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This work examined the polycyclic aromatic hydrocarbons (PAHs) and n-alkanes quantities, sources, and hazards in sediments collected from the Egyptian Western Desert Oases namely: Dakhla, Kharga and Farafra oases. The n-alkane (C9–C20) residue concentrations have ranged from 0.66 to 2417.91 µg/g recorded for the three Oases. On the other hand, the total n-alkane ranged from 448.54 µg/g to 8442.60 µg/g. Higher carbon preference index (CPI) values (> 1.0) proposed that the natural sources could be the main contributor to n-alkanes in the Oases sediment. GC-MS/MS (selected reaction monitoring (SRM) method) was used for the determination of the ΣPAHs concentrations in the studied sediments. The ΣPAHs concentrations (ng/g, dry weight) in the studied three Oases varied from 10.18 to 790.14, 10.55 to 667.72, and from 38.27 to 362.77 for the Kharga, Dakhla and Farafra Oases, respectively. The higher molecular weight PAHs were the most abundant compounds in the collected samples. Assessing potential ecological and human health issues highlighted serious dangers for living things and people. All the investigated PAHs had cancer risk values between 1.43 × 10–4 and 1.64 × 10–1, this finding suggests that PAHs in the samples under study pose a moderate risk of cancer. The main sources of PAHs in this study are biomass, natural gas, and gasoline/diesel burning emissions. [ABSTRACT FROM AUTHOR]

This preliminary investigation aimed to detect concentrations of chlorinated pesticides and PCBs in 40 sediment samples from three desert oases located in Kharga, Dakhla and Farafra in western Egypt. The residues of 18 PCBs and 16 chlorinated pesticides were measured by GC–MS/MS (SRM) method. The results showed that PCBs and pesticides were present in all studied samples. The concentrations of individual PCBs ranged from undetected to 3.99 ng/g dw in all these sediment samples. The total residue of pesticides (ng/g, dry weight) in sediment samples also varied from 5.18 to 25.92, 5.41 to 29.49, and 5.93 to 24.19 ng/g dw for the Kharga, Dakhla and Farafra Oases, respectively. The concentrations of PCBs and chlorinated pesticides detected in these oasis sediments were lower than that reported for other worldwide locations. According to the recorded concentrations in this baseline study of PCBs and total DDTs, the results revealed the minimal risks to organisms and people in the studied area according to the Effects Range-Low (ERL) and Effects Range-Median (ERM) guideline values. • Pesticides and PCBs residues in the Dakhla, Kharga and Farafra Oases sediment. • Pesticides and PCBs concentrations are still lower than in other Egyptian sites. • 18 PCBs and 16 pesticides were measured in sediments by GC–MS/MS (SRM) method. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in eight sampling sites collected from El-Mex Bay sediments during the period of 2013–2015. Concentrations of PCBs, Hexachlorocyclohexanes (HCHs), Dichloro Diphenyl Trichloroethanes (DDTs), and cyclodienes ranged from 0.148 to 23.99, ND to 0.089, ND to 4.64, and 0.005 to 0.581 ng g−1dry wt, respectively. Total organic carbon (TOC) was relatively low, ranging from 0.09% to 1.42%. Total carbonate content ranged from 38% to 58%. The negative correlation of TOC with total pesticides (r  =  −0.18) suggested that TOC does not have a role binding with pesticides. On the other hand, a positive correlation between PCBs and TOC (r  =  0.254 atp > 0.01) was observed probably due to the low solubility of PCBs in the seawater. So, it will continue to precipitate until it reaches the bottom water and contaminates the sediment. The data obtained in the present work compared well with the counterpart data reported internationally. In general, the results of PCBs and OCP concentrations in El-Mex Bay sediments were much lower than the permissible levels recorded by sediment quality guidelines (SQGs). Interestingly, the organochlorines in sediments of El-Mex Bay were below the respective SQG values and were not likely to pose potential biological adverse impact. [ABSTRACT FROM AUTHOR]

The use of two schemes (I and II) was compared for the fractionation of Fe, Mn and Zn in surficial sediments of the coastal regions of Egyptian Red Sea coasts. Scheme I measured the total oxide fraction. Scheme II, a detailed sequential extraction protocol, was used to distinguish oxide forms of the metal (Mn, poor crystalline Fe and crystalline Fe oxides). The data revealed that high percentage of Zn was concentrated in the residual fraction (lithogenic origin) in all sectors of the study. A high percentage of Mn was concentrated in the residual fraction in both of the Gulf of Aqaba and Red Sea proper samples. However, a high percentage of Mn was recorded in the non-residual form; 60.53% (anthropogenic origin) in the Suez Gulf samples. The recovery of Fe was efficient at most stations using Scheme II, and it was shown that most of the Fe was concentrated among residual, poor crystalline Fe oxide and crystalline Fe oxide fractions. Both Schemes I and II are recommended for speciation of Mn and Zn, but Scheme I is preferred since it has fewer analytical steps. However, Scheme 2 is strongly recommended for the determination of the Fe fractionation pattern. Principal component analysis was applied to the multivariate data derived from the geochemical analysis of 24 stations in the study area and the fractionation patterns of Fe, Mn and Zn associated with physico-chemical characteristics of the sediment are discussed. [ABSTRACT FROM AUTHOR]