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Problem of environmental contamination due to toxic metals has become a global concern in most major metropolitan citiesthat are facing problems of water shortage (Miroslay and Vladmir, 1998; Anikwe, and Nwobodo, 2006; Odoh and Adebayo, 2011; Shagalet al., 2012; Alexander et al., 2014; Salawuet al., 2015).The farms under study accumulate varied amount of environmental



International Journal of Innovations in Engineering, Science and Technology   Volume 5, Number 2, 2016


pollution load from atmospheric deposits, anthropogenic inputs, fertilizer application, other agro-allied practices and irrigation of crops with water from non-conventional resources containing household effluents. Vegetables cultivated on the farm absorb such pollutants and eventually passed to man via the food chain. Potentially toxic heavy metals entering the ecosystem may lead to geo-accumulation and bio-accumulation in the environment as well as human body with the attendant manifestation of chronic diseases that afflict the human population (Lokeshwari and Chandrappa, 2006; Salawuet al., 2015).

          Heavy metals like nickel (Ni), iron (Fe), copper (Cu), zinc (Zn) and other trace elements are important for proper functions of biological systems, however, their deficiency or excess could lead to a number of disorders. Therefore, a better understanding of heavy metal sources, their accumulation in the soil and the effect of their presence in water and soil on plants system seem to be of great importance for researches on risk assessment (Rajesh et al., 2004).

A number of studies have shown that sewage water irrigation has elevated the levels of toxic heavy metals such as nickel (Ni), zinc (Zn), cobalt (Co), manganese (Mn), and iron (Fe) in the ecosystem. (Mapandaet al., 2005; Anikwe, and Nwobodo, 2006; Odoh and Adebayo, 2011; Shagalet al., 2012; Alexander et al., 2014; Salawuet al., 2015).

This research work is therefore aimed at assessing the contamination levels of some selected vegetables cultivated in the study area with some toxic heavy metals in other to ascertain their pollution load.This will in no thought provide us with the opportunity to proffer rational advice to the community with respect to the vegetables they consumed.



The Study Area

Mubi north region geographically is located in the North - western part of Adamawa state in the north-eastern part of Nigeria. Its geographical coordinates are 10°16’ North13°16’ East of the equator and10.267oNorth 13.267o East of the Greenwich meridian with an estimated population of about 151,515 according to 2006 census. Mubi is occupied by diverse ethnic groups but the Fali, Gude, and Njanyi are the majority.


Sample Collection/ Preparation

Sampling was performed by random collection of the vegetable sample from various sampling points identified in the study area according to the FAO/WHO recommendation (FAO/WHO, 1986). Three replicate samples about 1kg of the vegetable was collected from each sampling point. All the samples were packed in a well labeled plastic bag and transported to the laboratory.

Samples were collected from farms in Shuware, Wurogude and Hurida, These farms are located on the banks of river Yadzaram. The samples were taken among commodities considered of high consumption rate and commonly cultivated at the study area. The vegetable sample was washed to remove the soil particles and afterwards it was dried under shade for 72 hours. The dried samples were then pulverized in a mortar, sieved through a 2mm sieve and stored at room temperature before analysis.


Plant Digestion

One gram of prepared sample was weighed into 250cm³ conical flask, the sample was digested according to the United State Environmental Protection Agency [USEPA] 3050 method as reported by Odoh and Kolawole, 2011;Salawuet al., 2015). 10cm³of HNO3 was added to the mixture and heated for 30 min in a water bath at 100°C. The digest was allowed to cool and another 5cm³ of HNO3 was again added and continuously heated for 1hr at 100°C. The volume of the digest was reduced by boiling on the water bath and this was allowed to cool. 5 cm3 of distilled water was added when effervescence subsided, 10 cm3 of H2O2 (60%) was also added and the heating continued for another



Heavy Metal Profile of Some Selected Vegetables Cultivated in     Buba M., Gaila N.M ,Isah L. and

Mubi-North Local Government Area of Adamawa State, Nigeria     Umar Y.D.


30 min. The final digest was allowed to cool and filtered. The final volume of digest was made up to 50 cm3 with distilled water and was analyzed for the studied heavy metals by AAS Buck Scientific 210.



Table 1: showed the summary of the distribution and concentration of some heavy metals in the selected vegetables.


