Al-Rekabi, HN; Al-Timari, AA; Al-Saad, HT; Douabul, AA
Organochlorine pesticides were determined in the Tigris-Euphrates-Shatt al-Arab Delta by high resolution gas chromatography. Mean concentrations of pesticides in the dissolved form were 98 ng/L p,p ' - DDE (2,2-bis(p- chlorophenyl)-1,1-dichloroethylene); 8 ng/L o,p ' - DDD (2 ,2-bis(p- chlorophenyl)-1,1-dichloroethane); 28 ng/L p,p ' - DDD; 16 p,p ' - DDT (2, 2-bis(p-chlorophenyl)-1,1 ,1-trichloroethane); 30 mg/L aldrin; 66 ng/L dieldrin; 57 ng/L cis-chlordane; 15 ng/L trans-chlordane and 10 ng/L heptachlor. Mean particulate concentrations were 76 microgram/kg dry weight for p,p ' - DDE; 67 microgram/kg p,p ' - DDT; 154 microgram/kg endrin; 11 microgram/kg cis-chlordane; and 68 microgram/kg heptachlor. Partitioning of dissolved pesticides was evident along the Shatt al-Arab River, which was reflected by significantly higher levels of particulate species down river. Residues of p,p ' - DDE; p,p ' - DDD; p,p ' - DDT; endrin and dieldrin were confirmed in sediments from this river; however, DDD was confined to the anoxic sub-surface layers only. Absorbing pesticides from both water and suspended particulate matter, Shatt al- Arab mussels had mean residue concentrations of 43 microgram/kg wet weight p,p ' - DDD; 12 microgram/kg aldrin; 24 microgram/kg dieldrin; 6 microgram/kg cis-chlordane and 5 microgram/kg trans-chlordane. The euphrates River was the major source of pesticides in the dissolved form, while the Tigris River contributed pesticides mainly in the particulate form to the Shatt al-Arab River. The sediment of this river was the largest reservoir of organochlorine pesticides, where more than 80% of the studied contaminants reside. (Author 's abstract)