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AASCIT Journal of Environment
2017; 2(5): 48-55
http://www.aascit.org/journal/environment
ISSN: 2381-1331 (Print); ISSN: 2381-134X (Online)
Keywords Pesticide Residues,
Organochlorines,
Soil,
Water,
Floodplains,
GC-MS,
Minna
Received: August 15, 2017
Accepted: September 6, 2017
Published: October 13, 2017
Assessment of Organochlorine Pesticide Residues in Soil and Water from Fadama Farming Communities in Minna, North Central, Nigeria
Ogbonnaya Ikechukwu Chikezie1, *
, Mann Abdullahi2,
Yisa Jonathan2, Bala Abdulalahi
1
1Department of Soil Science and Land Management, Federal University of Technology, Minna,
Nigeria 2Department of Chemistry, Federal University of Technology, Minna, Nigeria
Email address [email protected] (O. I. Chikezie) *Corresponding author
Citation Ogbonnaya Ikechukwu Chikezie, Mann Abdullahi, Yisa Jonathan, Bala Abdulalahi. Assessment of
Organochlorine Pesticide Residues in Soil and Water from Fadama Farming Communities in
Minna, North Central, Nigeria. AASCIT Journal of Environment. Vol. 2, No. 5, 2017, pp. 48-55.
Abstract The high pesticide residue in soil and water in the floodplains in Minna is of great
concern because the soil is used for cereal and vegetable cultivation and the water used
for domestic purposes. Therefore, organochlorine multi-pesticide residue analysis were
determined in soil and water collected from the vegetable growing floodplains in Minna,
North Central, Nigeria, where urban and peri-urban agriculture is practiced with
extensive application of synthetic pesticides. Analysis was carried out using the gas
chromatograph with mass spectrometric (GC-MS) detection technique. Organochlorine
pesticide residues detected in soil and water in Minna included endosufan-II, p,p'-DDT,
δ-BHC and heptachlor. Heptachlor and p,p’-DDT were the most common detected
organochlorines in the soil and the water samples. All the detected pesticide residues in
soil and water had concentrations that greatly exceeded the maximum residue limits
(MRLs). Heptachlor had (11.310 ± 0.46 mgkg-1
) > 0.03 mgkg-1
, δ-BHC (0.581 ± 0.32
mgkg-1
) > 0.02 mgkg-1
, p,p-DDT (0.296 ± 0.04 mgkg-1
) > 0.01 mgkg-1
, and endosulphan-
II (0.056 ± 0.03 mgkg-1
) > 0.02 mgkg-1
. Plant uptake of pesticides poses health risks to
domestic livestock that forage on crop stubble and consumers of food products from
these animals. The need for regular and stringent monitoring of pesticide residues in soil
and water in the floodplains in Minna, North Central, Nigeria is advocated while farmers
are adviced to adopt good agricultural practice.
1. Introduction
Organochlorine pesticide residues most commonly found in soil and water are
pesticides that are intentionally applied to cultivated crops to attack crop pests and
diseases (FAO/WHO, 2004). Global reports show that organochlorine pesticide usage
has increased significantly during the past three decades (Gilden et al., 2010). The
extensive use of pesticides for agriculture and non-agricultural purpose has resulted in
their enrichment in various environmental matrices, especially, soil water and food
(Darko and Akolo, 2008; Cardenas-Gonzalez et al., 2013). Modern and mechanized
49 Ogbonnaya Ikechukwu Chikezie et al.: Assessment of Organochlorine Pesticide Residues in Soil and Water from
Fadama Farming Communities in Minna, North Central, Nigeria
agriculture cannot operate without any form of chemical
pesticide of some sort, food production would probably
decline precipitously in many areas, prices of food would
soar for higher and food shortages would become more
severe (Uygun et al., 2005).
High levels of pesticide residues arising from improper
and unregulated application and multiple sprays of sub-lethal
doses have been reported to be responsible for the poisoning
and several adverse health hazards in both rural and urban
areas in Nigeria and Niger State in particular (NAFDAC,
2004; Berrade et al., 2010). According to the Centers for
Disease Control and Prevention (CDCP) Organochlorine
pesticides are ubiquitous environmental contaminants
because they break down very slowly.
