Evaluation of heavy metals contamination in some irrigated vegetables from Kano, Nigeria

The content of Pb and Cr in some vegetables (viz lettuce, onion, carrot, tomato, pepper and amaranthus) grown on irrigated farm lands in the vicinity of Sharada industrial waste water drainage basin at Kaba village, Challawa, Kano, Challawa-Yandanko rivers and Thomas Dam, Danbatta, Kano, Nigeria were evaluated. It is situated at 8 o 29` 42” to 8 o 30` 54” E longitude and 11 o 5`18” to 11 o 5` 54” N latitude, also 8 o 30` 18” to 8 o 31` 30”E Longitude and 12 o 17` 6” to 12 o 16` 30”N Latitude. The objectives have been mainly to determine Cr, and Pb in edible parts of these vegetable samples which were frequently consumed by people in Kano and other parts of Nigeria in order to compare the heavy metals contents with the results obtained in analogous studies carried out in relation to the permissible limits specified by WHO/FAO, standards. Samples of vegetable were obtained in the dry season for the year 2018 from upstream and downstream portion of the sample sites. Analyses for the concentration of these heavy metals (Pb and Cr) were conducted by the use of Mass plama-Atomic Emission spectrometry (MP-AES) method. The Data obtained were expressed in terms of descriptive statistics while the figures were presented with mean values of three replicates. The statistical significance was computed using pair samples T-test to test the variation among the heavy metals in the vegetables and sites with a software JMP4 version 14. Results for the study indicated that concentration values of Pb (0.71-8.39 mgkg -1 ) and (Cr 9.58-28.30 mgkg -1 ) were higher than WHO/FAO maximum permissible limits for (Pb 0.3mgkg -1 ) and (Cr 2.3mgkg -1 ). The two way Anova test showed significant differences by farming site, vegetable type and their interaction. Furthermore, the study revealed that some areas of the sample site were more polluted by a particular metal than the other due to the revealing and anthropogenic activities such as the use of untreated industrial and municipal effluents, pesticides, fertilizer supplements for irrigation purposes in the area. Therefore, consumers of these vegetables run the risk of health problems like elevated blood pressure, developmental and neuro-behavioural effects on fetuses, in infants and children, cardiovascular, tubular dysfunction in kidneys and nervous disorders due the elevated concentrations of Cr and Pb in the vegetables. Keywords: Effluent, Heavy metals, Kano, Nigeria, Vegetables