Partitioning and sources of PAHs in wastewater receiving streams of Tianjin,China

Polycyclic aromatic hydrocarbons (PAHs) partitioning among dissolved phase, suspended particulate matter, pore water, and sediment was studied in one moderately contaminated river (Yongding New River) and two highly contaminated drainage canals (South Drainage Canal and North Drainage Canal) of Tianjin, China. PAHs concentrations in sediment (ranged from 0.2 to 195 μg/g) showed positive relations with both total organic carbon contents (ranged from 0.7% to 31.1%, dw) and black carbon contents (ranged from 0.1% to 2.1%, dw) in the sediments. Moreover, most of the measured organic carbon normalized partition coefficients of PAHs in the three streams were 0.76 to 1.54 log units higher than the predicted values. These indicated that strong and nonlinear sorption of PAHs by carbonaceous geosorbents such as black carbon (BC) existed in the streams, and BC was an important part of the carbonaceous particles controlling the partitioning of PAHs in the sediments of this study. PAH component ratio analyses suggested that PAHs in the three streams, effluent samples from wastewater treatment plants, and soil samples by the riverbank had similar main sources, which is coal/petroleum combustion. We suggested the transportation and transformation of both carbonaceous particles and PAHs during wastewater treatment process, surface runoff, etc, should be studied further in order to make decisions on PAHs controlling measures.     

Occurrence, source apportionment and toxicity assessment of polycyclic aromatic hydrocarbons in surface sediments of Chaohu, one of the most polluted lakes in China

In order to evaluate the effect of local anthropogenic activities on Chaohu Lake, one of the most eutrophicated lakes in China, surface sediments have been collected from the whole lake with 0.05 × 0.05 degree latitude/longitude resolution and in the estuaries of three main inflowing rivers. The concentrations of the 28 polycyclic aromatic hydrocarbons (PAHs) determined were in a range 82.4-13,000 ng g(-1) with an average value of 1670 ng g(-1) dry weight for total 28 PAHs (referred to as Σ(28)PAH). Amongst the 28 PAHs, 16 are listed as high priority PAHs by the USEPA and they were in the range of 60.8-10,200 ng g(-1) with an average value of 1230 ng g(-1) for the total of them (referred to as Σ(16)PAH); 7 are known as carcinogenic PAHs and their levels ranged from 34.2 to 6400 ng g(-1) with an average of 815 ng g(-1) in total (referred to as Σ(7)PAH). Chaohu Lake was considered significantly polluted by PAHs through the comparison with the PAH burdens in fresh-water lakes both in China and worldwide. Toxic units (TUs) evaluation showed some sampling locations possibly were over the median lethal level for benthic invertebrate. The highest PAH concentrations were found in sediments from the Nanfei River estuary, suggesting the major contributor of PAHs contamination to the lake. The PAHs with four and five rings were found to be dominant among the PAHs detected in all of the sediment samples, and perylene was the most abundant. Σ(16)PAH had a good correlation with those PAHs from pyrogenic sources, such as anthracene and phenanthrene, but a poor correlation with perylene. The results demonstrated that the environmental behavior of PAHs from pyrogenic sources is significantly different to that of perylene from diagenetic sources. The PAHs in sediments were mainly from traffic-related emission by qualitatively assessing with the diagnostic ratios of PAH isomers, and the ratios for low molecular weight PAHs were strongly altered during their transport.     

Aliphatic and polycyclic aromatic hydrocarbons in the surface sediments of the Mediterranean: assessment and source recognition of petroleum hydrocarbons

Coastal marine sediment samples were collected from ten sampling stations along the Egyptian Mediterranean coast in April 2010. All sediment samples were analyzed for aliphatic (C7 to C34) and polycyclic aromatic hydrocarbons (PAHs) as well as total organic carbon (TOC) contents and grain size analysis. Total aliphatic hydrocarbons ranged from 1621.82 to 9069.99 ng/g (dry weight), while aromatic hydrocarbons (16 PAHs) varied between 208.69 and 1020.02 ng/g with an average of 530.68?±?225.86 ng/g?dwt. Good correlations observed between certain PAH concentrations allowed to identify its origin. The average TOC percent was varied from 0.13 to 1.46 %. Principal component analysis was used to determine the sources of hydrocarbon pollutants in sediments of Mediterranean. Additionally, special PAHs compound ratios suggest the petrogenic origins.     

