Source identification and ecological risks of parent and substituted polycyclic aromatic hydrocarbons in river surface sediment-pore water systems: Effects of multiple factors

Unconventional polycyclic aromatic compounds distribution profiles in sediment cores collected from Todos os Santos Bay, Northeastern Brazil

Polycyclic aromatic compounds (PACs) include conventional polycyclic aromatic hydrocarbons (PAHs) and nitrated (NHPAs), oxygenated (OHPAs), heterocyclic polycyclic aromatic sulfur (PASHs) derivatives, considered unconventional. Sediment cores were collected at four Todos os Santos Bay sites (BTS, Northeastern Brazil). Eighteen NPAHs, six OPAHs, seven PASHs, and nineteen PAHs were determined. The total concentrations of NPAHs, PASHs, and PAHs increased from the bottom towards the top of the cores, ranging from Collapse

Key Words

• Ecological risk assessment
• Heterocyclic aromatic polycyclic aromatics
• Nitrated-PAHs
• Oxygenated-PAHs
• Sediment cores
• Todos os Santos Bay

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Affiliation(s)

Eileen Rocio Niño-Zambrano Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil
Pedro V B Bahia Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil
Madson M Nascimento Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil; Centro Universitário SENAI-CIMATEC, Salvador, Bahia 41650-010, Brazil
Fábio X A Sampaio Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil
Ricardo da S Duarte Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil
Vanessa Hatje Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil
Maria Elisabete Machado Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil; INCT em Energia e Ambiente, Universidade Federal da Bahia, Salvador, Bahia 40170-11, Brazil
Jailson B de Andrade Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil; Centro Universitário SENAI-CIMATEC, Salvador, Bahia 41650-010, Brazil; INCT em Energia e Ambiente, Universidade Federal da Bahia, Salvador, Bahia 40170-11, Brazil
Gisele O da Rocha Instituto de Química da Universidade Federal da Bahia, Salvador, Bahia 40170-110, Brazil; Centro Interdisciplinar de Energia e Ambiente-CIEnAm, Universidade Federal da Bahia, Salvador, Bahia 40170-115, Brazil; INCT em Energia e Ambiente, Universidade Federal da Bahia, Salvador, Bahia 40170-11, Brazil.

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Polycyclic aromatic hydrocarbons (PAHs) occurrences in water bodies, extraction techniques, detection methods, and standardized guidelines for PAHs in aqueous solutions

Polycyclic aromatic hydrocarbons (PAHs) are a carcinogenic compound comprised of benzene ring(s). They occur naturally. However, the occurrence of anthropogenic PAHs (originates from human activities and man-made structures) may contribute to water pollution, risking the public health and aquatic life. This review describes occurrences of PAHs in water bodies, extraction techniques, detection methods, and standardized guidelines for PAHs in aqueous solutions. Previous research identifies PAH contamination across freshwater bodies due to proximity to pollution sources and hydrological factors. Despite analytical advancements, accurately quantifying and characterizing PAHs in complex environmental matrices remains challenging. Overall, this review supports the Sustainable Development Goals (SDGs) no. 6 (clean water and sanitation public) and no. 14 life below water.

Unraveling the spatiotemporal trends and source attribution of polycyclic aromatic hydrocarbons and oxygenated derivatives in Guangzhou agricultural ditch sediment

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) have garnered significant scientific attention due to their heightened toxicity and mobility compared to their parent PAHs. This study investigated the occurrence of 11 OPAHs and 16 PAHs within agricultural ditch sediment of Guangzhou City, China. The ΣPAH and ΣOPAH concentrations ranged from 63.8-3955 ng/g and 16.5-522 ng/g, respectively. Notably, concentrations were elevated during the rainy season, attributed to intensified atmospheric deposition and surface runoff during the rainy season. Spatially, Pearson correlation and path analysis disclosed a linkage between OPAHs and high-molecular-weight PAHs and adjacent agricultural practices, whereas low-molecular-weight PAHs were associated with human and industrial operations. This disparity was linked to the restricted mobility of high-molecular-weight PAHs, rendering them particularly susceptible to proximal sources. Diagnostic ratios and principal component analysis-multiple linear regression (PCA-MLR) implicated fossil fuel combustion and vehicle emissions as major contributor to the sedimentary OPAHs and PAHs. Further correlations between estimated source contributions and water quality, strengthened by spatial interpolation, clearly identified agricultural activities, and atmospheric deposition associated with traffic emissions and fossil fuel combustion as primary contributor to sedimentary OPAHs and PAHs. Secondary sources encompassed coal combustion, road runoff, and wastewater from both industrial and shipping activities. The risk quotients (RQs) for PAH and OPAH mixtures indicated moderate to high ecological hazards. This study demonstrated the importance of employing the integrated approach, combining PCA-MLR, diagnostic ratios, and correlation of source contributions with water quality in precisely delineating the origins of OPAHs and PAHs in agricultural ditch sediment.