In the European Union (EU), hexachloro-benzene (HCB),
dichlorodiphenyltrichloroethane (DDT), chlordane and
hexachloro-cyclohexane (HCH, which exists as different
forms, or “isomers”, one of which, γ-HCH, is lindane) has
been banned. According to (Yang et al., 2005), they are all
persistent and bio-accumulative chemicals, found widely in
the environment, wildlife and humans. Due to legislative
action in developed countries, the levels of organochlorine
pesticides are slowly declining. The DDT, chlordane and
HCB are classified as persistent organic pollutants (POPs)
under the Stockholm Convention of (2011). Ritter et al.,
(2007) stated that lindane is designated as a POP under the
European Commission (EC) Protocol, and is under
consideration for inclusion under the Stockholm Convention.
The two main groups of organochlorine insecticides are
the DDT-type compounds and the chlorinated alicyclics.
Their mechanism of action differs slightly: The DDT like
compounds work on the peripheral nervous system, and
prevent gate closure after activation and membrane
depolarization. (Da-Cuna et al., 2011). Chlorinated
cyclodienes include aldrin, dieldrin, endrin, heptachlor,
chlordane and endosulfan. They are hazardous
organochlorines, about 2 to 8 hour exposure to these OCPs
may lead to the depression of the central nervous system
(CNS) activity, followed by hyperexcitability, tremors, and
then seizures (Hayat et al., 2010). Other examples include
dicofol, mirex, kepone and pentachlorophenol. These can be
either hydrophilic or hydrophobic depending on their
molecular structure.
Some types of organochlorides have significant toxicity to
plants or animals, including humans. Dioxins, produced
when organic matter is burned in the presence of chlorine,
and some insecticides, such as DDT, are persistent organic
pollutants which pose dangers when they are released into
the environment. For example, DDT, which was widely used
to control insects in the mid-20th century, also accumulates
in food chains, and causes reproductive problems (eggshell
thinning) in certain bird species. Some organochlorine
compounds, such as sulfur mustards, nitrogen mustards, and
lewisite, are also used as chemical weapons due to their
toxicity. However, the presence of chlorine in an organic
compound does not ensure toxicity. Some organochlorides
are considered safe enough for consumption in foods and
medicines.
The present study investigates the pollution level of
organochlorine pesticide residues in soil and water of fadama
communities in Minna, North Central, Nigeria, where urban
and peri-urban agriculture is practiced with extensive inputs
of synthetic pesticides and agrochemicals to improve
agricultural production.
2. Methodology
The Study area is in Minna the capital of Niger State,
Nigeria. It lies between longitude 9° 40' N to latitude 6° 27' E
and longitude 9° 33' N to latitude 6° 35' E. It is in the North
Central region of Nigeria covering an area of about
100,899km2 with a population of about 5,17,1107 [G Nat.
Population]. The study area is characterized by three seasons:
the cool, dry (Harmattan) season (October- January), hot dry
season (February-April) and rainy season (June-September).
The mean annual rainfall in the area is about 1200 mm, while
the minimum and maximum temperatures are 26°C and 34°C
respectively (Federal Meteorological Agency, Minna, 2011).
Temperature rarely falls to 22°C. Wet season temperature
average is about 29°C. The peaks are 34°C (February to
March). Minna lies in the Guinea Savanna agro-ecological
zone which is characterized by vegeteation comprising of tall
trees with grasses and shrubs. The soil possess large amount
of conditionally water stable aggregates (FDALR, 1985).
Sampling and Sample Selection
Four floodplains at different parts of Minna (Bosso,
Chanchage, Maikunkele and Maitumbi) were selected based
on their geographic proximity to elevated centres of
population and the presence of urban and peri-urban fadama
cultivation with widespread use of pesticides
From the four floodplains, soil and water samples were
taken at four points. Grab sampling technique (Staare et al.,
2000) was employed in the collection of the surface water
samples. The water temperature and pH were measured
directly from the water samples using pH meter (Hanna
Instrument H1.991301) before transferring into scrupulously
cleaned screw-cap bottles under ice pack pending their
extraction.
