Distribution,source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh,Persian Gulf

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 μg kg^?1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaP_eq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQ^carc) for carcinogenic compounds ranged from 0.01 to 7 μg kg^?1-BaP_eq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.     

Ecological risks of polycyclic aromatic hydrocarbons found in coastal sediments along the northern shores of the Bohai Sea (China)

The total concentrations of 16 United States Environmental Protection Agency (US EPA)-listed polycyclic aromatic hydrocarbons (PAHs) found in coastal and estuarine sediments along the northern shores of the Bohai and Yellow Seas, China, at any study location varied from 0.236 to 8.34 nM g^?1 dry weight (dw). For a given PAH, concentrations varied by one to two orders of magnitude. Ecological risk assessments based on biota–sediment accumulation factors (BSAFs) indicated that the potential ecological hazard of PAHs in the sediments was limited. The average total sediment PAH concentrations were less than the effects range low, indicating that PAHs currently present in the sediments were not harmful to aquatic organisms. The estimated PAH concentration in the aquatic organisms was 0.223 nM g^?1 and posed a limited threat to human health via biological concentration from sediment to harvest of the sea. Assuming no additional PAH inputs, 99% of the 16 PAH molecules currently present in the sediments would be degraded in 40 years.     

汾河流域水系和表层沉积物中多环芳烃的空间变化规律及其生态风险研究

本研究在汾河流域上、中、下游及其部分支流布设29个采样点,对其水体和表层沉积物多环芳烃(PAHs)的空间分布规律及生态风险进行了分析和讨论。结果表明,汾河流域水相中丰水期PAHs总量浓度范围是0.530~16.002μg·L~(-1),平均浓度为(2.738±3.078)μg·L~(-1),枯水期PAHs总量浓度范围是0.588~12.916μg·L~(-1),均值为(2.762±3.132)μg·L~(-1)。就空间分布而言,汾河流域整体呈现上游污染较轻,中下游污染严重的特点。PAHs的组成规律显示,丰水期和枯水期PAHs含量均以低环(2~3环)为主,不同采样期低环PAHs所占比例分别为96.5%和90.4%。与其他15个研究地区水体PAHs含量比较,汾河流域水体中PAHs污染程度的国内外对比处于中等到较高程度的污染。丰水期和枯水期水体中PAHs来源于石油源和植物、木材、煤的燃烧,主要受到流域煤化工、燃煤电厂排放污染物的影响。地表水健康风险评价结果显示,汾河流域丰水期和枯水期分别有13.8%和20.7%的点位存在一定的健康风险。汾河流域沉积相中16种PAHs平均浓度为(3.774±1.987)μg·g-1,其污染主要集中在流域中下游地区。PAHs的组成规律显示,PAHs含量集中在低环(2~3环),约占总量的75%左右。与本研究提到的河流、湖泊及港口沉积物中PAHs含量比较,汾河流域沉积物中PAHs污染程度仍处于中等偏高的污染水平。丰水期沉积相中PAHs以燃烧源和石油源为主,部分来自典型石油类产品的输入。表层沉积物生态风险评价结果显示,对于提出的12种PAHs的生态风险的效应区间低值(ERL值)或效应区间中值(ERM值)以及苯并(b)荧蒽(Bb F)和苯并(k)荧蒽(Bk F)这2类没有最低安全值的PAHs化合物来说,汾河上、中、下游流域均有采样点的PAHs可能存在着对生物的潜在生态风险。通过本研究可全面地了解该流域多环芳烃的空间分布规律及其可能的来源,并且为汾河流域多环芳烃污染的控制和生态风险评价提供科学依据。     

Aliphatic and polycyclic aromatic hydrocarbons in the bottom sediments from Klaipėda Harbour,Lithuania (Baltic Sea)

