Macroplastics and Microplastics in the Ecosystems of Rice Fields and Irrigation Ditches in the Malang Region, East Java, Indonesia

This study analyzes the contamination and develops a model of the relationship between macroplastics and microplastics (MPs) in water, sediment, and dominant gastropods found in rice fields and irrigation ecosystems. This study employed an ex post facto method in the rice fields and irrigation ecosystems of Singosari, Kepanjen, Turen, and Dampit districts in Malang Regency. In each district, five rice field ecosystems and five irrigation ecosystems were chosen to monitor the presence of macroplastics (MPs) and the quality of water and sediment, with three repetitions for each ecosystem. Macroplastic sampling was conducted by creating a 1 x 1 m² plot. The findings revealed that Low-Density Polyethylene (LDPE) macroplastic waste was the most prevalent type found across all ecosystems, followed by Polyethylene Terephthalate (PETE). The quantity of macroplastic waste in the rice field ecosystems was significantly lower (7.05-32.03 g.m^-2) compared to the irrigation ditches (65.72-102.80 g.m^-2). Biplot and structural equation model analysis demonstrated a positive correlation between anthropogenic activities and macroplastic density, which in turn was associated with an increase in MPs within the sediment, particularly of the fiber and film types. The presence of MPs in the sediment can significantly accumulate in the digestive tracts of gastropods. The BSCF (Bio-Sediment Concentration Factor) calculation results indicated that the capacity of gastropods to accumulate MPs ranged from 3.8 to 245.8. Based on the BSCF findings, the study highlights the potential of gastropods to serve as bioindicators of MPs and emphasizes the importance of efficient effective solid-waste management by government and local communities.