The main strategies for soil pollution apportionment: A review of the numerical methods

Nowadays, a large number of compounds with different physical and chemical properties have been determined in soil. Environmental behaviors and source identification of pollutants in soil are the foundation of soil pollution control. Identification and quantitative analysis of potential pollution sources are the prerequisites for its prevention and control. Many efforts have made to develop methods for identifying the sources of soil pollutants. These efforts have involved the measurement of source and receptor parameters and the analysis of their relationships via numerical statistics methods. We have comprehensively reviewed the progress made in the development of source apportionment methodologies to date and present our synthesis. The numerical methods, such as spatial geostatistics analysis, receptor models, and machine learning methods are addressed in depth. In most cases, however, the effectiveness of any single approach for source apportionment remains limited. Combining multiple methods to address soil quality problems can reduce uncertainty about the sources of soil pollution. This review also constructively highlights the key strategies of combining mathematical models with the assessment of chemical profiles to provide more accurate source attribution. This review intends to provide a comprehensive summary of source apportionment methodologies to help promote further development.

Polycyclic aromatic hydrocarbon (PAH) source identification and a maternal transfer case study in threatened killer whales (Orcinus orca) of British Columbia, Canada

The northeastern Pacific (NEP) Ocean spans the coast of British Columbia (Canada) and is impacted by anthropogenic activities including oil pipeline developments, maritime fossil fuel tanker traffic, industrial chemical effluents, agricultural and urban emissions in tandem with stormwater and wastewater discharges, and forest wildfires. Such events may expose surrounding marine environments to toxic polycyclic aromatic hydrocarbons (PAHs) and impact critical habitats of threatened killer whales (Orcinus orca). We analyzed skeletal muscle and liver samples from stranded Bigg's killer whales and endangered Southern Resident killer whales (SRKWs) for PAH contamination using LRMS. C3-phenanthrenes/anthracenes (mean: 632 ng/g lw), C4-dibenzothiophenes (mean: 334 ng/g lw), and C4-phenanthrenes/anthracenes (mean: 248 ng/g lw) presented the highest concentrations across all tissue samples. Diagnostic ratios indicated petrogenic-sourced contamination for SRKWs and pyrogenic-sourced burdens for Bigg's killer whales; differences between ecotypes may be attributed to habitat range, prey selection, and metabolism. A mother-fetus skeletal muscle pair provided evidence of PAH maternal transfer; low molecular weight compounds C3-fluorenes, dibenzothiophene, and naphthalene showed efficient and preferential exposure to the fetus. This indicates in-utero exposure of PAH-contamination to the fetus. Our results show that hydrocarbon-related anthropogenic activities are negatively impacting these top predators; preliminary data found here can be used to improve oil spill and other PAH pollution management and regulation efforts, and inform policy to conserve killer whale habitats in the NEP.

Fine and ultrafine particle emission factors and new diagnostic ratios of PAHs for peat swamp forest fires

Peatland fires are one of the major global sources of atmospheric particles. Emission factors for fine (PM1 and PM2.5) and ultrafine (PM0.1) particles and particle-bound polycyclic aromatic hydrocarbons (PAHs) from plants in the peat swamp forest (PSF), including Melaleuca cajuputi leaves, M. cajuputi branches, M. cajuputi bark, Lepironia articulata (Retz.) Domin, forest leaf litter and peat were measured in a laboratory combustion chamber. From these measurements, new PAH diagnostic ratios for fine and ultrafine particles were proposed for identifying the forest burning source. The new emission factors for PM were PM0.1: 0.03-0.33, PM1: 0.69-2.11 and PM2.5: 1.12-4.18 g/kg; for PM-bound PAHs, the factors were PM0.1: 5.7-166.0, PM1: 31.5-1338.9 and PM2.5: 36.3-3641.1 μg/kg. The predominant PAHs for PSF burning were Pyr, BbF, DBA (in PM0.1), Flu, DBA, BghiPe (in PM1), and BbF, DBA and BghiPe (in PM2.5). We also presented new diagnostic ratios for PSF burning, including BaP/(BaP + Chr): 0.39-0.75, BaP/(BaP + BbF): 0.21-0.47 and BaA/(BaA + Chr): 0.36-0.53. Moreover, the physical and chemical characteristics of ambient fine and ultrafine particles in the Kuan Kreng forest during the 2019 forest fire (FF) and 2021 non-forest fire (NFF) periods were investigated. The mean PM0.1, PM1 and PM2.5 concentrations during the FF period were approximately 3.5-4.4 times as high as those during the 2021 NFF period. New PAH diagnostic ratios of BaP/(BaP + BbF) versus BaP/(BaP + Chr) were able to identify PAH burning sources in PM1 and PM2.5 but were less clear for PM0.1, which was dominated by a single source - M. cajuputi. Chemical mass balance studies identified peat forest burning emissions as the main source of fine and ultrafine particles during the FF period. This study suggests that the new PAH diagnostic ratios can be used to identify the burning source for more precise source apportionment.

