Analysis and Sources of Polycyclic Aromatic Hydrocarbons in Soil and Plant Samples of a Coal Mining Area in Nigeria

Biosorption of potassium ion using bean seeds and its energy saving application

Ca and Mg have been implicated in causing hardness in beans resulting in relatively long cooking time. This study used potassium to replace the cations and determined the adsorption of potassium solution to bean seeds. Then, plantain peel, a natural source of potassium, was used to cook beans and its impact on the cooking time of beans was investigated. The adsorption experiments were performed using batch technique, while metal compositions of the bean seeds and plantain peel were determined by spectroscopy. Optimum removal conditions of potassium ion biosorption using bean seeds were observed at pH 10.2, 2 g bean seed dosage, 180 min agitation time, with 75 ppm as initial metal concentration. The kinetic model correlate with pseudo-second order reaction and the Langmuir adsorption model best fitted the adsorption. After cooking the beans with plantain peel, the concentration of Mg reduced in the bean seeds by about 48%, while the concentration of Ca reduced by about 22%, but the concentration of K increased by over 200% in the cooked bean seeds. Beans treated with plantain peel cooked earlier than the control experiment. This may be affected by pH, adsorbent dosage, metal concentration and contact time.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface water in the coal mining area of northern Shaanxi, China

This study investigated the spatial distribution, pollution source, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the Kuye River, which is a typical river in the mining area of China, 16 priority PAHs were quantitatively detected at 59 sampling sites by high-performance liquid chromatography-diode array detector-fluorescence detector. The results showed that the ∑PAHs concentrations in the Kuye River were in the range of 50.06-278.16 ng/L. The PAHs monomer concentrations were in the range 0-121.22 ng/L, of which chrysene had the highest average concentration (36.58 ng/L), followed by benzo[a]anthracene and phenanthrene. In addition, the 4-ring PAHs showed the highest relative abundance in the 59 samples, ranging from 38.59 to 70.85%. Moreover, the highest concentrations of PAHs were mainly observed in coal mining, industrial, and densely populated areas. On the other hand, according to the diagnostic ratios and positive matrix factorization (PMF) analysis, it can be concluded that coking/petroleum sources, coal combustion, vehicle emission, and fuel-wood combustion contributed to the PAHs concentrations in the Kuye River by 37.91%, 36.31%, 13.93%, and 11.85%, respectively. In addition, the results of the ecological risk assessment indicated that benzo[a]anthracene had a high ecological risk. Among the 59 sampling sites, only 12 belong to low ecological risk areas, and others were at medium to high ecological risks. The current study provides data support and a theoretical basis to effectively manage pollution sources and ecological environment treatment in mining areas.

Ingestion and Dermal Cancer Risk via Exposure to Polycyclic Aromatic Hydrocarbon-Contaminated Soils in an Oil-Producing Community, Niger Delta, Nigeria

There is an intrinsic link between polycyclic aromatic hydrocarbons (PAHs) accumulated in soils and increased health risk to humans after exposure to contaminated soil via ingestion, inhalation of particulates carrying PAHs, and direct contact with polluted soils. However, the assessment of PAH contamination in most developing countries fails to consider health risk assessment. Therefore, a comprehensive study was conducted to determine the concentration, source, toxicity, and human health risks of 16 PAHs in an urban area in Warri, Delta State, in the Niger Delta region of Nigeria. The results showed varying contamination levels for PAH in soil samples from all sampling points, with benzo[a]anthracene (BaP; at 338.81 μg/kg) being the most abundant at all 9 sampling stations. The highest total concentration of PAH was observed at station 5 (1230.98 μg/kg), which was closest to a flow station. Further comparison with PAH contamination standards showed that soils from stations 1 and 2 were weakly contaminated (<600 μg/kg), and soil samples from stations 3, 4, 6, 7, and 9 were moderately contaminated (<1000 μg/kg). Soil samples from stations 5 and 8 were observed to be heavily contaminated (>1000 μg/kg). The BaP estimates for soil samples obtained for stations 3 to 9 were higher than the BaP soil screening value (15 μg/kg), indicating a carcinogenic potential of soil samples. The results also showed that the incremental lifetime cancer risk estimates for PAH in the soil for adults and children were above the recommended threshold (10^-4 ) for ingestion and dermal contact, implying that exposure to contaminated soil could lead to cancers in adults and children. Currently, there are no regional or national standards for PAHs in soil that would indicate an increased likelihood for human exposure and subsequent health issues. Environ Toxicol Chem 2021;40:261-271. © 2020 SETAC.

