Estimating the Trajectory of Macroplastic Particles in Java Sea Using Numerical Modelling Parikesit Nuril Azmi (a*) and Mutiara Rachmat Putri (b)
a)Study Program of Earth Sciences, Faculty of Earth Science and Technology, Institute of Technology Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia
*22424003[at]mahasiswa.itb.ac.id
b)Research Group of Oceanography, Institute of Technology Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia
Abstract
The excessive use of plastic in human activities on land has become a problem of marine litter pollution. This problem attracts many researchers because it not only involves a regional scale but can have an impact on a global scale. Therefore, this study uses a numerical model that aims to describe the hydrodynamic conditions in the Java Sea and simulate the trajectory of macroplastics in the Java Sea originating from DKI Jakarta, Cirebon City, and Surabaya City. The hydrodynamics model simulation uses the Region Ocean Modelling System with resolution of spatial 1/96o or 1.1 kilometres and duration of simulation time is 1 year from 1 January 2019 to 31 December 2019 with a time step of 60 seconds. The hydrodynamics simulation results in the form of average ocean current data per 30 minutes are used as input data to model particle trajectories using Opendrift with the assumption that the particle weight is equal to 1 kilogram of plastic. Furthermore, the trajectory model will be simulated with 2 scenarios, namely stranded and previous. Then, releasing macroplastic particles every month continuously at 3 source points in DKI Jakarta, Cirebon, and Surabaya. The results of the hydrodynamics model show that the ocean currents in the Java Sea are dominated by tidal currents with a magnitude of 0.01 - 1 m/s, the direction of the ocean currents is dominated to the east in one year. In the previous boundary conditions, particle trajectory simulation results show that the missing particles were 51.2% (8,599 kg) and active particles were 48.2% (8,188 kg) with the largest contribution from Jakarta. While the stranded boundary conditions show lost particles of 1.6% (271 kg), active particles 3.35% (562 kg), and trapped particles 95.05% (15,594 kg) with the largest contribution for lost particles is sourced from Cirebon, active particles and trapped sourced from Jakarta. This is due to the dynamics of ocean currents have an important role in the spread of plastic waste in the Java Sea which is dominated by tidal currents and the influence of monsoon winds coupled with the many small islands and the shape of the coastline that curves inward, so that it can trap macroplastic particles in the Java Sea. This result is expected to help government in the National Action Plan for Marine Debris Management through their policies and technologies in order to make a clean and healthy marine environment, so as to improve the economy of the community.
