A new approach to extracting biofilm from environmental plastics using ultrasound-assisted syringe treatment for isotopic analyses

Uncovering the characteristics of plastic-associated biofilm from the inland river system of Mongolia

The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, limited information exists on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms to uncover their characteristics using spectroscopic, isotopic, and thermogravimetric techniques. Mixtures of organic and mineral particles were detected in the extracted biofilms, revealing plastic as a carrier for exogenous substances, including contaminants, in the river ecosystem. Thermogravimetric analysis (TGA) indicated the predominant contribution of minerals primarily comprising aluminosilicate and calcite, representing approximately 80 wt% of the biofilms. Differential thermal analysis (DTA) coupled with Fourier transform infrared (FTIR) spectrometry operated at 25°C-600 °C enabled the detection of gaseous decomposition products, such as CO2, H2O, CO, and functional groups (O-H, C-H, C-O, CO, CC, and C-C), released from biopolymers in the extracted biofilms. Dehydration, dehydroxylation, and decarboxylation reactions explain the thermal properties of biofilms. The stable carbon (δ13C) and nitrogen (δ15N) isotope ratios of the biofilms demonstrated variable signatures ranging from -24.1‰ to -27.0‰ and 3.1‰-12.3‰, respectively. A significant difference in the δ13C value (p < 0.05) among the upstream, middle, and downstream research sites could be characterized by available organic carbon sources in the river environment, depending on the research sites. This study provides insights into the characteristics and environmental behavior of biofilms which are useful to elucidate the impact of plastic-associated biofilms on organic matter and material cycling in aquatic ecosystems.

Tracking the behavior and characteristics of microplastics using a multi-analytical approach: a case study in two contrasting coastal areas of Japan

The global survey for the presence of microplastics (MPs) in aquatic environments has attracted widespread scientific attention over the past decade. However, evaluating the composition and characteristics of these anthropogenic debris using highly sensitive techniques is still under consideration. This study demonstrates a multidimensional analytical approach, including isotopic and thermogravimetric analyses to evaluate characteristics and behavior of MPs in the environment. The MP samples were collected in two contrasting coastal areas of Japan. The stable carbon isotope (δ¹³C) ratios of field-collected polyethylene (PE), polypropylene (PP), and polystyrene (PS) MPs ranged from -25.6‰ to -31.4‰, -23.4‰ to -30.9‰, and -27.3‰ to -28.6‰, respectively. The detected isotope signatures were similar to those of commercial products. In addition, the differences in δ¹³C signature were determined between MPs with different colors. Through thermal analysis, the single-step endothermic process was observed for environmental PE and PS-MPs. Patterns in the thermograms revealed dissimilarities in degradability among the PE-MPs with different colors. The results reveal that degradation (aging) may play a significant role in the behavior and characteristics of MP debris in the aquatic environment. The present study provides fundamental data of environmental MPs from the isotopic and thermogravimetric aspects and highlights the usefulness of the approach for advances in MP research.