HEAVY METAL PROFILE OF SOME SELECTED VEGETABLES CULTIVATED IN MUBI-NORTH LOCAL GOVERNMENT AREA OF ADAMAWA STATE, NIGERIA - Buba M., Gaila N.M,Isah L. & Umar Y.D
International
Journal of Innovations in Engineering, Science and Technology Volume 5, Number 2, 2016
© 2016 McEvans Publications
HEAVY METAL PROFILE OF
SOME SELECTED VEGETABLES CULTIVATED IN MUBI-NORTH LOCAL GOVERNMENT AREA OF
ADAMAWA STATE, NIGERIA
Buba M.1*,Gaila N.M2,Isah
L.3and Umar Y.D4
1, 2&3Department of Science
Laboratory Technology, Federal Polytechnic Mubi
4Department of Chemical Science
Technology, Federal Polytechnic Mubi
Adamawa
State, Nigeria
ABSTRACT
The
objective of the study was to determine the heavy metal profile of some
selected vegetables cultivated in Mubi North local government area of Adamawa
state. Three replicate samples ofeach of the selected vegetables were randomly
collected from the study area and analyzed for 5 heavy metals namely cadmium
(Cd), copper (Cu),
lead (Pb), zinc (Zn) and iron (Fe) using Atomic Absorption Spectrophotometer
Buck Scientific 210. 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. Comparing the results with the FAO/WHO maximum
permitted level showed thatCu, Zn and Fe were higher than the safe limits in
almost all the samples except in moringa (Cu 0.064 ± 0.003 mg/kg). Consumption
of vegetables cultivated in the study area poses significant health hazard to
the community. Therefore, regular
monitoring of the levels of heavy metals from soil, refuse, effluents and all
other food items is essential to prevent excessive build-up of heavy metals in
the environment.
Key
words:-Heavy metals, Vegetables, Bioaccumulation, Maximum Permitted Level,
INTRODUCTION
Nutrition
experts encourage everyone to consume more vegetables as a rapid and least
means of providing adequate vitamins, minerals and fibers. Regular consumption
of vegetables in diet also provide many health benefits by reducing diseases,
it can also convert fats and carbohydrates into energy (Mercola, 2014). Eating
vegetables as integral part of diet is also one of the most important pathways
for the human body to absorb dietary minerals necessary for healthy development
(Elsevier, 2008). But however, consumption of vegetables contaminated with
environmental pollutants such as toxic heavy metals poses a significant health
risk to the public (Miroslay and Vladmir, 1998;Shagal et al., 2012).
Though,
heavy metals are persistent and cannot be illuminated from the environment,
their availability at high concentration is attributed to high background level
and human activities (Jonathan and Maina, 2009). A number of farms used for
vegetable cultivation are situated along river banks and around residential
areas, these areas also serves as dump sites and channels for the discharge of
house hold effluent into the water ways (Shagal et al., 2012).
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.
MATERIALS AND METHODS
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.
RESULTS AND DISCUSSION
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).
|
Sample
|
Pb (mg/kg)
|
Cu (mg/kg)
|
Zn (mg/kg)
|
Fe (mg/kg)
|
Cd (mg/kg)
|
|
Moringa
|
0.029±0.002
|
0.064±0.003
|
1.741±0.001
|
0.700±0.001
|
˂0.01
|
|
Spinach
|
0.017±0.001
|
0.330±0.001
|
2.134±0.001
|
3.600±0.011
|
˂0.01
|
|
Rosella
|
0.012±0.001
|
0.374±0.007
|
1.520±0.001
|
4.430±0.002
|
˂0.01
|
|
Sesame
|
0.012±0.001
|
0.334±0.001
|
2.476±0.001
|
1.425±0.001
|
˂0.01
|
|
Cabbage
|
0.005±0.001
|
0.110±0.001
|
0.697±0.001
|
1.300±0.001
|
˂0.01
|
|
FAO/WHO permitted level
|
0.10
|
0.10
|
0.10
|
0.10
|
0.002
|
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.
CONCLUSION AND RECOMMENDATIONS
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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