Assessment of heavy metal pollution in Córdoba (Spain) by biomonitoring foraging honeybee

The degree of heavy metal (Hg, Cr, Cd, and Pb) pollution in honeybees (Apis mellifera) was investigated in several sampling sites around central Italy including both polluted and wildlife areas. The honeybee readily inhabits all environmental compartments, such as soil, vegetation, air, and water, and actively forages the area around the hive. Therefore, if it functions in a polluted environment, plant products used by bees may also be contaminated, and as a result, also a part of these pollutants will accumulate in the organism. The bees, foragers in particular, are good biological indicators that quickly detect the chemical impairment of the environment by the high mortality and the presence of pollutants in their body or in beehive products. The experiment was carried out using 24 colonies of honeybees bred in hives dislocated whether within urban areas or in wide countryside areas. Metals were analyzed on the foragers during all spring and summer seasons, when the bees were active. Results showed no presence of mercury in all samples analyzed, but honeybees accumulated several amounts of lead, chromium, and cadmium. Pb reported a statistically significant difference among the stations located in urban areas and those in the natural reserves, showing the highest values in honeybees collected from hives located in Ciampino area (Rome), next to the airport. The mean value for this sampling station was 0.52 mg kg(-1), and July and September were characterized by the highest concentrations of Pb. Cd also showed statistically significant differences among areas, while for Cr no statistically significant differences were found.

Honeybees (Apis mellifera L.) have great potential for detecting and monitoring environmental pollution, given their wide-ranging foraging behaviour. Previous studies have demonstrated that concentrations of metals in adult honeybees were significantly higher at polluted than at control locations. These studies focused at a limited range of heavy metals and highly contrasting locations, and sampling was rarely repeated over a prolonged period. In our study, the potential of honeybees to detect and monitor metal pollution was further explored by measuring the concentration in adult honeybees of a wide range of trace metals, nine of which were not studied before, at three locations in the Netherlands over a 3-month period. The specific objective of the study was to assess the spatial and temporal variation in concentration in adult honeybees of Al, As, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, V and Zn. In the period of July–September 2006, replicated samples were taken at 2-week intervals from commercial-type beehives. The metal concentration in micrograms per gram honeybee was determined by inductive coupled plasma–atomic emission spectrometry. Significant differences in concentration between sampling dates per location were found for Al, Cd, Co, Cr, Cu, Mn Sr, Ti and V, and significant differences in average concentration between locations were found for Co, Sr and V. The results indicate that honeybees can serve to detect temporal and spatial patterns in environmental metal concentrations, even at relatively low levels of pollution.