Levels of metal contents in the analyzed finger millet samples
The results indicated that the samples had a variable concentration of analyte metals in three types of finger millet from the two study areas.
Table 1 indicates variation in heavy metal concentration in three types of finger millet. The manganese concentration was the highest of all the analyzed metals in all samples. Its mean concentration ranges from 2.3260 to 5.6510 mg/L, while Lead (ND to 0.024 mg/L) was the least mean concentration of all samples among the two study areas from the analyzed metals. Therefore, the trend of the analyzed metal concentration determined in all types of finger millet samples from the two study areas was almost Mn>Fe>Zn>Cu>Pb. So, The probable reasons for the variation of these metal concentrations in all three types of finger millet samples between the two study areas may be due to their genetic potential to absorb and accumulate these metals from the soil, the availability of the minerals in the soil that exist in usable forms, the degree of contamination of the soil with heavy metals, the use of different types of fertilizers, pesticides, herbicides and other chemicals,
etc (
Chandravanshi and Feleke, 2015 and
Yohannes and Chandravanshi, 2015).
Therefore, as shown in Table 2, an independent t-test at a 95% confidence level indicated that there were significant differences between the mean values of black finger millet samples in Mn, Fe, Cu, Zn and Pb, mixed finger millet samples in Mn, Zn and Pb, white finger millet samples in Mn, Fe, Cu and Pb. And there was no significance between the mean values of mixed finger millet in Fe, Cu and white finger millet in Zn in both studying areas.
Manganese status
The concentration of manganese in black finger millet from Mankusa varied from 3.693 to 3.820 mg/L with a mean value of 3.751 mg/L. Mixed finger millet ranges from 3.507 to 3.643mg/L with a mean value of 3.573 mg/L; in the white finger millet, it was 2.302 to 2.337mg/L with a mean value of 2.326 mg/L. In the case of Finoteselam, the concentration of black finger millet varied from 5.591 to 5.702 mg/L with a mean value of 5.651 mg/L. while the mixed finger millet was found to be from 2.953 to 3.097 mg/L with a mean value of 3.023 mg/L and in the white finger millet, it ranges from 2.856 to 2.886 mg/L with a mean value of 2.8695 mg/L. So, the concentration of Mn was found to be the highest of all heavy metals measured in finger millet samples. The pattern of the mean concentration of Mn in finger millet varieties was in the order of white finger millet<mixed finger millet< and black finger millet among the two study areas. From the analysis, as shown in Table 2, it was observed that the concentration of Mn with mean values of black, mixed and white finger millets from both study areas have significant differences (P<0.05). The highest and lowest mean values were recorded in Finoteselam black finger millet (5.651 mg/L) and Mankussa white finger millet (2.326 mg/L), respectively.
The result (2.326 to 5.651 mg/L) of Mn in this study was not agreed with the value (52±3mg/L to75.3± 0.3 mg/L) reported by
(Desta and Bhagwan 2014). According to the safe limit adopted by
FAO (2010), almost all of the finger millet samples in the two study areas were above the safe limit (2 mg/L). The finding of this study is in contrast to what is recommended by FAO. The daily intake amount of these metals differs from person to person based on the developmental levels, sex and the standards of the different countries they set. Therefore, According to U.S.A. standards, the R.D.I. of Mn is (2.3 mg/day) for matured adults and (2.6 mg/day) for lactating females, respectively. Because of the mean concentration of Mn in this study as compared to the FAO standard, most of the finger millet samples are not safe for consumption. But in the case of Mankussa and Finoteselam, white finger millets are safe for consumption.
Iron status
The concentration of Iron in Makussa, black finger millet, varied from 1.493 to 1.892 mg/L with a mean value of 1.695 mg/L and mixed finger millet ranged from 1.676 to 3.508 mg/L with a mean value of 2.579 mg/L and white finger millet samples vary from 1.488 to 3.082 mg/L with a mean value of 2.289 mg/L. But in the case of Finoteselam, it was 1.696 to 2.698 mg/L with a mean value of 2.196 mg/L, 1.910 to 2.389 mg/L with a mean value of 2.155 mg/L and 1.187 to 1.642 mg/L with a mean value of 1.412 mg/L for black, mixed and white finger millet samples respectively. So, the concentration of Fe was found to be the second highest of all heavy metals measured in finger millet samples. The pattern of the mean concentration of Fe in finger millet varieties was in the order of white finger millet < mixed finger millet < black finger millet in the Mankussa study area while in the case of Finoteselam, it was Black finger millet < white finger millet < mixed finger millet. From the analysis, it was observed that the concentration of Fe with mean values in mixed finger millets from both areas had no significant difference because the P value of the samples was P=0.188 which is greater than 0.05 at 95% confidence level while the concentration of Fe in black and white finger millets from both areas have significant difference because the P value of the sample was P=0.011 and p=0.036 respectively these P values are less than 0.05 at 95% confidence level. Fe’s highest and lowest mean values were recorded in Mankussa mixed finger millet (2.5785 mg/L) and Finoteselam white finger millet (1.412 mg/L), respectively. The result (1.412 to 2.5785 mg/L) of Fe in this study was not agreed with the value (156±18 mg/L to 775.3±42 mg/L) reported by
(Birhanu et al., 2015). According to the permissible limit adopted by
FAO (2010), almost all of the finger millet samples in the two study areas were below the safe limit (3.6 to 6.4 mg/L). The finding of this study is in contrast to recommend the value of
FAO (2010). Because of the lower mean concentration of Mn, the finger millet is not safe for consumption. So, According to
Vijayakumari (2003) finger millet is the richest source of iron. Iron deficiency leads to anemia, which can be overcome by introducing finger millet and other food items that can be rich in iron to our daily diet.
