Composition and distribution of polycyclic aromatic hydrocarbons in the surface sediments from the Susquehanna River

Polycyclic aromatic hydrocarbon (PAH) concentrations in 34 surface sediments along the Susquehanna River were investigated in 2000. The total concentrations of PAHs in the surface sediments of Lake Clarke, Lake Aldred, the upper Conowingo Reservoir, and the lower Conowingo Reservoir were 3.3+/-1.5 microg g-1 (n=9), 1.6+/-1.3 microg g-1 (n=4), 9.8+/-5.5 microg g-1 (n=7), and 4.0+/-1.2 microg g-1 (n=14), respectively. These represent the first comprehensive measurement of PAHs in Susquehanna River surface sediments. Overall, total PAH concentrations were relatively lower in Lake Aldred, which is more shallow and sloped, and significantly higher in the upper Conowingo Reservoir. The sediment PAH levels were related to river flow rates, which are indirectly correlated with the particle size of the surface sediments. Total PAH levels in all the studied sites were below the effects range median (ERM) of 44.8 microg g-1 with 38% (13 of the 34 sampling sites) exceeding the effects range low (ERL) of 4.02 microg g-1. Principal component analysis indicated that variations in the PAH compound patterns of each reservoir decreased from upstream to downstream, indicating that the surface sediments were mixed along the Susquehanna River. The PAH patterns in the lower Conowingo Reservoir sediments were a combination of those upstream sources. Source analysis using isomer ratios as indicators suggested that PAHs in the Susquehanna River surface sediment are derived from the combustion of fossil fuels such as coal and gasoline with coal as the major source of contaminants.     

Heavy metals and polycyclic aromatic hydrocarbons in sediments from the Shenzhen River,South China

With the analysis of eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and sixteen polycyclic aromatic hydrocarbons (PAHs) in sediments from the Shenzhen River, South China, the ecological risks associated were evaluated using Hakanson’s method (for the metals) and the Effect Range Low/Effect Range Median (ERL/ERM) method (for the PAHs). The result shows concentrations of heavy metal in the order Zn?>?Cu?>?Cr?>?Ni?>?Pb?>?As?>?Cd?>?Hg, and among which the Zn, Cu, Ni, and Pb are exceeding the maximum contaminant level for sediments while those of PAHs are far below. The potential ecological risk index value for the heavy metals in the sediment samples was 261.90, which is in the moderate risk category. Total PAH concentrations in the sediments ranged from 1,028 to 1,120 ng/g, which are all far lower than the sediment guideline concentration of 4,022 ng/g, indicating that the risks of biological impacts caused by PAHs in Shenzhen River sediments are, therefore, relatively low. Besides, the fluorene concentration was above the ERL, and would potentially cause negative biological effects in the Shenzhen River. Heavy metals risks are suggested among the most important concerns that the environmental recover measures pay attention to.     

Temperature-dependent sorption of polycyclic aromatic hydrocarbons on natural and treated sediments

In aqueous environment temperature is considered to play a significant role in the sorption process of polycyclic aromatic hydrocarbons (PAHs) and its influence on the sorption equilibrium is indicative of sorption energies and mechanisms. In this study, sorptions of five PAHs on three heterogeneous sorbents including one river sediment (YHR), one estuary sediment (YRD) and one treated sediment with organic matter removed (IM) were carried out at a range of temperature from 5 °C to 35 °C. Stronger sorptions were observed at lower temperatures, with the equilibrium sorption coefficient K_d increasing 2-5 times as the temperature decreases 30 °C. The increase of K_d value was attributed primarily to the change of PAH water solubility, which predicted 40-75% of the increase of K_d in the sorption process. To provide insight into the sorption mechanism, enthalpy change (ΔH_S) for the sorption process was calculated and the values were observed to be negative for all of the interactions, suggesting that the exothermal sorption of PAHs inversely dependents on temperature. Based on the values of ΔH_S, van der Waals forces were inferred as the main sorption mechanism for the PAHs, especially on the YHR sediment which contained more organic matter. For sorption of larger size PAHs on the sorbents with low organic matter, specific interactions were deduced to contribute to the overall sorption.     

Distribution of polycyclic aromatic hydrocarbons in the sediments of the Adriatic Sea

Distribution of the sixteen polycyclic aromatic hydrocarbons (PAHs) indicated from USEPA as priority pollutants was studied in surface sediments of two coastal areas of the Adriatic Sea. PAHs were recovered from the sediments by solvent extraction and then analyzed by means of gas chromatography-mass spectrometry. Total concentrations of the analytes in the range 24.1-501.1 ng/g were detected. The observed distribution has been discussed taking into account different aspects, such as the fluvial inputs and the grain size of the sediments. By using a molecular marker approach and characteristic compositional patterns it was possible to ascribe to combustion processes the main source of PAHs. Furthermore a good correlation between benzo[a]pyrene and the total concentration of PAHs (r=0.953) has been pointed out.     

Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China

Spatial distribution of chlorinated hydrocarbons [chlorinated pesticides (CPs) and polychlorinated biphenyls (PCBs)] and polycyclic aromatic hydrocarbons (PAHs) was measured in riverine and estuarine sediment samples from Pearl River Delta, China, collected in 1997. Concentrations of CPs of the riverine sediment samples range from 12 to 158 ng/g, dry weight, while those of PCBs range from 11 to 486 ng/g. The CPs concentrations of the estuarine sediment samples are in the range 6-1658 ng/g, while concentrations of PCBs are in the range 10-339 ng/g. Total PAH concentration ranges from 1168 to 21,329 ng/g in the riverine sediment samples, whereas the PAH concentration ranges from 323 to 14,812 ng/g in the sediment samples of the Estuary. Sediment samples of the Zhujiang River and Macao harbor around the Estuary show the highest concentrations of CPs, PCBs, and PAHs. Possible factors affecting the distribution patterns are also discussed based on the usage history of the chemicals, hydrologic condition, and land erosion due to urbanization processes. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived PAHs of the sediment samples of the Pearl River Delta. In addition, the concentrations of a number of organic compounds of the Pearl River Delta samples indicate that sediments of the Zhujiang river and Macao harbor are most likely to pose biological impairment.     

Contamination of polycyclic aromatic hydrocarbons in surface sediments of mangrove swamps

The concentrations of total polycyclic aromatic hydrocarbons (sigmaPAHs) and 15 individual PAH compounds in 20 surface sediments collected from four mangrove swamps in Hong Kong were analysed. sigmaPAH concentrations ranged from 356 to 11,098 ng g(-1) dry weight with mean and median values of 1992 and 1,142 ng g(-1), respectively. These values were significantly higher than those of marine bottom sediments of Hong Kong harbours, suggesting that more PAHs were accumulated in mangrove surface sediments. The concentrations of sigmaPAHs as well as individual PAH compound varied significantly among mangrove swamps. The swamps heavily polluted by livestock and industrial sewage, such as Ho Chung and Mai Po, had much higher concentrations of total PAHs and individual PAH than the other swamps. The PAH profiles were similar among four mangrove swamps, and were dominated by naphthalene (two-ring PAH), fluorene and phenanthrene (three-ring PAH). The mangrove sediments had higher percentages of low-molecular-weight PAHs. These indicated that PAHs in mangrove sediments might originate from oil or sewage contamination (petrogenic input). Ratio values of specific PAH compounds such as phenanthrene/anthracene and fluoranthene/ pyrene, were calculated to evaluate the possible source of PAH contamination in mangrove sediments. These ratios varied among samples, suggesting that mangrove sediments might have a mixed pattern of pyrolytic and petrogenic inputs of PAHs. Sediments collected from Ho Chung mangrove swamp appeared to be more dominated by pyrolytic input while those from Tolo showed strong petrogenic contamination.     

Sorption-desorption behavior of polycyclic aromatic hydrocarbons in upstream and downstream river sediments

Sorption and desorption behaviors of phenanthrene and naphthalene were studied with the whole sediment, humic acid (HA) and humin samples from downstream and upstream sites along the Kishon River, Israel. The 13C nuclear magnetic resonance spectra and the sorption coefficients suggest that sorption occurs to both aromatic and aliphatic moieties of the sedimentary organic matter and that rigid paraffinic domains probably contribute to the sorption non-linearity. The carbon-normalized Freundlich affinity values for the two sorbates were significantly higher for the whole sediment and humin samples from the downstream region of the river than for the upstream sediment samples. On the basis of the measured affinity values, the sorbents can be arranged in the following order: humin>HA>whole sediment. Phenanthrene exhibited the lowest desorption from the whole sediment samples compared with the other sorbents. For naphthalene, the desorption hysteresis obtained with the whole sediment and humin samples were similar: both exhibited a decrease in desorption with decreasing solute concentration. The higher sorption affinities observed for all the organic fractions from the downstream sediment are suggested to be related to the low levels of polar domains and humin content. It is concluded that in bulk sediment samples, the overall contribution of the HA fraction to short-term sorption is of high importance, but the sorption non-linearity is controlled mainly by the humin complexes. The low desorption potential recorded for the whole sediment samples could affect the natural attenuation of the sorbed hydrophobic organic compounds.     

