Tracing old carbon sources in Hungarian nectar samples using radiocarbon analysis

In our previous research, we observed a discrepancy between the apparent¹⁴C age of the carbon content of honey samples and their known age, date of the collection. The aforementioned studies demonstrated the existence of substantial old carbon intake, even older than five years, as evidenced by the outcomes of bomb-peak based radiocarbon dating. In order to ascertain the cause of the anomalies identified, a targeted nectar sample collection was conducted in Hungarian sampling areas. Consequently, the carbon isotope ratios (¹³C/¹²C and ¹⁴C/¹²C) of individual nectar samples from black locust, linden, phacelia, rapeseed and apple were determined by isotope ratio mass spectrometry (IRMS) and accelerator mass spectrometry (AMS). Furthermore, ¹⁴CO₂ data from an international atmospheric background station were employed for comparative purposes. The presented results demonstrate that the aforementioned anomalies, previously detected in honey, can also be observed in nectar samples. It has been demonstrated that carbon deposits of up to three years old, and in some cases exceeding 60-70 years of age, can be identified in nectars. In addition to representing the first ¹⁴C/¹²C nectar results, the findings underscore the potential for older carbon stored in soil or plants to enter the food chain through nectar.