Soil samples were taken from four floodplains at five
points at the depth of 0-20 cm using the soil auger and a
composite made for each floodplain. The soil samples were
air dried in the laboratory for about 1 week, picked for
obvious extraneous material, ground with porcelain mortar
and pestle, and sieved through 2 mm wire mesh. The samples
were stored in brown bottles prior to extraction. The
sampling points were all geo-referenced with Global
Positioning System (GPS Garmin eTrex10 Model).
Materials and Preparation
All the reagents used were of analytical grade from
AASCIT Journal of Environment 2017; 2(5): 48-55 50
ACUSTAT Standards, Inc. USA. and included n-Hexane,
acetone, diethyl ether, ethyl acetate, methylene chloride,
sodium sulphate, silica gel, toluene and methanol. Proper
cleaning of the glass wares was ensured to avoid sample
contamination. The glass wares used for organochlorine
pesticide determination were cleaned as recommended by the
method 1669 of United States Environmental Protection
Agency (USEPA), (2007). The activated silica gel clean up
procedure and the anhydrous sodium sulphate used for drying
the samples were prepared in accordance with USEPA
method 1699.
Figure 1. Map of Minna, Niger State showing the study site.
51 Ogbonnaya Ikechukwu Chikezie et al.: Assessment of Organochlorine Pesticide Residues in Soil and Water from
Fadama Farming Communities in Minna, North Central, Nigeria
Physico-chemical Analysis of the Soil
Samples
The particle size distribution of the soil was determined
using the Bouyoucous hydrometer method (IITA, 2009),
involving mainly the dispersion of the soil using sodium
hexametaphosphate (Calgon). The Walkley Black wet
oxidation method (Schulte, 1995) was used to determine the
organic carbon content of the soil and hence the organic
matter. The moisture content was determined by the
gravimetric method while the cation exchange capacity was
determined by the NH4OAC displacement and summation of
the exchangeable cations (Na, K, Ca and Mg). pH was
determined in-situ using the pH meter (Hanna Instruments HI
991301).
Extraction of Organochlorine Pesticide
Residues from Soil and Water Samples
Extraction of soil samples was carried out using the
method described by Ize-Iyamu et al., (2007) with slight
modifications. A mixture of 25 g sample and 50 g granular
sodium sulphate was ground into a powdery consistency
using a mortar and pestle. The ground sample was extracted
with 150 cm3 of a mixture of n-Hexane and acetone (1:2).
The extract was transferred into a round bottomed flask and
concentrated to about 20 cm3 on a water bath maintained at
50°C - 55°C. The remaining solvent in the concentrated
extract was evaporated using a rotary evaporator (Buchi R
110 Brinkmann TM
) to about 5 cm3. The concentrated extract
was quantitatively transferred to a centrifuge tube,
concentrated on a nitrogen evaporator to 0.5 cm3 and diluted
to 2 cm3 in hexane pror to GC-MS analysis.
Clean up Procedures for the Sample Extract
Various components with large molecular size such as
lipids, proteins, pigments and residues are co-extracted with
pesticide molecules (Tiryaki et al., 2006). These substances
are referred to as ‘dirts’ and are necessarily removed from the
extracts prior to chromatographic analysis, as they may cause
interferences in the chromatographic system and detection,
and may also damage the GC equipment. However, in this
study, no clean- up was required for the water samples as
they were relatively clean with no obvious co-extracted dirts.
Clean up of Soil Extracts
The concentrated soil extract was washed by liquid-liquid
partitioning with 120 cm3 of saturated sodium sulphate and
250 cm3 of distilled water. After shaking, the aqueous was
drained into a beaker and the hexane was transferred to a
separatory funnel. The aqueous layer was returned to a 500
cm3 separatory funnel and re-extracted with 40 cm
3 of
dichloromethane in hexane. The organic layers were
combined in a 250 cm3 separatory funnel and gently washed
with 100 cm3 distilled water for about 30 seconds. After the
aqueous layer was discarded, the organic layer was filtered
through sodium sulphate, evaporated to near dryness on a
rotary evaporator. The sides of the flask were rinsed down
with 120 cm3 of hexane and evaporated to about 1.0 cm
3. The
sample extract was quantitatively transferred to centrifuge
tube, concentrated on a nitrogen evaporator to 0.5 cm3 and
diluted to 2.0 cm3 final volume and subsequently presented
for GC-MS analysis.
