Groundwater quality assessment for irrigation and drinking water: health risks from heavy metals and PAHs in the Niger Delta, Nigeria

Groundwater pollution frequently occurs as contaminants migrate from the soil into the ground level (Cho et al. 2023). If the topsoil is polluted, it can eventually contaminate the groundwater. The geology of the soil can also impact the potential of the underlying aquifer to become polluted (Yang 2021). However, water can be polluted by oil and other natural substances that are insoluble in water, and therefore they are normally found connected to or adsorbed into sediments (Nsabimana & Li 2022; Akakuru et al. 2023). The physicochemical parameters such as pH, conductivity, total dissolved solids (TDS), and temperature point toward water pollution (Ibe et al. 2020). If the groundwater is found to be contaminated, it is important to measure the levels of certain pollutants, such as heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs), in order to determine the extent of the pollution and assess the potential health risks of the people using the water (Ibe et al. 2018, 2020). Among nature's abundant gifts, water holds a position of extreme importance, second only to air (Rohde et al. 2017; Edokpayi et al. 2018; Ihenetu et al. 2020; Reberski et al. 2022). When it comes to irrigation waters, salinity, sodicity, and ion toxicity represent substantial quality challenges (Mohamed & Hoda 2023). To ensure the continuous monitoring of soil and water resources for variability in salt concentrations, continuous environmental assessment becomes essential (Cho et al. 2023). These changes in salt concentration are critical since they can exceed the threshold levels at which certain salts, including ⁠, ⁠, Na⁺, Cl⁻, Mg²⁺, and various trace elements, negatively affect plant growth (Mammeri et al. 2023). The water quality index (WQI) serves as a valuable tool for assessing the quality of irrigation water.

Crude oil exploration is a significant financial venture in Nigeria, resulting in the influx of PAHs and HMs into soils and water bodies due to oil spillage (Agbozu et al. 2017; Ambade et al. 2022; Akash et al. 2023). Some studies have evaluated the concentrations of HMs and irrigation studies (Duru et al. 2017; Akakuru et al. 2022, 2023) and PAHs (Huang et al. 2023) in groundwater. Amadi et al. (2020) used the metal pollution index and factor analysis to analyze the effects of HMs in groundwater in part of the Niger Delta and reported that nickel, cadmium, lead cobalt, chromium, copper, iron, mercury, zinc, arsenic, and manganese polluted the groundwater at various concentrations (Akakuru et al. 2022). For PAHs, Amadi et al. (2020) conducted a study on the diesel contamination of groundwater in Ring Road, Jos, Plateau State, Nigeria, and found that the distribution of PAHs in the groundwater was dominated by three-fused-ring PAHs, indicating a petrogenic origin. In terms of direct ingestion, phenanthrene, acenaphthylene, and fluorene exhibited the highest exposure doses of PAHs. Also, when considering dermal absorption, benzo(a)anthracene, benzo(b)fluoranthene, and benzo(k)fluoranthene were associated with the highest exposure doses. According to Ejiogu et al. (2019), PAHs concentration in water samples can be attributed to pyrogenic sources, and some are linked to petrogenic origins. Every stage of a crude oil spill has detrimental effects on the environment, and Ohaji-Egbema is no exception. Over 40 years of oil drilling in Nigeria, more than 6,000 spills have been documented, averaging 150 spills annually (Enyoh et al. 2018; Enyoh & Isiuku 2020). Oil spills have contaminated a significant portion of farmlands in the Niger Delta region, including Ohaji-Egbema, leading to the transformation of once-productive areas into wastelands (Chika et al. 2014).

The novelty of this research lies in the application of advanced, previously unused models for the comprehensive analysis of groundwater quality, health risks, and irrigation suitability in the Niger Delta region of Imo State, Nigeria. This approach not only provides a more detailed assessment of the environmental impact of crude oil exploration but also offers new insights into the interaction between various pollutants and local groundwater resources, which have not been explored in prior studies. This study, therefore, seeks to carry out physicochemical, pollution, health risk, and irrigation quality evaluation of some groundwater in these areas. This is especially crucial as the inhabitants of this area rely on groundwater for drinking, and domestic and agricultural activities. Second, the models employed for the analysis of the results represent a departure from previous approaches, as they have not been previously used in the study of groundwater in this area. The significance of this study is as follows: (1) the study places its focus on a region heavily impacted by crude oil exploration, namely the Niger Delta area in Imo State, Nigeria. (2) Groundwater is a vital resource in this region, serving as a source of drinking water for the local population and supporting agricultural activities. (3) This study contributes significantly to the understanding of environmental sustainability in regions impacted by industrial activities and highlights the importance of proactive environmental management to mitigate pollutant impacts and safeguard public health.

