Pollen analysis and heavy metals detection in honey samples from southern Nigeria

Pollen analytical study of two locally produced honey samples, collected from Akwa Ibom and Cross River State, Southern Nigeria, were carried out in order to ascertain the preferentially foraged plants by honey bees, as well as the concentration of heavy metals. Samples were subjected to standard laboratory procedures using an acetolysis mixture (pollen analysis) and atomic absorption spectrometry (heavy metals). The results from the analysis revealed 32 taxa belonging to 17 botanical families. The number of pollen grains in the honey samples varied significantly (between 4,887 - 12,755 pollen grains), indicating their richness in pollen grains. 12 elements – Ni, Cu, Zn, Se, Br, K, Ca, Ti, Cr, Mn, Rb, and Fe were detected. Potassium had the highest concentration, followed by iron, calcium, titanium, zinc, copper, chromium, nickel, among others. What is more, in this study, some important honey plants: Spondias mombin, Daniella oliveri, Manihot esculenta, Treculia africana, Syzigium guineensis, Diospyros mespiliformis, Parkia biglobosa, Terminalia superba, Senna hirsuta, among others, were found to be predominant and have been identified to be characteristic of the vegetation typical of Southern Nigeria. With regard to honey, this study gives an indication of the geographical and botanical origins, as well as types, source, and degree of contamination, and also an overall measure of honey purity. Such information, when displayed, can help consumers make informed decision when purchasing honey and will also help beekeepers to avoid possible contamination. Moreover, it will assist regulatory agencies in taking proper measures for environmental and consumer protection, since the concentration of heavy metals in honey is influenced by environmental pollution.