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 American Journal of  
Food Science and Technology (AJFST)

Heavy Metal Concentration of  Okra (Abelmoschus Esculentus) Grown on Dumpsite Soil in 
Benin City, Nigeria

Godspower Oke Omokaro1*, Mary Ganpatei Ojujoh2, Ikioukenigha Michael3, Zipporah Simiyu Nafula1

Volume 2 Issue 2, Year 2023
ISSN: 2834-0086 (Online)

DOI: https://doi.org/10.54536/ajfst.v2i2.2233
https://journals.e-palli.com/home/index.php/ajfst

Article Information ABSTRACT

Received: October 28, 2023

Accepted: November 30 2023

Published: December 04, 2023

The study investigates the concentrations of  heavy metals in Okra (Abelmoschus esculentus) 
planted in dumpsite soil obtained from the University of  Benin and Ekosodin in Benin City. 
Soil samples were collected before and after planting and analyzed for pH, total nitrogen 
(N), total organic carbon (C), phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and 
heavy metal concentrations (Cu, Pb, Cd, and Cr). The study reveals variations in soil acidity 
levels across different locations before and after planting. In Table 1, soil pH was moderately 
acidic in Farmland (5.61), neutral in Market (6.79) and Residential (6.76) areas, and slightly 
acidic in Faculties (6.14). In Table 2, after planting, the pH remained moderately acidic 
in Market (5.68) and Residential (5.80), while becoming strongly acidic in Farmland (5.42) 
and Faculties (5.36). Total N and P decreased in most dumpsites after planting, while total 
organic carbon increased. Fe, Zn, and Mn concentration varied between dumpsites and after 
planting stages. Particle size distribution remained predominantly sandy across dumpsites 
and planting stages. The study suggests that Okra plants cultivated in various dumpsite soils 
showed no toxic levels for the selected heavy metals, with concentrations generally falling 
within acceptable limits for vegetable consumption. The copper concentration highest uptake 
observed in Okra plants from Residential Land (36.0 mg/kg) and the lowest in Farmland 
(23.3 mg/kg). Lead (Pb) uptake varied across dumpsites: Market (0.15 mg/kg), Farmland 
(0.10 mg/kg), Residential Land (0.12 mg/kg), and Faculties (0.06 mg/kg). Cadmium (Cd) 
uptake was observed at Market dumpsites (0.05 mg/kg), Farmland (0.02 mg/kg), Residential 
Area (0.01 mg/kg), and Faculties (0.04 mg/kg). Heavy metal concentrations in the soil and 
Okra plants were generally below the permissible limits set by the Department of  Petroleum 
Resources (DPR) for soil and World Health Organization (WHO) for vegetables intended 
for human consumption.

Keywords

Heavy Metals, Okra, 
Dumpsites, Soil Properties, Soil 
Analysis

1 Institute of  Ecology, Peoples Friendship University of  Russia, Moscow, Russia
2 Department of  Soil Science and Land Management, University of  Benin, Ugbowo, Benin City, Edo State, Nigeria
3 Department of  Geography and Regional Planning, Igbinedion University, Okada, Edo State, Nigeria
* Corresponding author’s e-mail: omokaro.kelly@gmail.com

INTRODUCTION
Earth is very good at recycling waste, but when the 
amount of  wastes generated is far more than the earth 
can cope with; it poses a big threat to lives, a phenomenon 
called pollution. Pollution occurs at different levels and 
affects all lives ranging from plants, animals to man 
(Skye, 2006). Nearly all human activities generate waste 
and the way, in which this is handled, stored, collected, 
and disposed of, can pose risks to the environment and 
to public health (Zhu et al., 2008). The decay of  these 
solid wastes releases substances that can affect the soil 
nutrients content, increase the concentration of  heavy 
metals in the soil, altering the natural balance of  nutrients 
available for plant growth and development thereby 
affecting species diversity and agricultural productions. 
Contamination of  the environment by heavy metals with 
their potential effects on human health, agriculture and 
natural ecosystems has become a subject of  worldwide 
concern. Hazards of  heavy metal contamination have 
been reported (Chan et al, 1999). Wastes found in the 
dump sites come from municipal, domestic and industrial 
sources and may contain heavy metals (Babatunde et al., 
2013). The increase in population coupled with rural-
urban drift has increased the quantity of  wastes generated 
in the urban areas and the developing countries are faced 