Sampling was done according to our previous research (Wang et al. 2020; Ihenetu et al. 2021b). Random sampling was used for sample collection, with 45 samples collected from each of the three communities: Mmahu-Egbema, Obosima, and Umuagwo, shown as A, B, and C, respectively. In each community, the samples were composited, resulting in a total of 135 samples across all areas. Sampling was done from February 2022 to November 2022. Control samples were also collected and labeled as D and E. As a reference, control samples were collected from Owerri Municipal, a local government area in Imo State, characterized by the absence of any recorded crude oil pollution. For the sample collection, 500 mL plastic bottles were used, carefully cleaned with 10% nitric acid, thoroughly rinsed with distilled water, and oven-dried to prevent bacterial degradation. Following collection, these bottles were promptly placed in an icebox and transported to the springboard laboratory for analysis. Upon arrival, they were stored in a refrigerator at 4°C before undergoing pretreatment analysis. For HM analysis, each sample was filtered using 0.45 μm membrane filters to remove particulate matter. The filtered samples were then acidified with concentrated nitric acid to a pH of less than 2 to preserve the metal ions and prevent precipitation. For PAHs analysis, the samples were extracted using liquid–liquid extraction with dichloromethane, followed by concentration under reduced pressure. The concentrated extracts were then purified using silica gel chromatography. The concentrations of HMs were determined using a Varian AA240 atomic absorption spectrophotometer, while PAHs were analyzed using gas chromatography-mass spectrometry. Calibration standards and quality control samples were run alongside the sample analysis to ensure accuracy and precision. Analytical methods for the analysis and health risk assessment methods are found in the Supplementary Material Text S1–S2.

Quality control measures were rigorously applied during the experiments, which utilized high-grade analytical reagents from BDH Chemical Ltd, UK, and Sigma-Aldrich Chemie GmbH, Germany. Containers were thoroughly cleaned using detergents and deionized water, followed by overnight soaking in a solution of 10% HNO₃ and 1% HCl, and then extensively rinsed with deionized water. Anion concentration determinations were carried out using reagents from Hanna Instruments with the Hanna Hi 83,200 instruments. Soil samples and reagents were precisely weighed using a Shimadzu AW 320 analytical balance. The extraction processes were performed with a Yamato Scientific RE201 rotary evaporator. To ensure reliable analytical results, stringent quality assurance protocols were observed, including the proper calibration of laboratory instruments before analyses. Accuracy and precision were verified through duplicate analyses of samples against standard reference materials, and blank samples were included in the analysis process to maintain data integrity.

The physicochemical properties of the analyzed groundwater samples were compared with World Health Organization (WHO) standards and are presented in Table 1. The water temperature falls within the range of 20–30°C. Dissolved oxygen (DO) refers to the oxygen present in dissolved form in water bodies, and in this study, DO levels ranged from 4.32 to 5.04 mg/L, respectively. The electrical conductivity (EC) measurements in this study were all below the WHO standards, ranging from 0.98 to 32.14 mg/L. pH value is a crucial factor affecting the taste of water and can also indicate potential corrosion issues arising from the dissolution of metals such as copper, zinc, and cadmium in water (Itodo et al. 2018). The slight increases observed in both DO and pH during this study may suggest that both parameters are influenced by similar human activities in the study areas. These observations are consistent with findings at the Orji Mechanic Village, where the levels of DO fell below the standards set by the WHO (WWQA 2021).

Table 1

Mean physicochemical parameters and metal concentrations in groundwater at the areas of the study location

