Appraisement, source apportionment and health risk of polycyclic aromatic hydrocarbons (PAHs) in vehicle-wash wastewater, Pakistan

A nature-based closed-loop wastewater treatment system at vehicle-washing facilities: From linear to circular economy

Pakistan, among the top five most water-stressed nations globally, grapples with water scarcity owing to inadequate treatment infrastructure and groundwater overextraction. We demonstrate a successful nature-based closed-loop system to treat wastewater from urban vehicle-washing facilities, previously reliant on groundwater. An eco-friendly integrated system containing floating treatment wetlands (FTWs), subsurface flow constructed wetlands (SSF-CWs), and sand filtration (SF) was designed and installed at three vehicle-washing facilities for wastewater treatment and reuse in a loop. While the system is still operational after years, a consistent and significant reduction in water quality indicators is recorded, successfully meeting the national environmental quality standards of Pakistan. By reducing per unit water treatment costs to as low as $0.0163/m³ and achieving payback periods under a year, the embrace of these closed-loop strategies vividly underscores the imperative of transitioning to a circular economy in the domains of wastewater treatment and resource conservation.

Polycyclic Aromatic Hydrocarbons in Soil and Vegetation of Niger Delta, Nigeria: Ecological Risk Assessment

The Niger Delta, Nigeria, is noted for crude oil exploration. Whereas there seems to be a handful of data on soil polycyclic aromatic hydrocarbon (PAH) levels in this area, there is a paucity of studies that have evaluated soil and vegetation PAHs simultaneously. The present study has addressed this information gap. Fresh Panicum maximum (Jacq) (guinea grass), Pennisetum purpureum Schumach (elephant grass), Zea mays (L.) (maize), and soil samples were collected in triplicate from Choba, Khana, Trans-Amadi, Eleme, Uyo, and Yenagoa. PAHs determination was carried out using GC-MS. The percentage composition of the molecular weight distribution of PAHs, the molecular ratio of selected PAHs for identification of possible sources, and the isomeric ratio and total index of soil were evaluated. Pennisetum purpureum Schumach (elephant grass) from Uyo has the highest (10.0 mg·kg^-1) PAH while Panicum maximum (Jacq) (guinea grass) has the highest PAH (32.5 mg·kg^-1 from Khana. Zea mays (L.) (maize) from Uyo (46.04%), Pennisetum purpureum Schumach (elephant grass) from Trans-Amadi (47.7%), guinea grass from Eleme (49.2%), and elephant grass from Choba (39.9%) contained the highest percentage of high molecular weight (HMW) PAHs. Soil samples from Yenagoa (53.5%) and Khana (55.3%) showed the highest percentage of HMW PAHs. The total index ranged 0.27-12.4 in Uyo, 0.29-8.69 in Choba, 0.02-10.1 in Khana, 0.01-5.53 in Yenagoa, 0.21-9.52 in Eleme, and 0.13-8.96 in Trans-Amadi. The presence of HMW PAHs and molecular diagnostic ratios suggest PAH pollution from pyrogenic and petrogenic sources. Some soils in the Niger Delta show RQ_(NCs) values higher than 800 and require remediation to forestall ecohealth consequences.

Genotoxic effects of polycyclic aromatic hydrocarbons (PAHs) present in vehicle-wash wastewater on grass carp (Ctenopharyngodon idella) and freshwater mussels (Anodonta cygnea)

Vehicle-wash wastewater (VWW) contains high levels of various petrochemicals such as polycyclic aromatic hydrocarbons (PAHs), a carcinogenic category of organic substances. However, the genotoxic effects of PAHs present in VWW remain largely unknown. We explored the genotoxic effects of PAHs present in VWW on fish grass carp (Ctenopharyngodon idella) and freshwater mussels (Anodonta cygnea). Fish and freshwater mussels were divided into control and exposed groups, the prior groups were treated at weekly intervals with clean water, and the latter with Σ16PAHs contaminated VWW for up to four weeks. The samples of blood from fish and haemolymph from freshwater mussels were collected and analyzed using the comet assay technique. Results exhibited that in control fish and freshwater mussel groups the genotoxicity decreased with every week passing following the order of W1 > W2 > W3 > W4, ranging from 8.33 ± 3.06 to 25.3 ± 4.62 and from 46.0 ± 6.93 to 7.67 ± 3.79, respectively. The exposed fish and freshwater mussel groups indicated an increase in genotoxicity with increasing week intervals with an order of W4 > W3 > W2 > W1, ranging from 55.7 ± 11.9 to 128.3 ± 10.0 and from 112.7 ± 8.50 to 183.3 ± 10.1, respectively. The genotoxic effect of Σ16PAHs on fish was comparatively lower than on freshwater mussels. This study elucidates that VWW is highly genotoxic and should be treated before discharging into aquatic ecosystems.

