Indones. J. Chem., 2019, 19 (3), 615 - 625 Askal Maimulyanti et al. 615 Effect of Salinity and Oxygen Condition on Phosphate Release from Marine Sediment Measured Using Diffusive Gradient in Thin Film (DGT) Technique Askal Maimulyanti 1,* , Budiawan 1 , Asep Saefumillah 1 , and Heny Suseno 2 1 Department of Chemistry, Universitas Indonesia, Depok 16424, Indonesia 2 Marine Radiology Group, National Nuclear Energy Agency, Jakarta 12070, Indonesia * Corresponding author: tel: +62-81320717396 email: askal_m@yahoo.com Received: May 2, 2018 Accepted: October 19, 2018 DOI: 10.22146/ijc.35233 Abstract: The diffusive gradient in thin film (DGT) is an analytical technique to determine phosphate in the environment. This technique uses a thin film diffusive hydrogel in contact with a binding phase (ferrihydrite) to binding of phosphate. The released phosphate from marine sediment of Jakarta Bay was studied by DGT technique for effect of salinity and oxygen condition. Effect of salinity was observed by NaCl concentration from 0-35 g/L. The maximum phosphate release from sediment was occurred at the concentration of NaCl 30 g/L with incubation for 15 days with phosphate released at 113.99 μg/L, MDGT of 4.7723 μg and CDGT of 17.56 μg/L. The experiment showed the increase of MgCl2 and CaCl2 concentration reduced phosphate release from sediment. The condition of oxygen indicating the release of phosphate under anaerobic conditions is greater than the aerobic condition. The aerobic conditions with incubation for 21 days showed the release of phosphate from sediment to overlying water of 124.72 μg/L, MDGT of 2.4492 μg and CDGT of 6.4380 μg/L. Anaerobic conditions with incubation for 21 days showed phosphate release from sediment to overlying water of 208.62 μg/L, MDGT of 6.1081 μg and CDGT of 16.06 μg/L. The experiment shows that salinity and oxygen concentration influences phosphate release from marine sediment of Jakarta Bay. Keywords: phosphate release; DGT; salinity; oxygen condition ■ INTRODUCTION Phosphorus (P) is one of the most important nutrients for marine eutrophication. The eutrophication in the aquatic ecosystem causes significant changes in biodiversity. The eutrophication causes an increase in plant and animal biomass, the frequency of algal blooms, the growth of rooted plants, and decrease the species diversity [1]. Phosphate is the first cause of eutrophication in an aquatic system. It accumulates in sediments and under some environmental condition can be released into the water [2]. Monitoring phosphate concentration is very important to prevent and control eutrophication. The effect of eutrophication is rooted mainly in ecological impacts as decrease species biodiversity and abundance [3]. Sediment act as a sink where phosphate can be stored, and also as a source of phosphate for the overlying water and play an important role in the overall phosphate metabolism [4]. The release of phosphate from the sediments is an important source for the aquatic environment. Only dissolved phosphate can be released from the sediments to the overlying water. Release phosphate from sediment can be an important source of phosphate for the phytoplankton community in the water. If phosphate concentration is too high, algal growth may become blooming. Phosphate release from sediment is often the significant component of the phosphate budget of an aquatic system. Phosphate release is affected by a multitude of factors, such as pH, redox potential, temperature, hydrological condition and oxygen concentration [5]. There are two main processes responsible for the regulation of phosphate exchange across the sediment- water interface, i.e., sorption reaction between the sediment and porewater, and diffusive and connection movement between the pore water and overlying water