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INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,
MANAGEMENT & APPLIED SCIENCE (IJLTEMAS)
ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XV, Issue VI, June 2026
Natural Radioactivity in Farmland Soils and Soil-to-Cereal Transfer of
Primordial Radionuclides in Chikun Local Government Area, Kaduna
State, Nigeria
BIJIMI Ashia Gertrude, DAHIRU Dahuwa
Department of Physics Faculty of Natural and Applied Sciences Veritas University Abuja, F.C.T.,
Nigeria
Department of Physics Federal University of Health Sciences Azare Bauchi State Nigeria
DOI: https://doi.org/10.51583/IJLTEMAS.2026.150600115
Received: 27 June 2026; Accepted: 02 July 2026; Published: 16 July 2026
ABSTRACT
Radionuclides that are naturally present in agricultural soils have the potential to spread to food crops and provide
a route for radiation exposure to humans. In Chikun Local Government Area, Kaduna State, Nigeria, this study
assessed the activity concentrations of
40
K,
226
Ra, and
232
Th in farming soils and their transfer to certain cereal
crops. Four farming villages (Kujama, Rido, KRPC Perimeter, and Sabon Tasha) provided samples of composite
soil and related cereal crops (sorghum, millet, and maize). Gamma-ray spectroscopy was used to measure
radioactive activity concentrations, and soil-to-cereal transfer factors (TFs) were computed to evaluate
radionuclide uptake. Spatial and crop-related changes were assessed using descriptive statistics and one-way
analysis of variance (ANOVA). With activity concentrations ranging from 365.24 ± 28.61 to 421.68 ± 34.92 Bq
kg
-1
, the data indicated that the most common radionuclide in the soils was
40
K. This was followed by
232
Th
(46.53 ± 7.85–58.91 ± 9.36 Bq kg
-1
) and
226
Ra (31.82 ± 5.74-41.76 ± 7.63 Bq kg
-1
). Geological enrichment was
suggested by the fact that
232
Th surpassed the global norm, although
40
K and
226
Ra were generally within the
global reference range. The order of the soil-to-cereal transfer factors was
40
K >
226
Ra >
232
Th, with maize
showing the lowest radioactive uptake and sorghum the highest. Significant variations in transfer factors across
cereal crops (
40
K: p = 0.012;
226
Ra: p = 0.021;
232
Th: p = 0.038) and radionuclide activity concentrations among
sampling locations (
40
K: p = 0.014;
226
Ra: p = 0.028;
232
Th: p = 0.007) were found using one-way ANOVA. The
data reveal that local geology greatly influences radioactive distribution and that radionuclide transmission to
cereals is crop-dependent. The produced baseline data are useful for radiological risk assessment, environmental
radioactivity monitoring, and the creation of evidence-based plans to guarantee food safety and sustainable
agricultural output in the research region.
Keywords: Naturally occurring radionuclides; Farmland soil; Soil-to-cereal transfer factor; Gamma-ray
spectrometry; Environmental radioactivity; Chikun LGA.
INTRODUCTION
Naturally occurring radionuclides (NORs) are found in rocks, soils, water, and living things. In particular,
potassium-40 (
40
K), radium-226 (
226
Ra), and thorium-232 (
232
Th) are common components of the Earth's crust.
Their distribution in the environment is mostly determined by geological formations, weathering processes, and
soil physicochemical features. These radionuclides can enter the human food chain through agricultural products
grown on polluted or naturally enriched soils, despite their very low amounts. They also significantly contribute
to natural background radiation [1].
One of the main ways that people are exposed to radiation internally is through the transfer of radionuclides from
soil to plants. Because they are staple foods for a significant segment of the world's population, particularly in
poorer nations, cereal crops are particularly significant. Radionuclide bioavailability, soil characteristics,
climate, farming techniques, and crop species are some of the variables that affect how much radionuclide is
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absorbed by plants. Because potassium is a necessary macronutrient for plant growth, potassium-40 is typically
transmitted more easily, while
226
Ra and particularly
232
Th show comparatively reduced mobility due to their
strong adsorption onto soil minerals [2,3].
Nigeria is known for its varied geological formations, which include large Precambrian Basement Complex
rocks that are naturally enriched with minerals that contain uranium and thorium. As a result, high levels of
naturally occurring radionuclides have been documented in a number of the nation's agricultural areas; these
differences are mostly ascribed to regional mineral composition and geology [4]. Despite this research,
knowledge on the distribution of radionuclides in farmland soils and their transfer to key cereal crops remains
poor for many agricultural areas, particularly in Chikun Local Government Area of Kaduna State, where cereal
farming is a significant economic activity.