Sources, pollution, and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in Porto-Novo Lagoon, Benin Republic

The Porto-Novo Lagoon is influenced by agricultural discharges and human activities. In order to evaluate the impact of wastes and human activities on Porto-Novo Lagoon, the sources and ecological risks of sixteen polycyclic aromatic hydrocarbons (PAHs) were assessed. The physicochemical and biological parameters of the water were also determined. The result showed that between the sampling sites, the mean concentration of dissolved oxygen ranged from 4.8 ± 0.5 to 5.1 ± 0.2 mg/L; biochemical oxygen demand varied from 12.6 ± 2.0 to 77.9 ± 81.9 mg/L; biological oxygen demand ranged from 2.8 ± 2.6 to 5.6 ± 0.9 mg/L; total phosphorus varied between 4.7 ± 2.7 and 15.3 ± 9.5 mg/L; total dissolved solids ranged from 183.0 ± 115.8 to 337.5 ± 413.3 mg/L, and Escherichia coli varied from 495.0 ± 542.9 to 1920.0 ± 2676.5 UFC/100 mL. Water parameter values obtained were not within World Health Organization (WHO)-recommended limits except pH and TDS. Total PAHs (∑PAHs) concentration varied from 38.8 to 123.9 mg/L. The mean ∑PAH concentration was 83.2 ± 20.3 mg/L. Benzo[b]fluoranthene, benzo[g,h,i]perylene, and benzo[k]fluoranthene were the most dominant PAHs and contributed to 55.9%, 15.3%, and 4.5% of the ∑PAHs concentration, respectively. Douane-Tokpa and Djassin recorded the lowest and highest concentrations. PAHs of four to six rings were the most abundant across the sampling sites. Naphthalene showed the lowest risk in the lagoon. Acenaphthene showed low risk at Djassin, while Indeno(1,2,3 cd)pyrene showed low risk at Benin Industry Body Fat. Except for those that were not detected, all the PAHs at individual or complex mixture levels showed high risk at all the sites. The highest total concentration was recorded in Djassin followed by Beaurivage. The high level of PAHs pollution was attributed to both human and goods traffic, runoff, and the complex hotels close to the lagoon. Molecular diagnostic ratios and principal component analysis suggest that the target hydrocarbons were from both petrogenic and pyrogenic sources with predomination of vehicular emission and coal/woods combustion. ∑LWM/HWM confirmed also the predominance of pyrolytic sources of PAHs in Porto-Novo Lagoon. The predominance of the vehicular emission may be due to the position of the complex Porto-Novo Lagoon-Nokoué Lake which is between the two big cities of the country.

Simultaneously enhanced removal of PAHs and nitrogen driven by Fe2+/Fe3+ cycle in constructed wetland through automatic tidal operation

The lack of dissolved oxygen and weak substrate removal capacity in constructed wetlands (CW) leads to terrible removal of nitrogen and polycyclic aromatic hydrocarbons (PAHs). In this study, automatic tidal flow CW microcosms were constructed by improving the oxygen environment (siphon and air-duct) and substrate (magnetite) to enhance purification performance and the mechanism was explored. The results showed that the addition of air-duct could improve the oxygen collection and thus improved the NH₄⁺ removal efficiency. Additionally, nitrogen removal was improved greatly due to the simultaneous nitrification and denitrification in aerobic layer with the addition of magnetite. Mass balance indicated the microbial degradation dominated (32-62%) the removal of PAHs. Metagenomic analysis proved the existence of magnetite enhanced the number of PAHs-degrading bacteria, functional groups and metabolic pathways and thus greatly improved the microbial degradation of PAHs. Furthermore, Fe²⁺/Fe³⁺ cycle played an important role in promoting the anaerobic degradation of PAHs, which might be served as an electron conduit to establish the direct interspecies electron transfer between iron-reducing bacteria (e.g. Deltaproteobacteria bacterium) and Anaerolineae bacterium to degrade PAHs efficiently. This study provided better understanding of the simultaneous removal of PAHs and nitrogen in tidal flow CWs.

