Deteksi dan Kuantifikasi Mikroplastik menggunakan Scientific Echosounder

Abstract

Mikroplastik di perairan umumnya diidentifikasi melalui pengambilan sampel dan analisis laboratorium, namun pendekatan ini terbatas secara spasial. Teknologi hidroakustik menawarkan alternatif untuk mendeteksi mikroplastik secara in situ dengan cakupan lebih luas. Penelitian ini bertujuan untuk: (1) menganalisis karakteristik hamburan mikroplastik; (2) menganalisis koefisien hamburan balik volume (sv) sebagai representasi intensitas partikel terkonsentrasi; serta (3) menganalisis kekuatan hamburan balik volume (SV) mikroplastik pada kolom perairan. Eksperimen dilakukan pada kolam uji dengan penuangan 2.500 g mikroplastik per pengulangan (tiga kali), menggunakan distribusi ukuran homogen 1 mm (large MPs) dan 0,5 mm (medium MPs). Data konsentrasi dari analisis laboratorium dikorelasikan dengan data akustik yang diperoleh melalui Simrad EK-15 200 kHz. Hasil menunjukkan nilai nondimensional x ˜ 0,419 (large MPs) dan x ˜ 0,209 (medium MPs), keduanya berada dalam Rayleigh scattering regime dengan hamburan lemah. Nilai rata-rata sv large MPs adalah 9,03×10?5; 5,40×10?5; dan 6,85×10?5 m²/m³ pada kedalaman D1.5, D1, dan D0.5, sedangkan medium MPs masing-masing 1,71×10?4; 5,40×10?5; dan 7,71×10?5 m²/m³. Volume backscattering strength (SV, dB) medium MPs lebih tinggi dibanding large MPs, dengan model regresi yang menunjukkan kecocokan tinggi (R² > 0,80) dan korelasi kuat (r > 0,80). Temuan ini menegaskan bahwa meskipun mikroplastik berada dalam Rayleigh scattering regime, konsentrasi tinggi memungkinkan deteksi praktis. Penelitian ini memvalidasi potensi penggunaan single beam echosounder (SBES) 200 kHz untuk estimasi konsentrasi mikroplastik di kolom perairan.

Microplastic identification in aquatic environments is commonly conducted through water sampling and laboratory analysis, which remain spatially limited. Hydroacoustic technology provides an alternative approach for in situ detection with broader spatial coverage. This study aims to: (1) analyze the scattering characteristics of microplastics; (2) analyze the volume backscattering coefficient (sv) as a representation of concentrated particle intensity; and (3) analyze the volume backscattering strength (SV) of microplastics in the water column. Experiments were conducted in a test tank by introducing 2,500 g of microplastics per trial (three repetitions), assuming a homogeneous size distribution of 1 mm (large MPs) and 0.5 mm (medium MPs). Laboratory-derived concentrations were correlated with acoustic data obtained using a Simrad EK-15 operating at 200 kHz. Results indicated nondimensional values of x ˜ 0.419 for large MPs and x ˜ 0.209 for medium MPs, both within the Rayleigh scattering regime characterized by weak scattering. The mean sv values for large MPs were 9.03×10?5, 5.40×10?5, and 6.85×10?5 m²/m³ at depths D1.5, D1, and D0.5, respectively, while medium MPs yielded 1.71×10?4, 5.40×10?5, and 7.71×10?5 m²/m³. Volume backscattering strength (SV, dB) was consistently higher for medium MPs compared to large MPs, with regression models showing strong fits (R² > 0.80) and strong correlations (r > 0.80). These findings demonstrate that although microplastics in the Rayleigh scattering regime are theoretically difficult to detect, high concentrations enable practical detection. The study validates the methodological and theoretical feasibility of employing a 200 kHz single beam echosounder (SBES) for estimating microplastic concentration in the water column.