WHEAT SEED (TRITICUM AESTIVUM L.) RADIOCARBON CONCENTRATION OVER THE LAST 75 YEARS

ABSTRACT Here we report radiocarbon measurements made on wheat seed tissue (Triticum aestivum L.; winter or spring type growth habit), from the seed archive of the IPK Gatersleben, Sachsen-Anhalt, Germany, which was harvested between 1946 and 2020. The results give an overview of 75 years of radiocarbon concentration evolution in agricultural plant products. The wheat tissue radiocarbon concentrations follow known pre- and post-bomb radiocarbon records, such as the atmospheric Jungfraujoch, Schauinsland, and NH1 datasets. Based on a Northern Hemisphere growing period from April to July, the Gatersleben seed tissue radiocarbon concentration indicates incorporation of fossil carbon of about 1% with respect to the high alpine, clean-air CO2 of the Jungfraujoch station between 1987 and 2019. We propose to use the pre- and post-bomb radiocarbon record of Gatersleben wheat as a reference in forensic investigations, such as the age estimation of paper by analyzing starch used in paper manufacture. Additionally, an advantage of the record reported here lies in its extensibility by adding new analyses from future harvests.

Surface radiocarbon record from the northern Indian Ocean: understanding surface ocean processes

<p>Due to nuclear bomb tests during mid 1950s and 1960s, enormous amount of bomb radiocarbon was introduced into the atmosphere and subsequently to the ocean. Corals growing in shallow oceanic region record the radiocarbon variations in ocean surface waters. The bomb radiocarbon signature embedded in coral can be useful in providing information about natural processes affecting the surface waters of the region. In this regard, coral based radiocarbon records from the Lakshadweep Islands and the Andaman Islands from the northern Indian Ocean has been analysed. The analysed coral ∆<sup>14</sup>C values of recent period show comparable or even higher than the atmospheric ∆<sup>14</sup>C values, suggesting that major fraction of bomb radiocarbon have transferred in to the ocean. The northern Andaman region show ∆<sup>14</sup>C decline rate of about 3.1 ‰ yr<sup>-1</sup> between 1978 to 2014. Whereas, the southern Bay of Bengal and the Lakshadweep records show relatively lower decline rate of 2.5 ‰ yr<sup>-1</sup> for the same period. Based on the coral and atmospheric radiocarbon values, air-sea CO<sub>2</sub> exchange rate over the Lakshadweep and Andaman region has been estimated. The bomb radiocarbon based estimate of air-sea CO<sub>2</sub> exchange rate over Lakshadweep is 13.4 ± 2.1 mol m<sup>-2</sup> yr<sup>-1</sup> and over northern Andaman is 8.8 ± 1.3 mol m<sup>-2</sup> yr<sup>-1</sup>. The Lakshadweep region show net regional CO<sub>2</sub> flux of 2.5 ± 0.4 Tg C yr<sup>-1</sup>, while the northern Andaman region shows value of -0.3 ± 0.04 Tg C yr<sup>-1</sup>. This study discusses the spatial and temporal radiocarbon changes in the northern Indian Ocean and has implications to constraining the carbon flux over the region.</p>

A multi-resolution ocean simulation of the anthropogenic radiocarbon transient

<p>We have implemented <sup>14</sup>C and further abiotic tracers (<sup>39</sup>Ar, CFC-12, and SF<sub>6</sub>) into the state-of-the-art ocean circulation model FESOM2. Different to other global ocean circulation models, FESOM2 employs unstructured meshes with variable horizontal resolution. This approach allows for improvements in areas which are commonly poorly resolved in global ocean modelling studies such as upwelling regions, while keeping the overall computational costs still sufficiently moderate. Here, we present results of a transient simulation running from 1850-2015 CE tracing the evolution of the bomb radiocarbon pulse with a focus on the evolution of marine radiocarbon ages. In addition we explore the potential of <sup>39</sup>Argon to complement <sup>14</sup>C dating of marine waters.</p>

Radiocarbon in modern carbon cycle research

<p>Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10<sup>28</sup> atoms or about 0.6 tons of radiocarbon (<sup>14</sup>C), leading to a doubling of the <sup>14</sup>C/C ratio in tropospheric CO<sub>2</sub> of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced <sup>14</sup>C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO<sub>2</sub> into the atmosphere has become the dominant driver of the <sup>14</sup>C/C ratio in global atmospheric CO<sub>2</sub>. The observed decreasing <sup>14</sup>C/C trend in atmospheric CO<sub>2</sub> may thus help scrutinising the total global release of fossil fuel CO<sub>2</sub> into the atmosphere. On the local and regional scale, atmospheric <sup>14</sup>C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO<sub>2</sub> signals and to estimate trends of regional fossil fuel CO<sub>2</sub> emissions. Some prominent examples where the bomb <sup>14</sup>CO<sub>2</sub> disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.</p>

Eye lens Δ14C validates otolith-derived age estimates of Gulf of Mexico reef fishes

We tested whether Δ14C values of eye lens protein (crystallin) formed in early life could be utilized to validate marine bony fish age estimates via the bomb radiocarbon chronometer. The slope of the relationship between red snapper (Lutjanus campechanus; n = 8; 0 to 27 years old), otolith and eye lens core Δ14C values was not significantly different than 1, which was also true for seven additional reef fish species (n = 21; 0 to 24 years old). Results demonstrate eye lens core Δ14C can be utilized to validate age estimates of marine fishes, which will be useful in numerous age validation applications.

Inferring life history characteristics of the oceanic whitetip shark Carcharhinus longimanus from vertebral bomb radiocarbon

High-precision vertebral bomb radiocarbon measurements likely track philopatric movements in oceanic whitetip shark Carcharhinus longimanus.

RADIOCARBON AND DENDROCHRONOLOGY APPLIED IN A LEGAL DISPUTE: A CASE FROM COLOMBIA

ABSTRACT In 2015 a dispute arose between an electricity company (EC) and smallholder of a teak plantation when the EC felled 80 trees (without consent of the owner) in a linear transect under a rural power-line-corridor (PLC), fragmenting the teak stand in two portions. The EC stated that there were no planted trees in the area when the PLC was established in 2008. The owner asserted he planted the stand in 2006 so in 2008 the company should have seen the planted trees. We used the bomb radiocarbon (14C) signal of three felled trees and dendrochronological dating of five trees, three felled by the EC and two felled by us in 2016, to do this study to determine the age. We found that the first growth rings were dated to 2005 both in the trees felled by the EC in 2015 and felled by us in 2016, one year before that reported by the owner (2006). This year corresponds to the wood present in the cuttings during the stand’s planting year. These facts are in agreement with the owner’s testimony. The plantation was 10 years old in 2015.