Assem O. Barakat

Distribution and characteristics of PAHs in sediments from the Mediterranean coastal environment of Egypt

To assess the contamination of polycyclic aromatic hydrocarbons (PAHs) in the Mediterranean coastal environment of Egypt, 26 sediment samples from the coastline, harbours, estuaries and coastal lakes were collected and analyzed. The sediment PAH concentrations of thirty-nine 2-6 ring PAHs ranged from 13.5 to 22,600 ng/g. PAH profiles varied according to the nature of the site and its proximity to sources. Industrialized and urbanized region showed high level of PAHs contamination. In general, the contamination levels of PAHs were similar to those observed in contaminated and slightly contaminated sediments of the Mediterranean Sea. Molecular indices based on ratios of selected PAH concentrations were used to differentiate PAHs from pyrogenic and petrogenic and mixed origins. Good correlations were observed between the petrogenic index, MP/P, A-PAHs/P-PAHs and HMW/LMW. Finally, PAH levels in sediments were compared with Sediments Quality Guidelines (ERM-ERL) for evaluation of probable toxic effects on organism.

Assessment of persistent toxic substances in the environment of Egypt

The objective of this review is to provide a comprehensive assessment of the threats posed by persistent toxic substances (PTS) to the environment and human health in Egypt and to identify priorities, data gaps and recommendations for future intervention to control, reduce or eliminate releases of PTS. Data on available concentrations of persistent toxic substances in the different environmental compartments and their impacts on the ecosystem, and humans have been assembled and summarized. Despite extensive studies, most of the data available deal with limited studies or hot spot situations. Localized inputs of PTS have been identified from freshwater discharges in coastal areas (e.g., Nile estuaries and coastal lakes) and near sewage outfalls from highly industrialized and populated cities. Data are often missing for certain contaminants and in some compartments and geographical areas. The lack of standardized methodologies makes it difficult to compare and use existing data to provide exact conclusions on spatial and temporal trends. In spite of these restrictions, available data indicate that it is unlikely that present levels of cyclodiene pesticides would adversely affect marine organisms. Compounds which are proven to be of concern are DDT, PCBs, gamma-HCH, PAHs, HCB and organotin compounds. Other compounds are suspected to be ubiquitous but data are lacking. Based on few recent data, the reported levels of organochlorine pesticides in fish and human milk samples suggest a concentration decline during the 1990s consistent with the regulatory restrictions on the use of these compounds. It is essential to activate monitoring programs to fill data gaps in appropriate abiotic and biotic. Monitoring programs should be follow standard procedures and include improved QA/QC protocols.

Chemical characterization of naturally weathered oil residues in arid terrestrial environment in Al-Alamein, Egypt.

The main objective of this study was to investigate compositional changes in a range of source- and weathering-dependent molecular parameters in oil residues in the arid terrestrial environment of Al-Alamein, Egypt. The results of aromatic hydrocarbon analysis demonstrated the stability of several aromatic hydrocarbon ratios in oil residues over a wide range of weathering and hydrocarbon concentrations. The ratios of C2-dibenzothiophenes/C2-phenanthrenes (C2-DBTs/C2-PHENs), C3-dibenzothiophenes/C3-phenanthrenes (C3-DBTs/C3-PHENs), C2-chrysenes/C1-chrysenes (C2-CHRYs/C1-CHRYs), and C2-dibenzothiophenes/C1-dibenzothiophenes (C2-DBTs/C1-DBTs) were nearly constant in oil residues of varying degrees of weathering. Biomarker ratios of hopanes and steranes were useful for source identification even for severely weathered oil residues. The data confirmed previous observations that C29 20S/(20S + 20R) and C29 betabeta/(betabeta+ alphaalpha) sterane epimer ratios, and C29/C30, C30 alphabeta(alphabeta + 3alpha), C31 22S/(22S + 22R) hopane ratios correlate well even after extensive weathering of spilled oils, although some exceptions were encountered for an extensively weathered surface sample. The data provided clear evidence of correlation between samples of the weathered oil residues and the possible source oil. Moreover, the results of biomarker compositions were in good agreement with weathering classification based on alkanes and aromatic hydrocarbons. In general, samples with lowest pregnane indices (PI) and tricyclic terpane indices (TriTI) showed the lowest concentrations of n-alkanes and alkylated polycyclic aromatic hydrocarbon (PAH) homologues, the highest weathering ratios (WRs), the highest values of unresolved complex mixture (UCM)/total resolved peak (TRP) ratios, and the highest ratios of C2 and C3-alkylated CHRYs to their counterparts in the PHEN and DBT series.