Distribution of carcinogenic polycyclic aromatic hydrocarbons in urban soil across major cities of Bihar, India: seasonal variation, source apportionment, and health risk assessment

This study investigates the distribution of sixteen priority polycyclic aromatic hydrocarbons (PAHs), various sources of PAHs, and their probable cancer-causing risks in the soil samples collected from urban cities in Bihar, India. During the winter season, the ∑16 PAH concentration was dominant and ranged from 979.36 to 5149.37 ngg-1 with a mean value of 2684.79 ngg-1, while for the summer season, it ranged from 690.06 to 4539.55 ngg-1 with a mean value of 2194.31 ngg-1. The (4-ring) PAH compounds were the major contributors, accounting for 40% and 37% in the winter and summer seasons, respectively followed by (5- and 6-ring) PAHs at 30% and 32%, and (2- and 3-ring) PAHs at 29% and 30% in the respective seasons. Carcinogenic PAHs constituted ~ 50% of the ∑16 PAHs, with mean values of 1353.97 ngg-1 and 1098.09 ngg-1 for the winter and summer seasons, respectively. Positive matrix factorization (PMF) confirmed the dominance of fossil fuel burning and biomass burning as a primary source in the urban soil of Bihar. Total mean benzo(a)pyrene equivalent (BaPeq) values for the ∑16 PAHs were 312.04 ngg-1 for the winter season and 262.83 ngg-1 for the summer season. These values were higher in current study sites as compared with other studies. However, the concentration range fell within the limit set by the Canadian soil quality standard (700.00 ngg-1) and exceeded the limit of the Dutch target value (32.96 ngg-1). The Incremental Lifetime Cancer Risk (ILCRs) from dermal and ingestion pathways were approximately 104 to 105 times lower than the inhalation pathway, suggesting greater risk. The study revealed higher mean cancer risk values for children (1.16 × 10-5) and adults (1.03 × 10-5) in the winter season, falling within the unacceptable range (10-6 and 10-4) of carcinogenic risk that might lead to human health risk in the study sites.

Presence of polycyclic aromatic compounds in river sediment and surrounding soil: Possible impact from shale gas wastewater

Shale gas has been extensively extracted in the Sichuan Basin in China in recent years. To gain insight into the potential impact of shale gas wastewater (SGW) discharge, sediment in a small river receiving treated SGW, as well as cultivated soil and paddy soil irrigated by the river water were collected. The occurrence and distribution of polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and their alkylated/oxygenated derivatives (APAHs/OPAHs), and thiophenes were investigated, the resultant potential ecological risks were assessed subsequently. The total concentration of PACs varied in the range of 1299.9-9286.4, 2069.4-11,512.3, and 475.7-2927.9 ng/g in sediment, cultivated soil and paddy soil, respectively, with thiophenes followed by APAHs being the abundant components in all the studied samples, demonstrating the potential impact of SGW discharge on sediment and surrounding soil environment. Based on the measured concentrations, potential ecological risks posed by PAHs and APAHs were calculated, and moderate to high ecological risks were observed in partial sampling sites, which mainly caused by 3-4 rings PAHs and APAHs.