Parameters .	A .	B .	C .	Dcontrol .	Econtrol .	WHO .
Temp.	25.31	25.19	25.22	26.31	26.08	20–30
DO (mg/L)	5.02	4.89	5.04	4.32	4.48	10
EC (μS/cm)	1.10	1.08	0.98	30.71	32.14	2500
pH	7.04	7.02	7.03	6.21	5.91	6.5–8.5
TDS (mg/L)	0.63	0.63	0.67	20.12	20.49	500
Col (PCU)	8.22	8.63	8.44	8.03	8.21	15
Hardness (mg/L)	20.32	20.22	20.24	27.42	26.81	200–500
Alkalinity (mg/L)	16.57	16.56	16.49	5.41	25.62	120
Acidity (mg/L)	17.81	17.56	17.47	15.41	15.55	6.5–9.2
	3.97	3.96	3.84	10.31	10.82	50
	4.52	4.56	4.88	2.31	2.82	1.0
	2.46	2.25	2.62	1.42	2.03	250
Ca (mg/L)	4.05	4.02	4.06	5.02	4.87	75
Na (mg/L)	0.18	0.19	0.17	7.11	7.32	200
K (mg/L)	3.27	3.26	3.27	4.83	4.77	20
Fe (mg/L)	0.005	0.004	0.005	0.24	0.21	0.3
Cu (mg/L)	0.016	0.014	0.015	0.01	0.00	2.0
Cd (mg/L)	0.019	0.020	0.018	0.001	0.001	0.003
Co (mg/L)	0.051	0.049	0.052	0.002	0.002	0.5
Ni (mg/L)	0.016	0.015	0.015	0.0	0.0	0.02
Cr (mg/L)	0.002	0.003	0.002	0.05	0.07	0.05
Mn (mg/L)	0.063	0.062	0.062	0.05	0.05	0.4
Zn (mg/L)	0.556	0.562	0.554	0.0	0.0	3.0
Pb (mg/L)	0.004	0.006	0.003	0.00	0.00	0.01

Parameters .	A .	B .	C .	Dcontrol .	Econtrol .	WHO .
Temp.	25.31	25.19	25.22	26.31	26.08	20–30
DO (mg/L)	5.02	4.89	5.04	4.32	4.48	10
EC (μS/cm)	1.10	1.08	0.98	30.71	32.14	2500
pH	7.04	7.02	7.03	6.21	5.91	6.5–8.5
TDS (mg/L)	0.63	0.63	0.67	20.12	20.49	500
Col (PCU)	8.22	8.63	8.44	8.03	8.21	15
Hardness (mg/L)	20.32	20.22	20.24	27.42	26.81	200–500
Alkalinity (mg/L)	16.57	16.56	16.49	5.41	25.62	120
Acidity (mg/L)	17.81	17.56	17.47	15.41	15.55	6.5–9.2
	3.97	3.96	3.84	10.31	10.82	50
	4.52	4.56	4.88	2.31	2.82	1.0
	2.46	2.25	2.62	1.42	2.03	250
Ca (mg/L)	4.05	4.02	4.06	5.02	4.87	75
Na (mg/L)	0.18	0.19	0.17	7.11	7.32	200
K (mg/L)	3.27	3.26	3.27	4.83	4.77	20
Fe (mg/L)	0.005	0.004	0.005	0.24	0.21	0.3
Cu (mg/L)	0.016	0.014	0.015	0.01	0.00	2.0
Cd (mg/L)	0.019	0.020	0.018	0.001	0.001	0.003
Co (mg/L)	0.051	0.049	0.052	0.002	0.002	0.5
Ni (mg/L)	0.016	0.015	0.015	0.0	0.0	0.02
Cr (mg/L)	0.002	0.003	0.002	0.05	0.07	0.05
Mn (mg/L)	0.063	0.062	0.062	0.05	0.05	0.4
Zn (mg/L)	0.556	0.562	0.554	0.0	0.0	3.0
Pb (mg/L)	0.004	0.006	0.003	0.00	0.00	0.01

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TDS values ranged from 0.62 to 20.49 mg/L, with higher concentrations recorded in the control samples. Watercolor plays a significant role in its appearance, taste, and overall drinkability. The color of water samples at all sampling locations remained below the permissible limit, ranging from 8.03 to 8.63 Platinum-Cobalt Unit (PCU). Alkalinity measures water's acid-neutralizing capacity, acting as a buffer against abrupt shifts in pH, and its assessment depends on the specific chemical composition of the sample. Groundwater alkalinity in this study varied from 5.41 to 25.62 mg/L, contrasting with the WHO standard of 120 mg/L. Hardness, associated with high mineral content in water, occurs when water filters through calcium (Ca)- and magnesium-rich formations such as limestone, chalk, or gypsum. Water hardness ranged from 20.22 to 27.42 mg/L, indicating no pollution of groundwater with regards to hardness. Water acidity, reflecting its capacity to react with a strong base up to a specific pH value, was observed to be between 15.41 and 17.81 mg/L, consistent with previous research by Ward et al. (2020) and Birhanu et al. (2021).

