Polycyclic aromatic hydrocarbons (PAHs) in crude oil-contaminated water and soil and their removal using locally available plant materials

Crude oil processing releases substances that can affect humans, plants and aquatic organisms if ingested through drinking water, consumption of plants through the food chain or inhalation. Most of the crude oil constituents and byproducts are categorized as persistent organic pollutants (Jacquin et al. 2017). The pollution of water bodies in Nigeria was commonly caused by oil spills. This affects vital ecosystem balance such as nutrient recycling and water purification processes (Akpan & Bassey 2020; Erwin et al. 2023). In Nigeria, a substantial number of activities that affect the ecosystem occur regularly, especially in the Niger Delta region. This includes waste discharged from industries, flaring of gases and water and soil pollution which cause health challenges (Ite et al. 2018). The natural environment contaminated by the spillage of oil is very difficult to remove from marshes and mangroves (Wali et al. 2019). The oil spill causing the contamination of environmental media (soil, water, and air) has been linked to respiratory challenges, such as cancer risk, skin diseases, and gastrointestinal disorders for the residents (Kuppusamy et al. 2020; Onyena & Sam 2020). Toxic effects, such as asphyxiation of plants and death of organisms, may occur, if it contains a high amount of light aromatic hydrocarbons (Linden & Jonas 2013).

The pollution of surface water bodies has led to a decrease in the quantity of fish, aquatic animals, and species . Aquatic animals not trapped by the pollutants migrate away from more polluted areas to less polluted areas of the water body. When crude oil contaminates water bodies, micro-organisms migrate to the uncontaminated areas (Omozue 2021). This causes economic hardship for fishermen (Iwubeh et al. 2020). Plants cannot move in most cases and get destroyed, thereby putting the ecosystem in a state of disequilibrium. The wastewater, heavy metals, and toxic chemicals discharged due to crude oil processing and agricultural practices contributed to the quality issues of the water. These further complicate the sustainable treatment and remediation of water systems (Eyankware et al. 2021).

Polycyclic aromatic hydrocarbons (PAHs) are toxic, mutagenic, teratogenic, and carcinogenic (USEPA 2009). PAHs in the soil can be encapsulated in minerals, and are present in non-aqueous liquid, which can serve as a route for human exposure (Tarafdar et al. 2018). Other sources are industrial activities, vehicular emissions, horticultural composts, and the combustion of fossil fuels (Kumar et al. 2020; Ambade et al. 2021). The presence of PAHs everywhere stimulated research interest in different remediation techniques (Gan et al. 2009).

The low-molecular-weight (Lmw) PAHs in contaminated soils have a half-life of 5–7 years while the high-molecular-weight (Hmw) PAHs have a half-life of 9–10 years (Wild et al. 1991). There is a need to remove PAHs from contaminated soils because of adverse human health effects associated with its ingestion (Haritash & Kaushik 2009). Degradation of PAHs by chemical oxidation has been used as an effective method of remediation of the soil. Permanganate ion is a strong oxidant for organic contaminants that can break the double bonds present in PAH structure (Ferrarese et al. 2008; Brown et al. 2003). The oxidants (Fenton reagents) can rapidly remove PAHs in soils (Lindsey et al. 2003; Yap et al. 2011).

PAHs are chemically stable and not biodegradable. The tendencies to cause cancer of the lung, bladder, and skin make the need to determine PAH levels in water, soil and air very important. The route and frequency of exposure go a long way in determining the severity of adverse effects (Yu et al. 2018). PAHs in water should not exceed 0.01 μgL⁻¹ and they should be considered priority pollutants in drinking water (Wang et al. 2007; Ma et al. 2020). Sources of PAHs in water could bepetroleum spills, fuel combustion, run-off from roads, creosote-coated wood leachate, and effluents from industries (Fouad et al. 2022; Mojiri et al. 2019).

