Yunchong Fu

Determination of Ultralow Level 129I/127I in Natural Samples by Separation of Microgram Carrier Free Iodine and Accelerator Mass Spectrometry Detection

Separation of carrier free iodine from low iodine level samples and accurate measurement of ultralow level (129)I in micrograms of iodine target are essential but a bottleneck in geological dating of terrestrial system and tracer research using naturally produced (129)I. In this work, we present a carrier free method using coprecipitation of AgI with AgCl for preparing micrograms of iodine target, associated with combustion using a tube furnace for separating iodine from solid samples and anion exchange chromatography for preconcentrating iodine from a large volume of water. An accelerator mass spectrometry was used to measure ultralow level (129)I in micrograms of iodine target. The recovery of iodine in the entire separation procedure is higher than 80% and 65% for solid and water samples, respectively. One microgram iodine in the target (AgI-AgCl) can produce a stable (127)I signal for AMS measurement of (129)I/(127)I, and a detection limit of this method for (129)I is calculated to be 10(5) atoms. This will allow us to accurately determine (129)I in prenuclear geological samples of low iodine concentration with (129)I/(127)I of 10(-12), such as loess, soil, coral, rock, sediment, and groundwater. Some samples with low iodine content have been successfully analyzed, and the lowest value of the (129)I/(127)I ratio of 2 × 10(-11) was observed in 23.5 and 63.5 m loess samples collected in the Loess Plateau, China. The developed method sheds light on a wide application in earth science.

Atmospheric Fossil Fuel CO2 Traced by Δ14C in Beijing and Xiamen, China: Temporal Variations, Inland/Coastal Differences and Influencing Factors

One year of atmospheric Δ(14)CO2 were observed in 2014 in the inland city of Beijing and coastal city of Xiamen, China, to trace temporal CO2ff variations and to determine the factors influencing them. The average CO2ff concentrations at the sampling sites in Beijing and Xiamen were 39.7 ± 36.1 ppm and 13.6 ± 12.3 ppm, respectively. These contributed 75.2 ± 14.6% and 59.1 ± 26.8% to their respective annual ΔCO2 offsets over background CO2 concentrations. Significantly (p < 0.05) high CO2ff values were observed in winter in Beijing. We did not find any significant differences in CO2ff values between weekdays and weekends. Diurnal CO2ff variations were plainly evident, with high values between midnight and 4:00, and during morning and afternoon rush hours. The sampling site in the inland city of Beijing displayed much higher CO2ff inputs and overall temporal variations than the site in the coastal city of Xiamen. The variations of CO2ff at both sites were controlled by a combination of emission sources, topography, and atmospheric dispersion. In particular, diurnal observations at the urban site in Beijing showed that CO2ff was easily accumulated under the southeast wind conditions.

Cosmogenic 10Be surface exposure dating of ‘Little Ice Age’ glacial events in the Mount Jaggang area, central Tibet:

The timing and extent of ‘Little Ice Age’ (LIA) glacial advances on the Tibetan Plateau (TP) are critical for understanding climate during the past millennium. However, the lack of LIA chronologies in central Tibet makes it difficult to fully understand the nature of LIA throughout the TP. In this study, two presumed LIA moraines in the east of Mount Jaggang, Xainza range, the central TP, were examined and dated using 10Be surface exposure dating. Eight boulders from the two moraines yielded apparent 10Be exposure-ages ranging from 41 ± 31 to 529 ± 130 years. These 10Be exposure-ages indicate that glaciers advanced at least once in the Mount Jaggang area during the LIA. A relatively extensive glacial advance occurred around 267 ± 36 years, a relatively humid period as indicated by proxy data from lake sediments in the central TP. A glacial standstill might have occurred around 151 ± 36 years. The two LIA glacial events are comparable with those across the TP. However, much more efforts should be made on dating of LIA moraines in the Mount Jaggang area to elucidate the relationships between glacial advances and climate changes during the LIA.

Authentication of Chinese vintage liquors using bomb-pulse (14)C.

The older a bottle of Chinese vintage liquor is, the higher the price it commands. Driven by the potential for higher profits, some newly-founded distilleries openly sell liquor whose storage ages are exaggerated. In China, the market for vintage liquor has become fraught with uncertainty and a pressing need has arisen to establish an effective method to authenticate the age of vintage liquors. A radiocarbon (14C) dating method is described here that can verify cellar-stored years of Chinese liquors distilled within the last fifty years. Two different flavored Chinese liquors produced in “the golden triangular region” in the Upper Yangtze River region in southwest China, with known cellar-stored years, were analyzed to benchmark the technique. Strong flavored liquors are found to be consistent with local atmospheric Δ14C values. A small offset of 2–3 years between predicted vintage years of soy-sauce flavored liquors and strong flavored liquors is found to be associated with the fermentation cycle of certain varieties. The technique can measure cellar-stored years of a wide range of liquors including those with fundamentally different aromas. This demonstrates the strength of our method in identifying suspect Chinese vintage liquors.