Dual biomarker traceability and ecological risk assessment of centennial organic contamination in South Dongting Lake

Enhanced anthropogenic activity strength has altered the watershed particulate transport and material cycle resulting in organic pollutant deposition changes in Dongting Lake associated with unclear ecological risk. In the present study, dual biomarkers i.e. n-alkanes and polycyclic aromatic hydrocarbon (PAHs) were applied in the 210Pb-dated sediment cores for traceability of centennial organic pollutants in the lake mouth area. The partial least squares path model and risk quotients method were used to explore the controlling pathways and ecological risk. The results show a range of sedimentary organic carbon (C), nitrogen (N), and phosphorus (P) was at 1.76-185.66, 0.97-89.80, and 0.01-0.97 g m-2 yr-1 with total reserves of 51.68, 18.44, and 0.27 t ha-1, respectively, over the past 179 years. The presence of PAHs rapidly increased by 2.47 fold from 535.60 ng g-1, while PAHs and carcinogenic PAHs (ΣCPAHs) burial fluxes increased by about 6 and 5 folds, respectively. Accompanied by anthropogenic activities and climate change, the exotic sources gradually becoming predominant. The n-alkane diagnostic ratios indicated a shift of organic matter (OM) from autotrophic bacteria, algae, and phytoplankton-derived sources to macrophyte and terrestrial plants. The exotic origins rose to approximately 73.61 %, while endogenous sources decreased to 26.39 %. The direct effects of anthropogenic activities and their indirect negative impacts on climate and sedimentary structure are the key ways for sediment material loading. The nutrient accumulation in sediments coincides with the lake's eutrophication history over the past decades. The ΣCPAHs accounted for about 89.37 ± 17.14 % of the total TEQ, reflecting a strong ecological risk. The contribution of anthropogenic activities such as fuel usage, fertilizer application, hard pavement coverage, and OM loss from the ecosystem to the sources of organic pollutants and their component types may be a focus of attention in the middle reaches of the Yangtze River plain lake.

Distribution and sources of polycyclic aromatic hydrocarbons in cascade reservoir sediments: influence of anthropogenic activities and reservoir hydrology

The construction of dams has caused disruptions to river connectivity, leading to alterations in the deposition of hydrophobic organic contaminants in reservoir sediments. Further investigation is warranted to explore the impact of cascade reservoirs with differing hydrological characteristics on polycyclic aromatic hydrocarbons (PAHs) distribution in sediment. This study examines the presence of 30 PAHs in the sediments collected from six cascade reservoirs situated in the Wujiang River basin during January and July 2017. The results showed that Σ30 PAHs ranged from 455-3000 ng/g dw (mean 1030 ng/g dw). Anthropogenic activities and reservoir hydrology determined the distribution trend of PAHs in sediments, with an overall increase from upstream to midstream and then a decrease downstream. The PAH levels were highly linked to the secondary industry (P < 0.05). This was further supported by the relationship between the PAH emissions from coal combustion and traffic sources analyzed by the positive matrix factorization model and economic parameters in the wet season (P < 0.01). At the same time, reservoir age (RA) showed a positive correlation with PAH concentrations (P < 0.05), while hydraulic retention time (HRT) exhibited a negative correlation with PAH levels (P = 0.03). The relationship between total organic carbon (TOC) and PAHs in stream sediments worldwide was nonlinear (P < 0.01), with PAH concentrations initially rising and then falling as TOC levels increased. Concerns regarding carcinogenic risk were raised due to contributions from coal and vehicular sources, with the risk increasing with RA.

Quantifying the impact of anthropogenic emissions and aquatic environmental impacts on sedimentary mercury variations in a typical urban river

In urban and industrial regions, sedimentary mercury (Hg) serves as the crucial indicator for Hg pollution, posing potential risks to ecology and human health. The physicochemical processes of Hg in aquatic environments are influenced by various factors such as anthropogenic emissions and aquatic environmental impacts, making it challenging to quantify the drivers of total mercury (THg) variations. Here, we analyzed the spatiotemporal variations, quantified driving factors, and assessed accumulation risks of sedimentary THg from the mainstream of a typical urban river (Haihe River). THg in the urban region (37-3237 ng g-1) was significantly higher (t-test, p < 0.01) than in suburban (71-2317 ng g-1) and developing regions (156-916 ng g-1). The sedimentary THg in suburban and developing regions increased from 2003 to 2018, indicating the elevated atmospheric deposition of Hg. Together with the temperature, grain size of sediments, total organic carbon (TOC), the pH and salinity of water, 40 components of parent and substituted polycyclic aromatic hydrocarbons (PAHs) were first introduced to quantify the driver of sedimentary THg based on generalized additive model. Results showed that anthropogenic emissions, including three PAHs components (31%) and TOC (63%), accounted for 94% of sedimentary THg variations. The aquatic environmental impacts accounted for 5% of sedimentary THg variations. The geo-accumulation index of THg indicated moderate to heavy accumulation in the urban region. This study demonstrates that homologous pollutants such as PAHs can be used to trace sources and variations of Hg pollution, supporting their co-regulation as international conventions regulate pollutants.