Gas Chromatograph-Mass Spectrometry
Instrumentation
All the extracts (soil and water) were determined with the
aid of a gas chromatograph equipped with a mass-selective
detector (GC-MS), an auto-sampler and a split-split less
injector. The DB-5 fused silica capillary column of 30m x
0.25µm i.d. x 0.25µm film thickness was coated with cross
linked 5% phenyldimethyl polysiloxane. The carrier gas was
helium (99.999% purity) at a flow rate of 1.0ml/min. Oven
temperature was maintained initially at 40°C for 1min,
increased at 12°C/min to 280°C, then at 20°C/min to 215°C,
at 100°C/min to 265°C and finally at 200°C/min to 290°C
and held for 8 min. Injection volume was 1µL, injected in
split less mode at injection temperature of 250°C. The mass
spectrometer was operated in electron impact (EI) ionization
mode with a detector voltage of 700V, ion source
temperature of 200°C, GC interface temperature of 320°C
and emission current of 150 µV. Acquisition mode was
selected ion Monitoring (SIM).
Table 1. Names, Retention Time, Correlation Coefficient, Limit of Detection and Maximum Residue Limit of the Pesticides.
Pesticide (Common name) Retention Time
(mins)
Correlation Coefficient
(r2)
Limit of Detection
(mgkg-1) *(LOD)
Maximum Residue Limit
(mgkg-1) **(MRL)
α-BHC 12.46 0.9993 0.011 0.010
Heptachlor 13.86 0.9977 0.011 0.030
Dieldrin 17.38 0.9958 0.021 0.050
Endosulphan-II 18.05 0.9986 0.014 0.020
p,p'-DDT 18.93 0.9985 0.007 0.100
δ-BHC 12.46 0.9984 0.010 0.020
Lindane 12.46 0.9994 0.026 0.010
p,p'-DDD 18.96 0.9819 0.014 0.010
*LOD- Limit of Detection of GC-MS
**MRL- Maximum Residue Limit (EU, FAO/WHO, 2006)
AASCIT Journal of Environment 2017; 2(5): 48-55 52
Figure 2. Chromatogram of 15 Organochlorine Standard Pesticide mix (0.50 mgL-1) in acetonitrile.
3. Results and Discussion
The results of the physio-chemical properties of the soil
samples from the floodplain under study are presented in
Table 2. The pH of soil from Minna floodplains were slightly
acidic and ranged between 6.0 and 6.5. It is noteworthy that
most soils of the Nigerian Guinea savannah show similar pH
trend, Federal Department of Agriculture and Land
Resources (FDALR), (1985). The soil organic matter content
of the soil were moderately high and ranged between 13.51
gkg-1
and 15.61 gkg-1
It supported the growth of both cereals
and vegetables, this may be due to the fact that the tests soils
are surface soil samples (0-20cm depth) where
decomposition, synthesis process and other biological
activities are progressively taking place (Lee et al., 2003).
The particle size analysis of the soils studied revealed that the
fadama soils were predominately sandy clay loam (SCL)
soils. This implies that pesticide residues and organic
pollutants may not easily migrate down the soil profile to
pollute groundwater due to the high clay content. The
Electrical Conductivity (EC) of the soil were low and ranged
between (201.45 µScm and 121.38 µScm-1
), however, the
Cation exchange capacity of the soils were moderately high
and ranged between 9.58 Cmolkg-1
and 12.02 Cmokg-1
The
low level of EC and CEC coupled with the high clay content
of the soils may retard the movement and mass transfer of
pesticide residues to contaminate groundwater. The pesticide
residues are adsorbed by the fine clay particles which will
restricts the movement of the pesticides down the soil profile
to pollute groundwater, similarly, due to the high organic
matter content of the soil, and duet to the organic synthesis
and bio-transformtions progressively taking place in the soil,
pesticide residues are may only be transported and transfered
to the root zones where they are taken up by plants (Lee et al.,
2003).