⁠, a stable form of nitrogen, was consistently detected in the groundwater samples. Nitrate levels were found to be lower than the WHO Standard for safe drinking water, ranging from 3.84 to 10.82 mg/L. Phosphorus was a crucial nutrient responsible for the fertility and productivity of fishponds, particularly in supporting plankton growth (Francis et al. 2021; Hu et al. 2014). levels in this study ranged from 2.31 to 4.56 mg/L. The higher levels observed may be attributed to the frequent use of phosphate-based fertilizers by farmers in the study area. values, ranging from 1.42 to 2.46 mg/L, were observed in this study, and are below the WHO Standards for drinking water and domestic water use. Similar findings regarding sulfate levels were recorded in a study conducted in the Niger Delta area in Nigeria (Akakuru et al. 2022). This result agrees with the outcome of the result obtained from sub-Saharan Africa (Banks et al. 2021). Fe levels observed in this study, ranging from 0.004 to 0.24 mg/L, are within the range of the WHO Standards. The presence of Fe in all the samples could be attributed to the use of Fe coagulants in the area. Cu, an essential nutrient, and potential drinking water contaminant (Joshua et al. 2016), was detected at levels below the WHO Standards for drinking water and domestic use in this study, with concentrations ranging from 0.00 to 0.015 mg/L. The low Cu levels align with findings from a study conducted in European groundwater (Bunting et al. 2021) and a similar study on Owerri municipality and environs, southeastern Nigeria (Ibe et al. 2020). Cd, Co, Ni, Ch, Mn, Zn, and Pb were all found to be below significant levels and within the permissible limits set by WHO.

The WQI values reveal a spectrum of water quality ranging from 29.02 to 134.78, reflecting the diverse environmental conditions in this study area. Notably, these values collectively indicate that the overall water quality is predominantly poor, showing the pressing need for heightened environmental management efforts. Specifically, the presence of poor water quality is evident in samples A, B, and C, which are situated in regions associated with various human activities and potential sources of pollution. These activities, coupled with the possibility of oil spillage in proximity to the sampling points, contribute to the degradation of groundwater quality in these areas. The calculated WQI values for these locations fall within the higher range, emphasizing the urgency of implementing targeted mitigation measures to address the contamination. Samples D and E provide a stark contrast, boasting excellent water quality with WQI values ranging from 29.02 to 33.47. To summarize this point, the computation of the WQI highlights the varying degrees of water quality across the sampled locations. While samples A, B, and C exhibit poor water quality, attributed to a range of anthropogenic and environmental factors, samples D and E shine as beacons of excellence, showcasing the availability of uncontaminated groundwater resources. This result is shown in Table 2.

Table 3 presents the HQ values for potential non-carcinogenic risk (CR) associated with each HM in both adults and children, as well as the cumulative HI. The HQ values are indicative of the relative health risk posed by individual HMs through dermal absorption (HQ_derm) and oral ingestion (HQ_ing). For Fe, the HQ values ranged from a minimum of 7.30 × 10⁻⁹ (in adults through dermal absorption) to a maximum of 4.11 × 10⁻⁵ (in adults through oral ingestion) which indicate low hazard. Cu showed very low HQ values, often reaching zero, indicating minimal non-CR for both adults and children. Cd displayed slightly higher HQ values but remained within an acceptable range, suggesting limited non-CR. Co exhibited higher HQ values, especially in adults, implying a somewhat higher non-CR. Ni had extremely low HQ values, often at zero, indicating minimal non-CR. Cr displayed moderate HQ values, indicating a relatively higher potential non-CR. Mn exhibited HQ values within an acceptable range, signifying limited non-CR. Zn consistently showed very low HQ values, often at zero, suggesting minimal non-CR. Pb displayed HQ values within an acceptable range, indicating limited non-CR. It is important to highlight the decreasing order of HQ values for both children and adults, which ranged from Co > Pb > Cr > Cd > Mn > Zn > Co > Ni > Fe. This ranking provides insights into the relative levels of risk associated with each trace metal, with Co presenting the highest potential risk and Fe the lowest, for both age groups. The cumulative HI for all HMs in both adults and children was below one, suggesting that the combined non-CR posed by these metals was minimal and unlikely to result in significant adverse health effects in the studied populations.