A total of 22 bottom surface sediment samples were collected from Klaip?da Harbour, Lithuania (Baltic Sea). Sediment parameters, such as grain size and concentrations of total organic carbon, aliphatic hydrocarbons (ALHs) and polycyclic aromatic hydrocarbons (PAHs), were determined. Hydrocarbon contamination levels in the sediments were estimated based on classifications provided in the literature, and potential biological effects were assessed based on the effects range low–effects range median values of the Sediment Quality Guidelines and on the total toxic benzo(a)pyrene equivalent. The results demonstrated that concentrations of PAHs and total aliphatic hydrocarbons in the sediments varied between 1.6 and 5456?ng?g^?1 d.w. and 6.9 and 727?μg?g^?1 d.w., respectively. In most cases, the concentrations of ALHs and PAHs in the sediments indicated low to moderate levels of pollution and were not observed to have any significant adverse effects on living biota. To determine possible sources of hydrocarbons, hydrocarbon compositions were analysed, and ALHs’ and PAHs’ specific diagnostic ratios were calculated. According to the results, the Klaip?da Harbour bottom sediments were dominated by PAHs of pyrogenic origin, whereas the origin of ALHs was mixed, that is, anthropogenic with a biogenic (aquatic and terrestrial) input.     

Risk assessment of human exposure to polycyclic aromatic hydrocarbons via shrimp (<Emphasis Type="Italic">Macrobrachium felicinum</Emphasis>) consumption along the Imo River catchments,SE Nigeria

Shrimp species (Macrobrachium felicinum) collected from estuarine mangrove area of the Imo River is an important route of exposure to polycyclic aromatic hydrocarbons (PAHs). The estuarine associated sediment (EAS) composited sample showed higher TPAH, ΣAlkyl, ΣPAH_carc and ΣPAH_EPA concentrations (550.84, 172.36, 413.17 and 482.11 ng/g dry weight—dw) than their mean concentrations in shrimp samples (509.39 ± 354.21, 31.38 ± 18.49, 52.10 ± 1.35 and 460.06 ± 330.76 ng/g wet weight—ww), respectively. Among the individual PAHs congeners, phenanthrene was the dominant species detected in the EAS accounting for 21.02 % of the total PAH load and the decreasing order of 3- > 2- > 5- > 4- > 6-ring contamination was found. A different pattern predominated by naphthalene was observed for the shrimp species, suggesting that the organisms have different selectivity for a range of PAHs congeners. These variations may be attributed to different degree of bioavailability of these compounds, characteristic sandy lithology of the EAS and the protective capacity of soot particles associated with liquid fossil fuel combustion masking the uptake of high molecular weight PAHs by the organisms. Cancer risk associated with consumption of shrimps in the region was assessed using estimated daily intake (EDI) and compared with standards. The EDI values for naphthalene, benzo(a)pyrene and ∑PAH_carc were lower than the USEPA benchmarks and EFSA levels of concern values for adult and children population, suggesting low probability of developing cancer.     

Spatial distribution and temporal trends of polycyclic aromatic hydrocarbons (PAHs) in water and sediment from Songhua River, China

The spatial and temporal distributions of polycyclic aromatic hydrocarbons (PAHs) in the Songhua River, Harbin, China, were investigated. Seventy-seven samples, 42 water and 35 sediment samples, were collected in April and October of 2007 and January of 2008. The concentrations of total PAHs in water ranged from 163.54 to 2,746.25 ng/L with the average value of 934.62 ng/L, which were predominated by 2- and 3-ring PAHs. The concentrations of total 16 PAHs in sediment ranged from 68.25 to 654.15 ng/g dw with the average value of 234.15 ng/g dw, which were predominated by 4-, 5- and 6-ring PAHs. Statistical analysis of the PAH concentrations shown that the highest concentrations of the total PAHs were found during rainy season (October of 2007) and the lowest during snowy season (January of 2008). Ratios of specific PAH compounds, including fluoranthene/(fluoranthene + pyrene) (Flu/(Flu + Pyr)) and phenanthrene/(phenanthrene + anthracene) (An/(Ant + PhA)), were calculated to evaluate the possible sources of PAH contaminations. These ratios reflected pyrolytic inputs of PAHs in Songhua River water and a mixed pattern of pyrolytic and petrogenic inputs of PAHs in the Songhua River sediments. Ecotoxicological risk levels calculated for PAHs suggested that there were individual PAHs, which can less frequently cause biological impairment in some samples, but no samples had constituents that may frequently cause biological impairment. Total toxic benzo[a]pyrene equivalent of ΣcPAHs varied from 10.03 to 29.7 ng/g dw and from 0.36 to 1.92 ng/g dw for total toxic tetrachlorodibenzo-p-dioxin equivalent. The level of PAHs indicated a low toxicological risk to this area.     