with not only the challenge of  collecting the wastes but 
how and where to dispose it without causing further 
environmental hazard (Oguche, 2013). 
Heavy metal contamination of  the environment arises at 
all stages of  metal utilization from the mining of  metallic 
ores to the disposal of  domestic and industrial wastes. 
Human beings, animals, vegetation and soil are the ultimate 
receipt of  heavy metals in the environment. However, 
lack of  effective waste management in overpopulated 
cities can have substantial negative effects that include 
fetid water ways emitting stench from sewage, spreading 
diseases and harbouring vehicles that spew treaded 
exhaust into dust filled air. At a time when environmental 
quality and food production are of  major concern, a 
better understanding of  the behaviour of  elements in the 
air-soil-plant system seems to be particularly important. 
The presence of  lead for example has been reported in 
the bark of  trees, in some fauna (Ogbonda 1992) and 
in man (Okokoyo and Rim- Rukeh, 2004). Heavy metal 
composition in different food types of  various countries 
have been studied (Rashed, 2001). However, such data 
are not readily available for most foods of  less-developed 
countries such as Nigeria (Onianwa et al, 1999). Okra 
which grows in wide range of  soil is known for its nutrient 
supply and as a very common vegetable in tropical 



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Am. J. Food. Sci. Technol. 2(2) 65-73, 2023

region most especially in the Southern part of  Nigeria. 
It is widely cultivated and recognized as a fast-growing 
vegetable; however, this study focuses on the heavy metal 
content of  Okro (Abelmoschus esculentus) grown on soil of  
dumpsite obtained in Benin City. The specific objective 
was to ascertain heavy metal concentration of  okra raised 
on dumpsite soil.

LITERATURE REVIEW
OKRA (Abelmoschus esculentus) (L) Moench Origin and 
Geographic Distribution
Okra Ablemoschus esculentus L. (Moench), a member of  
family Malvaceae, is widely cultivated vegetable of  high 
nutritional values in human diet (Dikwahal et al., 2006; 
Jonathan et al., 2011). It is a good source of  protein, 
carbohydrate, vitamin C and calcium (Kahlon et al., 2007; 
Arapitsas, 2008). The leaves, stems and fruits are also 
economically important in paper and pharmaceutical 
industries (Dilruba et al., 2009). The plant is cultivated 
in tropical, subtropical and warm temperate regions 
around the world (NRC, 2006). Okra can be grown on 
wide range of  soils, but well drained fertile soils with 
adequate organic matter result to high yield (Akinyele et 
al., 2007). The crop is widely cultivated throughout the 
year in the tropics. Okra is a nutritious vegetable which 
plays important role to meet the demand of  vegetable are 
scanty in the market (Ahmed et al., 1995).

Botany of  Okra
Okra belongs to the family malvaceae and genus 
Abelmoschus (Schippers, 2000). It used to be classified 
within the genus Hibiscus, (Farooq et al., 2010) from which 
it has been separated. Schippers (2000) reported that the 
genus Abelmoschus has 5-toothed calyx (sepal) which splits 
longitudinally along a single suture at flowering. After 
flowering, the whole bloom consists of  a calyx, petal, 
and staminal column, which are fused at the base, drops 
together, leaving the ovary and the epicalyx segment 
behind (Schippers, 2000). NRC, (2006) reported that 
Abelmoschus is now considered to consist of  nine or ten 
species. Five species are in Africa, three are indigenous 
and two were introduced from Asia in the distant past.  A. 
ficulneus L. is found in tropical lowland areas with a long 
dry season, such as parts of  the Sahel (Mali, Chad, Sudan) 
and East Africa (Ethiopia, Somalia, Tanzania, Uganda, 
Madagascar), but more so in South and South-East Asia 
and in Australia (NRC, 2006). Schippers, (2000) reported 
that this specie can be strongly branched and short, such 
as in Sudan, or tall with few branches, reaching 2 m in 
height, such as plants found in the Selous Game Reserve 
in Southern Tanzania. It has pink flowers of  about 2–4 
cm with a distinctly dark centre. Its hairy fruit, often with 
a round rather than a pointed apex, are best recognized by 
its divided, pear-shaped leaves. It is a wild species and one 
of  the two ancestors of  the common okra (Schippers, 
2000).

Varieties of  Okra
Most plant populations consist of  landraces or remnants 

of  earlier introduced varieties such as Clemson spineless 
from the US (NRC, 2006). These can be seen in East and 
Southern Africa and remain the most popular cultivars in 
the forest zone of  West Africa. They usually take about 
10 weeks from sowing to produce the first fruit (early 
maturing) but are less mucilaginous than the West African 
okra or common okra (NRC, 2006). The Southern Asia 
cultivar Pusasawani has been introduced to East Africa 
where it has become very popular. Other varieties that 
have been introduced to Africa are Green emerald 
and Dwarf  long green (NRC, 2006). NRC, (2006) also 
reported that only minimal research has been undertaken 
on truly African varieties.  In Sudan, there are several 
varieties available from local seed houses which include 
a spiny one called Khartoumia. Other local varieties 
include Momtaza, Kerrari, Kassala, Medani, Sinnar and 
others which are named after the location where they 
are grown. The same applies to Kariba from Zambia. 
Rechiindia (early maturing dwarf  variety) and Derererefu 
(late-maturing tall variety) are widespread (Schippers, 
2000).