The CR of Pb on the ground samples was calculated for both adults and children due to the unavailability of slope factors for other HMs in the literature. In the study, the average levels of CRing for Pb show 0.81⁻⁵ and 2.21⁻⁵ for adults and children. Under extreme regulatory programs, the CR values between 10⁻⁶ and 10⁻⁴ for an individual show potential risk; therefore, the results in this study showed that the level of Pb in the groundwater does not pose a CR to both adults and children. It is important to consider the long-term effects of chronic exposure, particularly given the cumulative nature of these contaminants. Although, the current CDI and CR values for the studied metals suggest that the immediate health risks are low, especially regarding Pb, the possibility of bioaccumulation over prolonged periods cannot be ignored. This is mostly concerning for children, who are more vulnerable to the adverse effects of HMs due to their developing systems and higher relative intake of water (Ibe et al. 2023). The absence of slope factors for other HMs in the literature should not be misconstrued as an indication of safety; rather, it highlights a critical gap in our understanding that warrants further investigation.

Table 4 presents the mean levels of the concentration of PAHs in the groundwater samples from different sampling points, including A, B, C, D (Control), and E (Control). Naphthalene, a common PAH, was detected in samples A, B, and C, with concentrations ranging from 0.1838 to 0.1975 mg/kg. Dibenzyl (a–h) anthracene was also present in these samples at similar concentrations. Fluorene was detected in samples A, B, and C, with concentrations around 0.25 mg/kg, while sample E had a minor presence of 0.0117 mg/kg. Acenaphthene and 1–2 benzanthracene were found in trace amounts in samples A, B, and C. Benzo (a) pyrene, a well-known carcinogenic PAH, was detected in all samples, with concentrations ranging from 0.0515 to 0.0536 mg/kg. Chrysene, another potentially harmful PAH, was present in all samples, with variable concentrations. Benzo (g-h-i) perylene and benzo (k) fluoranthene were also detected in samples A, B, and C. Acenaphthylene was detected in sample B, while pyrene and phenanthrene were found in samples C and D. Flouranthene was detected in sample E. The mean PAH levels observed in the study are in the order of Flu > Nap > DaA > BgP > Chr > Ace > BzA > Bkf > Acy > Phe > Flo > Pyr. Overall, the mean concentrations of PAHs varied among the sampling points, with samples A, B, and C generally showing higher levels of several PAH compounds compared to the control samples D and E. These findings indicate the potential presence of PAH contamination in the groundwater of the study area, with certain compounds at levels of concern, particularly benzo (a) pyrene. Monitoring and further investigation are warranted to assess the environmental and health implications of these PAHs in the groundwater. Elevated levels of fluorene, naphthalene, and dibenzyl (a–h) anthracene were detected in nearly all the sampling points. Additionally, the occurrence of pyrene (Pyr), phenanthrene (Phe), fluorene (Flu), and acenaphthylene (Acy) was observed to be relatively low.

The results revealed total BaPeq (mg/kg) values spanning from = 2.74⁻¹ for A, 2.80⁻¹ for B, 2.82⁻¹ for C, 2.64⁻³ for D, and 1.22⁻⁵ for sample E. It is worth noting that atmospheric sedimentation could contribute to the presence of PAH concentrations in seemingly unpolluted areas due to economic and other human activities (Bhattacharya et al. 2020; Olayinka et al. 2018). Furthermore, the elevated concentrations of PAHs in the primary study sites may be linked to recurrent local flooding events. This region experiences frequent heavy rainfall, leading to water overflow and extensive flooding, which results in significant leaching and erosion of topsoil particles containing accumulated PAHs and crude oil spillage (Ugochukwu & Ochonogor 2018). Consequently, these PAHs are distributed to floodplains and other low-lying areas. The carcinogenic potency is presented in Table 5. LMW PAHs such as naphthalene exhibit minimal carcinogenic potential (Toxic Equivalence Quality Factor (TEQF) of 0.001), while higher molecular weight PAHs such as dibenz(a,h)anthracene and benzo(a)pyrene, with five or more rings, show significantly higher potencies (TEQF of 1.00). Intermediate weights such as fluorene, acenaphthene, and chrysene have moderate TEQFs, indicating a corresponding CR. The BaPeq values, which aggregate the carcinogenic potential of all PAHs present, suggest that samples A, B, and C have a higher CR compared to the negligible levels in control samples D and E. This indicates potential environmental contamination in the study area, necessitating careful monitoring and possibly intervention to mitigate the associated health risks. Unlike previous studies of soil PAHs in the metropolitan area, the present investigation identified a high-risk level in the study area (Zheng et al. 2018; Xu et al. 2021).

