Assessing heavy metal pollution by biomonitoring honeybee nectar in Córdoba (Spain)

Nectar of honeybee colonies has been used in order to identify heavy metals and establish the benefit of this type of studies as a tool for environmental management. For these goals, samples of nectar were obtained from Apis mellifera hives placed in the city of Córdoba (Spain) and its surroundings. Five stations (each with two hives) were selected and samples were collected from May to July of 2007, 2009 and 2010. Concentrations of Pb, Cr, Ni and Cd in nectar were determined by graphite furnace atomic absorption spectrophotometry. Substantial spatial and temporal differences were detected and compared with the values found in bee bodies in a previously published study based on samples obtained simultaneously with those presented in this work. Upper reference thresholds established for this investigation were surpassed frequently by the measures obtained, being Cr (21.43% of samples), stations S3 (22.22%) and S4 (11.12%) year 2009 (22.22%) and the month of July (23.68%) the metal, the locations and the periods that exceeded more times these references. Regarding the Cd, which was studied only in 2010, 33.33% of the nectar samples exceeded the upper reference thresholds. Comparing the biomonitoring of bee bodies and nectar, some coincidences were found, although they showed different results for highest worrisome values of metal, station and year. This suggests that both methods can give complementary information in the surveillance systems of atmospheric pollution.