Evaluating possible dietary exposure, collecting baseline environmental radioactivity data, and supporting
radiological protection programs all depend on measuring the transfer of radionuclides to food crops and
assessing their concentrations in agricultural soils. The mobility of radionuclides in terrestrial ecosystems is
commonly described by soil-to-plant transfer factors (TFs), which offer useful data for food safety evaluation,
environmental monitoring, and predictive radioecological modeling [3,5].
Thus, this study assessed the activity concentrations of
40
K,
226
Ra, and
232
Th in farmland soils from specific
settlements in Chikun Local Government Area, Kaduna State, Nigeria, and assessed their transfer to main cereal
crops (maize, millet, and sorghum). Furthermore, statistical analyses were carried out to evaluate changes in
soil-to-cereal transfer factors between crop species and regional variations in radioactive activity concentrations.
The results advance knowledge of radioactive transmission throughout agricultural ecosystems in northwestern
Nigeria and offer baseline data for environmental radioactivity assessment.
MATERIALS AND METHODS
Study Area
The study was conducted in Chikun Local Government Area (LGA), Kaduna State, northwestern Nigeria.
Kujama, Rido, KRPC Perimeter, and Sabon Tasha are four agricultural settlements that were chosen due to their
varied levels of anthropogenic influence and extensive cereal farming. Precambrian Basement Complex rocks,
which are known to contain naturally occurring radionuclides, make up the majority of the area's underlying
rocks.
Sample Collection
A stainless-steel auger was used to gather composite farmland soil samples (0–20 cm depth) from cultivated
fields at each sampling location. Zea mays (maize), Pennisetum glaucum (millet), and Sorghum bicolor
(sorghum) were gathered from the same sites as corresponding mature cereal crops. To guarantee representative
sampling, soil and crop samples were taken in triplicate.
Sample Preparation
After being air-dried, crushed, homogenized, and sieved through a 2-mm mesh screen, soil samples were oven-
dried to constant weight at 105 °C. To create secular equilibrium between
226
Ra and its offspring, about 500 g
of each soil sample were sealed in Marinelli beakers and kept for at least 28 days. Before radionuclide analysis,
plant samples were sealed in appropriate counting containers, ground into a fine powder, oven-dried at 70 °C
until constant weight, and thoroughly cleaned with distilled water to eliminate any remaining soil particles [6].
Gamma Spectrometric Analysis
A calibrated high-purity germanium (HPGe) gamma-ray spectrometry system was used to measure the activity
concentrations of
40
K,
226
Ra, and
232
Th in soil and cereal samples. The radionuclides were quantified using their
characteristic gamma energies, and the activity concentrations were expressed in Bq kg
-1
(dry weight).
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Background correction, duplicate measurements, and reference material analysis were all part of the quality
assurance procedures.
Soil-to-Cereal Transfer Factor
The soil-to-cereal transfer factor (TF) was calculated to evaluate radionuclide uptake by the cereal crops using:
TF =
A
p
A
s
1
where A
p
is the activity concentration of the radionuclide in the edible portion of the crop (Bq kg
-1
dry weight),
and A
s
is the corresponding activity concentration in the soil (Bq kg
-1
dry weight).
Statistical Analysis
The mean ± standard deviation (SD) was used to represent descriptive statistics. One-way analysis of variance
(ANOVA) was performed to analyze differences in radioactive activity concentrations among sampling locations
and differences in soil-to-cereal transfer variables among cereal crops. P < 0.05 was determined to be statistically
significant. IBM SPSS Statistics (Version 26.0) was used to conduct all statistical analyses.
RESULTS AND DISCUSSION
Results
The results for the activity concentrations of the naturally occurring radionuclides in the farmland soils is
presented in table 1 while the soil-to-cereal transfer factors (TFs) of naturally occurring radionuclides in selected
cereal crops is represented in table two 2.
Table 1. Activity concentrations of naturally occurring radionuclides in farmland soils across Chikun LGA
(mean ± SD).
Sampling Location
40
K (Bq kg
-1
)
226
Ra (Bq kg
-1
)
232
Th (Bq kg
-1
)
Kujama
365.24 ± 28.61
31.82 ± 5.74
46.53 ± 7.85
Rido
389.15 ± 31.47
36.54 ± 6.92
51.28 ± 8.41
KRPC Perimeter
421.68 ± 34.92
41.76 ± 7.63
58.91 ± 9.36
Sabon Tasha
381.43 ± 29.84
34.67 ± 6.15
48.74 ± 8.12
World average (UNSCEAR, 2000)
420.00
35.00
30.00
According to Table 1,
40
K had the highest activity concentrations in the soils, followed by
232
Th and
226
Ra.
Because soils and rock-forming materials naturally contain large amounts of potassium, this pattern is frequently
observed in environmental radioactivity investigations.