Atmospheric particle-bound polycyclic aromatic compounds over two distinct sites in Pakistan: Characteristics, sources and health risk assessment

Much attention is drawn to polycyclic aromatic hydrocarbons (PAHs) as an air pollutant due to their toxic, mutagenic and carcinogenic properties. Therefore, to understand the levels, seasonality, sources and potential health risk of PAHs in two distinct geographical locations at Karachi and Mardan in Pakistan, total suspended particle (TSP) samples were collected for over one year period. The average total PAH concentrations were 31.5 ± 24.4 and 199 ± 229 ng/m³ in Karachi and Mardan, respectively. The significantly lower concentration in Karachi was attributed to diffusion and dilution of the PAHs by the influence of clean air mass from the Arabian sea and high temperature, enhancing the volatilization of the particle phase PAHs to the gas phase. Conversely, the higher concentration (~6 times) in Mardan was due to large influence from local and regional emission sources. A clear seasonality was observed at both the sites, with the higher values in winter and post-monsoon due to higher emissions and less scavenging, and lower values during monsoon season due to the dilution effect. Diagnostic ratios and principal component analysis indicated that PAHs in both sites originated from traffic and mixed combustion sources (fossil fuels and biomass). The average total BaP equivalent concentrations (BaP_eq) in Karachi and Mardan were 3.26 and 34 ng/m³, respectively, which were much higher than the WHO guideline of 1 ng/m³. The average estimates of incremental lifetime cancer risk from exposure to airborne BaP_eq via inhalation indicated a risk to human health from atmospheric PAHs at both sites.

Utilization of activated carbon derived from waste plastic for decontamination of polycyclic aromatic hydrocarbons laden wastewater

Serious environmental deterioration caused by synthetic waste plastics, and the pollution of freshwater resources are the most alarming and marked challenges of the 21st century. Therefore, immense scientific efforts are being made towards the management of waste plastics and treatment of polluted water. The current study reports on the utilization of waste polyethylene terephthalate (wPET) and waste polystyrene (wPS) for fabrication of activated carbon (AC) and its application for the removal of hazardous polycyclic aromatic hydrocarbons (PAHs) pollutants from water. AC was prepared from wPET and wPS by carbonization under a N₂ atmosphere followed by chemical activation with 1 M KOH and 1 M HCl. The AC was characterized by scanning electron microscopy, surface area analysis, and Fourier transform infrared spectroscopy. Adsorption of PAHs from aqueous solutions through AC was examined by batch adsorption tests. The optimum parameters for maximum adsorption of PAHs were found to be: initial PAHs concentration 40 ppm, 2 h contact time, pH 3, 5, and 7, 50 °C temperature and adsorbent dose of 0.8 g. Kinetic and isotherm models were applied to evaluate the adsorbent capacity for PAHs adsorption. The kinetic study shows that the adsorption of these PAHs onto AC follows pseudo-second-order kinetics. The experimental results demonstrated that the Langmuir isotherm model best fitted the data. The thermodynamic factors calculated such as entropy change (ΔS°), enthalpy change (ΔS°) and free energy change (ΔG°) show that the adsorption process is non-spontaneous and endothermic in nature. Results were also compared with the efficiencies of some commercial adsorbents used in practice. This examination revealed that the novel plastic-derived AC possesses a great potential for elimination and recovery of PAH elimination from industrial wastewater.

Uptake, translocation, and risk assessment of PAHs in contaminated soil-air-vegetable systems based on a field simulation experiment

Vegetable consumption is a potential toxin exposure pathway for humans. Studies have recognized that vegetables can uptake organic contaminants via roots and translocate pollutants to their aerial parts. However, the aerial parts might also directly uptake polycyclic aromatic hydrocarbons (PAHs) from contaminated soils. This has not been extensively studied. The aim of this study was to explore the uptake and translocation of PAHs in contaminated soil-air-vegetable systems. Sixteen individual PAHs in contaminated soils, vegetable roots, and leaves were identified using GC-MS. The results showed that the average PAH concentrations both in roots and leaves from the reference soil, the moderately contaminated soil, and the heavily polluted soil increased as expected. PAHs with log K_OW < 5 accumulated more easily in roots and leaves. Using a Pearson correlation analysis, isomer ratios, and a principal component analysis (PCA), it was found that the contaminated soil not only caused PAH accumulation in roots, but also increased the PAH concentration in leaves. Quantitatively, the absorption of PAHs in roots in the moderately contaminated soil (70.3 ng m^-3) was approximately twice that of the reference soil (40.8 ng m^-3). The PAHs absorbed by vegetable roots in the heavily polluted soil (74.7 ng m^-3) was only slightly higher than that of the moderately polluted soil. In addition, the PAH dose volatilized into the air from the reference soil, the moderately contaminated soil, and the heavily polluted soil also showed an increasing trend. The incremental lifetime cancer risk (ILCR) indicated that adult females had a higher cancer risk via vegetable consumption than other groups. Although vegetable consumption had a slight effect on cancer risk for some groups in the present study, the cancer risk of PAHs caused by eating vegetables grown in heavily contaminated soil still requires attention.

