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Authors: Khan, Anwarzeb
Keywords: Applied Sciences
Agriculture & related technologies
Issue Date: 2016
Abstract: Heavy metals are considered as global environmental pollutants that are present everywhere in the environment. Urbanization, high population growth, construction and development and high demand for food are the major factors resulting in discharge of heavy metals to environment which ultimately lead to food chain contamination. Vegetables are the main source of diet and contamination of these vital sources may severely affect human health. Toxic metals have both direct and indirect effects on human health, while the effect on nutritional parameters is one of the indirect effects of heavy metals contamination. This research work is divided into different parts and several experiments were conducted to achieve the objectives. The first study was conducted to evaluate the effects of heavy metals (cadmium (Cd), lead (Pb) and Cd-Pb mix) on bioaccumulation of different nutrients. Three plant species including potato (Solanum tuberosum L.), tomato (lycopersicon esculentum) and lettuce (Lactuca sativa L.) were grown in pots containing soil contaminated with Cd, Pb and Cd-Pb mix at four different levels. The edible portions of each plant were analyzed for Cd, Pb and different macro- and micro- nutrients including protein, vitamin C, nitrogen (N), phosphorous (P), potassium (K), iron (Fe), manganese (Mn), calcium (Ca) and magnesium (Mg). Results indicated significant variations in selected elemental concentrations in all the three plants grown in different treatments. The projected daily dietary intake values of selected metals were significant (P<0.001) for Fe, Mn, Ca and Mg but not significant for protein, vitamin C, N and P. The elemental contribution to Recommended Dietary Allowance (RDA) was significant for Mn. Similarly, Fe and Mg also showed substantial contribution to RDA, while Ca, N, P, K, protein and vitamin C showed the minimal contribution for different age groups. This study suggests that vegetables cultivated on Cd and Pb contaminated soil may significantly affect their quality, and 2 the consumption of such vegetables may result in substantial negative effects on nutritional composition of the consumer body. Long term and continuous use of contaminated vegetables may result in malnutrition. The second study was focused on arsenic (As), being a toxic metalloid, ubiquitously present in the environment and severely affects the health of plants and humans. Pot experiments were also conducted to evaluate the toxic effects of As on plant nutritional parameters. Three nutritious plant species such as potato, tomato and lettuce were selected to investigate the possible toxic impacts on macro- and micro- nutrients concentrations. ‘As’ was added to the soil at three different concentrations with and without Cd and Pb. The edible parts of each plant were analyzed for As and essential macro- (vitamin C, protein, N, P, K) and micro- nutrients (Ca, Mg, Fe and Mn). The concentrations of macro- and micro- nutrients showed significant variation (P<0.001) in contaminated soil than in the control. ‘As’ amendments significantly (p<0.01) increased the concentrations of Ca, N and protein, while P and K concentrations were decreased. As concentrations were both negatively and positively correlated with Mn, Mg and vitamin C depended upon the type of vegetable and the contamination level. The values of contribution to RDA through consumption of contaminated vegetables were significant (P<0.01) for Mn, less significant (p=0.05) for Fe, Mg, P and K, while non-significant for Ca. N and protein for different age groups. It is concluded that the consumption of As contaminated vegetables may have both direct and indirect effects on human health. As contamination severely affected the quality and nutritional balance in contaminated vegetables and their consumption may result in to severe malnutrition. The third study was conducted to evaluate the potential effects of As, Cd and Pb on bioavailability, uptake and bioaccumulation of chromium (Cr), copper (Cu), nickel (Ni) and zinc 3 (Zn) by lettuce, potato and tomato. The concentrations of selected metals were determined using Atomic Absorption Spectrophotometer. The results indicated that plants cultivated in contaminated soil observed substantial changes in essential and trace element concentrations and the effects were more significant with increasing concentration of heavy metals in the soil. Both synergistic and antagonistic effects were observed depending upon type of vegetables, concentration of pollutants in the soil and metal mixture used. Among the selected vegetables the effects were more prominent on lettuce. The projected daily dietary intake of Cr, Ni and Zn was higher for vegetables grown in metals contaminated soil than in control. The contribution to RDA was significant for Cu and Ni and less significant for Zn, although great variation was observed in RDA for different treatment levels. Consumption of metals contaminated vegetables have provided 400% Ni RDA and >50% of Cu RDA for selected vegetables. The results indicate that the food quality and elemental composition of vegetables cultivated in metals soil was significantly affected, and their consumption may severely affect human health. From the findings of these studies, it is suggested that consumption of heavy metals contaminated vegetables have substantial effects on plant quality and nutritional balance that ultimately lead to malnutrition in consuming population.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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