Abundance and composition of polycyclic aromatic hydrocarbons in the surface sediments of twelve alpine lakes in the Central Taurus Mountains

The regions of Bolkar Mountains and Aladağlar accommodate a unique ecosystem in Turkey, due to being in a transitional climate between the continental and the Mediterranean and hosting alpine lakes which are considered as good indicators of regional and atmospheric pollution due to being far from direct human impact. On the other hand, these regions are surrounded by various power plants, and also subject to occasional human activities, where anthropogenic effects are expected to be. Sediment samples were collected from 12 lakes in Central Taurus Mountains, 6 lakes in Bolkar Mountains, and 6 lakes in Aladağlar. Fifteen PAHs, identified as priority pollutants by the US Environmental Protection Agency (EPA), as well as lake water chemical characteristics were determined. The distribution of analyzed PAHs was investigated, and PAH diagnostic ratios were calculated to identify their potential sources. It was a remarkable observation that only low-molecular-weight PAHs exist in the lakes of Aladağlar, whereas high-molecular-weight PAHs are also found in the lakes of Bolkar Mountains, likely reflecting more isolated characteristics of the Aladağlar region. As compatible with this observation, total PAHs (T-PAHs) were found lower in Aladağlar (0.00-105.78 ng/g w.w.) than in Bolkar Mountains (9.08-380.16 ng/g w.w.). Overall, T-PAHs of sampled lakes were found in a similar range when they are compared to the other high-altitude alpine lakes around the world, indicating no significant difference in terms of atmospheric pollution of the global average.

Characterization, sources, and risk assessment of PAHs in borehole water from the vicinity of an unlined dumpsite in Awka, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are contaminants of interest in the ecosystem due to associated health risks. Therefore, their detection in the environment is important. In this regard, the risk assessment of PAHs in borehole water near the unlined dumpsite in Anambra State was investigated. Samples of borehole water (16 each) were collected from the study and control areas during both seasons. The PAH concentrations in the borehole water samples were analyzed using gas chromatography. The mean PAH concentration in the study and control samples for the wet season varied from BL-7.65 µg/L to BL-2.98 µg/L, respectively. The study samples' dry season values ranged from BL to 3.33 µg/L, while control samples ranged from BL to 1.87 µg/L. [Formula: see text]PAHs for the wet and dry seasons varied from 5.8 to 13.94 µg/L and 4.25 to 10.09 µg/L for study and control samples, respectively. The four and five rings PAH were the most dominant group in the [Formula: see text] PAHs for the study and control samples, respectively. Diagnostic ratios suggested pyrolytic and petrogenic sources for both locations. The cluster analysis showed different sources of the congeners in the samples. The non-carcinogenic risk showed no possibility of risks via dermal and ingestion routes. In addition, the possibility of cancer risks via ingestion routes was doubtful. The carcinogenic risk index through dermal contact exceeded the acceptable limit for adults and is at a tolerable limit for children, indicating potential threats to humans, with adults more susceptible to cancer risks. Therefore, this study recommends that sanitary dumpsites be constructed for waste disposal and implementation of environmental laws to prevent underground water pollution and the environment.