Distribution, levels, sources and risk assessment of polycyclic aromatic hydrocarbons in the bottom sediments of a Mediterranean river under multiple anthropopressures (Soummam River), Algeria

The Soummam River, a vital watercourse in Algeria is threatened by anthropogenic activities despite its protected wetland status. This study is the first to assess sediment pollution in the Soummam River, examining levels, compositions, sources of 16 PAHs and their effects on the environment and human health. Analysis employing Principal Component Analysis (PCA) and molecular diagnostic ratios pointed to petrogenic sources, likely stemming from petroleum leaks originating from aging pipeline and vehicles, as well as pyrogenic sources arising from vehicle exhaust and biomass combustion. Environmental and health risks were assessed through risk quotients (RQ), Sediments Quality Guidelines (SQG) and Total Lifetime Cancer Risk (TLCR). Ecological risk was found to range from moderate to high, with anticipated biological impacts, while cancer risk was deemed low. Toxicity assessment, measured by TEQ, revealed that the majority of monitoring stations exceeded safe levels. Consequently, urgent action by local authorities is warranted to implement ecosystem rehabilitation measures.

Human health risk assessment associated with the reuse of treated wastewater in arid areas

Qatar produces more than 850,000 m3/day of highly treated wastewater. The present study aims at characterizing the effluents coming out of three central wastewater treatment plants (WWTPs) of chemical pollutants including metals, metalloids and antibiotics commonly used in the country. Additionally, the study is assessing human health risks associated with the exposure to the treated wastewater (TWW) via dermal and ingestion routes. Although the origin of domestic wastewater is desalinated water (the only source of fresh water), the results show that the targeted parameters in TWW were within the international standards. Concentrations of Cl, F, Br, NO3, NO2, SO4 and PO4, were 389, <0.1, 1.2, 25, <0.1, 346, and 2.8 mg/L, respectively. On the other hand, among all cations, metals and metalloids, only boron (B) was 2.1 mg/L which is higher than the Qatari guidelines for TWW reuse in irrigation of 1.5 mg/L. Additionally, strontium (Sr) and thallium (Tl) were detected with relatively high concentrations of 30 mg/L and 12.5 μg/L, respectively, due to their natural and anthropogenic sources. The study found that the low concentrations of all tested metals and metalloids do not pose any risk to human health. However, Tl presents exposure levels above the 10 % of oral reference dose (HQ = 0.4) for accidental oral ingestion of TWW. The results for antibiotics show that exposure for adults and children to TWW are far below the admissible daily intakes set using minimum therapeutic dose and considering uncertainty factors. Treated wastewater of Qatar can be used safely for irrigation. However, further investigations are still needed to assess microbiological quality.

Remediation of heavily PAHs-contaminated soil with high mineral content from a coking plant using surfactant-enhanced soil washing

This study investigated the effectiveness of various surfactants at different concentrations in removing high concentrations of polycyclic aromatic hydrocarbons (PAHs) from soil with high mineral content, focusing on the impact of surfactant treatment on the mobility of the residual PAHs in soil. The results revealed that the cationic surfactant (CTMAB) inhibited removal of PAHs in the whole tested concentration range of 0.1-8 g/L. In contrast, the non-ionic and anionic surfactants (Triton X-100 and SDBS) significantly enhanced removal of PAHs as their amendment concentrations reached 2 g/L and above. Triton X-100 exhibited steadily increased efficacy with increasing amendment concentrations and maintained favorable solubilization capability when continuously amended, making it the preferable choice for remediating PAHs-contaminated soil. Surfactant and water washing processes altered soil physicochemical properties by removing some clay minerals (e.g., faujasite) and organic matter that can bind or sequester PAHs, potentially increasing their extractability and bioavailability in the washed soil, thereby posing higher ecological risks compared to the original one. Although soil washing decreased retention of the remaining PAHs in soil, it did not significantly impact PAHs release from soil by flowing water. These findings provide insights into the long-term effectiveness and ecological impacts of surfactant-enhanced washing as a potential remediation technique for PAHs-contaminated soil.