Enrichment of polycyclic aromatic hydrocarbons (PAHs) in mariculture sediments of Hong Kong

Surface and core sediments collected from six fish farms in Hong Kong and from reference sites were investigated for the enrichment and sources of polycyclic aromatic hydrocarbons (PAHs). Moderately high ∑PAH₁₆ levels (123-947 ng g⁻¹, mean: 450 ng g⁻¹) were found in the surface aquaculture sediments. In comparison with the sediments from the reference sites, the average enrichment percentage of total organic carbon (TOC) and PAHs in surface sediments were 21.4 and 43.8%, respectively, and in the core sediments, 24.6 and 73.7%, respectively. Mathematical source apportionment analyses (i.e. isomer ratios, hierarchical cluster analysis, principal components analysis with multiple linear regression analysis) suggested a higher percentage of petrogenic sources in aquaculture sediments. The fish feeds might be the main source of the enriched PAHs in the aquaculture sediments. To our knowledge, this is the first study showing that PAHs in aquaculture sediments could be attributed to human aquaculture activities.     

Characterization of extractable and non-extractable polycyclic aromatic hydrocarbons in soils and sediments from the Pearl River Delta, China

Formation of bound residues of pollutants in soils and sediments is an important process to control the fate of pollutants in the environment. The most of bound residue is not solvent extractable. In this paper, we measured both extractable and non-extractable polycyclic aromatic hydrocarbons (PAHs) in different organic matter fractions of samples from the Pearl River Delta, China. Non-extractable PAHs concentration was 234.45-1424.57 μg/kg and accounted for 33.78-57.44% of total PAHs. 2-3 Ring PAHs were the dominant species and differed in concentration substantially between the samples. The atomic ratio of PAHs over organic-C in the fractions ordered as solvent soluble organic matter > humin > humic acids, matching the content of aliphatic moieties in the fractions of organic matter. The ratio of extractable and non-extractable PAHs may relate to the aging process of PAHs in soil and sediment.     

Distribution of polycyclic aromatic hydrocarbons (PAHs) and tributyltin (TBT) in Barcelona harbour sediments and their impact on benthic communities

Sediments have long been recognised as a sink for many contaminants like polycyclic aromatic hydrocarbons (PAHs) and tributyltin (TBT), which by virtue of their nature can strongly adsorb onto sediments affecting the benthic community inhabiting them. Using geographical information systems, this study reports and combines the results of several already existing studies along Barcelona harbour in order to assess the potential ecological impacts of these contaminants on the benthos of the harbour ecosystem. Chemical analysis indicated low to moderate contents of PAHs and high contents of TBT in sediments in Barcelona harbour. Comparison against existing sediment quality guidelines (SQGs) indicated that acutely toxic effects would not be expected for PAHs but for TBT, which represents a serious environmental threat for the benthic community. Benthos surveys revealed a deterioration of the benthic community throughout the harbour, especially in the inner port.     

Remobilization of polycyclic aromatic hydrocarbons during the resuspension of Yangtze River sediments using a particle entrainment simulator

Remobilization of 16 polycyclic aromatic hydrocarbons (PAHs) during sediment resuspension was investigated using a particle entrainment simulator at shear stress from 0.2 to 0.5Nm(-2), typical of the energy levels present in many tidally driven aquatic environments. The results suggested that desorption from the entrained particles was the primary source of dissolved PAHs. summation operatorPAHs concentrations in particles on volume normalization increased about four times. However, on mass weight basis, summation operatorPAHs concentrations decreased from 6039.74+/-138.28microgkg(-1) to 1665.39+/-112.26microgkg(-1). The same trend was observed for individual PAHs. Dissolved concentrations of PAHs demonstrated significant differences depending on molecular weight and applied shear. The distribution of PAHs between particle and water phase suggested that for three-ring PAHs, the amounts of PAHs in particles were higher than the predicted values during our experiments. This might be due to presence of another active sorbent.     

Analysis of ozone in the San Joaquin Valley of California

The dynamics of ozone in the San Joaquin Valley of central California are studied by systematic diagnostic runs of the three-dimensional SARMAP Air Quality Model. Air quality in the San Joaquin Valley is the result of a complex combination of local and transported emissions. Simulations show that relatively brisk winds at points of inflow to the Valley produce a strong dependence of ozone in the Valley on upwind conditions. Furthermore, NO_x influx from boundaries and local emissions has significantly greater impact on ozone production than ROG influx and emissions.     