Application of a Multimolecular Marker Approach to Fingerprint Petroleum Pollution in the Marine Environment

In an attempt to investigate the suitability of a multibiological marker approach for defining the origin of petroleum pollution in marine systems, the aliphatic hydrocarbon compositions of tar ball samples collected from the beaches of a small island impacted by heavy tar loads were determined by gas chromatography and gas chromatography/mass spectrometry. The tar ball samples, as collected, were at low stages of biodegradation and had diverse physical appearance. The majority of the samples (as many as 7 of the 10) appeared to be heavy fuel oils—possibly Bunker C. The GC traces for the other three tar balls, however, indicated that they were crude oils probably from tanker ballast washings or other non-point sources like the oil entering from the adjacent North Mediterranean. The biomarkers of the sterane and hopane series in these samples, however, had remained unaffected by weathering, and their distributions revealed significant differences among the samples suggesting multiple sources of the tar balls. The tar ball samples could be genetically subdivided into four groups on the basis of their biomarker fingerprints. A marine carbonate or evaporite, hypersaline, anoxic depositional environment of the petroleum source rock for Type I residues could be inferred from the even-carbon-number predominance of n-alkanes, the high relative abundance of gammacerane and the predominance of C35 relative to C34 17α(H)-homohopanes. Higher plant contribution and a deltaic environment of source rock deposition could be concluded for Type II residues from the high concentrations of oleanane and diasteranes. On the other hand, Type III residues possessed geochemical characteristics consistent with a normal marine carbonate or evaporite source depositional environment under normal saline, reducing conditions. Finally, type IV residues had biomarker signatures intermediate between Types II and III.

Application of Petroleum Hydrocarbon Chemical Fingerprinting in Oil Spill Investigations––Gulf of Suez, Egypt

Abstract In an attempt to examine the suitability of chemical fingerprinting methods in oil spill investigations, multiple parameters sensitive to both sources and degree of weathering were used to characterize spilled oil samples and to distinguish spilled hydrocarbons from sources unrelated to the spill in shoreline of the Gulf of Suez, Egypt. The characterizations of individual aliphatic and aromatic compounds were based on gas chromatography and gas chromatography/mass spectrometry analyses. The distribution of n-alkanes, polynuclear aromatic hydrocarbons (PAHs) and alkyl PAHs in the source oil and an oil slick collected 72 h after the spill were very similar. Major compositional changes observed in a weathered oiled sediment collected nine months after the spill from the shoreline at the spill location were consistent with previous studies. Molecular parameters of hopane and sterane biomarkers were very similar in the source oil, the spilled oil and the highly weathered oiled sediment. The similarity in biomarker compositions provided a strong evidence for a close genetic association of these samples. Ratios of C2-chrysenes/C2-phenanthrenes and C2-chrysenes/C2-dibenzothiophenes, the pregnane index (sum of the concentrations of C21 and C22 steranes over total concentration of steranes×100), and the tricyclic terpane index (sum of the concentrations of C19 and C30 tricyclic terpanes over total concentration of terpanes×100) clearly differentiated the refined oil products from crude oils. The composition of bilge oil indicated enrichment of late eluting steranes and terpanes and showed biomarker distributions similar to natural petroleum. The results further support that sterane and terpane biomarker analyses could differentiate oil samples of different sources even though they were sometimes indistinguishable in PAH and alkane compositions.

Source-dependent biomarker properties of five crude oils from the Gulf of Suez, Egypt

Abstract Five crude oils from some producing wells in the southern part of the Gulf of Suez were characterized using a variety of organic geochemical parameters. The results reveal significant differences within the oils from the Gulf of Suez basin that suggest two oil types and one mixed type. Type 1 oils from Ras Fanar and East-Zeit fields show a high relative abundance of gammacerane indicating a marine saline-source depositional environment. Another related feature of these oils is the predominance of C 35 over C 34 17α( H )-homohopanes. Type 2 oils from Gama and Amal-9 wells show oleanane indices over 20%, indicating that they originated from an angiosperm-rich, Tertiary source rock. Type 3 oil from Amal-10 well has geochemical characteristics intermediate between those of types 1 and 2. This may reflect mixing of oils from the sources of both types 1 and 2. The geochemical characteristics of the oils vary sufficiently to suggest multiple sources. The type 1 oils possess geochemical characteristics consistent with Upper Cretaceous Brown Limestone or Lower Eocene Thebes Formation carbonate source rocks. Type 2 oils are very similar in geochemical character to the Lower Miocene Rudeis Formation source rocks.