Hydrocarbons contamination and microbial degradation in mangrove sediments of the Niger Delta region (Nigeria)

The distribution of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), and their degradability by bacteria in epipelic and benthic sediments from Qua Iboe Estuary mangrove ecosystem and associated creeks were investigated. The research findings revealed that total aliphatic hydrocarbons in sediments ranged from 16.82 mg·kg ^?1 to 210 mg kg ^?1, wheras total PAHs ranged from 6.30 to 35.55 mg·kg ^?1 dry weight of sediment. Low molecular mass (i.e. the 2–3-ring) PAHs were predominant in almost all the sampling points, whereas the higher molecular masses (4-, 5- and 6-ring PAHs) had the lowest concentrations. In general, the sediment samples ES ₂ (39.7%), ES ₃ (24.8%), BS ₁ (46.7%), BS ₂ (49.9%) and BS ₃ (44.2%) showed<50% contributions of Σ combustion–derived PAH (COMP-PAH) concentration to the Σ PAH concentrations, whereas ES ₁ (57%) contained>50% of COMP-PAHs. Our results have also shown that many mangrove bacteria have strong capacity to utilise Qua Iboe Light (QL) crude oil as the sole source of carbon and energy, while lower number of bacterial species including Bacillus sp., Micrococcus sp., Pseudomonas aeruginosa, Alcaligenes sp. and Flavobacterium sp. exhibited detectable PAHs degradability; and as such may serve as efficient degraders of QL crude oil contamination of mangrove ecosystem.     

厦门湾海域表层沉积物重金属和多环芳烃污染特征及生态风险评价

研究了厦门湾海域表层沉积物中Cu,Pb,Zn,Cr,Cd,Hg和As和16种多环芳烃的分布、来源及潜在的生态风险.结果表明:(1)Cu,Pb和As平均含量均介于效应浓度区间低值(ERL)和效应浓度区间中值(ERM)之间,而大多数站位Zn,Cr,Cd和Hg平均含量则低于ERL值;(2)沉积物多环芳烃(PAHs)以石油或油料燃烧来源为主,PAHs的总量远低于ERL值(4000μg·kg~(-1));(3)重金属与低环PAHs相关性显著,易发生交互作用;(4)利用沉积物平均效应区间中值商法(mERM-Q)进行沉积物生态风险评价发现,筼笃湖表层沉积物对海洋底栖生物可能存在较强的生物毒性风险.     

Sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Biobio River in south central Chile

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment; there are concerns about them due to their toxic properties. Human activities could significantly contribute to the total PAH burden in river sediments. In this work, we document the analysis of PAHs in sediments taken in the middle stretch of the Biobio River in south central Chile. This river is a principal system, draining more than 24,000 km² and subjected to a diverse variety of human-made stressors (pulp mill and urban effluents, agricultural drainage systems, etc). During 2003, several sediment samples were taken in more than 45 sampling sites located in the river’s middle stretch. Due to the granulometric characteristics (mainly sandy sediments), only 17 samples were analyzed, taking into consideration the presence of a fine section within the sediment sample. Using HPLC with fluorescence detection, 15 EPA priority PAHs and perylene were analyzed. The composition of PAHs in the sediment samples is rather similar between sites and levels averaged 104 ± 78 ng g⁻¹ d.w. The highest levels were detected downstream from an industrial discharge. A good correlation was observed between PAH levels and organic carbon content in the tested sediments; however, concentrations above 134 ng g⁻¹ d.w. did not indicate correlation. The samples PAH ratios (Flu/Pyr and Chr/B(a)A) reveal a strong pyrolytic PAH pattern in the sediments tested, supporting evidence indicating that PAHs come mainly from pyrolytic sources. This result contrasts with previous records that have shown a natural influence in the upper basin and a petrogenic pattern near the mouth.     

