Rape, sunflower and forest honeys for long-term environmental monitoring: Presence of indicator elements and non-photosynthetic carbon in old Hungarian samples.

In this paper, we present the time-dependent elemental composition and AMS radiocarbon dating results of 36 rape, sunflower and forest honey samples, collected between 1985 and 2018 in geographically close locations. Based on the elemental information, we conclude that bee products regardless the type provide useful environmental information of the previous decades, such as the decreasing trend of airborne Pb emission can be traced. However, radiocarbon results agree less with the atmospheric bomb peak. Random offsets were observed in the specific radiocarbon activity of the honey samples indicating that rape, sunflower and forest honey samples are not as reliable materials for radiocarbon dating as acacia honeys. The radiocarbon results show that the rape, sunflower and forest honey samples can contain non-photosynthetic carbon, presumably derived from the soil. Thus, the complex application of honey samples for environmental reconstruction requires the species-separated investigation of bee products to reveal their adaptability for assessment approaches.

Honey as an indicator of long-term environmental changes: MP-AES analysis coupled with 14C-based age determination of Hungarian honey samples.

Several studies show that the elemental content of honey entirely depends on the botanical and geographical origin, but the information is incomplete regarding its time-dependent composition changes. Twenty-six acacia and three honey samples with unknown botanical origin were collected between 1958 and 2018 and analysed for elemental composition by Microwave Plasma Atomic Emission Spectrometry (MP-AES). The elemental analysis was coupled with independent dating method by Accelerator Mass Spectrometry (AMS) to confirm the calendar age of the honey samples and test the possibility of radiocarbon based dating of bee products, which has not been applied before. According to the analytical measurements and statistical analysis, we can conclude that the elemental composition shows change with time in the acacia honey during the last five decades. We have proven that honey preserves carbon isotopic and elemental information of its production time and thus can be applied as an environmental indicator (e.g. trace urban pollutants, precipitation, local industrial or agricultural emission) in reconstruction studies by analysing the non-degradable mineral content. Our results further show that acacia honey is a suitable material for radiocarbon dating, proved by the results compared to the atmospheric radiocarbon bomb-peak. The new approach presented for investigation of honey by radiocarbon-based age determination coupled with elemental analysis can be used in biological, dietary, archaeological or other multidisciplinary studies as well. Some samples show slightly depleted radiocarbon content. This could be an indication of local fossil CO2 emission. Based on these depleted 14C results, honey could be used for atmospheric monitoring of fossil CO2 urban or industrial hot-spots.