Soil and Environmental Requirements of  Okra
According to Schippers (2000) and Remison (2005), 
a well-drained sandy loam with pH of  6.0–6.8 is ideal 
for growing okra. It does not grow well on clay soils, 
in swampy or areas or on acid soils. Okra is moderately 
tolerant to salinity, particularly A. esculentus, which 
originated in a semi-arid environment where salt is often 
encountered at the soil surface, and more so than A. 
caillei which is found in the humid forest belt (Schippers, 
2000; Remison, 2005). The crop does not grow well when 
temperatures drop below 20°C, especially A. esculentus, 
which likes plenty of  sunshine and does not do well in the 
shade. It can tolerate high temperatures, but heat coupled 
with low humidity slows down growth considerably 
(Schippers, 2000).

Nutritional/Medicinal Value of  Okra
The nutritive value of  okra/100 g edible portion includes 
energy, 35Kcal; moisture, 89.6 g; carbohydrate, 6.4 g; 
protein, 1.9 g; fat, 1.2 g; mineral, 0.7 g; phosphorus, 
56.0 mg; sodium, 6.9 mg; sulphur, 30.0 mg; calcium, 
66.0 mg; iron, 0.35g; potassium, 103 mg; copper, 0.19 
mg; riboflavin, 0.01 mg; thiamine 0.07 mg; niacin 0.06 
mg; vitamin C 13.1 mg; oxalic acid, 8.0 mg (Goppalan 
et al, 2007).  It medicinal value has also been reported in 
curing ulcers and relief  from hemorrhoids (Kumar et al., 
2010). Unspecified parts of  the plant were reported in 
1898 to possess diuretic properties (Kumar et al., 2010) 
this is referenced in numerous sources associated with 
herbal and traditional medicine. Okra has found medical 
application as a plasma replacement or blood volume 
expander (Lengsfeld et al., 2004). It is also good source of  
iodine which is useful in the treatment of  simple goiter 
and source of  other medically useful compound (Lui 
et al., 2005).  It is very useful genitor-urinary disorders, 
spermatorrhoea and chronic dysentery (Lui et al., 2005). 
Tests conducted in China suggest that an alcohol extract 



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of  okra leaves can eliminate oxygen free radicals, alleviate 
renal tubular interstitial diseases, reduce protein urea, and 
improve renal function (Kumar, 2009).

Dumpsite
Dumpsite is an old traditional method of  waste disposal 
similar to landfill method of  waste management. 
Dumpsites are often established in disused quarries, 
mining or excavated pits away from residential areas 
(Abduls-Salam, 2009). Designated government agency, 
corporate bodies and some individuals collect wastes 
routinely into these dumpsites (Abduls-Salam, 2009).
Wastes found in the dump sites come from municipal, 
domestic and industrial sources and may contain heavy 
metals (Babatunde et al., 2013).The management of  
these wastes generated has become a serious problem 
because; little efforts have been made in order to improve 
on the wastes collection and disposal facilities. This is 
not without their consequence such as deteriorating 
soil quality (Obute et al., 2010). In Benin City and in 
Nigeria in general, modern landfill facilities are not 
found in these municipal dumpsites, hence the sorting-
out of  solid wastes into degradable, non-degradable 
and recyclable precious materials cannot be achieved. 
Poor management of  dumpsites could create a number 
of  adverse environmental impacts, including wind-blow 
litter, attraction of  mice and pollutants such as leachate, 
which can pollute underground soil bed, and / or aquifer 
(Abduls-Salam, 2009). Landfill gas mostly composed 
of  methane and carbon (IV) oxide is produced through 
biodegradation of  such waste (Abduls-Salam, 2009). 
Leachate from dumpsites is of  particular interest when 
it contains potentially toxic heavy metals. These metals 
are known to bio accumulate in soil and have long 
persistence time through interaction with soil component 
and consequently enter food chain through plants or 
animals (Dosumu, 2003). 
Household and industrial garbage may contain toxic 
materials such as lead, cadmium, mercury, manganese 
from batteries, insect sprays, nail, polish, cleaners, plastics 
polyethylene or PVC (polyvinyl chloride) made bottles 
and other assorted products (Abduls-Salam, 2009). Soil 
microorganisms can degrade organic contaminants, 
while metals need immobilization or physical removal 
because metals at higher concentrations are toxic and 
can cause oxidative stress by formation of  free radicals 
(Henry, 2000) and thus may render the land unsuitable 
for plant growth and destroy the biodiversity. When waste 
is dumped on land, soil microorganisms including fungi 
and bacteria, readily colonize the waste carrying out the 
degradation and transformation of  degradable (organic) 
materials in the waste (Stainer et al., 1989). Microorganisms 
in waste dump use the waste constituents as nutrients, 
thus detoxifying the materials as their digestive processes’ 
breakdown complex organic molecules into simpler 
fewer toxic molecules (Gimmler et al., 2002). However, 
municipal solid wastes are known to contain large amount 
of  persistent organic pollutants (Minh et al., 2006). The 

