Heavy metal values in honey samples
Heavy metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) mean values and standard errors of honey samples are shown in Table 1. In honey samples, significant statistical differences were found among the locations in terms of Cr, Cu, Fe, Mn, Ni and Zn, except Cd and Pb, (P<0.05).
The Cd value of honey samples ranged from 4.301–6.898 µg/kg, and the difference among locations was statistically insignificant. Bosancic et al. (2020) stated that no statistically significant differences were found between conventional and organic honey production systems. On the other hand, Arslan and Arıkan (2013) found the highest amount of Cd in honey samples taken from stations close to the highway. Adugna et al. (2020) found Cd contents of honey samples from different regions in the range of 17–35 μg/kg,which was higher compared with our results.
The maximum Cu content of honey samples was 0.950 mg/kg at L2, whereas the minimum values was 0.395 mg/kg at (L7) (P<0.05). Demirezen and Aksoy (2005) found that the Cu content of honey samples taken from sites close to residential areas was higher than those from rural areas (P˂0.01). On the other hand, Silici et al. (2016) stated that there was no statistical difference among the Cu values of honey samples taken from different distances to a thermal power plant.
The Cr, Fe, Mn, Ni, and Zn values of honey samples were highest around the city (L3, 67.01 µg/kg; L4, 67.01 µg/kg; L1, 1,270 mg/kg; L3, 0.216 mg/kg; L4, 1.635 mg/kg) and lowest in the rural sites (L8, 27.70 µg/kg; L6, 6.266 mg/kg; L6, 0.520 mg/kg; L8, 0.106 mg/kg; L6, 1.039 mg/kg).
Leblebici (2006) reported that the Cr content of honey samples taken from sites close to residential areas was higher than that from rural areas (P<0.05). Gurel et al. (1998) found significant differences among honey samples obtained from different locations in terms of Fe concentration (P<0.01). Leblebici (2006) found the Fe content of honey samples taken from locations close to the city center was higher than that of locations far from the city center (P<0.05). Arslan and Arıkan (2013) did not detect a significant difference among the Mn values of honey samples obtained from colonies placed at different distances from the highway. Taha et al. (2017) found that the Ni content in honey samples taken from colonies placed at different distances to the cement factory was higher in samples close to the factory (P<0.05). Demirezen and Aksoy (2005) stated that the Ni content of honey samples taken from sites close to residential areas was higher than those from rural areas (P˂0.01). Taha et al. (2017) found the Zn content of honey samples taken from colonies placed at different distances from a cement factory was higher in samples close to the factory (P<0.05). The Zn values (1.039-1.635 mg/kg) obtained in our study were lower than the value (4.814 mg kg) determined by Aliu et al. (2020) in honey.
The Pb content of honey samples ranged between 0.073 and 0.118 mg/kg, and the differences among the locations were statistically insignificant. On the other hand, Roman (2010) determined that the Pb content of honey samples obtained from settlements was higher than the values obtained from agriculture and forest areas (P<0.05). The Pb value (0.073-0.118 mg/kg) obtained in our study was similar to the value (0.02-0.098 mg/kg) determined by Purcarea et al. (2017) in Polish honeys.
In our study, the Cd and Pb values of honey samples were within the International Food Standard values (Alimentarius 2015).
Heavy metal values in pollen samples
The mean values and standard errors of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in pollen samples are given in Table 2. In pollen samples, the differences among the locations were statistically significant in terms of Cr, Cu, Fe, Mn, Ni, Pb, and Zn, except Cd, (P<0.05).
The Cd contents of the pollen samples ranged between 6.535 and 11.304 µg/kg, and the difference among the locations was statistically insignificant. Similarly, Arslan and Arıkan (2013) stated that there was no significant difference among the Cd values of pollen samples taken from colonies placed at different distances from the highway.
The Cd value (6.535 - 11.304 µg/kg) obtained in our study was lower than the value (26.1- 92.0 µg/kg) determined by Formicki et al. (2013) in Poland pollen.
The Cr, Cu, Fe, Mn, Ni, and Pb values of pollen samples were highest at sites around the city (L3, 79.36 µg/kg; L4, 7.275 mg/kg; L4, 96.95 mg/kg; L1, 19.149 mg/kg; L4, 0.384 mg/kg; L4, 0.180 mg/kg) and lowest in the rural sites (L8, 46.10 µg/kg; L6, 3.915 mg/kg; L7, 61.40 mg/kg; L6, 5.356 mg/kg; L7, 0.218 mg/kg; L8, 0.059 mg/kg).