Table 1: Concentration of the heavy metals and their Maximum permitted level (mg/kg).


Pb (mg/kg)

Cu (mg/kg)

Zn (mg/kg)

Fe (mg/kg)

Cd (mg/kg)































FAO/WHO  permitted level






All values represent mean ± standard deviation of triplicate determination, FAO/WHO 1995. 


Analysis of heavy metal profile in some selected vegetables cultivated in Mubi North LGA was conducted using AAS Buck Scientific 210,the results obtained is as shown in table 1 above. The results revealed the presence of heavy metals at varying concentrations on all the samples analyzed except cadmium which was found to be below the detection limit of the instrument.

Concentration of Pb in the samples analyzed ranges from 0.029±0.002 mg/kg in moringa to 0.005±0.001 mg/kg in cabbage, Cu showed highest concentration of 0.374±0.007 mg/kg in rosella and the lowest concentration of 0.064 ± 0.003 mg/kg in moringa, Zn showed maximum concentration of 2.476 ± 0.001 mg/kg in sesame and minimum concentration of 0.697 ± 0.001 mg/kg in cabbage, highest level of Fe was detected in rosella 4.430 ± 0.002 mg/kg and the lowest was detected in moringa 0.700 ± 0.001 mg/kg.

Though, certain heavy metals like Cu, Fe, Zn, Co and Mn at low concentration are essential elements for enzymatic activities and many biological processes, but at higher concentrations, they constitute a serious health hazard (Jonathan and Maina, 2009).

Comparing the results with the FAO/WHO maximum permitted level as shown in table 1, Cu, Zn and Fe were found to be higher than the safe limits in almost all the samples analyzed except in moringa ( Cu 0.064 ± 0.003 mg/kg).

 Accumulation of heavy metals in the analyzed vegetable samples may be attributed to some anthropogenic activities such as fertilizer application, discharge of household waste water into water ways and to some extent dumping of refuse close to agricultural areas as stated earlier. Several research reports have shown that municipal waste containing metals, ceramics, food waste, glass and paper increases the availability of heavy metals which can persist in soil at environmentally hazardous level (Odoh and Adebayo, 2011). According to Mohammed et al., (2014) sewage water irrigation increases the accumulation of certain heavy metals such as Pb, Zn, Fe and Mg in agricultural soil. Anikwe and Nwobodo, (2006) reported elevated level of Pb, Cu, Zn and Fe from there long term studies of the effect of municipal waste disposal on soil properties and productivity of sites used for urban agriculture in Abakaliki, South Eastern part of Nigeria. Akan et al., (2013) reported level of Cr, Mn, Fe, Ni, Pb, Zn Cd and Cu higher than the FAO/WHO in all the vegetable samples analyzed from Biu Local Government Area, Borno state North Eastern Nigeria. The result of this analysis also corroborate with the work of Shagal et al., (2012) in their analysis of Bioaccumulation of trace metals concentration in some vegetables grown near refuse and effluent dumpsites along Rumude-Doubeli bye-pass in Yola North, Adamawa state.




International Journal of Innovations in Engineering, Science and Technology   Volume 5, Number 2, 2016


Critical perusal of available literature reveals a growing interest in the investigation of heavy metals in plants and environmental samples, but to the best of our knowledge, no investigation, monitoring or regular survey assessment has been reported on the heavy metal profile of the vegetables cultivated in Mubi North local government area of Adamawa state. Therefore, the result obtained in this study provides a baseline data for the prevalence of heavy metals in vegetables cultivated in the study area.



The result obtained showed that concentration levels of the majority of the heavy metals in the samples were higher than the permitted levels for consumption, excessive consumption of these vegetables may warrant bio-accumulation of the heavy metals in the animal tissue via the food chain and this may constitute a serious adverse health effect.

We therefore recommend a regular monitoring of these toxic metals in vegetables and other food materials in other to avoid their excessive build-up in the environment. We also recommend that relevant agencies should provide the famers with soft loan and boreholes for irrigation farming far away from dumpsites and household effluents.



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Heavy Metal Profile of Some Selected Vegetables Cultivated in     Buba M., Gaila N.M ,Isah L. and

Mubi-North Local Government Area of Adamawa State, Nigeria     Umar Y.D.


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