concentrations and transformations of  heavy metals in 
solid municipal wastes lead to accumulation in the food 
web (Gimmler et al., 2002).

Use of  Dumpsite as Farmland
The use of  dumpsites as farmland is a common practice 
in urban and sub-urban centers in Nigeria because 
decayed and composted wastes enhance soil fertility 
(Ogunyemi et al., 2003). These wastes often contain heavy 
metals in various forms and at different contamination 
levels. Some heavy metals like As, Cd, Hg and Pb are 
particularly hazardous to plants, animals, and humans 
(Alloway and Ayres, 1997). Municipal waste contains such 
heavy metals as As, Cd, Co, Cu, Fe, Hg, Mn, Pb, Ni, and 
Zn which end up in the sink when they are leached out 
from the dumpsites. Soil is a vital resource for sustaining 
two human needs of  quality food supply and quality 
environment. Plants grown on a land polluted with 
municipal, domestic or a land polluted with municipal, 
domestic, or industrial wastes can absorb heavy metals 
inform of  mobile ions present in the soil through their 
roots or through foliar absorption. These absorbed metals 
get bioacumulated in the roots, stems, fruits, grains and 
leaves of  plants (Fatoki, 2000). Heavy metals like iron, tin, 
copper, manganese, and vanadium occur naturally in the 
environment and could serve as plant nutrients depending 
on their concentrations. Mercury, lead, cadmium, silver, 
chromium, and many others that are indirectly distributed 
because of  human activities could be very toxic even at 
low concentrations. These metals are non-biodegradable 
and can undergo global ecological circles (Adekola et al., 
2008).

Heavy Metals
Heavy metals are chemical elements grouped under 
the generic name of  micro-elements that exhibit metal 
properties with relatively high atomic weight, density and 
with a specific gravity of  5.0g/cm3 or greater (Ademoroti, 
1996). Heavy metals occur naturally in the ecosystem 
with large variations in concentrations. In modern times, 
anthropogenic sources of  heavy metals, i.e., pollution 
from the activities of  humans, have introduced some of  
these heavy metals into the ecosystem (Oluyemi et al., 
2008). The presence of  heavy metals in the environment 
is of  great ecological significance due to their toxicity at 
certain concentrations, translocation through food chains 
and non-biodegradability which is responsible for their 
accumulation in the biosphere (Awofolu, 2005). The 
presence of  very high contents of  heavy metals in the 
soil causes “heavy metal soil pollution”. This indicates 
that the content of  these elements in the soil are higher 
than the maximum concentration that has a beneficial or 
harmless effect on vegetation in some areas. The negative 
effect of  heavy metals depends on the concentration as 
well as on series of  physical and chemical soil specific 
characteristics, such as texture, organic matter content, 
pH, redox potentials, and hydraulic conductivity etc. 
(Lacatusu, 2001). Concern has been expressed regarding 



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the accumulation of  toxic heavy metal such as Cadmium 
(Cd), Zinc (Zn), Copper (Cu) and lead (Pb) and their 
potential effect on human health, agriculture and natural 
ecosystems (Adefemi and Awokunmi, 2009). The 
accumulation of  the toxic heavy metal in a particular 
domestic dumpsite is because of  indiscriminate dumping 
of  domestic waste, such as decayed food item, rotten 
eggs, animal slain and bones, useless tin, cans in which 
heavy metals are found to be mostly trapped.

Heavy Metal on Soil Due to Wastewater from Dumpsite
Streck and Richter (1997) reported that movement of  
heavy metals in soils from dumpsite with wastewater 
is very slow and more than 90% of  Cd, Ni, and Pb 
accumulated in the 10–15 cm soil depth. Wastewaters 
often contain significant concentrations of  organic and 
inorganic nutrients for example nitrogen, phosphate, 
(Alshammary and Qian, 2008) micronutrients and heavy 
metals (Mojiri and Amirossadat, 2011). Waste waters 
carry appreciable amounts of  toxic heavy metals which 
vary from city to city. Important sources of  heavy metals 
in wastewater are urban and industrial effluents. Heavy 
metals are extremely persistent in the environment; 
they are non-biodegradable and non-thermodegradable 
and thus readily accumulate to toxic levels. Long-term 
flow of  waste waters from dumpsite on lands often 
results in the build-up of  the elevated levels of  heavy 
metals in soils (Tabari et al., 2008). Metal absorption and 
accumulation in a plant depends on many soil factors, 
such as- pH, EC, clay content, organic matter content 
and physical and mechanical characteristics of  soil. Plant 
takes heavy metals from soil through different reactions 
such as: absorption, ionic exchange, redox reactions, etc. 
(Zabalawy et al., 2015).

