Study of Contamination of Vegetables and Soils by Heavy Metals in Khartoum State on 2016

Abstract

The study was focused on some heavy metals which are Mn, Zn, Cu and Pb that are known as the most toxic and contaminate to human health. In this study XRF and AAS techniques were used to determine concentrations of Mn, Zn, Cu and Pb in soils and vegetables (Onion, Jew Mallow, Watercress, Marrow and Cucumber). The mean value of concentrations of Copper in this vegetables by XRF technique (ppm), was found to be in Onion (11.32), Jew Mallow (6.18), Watercress (5.90), Marrow (7.05) and Cucumber (7.53), while the mean value of concentrations of Copper in soils (20.48), (19.01), (21.30), (19.40) and (19.56) respectively. The mean value of concentrations of Copper in this vegetables by AAS technique (µg/g), was found to be in Onion (19.04), Jew Mallow (10.89), Watercress (9.95), Marrow (11.44) and Cucumber (9.89), while the mean value of concentrations of Copper in soils (35.28), (52.15), (51.32), (43.49) and (41.15) respectively. The mean value of concentrations of Lead in this vegetables by XRF technique (ppm), was founds the concentrations to be in onion (1.43), Jew Mallow (0.87), Watercress (0.84), Marrow (0.98) and Cucumber (0.97), while the mean value of concentrations of Manganese in soils (15.13), (14.30), (13.36), (16.27) and (13.58) respectively. However the AAS technique can not at all detect existence of Lead. The mean value of concentrations of Zinc in this vegetables by XRF technique (ppm), was found to be in Onion (13.33), Jew Mallow (7.61), Watercress (13.58), Marrow (13.58) and Cucumber (15.67), while the mean value of concentrations of Zinc in soils (26.63), (22.34), (23.71), (22.93) and (24.40) respectively. The mean value of concentrations of Zinc in this vegetables by AAS technique (µg/g), was found to be in Onion (13.33), Jew Mallow (23.92), Watercress (22.63), Marrow (30.56) and Cucumber (28.80), while the mean value of concentrations of Zinc in soils (49.18), (76.01), (72.12), (62.02) and (57.96) respectively. The mean value of concentrations of manganese in this vegetables by XRF technique (ppm), was found to be in onion (41.67), Jew Mallow (41.72), Watercress (51.06), Marrow (17.70) and Cucumber (Non-Detect), while the mean value of concentrations of Manganese in soils (350.59), (432.14), (423.75), (421.50) and (396.62) respectively. The mean value of concentrations of manganese in this vegetables by AAS technique (µg/g), was found to be in onion (37.36), Jew Mallow (88.25), Watercress (89.84), Marrow (12.74) and Cucumber (10.9), while the mean value of concentrations of Manganese in soils (780.01), (106.09), (1012.90), (854.94) and (788.49) respectively. It is very interesting to note that the concentrations of Copper, Zinc and Manganese found by AAS technique is higher than that of XRF technique, this may results from the fact that light element emits more visible photons than x-ray photons. It is also very striking to note that XRF technique gives higher concentrations for Lead compared to AAS technique, this means that XRF spectrometer is better for Lead detection. This sensitivity of XRF spectrometer may be attributed to fact that heavy elements such as lead emit x-ray energetic photons more than light visible ones, since the photon energy is proportional to the square of the atomic number.