The Distribution and Sources of Polycyclic Aromatic Hydrocarbons in Surface Sediments Along the Egyptian Mediterranean Coast

Coastal marine sediment samples were collected from 31 sampling stations along the Egyptian Mediterranean Sea coast. All sediment samples were analyzed to determine aliphatic and polycyclic aromatic hydrocarbons (PAHs) as well as total organic carbon (TOC) contents and grain size analysis. Total concentrations of 16 EPA-PAHs in the sediments were varied from 88 to 6338 ng g⁻¹ with an average value of 154 ng g⁻¹ (dry weight). However, the concentrations of total aliphatic were varied from 1.3 to 69.9 ng g⁻¹ with an average value of 15.6 ng g⁻¹ (dry weight). The highest contents of PAHs were found in the Eastern harbor (6338 ng g⁻¹), Manzala (5206 ng g⁻¹) and El-Jamil East (4895 ng g⁻¹) locations. Good correlations observed between a certain numbers of PAH concentrations allowed to identify its origin. The average total organic carbon (TOC) percent was varied from 0.91 to 4.54%. Higher concentration of total pyrolytic hydrocarbons (∑COMB) than total fossil hydrocarbons (∑PHE) declared that atmospheric fall-out is the significant source of PAHs to marine sediments of the Egyptian Mediterranean coast. The selected marked compounds, a principal component analysis (PCA) and special PAHs compound ratios (phenanthrene/anthracene vs fluoranthene/pyrene; ∑COMB/∑EPA-PAHs) suggest the pyrogenic origins, especially traffic exhausts, are the dominant sources of PAHs in most locations. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed in the harbors due to petroleum products deliveries and fuel combustion emissions from the ships staying alongside the quays.     

Polycyclic aromatic hydrocarbons in river sediments from the western and southern catchments of the Bohai Sea, China: toxicity assessment and source identification

The concentration, distribution, and origin of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were investigated in river sediments from the western and southern catchments of the Bohai Sea, China. A toxicity assessment of 28 sediment samples collected from 15 main rivers was conducted by utilizing threshold and probable effect concentrations (TEC and PEC, respectively) derived from consensus-based sediment quality guidelines. The concentrations of total PAHs (∑PAH₁₆) ranged from 0.14 to 10,757 μg/kg dry weight (mean?=?1,368.6 μg/kg). The high concentrations of PAHs found in Binhai New Area of Tianjin and Binzhou City are likely the result of rapid population and heavy industry growth, resulting in elevated point and nonpoint source inputs of PAHs. Of the samples collected, samples 1 and 10 (7.1 % of the total) were categorized as toxic since some of the PAH concentrations exceeded the corresponding PECs. Twenty samples were classified as nontoxic, with both the individual PAH and the∑PAH₁₆ concentrations falling below the corresponding TECs. Analyses of selected PAH isomer ratios aided in the identification of PAH origins, allowing for a discrimination between pyrogenic and petrogenic sources. Spatial variability confirmed source heterogeneity within the study area. The most significant PAH-associated contamination was found in the Beitang River and Ji Canal, which are located in Binhai New Area. The magnitude of contamination and the likelihood of an ongoing influx of PAHs support the need for a better understanding of pollution sources and methods for both control and sediment restoration.     

The distribution and composition of hydrocarbons in sediments from the Fladen Ground, North Sea, an area of oil production

The distribution and composition of hydrocarbons in sediment from the Fladen Ground oilfield in the northern North Sea have been investigated. The total PAH concentrations (2- to 6-ring parent and alkylated PAHs, including the 16 US EPA PAHs) in sediments were relatively low (<100 microg kg(-1) dry weight). The PAH, the Forties crude and diesel oil equivalent concentrations were generally higher in sediment of fine grain size and higher organic carbon concentration. PAH distributions and concentration ratios indicated a predominantly pyrolytic input, being dominated by the heavier, more persistent, 5- and 6-ring compounds, and with a high proportion of parent PAHs. The n-alkane profiles of a number of the sediments contained small, high boiling point, UCMs, indicative of weathered oil arising from a limited petrogenic input. The geochemical biomarker profiles of the sediments that contained UCMs showed a small bisnorhopane peak and a high proportion of norhopane relative to hopane, indicating that there was contamination from both Middle Eastern and North Sea oils. Therefore contamination was not directly as a result of oil exploration activity in the area. The most likely source of petrogenic contamination was from general shipping activity.     

