Characteristics, distribution, source and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in sediments along the Yangtze River Estuary Deepwater Channel

A review of the pollution signatures of polycyclic aromatic hydrocarbons in the sediments of the East China Sea

Marine sediments serve as crucial reservoirs for polycyclic aromatic hydrocarbons (PAHs), and their PAH signatures offer valuable historical pollution records. This article provides a comprehensive review of the pollution status of 16 priority PAHs in more than 1000 sediments from the East China Sea (ECS). It focuses on the PAH sources, spatiotemporal distributions, driving factors, and ecological risks, with information derived from peer-reviewed papers published between 2003 and 2023. The results revealed that vehicular emissions, mixed combustion sources of coal, biomass, and coke, as well as petrogenic sources, were the primary contributors to PAH pollution in the ECS sediments, accounting for 50%, 34%, and 16%, respectively. Human activities, hydrodynamic mechanisms, and environmental variables such as particle size and organic matter, collectively influenced the distribution of PAHs. Additionally, the population size and economic development played a key role in the temporal distribution of PAHs in the ECS sediments. The ecotoxicity assessment of PAHs in sediments indicated a low risk level. These outcomes are expected to provide environmentalists with detailed and up-to-date insights into sedimentary PAHs in the ECS, helping to develop suitable monitoring plans and strategies for promoting better management of ECS environment.

Pollution characteristics, distribution and risk level of heavy metals in sediments of the Yangtze River estuary

Pollution characteristics, distribution, risk and sources of 7 heavy metals in sediments of Yangtze River Estuary were investigated. Total concentration ranges of As, Cr, Cu, Cd, Pb, Zn and Ni were [0, 16.5], [1.48, 51.3], [2.66, 318], [0, 0.99], [35.6, 992], [8, 91.3] and [1.88, 108] mg/kg, respectively. Based on the potential ecological risk index and Geoaccumulation index, it was determined that Pb is the most polluted heavy metal. According to class I standard of "Marine sediment quality" of China, mean baseline levels multiples were Pb (8.34) > Cu (0.57) > Cr (0.37) > Zn (0.355) > Ni (0.352) > As (0.28) > Cd (0.00). The study also found the heavy metal content of Pb is the most serious, but most of the Pb content comes from the residual state, which has minimal impact on the environment. The East Nanhui Shoal was identified as the most polluted sub-area in terms of Pb pollution, followed by other specific locations. Considering the pollution level and transport costs, the study concluded that dredge soils of the Yangtze River Estuary Deepwater Channel are not suitable for the restoration of East Hengsha Shoal.

Spatial distribution, source, and ecological risk of PAHs in the sediment of the Fenhe River Basin, China

Polycyclic aromatic hydrocarbons (PAHs) are persistent toxic substances that have ubiquitous presence in water, air, soil, and sediment environments. The growth of PAH toxicities and related ecotoxicology risk in sediment has been a serious concern. Present study examined the PAH concentration, sources, and ecological risk from the selected sites in sediment of Fenhe River. The characteristic molecular ratio (CMR) and principal component analysis (PCA) were applied to analyze the sources. The ecological risk assessment was conducted based on the sediment quality guidelines, the mean effects range median quotient, as well as the toxic equivalent quantity values. The results showed that the mean values of total contents of the 16 individual PAHs were 3.66 mg/kg and 3.16 mg/kg in wet and dry seasons, which were relatively high when compared with other rivers worldwide. Their spatial distribution presented the lower contents in the upstream, while higher concentrations in the middle and down streams of the river. The low molecular weight PAHs were major constituents, and 3-ring PAHs have the highest contents. The results of source analysis indicated that PAHs were primarily from the burning of oil, coal, and biomass. The ecological risk evaluations suggested that the possible adverse biological effects, the low to medium comprehensive risks, and the minor carcinogenic risks existed in the study area. This investigation might provide useful baseline data and technical support for policy-makers and researchers.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in sediments from Baiyang Lake, China

