Spatial Distribution of Methane Flux in the North Coast of Java Island Case Study: Jakarta Bay Fadjar Hidajat a,c*, Nining Sari Ningsih b), A. R .Kartadikaria b), Irfan Kampono a), Y.I. Ulumuddin c), Agus Dendi Rochendic), Singgih P.A.W c), M.T.Kaisupy c), Nurjamin c), Muhadjirin c) , Raden Sutiadi c) , Lusyana c)
a) Earth Science Study program of Oceanography, ITB, Jl. Ganesha 10 Bandung 40132, Indonesia
b) Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Jl. Ganesha 10, Bandung 40132, Indonesia
c) Research Center for Oceanography, National Research and Innovation Agency (BRIN), Jl. Pasir Putih 1, Ancol Timur, North Jakarta 14430, Indonesia
*E-mail: fadj003[at]brin.go.id
Abstract
Methane (CH4) is the second most potent greenhouse gas (GHG) in terms of global warming and climate change after carbon dioxide (CO2). Its concentration in coastal areas is strongly influenced by anthropogenic activities, especially from waste products that go directly into the rivers. Jakarta Bay is the outlet of several rivers that flow through populated areas- thus, it is very likely the water carries a form of contaminants including nutrients and organic matter. This zone is vulnerable to hypoxia, low concentation or without oxygen in water, that would cause an increase in the concentration of methane in the coastal sediments of the methanogenesis zone and the process of releasing CH4 into the water column and the atmosphere. The hypoxic condition of the waters is thought to be a potential source of dissolved CH4. According to the concept of the ^CH4 Paradox^ in which previous studies have revealed that CH4 is only found in zones that do not contain oxygen. Since in the aerobic seawater condition oxygen could convert methane (CH4) into carbon dioxide and water (H2O). The methane therefore slowly breaks down during its journey from the seabed up through the seawater. The greater the depth from which the methane rises, the farther it has to travel and the less methane reaches the upper water layers and the atmosphere. However, in recent studies there are reports that CH4 can be produced and emitted from freshwater environments and oxygen-containing marine systems. It is therefore important to understand, and take into account factors related to the source, cycle and distribution of CH4 in environments with high anoxic and oxic variability, such as in the Jakarta Bay area which is interesting to study. In this study, the dissolved CH4 and air-sea water methane flux in the Jakarta Bay are measured to determine the contribution of CH4 to the atmosphere. The aims of this study are: (1) to identify dissolved CH4 concentrations in spatial distribution (2) to understand the sources of CH4 (3) to assess the releasing process of CH4 into the atmosphere. The measurement of dissolved methane utilizes a headspace equilibrium method. Based on dissolved CH4 concentration from each sampling locations, methane flux distribution is mapped for the coastal area of Jakarta. The met-ocean parameters such as salinity, currents, wind direction, pressure, temperature, and other factors which influence the distribution of methane flux were included in the analysis. This work still in progress and the abstract is hypothetical result of the research.
Keywords: CH4, Jakarta Bay, Methane flux, Spatial distribution.
Keywords: CH4, Jakarta Bay, Methane flux, Spatial distribution
