Trace element and isotopic analyses of raw and commercial beehive products
thesisposted on 2022-03-28, 15:38 authored by Xiaoteng Zhou
Bees have existed on the planet for more than 100 million years and their relationship with early humans dates to the Pliocene period (5.3 million to 2.6 million years ago). As a result of recent human industrial activity, bees' foraging environments have been subject to variable levels of contamination. Consequently, bees have been used as bio-indicators to assess anthropogenic contamination. The primary product of bees is honey, a valued and popular human food. However, honey can be subject to adulteration via the addition of sugars and misleading labelling in relation to its geographic origin. Some international studies have evaluated beehive products for their authenticity and use in environmental monitoring. This study builds on existing approaches by applying multiple geochemical analytical techniques to link environmental sources to the concentrations and compositions of both raw and commercial beehive products. This thesis uses trace element analysis and isotopic techniques to: (a) evaluate the use of bees as environmental bio-indicators; (b) investigate the quality of Australian and global honey; and (c) explore a valid method to authenticate the geographic origin of honey. Trace element analysis of beehive products demonstrates that measurements of As, Pb, Mn and Zn in two bee species (Apis mellifera, European honey bees and Tetragonula carbonaria, an Australian native bee species) correlates to co-located soils and dusts. Furthermore, Pb isotopic composition analysis verifies that the contamination found in bees can be attributed to a range of local sources, specifically, current mining activities in the city of Broken Hill (NSW), former leaded petrol depositions and geogenic background according to their locations. Carbon isotopic ratios (13C/12C) and trace elements are used in this thesis to identify if commercial honey samples (from Africa, Asia, Europe, North America and Oceania) have been adulterated by synthetic sugars derived from C-4 plants. These techniques are also used to test whether the stated geographic information on the honey samples is correct. The carbon isotopic analysis demonstrates that the adulteration practice of adding C-4 sugars remains a common problem in the Australian and global market, with a 17 % and 27 % adulteration rate, respectively. Manganese, P, K and Sr concentrations are shown to be the most important trace elements for distinguishing Australian from international honey. Overall, this thesis contributes to the growing body of research that evaluates the effectiveness of bees and their respective products for use as bio-indicators of current and legacy trace element contamination. The research findings also demonstrate that isotopic composition and trace element concentrations can be used to authenticate and establish the geographic origin of honey, which has benefits for bona fide honey producers and consumers alike.