Understanding particulate matter formation in the California San Joaquin Valley: conceptual model and data needs

Quantitative information from the 1995 Integrated Monitoring Study (IMS95) is used to develop a conceptual model, which describes the chemical characteristics and the physical processes responsible for the accumulation of PM in the San Joaquin Valley of California. One significant finding of the conceptual model is the sensitivity of ammonium nitrate (46% of winter PM_2.5) and nitric acid to oxidants, which may be VOC-sensitive rather than NO_x-sensitive. Key gaps in current knowledge are identified using the conceptual model, e.g., the relative sensitivity of winter oxidants to VOC and NO_x, mechanistic details of secondary organic aerosol formation, mechanisms of dispersion under calm conditions, and the importance of dry deposition. Some recommendations are also provided for the formulation of air quality models suitable to address the accumulation of PM in the San Joaquin Valley.     

Determination of some aliphatic and polycyclic aromatic hydrocarbons in marine sediments of the Baltic Sea

Two representative samples of surficial marine sediments have been studied, one from the northern Baltic Proper and the other from the Gulf of Finland. Aliphatic hydrocarbons were determined by gas chromatography on a fused silica capillary column, and six polyaromatic hydrocarbons were determined by gas chromatography-mass fragmentography. Hydrocarbons were extracted with a benzene-methanol mixture and ultrasonic agitation. The aliphatic hydrocarbons were tentatively identified by their retention times. The polyaromatic hydrocarbons (PAHs) were identified on the basis of their retention times and mass fragmentograms by direct comparison with those of standard compounds. The aliphatic hydrocarbon contents ranged from 0,1 to 2,6 μg/g dry matter. In both samples there was a clear maximum at n-C₁₇ and also a clear odd-carbon predominance. The PAH contents ranged from 4 to 120 ng/g dry matter. The PAH concentration was about 58 per cent higher in the sample from the Gulf of Finland than in the sample from the Baltic Proper.     

Petroleum hydrocarbons and polycyclic aromatic hydrocarbons in the surficial sediments of Xiamen Harbour and Yuan Dan Lake, China

Surficial sediments were sampled from nine stations in Xiamen Harbour and two stations in Yuan Dan Lake during April 2002. Sediment samples were extracted by organic solvents, separated by silica gel column chromatography and analyzed by gas chromatography-mass selective detector (GC-MSD). Selected ion monitoring was at M/Z=57 for petroleum hydrocarbons (PHCs) and individual M/Zs for each of the 15 typical polycyclic aromatic hydrocarbons (PAHs) and nine alkylated PAHs. The results showed that concentrations of PHCs and total PAHs in the sediments of Yuan Dan Lake were 1397 microg g(-1) (dry weight, dw) and 1377 ng g(-1) (dw), respectively. The ranges for PHCs and total PAHs in the sediments from Xiamen Harbour were 133-943 microg g(-1) (dw) and 98-309 ng g(-1) (dw), respectively. Shipping activities, industrial wastewater discharges, fuel oil spillage from ships and vehicles were the main sources of PHCs and PAHs in the Harbour. In addition, the widespread use of coal for industrial processes and domestic consumption accounted for the second largest source of PAHs in the sediments, while atmospheric transport and deposition of PAHs are also important.     

Supercritical fluid extraction of polycyclic aromatic hydrocarbons from marine sediments and soil samples

Supercritical fluid extraction (SFE) was used to extract polycyclic aromatic hydrocarbons (PAH) from a certified sample of marine sediment. This sample contains a great number of organic pollutants that are present in low concentrations. The extractions were carried out at 50 and 80 degrees C, at a pressure varying from 230 to 600 bar and using CO2 in the supercritical phase and the effect of three organic modifiers (methanol, n-hexane and toluene), added at 5%/vol, at the same temperature and pressure conditions, were then considered. PAHs were characterized by GC-MS and the recover yield was estimated for 6 PAHs that were representative of those present in the sample, according to their molecular weight and to the number of condensed rings. The analytical conditions giving the best recovery efficiency were used on an unpolluted soil sample spiked with 11 PAHs of environmental importance at a concentration similar to that certified for the sediment sample. An increase in the yield of recovered PAHs, using methanol as co-solvent, was observed while higher temperatures caused a negative effect on the quantity of recovered pollutants. The recovery yield for PAHs from the spiked soil sample was measured and found to be greater than 90%. Better recoveries were obtained for those compounds with higher molecular weight.     