The issue of polycyclic aromatic hydrocarbons (PAHs) has been an environmental focus worldwide. In this study, the contents, sources, and ecological risks of sixteen PAHs in the sediment of Baiyang Lake were estimated, and a list of priority pollutants was established. The total PAH contents ranged from 114 to 1010 ng·g-1. The composition of PAHs indicated that 4- to 6-ring PAHs predominated in the sediment samples. The diagnostic ratio analysis showed that combustion sources were predominant for PAHs in Baiyang Lake. Specifically, the positive matrix factorization model indicated that diesel engine emissions, gasoline engine emissions, wood combustion sources, and coal combustion sources contributed 22, 32, 24, and 22% of ∑PAHs, respectively. Based on the sediment quality guidelines, mean effects range median quotient, ecological risk quotient, and toxicity equivalent quotient methods, the comprehensive assessment results of PAHs in Baiyang Lake sediments indicated that the ecological risks were at medium and low levels. The priority pollutant list showed that benzo[b]fluoranthene and benzo[a]pyrene were the highest-priority pollutants and thus should be given more attention.

Polycyclic aromatic hydrocarbons in aquatic media of Turkey: A systematic review of cancer and ecological risk

Polycyclic aromatic hydrocarbons (PAHs) have gathered worldwide attention due to their carcinogenicity and toxicity. This paper aims to review and extend current knowledge on PAHs in aquatic environments in Turkey, where expansion of the marine industry has caused contamination concerns. To assess cancer and ecological risks associated with PAHs, we systematically reviewed 39 research articles. Mean measured concentrations of total PAHs ranged from 61 to 249,900 ng L^-1 in surface waters, 1 to 209,400 ng g^-1 in sediments, and 4 to 55,000 ng g^-1 in organisms. Estimated cancer risks from concentrations in organisms were higher than those from surface waters and sediments. Negative ecosystem impacts of petrogenic PAHs were estimated to be larger than those of pyrogenic origin, despite the predominance of the latter. Overall, the Marmara, Aegean, and Black seas are highly-polluted and need remedial action, while further study is needed to confirm the status of other water bodies.

Characteristics and source analysis of polycyclic aromatic hydrocarbons in organisms and manure near Ardley Island, Antarctica

In order to better understand the migration and accumulation behavior of polycyclic aromatic hydrocarbons (PAHs) in biological chains in the cold environment around the Ardley Island, a variety of biological and penguin manure samples during China's 36th Antarctic Scientific expedition have been collected and studied. A certain difference in PAHs concentration was observed in the environmental samples, and the order of size was as follows: fish > limpets > krill > manure > brown alga > mosses. The percentage of PAHs with different ring numbers in brown alga, moss, and krill was in the following order: three rings > two rings > four rings > five rings > six rings. The proportion of HMW-PAHs in limpets and fish samples was higher than that in brown alga, moss, manure, and krill samples. The main source of PAHs in environmental samples near Ardley Island is oil, which may be due to the development of tourism in Antarctica, the number of ships and human activities around the region. Therefore, it is imperative to strengthen the protection of the ecological environment in the area around Ardley Island.

Historical evolution of polycyclic aromatic hydrocarbon pollution in Chaihe Reservoir from 1863 to 2018

Pollution from polycyclic aromatic hydrocarbons (PAHs) spreads and changes worldwide. The pollution evolution in the regional water environment evolves in response to multiple factors, requiring considerable attention. PAH heterogeneity in the sediment core from Chaihe Reservoir was investigated to indicate dynamic changes in PAH pollution levels and sources and propose recommendations for controlling PAHs. Dynamic PAH patterns showed that the overall decline in PAH pollution was in association with local anthropogenic activities, temperature, and precipitation over the period 1863-2018. Nevertheless, coal, oil, and natural gas consumptions still played significant roles in transferring PAHs to the reservoir. Meanwhile, there were dominant local origins, including grass, wood, and coal combustion. The results highlight that the joint action of natural and anthropogenic interventions mitigated PAH pollution in the reservoir. Promoting improved fuels, new energy vehicles, and cleaner energy may further lower PAH pollution.

