Microplastics contamination in the fishes of selected sites in Pasig River and Marikina River in the Philippines.

Microplastics (MPs), <5 mm in size, are a concerning pollutant in bodies of water because they can be ingested by biological organisms, posing risks to humans and the environment. This study assessed the extent of MPs contamination in various fish species (Oreochromis niloticus, Arius manillensis, and Pterygoplichthys spp.) in selected sites along two major river systems in the Philippines - Pasig and Marikina Rivers. An optimized Raman microspectroscopy technique was used for imaging and identification of MPs using a mean laser spot size of about 1 µm, which is advantageous in the identification of fibers which have small diameters (<50 µm). It also allowed the simultaneous identification of MPs and their pigment additives, which in turn enabled the tracing of possible sources of these MPs. This is important because the fate and accumulation of MPs in rivers systems, as well as its toxicity is dependent on various factors including polymer type and surface chemistry. Majority of the MPs identified from all the fish species were composed of polypropylene and polyethylene in the form of fragments, which reflects both the widespread use of these polymers for packaging and their environmental fate as riverine plastic debris. Moreover, the detection of MPs in the fish species may affect the food chain and eventually pose health risks for humans. The study could provide guidance on waste and environmental water management in the surrounding region.

Fully integrated 3D-printed electrochemical cell with a modified inkjet-printed Ag electrode for voltammetric nitrate analysis.

To address the need for low-cost analytical tools for on-site aquaculture water quality monitoring, miniaturized electrochemical sensor systems can be readily fabricated using additive manufacturing technologies such as 3D printing and inkjet printing. In this work, we report the design and fabrication of an additively manufactured electrochemical platform featuring a reusable 3D-printed electrochemical cell with integrated reference and counter electrodes, and a replaceable inkjet-printed Ag (IJP-Ag) working electrode. The electrochemical cell was 3D-printed with acrylonitrile butadiene styrene (ABS) filament and features a 3D-printed ABS-carbon counter electrode and a Ag|AgCl|gel-KCl reference electrode with a 3D-printed porous junction directly integrated along the sides of the sample compartment. The application of the integrated cell is demonstrated with the analysis of nitrate ions on the IJP-Ag electrode, which was modified with electrodeposited nanostructured Ag to enhance sensitivity to nitrate reduction. Linear sweep voltammetry (LSV) was successfully applied to detect nitrate with a LOD of 1.40 ppm and a sensitivity of 0.2086 µA ppm-1 in a background of artificial brackish aquaculture water (pH 8.0). The sensor response showed intra- and inter-electrode reproducibility and no significant interferences to most of the commonly encountered cations and anions in brackish water. The electrochemical sensor system was also applied to nitrate determination in real aquaculture water samples and demonstrated no significant differences with the results obtained using the standard spectrophotometric method at a 95% confidence level. Our results show how additive manufacturing is a promising approach to readily fabricate fit-for-purpose, low-cost miniaturized electrochemical sensor systems for point-of-use applications.