Polycyclic aromatic hydrocarbons in surface sediments held in experimental mesocosms

Sediment was collected from three locations along a pollution gradient in Narragansett Bay and transplanted to controlled mesocosms. Total hydrocarbons and eleven individual polycyclic aromatic hydrocarbons (PAHs) were measured in these sediments over a period of 394 days. Total hydrocarbon concentrations increased in the “relatively uncontaminated”; (Rhode Island Sound) sediment that was held in the mesocosms, but did not change in the two other sediments. The concentrations of four PAHs: naphthalene, 2‐methyl naphthalene, 1‐methyl naphthalene and biphenyl, decreased in the “contaminated”; (Providence River) sediment during the experiment and the calculated half‐lives for these compounds were 287, 353, 321 and 333 days, respectively.     

Trace elements in surface sediments of the Hooghly (Ganges) estuary: distribution and contamination risk assessment

Our objective was to evaluate distribution and accumulation of trace elements (TEs) in surface sediments along the Hooghly (Ganges) River Estuary, India, and to assess the potential risk with view to human health. The TE concentrations (mg kg^?1 dry weight) exhibited a wide range in the following order: Al (31.801 ± 15.943) > Fe (23.337 ± 7584) > Mn (461 ± 147) > S (381 ± 235) > Zn (54 ± 18) > V (43 ± 14) > Cr (39 ± 15) > As (34 ± 15) > Cu (27 ± 11) > Ni (24 ± 9) > Se (17 ± 8) > Co (11 ± 3) > Mo (10 ± 2) > Hg (0.02 ± 0.01). Clay, silt, iron, manganese and sulphur were important for the accumulation of TE in the sediments as confirmed by factor analysis and Pearson correlation. The accumulation and dispersal of TEs were most likely to be governed by both tide-induced processes and anthropogenic inputs from point and non-point sources. Enrichment factor analysis and geoaccumulation index revealed serious contamination of the sediments with Se and As, while comparing the consensus-based sediment quality guidelines (SQGs), adverse biological effects to benthic fauna might be caused by As, Cu, Ni and Cr. This investigation may serve as a model study and recommends continuous monitoring of As, Se, Cu, Ni and Cr to ascertain that SQGs with respect to acceptable levels of TEs to safeguard geochemical health and ecology in the vicinity of this estuary.     

白洋淀湿地表层沉积物多环芳烃的分布、来源及生态风险评价

对白洋淀湿地表层沉积物15种多环芳烃含量进行了检测.结果表明,其总含量范围为324.6~1738.5ng·g-1,整体来看,白洋淀湿地多环芳烃污染处于中等偏低污染水平.多环芳烃组成主要以2~3环、4环为主,其含量分别占总含量的47.8%、28.6%.白洋淀湿地表层沉积物多环芳烃主要以化石燃料、木柴及生物质低温燃烧来源为主,个别样点受油类排放污染严重.风险评价表明,严重的多环芳烃生态风险在白洋淀湿地表层沉积物中不存在,但是在部分区域某些多环芳烃含量超过了效应区间低值(ERL),可能存在着对生物的潜在危害.     