The polycyclic aromatic hydrocarbon and geochemical biomarker composition of sediments from sea lochs on the west coast of Scotland

Sediments from twelve sea lochs on the west coast of Scotland were analysed for parent and branched 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs), n-alkanes and geochemical biomarkers (triterpanes). Where possible at least fourteen sediment samples were collected at random from each sea loch. All sea lochs were remote, most had limited industrial and urban inputs, although all had fish farms. Four lochs had moderate total PAH concentrations and eight lochs had high total PAH concentrations. Total PAH concentration was related to organic carbon content and particle size distribution, with sandier sediments having lower PAH concentrations. The highest total PAH concentrations, normalised for organic carbon, were in Loch Linnhe and Ballachulish Bay (Loch Leven), close to an aluminium smelter. PAH concentration ratios showed that pyrolysis was the main source of PAHs in most lochs. Only sediments from Loch Clash showed evidence of petrogenic input based on their geochemical biomarker (triterpane and sterane) and n-alkane profiles. PAH profiles were similar across lochs apart from Loch Linnhe and Ballachulish Bay, which had a greater proportion of heavy parent PAHs. West coast sediments had a smaller proportion of heavy PAHs than sediments collected from voes in Shetland and a smaller proportion of alkylated PAHs relative to sediments collected from coastal waters around Orkney.     

Concentrations of polycyclic aromatic hydrocarbon in the surface sediments from inter-tidal areas of Kenting coast,Taiwan

The main objective of this study was to investigate the concentrations of polycyclic aromatic hydrocarbons (PAHs) in inter-tidal sediments of the Kenting coast, Taiwan, to assess the levels and origin of PAHs, and to provide useful information on the potential ecological risk of PAHs to benthic organisms. The total concentrations of 38 PAHs ranged from 0.2 to 493 ng/g dry weight. The high variation in total PAH concentrations was caused by the sand content of the sediment in the area. Compared with other coasts and bays in the world, the concentrations of PAHs in the inter-tidal surface sediment of the Kenting coast is low to moderate. Based on the sediment quality guidelines, the total PAH concentrations were below the effects range low value, indicating that the PAH levels in the Kenting area were within minimal effects ranges for benthic organisms. Principal component analysis and isomer ratios were analyzed to identify the contamination source in the inter-tidal surface sediment of the Kenting coast. The results of compounds’ pattern and origin analysis suggest that the source of PAHs in the inter-tidal surface sediment of the Kenting coast is the combustion of petroleum and biomass.     

Distribution and partitioning of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons between water, suspended particulate matter, and sediment in harbours of the West coastal of the Gulf of Tunis (Tunisia)

