PAHs in sediment

The sediment material of interest had to show a PAH content sufficient to be determined with an acceptable precision and not reflecting heavy pollution such as harbour dredges. Based on records of the Dutch National Institute for Water Management and Waste Water Treatment (RIZA) on the concentrations of pollutants in the sediments of the big rivers, a sampling location was selected where the sediment was expected to meet the requirements mentioned above. A total of 1500 kg of wet material was taken from a sediment top layer of about 70 cm. 

A pilot study on the heat sterilisation process of the sediment material was performed to evaluate the losses of PAHs. Heating of the sediment at 105°C for 70 h led to losses of up to 60% of some PAHs. From the results it was concluded that the heat treatment has to be carried out at ca. 120°C over a period of 2 h in order to have the least effect on the PAH content. Immediately after sampling, the sediment was air-dried at 40 C over a period of several weeks with continuous churning up and removal of larger objects. The dried sediment was then sieved (pore size 2 mm) and jet-milled for a particle 

The within- and between-bottle homogeneity was verified and the variances were compared with the method variance (assessed on the basis of replicate analyses of an extract). A 500 mg portion of the sediment was extracted in a Soxhlet apparatus with 120 mL of a mixture of n-hexane and acetone 90/10 (v/v) for 6 h. The extract was concentrated and taken into a volume of 1 mL iso-octane. The concentrated extract was eluted over 1.5 g fully activated silica with 15 mL of a 85/15 (v/v) n-pentane/ dichloromethane mixture. A first fraction of 7 mL pure n-pentane was discarded. The eluate was concentrated and taken into a volume of 1 mL of acetonitrile. The concentrate was separated by HPLC with a C-18 column (length 25 cm, internal diameter 4.6 mm, particle size 5 mm), with an acetonitrile/water gradient (45/55 to 100/0 (v/v)) associated to a fluorescence and a diode-array absorption detection. No significant difference in the variance of the between- and the within-bottle series and the analytical method itself Therefore, it was concluded that the material is homogeneous for PAHs. 

The stability was tested over a period of 12 months at -20°C, +20°C and +40°C. All PAH compounds were found to be stable at +20°C. At -)-40°C, instability was noticed after 6 months for almost all PAHs. As a consequence, storage of the sediment over long periods is recommended at -i-4°C. 

The final determination of the PAHs was performed by capillary gas chromatography using flame ionisation or mass selective detection, or by high-performance liquid chromatography using fluorescence or absorption detection. Each participant had validated its method by performing experiments on recovery, extraction efficiency, procedure blanks and detector linearity. 

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Reproductive impairment in fish by anthracene (Hall and Oris 1991) and elevated concentrations of total PAHs in sediments (Johnson et al. 1998)... 

Krahn et al. [479] developed a similar multi-residue scheme for the determination of organochlorines and PAHs in sediments. In this scheme, the preparation is semi-automated with GPC to separate the biogenic material and the sulfur from both the PAHs and organochlorines in the samples. The sterols were separated and purified with an amino-cyano HPLC column prior to derivatiza-tion with bis(trimethylsilyl)trifluoroacetamide (BSTFA). 

Polycyclic aromatic hydrocarbons (PAH) are produced by the combustion, under fuel rich conditions, of almost any fuel. Although a few PAH with vinylic bridges (such as acenaphthylene) are lost, most PAH are quite stable in the atmosphere and eventually accumulate in environmental sinks such as marine sediments. Spatial and historical measurements of PAH in sediments Indicate that these compounds are stable, conservative markers of man s energy producing activities. 

The basis for these arguments is extensive analyses of PAH in sediments which we have carried out over the last several... 

Radiocarbon (14C) dating is the most common application of AMS, and is also relevant for compound specific measurements. PAHs in sediments from an urban reservoir were 14C-free, but most of the PAHs in these sediments were derived from fossil fuel combustion rather than biomass burning.136... 

Fig. 4 Accumulation of PAHs in sediments of Lake Michigan and coal use in Illinois (reprinted with permission from [23])...

Helfrich, J., Armstrong, D., 1986. PAHs in sediments of the southern basin of Lake Michigan. J. Great Lakes Res. 12, 192-199. 

Kayal, S.I., Connell, D.W., 1989. Polycyclic aromatic hydrocarbons (PAH) in sediments of the Brisbane River (Australia) preliminary results. Water Sci. Technol. 21, 161-165. 

The prominence of car soot and crankcase oil PAHs in sediments supports the suggestion that road runoff and runoff via the sewer system, and not atmospheric deposition, is the main pathway for PAH input to the Harbor sediments. This is also reflected by the similarity in the isotopic values of the PAHs in the sewage and sediment samples (Figure 21). Input of road sweep materials to the sediments was also supported by the presence of asphalt-like particulates similar to those observed in the open-road sweeps. Due to the absence of major industries in the St. John s area, sewage is dominated by domestic sources. Sewage PAH content is, therefore, predominantly derived from aerially deposited pyrolysis products, car emissions, crankcase oil by direct... 

Table 2.4.4 Background concentration (BC) and provisional background assessment criteria (BAC) (OSPAR agreement 2005-6) and provisional environmental assessment criteria (EAC) for organochlorines and PAHs in sediment, blue mussel and fish... 

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