Table 2. Physicochemical Characteristics of Selected Fadama Soil samples from Minna.
Minna Sand (%) Silt (%) Clay (%) Textural Class
(U.S.D.A) pH (CaCl2) EC mScm-1 OM gkg-1
CEC
Cmolkg-1
Moisture
(%)
Bosso 58 18 24 SCL 6.0 121.38 14.59 9.58 94.05
Chanchaga 60 17 23 SCL 6.2 132.43 13.51 12.02 93.01
Maikunkele 61 13 26 SCL 6.5 138.45 15.61 10.30 96.09
Maitumbi 60 18 22 SCL 6.4 135.32 14.72 12.91 92.97
EC—Electrical Conductivity
OM—Organic Matter
CEC– Cation Exchange Capacity
SCL – Sandy Clay Loam
53 Ogbonnaya Ikechukwu Chikezie et al.: Assessment of Organochlorine Pesticide Residues in Soil and Water from
Fadama Farming Communities in Minna, North Central, Nigeria
The mean concentration of organochlorine pesticides
identified in soil is presented in Table 3. Two pesticide
residues were detected in soil and samples from the floodplains
in Minna and these include – Endosulphan and p,p'-DDT. The
mean concentration of pesticide residues detected in soil
samples from Minna floodplains are endosulphan that ranged
between 0.049 mgkg-1
and 0.056 mgkg-1
and while p,p'-DDT
ranged between 0.289 mgkg-1
and 0.298 mgkg-1
and All the
pesticides detected in soil in the four floodplains under study
had pesticide residue concentrations that exceeded the
maximum residue limits (MRL).
Table 4 depicts the mean concentration of organochlorine
pesticide residues in water samples from Minna. The residues
include heptachlor which mean concentration ranged from
10.211 mgkg-1
to 11.312 mgkg-1
and δ-BHC that ranged
between 0.497 mgkg-1
to 0.581 mgkg-1
. All the pesticide
residues identified and quantified in water in the floodpains
in Minna greatly exceeded the maximum residue limits
(MRLs). Heptachlor and p,p'-DDT were the frequently
detected organochlorines in the soil and the water samples.
The study revealed that the exceedingly high concentrations
of pesticides detected in the soil and surface water from the
floodplains probably may have been contributed from some
non-point sources such as run-off applications of pesticide
upstream which ends up in the floodplains, atmospheric fall-
out or chemical drift during application and practices such as
washing spraying equipment’s in surface water could also be
a source of contamination of soil and water in the floodplains.
The results show that the transport and transfer of the
organochlorine pesticides in the soil was restricted by the
high clay, and organic matter content and the slightly acidic
nature of the soils of the floodplains. The slightly acidic
nature of the soils enhances the adsorption and binding of
pesticide residues to the clay minerals, thereby, increasing
their residency period in the soil which allows transport of
pesticides down to the root zone where due to the high
organic matter content of the soils and the synthesis and bio-
transformations taking place, the pesticides are transported to
the root zones where they are taken up by vegetables and
cereal crops that are cultivated in the floodplains (Kellogg et
al., 2000).
The results of this study when compared with USEPA and
the Codex Alimentarius FAO/WHO, 2004 MRL indicate that
the concentration of the pesticide residues detected in soil
and water greatly exceeded the allowable maximum residue
limits. Most pesticide residues identified in this study are
known to be neurotoxic, others have been found to be
carcinogenic, teratogenic and depress immune responses,
while others have been identified as endocrine disruptors,
this implies that they can affect human growth and
reproduction (Monsour, 2004; Jobling et al., 1995; Koprucu
et al., 2006). The high concentrations of organochlorine
pesticide in soil and water in Minna floodplains pose a risk to
the human and aquatic life and provide an indication of
unregulated application of hazardous pesticides in the
floodplains in Minna.
Table 3. Concentration (mgkg-1) of Organochlorine Pesticide Residues in Soil in Minna.
