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Tracing the journey of microplastics in lake from surface water to accumulation in the sediments
Summary
Researchers conducted a comprehensive seasonal monitoring study of microplastics in an urban lake in Latvia, tracking distribution in surface water, measuring sediment deposition rates over one year, and analyzing dated sediment archives to determine which environmental compartment best represents long-term microplastic pollution trends. The study aimed to identify the most suitable monitoring matrix and establish standardized sampling protocols for freshwater microplastic research.
The monitoring of freshwater microplastics still is underway to establish standardized methods for sampling, sample treatment, and analysis. Here we present a comprehensive study on microplastics in an urban lake from Latvia (North-Eastern Europe). This study covers the seasonal dynamics of pollution in surface water, sediment deposition rates over one year and distribution in dated sediment archives to determine the most representative environmental compartment for microplastic pollution monitoring (Barone et al. manuscript submitted for publication). We used Manta trawling (300 µm) for surface water collecting, sediment coring for sediments, and trapping for assessing microplastic sedimentation rates. Attenuated Total Reflection and micro-Fourier transform infrared spectroscopy methods were used to investigate particles. Sediment core chronology was based on 210Pb. Surface water microplastic concentrations peaked in summer (5.71 particles/m3) and gradually declined towards winter (0.75 particles/m3). Microplastic concentrations were nearly 25 times higher in more recent sediments (year 2013) compared to deeper layers dating back to 1924. A significant amount of microplastics were found in sediments dated before 1950. The deposition rate of microplastics was 9.47 particles/cm2/year or 4.31 µg/cm2/year. The most abundant polymers identified were polyethylene, polystyrene, and polypropylene, with fibres being the dominant shape in surface water and fragments in sediments. These findings establish a baseline for evaluating future changes in contamination levels. We recommend a combined approach of surface water filtering and sediment trapping methods for monitoring microplastics in lakes. This approach offers efficient sampling and processing, utilizing minimal time and financial resources, while providing valuable insights into the temporal occurrence and deposition of microplastics. This study was supported by ESF Project No. 8.2.2.0/20/I/003, European Regional Development Fund, 1.1.1.2 postdoctoral project no. 1.1.1.2/VIAA/2/18/359, EEA and Norway grants 2014-2021 Bilateral Relations Fund (agreement no. FM2022/37), Estonian Research Council grant PRG1993, Centre of Excellence TK215 and the Latvian University grant Y5-AZ03_ZF-N-110. Also see: https://micro2024.sciencesconf.org/555548/document