Identifying the distribution and source of riverine plastic waste contamination: case study of Brantas River in Malang city

Brantas River experiences significant pollution due to domestic and industrial wastes. This condition also causes natural disasters such as floods. Single use plastics generally made up a large portion of local wastes. However, previous studies mostly investigated plastic waste pollution and local waste management habits as separate topics. Therefore, the objects of this study are the plastic wastes in Brantas River, as microplastic particles, and the identification of its source. The assessments were based on microplastic counts, macroinvertebrate bioassessment with SIGNAL-2 index, and the quantitative data of local domestic waste management at three Stations in Malang City area. Riverine microplastic pollutant concentrations and its sources were both successfully identified and solved. The results showed that the highest riverine microplastic particles were found in Station 3. This station only had four macroinvertebrate taxa with a SIGNAL-2 score of 4.42, indicating severe degradation. Quantitative data showed that 80 % of Station 3 residents threw plastic wastes directly to Brantas River. The low macroinvertebrate counts possibly caused by ingestion of microplastic from households and small-scale enterprises which heavily utilized single use plastics to trade their goods. The first distinctive feature of this study is the comparability of the microplastic, and macroinvertebrate counts with the river degradation status. Secondly, the quantitative data can serve as complementary evidence. Practically, the obtained results can be developed into an integrated plastic waste management plan for the residents surrounding the rivers, particularly in developing countries with similar socio-cultural conditions as elaborated in this study, to maintain the ecosystem quality