Elevated exposure to polycyclic aromatic hydrocarbons (PAHs) may trigger cancers in Pakistan: an environmental, occupational, and genetic perspective

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds which are emitted through incomplete combustion of organic materials, fossil fuels, consumption of processed meat, smoked food, and from various industrial activities. High molecular mass and mobility make PAHs widespread and lethal for human health. A cellular system in human detoxifies these toxicants through specialized enzymatic machinery called xenobiotic-metabolizing (CYP450) and phase-II (GSTs) enzymes (XMEs). These metabolizing enzymes include cytochromes P450 family (CYP1, CYP2), glutathione s-transferases, and ALDHs. Gene polymorphisms in XMEs encoding genes can compromise their metabolizing capacity to detoxify ingested carcinogens (PAHs etc.) that may lead to prolong and elevated exposure to ingested toxicants and may consequently lead to cancer. Moreover, PAHs can induce cancer through reprograming XMEs' gene functions by altering their epigenetic markers. This review article discusses possible interplay between individual's gene polymorphism in XMEs' genes, their altered epigenetic markers, and exposure to PAHs in cancer susceptibility in Pakistan.

Environmental impact assessment of municipal solid waste management value chain: A case study from Pakistan

The present study quantified environmental impacts of the Rawalpindi Waste Management Company (RWMC) value chain in Pakistan for three consecutive years (2015-2018) using a cradle-to-grave life cycle assessment (LCA) approach. Energy potential from municipal solid wastes (MSW) was also predicted till the year 2050. Based on a functional unit of 1.0 tonne of MSW, the study analyzed inputs and outputs data through SimaPro v.8.3 applying CML 2000 methodology and cumulative exergy demand indicator (CExD). LCA revealed that operational activities of RWMC mainly contributed to marine aquatic ecotoxicity, i.e. 8962.83 kg1,4-DBeq t^-1 MSW, indicating long-range transport of petrogenic hydrocarbons from the company's fleet gasoline combustion. Similarly, human toxicity potential, global warming potential and freshwater aquatic ecotoxicity potential were also found to be significant, i.e. 18.14 kg1,4-DBeq t^-1 MSW, 15.79 kgCO₂eq t^-1 MSW and 6.22 kg1,4-DBeq t^-1 MSW, respectively. The CExD showed that company activities consumed 827.14 MJ t^-1 MSW exergy from nature, and gasoline used in MSW transport was the most exergy-intensive process, using 634.47 MJ exergy per tonne MSW disposed of. Projections for energy generation potential up to the year 2050 showed that MSW of Rawalpindi city will have the potential to produce 3901 megawatt of energy to fulfill the energy needs of the country. Possible stratagems to reduce environmental impacts from the municipal solid waste management (MSWM) value chain of RWMC include curtailing dependency on petrogenic and fossil fuels in mobile sources, optimization of waste collection methods and dumping routes, inclining attention toward suitable wastes-to-energy conversion technology and opting for a holistic approach of MSWM in Pakistan.

Comparative study of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in corals, sediments and seawater from coral reefs of Hainan, China

This work investigated levels of PAHs and HMs in fourteen species from seven genera of scleractinian corals, adjacent sediments, and surface seawater in Hainan, China. The sources of contaminations were analyzed as well. The results showed that scleractinian corals had a relatively higher bioaccumulation capacity for PAHs from sediments than for HMs. There were inter-species differences for these contaminants enriched in corals. Pavona varians and Porites lutea could accumulate PAHs more readily. While higher concentrations of Cr, Mn and Pb occurred in Favites flexuosa, other metal levels, such as for Ni, Cu, Zn and As, were found to be elevated in Pocillopora damicornis, as well as for Cd in Acropora echinata. It was found that PAHs originated from petrogenic and pyrolytic sources, and were mainly linked to onshore and on-sea activities, such as motorboats. Mn, Ni, As and Cd were from crustal materials or natural weathering, while Cr, Cu, Zn and Pb were non-crustal origin connecting with the use of anti-fouling boat paint and agricultural and/or aquacultural chemicals. This study suggested that corals could serve as good bioindicators for two types of chemical pollution in the reef system, especially for the two species P. varians and P. lutea for PAHs contaminants.