Ruptures of old pipes have been recorded severally in the B-Dere community and the odor of the oil can be perceived some distance away from the spill location. Gokana and B-Dere people have protested oil spills for affecting their source of livelihood (Wizor & Eludonyi 2020).

Many varieties of sorbent materials have been used for the removal of oil by absorption or adsorption. Synthetic, inorganic, and organic materials are effective with one or more drawbacks. Synthetic materials, such as polyurethane and butyl rubber, are non-biodegradable causing environmental challenges. Fouling occurs in clay and zeolites when used as adsorbent materials for oil because of water absorption in their matrices (Al-Jammal & Juzsakova 2017; Kumar et al. 2021). The used agro-based materials, such as rice husk, corn cobs, and silica, have been effective. It is necessary to further explore extracts from plant materials because of their low cost and environmental degradability.

This study aimed to determine environment-friendly ways of removing PAHs in contaminated water and soil of a rural community. Garlic and Moringa seed extracts were used to remove PAHs from water, while garlic and Fento reagents were used to remove them from the soil of the study area.

The study area is the B-Dere community in the Gokana Local Government Area of Rivers State, Nigeria. The town covers an area of 963 square kilometers. It is one of the many communities that are affected by the oil spillage problems in Ogoni land. B-Dere, Gokana, Nigeria is only 20 meters 65.62 feet above sea level. It is a coastal community which is affected by heavy flooding. Most inhabitants are fishermen and because of the availability of dryland within the vicinity, when the sea level rises, most coastal communities around the area relocated to B-Dere. It is located between Longitude 3°48′ 84″ E – Latitude 5°17′ 87.5″N and Longitude 3°77′ 86″ E – Latitude 5°25′92″N (Figure 1). Oil spillage in the area impacts negatively on the adjoining creek which rendered large agricultural land unsuitable for the intended use (Weli & Arokoyu 2014).

All reagents used for preparations are of analytical grade which require no further purification. The water used was doubly deionized water using a Millipore purification system (Millipore, France). The Fenton reagents used are Hydrogen peroxide (50%) and iron (II) sulfate (0.1%) (Akpoveta et al. 2018).

Garlic and moringa seeds were obtained from the market and identified by the plant expert from the School of Agriculture of the University. The garlic was washed and rinsed with distilled water before blending to extract its water content. The water was filtered using filter paper and kept in the refrigerator. The moringa seed shell was removed and 10 g of the seeds were soaked in 250 mL of distilled water for 6 h. 300 mL of contaminated water sample was added to100 mL of the plant extracts and the mixture was shaken on a rotary shaker for 15 min at 105 cycles per minute (Hussein et al. 2011; Idris et al. 2014).

A standard method was used for the liquid–liquid PAH extraction with a mixture of dichloromethane and n-hexane. The extraction was carried out using Moringa seed extract (250 mL) and garlic extract (250 mL), respectively. It was shaken rigorously with the addition of a 100 mL mixture of dichloromethane and n-hexane.

20 mL of garlic and 20 mL of Fenton reagents were added, respetiely to 2 g of soil in each beaker. They were mixed and allowed to settle. The reagents were optimized following Akpoveta et al. (2018). The sample was filtered into a clean solvent-rinsed extraction bottle, using filter paper fitted into Buchner funnels. The extract was concentrated to 2 mL by freeze drying and then transferred for cleanup/separation.

10 mL of dichloromethane was added to 2 g of the soil, mixed, shaken on a rotary shaker and filtered using Buchner funnels (Lau et al. 2010). The extract was concentrated to 2 mL and then transferred for cleanup.

An optimized solid phase extraction (SPE) was used to co-extract PAHs from the matrix of Moringa extract and garlic extract, respectively. The column was first conditioned with dichloromethane and n-hexane, while the plant extracts were loaded on a normal phase column (–NH₂ and Alumina) (Blasco et al. 2007). 2 mL of hexane was used to elute the PAHs from the column.