Copper status
When we looked at copper status in the two study areas, the concentration of Copper varied from 0.058 to 0.086 mg/L with a mean value of 0.072 mg/L, 0.053 to 0.064 mg/L with a mean value of 0.0585 mg/L and 0.043 to 0.047 mg/L with a mean value of 0.045 mg/L in black finger millet, mixed finger millet and white finger millet, respectively from Mankussa. while its concentration is also varied from 0.042 to 0.045 mg/L with a mean value of 0.044 mg/L,0.046 to 0.074 mg/L with a mean value of 0.0525 mg/L and 0.052 to 0.053 mg/L with a mean value of 0.0525 mg/L in Finoteselam black, mixed and white finger millet respectively. The trend of the mean concentration of Cu in finger millet varieties among the Mankussa study area was in the order of black finger millet > mixed finger millet >white finger millet. In contrast, in the case of Finoteselam, it was mixed finger millet = white finger millet >Black finger millet. There is a significant difference in the concentrations of Cu in black and white finger millets between both areas (p=0.000) each P values are less than 0.05 at 95% confidence level. While there is no significant difference in the concentration of Cu in mixed finger millet in both areas because the P value of the sample is p=0.103. This P value is greater than 0.05 at a 95% confidence level. The highest and lowest mean values of Cu are recorded in Mankussa black finger millet (0.072 mg/L) and Finoteselam black finger millet (0.0435 mg/L) respectively. The result (0.0435 to 0.072 mg/L) of Cu in this study is not agreed with the safe limit value of (30 mg/L) reported by
FAO (2010). The daily intake amount of Cu differs from person to person based on the developmental levels, sex as well as the standards of the different countries they set. So, According to U.S.A. standards, R.D.I. of Cu is (0.9 mg/day) for matured adults and (1.3 mg/day) for lactating females respectively.
Zinc status
The Zinc concentration varies from 0.336 to 0.561 mg/L with a mean value of 0.449 mg/L,0.521 to 1.077 mg/L with a mean value of 0.799 mg/L and 0.514 to 0.682 mg/L with a mean value of 0.599 mg/L in Mankussa black, mixed and white finger millet samples respectively. while its concentration is varied from 0.410 to 1.139 mg/L with a mean value of 0.774 mg/L,1.152 to 1.365 mg/L with a mean value of 1.259 mg/L and 0.210 to 1.941 mg/L with a mean value of 1.0735 mg/L in Finoteselam black, mixed and white finger millet samples respectively. From the analysis, it was observed that the concentration of Zn with mean values in black and mixed finger millets from both areas have significant differences because the P value of the samples was p=0.021 and P=0.00 respectively each P values are less than 0.05 at 95% confidence level while the concentration of Zn in mixed finger millets from both areas have no significant difference because the P value of the sample was p=0.119)this P value is greater than 0.05 at 95% confidence level. In the present study, the concentration of zinc was found to be high in mixed finger millet from Finoteselam (1.259 mg/L), while a low concentration of zinc was observed in black finger millet from Mankussa (0.4485 mg/L). The result (0.4485 to 1.259 mg/L) of Zn in this study was not agreed with the value (15±3 to 24±3 mg/L) reported by (Birhanu
et al.,2015). The permissible limit of Zn is 27.4 mg/L and the average daily intake of zinc is 7-16.3 mg per day, the recommended dietary allowance is 15 mg per day for men and 12 mg per day for women, almost all of the finger millet samples among the two study areas were found to be below the safe limit. As it falls below the safety limit, finger millet which contains Zn can be consumed in addition to other types of food which include Zn to obtain all of the following importance of Zn. which is essential in wound healing, nervous system, reproductive and immune systems, metabolic function, malaria treatment and as well as the treatment of diabetes Mellitus’s
(Djama et al., 2011).
Lead status
The concentration of Lead is varied from 0.023 to 0.024 mg/L with a mean value of 0.024 mg/L,0.022 to 0.026 mg/L with a mean value of 0.024 mg/L and 0.003 to 0.02 mg/L with a mean value of 0.014 mg/L in Mankussa black, mixed and white finger millet samples respectively. while its concentration is varied from 0.007 to 0.014 mg/L with a mean value of 0.011 mg/L,-0.018 to (-0.001) mg/L with a mean value of -0.014 mg/L and -0.025 to (-0.023) mg/L with a mean value of -0.0245 mg/L in Finoteselam black, mixed and white finger millet samples respectively. The pattern of the mean concentration of Pb in finger millet varieties was in the order of black finger millet = mixed finger millet >White finger millet in the Mankussa study area while in the case of Finoteselam, it was Black finger millet >white finger millet (N.D.)= mixed finger millet (N.D.). From the analysis, it was observed that the concentration of Zn with mean values in black, mixed and white finger millets from both study areas have significant differences because the P value of each sample was p=0.000 which is less than 0.05 at 95% confidence level. In the present study, the concentration of Mean values of Pb was found to be high in Mankussa black and mixed finger millet which is 0.024 mg/L for each, while a low concentration of mean values of Lead was observed in Finoteselam mixed and white finger millet (-0.014 and
-0.0245 mg/L) respectively.