In this research, four transects (Astara, Anzali, Sefidrood and Chaboksar) were selected in the southern area of the Caspian Sea, in Gilan province, and in each transect three depths of 5, 10 and 20 meters were selected for investigation and sampling. The concentration of heavy metals in water, surface sediments and edible tissue of two species of fish (Caspian kutum and mullet) and the concentration of 13 polyaromatic petroleum compounds (PAHs) and the residual amount of some pesticides used in the agricultural lands of the region were measured. The results of the measurement of heavy metals in water showed that the concentration of lead and cadmium metals is higher than the RCSM and SEPA standards, the nickel concentration is higher than the WQC, ANZECC standards, and the zinc concentration is higher than the WQC, ANZECC, RCSM and SEPA standards, this can be a warning signal. and be a warning to executive officials.The concentration of heavy metals in surface sediments is lower than the American Sediment Quality Standard (NOAA) and Canadian Sediment Quality Standards (ISQGs). Enrichment index (EF) calculated for all metals was less than 1. The degree of pollution (Cd), the value of the modified degree of pollution (mcd) and the pollution load index (PLI) for heavy metals in sediments are calculated and compared with the quality of the assessment of the level of pollution provided for these indicators in the studied sediments compared to heavy metals without Contamination was detected.The amount of accumulation of zinc and lead metals in the muscle tissue of the studied fish is higher than the USEPA standard and the chromium concentration is higher than the WHO standard. The amount of hazard index (THQ) for all metals was calculated to be less than 1. Therefore, currently, the consumption of the studied fish does not pose a serious threat to the health of consumers.In this study, for the origin of PAHs petroleum compounds in sediments, composite ratios were used, based on which the sediments of the study area had both pyrogenic (fuel) and petrogenic (petroleum) origin.The ecological risk (HQ) calculated for petroleum compounds in water, three petroleum compounds anthracene (Ant), pyrene (pyr) and benzo (b) anthracene (Ben (b) A) was calculated to be greater than 1, therefore it has an ecological impact on the environment The concentration level of Ace petroleum composition compared to ERL, TEL, TEC, ESL standard and the toxicity threshold of PAHs compounds in marine sediments and Flo petroleum composition compared to ERL, TEL and Iranian soil standard and the toxicity threshold of PAHs compounds in marine sediments have been recorded higher.The results showed that the amount of nutrients in the coastal strip of the Caspian Sea has increased compared to the past, which is probably due to fishing activities and the development of aquaculture (cage method) in the southern shores of the Caspian Sea.
Kywords: Heavy metals, Hazard index(THQ), Petroleum compounds (PAHs), Pollution load index (PLI), Nutrients, Caspian Sea
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