MATERIAL AND METHODS
Study Area
This study will be carried out at the Screen House of  
the Department of  Soil Science and Land Management, 
University of  Benin, Benin City in Edo State, Nigeria. 
The area lies from 6° 23’ 53” - 6° 24’ 40” N and 5° 37’ 
24” - 5° 37’ 34” E. It is the segment of  the coastal plain 
sand commonly referred to as acid sand of  Nigeria. The 
soil type in this area is Ultisol (Rhodic paleudult). This 
region is within the rain forest zone of  Nigeria. It has an 
annual average temperature of  about 27°C and an annual 
rainfall of  about 2000 mm. The study area experiences 
two major seasons namely the rainy season which lasts 
between March to October and the dry season lasts from 
November to February (Ogeh and Ogwurike, 2006).

Sample Collection and Planting
Twelve (12) dumpsites were carefully selected in 
University of  Benin, Benin City, Edo State. The dumpsites 
were: three (3) each from marketplaces, Residential 
places, learning centers and farmland. Soils sample from 
the market and residential places were collected from 
Ekosodin dumpsites in Benin City. From Farmland: The 

Faculty of  Agriculture Experimental Farm, Forestry and 
Wildlife and Fisheries dumpsites were selected. Learning 
centers: The Faculty of  Agriculture, Faculty of  Law 
and Faculty of  Art Dumpsites were used. Collected 
soil samples were filled into plastic buckets and placed 
in the screen house of  the Department of  Soil Science 
and Land Management, University of  Benin, Benin City. 
Seeds of  Abelmoschus esculentus were planted at a depth of  
2cm and 3 seed per bucket. Soil samples were taken from 
the buckets before and after planting, soil samples from 
the same Land use were bucked to make a composite 
sample.

Soil Laboratory Analysis
The analysis of  the soil physical and chemical properties 
was carried out at the Faculty of  Agriculture main 
laboratory. Standard laboratory procedures were used in 
the analysis of  the selected physiochemical characteristics 
selected in this study. The particle size distribution was 
determined by the hydrometer method (Boyoucos, 1951) 
as modified by Gee and Bauder (1986). The pH of  the 
air-dried soil was determined using a glass electrode pH 
meter at ratio 1:1 and (20g soil to 20ml distilled water) 
and in 1N KCl solution at a ratio of  1:2 soil to water 
suspension according to Mclean, (1982) method. Calcium 
and magnesium were determined volumetrically by the 
EDTA titration procedure, and Potassium was determined 
from the filtrate by flame photometry described by Black 
(1965). Organic carbon was determined by the chromic 
acid wet oxidation procedure of  Walkley and Black as 
described by (Black 1965). The available phosphorus in 
the soil samples was determined using Bray and Kurtz 
(1945) solution. The total nitrogen in the filtrate was 
determined by the alkaline phenate procedure of  Fiore 
and O’ Brien (1962).

Analysis for Micro-nutrients and Heavy Metals
1g of  the prepared soil samples were weighed into a 
100ml of  conical flasks. 15ml of  concentrated Nitric 
(HNO3) acid was added and heated for 30 minutes. 5 ml 
of  Perchloric (HClO4) acid was added to the solution and 
heated further till samples become clear. The samples 
were cooled and 30ml of  distilled water was added. These 
mixtures were filtered using Whatman No 45 filter Paper 
into 100ml volumetric flasks and were made up to 100ml 
mark. These samples were stored in 100ml plastic reagent 
bottle for instrumental analysis. These samples where 
read at recommended wavelength for different elements 
in an Atomic Absorption Spectrophotometer (AAS). 
Heavy metal content in plant were determined with the 
use of  mass spectrometry (MS) usually coupled to liquid 
(LC) or gas chromatography (GC).

Statistical Analysis
Data obtained were subjected to analysis of  variance 
using GENSTAT Version 8 (2012), while Duncan’s 
Multiple Range Test was used to separate means, at 5% 
level of  significance.