Harbours of La Goulette, Rades and Sidi Bou Said are considered as the principal largest and most important port in the Gulf of Tunis characterised by a direct influence of different activities (sailing, industry and fishing) to the Mediterranean Sea. Due to their social and economic impact, a comprehensive assessment of the spatial distribution and partitioning of 24 polycyclic aromatic hydrocarbons (PAHs) and 18 aliphatic hydrocarbons (AHs) in summer and in winter among overlying water, suspended particulate matter (SPM) and surface sediments is essential. Distribution of hydrophobic organic contaminants in abiotic compartments is important for describing their transfer and fate in aquatic ecosystems and to identify the potential danger due to mobilization of contaminants produced by managing of the same sediments. Total organic carbon (TOC) contents range between 4.3% and 6.5%, with an average value of 5.9% in summer, and between 2.3% and 9.6%, with an average value of 6.1% in winter. The average concentrations of ΣPAH in winter and in summer were respectively 703.1 ng L?1 and 378.4 ng L?1 in seawater, 4599.1 ng g?1 and 3114 ng g?1 in SPM, and 1507.6 ng g?1 dw (dry weight) and 1294.6 ng g?1 dw in surface sediment. For ΣAH the average concentrations in winter and in summer were respectively 701 ng L?1 and 741.7 ng L?1 in seawater, 6743.5 ng g?1 and 6282.9 ng g?1 in SPM, and 4971.3 ng g?1 and 4588.1 ng g?1 in surface sediment. Higher PAH and AH concentrations were observed in SPM than in surface sediment. SPM and water were dominated by PAH with low molecular weight, while for sediment low and high molecular weight PAHs were present. PAH and AH fingerprint ratios, such as pristane to phytane (Pr/Ph), phenanthrene to anthracene (Phe/An) and fluoranthene to pyrene (Fl/Py), suggest that hydrocarbons in all harbours may originate from both pyrolytic and petrogenic sources derived from discharge of untreated sewage and wastewater or from direct input by ship traffic in the area. The results showed significant difference (ANOVA, p < 0.05) for hydrocarbon mean concentrations between all harbours studied and between different matrixes.     

Measurement of organic contaminants and biological effects in Scottish waters between 1999 and 2005

Concentrations of organic contaminants were determined in sediment and fish collected annually at six sites around Scotland between 1999 and 2005, as part of the UK National Marine Monitoring Programme. Polycyclic aromatic hydrocarbons (PAHs) and chlorobiphenyls (CBs) were measured in sediment, while CBs and ethoxyresorufin-O-deethylase (EROD) activities were measured in the fish. Highest PAH concentrations in sediment were found at sites where higher coastal influences would be expected (e.g., Clyde and Solway) and four of the six sites gave PAH concentrations above OSPAR background assessment concentrations (BACs). A significant downward trend in the median total PAH concentrations, normalised to total organic carbon (TOC), was found at one of the six sites (Minches). The PAH profiles at all sites were consistent over the 6 year period, indicating that the sites are relatively stable and PAH sources are not changing. There was an indication of a greater petrogenic input on the west coast, with sediment from the Clyde, Solway and Minches having a greater proportion of 2- and 3-ring PAHs and a lower proportion of 5-ring PAHs. CB concentrations at all sites were low compared with UK estuarine sites and similar to sediment from more remote areas: however, BACs were exceeded. No significant trends were detected in either the sediment CB concentrations or patterns at any of the six sites. CB concentrations were significantly higher in fish liver collected from the Clyde. Concentrations at the other five sites were low, with the majority of samples having concentrations for the ICES7 CBs of <500 microg kg(-1) lipid weight. However, individual CB concentrations were still above the BACs. Hepatic EROD activities were measured in male plaice from 2002-2005 and were generally low (<10 pmol min(-1) mg protein(-1)). No temporal trends were detected in either CB concentrations or the EROD activity.     

中国表层水体沉积物中多环芳烃源解析及评价

采用索氏提取气相色谱-质谱法测定中国6个重点水体表层沉积物中16种多环芳烃的含量。各化合物含量范围分别为长江6.20~163 ng/g、淮河7.90~249 ng/g、海河12.1~401 ng/g、松花江5.75~152 ng/g、太湖29.1~2 810 ng/g和滇池19.1~795ng/g;16种多环芳烃的总量分别为：长江1 147 ng/g、淮河1 723 ng/g、海河2 595 ng/g、松花江793 ng/g、太湖12472 ng/g、滇池3 714 ng/g,属中等污染水平。利用特征分子比值法分析结果表明6条水体表层沉积物中PAHs均可能以燃料（包括柴油、汽油、煤、木材）燃烧以及焦化污染为主。淮河和滇池还可能存在轻微石油泄漏污染。利用沉积物质量基准法（SQGs）和沉积物质量标准法分别对6条水体表层沉积物中多环芳烃的风险评估表明严重的多环芳烃生态风险在这些水体表层沉积物中不存在,但长江、淮河、松花江、海河均可能存在一定的潜在风险,负面生物毒性效应会偶尔发生,风险主要来源于荧蒽和菲。太湖和滇池水体中存在的潜在多环芳烃风险种类较多,风险主要来源于菲、荧蒽、芘、苯并（a）蒽、苊和蒽,对水生生物毒性效应较高,有必要进行更深入细致的调查研究高风险区域底栖生物的受损状况、污染来源和途径,以制定合理的污染控制对策。     

