NC State
(RETRACTED) Tanase, C., Nisca, A., and Lopez, A. (2021). "Assessment of heavy metal content in tree barks: Picea abies, Pinus sylvestris, and Pinus nigra," BioResources 16(3), 5047-5057.


Extracts obtained from the bark of woody plants are used for their high content in polyphenolic compounds with various biological activities. Thus, it is important to evaluate the heavy metals in various tree barks, as these pollutants may end up in the final product, affecting its properties and having potential health implications. This study assessed the heavy metal content in the barks of spruce (Picea abies) and pine (Pinus sylvestris and Pinus nigra) collected from different areas in Romania. After collecting the vegetal material from different sites, the bark samples were appropriately processed and analyzed via inductively coupled plasma optical emission spectroscopy (ICP-OES). The results showed that 6 out of 8 tested samples exceeded the normal values of selenium (Se). Arsenic (As) and cadmium (Cd) were not detected in any sample, while other metals (chromium (Cr); lead (Pb); nickel (Ni)) were detected in variable amounts. Moreover, relatively high levels of heavy metals were recorded in a spruce bark sample collected from the seemingly most unpolluted site. Although further studies are needed to determine the effects of these heavy metals on extraction yields and their transfer into the final extracts, their presence might indicate a potential problem.

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RETRACTED: July 28, 2021. The authors retract their study due to ethical issues regarding plant samples.