PAH analyses were carried out using a gas chromatograph (GC/MS, Agilent, 7890 series, USA). The flow rate was set at 1.5 mL/min with nitrogen as the carrier gas. The oven temperature was set at 80 °C, holding time of 0.5 min; ramped 80–220 °C at 20 °C/min, then 220–300 °C at 10 °C/min.

The double-distilled water samples were spiked with 16 PAHs and extracted. The results were validated through recovery studies.

Principal components analysis (PCA) was used for data evaluation of PAH sources in water and soil samples. Varimax rotation and eigenvalue of 1 were used to reduce a set of original data.

• (i) The %PAHs removed was calculated by

  

  (1)

  where C_i is the mean concentration of PAHs in the raw water and C_f is the mean concentration after treatment.
• (ii) The tendency of BaP to cause cancer was calculated using (BaP_TEQ):

  

  (2)

  where BaP_TEF is the cancer potency relative to BaP and C_i is the individual PAH concentration
• (iii) The BaP mutagenic equivalency factor (BaP_MEQ) for the PAHs was evaluated sing the following Equation:

  

  (3)

  where BaP_MEF is the mutagenic potency factor while C_i is the PAH concentration.

• (iv) Incremental Lifetime Cancer Risk (ILCR)

The percent PAHs recovered was explained under recovery studies while physicochemical parameters, such as pH, temperature, and conductivity of both water and soil, were discussed under various headings (Tables 1 and 3). The range of concentration of PAHs in water and soil is presented in Tables 2 and 4. The source identification of PAHs and lifetime risk are discussed in Table 5 and 6, respectively. The results of treatment with moringa, garlic, and fento-oxidation reagents are presented in Table 7.

The results from recovery studies showed that percentage recovery of naphthalene, acenaphthylene, biphenylene, acenaphthene, fluorene, anthracene, phenathrene, pyrene, tryphenylene, benz(a)anthracene, benzo (e)pyrene, benzo(b)fluorothane, benzo(ghi)perylene, and BbT are 90.3 ± 1.79%, 90.1 ± 2.16%, 91.7 ± 2.61%, 90.3 ± 1.55%, 91.8 ± 2.12%, 90.9 ± 2.83%, 94.2 ± 1.8%, 92.1 ± 1.71%, 89.9 ± 1.02%, 91.6 ± 2.03%, 93.31 ± 2.03%, 95.1 ± 1.94%, 94.3 ± 1.04%, and 92.7 ± .04%, respectively, while the limit of detection ranged between 0.02 and 0.1. Kabzinski et al. (2002) reported a higher percentage recovery value for phenathrene and similar values for other PAHs. SPE and reverse-phase high-performance chromatography (RHPLC) were used to achieve the results.

The pH recorded from B-Dere, Gokana Creek water ranged from 6.5 to 7.1 with an average value of 6.7 ± 0.11 while the temperature ranged from 28.5 to 30.5 °C with an average value of 29.6 ± 0.35 °C (Table 1). The pH range is in agreement with Nkpa et al. (2013), who studied crabs and shrimps in Bodo City, B-Dere, and Kaa river water and reported a similar range of values. Electrical conductivity recorded in the water ranged from 102.5 to 206.1 μSCm⁻¹ with an average value of 159 ± 21.3 μSCm⁻¹. The low value of conductivity implies lower mineralization of organic matter in the water (Abida & Harikrishna 2008). Alkalinity ranged from 121 to 140 mgCaCO₃L⁻¹ with an average value of 129 ± 3.59 mgCaCO₃L⁻¹. Total hardness ranged from 120.9 to 140.1 mgL⁻¹ with a mean value of 131.1 ± 7.83 mgL⁻¹.

Chloride concentration ranged from 255.8 to 350.7 mgL⁻¹ with a mean value of 301.9 ± 35.9 mgL⁻¹. All chloride concentrations are above the WHO limit in drinking water. This is in agreement with Oladimeji et al. (2009). The TDS concentration ranged between 50.3 and 105.4 mgL⁻¹ with a mean value of 86.9 ± 10.1 mgL⁻¹ which was below the WHO limit. Extremely high TDS concentrations can cause depletion of oxygen, affect the growth of many aquatic lives and can even cause their death.

