luminescence properties of commercially available KCL dietary supplements as retrospective dosimeters.

In the case of an unexpected exposure to radiation in places where there is no access to standard dosimeters, materials that can act as detectors in methods of retrospective dosimetry are looked for. Such materials include, but are not limited to, medicines and dietary supplements that are found in households or in personal bags. This article presents the optically stimulated luminescence (OSL) dosimetric properties of dietary supplements, the main ingredient of which is a sensitive phosphor - potassium chloride (KCl). Three types of KCl dietary supplements were tested and compared to a selection of four common drugs in terms of their sensitivity. Basic dosimetric properties of dietary supplements such as signal repeatability, dose response and fading were determined. The dose recovery test was performed 2 and 7 days after exposure to radiation. The obtained dose values for the two supplements showed good compliance with the nominal dose values and the possibility of correctly assigning the doses to the levels of triage (low dose 0-1Gy, medium dose 1-2Gy and high dose > 2Gy). The presented results show that dietary supplements with KCl have the potential to be used as emergency detectors in the dose recovery process.

Age comparison by luminescence using quartz and feldspar on core HPQK01 from the Pearl River delta in China

Reliable chronology is critical for reconstructing estuarine delta process. In this study, detailed chronological framework has been performed on a core HPQK01 (52 m in depth) from the central Pearl River delta (PRD) of China. Both quartz OSL and feldspar post-IR IRSL (pIRIR) methods for late Pleistocene sediments, as well as radiocarbon dating for Holocene sediments, were applied to date the core. Results show that quartz OSL ages range from 125 ± 18 ka to 58 ± 6 ka, and that all of them were minimum ages due to the OSL signal saturation. Feldspar pIR 200 IR 290 protocol shows some overestimation in dose recovery test, with the recovered to the given ratio of 1.2, while a ratio of around 1 was obtained for feldspar pIR 50 IR 250 signals. Robust ages have been obtained from feldspar fading corrected pIR 50 IR 250 dating with ages ranging from 150 ± 17 ka to 98 ± 12 ka. AMS 14 C results suggest that subtidal-intertidal zone was deposited during the middle Holocene from 8.21 ± 0.19 cal ka BP to 4.99 ± 0.25 cal ka BP. The sedimentology of core HPQK01 record two marine transgressive-regressive cycles. Based on the dating results, the lower fluvial sediment unit (T2) could be correlated to marine isotope stage (MIS) 6, and the lower marine unit (M2) was deposited during MIS 5. A sedimentary hiatus occurred with age range of from MIS 4 to MIS 2. Since middle Holocene, another marine stratum (M1) has been accumulated. Overall, our findings suggest that feldspar pIRIR dating method has the potential to establish the Quaternary chronostratigraphic framework of the PRD for samples with ages within 150 ka. • Quartz OSL and feldspar post-IRIR, as well as 14 C, were performed to date a core in the Pearl River delta. • Quartz OSL produced minimum ages due to signal saturation. • Feldspar corrected pIR 50 IR 250 is appropriate for dating. • The age of the lower fluvial layer (T2) was in MIS 6. • The age of lower marine layer (M2) was in MIS 5 instead of MIS 3 that previously reported.

Effects of the size of the test dose on the SAR protocol for quartz optically stimulated luminescence dating of loess in the eastern Tibetan Plateau

Dating of quartz by optically stimulated luminescence (OSL) has been revolutionized with introduction of the test dose (TD) in development of a measurement sequence known as the single-aliquot regenerative-dose (SAR), whereby a valid sensitivity correction for the luminescence signal is provided in the measurement cycle. However, the size of the TD used in the SAR protocol remains controversial. Previous studies show that the TD has little effect on the equivalent dose (D e ) for young samples in luminescence dating in which the applicability of different deposits varies greatly in different regions. However, detailed studies are lacking on how TD size affects SAR–OSL results of samples with a relatively high D e range. In this study, typical loess samples with high D e values (∼60 Gy–∼250 Gy) from the eastern Tibetan Plateau were selected to investigate the effects of variation in TD size on the quartz SAR–OSL protocol. Dose recovery tests show that a known dose could be recovered successfully by applying different TDs. Test dose size has an effect on shapes of regenerated dose–response curves (DRCs) and has different influences on D e s and characteristic saturation doses for quartz samples with a high dose range. A TD size of 20%–30% D e is a good compromise for Tibetan loess with D e of ∼60–120 Gy in the quartz SAR protocol, and a TD size larger than 30% should be considered for samples with a larger D e . The results of this study highlight the importance of TD size in the SAR–OSL protocol for quartz samples with a high dose range. • Test dose size effect on the quartz SAR for high dose range is investigated. • Successful dose recovery test can be obtained by applying different test doses. • Test dose size has different influences on D e s and D 0 s. • A 20%–30% test dose size is a good compromise for D e of ∼60–120 Gy.