Dibenzothiophene, sediment

Comprehensive chemical analyses of samples of water, sediment, and biota were carried out both before and after the spill. This cannot of course be carried out in most cases, and illustrates a serious limitation in field studies, in which lack of background data or difficulty in finding an uncontaminated control locality is frequently encountered. Sum parameters were sparingly employed in Baffin Island Oil Spill (BIOS), and emphasis was placed on the analysis of specific compounds attention was directed not only to PAHs, but also to azaarenes, dibenzothiophenes, and hopanes. Thereby, a clear distinction could be made between the input from the oil deliberately discharged, and that arising from natural biological reactions or mediated by atmospheric transport. 

The presence of chlorine and chlorinated compounds is also the source of dioxins and furans during paper making, and these compounds have been detected in sediments in the vicinity of a pulp and paper mill [53] and in effluents, along with polychlorinated dibenzothiophenes [54]. A recent study found high concentrations of PCDD and PCDF along with PCP in nestling tissue (Tachycineta bicolor) collected downstream of paper pulp mills, suggesting that the primary source of contaminants was the use of PCP for timber preservation [55]. In addition, it has been shown that dioxins bioaccumulate in fish downstream of pulp and paper mills [56]. The levels of chlorinated compounds of different families are shown in Fig. 3. 

In one method dichloroethane extraction of the sediment, followed by elimination of elemental sulphur, mercaptans, disulphide and dibenzothiophene on a copper column is followed by a gas chromatographic... 

Boehm and Farrington [18] successfully applied this technique to marine sediments. However, lacking the analytical capabilities to resolve all of these alkylated species, other techniques must be employed. It has been determined that the most environmentally stable alkylated dibenzothiophenes... 

None of the pure cultures that produced HFBT have been shown to further metabolize this compound. Bohonos et al. (46) found two further oxidation products, 3-hydroxybenzothiophene and 2,3-dihydrobenzothiophene-2,3-dione in aerobic mixed cultures co-metabolizing dibenzothiophene. Recently, Mormile and Atlas (61) inoculated portions of the filter-sterilized supernatant from a dibenzothiophene-degrading culture with soil and sediment samples and observed the loss of HFBT using a spectroscopic method. Under their aerobic growth conditions, they also observed the release of carbon dioxide from these cultures indicating that these products of dibenzothiophene degradation can be further oxidized. In addition, they observed carbon dioxide production from dibenzothiophene-sulfoxide. 

Dibenzothiophenes show increasing bioconcentration factors and octa-nol/water partition coefficients with increasing alkyl substitution [38]. It is not known how persistent PCDTs and PCTAs are in the environment. However, alkylated dibenzothiophenes have previously been found to be persistent oil residue compounds in marine organisms and especially in sediments. DBT derivatives, which are abundant in crude oil, represent a group of most persistent oil residues in the marine environment. Alkyl substituents retard microbial degradation. However, some microbes are known which degrade DBT derivatives [7, 39-41]. Oxidation of the derivatives of dibenzothiophene to the respective sulfoxides and sulfones is possible [42]. 

The quantification of dibenzothiophene, phenanthrothiophenes, and benzo b ] n a p htho [2,3-d] thiophene in extracts of a sediment sample is complicated by the presence of higher concentrations of PAHs. This was overcome by reversed-phase LC fractionation, and identification and quantification were based on atmospheric pressure chemical ionization MS, and MS/MS using multiple reaction monitoring (Thomas et al. 1995). 

As common sulphur-containing aromatic compounds, dibenzothiophene and benzo[b]naphtho[2,l-d]thiophenes were determined as illustrated in Fig. 5 C and 5B. Interestingly, the concentration profiles of both contaminants differ significantly. Dibenzothiophene was detected with concentration values between 66 and 2939 ng/g. The first occurrence at a depth of 152 cm can be attributed to a period around 1940. The concentration profile shows relatively consistent values from the bottom to the top of the core with two local maxima at a depth of 142 cm and at a depth range between 62 and 38 cm. In contrast, the concentrations of benzo[b]naphtho[2,l-d]thiophenes are very low in the bottom sediment layers (170 to 135 cm), but increase rapidly towards the depth of 110 cm with values up to approx. 4400 ng/g. This high concentration level persists to a depth of 80 cm followed by a slight decrease towards the top layers with concentrations around 2000 ng/g. Interestingly, also acenaphtylene (Tab. 1) was detected with a similar concentration profile. 

Fig. 5 A-C Depth- and time-correlated concentration profiles of detected PACs benzo[a]pyrene, benz[a]anthracene, benzo[x]fluoranthene (with x=b,k), dibenzothiophene and benzo[b]naphtho[2,l-d]thiophene determined in dated sediments of a Lippe river wetland (Germany).

Claus E, Heininger P, Bade M (1998) Mass spectrometric identification of polychlorinated dibenzothiophens (PCDBTs) in surface sediments of the River Elbe. Fresenius J Anal Chem 361, 54-58. 

Fig. 6. Concentrations per gram dry weight of sediment of (a) total organosulphur compounds, and (b) of dibenzothiophene ( ) and total aliphatic hydrocarbons (o---o) in...

Higher dibenzothiophene/2-methylnaphthalene in the Hassi Messaoud and Zemlet oil samples (DBT/2MeN = 0.07-0.12, Table 3) compared to the Devonian samples (0.02-0.06) suggests that the Silurian source rock was deposited under conditions of lower redox potential (Eh) and contained less iron in clay minerals that could react with sulfides to form pyrite. Excess sulfide in anoxic sediments with little available iron can result in sulfur incorporation into the kerogen, which is then incorporated into the generated oil... 

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