Potential sources and health risk assessment of polycyclic aromatic hydrocarbons in street dusts of Karaj urban area, northern Iran

In the present study chemical fingerprinting approach (isomeric ratios), a receptor-oriented model (principal component analysis with multiple linear regression, PCA/MLR) and a probabilistic health risk framework were employed to characterization, source appointment and carcinogenic risk assessment of polycyclic aromatic hydrocarbons (PAHs) in street dusts of Karaj urban area (northern Iran). Thirty street dusts samples were collected from the different functional areas in the city of Karaj and analyzed for PAHs by gas chromatography/mass spectrometry (GS/MS). The results obtained showed that ∑16PAHs concentrations varied widely from 16.2 to 1236.2 with a mean of 624 μg/kg and decreased in the following order of functional areas; traffic> residential > green/park areas. PAHs profile in the majority of dust samples were dominated by 5-6 rings PAHs, accounting for 25%-95% of the total PAHs. Qualitative source apportionment using the molecular isomeric ratios indicated mixed sources of PAHs in street dusts while PCA/MLR receptor model quantitatively identified three major sources with following relative contributions to the total dust PAH burden; 51% for pyrogenic-traffic sources, 32% for traffic-stationary sources and, 16% for petrogenic sources. The results of health risk assessment based on probabilistic model indicated that at the 95% percentiles, total cancer risks for children and adults are 8.43 × 10^-4 and 3.34 × 10^-5, respectively which both are higher than the acceptable baseline (10^-6) indicating potential carcinogenic risk for local residents. It was also revealed that dust ingestion pathway is the most important contributor to the total carcinogenic risks of PAHs for both children and adults although the cancer risk level for adults through dermal and inhalation was 10 times greater than that for children. Based on the sensitivity analysis using the Monte Carlo simulation, benzo[a]pyrene equivalent concentration, exposure duration, dermal exposure area and ingestion rate were found to be the most sensitive exposure parameters which could introduce uncertainties into the cancer risk estimated.

Distribution pattern and health risk assessment of polycyclic aromatic hydrocarbons in the water and sediment of Algoa Bay, South Africa

Polycyclic aromatic hydrocarbons are amongst the pollutants of major concern in the terrestrial and aquatic habitats. They are mostly characterised by carcinogenic and non-carcinogenic effects. Distribution and potential health risks of sixteen priority PAHs in the water and sediment samples collected between December 2015 and June 2016 from Algoa Bay, South Africa, were evaluated. Water and sediment samples collected were extracted with liquid-liquid and soxhlet extraction methods, respectively, and then cleaned up using glass column loaded with silica gel. Final concentrations of the target PAHs were determined by gas chromatography interfaced with flame ionization detector. Results indicated that individual PAH concentrations in surface water, bottom water and sediment samples ranged from not detected (ND) to 24.66 µg/L, ND to 22.81 µg/L and ND to 5.23 mg/kg correspondingly. Total PAHs concentrations varied as 12.78-78.94 µg/L, 1.20-90.51 µg/L and 1.17-10.47 mg/kg in the three environmental matrices in that order. The non-carcinogenic risk was generally below 1, whereas risk indices (dermal contact) were above the acceptable limit of 1 × 10^-4 in the water column, suggesting possible carcinogenic effects to humans, with adults being the most vulnerable. Similarly, highest contributions to TEQs and MEQs in the sediments were made by benzo(a)pyrene and dibenzo(a,h)anthracene, the two most toxic congeners, signifying the possibility of carcinogenicity and mutagenicity in humans. Diagnostic ratios of PAHs reflect a prevailing pyrogenic input all through. The pollution was albeit moderate, yet regular check is recommended to ensure safe and healthy environment for human and aquatic lives.