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RESULTS AND DISCUSSION
Soil Physical and Chemical Properties of  Dumpsites 
Soils
The physical and chemical properties of  the soil in 
University of  Benin, and Ekosodin, Benin City are shown 
in Table 1 (before planting) and Table 2 (after planting). 
The table 1 pH of  the soils was moderately acidic for 
Farmland with a pH of  (5.61) while for Market and 
Residential where neutral with pH of  (6.79), (6.76) and 
Faculties (6.14) was slightly acidic respectively.  For Table 
2 the pH of  the soil were moderately acidic for Market 
and Residential with value of  (5.68) and (5.80) respectively 
while that of  Farmland and Faculties were strongly acidic 
with pH range of  (5.42) and (5.36) according to the rating 
of  Chude et al., (2011). The total nitrogen (N) in the soil 
decreased at the various dumpsites; however the highest 
total nitrogen value (1.13 g/kg) which is considered 
moderately low and lowest value (0.83g/kg) very low 
were obtained at the Faculties and Market dumpsites 
respectively; while that of  Table 2 recorded very low 
in total N for all dumpsite and according to the rating 
of  Chude et al., (2011). The total Organic carbon (C) in 
the soils in Table 1 increased at various dumpsites. The 
faculties dumpsites 22.5 g/kg (very high) have the highest 
Carbon (C) whereas Market dumpsite had the lowest 
(16.0 g/kg) and all the other dumpsite values considered 
(High) according to the rating of  Chude et al., (2011). In 
Table 2 they all recorded (High) according to the rating 
of  Chude et al., (2011) with this range values of  (14.6), 
(14.8), (15.9) and (18.6) in the decreasing order below. 
The Total Organic Carbon (C) increased in the following 
order: Faculties > Residential > Farmland > Market Area
Table 1 Phosphorus content of  13.6 mg/kg, 14.6 mg/kg, 
14.0 mg/kg and 12.2 mg/kg were recorded on Market, 
Farmland, Residential and Faculties respectively while 
that of  Table 2 contains 9.54 mg/kg in Market, 10.8 mg/
kg in Farmland, 12.1 mg/kg in Residential area and 8.70 
mg/kg in Faculties which they are considered (Moderate) 
according to Chude et al., 2011. The reduction in P content 
of  farmland may be due to the nutrient uptake (Yeshanch, 
2015). The Iron (Fe) content in Table 1 was highest at 
the Residential land with iron content (102.5mg/kg) 
and the Farmland had the lowest iron (53.8mg/kg) in 
these dumpsites. While that of  Table 2, the highest was 
at the Residential land with iron content (89.4mg/kg) 
and the Farm land had the lowest iron (45.8mg/kg); the 

reduction of  these elements in Table 2 is due to plant 
uptake and according to Samaranayke et al., (2012) the 
reduction of  iron in Farm land may be primarily due to 
the low solubility of  the oxidized ferric form in aerobic 
environments. Table 1 shows that, the highest Zinc (Zn) 
value (30.0 mg/kg) was obtained at Residential land 
while the lowest value (25.3mg/kg) was obtained at the 
Farmland. While that of  Table 2, the highest zinc value 
(25.3 mg/kg) was obtained at Residential land while the 
lowest value (20.1 mg/kg) was obtained at the Farmland 
and the variations occurs in Table 1 and 2 because Table 2 
shows the report of  after planting effect. The lowest value 
of  Zinc obtained from Farmland in Table 2 agrees with 
the report of  Brady and Weil (2002) indicated that the 
solubility, availability, and plant uptake of  micronutrient 
cations (Zn) are more under acidic conditions (pH of  
5.00 to 6.60) which the pH of  Farmland falls between 
in Table 2. Table 1 and 2 falls below the target value set 
aside by department of  petroleum resources (DPR) in 
2002 in Nigeria. Table 1 show that Farmland had the least 
Manganese (Mn) content (18.4 mg/kg); closely followed 
by Faculties (20.3 mg/kg) respectively. While the highest 
values (21.6 mg/kg) were recorded on Residential land. 
While that of  Table 2, follows same pattern in variations 
but the major difference between Table 1 and 2 is that; 
nutrient reduction occurs most in Table 2 due to plant 
uptake of  these nutrient.

Dumpsite effect on Particle Size Distribution on Soils
The result of  the soil separates under each dumpsite 
are presented in Table 1 and Table 2. For Table 1 the 
results showed that the texture of  all the dumpsites were 
predominantly sandy having a sand fraction ranging from 
886-852 g/kg; a silt fraction ranging from 80-50 g/kg and 
a clay fraction ranging from 68-54 g/kg. The similarity 
in the textural class could be attributed to the fact that 
soil texture is not readily influenced by soil management 
(Oyedele et al., 2009). For that of  Table 2, the results 
showed that the texture of  all the dumpsites after planting 
were predominantly sandy, i.e there was a major increase 
in sand content of  the soil having a sand fraction ranging 
from 889-878 g/kg; a silt fraction ranging from 69-48 
g/kg and a clay fraction ranging from 63-52 g/kg. The 
reduction in silt and clay could be due to planting effect 
because, humus is present in Silt and CEC is high in Clay 
which shows the presence of  organic matter.