Significance of the great protection of the Yangtze River: Riverine input contributes primarily to the presence of PAHs and HMs in its estuary and the adjacent sea

The Yangtze River protection strategies are expected to improve the water quality and ecological function of the Yangtze River Estuary (YRE). The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 heavy metals (HMs) in the YRE were measured and the riverine fluxes were calculated subsequently. In particular, the concentrations of low molecular weight PAHs (LMW-PAHs), arsenic (As) and mercury (Hg) in seawater decreased over time, while those of other studied pollutants did not change a lot. In sediments, the concentration changes for all the pollutants were insignificant. For the present pollutants, the river input is the dominant source, and the flux decreased after the protection. The contribution of the discharge from wastewater treatment plants (WWTPs) was quantified. Its influence cannot be ignored. The seafood quality remained stable and the risk via diet was insignificant. Long-term monitoring is necessary, and the positive impact of the Protection Strategy is gradually emerging.

Accumulation of polycyclic aromatic hydrocarbons (PAHs) in surface sediment residues of Mahanadi River Estuary: Abundance, source, and risk assessment

In this study, we examined the distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from the Mahanadi River Estuary (MRE), identified sources, and evaluated the ecological toxicity. The PAHs distributions in MRE ranged from 13.1 to 685.4 ng g^-1 (dry weight), with a mean value of 192.91 ± 177.56 ng g^-1 (dry weight). Sediments at sites S11, S8, and S13 have the highest 3-rings, 4-rings, and 5-rings PAHs, respectively. In MRE, pyrene has a significantly higher concentration with a mean value of 30.51 ng g^-1, followed by Fluoranthene (86.2 ng g^-1), Chrysene (67.4 ng g^-1), and Benzo(k)fluoranthene (54.2 ng g^-1). Site S8 had a higher total PAH concentration than sites S11, S13, and S1. The diagnostic and principal component analysis suggests that PAHs originated from petroleum, oil, biomass, and coal combustion. Higher toxic and mutagenic equivalent quotients indicate potential aquatic toxicity and a need for continuous monitoring of MRE for PAHs pollution.

Polycyclic Aromatic Hydrocarbons (PAHs) in the Dissolved Phase, Particulate Matter, and Sediment of the Sele River, Southern Italy: A Focus on Distribution, Risk Assessment, and Sources

The Sele River, located in the Campania Region (southern Italy), is one of the most important rivers and the second in the region by average water volume, behind the Volturno River. To understand the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in the Sele River, water sediment samples were collected from areas around the Sele plain at 10 sites in four seasons. In addition, the ecosystem health risk and the seasonal and spatial distribution of PAHs in samples of water and sediment were assessed. Contaminant discharges of PAHs into the sea were calculated at about 1807.9 kg/year. The concentration ranges of 16 PAHs in surface water (DP), suspended particulate matter (SPM), and sediment were 10.1–567.23 ng/L, 121.23–654.36 ng/L, and 331.75–871.96 ng/g, respectively. Isomeric ratio and principal component analyses indicated that the PAH concentrations in the water and sediment near the Sele River were influenced by industrial wastewater and vehicle emissions. The fugacity fraction approach was applied to determine the trends for the water-sediment exchange of 16 priority PAHs; the results indicated that fluxes, for the most part, were from the water into the sediment. The toxic equivalent concentration (TEQ) of carcinogenic PAHs ranged from 137.3 to 292.6 ngTEQ g⁻¹, suggesting that the Sele River basin presents a definite carcinogenic risk.

Monitoring the Chl-a Distribution Details in the Yangtze River Mouth Using Satellite Remote Sensing