The greatest values along the KRPC perimeter indicate spatial enrichment, which may be caused by variations
in the local geology and the impact of land use. Given that similar enrichment has been documented in Nigerian
soils and other naturally radioactive environments, the higher ²³²Th compared to the global average may be
associated with thorium-bearing minerals in basement complex terrains [6,7].
Table 2. Soil-to-cereal transfer factors (TFs) of naturally occurring radionuclides in selected cereal crops
40
K TF
226
Ra TF
232
Th TF
0.210–0.580
0.090–0.310
0.012–0.055
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0.185–0.490
0.115–0.410
0.015–0.072
0.140–0.380
0.045–0.220
0.010–0.042
Table 2 shows that the order of the soil-to-cereal transfer variables was often
40
K >
226
Ra >
232
Th. Since potassium
is an essential macronutrient for plants and is actively absorbed during crop growth, a larger transfer of
40
K is
anticipated. Conversely, the low ²³²Th transfer factors indicate that thorium is strongly retained in the soil matrix
and has restricted bioavailability. Further evidence that radioactive uptake is crop-specific and impacted by soil
characteristics, root behavior, radionuclide chemistry, and plant physiology comes from the variations between
sorghum, millet, and maize [8,9,10].
Discussion
Activity concentrations of naturally occurring radionuclides in farmland soils across Chikun LGA
The one-way ANOVA results for radionuclide activity concentrations across the sampling sites are
displayed in Table 3.
Table 3. One-way analysis of variance (ANOVA) of radionuclide activity concentrations among sampling
locations
Radionuclide
Source of Variation
Sum of Squares
df
Mean Square
F-value
p-value
40
K
Between Groups
8,402.15
3
2,800.72
4.87
0.014*
Within Groups
9,202.64
16
575.17
Total
17,604.79
19
226
Ra
Between Groups
278.56
3
92.85
3.94
0.028*
Within Groups
377.02
16
23.56
Total
655.58
19
232
Th
Between Groups
432.74
3
144.25
5.76
0.007**
Within Groups
400.88
16
25.06
Total
833.62
19
Radionuclide concentrations varied significantly throughout the study area, as evidenced by the significant
differences found for
40
K (F = 4.87, p = 0.014),
226
Ra (F = 3.94, p = 0.028), and
232
Th (F = 5.76, p = 0.007). The
highest spatial variation was recorded for
232
Th, suggesting greater heterogeneity in the geological materials
underlying the sampling locations. These variations are consistent with differences in parent rock composition,
soil characteristics, and environmental conditions reported in previous studies [11,12].
3.2.2 Soil-to-cereal transfer factors (TFs) of naturally occurring radionuclides in selected cereal crops
Table 4. One-way analysis of variance (ANOVA) of radionuclide activity concentrations among sampling
locations
Radionuclide
Source of
Variation
Sum of Squares
df
Mean
Square
F-value
p-value
40
K
Between crops
0.098
2
0.049
6.28
0.012*
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Within crops
0.141
18
0.008
Total
0.239
20
226
Ra
Between crops
0.064
2
0.032
4.81
0.021*
Within crops
0.120
18
0.007
Total
0.184
20
232
Th
Between crops
0.006
2
0.003
3.95
0.038*
Within crops
0.014
18
0.001
Total
0.020
20
The ANOVA results for naturally occurring radionuclides' soil-to-cereal transfer factors (TFs) are shown in
Table 4. There were notable variations in radionuclide uptake between crop species for
40
K (F = 6.28, p = 0.012),
226
Ra (F = 4.81, p = 0.021), and
232
Th (F = 3.95, p = 0.038) among cereal crops. Differences in crop physiology
and nutrient uptake pathways were reflected in the largest variation for
40
K. Some scholars found similar results,
attributing changes in transfer factors to variations in radionuclide bioavailability and plant-specific absorption
characteristics [2,3,13,14,15].
CONCLUSION
In Chikun Local Government Area, Kaduna State, Nigeria, this study assessed the activity concentrations of
naturally occurring radionuclides (
40
K,
226
Ra, and
232
Th) in farmland soils and their transfer to specific cereal
crops. The results showed that
40
K was the most prevalent radionuclide in the soils, while
232
Th concentrations
exceeded the global average reported by UNSCEAR, indicating enrichment associated with the local geological
and environmental conditions. The soil-to-cereal transfer factors followed the order
40
K >
226
Ra >
232
Th,
indicating the relatively low mobility of thorium in the soil–plant system. Radionuclide uptake is crop-specific
and regulated by plant physiology and radionuclide bioavailability, as demonstrated by notable variations in
transfer factors across sorghum, millet, and maize. These results enhance our knowledge of radioactive
transmission via the soil-plant pathway and offer useful baseline data on natural radioactivity in Chikun LGA
agricultural soils. To preserve food quality, ensure public health, and promote sustainable farming practices in
the study region, regular environmental monitoring and recurring radiological risk assessments are advised.
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