Polycyclic aromatic hydrocarbons (PAHs) and esophageal carcinoma in Handan-Xingtai district, North China: a preliminary study based on cancer risk assessment

Extremely high risk of esophageal carcinoma (EC) occurs in Handan-Xingtai district of North China. In spite of various preventive measures and epidemiological investigations that have been conducted for years, incidence and mortality of EC are still in the highest level of China. The etiology of EC remains unclear in the region. Previous studies of our research group proposed that polycyclic aromatic hydrocarbons (PAHs) that derived from numerous coal gangue dumps and atmospheric particulates were major contaminants in these regions. In consideration of mutagenic, teratogenic, and carcinogenic characteristics of PAHs, the authors hypothesized that severe exposure to PAHs could preform as a causative factor for EC. Therefore, four data sets documented in our previous studies were employed in this paper. To quantitatively evaluate the carcinogenic risk imposed by sixteen priority PAHs, incremental lifetime cancer risks (ILCRs) via three exposure pathways were calculated. The results showed that total ILCRs for adult group ranged from 2.08E-05 to 8.63E-02, with an average of 2.00E-02. Total ILCRs for childhood group ranged from 1.09E-05 to 4.48E-02, with an average of 1.04E-02. Total ILCR value of 94% samples exceeded 10^-4, indicating a particularly high carcinogenic risk to local residents. Furthermore, ingestion and dermal contact conducted as principal pathways of exposing to PAHs for each population group, rather than inhalation. It can be speculated that severely exposing to PAHs may be a pathogenesis of EC in Handan-Xingtai district. The rigorous supervise and governance are imperative to avoid severe exposure to PAHs that derived from coal gangue dumps.

Human exposure risk to semivolatile organic compounds via soil in automobile workshops in Awka, South Eastern, Nigeria

Evaluation of the human exposure risk to semivolatile organic compound (SVOC) levels in soil from automobile workshops in Awka was investigated. Soil samples were collected in both dry and rainy seasons. Solvent extraction of the soil samples was carried out using n-hexane: acetone mixture (1:1). Concentrations of SVOCs were determined using gas chromatography-mass spectrometry. There were higher concentrations of SVOCs in the dry season than in the rainy season. The concentrations of the SVOCs were compared with standards for industrial soils. Concentrations of pentachlorophenol in the samples for dry and rainy seasons were below the Canadian Council of Ministers of Environment (CCME) acceptable limit of 7.6 mg/kg. Eighty percent of soil samples for the dry season and all the soil samples for the rainy season had benzo(a)pyrene concentrations lower than the CCME acceptable limit of 0.7 mg/kg. However, incremental lifetime cancer risk (ILCR_der) of PAHs and pentachlorophenol for dry seasons exceeded 1.0 × 10^-6 WHO acceptable limit in all the sampling stations, which indicates potential risk via dermal contact. ILCRs of pentachlorophenol were above 1.0 × 10^-6 in 60% of the samples for soil ingestion and all the samples for dermal contact. Hazard quotient of phenolics, phthalates, 1,3-dichlorobenzene and 1,4-dichlorobenzene for soil samples were less than 1 for both seasons, which indicates no non-cancer risk. Results suggest that the SVOCs were highest at the centre of the automobile workshop and the main route of exposure was dermal contact with the soil.

