Global Advanced Research Journal of Agricultural Science (ISSN: 2315-5094) Vol. 13(2) pp. 012-021, October, 2025. Available online http://garj.org/garjas/index.htm Copyright © 2025 Global Advanced Research Journals Full Length Research Papers Geo-accumulation Index and Enrichment Factor of Mercury (Hg) and Methyl mercury (MeHg) in Sediments from some Estuaries, Persian Gulf: Pollution Load Index (PLI) Javad Kazemzadeh Khoei Academic Center for Education, Culture and Research, Iran Email: khoei@iidsharif.ac.ir Accepted 6 October, 2025 Environment geochemistry of mercury and methyl mercury in contaminated sediments from five estuaries along the Imam Khomeini port, northwest part of the Persian Gulf, were studied. The samples were divided into particular grain size fractions and then the content of Hg and MeHg was determined. Environmental indicators such as geoaccumulation index (Igeo) and enrichment factor (EF) for Hg and MeHg in all estuaries were analyzed. According to study results, mean concentrations of Hg in all estuaries were 0.74 for Hendijan, 0.54 Ghanam, 0.37 Meleh, 1.35 Musa and 0.65 μg/g for Zangi, respectively. The mean concentrations of MeHg were 0.61 for Hendijan, 0.40 Ghanam, 0.29 Meleh, 1.01 Musa and 0.47 μg/g for Zangi, respectively. Measuring of geoaccumulation Index show that Meleh and Ghanam estuaries are moderately polluted, Zangi estuary is moderately to strongly polluted and Musa and Hendijan estuaries are strongly to extremely polluted. Enrichment Factor (EF) show metals trace and sources in Ghanam and Meleh estuaries is related to crustal materials or area background, but in Hendijan, Musa and Zangi estuaries is related to anthropogenic impact such as petroleum and petrochemical industries. Finally, the metals accumulated in the estuary sediment as a result of changing chemical conditions such as pH, oxygen content, redox potential, organic carbon and carbonate. Keywords: Geoaccumulation Index, Enrichment Factor, Mercury, Methylmercury, Persian Gulf INTRODUCTION Heavy metals introduced in the aquatic ecosystem are mostly concentrated in estuaries areas, near densely populated and industrialized regions (Vicente-Martorell et al. 2009). These particles are often very small, and can therefore stay in solution for a very long time. In the last decade, there has been an increasing ecological and global public health concern associated with environmental pollution by these metals (Hosseini et al. 2013). Also, human exposure has risen dramatically as a result of an exponential increase of their use in several industrial, specific oil and petrochemical industries and agricultural (Hou et al. 2013). Generally, sources of metals in the environment include industrial, agricultural, pharmaceutical, geogenic, domestic effluents, and atmospheric sources (Ip et al. 2004; Hatje et al. 2008). In the aquatic ecosystem, oil and petrochemical industries