The naphthalene (Nap) concentration in water ranged from 7.01 to 7.03 ngL⁻¹ with a mean value of 7.02 ± 0.006 ngL⁻¹. Acenaphthylene (Acy) ranged from 10.80 to 10.84 ngL⁻¹ with an average value of 10.8 ± 0.012 ngL⁻¹ (Table 2). Grmasha et al. (2024) reported a higher range of naphthalene and acenaphthylene in the Danube river, Budapest.

Biphenylene (Bip) ranged from 10.88 to 10.91 ngL⁻¹ with an average value of 10.9 ± 0.009 ngL⁻¹. Acenaphthene (Ace) ranged from 11.37 to 11.41 ngL⁻¹ with an average value of 11.4 ± 0.012 ngL⁻¹. Fluorene (Flu) ranged from 12.61 to 12.64 ngL⁻¹ with an average value of 12.6 ± 0.009 ngL⁻¹. Anthracene (Ant) ranged from 14.97 to 15.02 ngL⁻¹ with an average value of 14.9 ± 0.015 ngL⁻¹. Phenanthrene (Phe) ranged from 15.01 to 15.12 ngL⁻¹ with an average value of 15.1 ± 0.035 ngL⁻¹. Munyengabe et al. (2017) reported Phenathrene with a higher concentration value in the raw water of Msundusi River in South Africa than the results obtained from the present study. Naphthalene and Phenanthrene found in the water may be due to heavy traffic and aircraft passing through the study area. The emission produced may precipitate into the water body (Mojiri et al. 2019). Pyrene (Pyr) ranged from 18.04 to 18.08 ng/L with an average value of 18.1 ± 0.012 ngL⁻¹. Tryphenylene (Trp) ranged from 22.04 to 22.07 ng/L with an average value of 22.1 ± 0.009 ngL⁻¹. Benz(a)anthracene (BaA) ranged from 22.16 to 24.61 ngL⁻¹ with an average value of 22.9 ± 0.813 ngL⁻¹. Benzo(e)pyrene (BeP) ranged from 24.62 to 25.28 ngL⁻¹ with an average value of 24.8 ± 0.218 ngL⁻¹. Benzo(b)fluorothane (BbF) ranged from 25.28 to 27.42 ngL⁻¹ with a mean value of 26.0 ± 0.71 ngL⁻¹. Benzo(ghi)perylene (BghiP) ranged from 27.21 to 28.06 ngL⁻¹ with an average value of 27.7 ± 0.25 ngL⁻¹. Kabzinski et al. (2002) reported higher values for all the PAHs detected in the drinking water of Lodz, Poland except for Pyrene (Pyr), Phenanthrene (Phe), Benzo(e)pyrene (BeP), and Benzo(ghi)perylene (BghiP) (Table 2). Fouad et al. (2022) reported a higher value of PAHs in Shamal Helman water in Cairo, Egypt. The order of dominance is Benzo(ghi)perylene > benzo(b)fluorothane > Benzo(e)pyrene > Benz(a)anthracene > Tryphenylene > Pyrene > Phenathrene > Anthracene > Fluorene > Acenaphthene > Biphenylene > Acenaphthylene > Naphthalene. The light PAHs are found in all the water samples due to their hydrophilic nature which makes them persistent; however, factors, such as aeration, absorption, adsorption, and precipitation, are also responsible (Rojo-Nieto et al. 2013). The sum of PAHs before treatment was 224.463 ngL⁻¹ which can be classified as lightly polluted (Table 2). A higher value of a sum of PAHs was reported in the rivers of Dhaka, Bangladesh (Nahar et al. 2023). Similarly, Fouad et al. (2022) reported higher values in the river of Cairo, Egypt. Surface water contaminations involving PAHs can be categorized into four, namely, micro-polluted, if PAHs concentration ranges between10 and 50 ngL⁻¹; lightly polluted, if it ranges between 50 and 250 ngL⁻¹; moderately polluted, if the range is between 250 and 1,000 ngL⁻¹, and heavily polluted if the concentration is greater than 1,000 ngL⁻¹ (Feng-Chen et al. 2020).