Table 1: Physical and Chemical Properties of  Soils on Dumpsites before Planting
Before Planting Market Farmland Residential Faculties
pH 6.79 5.61 6.76 6.14
T.O.C (g/kg) 16.0 17.0 18.8 22.5
Total N (g/kg) 0.83 0.85 0.94 1.13
Av.P (mg/kg) 13.6 14.6 14.0 12.2
Fe (mg/kg) 92.4 53.8 102.5 95.3
Zn (mg/kg) 28.6 25.3 30.0 27.2
Mn (mg/kg) 20.8 18.4 21.6 20.3



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Heavy Metal Concentration
Copper (Cu) content in Table 3; the highest value 
(35.2mg/kg) was obtained at Residential land while the 
lowest value (30.9mg/kg) was obtained at the Farmland 
before planting. While that of  after planting had highest 
value (30.2mg/kg) was obtained at Residential land 
while the lowest value (24.6mg/kg) was obtained at the 
Farmland and the difference is due to plant uptake. They 
both falls below the target value set aside by department 
of  petroleum resources (DPR 2002) in Nigeria. Lead 
content in Table 3 before planting was highest in dumpsite 
soils of  Market (1.66 mg/kg) and lowest at Farmland 
(0.67 mg/kg) and this also have the same highest and 
lowest value after planting but the difference is observed 
due to plant uptake of  the nutrient in the soil in after 
planting. The highest value in market dumpsites agrees 
with the finding of  Akhilesh et al., 2009, who stated 
that; most serious source of  lead contamination in soil 

is through direct disposal of  different kind of  waste in 
soil. Both results fall below the target value set aside by 
Department of  Petroleum Resources (DPR 2002). The 
concentration of  Cadmium recorded in dumpsite soils 
were as follows; Residential land (0.45 mg/kg) which is 
closely followed by Market (0.44 mg/kg) and lowest at 
Farmland (0.12 mg/kg) before planting. While in after 
planting, there was a variation in dumpsite with Market 
having the highest value (0.26 mg/kg) and lowest value 
in Farmland (0.10 mg/kg); the difference in after planting 
is clear due to plant uptake of  the nutrient in the soil. 
Both results also fall below the target range value set 
aside by DPR (2002). The highest value of  Cd in market 
dumpsites after planting may be due to the concentration 
of  biosolids (sewage sludge), the disposal of  industrial 
wastes or the deposition of  atmospheric contaminants in 
open dumpsites which increases the total concentration 
of  Cd in soils (Weggler, 2004). 

Sand (g/kg) 859 886 852 868
Silt (g/kg) 75 50 80 78
Clay (g/kg) 66 64 68 54

Where N/D: Not Detected

Table 2: Physical and Chemical Properties of  Soils on Dumpsites after Planting
After Planting Market Farmland Residential Faculties
pH 5.68 5.42 5.80 5.36
T.O.C (g/kg) 14.6 14.8 15.9 18.6
Total N (g/kg) 0.83 0.80 0.85 0.90
Av.P (mg/kg) 9.54 10.8 12.1 8.70
Fe (mg/kg) 88.2 45.8 89.4 72.6
Zn (mg/kg) 23.4 20.1 25.3 22.5
Mn (mg/kg) 18.9 15.2 19.5 17.2
Sand (g/kg) 878 889 880 879
Silt (g/kg) 64 48 66 65
Clay (g/kg) 58 63 54 52

Where N/D: Not Detected

Table 3: Heavy Metal Concentration in Soil Before and After Planting
Locations Cu (mg/kg) Pb (mg/kg) Cd (mg/kg) Cr (mg/kg)
Before planting
Market 34.5 1.66 0.44 0.05
Farmland 30.9 0.67 0.12 0.09
Residential 35.2 1.15 0.45 0.11
Faculties 33.7 1.00 0.14 0.14
After Planting
Market 28.8 1.05 0.26 0.03
Farmland 24.6 0.51 0.10 0.04
Residential 30.2 0.83 0.22 0.09
Faculties 26.3 0.80 0.20 0.10

Note: The maximum allowable limit (M.A.L) for heavy metals concentration (mg/kg) use in Nigeria soils as set by the Department of  
Petroleum Resources (DPR) in 1991 for some heavy metals includes: 



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Table 3 shows the highest Chromium value (0.14 mg/
kg) was obtained at Faculties land while the lowest value 
(0.05 mg/kg) was obtained at the Market before planting. 
While that of  after planting had the highest Chromium 
value (0.10 mg/kg) at Faculties land while the lowest 
value (0.03 mg/kg) was obtained at the Market. The 
variations occur in because of  before and after planting 
reading. According to (Raymond and Felix, 2011), 
Chromium mobility depends on sorption characteristics 
of  the soil, including clay content, iron oxide content, and 
the amount of  organic matter present which depict the 
T.O.C of  Faculties dumpsites having the highest value. 
The results actually fall below the target value set aside by 
Department of  Petroleum Resources 2002.

