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Identifying the sources of polycyclic aromatic hydrocarbons (PAHs) in complex environmental matrices is essential for understanding the impact of combustion-related human activities on the environment. Since the turn of the century, advances in analytical capability and accuracy of accelerator mass spectrometry (AMS) have made it possible to accurately determine the source apportionment of PAHs based on their radiocarbon ( 14 C) mass conservation. This also allows us to trace the environmental transport processes of PAHs from the perspective of molecular 14 C. However, natural environmental matrices have very low concentrations of PAHs (ppb to ppm level). To meet the requirements of carbon weight for 14 C measurement by AMS, trace PAHs in complex environmental matrices must be enriched thousands of times, and then higher purity individual PAH molecules should be obtained through a series of complex purification procedures. Therefore, the technical difficulty is the main challenge in expanding the application of compound-specific 14 C analysis in environmental science. This article reviews the detailed pretreatment procedures for 14 C measurement of specific PAHs, including sample enrichment, extraction and purification of aromatic components, preparation of compound-specific PAHs by preparative capillary gas chromatography, graphitization of samples with ultra-small carbon content, and relevant quality control and assurance procedures. This study aims to help environmental geoscientists understand the technical process of 14 C analysis of PAHs and inspire new scientific questions related to environmental science. To our knowledge, this is the first comprehensive review of the technical method of compound-specific 14 C analysis for PAHs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Aquatic particles and organic carbon (OC) regulate the occurrence and transport of hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) in water-suspended particle-sediment interfaces. Conventional studies on the mechanisms regulating the relationships between PAHs and total particles/OC have ignored micro-scale regulatory factors such as particle size and OC composition. Field research in the eutrophic shallow Lake Taihu, China, revealed that the fine particle fractions 2.7-10 μm in diameter had stronger PAH adsorption capacity and significantly regulated PAH particle size distribution and water-particle partitioning. Selective PAH biodegradation by planktonic microorganisms probably significantly weakened the capacity of the coarse fractions to regulate PAHs. OC fragments at different temperature gradients had markedly different influences on the particle size distribution of PAHs. High-temperature pyrogenic OC fractions (part of black carbon) were the principal OC regulatory factors for medium-to high-molecular-weight PAHs. However, the OC fragments did not directly affect the particle distribution of low-molecular-weight PAHs. During particle deposition and burial, microbial PAH utilization and efficiency probably regulated the burial potential of various hydrophobic PAH species. Biodegradation of relatively less hydrophobic PAHs with octanol-water partition coefficients (log K ow ) < 5.8 showed an increasing trend with decreasing PAH hydrophobicity. Biological pump action of the relatively higher hydrophobic PAH species (log K ow > 5.8) showed a decreasing trend with increasing PAH hydrophobicity. The discoveries of the present work further clarified the mechanisms of PAH partitioning and burial in a eutrophic shallow lake and collectively provides a valuable reference for modeling the transport and dispersal mechanisms of hydrophobic, particle-bound organic contaminants in other aquatic ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

As typical chemical indicators of the Anthropocene, polycyclic aromatic hydrocarbons (PAHs) and their environmental behavior in urban estuaries can reveal the influence of anthropogenic activities on coastal zones worldwide. In contrast to conventional approaches based on concentration datasets, we provide a compound-specific radiocarbon ( 14 C) perspective to quantitatively evaluate the sources and land‒sea transport of PAHs in an estuarine‒coastal surficial sedimentary system impacted by anthropogenic activities and coastal currents. Compound-specific 14 C of PAHs and their 14 C end-member mixing models showed that 67-73% of fluoranthene and pyrene and 76-80% of five- and six-ring PAHs in the Jiulong River Estuary (JRE, China) originated from fossil fuels (e.g., coal, oil spill, and petroleum-related emissions). In the adjacent Western Taiwan Strait (WTS), the contributions of fossil fuel to these PAH groups were higher at 74-79% and 84-87%, respectively. Furthermore, as a significant biomarker for source allocation of terrigenous organic matter, perylene, a typical five-ring PAH, and its land‒sea transport from the basin through the JRE and finally to the WTS was quantitatively evaluated based on the 14 C transport models. In the JRE, fluvial erosions and anthropogenic emissions affected the 14 C signature of perylene (Δ 14 C perylene , -535 ± 5‰) with contributions of > 38% and < 62%, respectively. From the JRE to the WTS, the decreased Δ 14 C perylene (-735 ± 4‰) could be attributed to the long‒range transport of "ocean current-driven" perylene (-919 ± 53‰) with a contribution of 53 ± 8%. This compound-specific 14 C approach and PAH transport model help provide a valuable reference for accurately quantifying land‒sea transport and burial of organic pollutants in estuarine‒coastal sedimentary systems., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2021. Published by Elsevier Ltd.)

