Determination of the level of contamination in Khuzestan coastal waters (Northern Persian Gulf) by using an ecological risk index

The aims of the present study were to investigate the metal contents of sediments of several creeks that discharged into coastal waters using the Risk index. This study was carried out in eight creeks in Mahshahr coastal waters in the Northwest of Persian Gulf from October 2005 to November 2006. Superficial sediments were collected seasonally by Peterson grab, and the concentrations of heavy metals were measured by using a voltammetric polarographic method. The range and the mean concentrations obtained in ppm were 15.03–35.16 (27.01) for Cu, 65.57–171.41 (102.67) for Ni, 4.63–20.06 (13.22) for Co, 0.093–0.78 (0.22) for Hg, 65.07–379 (113.70) for Zn, 0.27–1.00 (0.56) for Cd and 7.09–29.72 (14.66) for Pb. To evaluate the levels of sediment contamination, the background values of the different heavy metals were calculated, and the contamination factor for each metal and the degree of contamination for each creek were determined as well. The results show that some elements such as Hg, Zn, and Ni are at risk level, and all of the studied creeks are classified as undergoing a moderate degree of pollution except for Ghannam that showed a considerable degree of contamination. According to the Risk index values, based on sedimentological toxic factors (S_t) of each metal and the BIO Production Index (BPI) in the studied area, the creeks were classified as considerable and with a very high level of ecological risk.