Characterization of polycyclic aromatic hydrocarbons in urban-rural integration area soil, North China: Spatial distribution, sources and potential human health risk assessment

The promotion of urbanization has accelerated the development of small manufacturing workshops and brought serious environmental problems. In this study, spatial distribution, sources and potential health risk for polycyclic aromatic hydrocarbons (PAHs) in urban-rural integration area soil in North China (800 km²) were discussed. The average total concentration of 16 PAHs was 225 μg kg^-1, and range from 25 to 15155 μg kg^-1 (n = 250). According to the European soil quality standards, more than 70% of the samples don't reach the pollution level, while around the small workshop concentration area and non-ferrous metal smelter were more contaminated than other area. The spatial distribution of soil PAHs concentration shows that low molecular weight, medium molecular weight and high molecular weight is very similar to the distribution of total PAHs, indicating that is likely to be caused by point source pollution. The sources of PAHs were identified by positive matrix factorization. The main six sources in the region are coal and biomass combustion, creosote, coke tar, vehicle and oil, which is consistent with the local energy consumption structure. Finally, a deterministic assessment of the cancer risk showed that the range for children was 5.94 × 10^-8 to 2.53 × 10^-5, and adults it ranged from 2.11 × 10^-8 to 9.01 × 10^-6. There is not a carcinogenic risk value greater than 10^-4 in the entire region, but potential carcinogenic risks persisted in some areas. We conclude that PAHs pollution of soil in the area is an issue that deserves urgent attention for the relevant departments.

Detection, provenance and associated environmental risks of water quality pollutants during anomaly events in River Atoyac, Central Mexico: A real-time monitoring approach

River Atoyac is considered to be one of the most polluted rivers in Mexico due to the discharges of untreated or partially treated wastewater from industrial and municipal activities. In order to improve the river water quality, it is obligatory to identify the possible contaminant sources for upholding a well-balanced ecosystem. Henceforth, the present study incorporates the application of a continuous real-time monitoring system to identify the provenance of pollutants of the river mainly from anomaly events. Four monitoring stations were installed all along the River Atoyac in the State of Puebla, Central Mexico. The real-time monitoring systems have an ability to measure various water quality parameters for every 15 minutes such as Temperature (T), pH, Conductivity (EC), turbidity (TURB), Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP) and Spectral Absorption Coefficient (SAC). In total, eight water samples of anomaly events (i.e.) 2 per monitoring station during rainy (August-September) and winter seasons (November-December), that were detected using the parameters previously mentioned were procured and also analyzed in the laboratory for evaluating almost 54 physicochemical, inorganic and organic characteristics. Statistical results of factorial analysis explained that 30% of the total variance corresponded to textile effluents, 23% related to discharges produced by automobile and petrochemical industries, and 18% of the total variance defined the agricultural activities. Additionally, indices like Overall Index Pollution, Heavy Metal Evaluation Index, Screening Quick Reference Table and Molecular ratios of hydrocarbons for PAH sources was also calculated to estimate the grade of pollution and associated ecotoxicological risks. The present study also enlightens the fact that the assessed results will definitely provide valuable information for the management of river water quality by developing stringent public policies by governmental agencies for the sustainable conservation of Atoyac River.

Halogenated and parent polycyclic aromatic hydrocarbons in vegetables: Levels, dietary intakes, and health risk assessments

Halogenated polycyclic aromatic hydrocarbons (HPAHs) are attracting increasing concern because of their greater toxicity than their corresponding parent PAHs. However, human exposure to HPAHs via food consumption is not fully understood. In this study, daily intake via vegetable ingestion of 11 HPAHs and 16 PAHs and subsequent cancer risk were assessed for population in Beijing. A total of 80 vegetable samples were purchased from markets, including five leafy vegetables and three root vegetables. The concentrations of total HPAHs (∑HPAHs) were 0.357-0.874ng/g in all vegetables, lower than that of total PAHs (∑PAHs, 10.6-47.4ng/g). ∑HPAHs and ∑PAHs concentrations in leafy vegetables were higher than those in root vegetables, suggesting that the atmospheric deposition might be the dominant source of PAHs and HPAHs in leafy vegetables. Among the HPAH congeners, 2-BrFle and 9-ClFle were the predominant compounds and frequently detected in the vegetable samples. HPAHs and PAHs were also found in certificated vegetables at the concentrations of 0.466-0.751ng/g and 10.6-38.9ng/g, respectively, which were lower than those in non-certificated vegetables except for spinach. For leafy vegetables from local farms, the ∑PAHs and ∑HPAHs levels in the rape and Chinese cabbage samples significantly decreased with increasing the distance away from the incineration plant. The incremental lifetime cancer risks of HPAHs were below the acceptable risk level (10^-6), suggesting that there might be little or no risk to consumers from these compounds in vegetables. For all population groups, children were the most sensitive population to PAHs and HPAHs, and their health issues should be paid more attention.