In order to investigate the impacts of dam-related water impoundment on the spatial-temporal variations and transport of anthropogenic organic pollutants, 15 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed in water samples from the Shuikou Reservoir (SKR) of the Minjiang River. The SKR was formed after the construction of the Shuikou Dam, which is the largest hydropower station in Southeast China. The water samples were collected from the backwater zone of the SKR, in both the wet and dry seasons, corresponding to the drainage and impoundment periods of water flow, respectively. The concentrations of the dissolved PAHs in surface water from the wet season (average of 161 ± 97 ng L -1 ) were significantly higher (ANOVA, p < 0.01) than those from the dry season (average of 43 ± 21 ng L -1 ). PAH concentrations in the SKR decreased from upstream (industrialized cities) to downstream (rural towns or counties), indicating high PAH loads caused by intensive urbanization effects. The high proportions of 3-ring PAHs in the wet season were from local sources via surface runoff; while the elevated proportions of 4- to 6- ring PAHs in the dry season reflected atmospheric deposition emerged of these PAHs and/or volatilization of 3-ring PAHs enhanced. Molecular diagnostic ratios of PAH isomers in multimedium and principal component analysis indicated that PAH presence in the SKR was mainly attributed to pyrogenic origin. The isomeric ratios of fluoranthene to fluoranthene plus pyrene in the wet season were homogeneous, implying that there were continuous new inputs along the riverine runoff. However, these ratios showed spatial downward trend in the dry season, indicating continued degradation of PAHs occurred along the transport path during the impoundment period. The input and output fluxes of PAHs in the SKR were 5330 kg yr -1 and 2991 kg yr -1 , revealing that the reservoir retained contaminants after impoundment of the hydropower dam., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Riverine runoff is one of the most important pathways of pollutants entering the oceans. To study the seasonal variations, spatial transports, sources and mass fluxes of polycyclic aromatic hydrocarbons (PAHs) from the subtropical Jiulong River watershed to estuary, water samples were collected in wet and dry seasons. PAH concentrations showed significant temporal-spatial variations (ANOVA, p < 0.05). In the watershed, PAH concentrations in wet season (48.6 ± 18.2 ng L -1 ) were significantly lower than in dry season (90.3 ± 18.5 ng L -1 ). In contrast, estuarine PAH concentrations in wet season (67.1 ± 24.6 ng L -1 ) were significantly higher than in dry season (27.4 ± 10.6 ng L -1 ) (p < 0.0001). The spatial variations of PAH concentrations in wet and dry seasons reflected positive and restricted transport processes occurred in the river. These findings might be subjected to seasonal changes in precipitation, water discharge, hydrodynamic conditions, and human activities. The compositional patterns of PAHs illustrated that fluorene and phenanthrene were the dominant compounds in the watershed, while phenanthrene was predominant in the estuary. Source analysis by molecular diagnostic ratios and PMF model indicated that fossil fuel and biomass combustion and petroleum both contributed to the presence of PAHs, and the high contributions of pyrogenic PAHs might be related to urban rainstorm runoff in winter and atmospheric inputs in winter. Although the estimated flux of PAHs from watershed to estuary was about 676 kg yr -1 with a low level by comparing the data obtained in the worldwide, continue concern of PAHs in the Jiulong River is recommended due to the intense human activities., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

On July 27, 2003, a spill of approximately 31,000 tons of Iranian light crude oil affected the coast of Karachi, Pakistan. Approximately 11 years after the spill, we analyzed polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues (alkyl-PAHs) as the indicators to evaluate the residual effect of oil spill to the sediment along the Karachi coast. The total concentrations (dry weight) of parent PAHs and alkyl-PAHs ranged from 121.9 to 735.4 and 42.3-1149.9 ng/g, respectively. The estuary and harbor were the two regions with the highest levels of PAHs in the sediment. Conversely, sedimentary PAHs in the oil spill areas and remote coastal areas showed significantly lower levels. Although the results of the source identification indicated the up to 75.2% of the contribution from petroleum and its derivatives, this could only reflect the direct impact of the Karachi city on the presence of PAHs in the coastal sedimentary environment and did not indicated that the oil spill continues to stay 11 years later. Compared with 11 years ago, the sharply reduced PAH content, great changed composition, and the degradation driven trend of diagnostic ratios all indicated a sharp decrease in the influence of PAHs caused by the oil spill. Finally, the ecological risk caused by the PAH residual in the marine sedimentary ecosystem had disappeared along the Karachi coasts, Pakistan., (Copyright © 2019. Published by Elsevier Ltd.)