Levels of polycyclic aromatic hydrocarbons and dibenzothiophenes in wetland sediments and aquatic insects in the oil sands area of Northeastern Alberta, Canada

An immense volume of tailings and tailings water is accumulating in tailings ponds located on mine leases in the oil sands area of Alberta, Canada. Oil sands mining companies have proposed to use tailings- and tailings water-amended lakes and wetlands as part of their mine remediation plans. Polycyclic aromatic hydrocarbons (PAHs) are substances of concern in oil sands tailings and tailings water. In this study, we determined concentrations of PAHs in sediments, insect larvae and adult insects collected in or adjacent to three groups of wetlands: experimental wetlands to which tailings or tailings water had been purposely added, oil sands wetlands that were located on the mine leases but which had not been experimentally manipulated and reference wetlands located near the mine leases. Alkylated PAHs dominated the PAH profile in all types of samples in the three categories of wetlands. Median and maximum PAH concentrations, especially alkylated PAH concentrations, tended to be higher in sediments and insect larvae in experimental wetlands than in the other types of wetlands. Such was not the case for adult insects, which contained higher than expected levels of PAHs in the three types of ponds. Overlap in PAH concentrations in larvae among pond types suggests that any increase in PAH levels resulting from the addition of tailings and tailings water to wetlands would be modest. Biota-sediment accumulation factors were higher for alkylated PAHs than for their parent counterparts and were lower in experimental wetlands than in oil sands and reference wetlands. Research is needed to examine factors that affect the bioavailability of PAHs in oil sands tailings- or tailings water-amended wetlands.     

Quantification and source identification of polycyclic aromatic hydrocarbons in sediment, soil, and water spinach from Hanoi, Vietnam

Polycyclic aromatic hydrocarbons (PAHs) were quantified in sediment, soil, and plant material from Hanoi, Vietnam, and an aquatic production system in peri-urban Hanoi. The sum of the concentration of 16 US-EPA priority PAHs ( summation PAH16) ranged between 0.44 and 6.21 mg kg(-1) dw in sediment and between 0.26 and 1.35 mg kg(-1) dw in soil, with decreasing concentrations from the urban area to the peri-urban area, indicating contributions from urban and industrial sources. Double plots of diagnostic source ratios indicate that PAHs originate from mixed petrogenic and pyrogenic sources, the latter being predominant. The predominance of low molecular weight (LMW) PAHs in the sediment samples suggests that petrogenic sources are more prevalent in the water environment than in the soil. In contrast, high molecular weight (HMW) PAHs dominated in water spinach which probably reflects the plant's uptake of particle-bound PAHs that originate from pyrogenic sources.     

Spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Nansi Lake, China

Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Nansi Lake of China to investigate the spatial and temporal distribution characteristics. The concentrations of 16 kinds priority PAH compounds were determined by GC-MS method. And ²¹⁰Pb isotope dating method was used to determine the chronological age of the sediment as well as the deposition rate. The results indicated that the total PAHs concentration ranges in surface and core sediment samples were 160 ~32,600 and 137 ~ 693 ng/g (dry wt.), respectively. The sediment rate and the average mass sedimentation were calculated to be 0.330 cm·year^???1 and 0.237 g·cm^???2·yr^???1 and the sediment time of the collected core sample ranged from 1899 to 2000. The peak of PAH concentrations came at recent years. The source analysis showed PAHs mainly came from the contamination of low temperature pyrogenic processes, such as coal combustion. The PAHs concentrations were lower than ERL and LEL values for most collected samples. However, in several surface sediment samples especially in estuary sites, the PAHs concentrations were not only higher than ERL and LEL values, but also higher than ERM values.     