The pH recorded from B-Dere soil ranged from 3.7 to 6.6 with a mean value of 5.37 ± 1.49 while the percentage moisture ranged from 6.7 to 7.09% with a mean value of 6.90 ± 0.195% (Table 3). The pH range and its average value imply that the soil is acidic which may need to be limed to reduce the acidity for agricultural purposes. The soil density ranged 0.79–0.95 g/cm³ with a mean value of 0.873 ± 0.79 g/cm³.

The organic carbon ranged from 0.92 to 2.11 mg/kg with an average value of 1.527 ± 0.595 mg/kg, while the electrical conductivity ranged between 150.0 and 263.0 μSCm⁻¹ with an average value of 196.3 ± 59.18 μSCm⁻¹. Ghare & Kumbhar (2021) reported a higher pH and a lower %organic carbon in the soil of the Gujarat region of India. The organic carbon can be low, while the high electrical conductivity confers salinity to the soil as a result of the different ions present (Zeeshan et al. 2014). The percentage of sand ranged from 70.4 to 86.9% with an average value of 76.8 ± 8.85%, while the percentage of silt ranged from 0.66 to 0.78% with a mean value of 0.71 ± 0.062%. The percentage of clay ranged from 23.4 to 66% with a mean value of 44.9 ± 21.3%.

The naphthalene concentration in the soil ranged from 6.001 to 6.324 ng/g with an average value of 6.14 ± 0.163 ng/g. A higher naphthalene concentration was reported in the soil of Shatt Al- Arab, Iran (Al-Sad et al. 2019). Acenaphthylene ranged from 7.92 to 8.865 ng/g with an average value of 8.24 ± 0.439 ng/g (Table 4). Acenaphthene ranged from 9.009 to 9.563 ng/g with a mean value of 9.33 ± 0.234 ng/g.

Fluorene ranged from 8.865 to 9.857 ng/g with an average value of 9.48 ± 0.430 ng/g. Phenanthrene ranged from 10.76 to 11.24 ng/g with an average value of 10.9 ± 0.199 ng/g. Anthracene ranged from 10.5 to 11.43 ng/g with an average value of 10.98 ± 0.380 ng/g. Floranthene ranged from 11.131 to 12.872 ng/g with an average value of 11.9 ± 0.771 ng/g. Pyrene ranged from 12.952 to 13.205 ng/g with an average value of 13.02 ± 0.125 ng/g. Chrysene ranged from 13.546 to 14.945 ng/g with an average value of 14.01 ± 0.063 ng/g. Benz(a)anthracene ranged from 14.091 to 14.945 ng/g with a mean value of 14.4 ± 0631 ng/g. Natural and anthropogenically transformed coastal soils of Southern Russia showed an extremely higher value of naphthalene, floranthene, pyrene, chrysene, and benz(a)anthracene in comparison with the present study (Dudrikova et al. 2023). Some PAHs were not found in the soil sample due to possible evaporation and biological activity (Sanches et al. 2011; Ukiwe et al. 2013). The order of PAHs dominance in the soil of the study area is as follows: Benz(a)anthracene > Chrysene > Pyrene > Floranthene > Anthracene > Phenathrene > Fluorene > Acenaphthene > Acenaphthylene > Naphthalene.

The sources of PAHs in soil and water of B-Dere are mainly due to combustion as the values obtained from Ant/Ant + Phen are 0.5 and 0.498, respectively (Table 5).