A Systematic Review of Polycyclic Aromatic Hydrocarbon Derivatives: Occurrences, Levels, Biotransformation, Exposure Biomarkers, and Toxicity

Polycyclic aromatic hydrocarbon (PAH) derivatives constitute a significant class of emerging contaminants that have been ubiquitously detected in diverse environmental matrixes, with some even exhibiting higher toxicities than their corresponding parent PAHs. To date, compared with parent PAHs, fewer systematic summaries and reanalyses are available for PAH derivatives with great environmental concerns. This review summarizes the current knowledge on the chemical species, levels, biotransformation patterns, chemical analytical methods, internal exposure routes with representative biomarkers, and toxicity of PAH derivatives, primarily focusing on nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs), halogenated PAHs (XPAHs), and alkylated PAHs (APAHs). A collection of 188 compounds from four categories, 44 NPAHs, 36 OPAHs, 56 APAHs, and 52 XPAHs, has been compiled from 114 studies that documented the environmental presence of PAH derivatives. These compounds exhibited weighted average air concentrations that varied from a lower limit of 0.019 pg/m3 to a higher threshold of 4060 pg/m3. Different analytical methods utilizing comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC × GC-TOF-MS), gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS), comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry (GC × GC-QQQ-MS), and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), that adopted untargeted strategies for the identification of PAH derivatives are also reviewed here. Additionally, an in-depth analysis of biotransformation patterns for each category is provided, including the likelihood of specific biotransformation reaction types. For the toxicity, we primarily summarized key metabolic activation pathways, which could result in the formation of reactive metabolites capable of covalently bonding with DNA and tissue proteins, and potential health outcomes such as carcinogenicity and genotoxicity, oxidative stress, inflammation and immunotoxicity, and developmental toxicity that might be mediated by the aryl hydrocarbon receptor (AhR). Finally, we pinpoint research challenges and emphasize the need for further studies on identifying PAH derivatives, tracking external exposure levels, evaluating internal exposure levels and associated toxicity, clarifying exposure routes, and considering mixture exposure effects. This review aims to provide a broad understanding of PAH derivatives' identification, environmental occurrence, human exposure, biotransformation, and toxicity, offering a valuable reference for guiding future research in this underexplored area.

Spatiotemporal variability of PAHs and their derivatives in sediments of the Laizhou Bay in the eastern China: Occurrence, source, and ecological risk assessment

To understand the pollution status and risk levels in the Laizhou Bay, the spatiotemporal distribution, source, and ecological risk of 16 polycyclic aromatic hydrocarbons (PAHs) and 20 substituted PAHs (SPAHs) were studied in surface sediments in 2022. The findings indicated significant seasonal differences in the concentrations of PAHs and SPAHs under the influences of precipitation, temperature, light, and human activities, with higher storage levels in summer than in spring, and there was also a spatial distribution trend of estuary > coast > offshore. 2-Nitrofluorene (2-NF) and 2-methylnaphthalene (2-MN) were the most abundant components of SPAHs in both spring and summer, with levels of 21.44 ng/g and 17.89 ng/g in spring, 43.22 ng/g and 25.51 ng/g in summer, respectively. The results of the diagnostic ratio and principal component analysis - multiple linear regression identified sources of PAHs and SPAHs as combustion sources, including petroleum, coal, and biomass. The risk level of PAHs was low-to-moderate according to the toxicity equivalent quotient (TEQ) and risk quotient. A novel calculation method based on TEQ was proposed to assess the ecological risk of SPAHs, and the results indicated that the risk level of SPAHs was moderate-to-high.