Potential source apportionment of polycyclic aromatic hydrocarbons in surface sediments from the middle and lower reaches of the Yellow River,China

In this work, principal component analysis/multiple linear regression (PCA/MLR), positive matrix factorization (PMF), and UNMIX model were employed to apportion potential sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from middle and lower reaches of the Yellow River, based on the measured PAHs concentrations in sediments collected from 22 sites in November 2005. The results suggested that pyrogenic sources were major sources of PAHs. Further analysis indicated that source contributions of PAHs compared well among PCA/MLR, PMF, and UNMIX. Vehicles contributed 25.1–36.7 %, coal 34.0–41.6 %, and biomass burning and coke oven 29.2–33.2 % of the total PAHs, respectively. Coal combustion and traffic-related pollution contributed approximately 70 % of anthropogenic PAHs to sediments, which demonstrated that energy consumption was a predominant factor of PAH pollution in middle and lower reaches of the Yellow River. In addition, the distributions of contribution for each identified source category were studied, which showed similar distributed patterns for each source category among the sampling sites.     

Source apportionment of polycyclic aromatic hydrocarbons in surface sediments of the Bohai Sea, China

A total of 112 surface sediment samples covering virtually the entire Bohai Sea were analyzed for polycyclic aromatic hydrocarbons (PAHs), in order to provide the extensive information of recent occurrence levels, distribution, possible sources, and potential biological risk of these compounds in this area. Surface sediment samples were collected from the Bohai Sea using a stainless steel grab sampler. Sixteen PAHs were determined by a Finnigan TRACE DSQ gas chromatography/mass spectrometry. Diagnostic ratios, cluster analysis, and principal component analysis (PCA) with multivariate linear regression (MLR) were performed to identify and quantitatively apportion the major sources of sedimentary PAHs in the Bohai Sea. Concentrations of total PAHs in the Bohai Sea ranged widely from 97.2 to 300.7 ng/g (mean, 175.7?±?37.3 ng/g). High concentrations of PAHs were found in the vicinity of Luan River Estuary-Qinhuangdao Harbor, Cao River Estuary-Bohai Sea Center, and north of the Yellow River Estuary. The three-ring PAHs were most abundant, accounting for about 37?±?5 % of total PAHs. The four-ring and five-ring PAHs were the next dominant ones comprising approximately 29?±?7and 23?±?3 % of total PAHs, respectively. Concentrations of acenaphthylene, acenaphthene, and dibenz[a,h]anthracene are higher than Canadian interim marine sediment quality guideline values at most of the sites in the study area. Contamination levels of PAHs in the Bohai Sea were low in comparison with other coastal sediments in China and developed countries. The distribution pattern of PAHs and source identification implied that PAH contamination in the Bohai Sea mainly originates from petrogenic and pyrogenic sources. Further PCA/MLR analysis suggested that the contributions of spilled oil products (petrogenic), coal combustion, and traffic-related pollution were 39, 38, and 23 %, respectively. Pyrogenic sources (coal combustion and traffic-related pollution) contributed 61 % of anthropogenic PAHs to sediments, which indicates that energy consumption could be a dominant factor in PAH pollution in this area. Acenaphthylene, acenaphthene, and dibenz[a,h]anthracene are the three main species of PAHs with more ecotoxicological concern in the Bohai Sea.     

Polycyclic aromatic hydrocarbons in the surface sediments from Yellow River, China

Fourteen surface sediment samples were collected from Lanzhou Reach of Yellow River, China in July 2005. The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). Total concentrations of the PAHs ranged from 464 to 2621 ng/g dry weight. Sediment samples with the highest PAH concentrations appeared at the downstream of Lanzhou City, where there was the biggest wastewater discharge pipeline from Lanzhou Oil Refinery Factory and Lanzhou Chemical Industry Company. Municipal sewage also contributed to the PAH contamination in the sediments. A correlation existed between the sediment organic carbon content (f(oc)) and the total PAH concentrations (r(2)=0.57), suggesting that sediment organic carbon content played an important role in controlling the PAHs levels in the sediments. According to the observed molecular indices, PAHs contamination in Lanzhou Reach of Yellow River originated both from the high-temperature pyrolytic processes and from the petrogenic source, showing a mixed PAH input pattern, which was also confirmed by the results of a principal component analysis (PCA). According to the numerical effect-based sediment quality guidelines (SQGs) of the United States, the levels of PAHs at most studied sites in Lanzhou Reach of Yellow River should not exert adverse biological effects. Although at some sites (such as S10, S12, etc.) one PAH may exceed the effects range low (ERL), individual PAH did not exceed the effects range median (ERM). The results indicated that sediments in all sites should have potential biological impact, but should have no impairment.