The BaA/(BaA + Chry) ratio in soil samples from B-Dere was 0.5 which indicated a pyrogenic origin. The ratio >0.35 showed pyrogenic sources, while <0.20 indicated petrogenic sources (Yunker et al. 2002). The results indicated sewage deposit or compost origin. Nwaichi et al. (2020) reported lower value in the soil collected from Abuloma and Okujagu-ama, Port Harcourt, Nigeria.

The Flr/Flr + Pyr ratios in soil samples from B-Dere were 0.494, which indicated a source to be from fuel combustion, while there is no fluoranthane in the water to compute the value. The presence of PAHs in surface water is known to be caused by oil spillage, exhaust, smoke, fire, industries, and precipitation (Wang et al. 2000). The ratio (Lmw/Hmw) PAHs was 1.012 in the soil, which indicated petrogenic sources, while in water it was 0.461 which is pyrogenic. This is in agreement with the previous studies (Rocher et al. 2004).

Component 1 consists of Flu, BbF, BeA, BeP, NaP, and Bghip, which represents 59.49% of the total variance observed. Component 2 is mainly dominated by Ant, Phe, and Pyr, which represents 40.508% of the total variance observed. This further supports the possibility of petrogenic sources.

Component 1 consists of NaP, Chr, Flr, Pyr, Ant, Phe, Acy, Ace, and Flu which represents 80.631% of the total variance observed. Component 2 is mainly dominated by BaA and a few others Ace, Flu, Phe, and Ant. All thes further suggest pyrogenic sources of PAHs in the soil.

The ILCR when the soil is ingested by an adult ILCR_ing (Adult) is 1.28 × 10⁻⁷ while that of children was 1.031 × 10⁻⁶ (Table 6). The cancer risk through the dermal route (ILCR_derm (Adult)) is 1.605 × 10⁻⁷ for adults, while that of children is 2.252 × 10⁻⁶.

Nasher et al. (2013) reported a higher dermal risk value than the results from the present study. The human and animal skin sensitizers among the PAHs are anthracene and benzo(a)pyrene (IPCS 1998). If the soil dust is inhaled, the incremental lifetime cancer risk (ILCR_inh (Adult)) is 1.092 × 10⁻⁵, while that of children is 2.729 × 10⁻⁶. PAHs can enter and exit the human body through breathing , and ingestion from water, soil, and food (ATSDR 1999; Nwaichi et al. 2020). The toxicity equivalent of soil (BaP_Teq) was evaluated with BaA and Chr values of 1.495 and 0.0149, respectively, while mutagenic equivalents (BaP_Meq) are 1.225 and 0.254, respectively.

The results of PAHs in water samples showed that the ILCR when ingested by an adult ILCRing(Adult) is 2.57 × 10⁻⁷, while that of children ILCR_ing (Children) is 2.05 × 10⁻⁶ (Table 6). The dermal version of it, when the water is used to bathe (ILCR_derm (Adult)) is 1.046 × 10⁻⁹ for adults, while that of children is 4.40 × 10⁻⁶. The ILCR of PAHs through inhalation by adults (ILCRinh(Adult)) is 2.273 × 10⁻⁸, while that of children is 5.39 × 10⁻⁹. The toxicity equivalent of water (BaP_Teq) was evaluated with BaA, BaP, and BbF values of 2.22, 0.253, and 24.7, respectively, while mutagenic equivalent (BaP_Meq) was 1.829, 6.325, and 24.7 respectively. The results from the present study with respect to ingestion and dermal risk agree with the results obtained by Yao et al. (2023), in the study of Don and Tangxum lake of China.

Garlic and Moringa seed extracts were used for the treatment of water, while garlic and Fenton reagents were used for the treatment of the soil. The garlic extract removal of PAHs from water ranged between 0.14% for BbF and 100% (BaA, Tph, and BbT) (Table 7). The higher removal of BaA, Tph, and BbT is in agreement with the study of Gutierrez-Urbano et al. (2021).

