Seasonal Variations of Radiocarbon Content in Plant Leaves in a ¹⁴C-Depleted Area

Abstract

The determination of radiocarbon content in biogenic samples such as tree leaves and short-lived plants is crucial when studying the anthropogenic impact on the ecosystem and for detecting any alteration in stable and radioactive CO 2 . A total of 76 samples of evergreen and deciduous tree leaves as well seasonal plants were collected in winter, spring, and summer. Sampling was carried out from rural villages located in Mount Lebanon Province, Lebanon. Based on the data obtained from a previous study carried out in autumn, which showed that the selected sites are characterized by depletion of 14 C caused by the releases of pollutants and CO 2 from a cement factory in the region, further investigation was carried out in the present work to determine possible significant seasonal variations in Δ 14 C values. Reference samples of identical species were collected in the same period from a clean zone. The conventional 14 C method was used to determine the carbon isotopic ratio. Δ 14 C data are compared to those obtained in autumn. 14 C concentration in the studied sites was significantly lower than in the clean area in all seasons. ANOVA tests showed that there is a significant seasonal variation for deciduous leaves and seasonal plants, while this difference was not significant in evergreen leaves. In addition, no significant variation was recognized for different species in the same season.

Anthropogenic CO2 Emission Records in Scots Pine Growing in the Most Industrialized Region of Poland from 1975 to 2014

“…Evergreen leaves may contain carbon fixed from the previous season or even previous years. The significant scatter of 14 C concentration (up to 70‰) in the plants growing polluted area comparing to the 14 C concentration in the plants growing in the clean area has been observed also by Baydoun et al (2015). Also the results of the systematic Δ 14 C measurements of soil CO 2 flux performed in the forest environment for 1998–2001, Gorczyca et al (2013) from closed-system gas collection at the soil surface suggested that Δ 14 C values of the CO 2 emitted from the forest soil were ~40‰ higher than current atmospheric background values.…”

“…In terms of 14 C, the global CO 2 becomes depleted in 14 C, because the CO 2 from fossil fuels is devoid of any 14 C (Suess 1955). Local depletion of the radioactivity concentration (local Suess effect) can be observed in areas with higher CO 2 emissions from fossil fuel combustion (Rakowski et al 2000; Molnar et al 2007; Pazdur et al 2007; Svetlik et al 2010; Baydoun et al 2015).…”

Carbon, cesium and iodine isotopes in Japanese cedar leaves from Iwaki, Fukushima

“…In summary, our present results fully support that the evergreen leaves may contain 14 C fixed from previous years, as observed previously [ 20 , 22 ]. As a result, care should be taken when 14 C in the leaf of an evergreen tree is considered as a proxy for atmospheric 14 C with an annual time resolution.…”

Characteristics of Pine Needles Exposed to Multi-Source Pollution in Silesia: Radiocarbon Concentration in Pine Needles and Elemental Analysis of the Needles’ Surface Deposits

“…Increasing anthropogenic carbon dioxide emissions into the atmosphere due to the combustion of large amounts of fossil fuel combustion has changed the local and global carbon cycle. The impact of these carbon dioxide emissions on the isotopic concertation in trees (tree rings and foliage) is evident (Suess 1955;Molnar et al 2007;Hua et al 2013;Pazdur et al 2013;Baydoun et al 2015;Ndeye et al 2017). The physiological processes of trees, such as their photosynthesis rate and stomatal conductance, can be affected not only by carbon dioxide, but also by other air contaminants, gases, and dust associated with human activities, such as industrial processes, road transport, and low and high-stack emissions (Staszewski et al 1994).…”