The distribution of chlorophyll-a (Chl-a) in the Yangtze River Mouth area was analyzed using a new Chl-a inversion model (PMS-C) based on the relationship between in situ Chl-a and GF-4 PMS band combinations. Combining GF-4 PMS with HY-C CZI, this paper revealed that: (1) Chl-a concentration in Yangtze River Mouth was in the range of 2–6 µg/L, being higher in the west than in the east. The high Chl-a area was mainly distributed near the mouth of the Yangtze River and the Chl-a value was in the range of 3.7 µg/L to 5.9 µg/L. Chl-a concentration is higher in spring and summer than in autumn and winter, with a Chl-a concentration difference of 1–2 µg/L. Chl-a downstream of islands and bridges increased by 0.5–1.7 µg/L compared with upstream. (2) Short-term (within 3 h) changes of Chl-a concentration were effectively detected. In summer and autumn, Chl-a obtained at 13:30 in the noon was generally lower than Chl-a obtained at around 10:30 in the morning and it decreased by nearly 0.1–4 μg/L within three hours on the same day. In winter, the concentration of Chl-a decreased in the range of 0–1.9 μg/L. Generally, within three hours, Chl-a in the downstream of the island decreased significantly from 5 μg/L to about 3.8 μg/L, and Chl-a downstream of piers decreased from 3.7 μg/L to about 3 μg/L. (3) Environmental factors including seawater temperature, illumination, and nutrients, as well as dynamic factors such as wind and tidal current can induce Chl-a change in the Yangtze River Mouth. Short-term change of Chl-a concentration is closely related to the specific hydrodynamic conditions, nutrients, and lighting conditions.

Distributions and potential sources of traditional and emerging polycyclic aromatic hydrocarbons in sediments from the lower reach of the Yangtze River, China

This study investigated the current contamination status and potential sources of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) in the sediments across a wide area of the Yangtze River, spanning nine cities. Fifty-seven sediment samples were collected in 2019, from which 15 t-PAHs and 11 e-PAHs were analyzed using GC-MSD. In addition, organic carbon (OC), total nitrogen (TN), and carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) in sediments were measured to evaluate associations with PAHs contamination. OC, TN, and their stable isotope ratios showed a wide range of site-specific contents and values, indicating high variation in contamination and sources. Concentrations of t-PAHs and e-PAHs in sediments ranged from 0.6 to 200,000 ng g^-1 dry weight (dw) and 1.1 to 20,000 ng g^-1 dw, respectively. Hotspot sites located in Nanjing (PuKou), Taizhou (JingJiang), and Suzhou (ZhangJiaGang). PAHs contamination reflected land use type and human activity in the surrounding area. Positive matrix factorization (PMF) modeling showed that, on average (n = 57), vehicle emissions were the most dominant contribution (57%), followed by petroleum (28%) and fossil fuel combustion (15%). Sites with high PAHs contamination in sediments were of severe ecological risk. Contributions to the potential risks of PAHs were most significant in the order of dibenz[a,h]anthracene, benzo[b]fluoranthene, and benzo[a]pyrene. The primary origin of these compounds appeared to be fossil fuel combustion. The results of this study are expected to provide useful baseline data on the current contamination status and potential sources of traditional and emerging pollutants in the sediments of the Yangtze River, China.

Occurrence, sources, and risk assessment of unconventional polycyclic aromatic compounds in marine sediments from sandy beach intertidal zones

This study investigated the concentrations of polycyclic aromatic compounds (PACs), including parent polyaromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives, in 48 sediment samples from the intertidal region of sandy beaches in Baía de Todos os Santos (BTS), Salvador, State of Bahia, Brazil. The total PAH (∑PAH) concentration, total nitro-PAH (∑nitro-PAH) concentration, and total oxy-PAH (∑oxy-PAH) concentration ranged from 2.11 μg g^-1 dry weight (dw) to 28.0 μg g^-1 dw, 2.58 μg g^-1 dw to 30.2 μg g^-1 dw, and 0.34 μg g^-1 dw to 3.65 μg g^-1 dw, respectively. Elevated concentrations of parent PAHs and nitro-PAHs were found in samples from two sites in BTS, which were also characterized by high percentages of fine-medium sand and low organic matter contents. Potent mutagenic 3-nitrobenzanthrone (3-NBA) was found in 86% of the samples at concentrations ranging from 0.200 μg g^-1 dw to 0.690 μg g^-1 dw. Furthermore, calculations of the benzo[a]pyrene toxicity equivalency (BaPTEQ) indicated that three carcinogenic high-molecular-weight PAHs accounted for 98.7% of the total maximum PAH concentration. Finally, we assessed the possible environmental risks posed to benthic species living in the sediments of BTS. The results showed that the risk quotient for PAHs (RQ_PAHs) was ≥1. In turn, the summed RQ for all PACs (∑RQ_mixture) ranged from 1 to 30, but did not exceed the maximum allowable threshold; thus, the risks posed to benthic species were moderate for all sediment samples.

