Comparison of Proximate and Heavy Metal Contents of Vegetables Grown with Fresh and Wastewater

Due to insufficient clean water resources wastewater is largely used for irrigation of vegetables in many developing countries, particularly in Pakistan. As a result, vegetables in spite of providing nutrients also accumulate toxic metals and causes health risks. In the present study, comparison of heavy metal contents, using two digestion methods, in fresh and wastewater-irrigated vegetables was appraised by ICP-AES and also their proximate composition was accessed. Samples of wastewater-irrigated vegetables; cauliflower, green pepper, spring onion and brinjal edibles and leaves were collected from wastewater-irrigated and fresh water-irrigated area of Faisalabad. In all the samples large variation of elemental concentration was found however, wastewater grown vegetables showed more accumulation of heavy metals than their respective fresh water irrigated vegetables. The amount of Pb (1.87 mg kg), Fe (1.09 mg kg), Cu (1.01 mg kg), Zn (1.03 mg kg), Cr (0.97 mg kg) showed more accumulation than Mn (0.17 mg kg), Cd (0.08 mg kg) and Ni (0.45 mg kg) both the edible and leaves of investigated vegetables but nearly all metals were found within safe limits. Only Pb (1.87 mg kg) concentration in wastewater-irrigated vegetables exceeded the permissible limits defined by World Health Organization (WHO). Of the two digestion methods nitric acid showed more recovery of metals as compared to dry ash procedure. The leaves of vegetables showed more intake capacity of heavy metals. Continuous accumulation of these metals can pose severe threats to health of people.