Indones. J. Chem., 2022, 22 (4), 1070 - 1080 Kumar Krishnan et al. 1070 Distribution of Heavy Metals in Sediments and Soft Tissues of the Cerithidea obtusa from Sepang River, Malaysia Kumar Krishnan 1* , Elias Saion 2 , Chee Kong Yap 3 , Prakash Balu 4 , Wan Hee Cheng 1 , and Mee Yoke Chong 5 1 Faculty of Health and Life Sciences, Inti International University, Persiaran Perdana BBN, Nilai 71800, Negeri Sembilan, Malaysia 2 Department of Physics, Faculty of Science, University Putra Malaysia, Serdang 43400, Selangor, Malaysia 3 Department of Biology, Faculty of Science, University Putra Malaysia, Serdang 43400, Selangor, Malaysia 4 Department of Biotechnology, Vels Institute of Science, Technology and Advanced Studies (VISTAS), PV Vaithiyalingam Rd, Velan Nagar, Krishnapuram, Pallavaram, Chennai, Tamil Nadu 600117, India 5 Matrix Global School, Pt 12652, Sendayan Merchant Square, Persiaran 1 Sendayan Utama, Pusat Dagangan Sendayan, 71950 Bandar Sri Sendayan, Seremban, Negeri Sembilan, Malaysia * Corresponding author: tel: +603-7982000 email: kumar.krishnan@newinti.edu.my Received: February 11, 2022 Accepted: May 11, 2022 DOI: 10.22146/ijc.72991 Abstract: The main purpose of the research was to analyze the distribution of Arsenic (As), Cadmium (Cd), Copper (Cu), Iron (Fe), Nickel (Ni), Cobalt (Co), Mangan (Mn), and Zinc (Zn) in soft tissues, shells, and associated surface sediments of Cerithidea obtusa (C. obtusa) mangrove snails collected from Sungai Besar Sepang. The concentration of iron (Fe) was found to be the highest in relation to other toxic elements in sediments, soft tissues, and shells of C. obtusa. The concentrations of Cu and Zn in soft tissues of C. obtusa were found to exceed the concentrations in sediments, indicating bioaccumulation of these metals. Metal pollution was assessed with the Enrichment Factor (EF), Geoaccumulation Index (I geo ), and Pollution Factor (CF). EF, I geo , and CF were 0.34 to 22.41, -3.37 to 2.65, and 0.14 to 9.42, respectively. The results indicate that sediments in Sungai Besar Sepang are contaminated with As and Zn. According to the bivalve bioaccumulation results, the soft tissues of C. obtusa act as a macro-concentrator for Cu and Zn. As a result, it is suggested that ongoing monitoring of releases of heavy metals from anthropogenic sources and stricter environmental protection measures should be implemented. Keywords: enrichment; bio-accumulation; trace elements; neutron activation analysis ■ INTRODUCTION Mollusks are invertebrates found in oceans, rivers, lakes, or even on land [1]. Mollusks are easily obtained from their habitat due to their wide distribution and abundance [2]. Mollusks have the great advantage of being able to be used as bioindicators based on minerals absorbed from their habitat environment [3]. Since these mollusks are one of the important food sources for various living things of beings, it is important to avoid these mollusks being exposed to harmful toxic compounds [4]. The toxic content of mollusks is elevated because of phytoplankton feeding or sediment filtration [5]. As reported in other studies, mollusks have been shown to store high levels of heavy metals in their tissues and shell and adapt to changing environmental conditions [6-7]. Consequently, these heavy metals are partially or fully used for the growth of shells and soft tissues of mollusks [8]. Recently, the accumulation of heavy metals in the shell and soft tissues of mollusks has received much attention [9]. The number of heavy metals in the shells and soft tissues of mollusks and in sediments can be used to assess the degree of