Evaluation of heavy metals concentration in surface sediments of the Mordab river and parts of the Caspian Sea coast in Astara county

Background and Objective: Due to the importance of Mordab river, the concentration and distribution of heavy metals in sediments and part of Caspian sea coast, mostly affected by the Mordab river, were evaluated. Additionally, considering the possibility of heavy metals release from sediments to water column and transfer to crops, the health risk of rice consumption in the region was assessed. Materials and Methods: 21 sediments samples and 4 rice samples from paddy fields along the Mordab River were collected. Heavy metal contents of the samples were measured using ICP-MS. Data analysis was performed using enrichment factor (EF), ecological risk index (RI), health risk index, principal component analysis (PCA) and Mann-Whitney test. Results: The maximum concentrations of elements was higher in coastal sediments than the Mordab River. The results showed low to moderate risk of elements in most stations except for two coastal stations which exhibited considerable risk of contamination with regard to Cr. Principal component analysis categorized the elements into three components of different origin. Moreover, the estimation of weekly intake of elements through rice consumption were less than their permissible concentration set by World Health Organization. Conclusion: The concentration of chromium in sediments, especially coastal sediments, is high, which may be partly due to the concentration of heavy minerals (chromium) in this fraction. Therefore, the origin of elements, particularly chromium, should be determined through sequential extraction methods. On the other hand, despite the pollution of river sediments and high consumption of rice among the residents of the study area, there is no danger to rice consumers in terms of heavy metals.