Heavy Metals Concentration in Okra Plants
Table 5, Copper concentration in Okra plant varies and the 
highest uptake is in Residential Land with value of  (36.0 
mg/kg) while the lowest is at Farmland with value of  (23.3 
mg/kg). The normal range of  Cu in plant is given to be 
(0.4-45.8 mg/kg) according to the rating of  Singh and 
Steinnes (1994). This shows that there is no toxicity effect 
on Okra plant cultivated in the various dumpsite soils. 
However, according to WHO (1996) permissible limits of  
10 mg/kg in Vegetables, Copper content in okra vegetable 
is considered high. Lead (Pb) uptake in Okra at the various 
dumpsites studied were given to be Market (0.15 mg/
kg), Farmland (0.10 mg/kg), Residential land (0.12 mg/
kg) and Faculties (0.06 mg/kg) and of  which Market 
dumpsites uptake recorded the highest value among others. 
According to the rating of  Singh and Steinnes (1994) the 
normal plant uptake range of  Pb is given to be (3 mg/
kg) and the toxicity range is soil of  plant (100-400 mg/kg). 
These values show that Pb uptake by Okra plant cultivated 
on the various dumpsites below the normal plant range 
and agrees with WHO (1996) permissible limits of  0.30 
mg/kg for vegetables. Heavy metal uptake of  Cadmium at 
Market dumpsites is (0.05 mg/kg), Farmland value is (0.02 
mg/kg), Residential Area value is (0.01 mg/kg) while that 

Table 4: Heavy metal target value & intervention value
Metals Target value 

(mg/kg) 
Intervention value 
(mg/kg)

Cadmium 0.8 17 
Chromium 100 380 
Copper 36 190 
Lead 85 530 
Zinc  140 720 

Table 5:  Heavy Metal Concentration of  Okra Plants
Heavy Metals Market Farmland Residential Faculties
Cu (mg/kg) 35.8 23.3 36.0 30.4
Pb (mg/kg) 0.15 0.10 0.12 0.06
Cd (mg/kg) 0.05 0.02 0.01 0.04
Cr (mg/kg) ND 0.01 0.01 ND

Where N/D: Not Detected

of  Faculties is (0.04 mg/kg); and according to Kabata and 
Pendias, (1984) the normal plant range of  this element is 
stated to be (0.2-0.8 mg/kg) while the Toxicity range in plant 
is (5-30 mg/kg). This shows that Cd has no toxicity effect 
on Okra plant cultivated on the various dumpsites and the 
uptake is below the normal range in the plants and agrees 
with WHO (1996) permissible limit of  0.1 for vegetables. 
According to Ross (1994), the normal plant range uptake of  
Chromium is given to be (0.006-18 mg/kg) and the uptake 
of  Cr in Farmland and Residential land is given to be (0.01 
mg/kg) respectively, while that of  Market and Faculties is 
not detected. 
The heavy metal uptake by Okra plant cultivated in 
Farmland and Residential land falls between the normal 
ranges, showing that there is no toxicity effect, and this result 
agrees with the permissible limits 10 mg/kg of  WHO (1996) 
for vegetables.

CONCLUSION
The study reveals that dumpsites significantly influence on 
soil properties, particularly pH, nutrient contents, and heavy 
metal concentrations. Planting also impacts these properties, 

with changes in nitrogen, carbon, and phosphorus levels.
Heavy metals in soil raises concerns, but the concentrations 
generally remain below toxic levels. The particle size 
distribution remains consistent across dumpsites and 
planting stages, indicating limited soil management influence. 
Okra plants show variable heavy metal uptake, although 
concentrations largely adhere to permissible limits for safe 
consumption.

RECOMMENDATION
Based on the findings, sustainable soil management practices 
should be implemented to counter dumpsites’ adverse 
effects. Strategies such as organic matter addition and pH 
adjustment could be considered to restore soil fertility 
and structure in farmland soil. Continued monitoring of  
soil properties and heavy metal concentrations is crucial, 
especially in areas affected by dumpsites. Remediation 
techniques such as phytoremediation to reduce heavy metal 
concentrations in soil are encouraged. Conducting further 
research to understand the long-term effects of  dumpsite 
soil on plant growth, human health, and the environment is 
highly suggested.



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