Polycyclic aromatic hydrocarbons in surface water and bed sediments of the Hungarian upper section of the Danube River

This study was performed to elucidate the distribution, concentration trend and possible source of polycyclic aromatic hydrocarbons (PAHs) in surface water and bed sediments of the Hungarian upper section of the Danube River and the Moson Danube branch. A total of 217 samples (water and sediments) were collected from four different sampling sites in the period of 2001–2010 and analysed for the 16 priority US Environmental Protection Agency PAHs. Concentrations of total 16 PAHs (∑PAHs) in water samples ranged from 25 to 1,208 ng/L, which were predominated by two- and three-ring PAHs. The ∑PAH concentrations in sediments ranged from 8.3 to 1,202.5 ng/g dry weight. Four-ring PAHs including fluoranthene and pyrene were the dominant species in sediment samples. A selected number of concentration ratios of specific PAH compounds were calculated to evaluate the possible sources of PAH contamination. The ratios reflected a pattern of pyrogenic input as a major source of PAHs. The levels of PAHs determined were compared with other sections of the Danube and other regions of the world.     

Long-term fate of polycyclic aromatic hydrocarbons (PAH) in sediments from Loch Leven after closure of an aluminium smelter

An aluminium smelter discharged polycyclic aromatic hydrocarbons (PAHs) into Loch Leven on the west of Scotland from 1907 until it closed in 2000, resulting in elevated PAH concentrations in the sediment. A temporal monitoring programme to investigate any recovery in sediment concentrations began in 2004, with sampling each year until 2008 and again in 2010. Cores were also collected to investigate temporal trends over a longer time scale and to estimate the sedimentation rate in the loch. The loch is divided into two basins, and PAH concentrations were significantly higher in the upper basin, closer to the smelter, than in the lower basin. The PAH distribution and concentration ratios were consistent with a pyrolytic source of PAHs, with a high proportion of heavier parent PAHs. There was no evidence of any recovery in PAH concentrations, perhaps due to the mixing and disturbances of the sediment, and the persistence of PAHs. Concentrations of all PAHs were above the Background Assessment Concentrations (BACs) in both basins. In the lower basin only the 5- and 6-ring PAHs were above the Effects Range Low (ERL) values, but in the upper basin all but naphthalene were above the ERLs. There is therefore still an unacceptable risk of chronic effects in marine species. Concentrations decreased down the cores, falling below BACs in the deepest sections. However, ERLs were exceeded as far down the core as 30 cm for some PAHs.     

Bioaccumulation of PAHs in the Zebra Mussel at Times Beach, Buffalo, New York

The zebra mussel, Dreissena polymorpha, was utilized in an in situ study in the Times Beach Confined Disposal Facility (CDF) located in Buffalo, New York, Mussels, placed both in the water column (upper position) and at the sediment surface (lower position), survived a 34-day exposure to the CDF. At the CDF, total polycyclic aromatic hydrocarbon (PAH) concentrations in the water column were below detection limits (<0.010 mg 1-1), mean total PAH concentrations in the sediment were 164.41 mg kg-1, and mean total PAH concentrations in mussel tissues after the 34-day exposure were 6.58 mg kg-1. PAH concentrations in mussels exposed for 34 days at the CDP were compared to a baseline PAH concentrations in mussel tissue prior to study initiation (Day 0), and mussel tissue from the reference site (Black Rock Channel Lock). There was a significant increase in total PAHs in mussel tissues over the 34 Day period at the CDF. No significant accumulation occurred at the reference site. PAHs which increased significantly in mussel tissue at the CDF were fluoranthene, pyrene, chrysene, and benzo(a)anthracene. Benzo(a)anthracene concentrations increased significantly in mussels at the upper position overall at Times Beach. Concentrations of Total PAHs, fluoranthene, pyrene, and chrysene were not related to position.     

