Trace element levels in Italian honeybees and wild plants: which factors matter?

Honey bees (Apis mellifera L.) can be considered interesting biosamplers for monitoring the contaminants they may accumulate as a function of distance and time since they are exposed to these compounds either directly or indirectly. The aim of this research was to investigate how the levels of essential and non-essential trace elements in honey bees and plants are altered by hive management (organic or conventional), agricultural practices, and seasonal conditions. The levels of iron, zinc, copper, lead, and cadmium were determined in honey bees and wild plants from six different apiaries located in four Italian regions using atomic absorption spectrometry. Iron was the most abundant essential trace element, followed by zinc, while copper was an order of magnitude less abundant. Honey bees from conventional farms had significantly higher copper levels than those from organic farms. Regarding the non-essential elements, only honey bee samples from apiary 6 (conventional) showed cadmium levels of around 0.1 µg/g wet weight, and only some samples from apiary 4 (conventional) showed an average lead level of 0.83 µg/g wet weight. Among the factors tested, the season (spring and summer) and the apiary management were critical factors affecting content of trace elements in honey bees. In particular, the season is the one that has the greatest influence on element content, highlighting the possible adverse effects of climate change on honey bee health.