Levels of Polycyclic Aromatic Hydrocarbons in the Water and Sediment of Buffalo River Estuary, South Africa and Their Health Risk Assessment

The incidence and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in the Buffalo River Estuary in the Eastern Cape Province of South Africa were assessed in this study. A total of 60 surface water and 19 sediment samples were collected from 5 sites of the estuary over a period of 6 months (December 2015 to May 2016). Extraction of PAHs from the water and sediment samples was achieved by using liquid-liquid and soxhlet extraction methods respectively, followed by column clean up with silica gel and quantification by gas chromatography-flame ionization detection. Individual PAH levels in the water and sediment samples ranged from not detected (ND) to 24.91 μg/L and ND to 7792 μg/kg, respectively. Total concentrations of the PAHs in the water and sediment samples varied as 14.91-206 μg/L and 1107-22,310 μg/kg in that order. Total levels of the contaminants were above the target values in the two matrices and were higher in summer than autumn. Although the noncarcinogenic risk of PAHs estimated in the water column through dermal absorption was very low compared with the target value, the carcinogenic risk determined was high for both adults and children. Similarly, benzo(a)pyrene and dibenzo(a,h)anthracene were found to be of higher carcinogenic and mutagenic risks in the sediments collected from the study area. Diagnostic ratios suggest that the target hydrocarbons are predominantly from pyrolytic sources. It therefore could be inferred that the water body is conspicuously polluted; hence, efforts should be made to control all the activities contributing to such magnitude of pollution at the sites.

Characterization and risk assessment of PAH-contaminated river sediment by using advanced multivariate methods

This study applied advanced multivariate methods and risk assessment to evaluate the characteristics of polycyclic aromatic hydrocarbons (PAHs) in the sediment of the severely polluted Erjen River in Taiwan. High-molecular-weight PAHs (HPAHs) dominated in the rainy season. The ecological risk of PAHs in the sediment was low, whereas the total health risk through ingestion and dermal contact was considerably high. The SOM (self-organizing map) analysis clustered the datasets of PAH-contaminated sediment into five groups with similar concentration levels. Factor analysis identified major factors, namely coal combustion, traffic, petrogenic, and petrochemical industry factors, accounting for 88.67% of the variance in the original datasets. The major tributary and the downstream of the river were identified as PAH-contamination hotspots. The PMF (positive matrix factorization) was combined with toxicity assessment to estimate the possible apportionment of sources and the associated toxicity. Spills of petroleum-related products, vehicle exhaust, coal combustion, and exhaust from a petrochemical industry complex constituted respectively 12%, 6%, 74%, and 86% of PAHs in the sediment, but contributed respectively 7%, 15%, 22%, and 56% of toxicity posed by PAHs in the sediment. To improve the sediment quality, best management practices should be adopted to eliminate nonpoint sources of PAHs flushed by storm water into the major tributary and the downstream of the Erjen River. The proposed methodologies and results provide useful information on remediating river PAH-contaminated sediment and may be applicable to other basins with similar properties that are experiencing resembled river environmental issues.

Health and carcinogenic risk evaluation for cohorts exposed to PAHs in petrochemical workplaces in Rawalpindi city (Pakistan)

This study presents the analyses of urinary biomarkers (1-OHPyr, α- and β-naphthols) of polycyclic aromatic hydrocarbons (PAHs) exposure and biomarkers of effect (i.e. blood parameters) in petroleum-refinery workers (RFs) and auto-repair workers (MCs). Exposed subjects had higher concentrations of white blood cell (WBC) count than control subjects (CN) subjects (5.31 × 10(3) μL(-1) in exposed vs. 5.15 × 10(3) μL(-1) in CN subjects), while the biomarker of oxidative DNA damage (8-OHdG) was significantly higher in MCs. The exposure among these two cohorts could be influenced by the ambience of the workplaces; in fact, MCs' shops are relatively damp and enclosed workplaces in comparison with the indoor environment of refineries. PAHs in the dust samples from mechanical workshops probably originated from mixed sources (traffic exhaust and petroleum spills), while the incremental lifetime cancer risk (ILCR) for MCs showed moderate-to-low cancer risk from exposure to dust-bound PAHs. The study shows that increasing PAH exposure can be traced in MC workstations and needs to be investigated for the safety of public health.