Distribution and sources of polycyclic aromatic hydrocarbons in Wuhan section of the Yangtze River, China

Polycyclic aromatic hydrocarbons (PAHs) are important organic contaminants with great significance for China, where coal burning is the main source of energy. In this study, concentrations, distribution between different phases, possible sources and eco-toxicological effect of PAHs of the Yangtze River were assessed. PAHs in water, suspended particulate matters (SPM) and sediment samples at seven main river sites, 23 tributary and lake sites of the Yangtze River at the Wuhan section were analyzed. The total concentrations of PAHs in the studied area ranged from 0.242 to 6.235 μg/l in waters and from 31 to 4,812 μg/kg in sediment. The average concentration of PAHs in SPM was 4,677 μg/kg, higher than that in sediment. Benzo(a)pyrene was detected only at two stations, but the concentrations were above drinking water standard. The PAHs level of the Yangtze River was similar to that of some other rivers in China but higher than some rivers in foreign countries. There existed a positive relationship between PAHs concentrations and the TOC contents in sediment. The ratio of specific PAHs indicated that PAHs mainly came from combustion process, such as coal and wood burning. PAHs may cause potential toxic effect but will not cause acute biological effects in sedimentary environment of the Wuhan section of the Yangtze River.     

Sorption and desorption of benzo(a)pyrene in aquatic systems

The sorptive behaviour of polycyclic aromatic hydrocarbons (PAHs) is critical to controlling their transport, fates and effects in the environment. Experiments are described which detail the behaviour of a model compound (benzo(a)pyrene) under simulated aquatic conditions. The kinetics of sorption were comparable to those of other PAH compounds. The sorption equilibrium was extensively studied and found to be affected by several key parameters, notably sediment concentration. The sorption coefficient decreased substantially with the sediment concentration, from 9580 ml g(-1) at a sediment concentration of 0.067 g l(-1) to 1,110 ml g(-1) at a sediment concentration of 9.8 g l(-1). The results are consistent with previous reports and often explained by the presence of colloids. In this paper the dry weight concentration of colloids was determined and used for deriving the true sorption coefficient, which is up to an order of magnitude higher than the observed partition coefficient. The sorption of benzo(a)pyrene was also dependent on some of the particle properties, and the sorption coefficient was found to increase with the organic carbon content and specific surface area of sediment particles. The desorption of benzo(a)pyrene from sediment was shown to be relatively rapid, with implications for the potential remobilisation of benzo(a)pyrene and similar compounds.     

Description and evaluation of a sampling system for monitoring hydrocarbons in sediments

A composite random sampling design was used to estimate the concentrations of hydrocarbons in sediments from two near-shore areas of Scotland (Firth of Clyde and Firth of Forth). The aim of this work was to estimate a mean value for each parameter in these areas, and to determine whether this can be done with more thorough coverage (better representation), better precision and less variance at lower analytical cost through a composite random sampling scheme rather than a simple random sampling scheme, and thereby contribute to the re-design of the UK National Marine Monitoring Programme (NMMP), re-named the UK Clean Seas Environmental Monitoring Programme (CSEMP) in 2006. Samples were collected using a simple random sampling design during 2005. All sediment samples were analysed for their particle size distribution and total organic carbon (TOC). All sediments were analysed for polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. The concentrations of PAHs and n-alkanes in the study areas are described, and sources of PAHs were investigated through the PAH distributions and n-alkane profiles. Individual sediment samples from each area were combined to give a series of composite sub-samples, each comprised of 5 individual sediment samples. These composite samples were re-analysed for the same parameters as the individual samples. Mean total PAH (2- to 6-ring parent and branched) concentrations, based on the individual original sediment samples collected through simple random sampling, were 1858 microg kg(-1) dry weight (SE = 196 microg kg(-1) dry weight, n = 25) and 532.4 microg kg(-1) dry weight (SE = 59 microg kg(-1) dry weight, n = 25) in the Clyde and Forth, respectively. Mean total PAH concentrations of the composite samples were 1745 microg kg(-1) dry weight (SE = 121.0 microg kg(-1) dry weight, n = 5) in the Clyde and 511.6 microg kg(-1) dry weight (SE = 37.4 microg kg(-1) dry weight, n = 5) in the Forth. No significant differences were found between the mean PAH concentrations from the two sampling designs. This study demonstrated that the composite random sampling design gave a mean value with less variance than the simple random sampling design, at significantly reduced analytical effort (and cost).