A case study on small-size microplastics in water and snails in an urban river.

Microplastic pollution has become pervasive in aquatic ecosystems. They readily interact with aquatic biota, potentially subjecting them to ecological and health risks. Urban rivers are also affected by microplastics due to intense anthropogenic activity. Nevertheless, relatively little is known about the physiocochemistry or ecotoxicology of microplastics in urban rivers. The present study used laser direct infrared chemical imaging to investigate microplastic pollution in a highly urbanized river in Beijing, China. Surface water was sampled at five sites along the river in March and July, and the benthic snail Bellamya aeruginosa was also collected at each location in July. Thirteen and fifteen different polymers were detected and identified in the surface water sampled in March and July, respectively. Thirteen different polymers were found and isolated in the snails. Of these, polypropylene, polyamide and polyethylene predominated in the microplastic particles. Moreover, the average abundance of the microplastic was significantly higher in the surface water sampled in July (39.55 ± 4.78 particles L-1) than in March (22.00 ± 4.87 particles L-1) (p < 0.05). The average microplastic abundance of snails across all sites was 28.13 ± 4.18 particles, among which the Q2 site has significantly higher microplastic abundance than station Q3-Q5 (p < 0.05). Microplastic particles 10-100 µm in size predominated in both the surface water and the snails. By contrast, the proportions of microplastic particles 200-500 µm in size were substantially smaller. The measured microplastic pollution load and microplastic pollution risk indices in the surface water indicated that the current microplastic pollution level in the Qing River was moderate from upstream to downstream. Moreover, the potential adverse effects of microplastic particles on snails remain unclear. Further research is required to elucidate small-size microplastics' environmental fate and potential ecological risks in urban rivers.

Standardizing microplastics used for establishing recovery efficiency when assessing microplastics in environmental samples.

Reports of microplastic contamination in the environment are ever-increasing allowing for global assessments of their distribution and abundance. However, differences in sampling and analytical methods used to assess microplastic contamination vary among investigators, resulting in uncertainties when comparing or compiling data. The determination of recovery efficiency is one aspect of the assessment process that can mire comparability among investigations. We evaluated recovery efficiency among studies published in 2020 and found that appreciable variability existed concerning the density and size of the microplastics used in the recovery efficiency determinations. Further, the established recovery efficiency may not be reflective of that obtained with mixtures of microplastics found in environmental samples. Herein, we recommend that microplastic standards at least containing three types of polymer with different densities, three shapes, and a similar size to the detection limit, should be tested simultaneously when conducting analytical methods. The inclusion of such information will aid in the comparison of results among different investigations and will aid in assessing the global distribution of these contaminants.

A proposed nomenclature for microplastic contaminants.

Microplastics are emerging contaminants with a wide environmental distribution and potential to elicit adverse impacts on organisms. Despite this lack of consistency among reports, data obtained from different investigations are often compared, resulting in the potential for misrepresentation of global microplastic contamination. Major interlaboratory variability in quantification of microplastic levels stem from size-related differences in sampling and analysis with different density solutions to separate microplastics. Herein, we propose a nomenclature that provides key information relating to the microplastics abundance in samples. That is, the proposed nomenclature, MPsca, b, informs on mesh or filter size used in sampling, the density of flotation solution used to separate the microplastics, and the detection limit during the analysis progress of microplastics. This proposed nomenclature would facilitate comparisons among studies to avoid over- or under-estimation of global microplastic levels. Moreover, it would also facilitate the interpretation of meta-data in future assessments.