The higher BaPeq levels in samples A, B, and C, particularly those with higher concentrations of HMW PAHs such as dibenz(a,h)anthracene and benzo(a)pyrene, show the significant carcinogenic threat these areas face. The disparity between these samples and the lower BaPeq values in control samples D and E highlights the extent of limited contamination, likely aggravated by the unique environmental conditions of the region, such as recurrent flooding and oil spillage. Moreover, the presence of these contaminants in groundwater, a critical resource for both drinking and agricultural activities, raises serious public health concerns, as seen in Table 5. The results suggest that the environmental dynamics of the area, combined with anthropogenic activities, are contributing to a heightened CR that warrants immediate attention.

Sample A exhibits a moderate SAR of 6.31. This SAR value suggests that the water contains a notable amount of Na ions relative to Ca and magnesium ions. Such conditions can potentially lead to the modification of soils, affecting soil structure and crop growth. Sample B, while still indicating a Na hazard, exhibits a relatively lower SAR of 4.42 compared to Sample A. This suggests a reduced risk of soil sodification when using this water for irrigation. In contrast, Samples C, D, and E have notably lower SAR values (2.36, 0.65, and 0.66, respectively). These lower SAR values imply a lower Na hazard in these samples, making them more suitable for irrigation without the significant risk of soil sodification.

Sample B presents a strikingly high MAR of 52.27. This MAR value indicates a considerable presence of magnesium in the water, which can adversely affect soil structure and permeability. Farmers using this water should be cautious about potential soil issues. In contrast, the other samples have substantially lower MAR values, signifying a diminished concern regarding excessive magnesium content in the water.

Sample A records the highest %Na at 55.61. This figure denotes that more than half of the cations in the water are Na ions. High %Na values can have a pronounced impact on soil structure, potentially leading to soil dispersion and reduced infiltration rates.

Sample B displays an extremely negative RSC value of −53.36. This strongly negative RSC indicates a significant potential for soil alkalinity, which can adversely affect soil health and crop growth. Conversely, the other samples exhibit less negative or even positive RSC values, implying a lower risk of soil alkalinity.

Sample A's high PI of 50.31 suggests that this water may not be suitable for sodium-sensitive soils. It implies that water with such characteristics could potentially compromise soil structure and restrict water infiltration. In contrast, the other samples possess lower PI values, indicating a better suitability for a broader range of soils.

Sample B stands out with the highest SSP of 52.62, suggesting a substantial Na hazard concerning all cations present in the water. Farmers should exercise caution when considering this water source for irrigation. The other samples present lower SSP values, indicating a comparatively lower Na hazard among all cations.

In this study on ecological risk assessment conducted in Imo State, Nigeria, we examined the presence of HMs and PAHs in groundwater from areas impacted by crude oil pollution. Our investigation revealed the widespread presence of these pollutants across all sampled locations, including control samples, although the control samples exhibited limited PAH presence. Our findings showed that high- fertilizers in farmlands have been used in the sampling points, which contributed to the elevation of levels that is higher than the WHO Standards. Despite being categorized as poor quality by the WDI calculations, the groundwater samples are still deemed safe for drinking purposes. The HQ and health HI, considering both ingestion and dermal exposure, indicated values within acceptable ranges for both adults and children. The notable elevation in PAH concentrations within the study locations may be closely tied to the region's susceptibility to flooding due to intense rainfall events. This recurring phenomenon leads to water overflow and substantial flooding, resulting in significant leaching and erosion of topsoil particles that carry deposited or accumulated PAHs, along with potential crude oil spillage. It is noted that Flu, Nap, and DaA levels were consistently high across all the sampling points, showing the significance of these PAHs in the studied area's environmental dynamics. The irrigation quality assessment of the investigated water sources revealed varying levels of Na and magnesium hazards, alkalinity potential, and Na dominance. These findings show the importance of considering crop and soil requirements when selecting irrigation water sources and the potential need for mitigation strategies to address water quality challenges. These findings collectively emphasize the need for continuous monitoring and proactive environmental management strategies to mitigate the impact of pollutants in the region and safeguard public health. Together, these findings emphasize the need for continuous monitoring and proactive environmental management to reduce the impact of pollutants in these areas and for public health concerns.

The authors acknowledge and appreciate Springboard Laboratories for their research assistance. We also appreciate Mr Maxwell of Alvan Ikoku College of Education for his assistance during the field analysis.

I.S.C. conceptualized the whole article, developed the methodology, software, and validated the process, rendered support in formal analysis, wrote the original draft, wrote the review and edited the article. C.A.J. rendered support in formal analysis, wrote the review and edited the article. J.N. rendered support in formal analysis, wrote the review and edited the article. C.E.E. developed the methodology, software, and validated the article, rendered support in formal analysis, wrote the review and edited the article.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.