Assessment of organochlorine contamination source and ecological risk in the Litani River: polychlorinated biphenyls and organochlorinated pesticides in surface sediments.

In this paper, we investigate for the first time the contamination source and the ecological risk associated to organochlorinated compounds in the Litani system. For this purpose, the levels of 7 polychlorinated biphenyls (PCBs) and 13 organochlorinated pesticides (OCPs) were assessed, using a microwave-assisted extraction coupled to gas chromatography-electron capture detector (MAE/GC-ECD) method, in surficial sediments from 30 sites along the main course of the river, two major tributaries, and the Quaraoun Lake. ∑7PCBs exhibited total concentrations ranging from 0.11 to 8 ng g-1 of dry weight and are not able apparently to pose ecological risks since none of the samples showed concentration above the effects range low (ERL) guideline (22.7 ng g-1). The detected levels of OCPs in the river were significantly higher than those of PCBs; ∑13OCPs range from 0.5 to 46.5 ng g-1 of dry weight. Overall, the integrated eco-toxicological risk imposed by the organochlorine contamination in the Litani River, estimated as the mean effects range medium quotient (mERMq), is considered low with risk probability lower than 21% in all sites. The six dichlorodiphenyltrichloroethane-based pesticides (∑6DDT) contributed to more than 70% of the mERMq in 15 over the 29 included sites. Moreover, the approach of ∑6DDT/∑7PCB ratios was applied to investigate the contamination source. ∑6DDT/∑7PCB was higher than one in all samples suggesting that the organochlorine contamination result from agricultural activities set in the surrounding areas of the Litani River.

Impact of Lebanese practices in industry, agriculture and urbanization on soil toxicity. Evaluation of the Polycyclic Aromatic Hydrocarbons (PAHs) levels in soil.

This study was carried out in order to investigate the toxicity on Lebanese soil and to show the impact of the anthropogenic activities, industrialization and urbanization, on the release of Polycyclic Aromatic Hydrocarbons (PAHs) in Lebanese soils. Hundred soil samples of different land use were screened for 17 PAHs using a UAE/GC-MS method. Detection frequency varied between 76 and 100% for most of the PAHs, where the ΣPAHs ranged from 33.5 to 4062.9 ng g-1. Moreover, BaPeq values varied between 0.93 and 332.4 ng g-1. BaPeq values in industrial and urban soils were 777 and 256 times higher than those in rural soil, respectively. None of the soil samples showed concentrations above the safe BaPeq value of 600 ng g-1. Significant decrease in concentration levels of ΣPAHs was obtained in the following order: Industrial, urban, traffic and agricultural. Furthermore, the relative high contribution of Chrysene, Benzo(a)Anthracene and Benzo(k)Fluoranthene in agricultural soils indicates that open burning remains an adopted way in Lebanon for disposal of agricultural residues, while the predominance of Benzo(ghi)Perylene and Benzo(b)Fluoranthene in industrial soils suggests the broad use of diesel powered engines in the Lebanese industrial sector. The ratios of Low Molecular Weight/High Molecular Weight and fluoranthene/fluoranthene+pyrene (Fln/Fln+Pyr) showed that PAHs in soil samples are mainly pyrogenic and created during combustion of petrol, coal, wood and other biomasses.