基于统计方法的辽东湾沉积物中多环芳烃来源特征分析

为研究辽东湾表层沉积物中多环芳烃(PAHs)的来源特征,2014年5月采集了20个辽东湾海域表层沉积物样品,并利用气相色谱质谱联用仪对优先控制的16种PAHs进行测定,采用聚类分析、主成分分析-多元线性回归分析、异构体比值3种统计方法对辽东湾表层沉积物中PAHs来源特征进行了研究。结果表明,辽东湾表层沉积物中PAHs含量范围88.5~199.3 ng·g-1,平均值为(126.3±35.3)ng·g-1,其中,萘、菲和荧蒽是PAHs优势组分。通过统计分析结果表明,辽东湾北部表层沉积物中PAHs含量低于西南部,沉积物中PAHs的来源包括石油燃烧来源、煤炭、木材等生物质燃烧来源和石油来源,其中燃烧来源是主要来源,煤炭、木材等生物质燃烧来源占49.9%,石油燃烧来源和石油来源占50.1%。     

Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau

High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the ²¹⁰Pb dating method and validated with the ¹³⁷Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ₈PAH) in the sediment core ranged from 0.83 to 12 ng/g dw, and the fluxes of the Σ₈PAH were in the range of 2.1–27 g/cm²/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.     

Siphon nipping facilitates lethal predation in the clam Mesodesma mactroides (Reeve, 1854) (Mollusca: Bivalva)

In soft sediment marine communities, fishes frequently bite off extended siphons of buried clams; the consequential shortening of the siphon is known to reduce burial depth of the clams, secondarily increasing their vulnerability to lethal excavating predators. In this study, siphon nipping on the yellow clam, Mesodesma mactroides, was simulated by removing the top 6.6–30% of siphons. This caused a burrow reduction in 25–75%, respectively, compared to control individuals with intact siphons, in field and laboratory trials. To examine subsequent consequences of reduced burial depth, we exposed nipped and intact clams to potential predators in the laboratory simulating the observed natural clam abundance. Artificially nipped clams were consumed twice as much as control clams. The present results suggest that sympatric croppers contribute to the stock recovery failure by facilitation of lethal predation and that re-seeding to increase the local abundance of M. mactroides should be an essential aspect of conservation efforts in South America.     

Concentrations,input prediction and probabilistic biological risk assessment of polycyclic aromatic hydrocarbons (PAHs) along Gujarat coastline

A comprehensive investigation was conducted in order to assess the levels of PAHs, their input prediction and potential risks to bacterial abundance and human health along Gujarat coastline. A total of 40 sediment samples were collected at quarterly intervals within a year from two contaminated sites—Alang-Sosiya Shipbreaking Yard (ASSBRY) and Navlakhi Port (NAV), situated at Gulf of Khambhat and Gulf of Kutch, respectively. The concentration of ΣPAHs ranged from 408.00 to 54240.45 ng g^?1 dw, indicating heavy pollution of PAHs at both the contaminated sites. Furthermore, isomeric ratios and principal component analysis have revealed that inputs of PAHs at both contaminated sites were mixed-pyrogenic and petrogenic. Pearson co-relation test and regression analysis have disclosed Nap, Acel and Phe as major predictors for bacterial abundance at both contaminated sites. Significantly, cancer risk assessment of the PAHs has been exercised based on incremental lifetime cancer risks. Overall, index of cancer risk of PAHs for ASSBRY and NAV ranged from 4.11 × 10^?6–2.11 × 10^?5 and 9.08 × 10^?6–4.50 × 10^?3 indicating higher cancer risk at NAV compared to ASSBRY. The present findings provide baseline information that may help in developing advanced bioremediation and bioleaching strategies to minimize biological risk.     

土壤与沉积物对多环芳烃类有机物的吸附作用

吸附作用是疏水性有机物在土壤和沉积物环境中的重要迁移转化行为之一。多环芳烃是环境中一种重要的疏水性有机污染物。文章着重阐述了多环芳烃类有机物在土壤和沉积物中有机质和粘土矿物吸附机理，指出土壤、沉积物有机质的结构异质性是导致非线形吸附的重要原因；分析了影响多环芳烃吸附过程的诸多因素，并提出该研究领域存在的问题以及今后发展的方向。     