Remediation of soils and sediments polluted with polycyclic aromatic hydrocarbons: To immobilize, mobilize, or degrade?

Polycyclic aromatic hydrocarbons (PAHs) are generated due to incomplete burning of organic substances. Use of fossil fuels is the primary anthropogenic cause of PAHs emission in natural settings. Although several PAH compounds exist in the natural environmental setting, only 16 of these compounds are considered priority pollutants. PAHs imposes several health impacts on humans and other living organisms due to their carcinogenic, mutagenic, or teratogenic properties. The specific characteristics of PAHs, such as their high hydrophobicity and low water solubility, influence their active adsorption onto soils and sediments, affecting their bioavailability and subsequent degradation. Therefore, this review first discusses various sources of PAHs, including source identification techniques, bioavailability, and interactions of PAHs with soils and sediments. Then this review addresses the remediation technologies adopted so far of PAHs in soils and sediments using immobilization techniques (capping, stabilization, dredging, and excavation), mobilization techniques (thermal desorption, washing, electrokinetics, and surfactant assisted), and biological degradation techniques. The pros and cons of each technology are discussed. A detailed systematic compilation of eco-friendly approaches used to degrade PAHs, such as phytoremediation, microbial remediation, and emerging hybrid or integrated technologies are reviewed along with case studies and provided prospects for future research.

Levels, distributions, and seasonal variations of polycyclic aromatic hydrocarbons (PAHs) in ambient air and pine components

Pine tree (Pinus pinea) components have been used as passive air samples for determining atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations. Our results indicated that pine needles and branches were found to be statistically successful in describing the ambient air. Monthly pine needles, branches (1- and 2-year-old) and ambient air samples were collected for 1 year to identify molecular distributions and temporal concentrations of PAHs in a suburban-industrial area. Annual average Σ₁₄PAH concentrations for pine needles, 1- and 2-year-old branches, and ambient air were 756 ± 232 ng/g DW, 685 ± 350 ng/g DW, 587 ± 361 ng/g DW, and 28.29 ± 32.33 ng/m³, respectively. The order of average Σ₁₄PAH concentrations in the pine tree components was determined as needle > 1-year-old branch > 2-year-old branch. In general, concentrations increased with the rise in the surface area of tree components. In the samples, 3- and 4-ring PAHs were dominant compounds in the ambient air, pine needles, and branches. The annual total fraction of 3- and 4-ring PAHs in the air was 98.5%, while the fraction of 5- and 6-ring PAHs was 1.5%. On the other hand, 3- and 4-ring PAHs in pine needles and branches were 30% or more. The fraction and level of PAHs change with the season. Although needle samples did not show any seasonal trend, PAH levels in other tree components changed with the air temperature. Generally, lower values were observed in warmer seasons in the branch samples. Similarly, ambient air PAH concentrations were higher in the winter season due to heating and adverse meteorological conditions.

Characteristics and source apportionment of polycyclic aromatic hydrocarbons of groundwater in Hutuo River alluvial-pluvial fan, China, based on PMF model

