ABSTRACT
This study was undertaken to assay the elemental concentration in
some Irish potatoes and soils from farmlands in an ex-mining area at
Dahwol-vwana village, Jos-south L.G.A, Plateau state, Nigeria. The total
heavy metal concentrations (for Irish potato and soil samples) were
obtained using Atomic Absorption Spectrometer. It was observed from the
soil sample concentration values gotten at the end of the AAS analysis
(Pb, ranges from 0.0445-3.9343ppm; Cd, from 0.0086-0.1200ppm and Zn,
from 0.0751-39.0302ppm) are higher than the concentration values
obtained from control area (Pb- 0.0088ppm, Cd-0.0029ppm and
Zn-0.0101ppm), but lesser than the international threshold values (EU:- Pb-300ppm, Cd-3.0ppm and Zn-300ppm. USA: - Pb-300ppm, Cd-3.0ppm and Zn-250ppm. UK:-
Pb-70ppm, Cd-1.4ppm and Zn-200ppm). While that of Irish potatoes: - Pb,
ranges from 0.0741-1.5042ppm; Cd, from 0.0081-0.0931ppm and Zn, from
0.1038-88.0503ppm). A modified sequential extraction procedure of
Tessier et. al., (1979) was used in separating the total metal
concentrations into four operationally defined fractions (exchangeable
and carbonate, Fe and Mn oxides, organic matter, and residual
fractions). Where it was discovered that the bulk of metals were
partitioned to the residual fraction (Zn- 138.85ppm, Pb-55.59ppm and
Cd-2.5ppm) which implies that the soils of the farmland are not polluted
by any of the metals studied. Pollution indices also as compared with
Banat et. al., (2005) standards, indicated minimal
contamination of the soils matrix with Cd, which had enrichment factor
value of 15.4 and I-geo factor of 4. The bulk partitioning of the metals
onto the residual fraction indicates a lithogenic origin of the heavy
metals, i.e. the heavy metals were directly inherited from the parent
material, and also a low risk of contaminant transfer under normal
cultural practices. However, heavy perturbation of the soil, such as
mining, would lead to significant pollution of soil, and water bodies as
well enhanced Irish potatoes and other plants uptake of the metals,
thereby resulting in a threat of biomagnifications.
CHAPTER ONE
1.0 INTRODUCTION
Tin mining industry which is also the largest producer of columbite
in Jos plateau state started in 1902 (Adegboye, 2012). The mining of
tin has been largely responsible for profound changes in the landscape
and in the social economic structure of study area (Adegboye, 2012).
Limited arable land is experienced in Jos plateau area, according to
(Patterson, 1986) this is due to the high rate of surface mining.
(Scholar, 1979) revealed that mined soils are poorer in agricultural
value compared to adjoining natural land. Crops grown on such mined land
are of low agricultural value, quick maturing and low-nutrient
demanding, such as acha, dauro, maize, millet and Irish potato.
(Calvert, 1990) revealed that the indiscriminate mining on the Jos
plateau, led to many parts of the area being exposed to erosion and
reduces the available arable land for crop production. The volume of
mineral tripped off during mining reduces the nutrient present in the
soil (Adegboye, 2012). Jos South local government area is an extensively
mined area, which was dominated by use of heavy earth – moving
equipment and draglines. As a result, the zone is characterized by deep
excavations and dumping of high over burden, mine ponds, mine tailings
and slurry wash deposits (Olaniyan, 1998; Musa et. al., 2011). According
to (Gyang et. al., 2010), the major problem of the area still remains
the devastated and de-vegetated land and mine spoils; depriving the
inhabitants of fertile farmland. The deep mining which is an excavation
of underlying sand has created mining pits, man-made lakes, pools and
ponds which have great effect on both the people and agricultural
practices. Mining ponds have always been death traps for people and
animals (Davis, 2001).