Conti and Botrè (2001) found higher Cr contents in pollen samples obtained from inner-city locations compared to urban locations (P<0.01). Taha et al. (2017) found that the Cu content of pollen samples taken from colonies placed at different distances from a cement factory was higher in samples close to the factory (P<0.05). Taha (2015) found significant statistical differences among pollen obtained from different plants in terms of Fe content (P<0.05). Arslan and Arıkan (2013) did not find a significant statistical difference among the Fe values of pollen samples obtained from colonies placed at different distances from the highway. Fakhimzadeh and Lodenius (2000) found no significant statistical difference among industrial, urban, and rural areas in terms of Mn values in pollen samples. Taha et al. (2017) found that the Ni content in the pollen samples taken from the colonies placed at different distances to a cement factory was higher in the samples close to the factory (P<0.05). Conti and Botrè (2001) found higher Pb contents of pollen samples taken from the colonies in the city center compared to those from colonies around the city (P<0.01).
The Zn content of the pollen samples was highest in the urban location (L3), with 20.27 mg/kg and lowest in the rural location (L7), with 10.25 mg/kg (P<0.05). On the other hand, Arslan and Arıkan (2013) did not detect significant statistical differences among the Zn values of pollen samples obtained from colonies placed at different distances from the highway.
The Zn value (10.25-20.27 mg/kg) obtained in our study was lower than the value (75.2- 159.3 µg/g) determined by Formicki et al. (2013) from Poland pollen. Altunatmaz et al. (2017) stated that mineral levels are related to plant type rather than to the soil and geographical situation.
Heavy metal results in honey bee samples
Heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn; mean values and standard errors) of honey bee samples are summarized in Table 3.
The Cd content of honey bee samples was highest in the site around the city (L4), with 20.78 µg/kg, and lowest at the rural site (L8), with 9.52 µg/kg (P<0.05). Similar results were found by Conti and Botrè (2001), where the Cd content of bee samples obtained from the inner-city location was higher than that from the surrounding locations (P<0.01). Similarly, Fakhimzadeh and Lodenius (2000) found a higher Cd content of bee samples taken from urban and industrial areas compared to samples from rural areas (P<0.05). The Cd values (9.52-20.78 µg/kg) obtained in our study were lower than the range (0.03-0.30 mg/kg) determined by Goretti et al. (2020).
The Cr content of honey bee samples was highest, at 99.24 µg/kg, in the urban site (L3) and lowest, at 58.24 µg/kg, in the rural site (L7) (P<0.05). Gutiérrez et al. (2015) found the highest Cr contents in honey bee samples taken from different locations, including urban, industrial, agricultural, and forested areas (P˂0.01).
In this study, the Cu content of honey bee samples was highest in the site around the city (L3), with 17.18 mg/kg, and lowest at the rural site (L6), with 12.18 mg/kg (P<0.05). Roman (2010) found that the Cu contents of honey bee samples obtained from residential areas were higher than those obtained from agricultural and forest areas (P<0.05). Silici et al. (2016), on the other hand, did not detect a statistical difference among the Cu values of honey bee samples taken at different distances to a thermal power plant.
Te Fe contents of honey bee samples were highest at the site around the city (L3), with 101.81 mg/kg, and lowest at the rural site (L6), with 82.46 mg/kg (P<0.05). Nisbet et al. (2013) reported that the Fe content of honey bee samples taken from locations with different environmental and flora characteristics varied from region to region (P<0.05). Taha et al. (2017) found that the Fe contents in honey bee samples taken from colonies placed at different distances to a cement factory were higher in samples close to the factory (P<0.05).
The Mn contents of honey bee samples were highest at the site around the city (L1), with 35.55 mg/kg, and lowest at the rural location (L6), with 15.63 mg/kg (P<0.05). On the other hand, Silici et al. (2016) did not detect a statistical difference among the Mn values of honey bee samples taken at different distances to a thermal power plant.
The Ni values of honey bee samples were highest at the site around the city (L3), with 0.432 mg/kg, and the lowest at the rural location (L7), with 0.201 mg/kg (P<0.05). Nisbet et al. (2013) found a statistical difference among the Ni contents of honey bee samples obtained from locations with different environmental and floral characteristics (P<0.05).
The Pb contents of honey bee samples were highest at the site around the city (L3), with 0.358 mg/kg, and lowest at the rural site (L8), with 0.192 mg/kg (P<0.05). Roman (2010) found higher Pb levels of honey bee samples in residential areas compared to agricultural and forest areas (P<0.05). The Pb values (0.192-0.358 mg/kg) obtained in our study were lower than those (4-27 µg/g) determined by Leita et al. (1996). On the other hand, our values were similar to those (0.14-0.52 mg/kg) determined by Perugini et al. (2011).
The Zn contents of honey bee samples were highest at the site around the city (L4), with 44.58 mg/kg, and lowest at the rural location (L8), with 29.93 mg/kg (P<0.05). Nisbet et al. (2013) reported that the Zn values of honey bee samples taken from locations with different environmental and floral characteristics varied from region to region (P<0.05), In a similar study, Taha et al. (2017), analyzing honey bee samples from colonies placed at different distances to a cement factory, found higher Zn values in the samples closer to the factory (P<0.05).