PAH contamination in water environment has become an important water quality problem in China. In this study, groundwater PAHs were monitored in September 2019 at 48 groundwater sites, and statistical analysis and positive matrix factorization (PMF) model were used to analyze the characteristic of PAHs in groundwater and to identify the pollution sources of PAHs in the Hutuo River Basin, Hebei Province, China. The results showed that the concentration of the PAHs in groundwater was low and the total PAHs (∑PAHs) ranged from below detection limit to 260.6 ng/L and with a mean value of 17.7 ng/L. The concentration of PAHs in groundwater was obviously affected by the land use. Based on molecular ratio method, the main source of PAHs in groundwater is the biomass combustion, while the results of PMF source analysis were more accurate and the results showed that the primary sources and contribution rate of PAHs in groundwater were wood, coal, and gasoline sources (41.4%), followed by oil and diesel sources (39.4%), and natural gas combustion (19.2%). There was obvious spatial variation in the contribution of pollution sources to PAHs at the sites of different land uses in this region. The highest contribution of nature gas combustion, oil and diesel sources, and wood, coal, and gasoline combustion to PAHs was found in the urban area (0.617 ng/L), industrial area (0.380 ng/L), and village area (0.379 ng/L), respectively. The results can provide scientific basis for the prevention and control of PAH contamination in groundwater in this area.

Human health and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in sediment of Woji creek in the Niger Delta region of Nigeria

Human health risk was determined by assessing risk due to dermal contact with the sediment and Benzo [a] pyrene -equivalent concentrations (BaP-TEQ- carcinogenic equivalents and BaP-MEQ- mutagenic equivalents). Ecological risk of PAHs in the sediment was determined by comparing PAHs concentrations to effect range low (ERL) and effect range median (ERM); to estimate the risk associated with the combined effects of PAHs, mean ERM quotient (mERMq) was calculated. Results revealed that hazard index (HI) due to dermal contact of the sediment for adults are 596 and 73.84 for children. Similarly, cancer risk for adults was all >10^-1 and was within 10^-3 ≤ 10^-1 for children, for every compound; the sum of cancer risk for adults and children were 8.26 and 1.022 respectively.

Sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary: Source, distribution, and potential toxicity

The source, distribution, and potential toxicity of sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary were investigated. Total concentrations of 17 PAHs in the study area ranged from 34.94 to 580.26 ng/g (mean value 146.31 ng/g). Results of PMF model revealed that mixed vehicle emissions (38.43%), natural gas combustion (24.98%), biomass combustion (20.76%) and coal combustion (15.83%) were sources of these sedimentary PAHs. The ERL/ERM, TEL/PEL and TEC/PEC values showed that the potential toxicity of PAHs was at low to medium level, but the presence of benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) requires more attention and research. Sedimentary PAHs pollution level in the three shoals (East Nanhui Shoal, Jiuduansha Shoal and Hengsha Shoal) was higher than that of the two passages (South Passage and North Passage), which demonstrates the possibility of restoration of the adjacent shoals by dredged soils in terms of PAHs pollution.

Spatial distribution and source identification together with environmental health risk assessment of PAHs along the coastal zones of the USA

Identification of polycyclic aromatic hydrocarbons (PAHs) sources and hot spot areas are the primary driving forces for their control in the environment. This study was performed in the US coastal areas to identify the major sources of PAHs and investigate the spatial distribution associated with carcinogenic PAHs (CPAHs) using a novel spatial forecasting method for the first time in environmental sciences. Diagnostic ratios of PAHs demonstrated the predominance of pyrogenic sources compared to petrogenic sources within the area of study. Five factors were extracted using positive matrix factorization method with respect to 16 priority PAHs, indicating the dominance of pyrogenic versus petrogenic sources mainly as a result of combustion products in the environment. The total toxic benzo[a]pyrene equivalency (TEQ) for all CPAHs ranged from 0.03 to 10,456 ng/g containing a mean of 199 ng/g. The contribution of each CPAH to the total TEQ varied according to the following order: benzo[a]pyrene (65.4%), dibenzo[a,h]anthracene (12%), benzo[b]fluoranthene (10%), benzo[a]anthracene (6%), indeno[1,2,3-c,d]pyrene (6%), benzo[k]fluoranthene (0.5%) and chrysene (0.1%). The spatial analysis by fixed rank kriging (FRK) highlighted a similar pattern associated with all of the CPAHs with higher values in the northern part of New Jersey State. In particular, Passaic River, Upper New York/New Jersey Harbor, Mullica River, Schuylkill River, Newark Bay and Christina River were the most contaminated stations regarding the observed values of CPAHs.