A Comparative Study of Molecular Paleosalinity Indicators: Chromans, Tocopherols and C20 Isoprenoid Thiophenes in Miocene Lake Sediments (Nördlinger Ries, Southern Germany)

Distributions of alkylated chromans and C20 isoprenoid thiophenes were investigated in four organic-matter- and sulfur-rich black shales of Miocene age deposited in the ancient crater lake of the Nördlinger Ries (southern Germany), a meteorite impact crater. Paleosalinity parameters based on these compound classes generally confirm sedimentological evidence of increased salinity over certain periods of the lakes history, but the data from both groups of compounds are not consistent. Diagenetically related molecular constituents were therefore studied to estimate the sensitivity of these parameters. The influence of thiolanes on the isoprenoid thiophene parameter was found to be low, whereas too little is known at present about the origin and diagenetic fate of alkylated chromans to conclude definitely that an alkylated chroman paleosalinity parameter can reliably be applied to a wide range of depositional settings.

Distribution of pentacyclic triterpenoids in Green River oil shale kerogen

Abstract Pentacyclic triterpenoids released from Green River kerogen by a low temperature, mild, stepwise oxidative degradation using sodium dichromate in glacial acetic acid have been investigated by high resolution gas chromatography and computerized gas chromatography-mass spectrometry. Three series of stereoisomeric hopanoic acids (C 30 –C 33 ) were found based on their αβ, ββ, and βα configurations. In addition, the following compounds were tentatively identified: 29,30-bisnorhopanoic acid, 30-norhop-22-one, 22,29,30-trinorhopan-21-one, 3-hopanone, and 3-gammacerone. The distribution of isomeric hopanoic acids supports previous suggestions of an extremely mild thermal history of Green River kerogen. Bonding of these triterpenoids to kerogen is likely to occur through the terminal positions (e.g. positions 3, 21, 22, 30, 31, etc.). The results also provide further evidence in favor of the microbiological origin of at least part of the organic matter in Green River oil shale kerogen.

Assessment of persistent organochlorine pollutants in sediments from Lake Manzala, Egypt

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in surface and core sediment samples collected from Manzala Lake, the largest of the Egyptian coastal lakes. Total concentrations of OCPs and ∑7 PCBs (ICES) in sediments ranged from 0.63 to 31.31 ng/g and 0.26 to 31.27 ng/g, respectively. Geographical distribution indicates that levels of contaminants were significantly higher in areas which are mainly influenced by municipal discharge, indicating significant sources of these compounds in urbanised areas. The composition of DDT and its metabolites suggest old input of DDT. The levels of contaminants in Manzala Lake were similar or lower than those observed in comparable areas worldwide. The profiles of ∑OCPs and ∑PCBs in a core from a site heavily impacted by sewage discharge have highest concentrations in the surface core section indicating recent inputs. Assessment of ecotoxicological risk indicated that sediments in two sites were likely to pose potential biological adverse impact.

Spatial distribution and temporal trends of persistent organochlorine pollutants in sediments from Lake Maryut, Alexandria, Egypt.

Organochlorine compounds (OCs) in surface and core sediments collected from Lake Maryut, Egypt, were examined to elucidate their distribution, ecological risk and historical trend. To our knowledge, this is the first study on residue levels of OCs in sediments from Lake Maryut. Concentrations of PCBs and DDTs were higher than other OCs, ranging from 3.06 to 388 and from 0.07 to 106 ng/g dry wt., respectively. The highest concentrations of OCs were found at stations near the discharge point of sewage and close to industrial areas. The distribution of DDT and its metabolites suggest no recent inputs into the lake environment. Contamination levels of sedimentary PCBs and DDTs, can be categorized moderate to high compared to other urbanized regions worldwide. Temporal trends in OCs levels were influenced by input pathways at two sites. Evaluation of ecotoxicological risks suggests that adverse biological effects are expected mainly in the main basin area.