Urban stormwater microplastic size distribution and impact of subsampling on polymer diversity

Microplastic concentration, characterization, and size distribution in the Delaware Bay estuary

Microplastic (MP) pollution has been widely reported across water matrices including in estuaries, which are important for the understanding of oceanic MPs. Estuaries can greatly alter the fate, transport, size distribution, and abundance of plastic pollution. The aim of this study was to quantify and characterize MP pollution in the Delaware Bay estuary USA, including the size distribution. Samples (N = 31) were collected from the mouth of the Delaware River to the coastal ocean including multiple frontal zones across two sampling campaigns (2019 and 2022). MP were extracted from the collected particles using wet peroxide oxidation and density separation with saturated sodium chloride. Particles collected on 500 μm mesh sieves were analyzed via Fourier transform infrared (FTIR) spectroscopy. Across all samples, 324 of the 1015 particles analyzed were MP, and 11 macroplastics were observed. MP concentrations ranged from below detection to 4.12 MP/m3 (mean 0.34 ± 0.80 MP/m3). No significant differences were observed between sampling sites; nonetheless, the two highest MP concentrations were observed when sampling along frontal zones with visible debris including macroplastics. Polyethylene (53%) and polypropylene (43%) were the most abundant polymers observed. The majority of the non-plastic particles were classified as particulate natural organic matter (82% of non-plastics). Particles from samples collected during 2022 (N = 864) also had color, morphology, and two size dimensions recorded. MP particle size was significantly associated with sampling site, with the coastal ocean sampling site generally having the smallest MPs. A correlation between total post-extraction particles and total plastic particles was observed. Aspect ratios for the plastics ranged from one to 40.7, with larger ratios for fibers, with a mean (±standard deviation) of 3.39 ± 4.72 (unitless). These aspect ratios can be used to select shape factors used to estimate the total volume of MP in the studied size range. Overall, these results can help inform fate, transport, and risk assessments related to estuarine plastic pollution.

Stormwater runoff microplastics: Polymer types, particle size, and factors controlling loading rates

Stormwater runoff is a pathway of entry for microplastics (MPs, plastics <5 mm) into aquatic ecosystems. The objectives of this study were to determine MP size, morphology, chemical composition, and loading across urban storm events. Particles were extracted from stormwater samples collected at outfall locations using wet peroxide oxidation and cellulose digestion followed by analysis via attenuated total reflectance (ATR) FTIR. Concentrations observed were 0.99 ± 1.10 MP/L for 500-1000 μm and 0.41 ± 0.30 MP/L for the 1000-5000 μm size ranges. Seventeen different polymer types were observed. MP particle sizes measured using a FTIR-microscope camera indicated non-target size particles based on sieve-size classification, highlighting a potential source of error in studies reporting concentration by size class. A maximum MP load of 38.3 MP/m2 of upstream catchment was calculated. MP loadings had moderate correlations with both rainfall accumulation and intensity (Kendall τ = 0.54 and 0.42, respectively, both p ≤ 0.005). First flush (i.e. rapid wash-off of pollutants from watershed surfaces during rainfall early stages) was not always observed, and antecedent dry days were not correlated with MP abundance, likely due to the short dry periods between sampling events. Overall, the results presented provide data for risk assessment and mitigation strategies.

Microorganism-mediated biodegradation for effective management and/or removal of micro-plastics from the environment: a comprehensive review

Micro- plastics (MPs) pose significant global threats, requiring an environment-friendly mode of decomposition. Microbial-mediated biodegradation and biodeterioration of micro-plastics (MPs) have been widely known for their cost-effectiveness, and environment-friendly techniques for removing MPs. MPs resistance to various biocidal microbes has also been reported by various studies. The biocidal resistance degree of biodegradability and/or microbiological susceptibility of MPs can be determined by defacement, structural deformation, erosion, degree of plasticizer degradation, metabolization, and/or solubilization of MPs. The degradation of microplastics involves microbial organisms like bacteria, mold, yeast, algae, and associated enzymes. Analytical and microbiological techniques monitor microplastic biodegradation, but no microbial organism can eliminate microplastics. MPs can pose environmental risks to aquatic and human life. Micro-plastic biodegradation involves fragmentation, assimilation, and mineralization, influenced by abiotic and biotic factors. Environmental factors and pre-treatment agents can naturally degrade large polymers or induce bio-fragmentation, which may impact their efficiency. A clear understanding of MPs pollution and the microbial degradation process is crucial for mitigating its effects. The study aimed to identify deteriogenic microorganism species that contribute to the biodegradation of micro-plastics (MPs). This knowledge is crucial for designing novel biodeterioration and biodegradation formulations, both lab-scale and industrial, that exhibit MPs-cidal actions, potentially predicting MPs-free aquatic and atmospheric environments. The study emphasizes the urgent need for global cooperation, research advancements, and public involvement to reduce micro-plastic contamination through policy proposals and improved waste management practices.

A simple microplastic splitter for subsampling expanded polystyrene particles

With the high number of microplastic-like particles captured by net hauls including manta or neuston nets, it is often required to subsample in order to decrease sample volume for microplastic enumeration and analysis. Plankton splitter is commonly used to divide microplastic samples. However, current devices such as Folsom plankton splitter and Motoda box splitter have accuracy issues in separating highly buoyant microplastics, namely expanded polystyrene (EPS) as they tend to adhere to the inner walls. Inspired by an apple cutter, we have developed a simple radial splitter made of stainless steel that efficiently divides EPS microplastic samples into precise aliquots. With this simple device, we uniformly divided EPS microplastic samples from marine environments into eight aliquots with no significant differences. The device is a versatile tool to partition all buoyant microplastics including polypropylene and polyethylene microplastics.•The method developed facilitates the precise division of buoyant microplastics into equal aliquots.•The method is specifically effective in splitting expanded polystyrene particles with high buoyancy.