Occurrence and possible fate of organochlorine pesticide residues at Manzala Lake in Egypt as a model study.

Persistence of the residue of organochlorine pesticides (OCPs) became a great danger to our environment long ago. In this study, the persistence of OCPs at Manzala Lake in Egypt was determined. Four different sites were investigated: the El-Gamel, El-Kowar, El-Rasoah, and Janb El-Timsah regions. Among these, the El-Kowar region had the highest concentration of total OCPs in the sediment samples when compared to other regions during both 2012 and 2013. In fact, generally, the residues of OCPs in the sediment samples were significantly higher in all tested sites in comparison with other compartments. Conversely, OCP residues were undetectable in water samples at both the El-Gamel region and the El-Rasoah site in the studied seasons. The data proved that the sediment layer plays a sourcing role in OCP persistence in the aquatic ecosystem. Data analysis also indicated that there was an external source for OCP contamination in the Manzala Lake ecosystem that most likely comes from Nile Basin countries and which extends the expected half-life of these compounds. It could be exemplified by DDT, the half-life of which increased from 30 to approximately 47 years.