Pesticide Bosso (Mean±
SD) (mgkg-1)
Chanchaga
(Mean± SD)
(mgkg-1)
Maikunkele
(Mean± SD)
(mgkg-1)
Maitumbi
(Mean±SD)
(mgkg-1)
Retention
time (mins)
Identified
Molecular
weight (gmol-1)
MRL
(mgkg-1)
α-BHC Nd Nd Nd Nd Nd Nd 0.01
Heptachlor Nd Nd Nd Nd Nd Nd 0.03
Dieldrin Nd Nd Nd Nd Nd Nd 0.05
Endosuphan-II 0.056 ± 0.03 0.054 ± 0.02 0.049± 0.02 0.051± 0.03 18.05 406.00 0.02
p,p'-DDT 0.296 ± 0.04 0.298 ± 0.02 0.293 ± 0.03 0.289 ± 0.02 18.94 354.00 0.10
δ-BHC Nd Nd Nd Nd Nd Nd 0.02
p,p'-DDD Nd Nd Nd Nd Nd Nd 0.01
γ-Lindane Nd Nd Nd Nd Nd Nd 0.01
trans-Permethrin Nd Nd Nd Nd Nd Nd 2.00
cis-Permethrin Nd Nd Nd Nd Nd Nd 2.00
n = 20 samples; MRL =Maximum Residue Limit; Nd = not detected
Table 4. Concentration (mgL-1) of Organochlorine Pesticide Residues in Water in Minna.
Pesticide Bosso (Mean±
SD) (mgL-1)
Chanchaga
(Mean± SD)
(mgL-1)
Maikunkele
(Mean± SD)
(mgL-1)
Maitumbi
(Mean±SD)
(mgL-1)
Retention
time (mins)
Identified
Molecular
weight (gmol-1)
MRL
(mgL-1)
α-BHC Nd Nd Nd Nd Nd Nd 0.01
Heptachlor 11.310 ± 0.46 10.321 ± 0.21 11.054 ± 0.32 10.981 ±0.26 13.86 372.50 0.03
Dieldrin Nd Nd Nd Nd Nd Nd 0.05
Endosuphan-II Nd Nd Nd Nd Nd Nd 0.02
p,p'-DDT Nd Nd Nd Nd Nd Nd 0.10
δ-BHC 0.581 ± 0.32 0.497 ± 0.20 0.534 ± 0.04 0.512 ± 0.03 12.46 290.00 0.02
p,p'-DDD Nd Nd Nd Nd Nd Nd 0.01
γ-Lindane Nd Nd Nd Nd Nd Nd 0.01
trans-Permethrin Nd Nd Nd Nd Nd Nd 2.00
cis-Permethrin Nd Nd Nd Nd Nd Nd 2.00
n = 20 samples; MRL =Maximum Residue Limit; Nd = not detected
AASCIT Journal of Environment 2017; 2(5): 48-55 54
4. Conclusion
The study clearly established that organochlorine pesticide
residues constitute a major source of contamination in soil
and water in the floodplains in Minna. The study also
revealed that DDT, heptachlor, endosuphan and δ-BHC are
used indiscriminately and without regulation in the
floodplains in Minna.
Based on the above findings the relevant regulatory
agencies of government should urgently legislate, regulate
and intensify the advocacy in the proper use of hazardous
pesticides and agrochemicals in agricultural farm lands.
Good agricultural practice (GAP) should be encouraged and
awareness created on the need for the use of protective
clothing, storage regulation, distribution and good personal
hygiene adopted by farmers that regularly use synthetic
hazardous pesticides and agrochemicals. Further studies
should be carried out on other pesticide groups such as
carbamtes and synthetic pyrethroids used in the floodplains
which have not been investigated in this study to ensure that
their residues are within safety limits.
Acknowledgements
The authors acknowledge the support of the Central
Laboratory of the National Food Drugs Administration and
Control (NAFDAC), Lagos for supporting the analyses of the
soil and water samples. We also appreciate Professor A.
Gachanja, Administrator, Pan African Chemistry Network
(PACN) and Dr. Steven Lancaster of the Royal Society of
Chemists (RSC) for sponsoring the Principal Investigator to
the Workshop held at Jomo Kenyata University of Science
and Technology, Nairobi, Kenya on GC-MS Technique and
interpretation.
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