چكيده انگليسي :
Heavy metal contamination of marine ecosystems is one of the important environmental problems. The Persian Gulf with its unique ecological features, geographical constraints as well as various human activities at sea and its coastal area always is under pressure by various sources of contamination, especially by heavy metals. Most studies related to the monitoring of heavy metals in the Persian Gulf are limited only to surface sediments, while core sediments are recognized as a valuable tool for determining the effect of human and natural activities throughout history. In this study, two sediments cores from near coast areas (20 m depth) were collected at Sirik (45 cm) and Tiab (60 cm) stations of the Hormozgan Province to determine the trends and the source of the heavy metal contamination. Physicochemical parameters such as moisture, dry density, bulk density, organic matter, pH, EC, Eh, and particle size were measured in different layers of both core sediments. The concentration of heavy metals including nickel, copper, zinc, vanadium, arsenic, iron, aluminum, chromium, cobalt, copper, and manganese were measured by inductively coupled plasma–optical emission spectrometry (ICP-OES) for Sirik (23 samples) and Tiab (20 samples). The average concentrations of heavy metals including nickel, lead, zinc, vanadium, arsenic, chromium, cobalt, copper, manganese, iron, and aluminum for the Sirik station were 98.20, 8.46, 51.17, 41.46, 2.60, 73.48, 13.83, 24.85, 469.13, 29945.65, and 19360.78 mg kg-1and for Tiab were 116.08, 7.78, 45.10, 54.48, 3.15, 96.75, 15.45, 27.88, 451.25, 36075, and 28115 mg kg-1, respectively. The results showed that the average concentration of all heavy metals are within standard limits at both stations and indicated no pollution signal; except nickel, which is higher than the limit of Sediment Quality Guidelines of Canada and the US EPA. The results of obtained enrichment factor (EF) and geo-accumulation index (Igeo) values for both stations showed that only nickel, among all heavy metals, has a low degree of contamination. The relative sedimentation rate of the two cores was determined based on the wiggle-matching method, comparison between changes in metal concentration in both core samples, and meteorological and hydrological drought indices (based on Minab Meteorological Station, and Minab River Hydrometric Station). This comparison showed that the severe wet periods have a direct effect on the increase of heavy metal contamination in the Sirik core sediment sample. Determination of the source of heavy metals by principal component analysis (PCA) indicated that the source of most metals is similar and might be a natural source. The natural source was probably related to the upstream erosion because of the direct effect of wet periods in the Sedij basin.
