Investigation of levels of some heavy metals (Cr, Cu, Zn, As, Se, Cd, and Pb) present in cattle fodder, water, milk, hair and manure in Malta

Abstract

The objective of this study was to assess the levels of seven heavy metals, four essential elements, Cr, Cu, Zn and Se, and three toxic elements, As, Cd and Pb, through the life cycle of cattle from the dairy cattle farm in Malta, to determine the pollution levels, by using two different equipment. The first technique used was Atomic Absorption Spectrometry (AAS) in which 110 milk, 110 hair, 15 fodder, and 11 manure samples were collected in 11 weeks, started at the last week of September and finished in mid-December, and their heavy metal concentrations were determined for Cu only. The conventional method was used to prepare all these samples. Cu concentration in milk samples showed high levels in each animal separately during this study’s period, which was found to be higher than the maximum level of 0.010mg/l, in accordance with FAO & WHO. The concentration was significantly high in Autumn, whereas it reached its lowest in Winter. On the other hand, the hair samples results had much higher concentrations than those in milk. The Cu concentration was relatively affected by colour. The highest Cu concentration was noted in black haired cows, while the cows with brown hair colour presented similar results but less than the black-haired one. In addition, Cu concentration in fodder showed that there is a significant difference between several types of fodder. Moreover, in manure samples the highest Cu concentration was in week 5, while the lowest was noted in week 7. Manure, fodder and hair had no significant seasonal effect. The second technique, Inductively Coupled Plasma - Optical Emission Spectrometry (ICPOES), was used on all seven heavy metals for a period of one year for all samples, except for hair which had a period of 8 months instead, to observe the seasonal effect. The microwave digestion preparation method was used. Cr resulted to have the highest seasonal effect, for all types of samples, during Winter, Spring and early Summer, with its highest concentrations being 0.880 ]] ppm in fodder, 0.720 ppm in hair, and 0.027 ppm in milk. Cu had the highest seasonal effect during the seasons of Winter and Spring for all samples and was also high in early Summer in hair. Its concentrations were 17.9 ppm in fodder, 10.9 ppm in hair, and 0.213 ppm in milk. Zn was found to be predominant in all samples during the season of Winter, along with milk and hair also having high levels during Summer, with concentrations of 63.1 ppm in fodder, 149 ppm in hair and 6.81 ppm in milk. As had the most seasonal effect during Summer or Winter, with the majority being in Summer. The concentration in fodder was 0.780 ppm, 1.22 ppm in hair, and 0.181 ppm in milk. Se reached seasonal effect during each season except for Winter, with most elements being mostly affected in Spring and Summer. Its highest fodder concentration was 0.740 ppm, hair was 0.130 ppm and milk 0.113 ppm. Cd concluded with seasonal effect being mostly present during Spring, except for Manure, which was highest during Winter, with concentrations of 0.080 ppm in fodder, 0.060 ppm in hair and 0.017 ppm in milk. The overall concentrations of Cd were lower than the permissible limit of 0.005 ppm. Lastly, Pb, resulted in being affected in each season, except for Autumn, with concentrations of 0.380 ppm in fodder, 0.130 ppm in hair and 0.007 ppm in milk. Pb was found to be higher than the permissible limit of 0.020 ppm. With regards to water, all samples were seasonally affected, however, their concentrations remained within the permissible limit. As for manure, it had the highest concentrations out of all the inputs and outputs, which is a positive result since manure does not directly affect the human food chain. The analysis of all the seven heavy metals’ concentrations in milk were determined using two digestion methods and comparing them for the preparation of samples. It was concluded that good recovery was achieved for both methods, in which method 1 presented higher concentrations in all elements, except for As and Se. Zn presented no changes. Furthermore, a comparison between black and white hair was carried out, resulting in no noticeable significance, except for a mild difference in Cr. This study concluded that the presence of some heavy metals’ concentrations are alarming indicators of high level of pollution in Malta.