Others are 0.64% NaP, 0.184% Ace, 0.734% Flu, 0.207% Ant, 0.171% Pyr, 0.28% Bip, 0.316% BeP, 0.14% BbF, and 2.5% Bghip. None of Acy and Phe is removed by garlic extract. Non-removal of phenanthrene might be due to its non-planar structure and its high stability (Rani & Shanker 2020). A higher success rate was recorded when PAH-contaminated water and soil samples were remediated using a tropical plant (Eleocharis ochrostachys) through a surface flow system (Alsbani et al. 2020). PAHs can be reduced by garlic, onions, shallots, and pepper (Neves et al. 2021). The ability to remove PAHs is due to the presence of a bioactive compound (allicin) in garlic (Janoszka et al. 2019; Saputro et al. 2022).

However, Moringa seed extract removal of PAHs ranged between 0.0001% for Bip and 100% for Bghip. Others are 0.139% Acy, 0.044% Ace, 0.126% Flu, 0.033% Ant, 0.033% Phe, 0.116% Pyr, 0.305% BaA, 0.045% Tph, 0.19% BeP, 0.059% BbF, and 0.338% BbT. Nap is not removed by the Moringa seed extract.

The results of treatment of polluted soil with the garlic extract showed removal of 1.34% NaP, 2.59% Acy, 0.429% Ace, 0.78% Flu, 0.177% Ant, 0.368% BaA, and 0.186% Flr. None of Phe, Pyr, and Chr is removed. The removal of PAHs using garlic extract acting as a chelating agent facilitates the removal of organic pollutants in the soil (Kiosnar et al. 2019).

Fenton reagents removed 1.45% NaP, 0.417% Acy, 0.265% Ace, 100% Ant, 100% Phe, 0.06% Pyr, 0.468% BaA, and 100% Chr. None of Flu and Flr is removed. The results of the percentage of PAHs removed from this study is lower than reported results from the literature (Jonsson et al. 2007; Nam et al. 2021). Phenanthrene and pyrene removal was achieved efficiently by graphene oxide-coated microbubbles (Yahya & Lau 2021). The electrophilic aromatic substitution mechanism was used to describe PAH oxidation and removal (Liu et al. 2020). Moringa seed and garlic extracts can be incorporated in water treatment that requires the removal of PAHs in water for their effectiveness in removing 100% of BaA, Tph, BbT, and Bghip.

The study investigated PAH levels in the B-Dere Community, which is an oil-producing area in Nigeria. The water and soil of the area were examined for their PAHs and their physicochemical parameters. The PAHs were removed using Moringa seed extracts, garlic extracts, and by the Fento-oxidation chemical method. The results showed that B-Dere water contained a high concentration of chloride and 13 PAHs. The order of dominance of PAHs in water is benzo(ghi)perylene > benzo(b)fluorothane > benzo(e)pyrene > benz(a)anthracene > tryphenylene > pyrene > phenathrene > anthracene > fluorene > acenaphthene > biphenylene > acenaphthylene > naphthalene. The soil contains 10 PAHs in the following order: benz(a)anthracene > chrysene > pyrene > floranthene > anthracene > phenanthrene > fluorene > acenaphthene > acenaphthylene > naphthalene. The sources of PAHs in water are pyrogenic, while those of soil are petrogenic. The lifetime risk was higher in children than in adults if the water is ingested through drinking and if the water is used to bathe. However, the incremental lifetime risk of cancer through inhalation from the soil was higher for adults than for children. Garlic extract is effective in removing benz(a)anthracene, BaA, and benzo(b)fluorothane from water, while moringa extract is effective in removing biphenylene from water. The garlic is not as effective in removing PAHs from the soil as the Fenton oxidation reagents. The community may adopt the green method of water and soil treatment described in this study for better utilization of water and soil for agricultural purposes.

There is no funding for this research work.

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

The authors declare there is no conflict.