Sulfate ions are commonly found in water, but excessive concentrations of these ions can have detrimental effects on the aquatic environment. In this study, reed straw was chosen as the raw material ...for producing biochar, which was then pyrolyzed with coal gangue to create environmentally friendly adsorption materials. This innovative approach aims to combat the issue of elevated SOsub.4 sup.2− concentrations in water while efficiently utilizing solid waste. The results showed that the adsorption process best fit the when the was pH 2 and the dosage was 8 g·Lsup.−1, and the adsorption capacity reached the maximum of 49.56 mg·gsup.−1. Via extensive characterization, kinetic studies, and isotherm experiments on the modified biochar, we determined that the mechanism of SOsub.4 sup.2− adsorption primarily involves electrostatic adsorption, physical adsorption, and chemical adsorption. The toxicology experiments showed that the activity of antioxidant enzymes and the amount of malondialdehyde decreased, and the content of chlorophyll and soluble protein increased. These findings suggest that modified biochar can mitigate the harmful effects of SOsub.4 sup.2− on reeds to a certain extent, ultimately promoting the growth of these plants.
The construction of the Iron Age Mediterranean chronology began in the Levant based on historical evidence and has been additionally supported in recent decades by means of radiocarbon analysis, ...although with variable precision and ratification. It is only in recent years that new evidence in the Aegean and the western Mediterranean has opened discussion towards its further acceptance as an authoritative i.e. highly reliable, and widely applicable historiographic network. Altogether, the Mediterranean Iron Age chronology has only undergone minor changes during the last hundred years. The Phoenician metropolis of Sidon in southern Lebanon now provides a new, large and robust dataset obtained through a combination of archaeological and .sup.14 C-radiometric analysis of materials from stratified contexts that allow their statistical assessment. The appearance of substantial amounts of pottery of Greek, Cypriot and Egyptian origin together with Phoenician local wares in a long stratigraphy is a benefit for the synchronisation of regional pottery styles and allows wider geographic correlation of relative chronological systems. The close association of the archaeological data with a long series of AMS-.sup.14 C-dates on short-lived samples provides new evidence for the absolute dating of many of the regional pottery styles that are represented in the stratigraphy of Sidon, and contributes towards a considerable improvement of the Mediterranean chronology.
Age validation of yellowfin Andrews, Allen H; Pacicco, Ashley; Airman, Robert ...
Canadian journal of fisheries and aquatic sciences,
04/2020, Letnik:
77, Številka:
4
Journal Article
Recenzirano
Estimates of age and growth of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna remain problematic because validation of growth zone deposition (opaque and translucent) has not been ...properly evaluated. Otolith growth structure (zone clarity) can be poorly defined for tropical tunas, but the use of bomb radiocarbon dating has validated age estimates to 16-18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period--defined by regional coral and otoliths--provided valid ages through ontogeny. Yellowfin tuna aged 2-18 years (n = 34,1029-1810 mm FL) and bigeye tuna aged 3-17 years (n = 12, 1280-1750 mm FL) led to birth years that were coincident with the bomb radiocarbon decline. The results indicate there was no age reading bias for yellowfin tuna and that age estimates of previous studies were likely underestimated for both species.
Estimates of age and growth of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna remain problematic because validation of growth zone deposition (opaque and translucent) has not been ...properly evaluated. Otolith growth structure (zone clarity) can be poorly defined for tropical tunas, but the use of bomb radiocarbon dating has validated age estimates to 16-18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period--defined by regional coral and otoliths--provided valid ages through ontogeny. Yellowfin tuna aged 2-18 years (n = 34,1029-1810 mm FL) and bigeye tuna aged 3-17 years (n = 12, 1280-1750 mm FL) led to birth years that were coincident with the bomb radiocarbon decline. The results indicate there was no age reading bias for yellowfin tuna and that age estimates of previous studies were likely underestimated for both species.
The megaliths of Senegal and The Gambia comprise nearly 30,000 erected stones recorded over a surface of around 30,000 km², mainly in the northern basin of the Gambia River. The very first ...radiocarbon date associated with the megaliths of Senegal and Gambia was published in 1965. Most of the radiocarbon dates obtained since then concern the westernmost part of Senegambian megalithism. More than 28 additional dates for the necropolis of Wanar (Senegal) alone, can now be added to the 25 previously available. Bayesian models incorporating the stratigraphic constraints specific to each sequence for each of the studied monuments, independently of each other, enable us to clarify these data and to propose an historic scenario. They illustrate a regional settlement sequence of more than two millennia, whereas the construction of standing stone circles could not have lasted for more than a few hundred years. Two radiocarbon dates on human teeth confirm that the death of the buried individuals dates from the eleventh or twelfth centuries AD.