On the basis of the application of compound-specific radiocarbon analysis (CSRA) and air-water exchange models, the contributions of fossil fuel and biomass burning derived polycyclic aromatic hydrocarbons (PAHs) as well as their air-water transport were elucidated. The results showed that fossil fuel-derived PAHs (an average contribution of 89%) presented the net volatilization process at the air-water interface of the Taiwan Strait in summer. Net volatile fluxes of the dominant fluorene and phenanthrene (>58% of the total PAHs) were 27 ± 2.8 μg m -2 day -1 , significantly higher than the dry deposition fluxes (average 0.43 μg m -2 day -1 ). The Δ 14 C contents of selected PAHs (fluorene, phenanthrene plus anthracene, fluoranthene, and pyrene) determined by CSRA in the dissolved seawater ranged from -997 ± 4‰ to -873 ± 6‰, indicating that 89-100% (95 ± 4%) of PAHs were supplied by fossil fuels. The South China Sea warm current originating from the southwest China in summer (98%) and the Min-Zhe coastal current originating from the north China in winter (97%) input more fossil fuel PAHs than the Jiulong River estuary (90%) and Xiamen harbor water (93%). The more radioactive decayed 14 C of fluoranthene (a 4-ring PAH) than that of phenanthrene and anthracene (3-ring PAHs) represented a greater fossil fuel contribution to the former in dissolved seawater.

Coastal upwelling prevails in the coast of Hainan Island, the northern South China Sea (SCS) during summer. We studied the influences of the upwelling on the horizontal and vertical transport of terrigenous polycyclic aromatic hydrocarbons (PAHs). PAHs in dissolved and suspended particulate phase of water samples were determined in the upper (depth < 1 m) and water column (depth > 10 m). PAH levels decreased sharply from inshore to offshore to open sea. The results showed that terrestrial input was the main source of coastal PAHs. Perylene, an important indicator of land plant-derived PAH, showed the significant correlation with PAHs (p < 0.005). This implied that fluvial transport was the primary pathway of terrigenous PAHs into the coast of northern SCS. Variations of the concentrations, compositions and diagnostic ratios of PAHs, accompanied the partition equilibrium in the water column, could indicate the selective degradation of PAHs by the plankton affected by upwelling. Different from the "traditional" transport pathway of PAHs in the water column (surface enrichment-depth depletion distribution), the upwelling could provide the original driver to elevate the upward diffusion of sediment entrained contaminants towards the intermediate even the upper waters. It could also enhance the outward diffusion of terrigenous PAHs accompanied by the offshore transport of the upper waters. Therefore, the transport pathway of PAHs can be summarized by the coastal upwelling rising PAHs with their subsequent transport offshore and settling in the adjacent open sea., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To study the spatial distributions and seasonal differences of concentrations, source identification, and phase partitioning of polycyclic aromatic hydrocarbons (PAHs) in surface water, intensive sampling was carried out along the marginal seas of China in four seasons. In the northern South China Sea (SCS), the highest PAH levels occurred in the summer (July to August) and autumn (October to November). In the East China Sea (ECS) and the Yellow Sea, the highest occurred in the summer (August) and winter (December). In all areas, the lowest PAH levels were found in the spring (May to June). The estimated mass inventory of PAHs in the surface water (0-5 m) of the northern SCS and ECS accounted for less than 8% of PAHs outflow into the offshore environment. That showed the consistent seasonal variation with PAHs levels. Land- and ocean-based emissions, surface runoff, and the open seawater dilution were the most important environmental factors influencing the seasonal heterogeneity and the spatial distributions of PAH in the surface water. The decline of observed organic carbon normalized partition coefficients in the four seasons was probably affected by the presence of submicrometer-sized soot particles accompanying the PAH outflow from China.

Historical records of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analyzed in two dated sediment cores (DH05 and DH11) collected from the continental shelf of the East China Sea (ECS) to investigate the influence of anthropogenic activities on marine sediment over the past century. The concentrations and fluxes of 15 PAHs were in the range of 28.6-96.5 ng g -1 and 7.6-35.2 ng cm -2 yr -1 in DH05 (1920s-2009), 18.8-76.4 ng g -1 and 13.9-30.9 ng cm -2 yr -1 in DH11 (1860s-2009). The sedimentary records of PAHs in the two cores generally reflected the economic development and energy consumption change in China. Identification of sources suggested that PAHs in ECS were predominantly from petrogenic origin and various combustion sources. A change of source from low- and moderate-temperature combustion to high-temperature combustion process was observed. Although a production ban of technical HCH and DDT was imposed in China in 1983, their sedimentary fluxes display increasing trends or strong rebounds from 1980s to 1990s as recorded in the core profiles. High proportions of DDD + DDE and γ-HCH suggested those OCPs mainly derived from early residuals. Temporal trends of PCBs presented relative high levels from 1970s to 1980s and high proportions of PCB congeners with 3-6 chlorines atoms indicated industrial sources., (Copyright © 2016 Elsevier Ltd. All rights reserved.)