We present a radiocarbon (14C) dataset of tropospheric air CO2, forest soil air CO2, and soil CO2 emissions over the course of one growing season in a Scots pine forest in southern Finland. The CO2 collection for 14C accelerator mass spectrometry (AMS) analysis was done with a portable, suitcase-sized system, using molecular sieve cartridges to selectively trap CO2. The piloting measurements aimed to quantify the spatial, seasonal and diurnal changes in the 14C content of CO2 in a northern forest site. The atmospheric samples collected above the canopy showed a large seasonal variation and an 11‰ difference between day and nighttime profiles in August. The higher Δ14C values during night are partly explained by a higher contribution of 14C-elevated soil CO2, accumulating in the nocturnal boundary layer when vertical mixing is weak. We observed significant seasonal trends in Δ14C-CO2 at different soil depths that reflected changes in the shares of autotrophic and heterotrophic respiration. Also the observed diurnal variation in the Δ14C values in soil CO2 highlighted the changes in the origin of CO2, with root activity decreasing more for the night than decomposition.

We report radiocarbon (14C) dates on bone samples of Ursus ladinicus, a small cave bear species well adapted to a life in the mountains, whose remains were found in Conturines Cave. Located at 2775 m asl in the Dolomites of northern Italy, this cave is by far the highest known cave bear site worldwide. Eleven 14C dates obtained by the Belfast and Oxford laboratories on samples showing good collagen preservation yielded consistent ages in excess of 46–50 ka BP. These results show that contrary to the previously held view these cave bear remains are older than Marine Isotope Stage 3, and likely date from a warm climate period with a high treeline, possibly the Last Interglacial.

This article presents the first radiocarbon (14C) results from the Late Bronze Age levels of Tel Azekah (Israel). The results testify to the long and prosperous occupation of the site during this period, commencing at least in LB IIA and ending with a severe destruction at the close of LB III. In the extra-mural quarter (Area S2), a pre-monumental building phase (S2-6) dates to the 14th or early 13th century BCE. Two sub-phases of a public building constructed above this yielded dates in the second half of the 13th century and first two-thirds of the 12th century BCE, suggesting that occupation persisted through the “Crisis Years” of the eastern Mediterranean region. On the top of the mound, in Area T2, the destruction of the final LB III level (T2-3) most likely occurred near the end of the 12th century BCE. The preliminary Azekah results are in good agreement with existing data from Lachish and Megiddo, but seem at odds with results from nearby Tel es-Safi/Gath.

A robust marine radiocarbon (14C) reservoir correction (ΔR) is essential for calibrating 14C dates of marine mollusks and fish bones routinely found in archaeological sites as discarded food remains and bones of terrestrial animals (including humans) with an appreciable marine diet. New ΔR values are reported for the atoll archipelago of the Marshall Islands, eastern Micronesia. Atolls consist of biogenetic material—mostly coral and foraminifera—that can be directly dated for establishing sequences of atoll emergence and islet development. After sectioning and examination using scanning electron microscopy (SEM) to screen for sample diagenesis, 6 pristine branch coral samples were selected from the modern oceanside beach, 3 archaeological sites, and islet developmental facies from Ebon Atoll (4º34′N, 168º41′E). Each sample was analyzed by U-series and accelerator mass spectrometry (AMS) 14C showing no substantial temporal ΔR variations and yielding a weighted mean ΔR of 41±42 yr1 spanning ~500 yr before earliest human colonization (the period when islets first became habitable) through the entire 2000-yr occupation sequence. Reliable published ΔR values for Micronesia and Δ14C data for Palmyra Island, together with our results for Ebon Atoll, indicate that the Pacific North Equatorial Counter Current is almost stable for the past 2500 yr.

Radiocarbon (14C) activity in groundwater can be used to determine subsurface residence time up to ∼40 kyr, providing crucial information on dynamic properties of groundwater and on paleoclimate. However, commonly applied sampling methods for dissolved inorganic carbon (DIC-14C) are prone to low level of modern atmospheric contamination, resulting in underestimation of groundwater ages that cluster around 30–40 kyr. We extract CO2 gas from groundwater using a device originally developed for studies of noble gas radionuclides. Carbon is collected in the gas phase, eliminating the possibility of fostering microbial activities and aqueous chemical reactions during sample storage. This method collects CO2-14C and radiokrypton (81Kr and 85Kr) samples simultaneously. The presence of any shorter-lived 85Kr is used to evaluate the degree of atmospheric contamination during sampling or mixing of young groundwater. Most groundwater samples showed lower CO2-14C activities than those of DIC-14C, presumably due to the absence of atmospheric contamination. Samples with 81Kr age exceeding 150 kyr have no detectable CO2-14C except where mixing sources of young groundwater is suspected. These field data serve as confirmations for the reliability of the newly presented sample collection and CO2-14C method, and for the outstanding roles of radiokrypton isotopes in characterizing old groundwater.