Floodplains are dynamic ecosystems that cycle carbon, which is both delivered from upstream catchment sources and produced in-situ. These systems are being increasingly recognised as key environments ...of carbon processing, with the capacity for substantial carbon storage, in addition to acting as hotspots of carbon mineralisation. The balance of storage versus mineralisation is dependent on a number of controls including landscape position and environmental conditions. This study focuses on three headwater floodplains downstream of a highly eroded blanket bog peatland in the Peak District, UK. Previous research has shown that aged organic carbon from peatland sources, has been stored in floodplains in this area, and therefore, we aimed to understand whether allochthonous carbon was being mineralised in this context. We examined sediment cores and analysed the radiocarbon (14C) content of soil-respired CO2, using a partitioning approach to scrutinise the depth and age relations of respiration in the individual floodplains, and patterns of age distributions downstream. Aged organic carbon was released from the upper and mid floodplain sites (14C ages of 682 and 232 years BP, respectively), whereas only modern dates were recorded at the lower site. The geomorphic context and sedimentology supported these results, with the stratigraphy suggesting a dominance of allochthonous deposition at the upper sites, but primarily in-situ soil development at the lower site. There were no trends of radiocarbon age with depth in the individual floodplains, suggesting that floodplain sediments were well mixed and that aged organic matter was being processed both at the surface and at depth in the uppermost sites. An isotope mass balance mixing model indicated the dominance of two sources of CO2; recently fixed C3 organic matter (<10 years old) and CO2 produced by methanogenesis. The results indicate that floodplains in a relatively narrow halo around eroding headwater peatlands, could be important sites of aged carbon turnover originally derived from upstream sources. Reworked carbon does not transfer passively through the system and experiences periods of deposition where it can be subject to microbial action. This is an important consideration in other environments where organic carbon has previously been ‘locked up’ (e.g., permafrost regions) but is now under the threat of release due to climate change.
•Headwater floodplains as hotspots of old carbon turnover decline rapidly downstream.•Floodplains support microbial communities capable of respiring aged organic matter.•Lateral transfers from intact peatlands to floodplains lead to carbon emissions.
Investigating North Pacific climate variability during warm intervals prior to the Common Era can improve our understanding of the behavior of ocean-atmosphere teleconnections between low latitudes ...and the Arctic under future warming scenarios. However, most of the existing ice core records from the Alaskan and Yukon region only allow access to climate information covering the last few centuries. Here we present a surface-to-bedrock age scale for a 210 m long ice core recovered in 2013 from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). Combining dating by annual layer counting with absolute dates from micro-radiocarbon dating, a continuous chronology for the entire ice core archive was established using an ice flow model. Calibrated .sup.14 C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP) indicate that basal ice on Begguya is at least of early Holocene origin. A series of samples from a shallower depth interval (199.8 to 206.6 m) were dated with near-uniform .sup.14 C ages (3 to 5 ka cal BP). Our results suggest this may be related to an increase in annual net snow accumulation rates over this period following the Northern Hemisphere Holocene Climate Optimum (around 8 to 5 kyr BP). With absolute dates constraining the timescale for the last 8 kyr BP, this paleo-archive will allow future investigations of Holocene climate and the regional evolution of spatial and temporal changes in atmospheric circulation and hydroclimate in the North Pacific.
Elucidating when Neanderthal populations disappeared from Eurasia is a key question in paleoanthropology, and Belgium is one of the key regions for studying the Middle to Upper Paleolithic ...transition. Previous radiocarbon dating placed the Spy Neanderthals among the latest surviving Neanderthals in Northwest Europe with reported dates as young as 23,880 ± 240 B.P. (OxA-8912). Questions were raised, however, regarding the reliability of these dates. Soil contamination and carbon-based conservation products are known to cause problems during the radiocarbon dating of bulk collagen samples. Employing a compound-specific approach that is today the most efficient in removing contamination and ancient genomic analysis, we demonstrate here that previous dates produced on Neanderthal specimens from Spy were inaccurately young by up to 10,000 y due to the presence of unremoved contamination. Our compound-specific radiocarbon dates on the Neanderthals from Spy and those from Engis and Fonds-de-Forêt demonstrate that they disappeared from Northwest Europe at 44,200 to 40,600 cal B.P. (at 95.4% probability), much earlier than previously suggested. Our data contribute significantly to refining models for Neanderthal disappearance in Europe and, more broadly, show that chronometric models regarding the appearance or disappearance of animal or hominin groups should be based only on radiocarbon dates obtained using robust pretreatment methods.
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