Health risk assessment and source study of PAHs from roadside soil dust of a heavy mining area in India

The total concentrations of 13 detected polycyclic aromatic hydrocarbons (PAHs) in different traffic soil samples of Dhanbad heavy mining area, India, were between 8.256 and 12.562 µg/g and were dominated by four ring PAHs (44%). Diagnostic ratio study revealed that fossil fuel burning and vehicular pollution are the most prominent sources of the PAHs in roadside soil even at a heavy coal mining area. The 90th percentiles cancer risks determined by probabilistic health risk assessment (Monte Carlo simulations) for both the age groups (children and adults) were above tolerable limit (>1.00E-06) according to USEPA. The simulated mean cancer risk was 1.854E-05 for children and 1.823E-05 for adults. For different exposure pathways, dermal contact was observed to be the major pathway with an exposure load of 74% for children and 85% for adults. Sensitivity analysis demonstrated relative skin adherence factor for soil (AF) is the most influential parameter of the simulation, followed by exposure duration (ED).

Polycyclic aromatic hydrocarbons (PAHs) in surface sediments near a mining site in Okobo-Enjema, Nigeria: concentrations, source apportionment and risk assessment

PAHs are pollutants of serious environmental and human health concerns. PAH studies in environmental compartments may assist in designing PAH control measures. The levels of selected PAHs in surface sediment samples of a stream near a mining site at Okobo-Enjema, Nigeria, were investigated. The data were used to determine the possible sources of the PAHs and to assess the potential health risk of the PAHs to humans which was evaluated based on the sediment quality, contamination level and cancer risk guidelines. Sediment samples were collected in replicates at various locations in the stream. A mixture of acetone, dichloromethane and n-hexane was used to extract the PAH compounds by sonication. The extracts were cleaned-up, concentrated and quantitatively analyzed using gas chromatography-mass spectrometry. The results indicated 14, 10 and 4 out of the 16 target PAHs were detected at various sampling stations. The total concentrations of the PAHs ranged from 0.09 to 1.2 mg/kg dry weight. High molecular weight PAHs dominated over the low molecular weight compounds at distances nearer to the coal mine. The PAH contamination came from pyrogenic and petrogenic sources. The results suggested that there was no eco-toxicological risk for organisms in the sediments beyond 400 m from the coal mine. The sediments were highly contaminated at ≤400 m from the coal mine; moderately contaminated at between 400 and 500 m from the mine; and lowly contaminated at beyond 500 m from the mine. The cancer risk is low on ingestion and skin contact with the sediments.

Distributions and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils around a Chemical Plant in Shanxi, China

Background: Yearly the Shanxi coal chemical industry extracts many coal resources, producing at the same time many polycyclic aromatic hydrocarbons (PAHs) that are emitted as by-products of coal incomplete combustion. Methods: Sixty-six soil samples collected from 0 to 100 cm vertical sections of three different agricultural (AS), roadside (RS) and park (PS) functional soils around a chemical plant in Shanxi, China were analyzed for the presence of the 16 priority control PAHs. Results: The total concentrations (∑16PAHs) varied in a range of 35.4–116 mg/kg, 5.93–66.5 mg/kg and 3.87–76.0 mg/kg for the RS, PS and AS surface soil, respectively, and 5-ring PAHs were found to be dominant (44.4–49.0%), followed by 4-ring PAHs (15.9–24.5%). Moreover, the average value of ∑16PAHs decreased with the depth, 7.87 mg/kg (0–25 cm), 4.29 mg/kg (25–50 cm), 3.00 mg/kg (50–75 cm), 2.64 mg/kg (75–100 cm) respectively, in PS and AS soil vertical sections. Conclusions: The PAH levels in the studied soils were the serious contamination level (over 1.00 mg/kg) according to the Soils Quality Guidelines. The carcinogenic PAHs (ΣBPAHsBapeq) were approximately 14.8 times higher than the standard guideline level (0.60 mg/kg) and 90.3% of PAHs were produced by coal/wood/grass combustion processes.