广东典型湿地环境沉积物及鱼体中多环芳烃的污染特征及风险评估

为了解广东典型湿地环境表层沉积物及鱼体中多环芳烃(PAHs)的污染特征,分别于2014年10月和2015年4月采集沉积物及鱼类样品,分析其中16种US EPA优控多环芳烃的主要来源和风险。结果表明,广东典型湿地环境表层沉积物中多环芳烃的含量范围为139.4～1 134.3 ng·g~(-1)干重,鱼类肌肉中多环芳烃含量范围为11.1～33.9 ng·g~(-1)湿重。表层沉积物中有机碳与不同环数的多环芳烃含量均呈现显著的正相关关系。来源分析的结果表明,研究区域表层沉积物中多环芳烃的主要来源为石油排放及燃烧来源的混合。风险评估的结果表明,该区域表层沉积物中多环芳烃存在一定的生态风险,需引起重视;通过食用鱼类造成的致癌风险为2.25×10~(-6)～4.23×10~(-6),略高于美国环保局(US EPA)推荐的可接受风险(10~(-6)),存在一定的潜在致癌风险。对于成年人来说,研究区域鱼类肌肉中多环芳烃产生致癌风险允许的最大日食用量(CR_(lim))范围为124.5～234.6 g·d~(-1),尽管食用这几种鱼的致癌风险不大,居民摄入时仍应加以控制。     

Assessment of persistent organic pollutants in soil and sediments from an urbanized flood plain area

Polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and phenolic compounds (PCs) are persistent organic compounds. Contamination of these potentially toxic organic pollutants in soils and sediments is most studied environmental compartments. In recent past, studies were carried out on PAHs, OCPs and PCs in various soils and sediments in India. But, this is the first study on these pollutants in soils and sediments from an urbanized river flood plain area in Delhi, India. During 2018, a total of fifty-four samples including twenty-seven each of soil and sediment were collected and analyzed for thirteen priority PAHs, four OCPs and six PCs. The detected concentration of ∑PAHs, ∑OCPs and ∑PCs in soils ranged between 473 and 1132, 13 and 41, and 639 and 2112 µg/kg, respectively, while their concentrations in sediments ranged between 1685 and 4010, 4.2 and 47, and 553 and 20,983 µg/kg, respectively. PAHs with 4-aromatic rings were the dominant compounds, accounting for 51 and 76% of total PAHs in soils and sediments, respectively. The contribution of seven carcinogen PAHs (7CPAHs) in soils and sediments accounted for 43% and 61%, respectively, to ∑PAHs. Among OCPs, p, p’-DDT was the dominant compound in soils, while α-HCH was found to be dominated in sediments. The concentrations of ∑CPs (chlorophenols) were dominated over ∑NPs (nitrophenols) in both the matrices. Various diagnostic tools were applied for the identification of their possible sources in soil and sediments. The observed concentrations of PAHs, OCPs and PCs were more or less comparable with the recently reports from various locations around the world including India. Soil quality guidelines and consensus-based sediment quality guidelines were applied for the assessment of ecotoxicological health effect.

     

Sources and spatial distribution of polycyclic aromatic hydrocarbons in coastal sediments of the Basque Country (Bay of Biscay)

This contribution characterises the sources and distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Basque coast (Bay of Biscay). Different source characterisation approaches (i.e. GIS assisted-chemometrics, PAH diagnostic ratios and analyses of composition profiles) were used in combination to successfully identify the factors determining the origin and distribution of PAHs. Urban/industrial combustion processes were identified as the main PAH source. However, the analysis of PAH composition patterns and diagnostic ratios identified secondary natural and petrogenic PAH sources on small spatial scales. The median ∑18PAH concentration ranged from 66 μg kg^?1 (d.w.) to 7021 μg kg^?1 (d.w.). The Ibaizabal estuary, which supports most of the anthropogenic pressure in the region (i.e. urban development, industrialisation, commercial and recreational harbours), also showed the highest PAH concentrations. On the shelf, human activities, hydrodynamic conditions and geomorphological features led to spatial differences in the PAH concentrations among sectors: the offshore and west sectors were characterised by higher concentrations, while the lowest values were found in the mid and east sectors. The results enhance the knowledge on PAH-related contamination processes and could be used to support the environmental assessment process required under current European marine legislation.