Microplastics formation based on degradation characteristics of beached plastic bags.

Environmental pollution from plastic bags is a significant issue in the global environment. Plastic bags can be transferred by the wind and ocean currents everywhere in the three dimensions and be fragmented into small particles, termed film-shaped microplastics. The purpose of this study is to provide insights on the degradation of beached plastic bags. Monitoring and sampling were performed to determine plastic bag fragmentation and the possible mechanisms. On selected samples, various spectroscopic techniques and microscopy were used. Before the imposition of the "green" plastic bag fee in Greece, field monitoring suggested that the majority of the coastal plastic bags were fragmented whereas after the "green" fee, less fragmented bags were observed. Evidence of three degradation mechanisms were observed in this study. For oxodegradable plastic bags, degradation takes place for the starch additives and the polymer part stays in the environment as microplastic particles. For thin light density polyethylene plastic bags, mechanical fragmentation takes place in the environment creating microplastics before significant chemical alterations in functional groups were observed and once chemical alteration (oxidation) is observed, fragmentation (of HC or CC bonds) is also taking place. Thus, regulating thin plastic bags usage removes problems related to plastic bags but also to film-shaped microplastics.

Characteristics of microplastics on two beaches affected by different land uses in Salamina Island in Saronikos Gulf, east Mediterranean.

In the present study, samples were taken from two beaches of the Salamina Island. The results of microplastics characterization agree well with the predicted results based on the land uses both locally and from across the mainland. The first beach, Psili Ammos, is affected by increased anthropogenic and industrial activity. Based on the Attenuated Total Reflectance (ATR) - Fourier Transform Infra-Red spectroscopy (FTIR) analysis mainly polyethylene (PE) fragments are observed than in the second beach, Kanakia. A high percentage of plastic pellets from industrial activity among fragments are found as well as the most fresh and the most degraded particles (based on the ester, keto, and vinyl indices). The second beach, Kanakia, has a high percentage of expanded polystyrene (EPS) particles suggesting an impact from fishing activities rather than industrial ones and all PE samples are found to be degraded suggesting that sources of non-fishing microplastic pollution are further away.

Questionnaire-based survey to managers of 101 wastewater treatment plants in Greece confirms their potential as plastic marine litter sources.

Marine pollution by plastics and microplastics (plastic particles 1 nm to 5 mm) is a recognized environmental issue. There are a few studies measuring the concentration of microplastics in the wastewater treatment plants (WWTP) effluent to the sea. Although microplastic concentrations are low in the WWTP effluent, the actual amount of microplastic ending up in the marine environment through WWTPs is quite significant. The present study is an extensive questionnaire-based survey to untrained managers of 101 WWTPs located all over Greece reporting visually-observed plastic items. 94 of the WWTPs have screens with gaps larger than 5 mm. This suggests that microplastics are passing through pretreatment to the main WWTP. In addition, 89 of the WWTP managers observed plastics in different tanks of the WWTPs. Cotton swab sticks are identified as the most common plastic found in WWTPs and the surrounding marine and coastal areas of the effluent pipes.

Oxidation of municipal wastewater by free radicals mechanism. A UV/Vis spectroscopy study.

This study investigates the oxidation of municipal wastewater (WW) by complexation with natural polyphenols having radical scavenging activity, such as (3,4,5 tri-hydroxy-benzoic acid) gallic acid (GA) in alkaline pH (>7), under ambient O2 and temperature. Physicochemical and structural characteristics of GA-WW complex-forming are evaluated by UV/Vis spectroscopy. The comparative analysis among UV/Vis spectra of GA monomer, GA-GA polymer, WW compounds, and GA-WW complex reveals significant differences within 350-450 and 500-900 nm. According to attenuated total reflectance (ATR) spectroscopy and thermogravimetric analysis (TGA), these spectra differences correspond to distinct complexes formed. This study suggests a novel role of natural polyphenols on the degradation and humification of wastes.

The degradation potential of PET bottles in the marine environment: An ATR-FTIR based approach.

The dominance and persistence of plastic debris in the marine environment are well documented. No information exists in respect to their lifespan in the marine environment. Nevertheless, the degradation potential of plastic litter items remains a critical issue for marine litter research. In the present study, polyethylene terephthalate bottles (PETs) collected from the submarine environment were characterized using ATR-FTIR in respect to their degradation potential attributed to environmental conditions. A temporal indication was used as indicative to the years of presence of the PETs in the environment as debris. PETs seem to remain robust for approximately fifteen years. Afterwards, a significant decrease of the native functional groups was recorded; some even disappear; or new-not typical for PETs-are created. At a later stage, using the PET time series collected from the Saronikos Gulf (Aegean Sea-E. Mediterranean), it was possible to date bottles that were collected from the bottom of the Ionian Sea (W. Greece). It is the first time that such a study has been conducted with samples that were actually degraded in the marine environment.

Diffuse pollution by persistent organic pollutants as measured in plastic pellets sampled from various beaches in Greece.

Plastic pellets found stranded on beaches are hydrophobic organic materials and thus, they are a favourable medium for persistent organic pollutants to absorb to. In the present study, plastic pellets are used to determine the diffuse pollution of selected Greek beaches. Samples of pellets were taken from these beaches and were analyzed for PCBs, DDTs, HCHs, and PAHs. The observed differences among pellets from various sampling sites are related to the pollution occurring at each site. Plastic pellets collected in Saronikos Gulf beaches demonstrate much higher pollutant loading than the ones collected in a remote island or close to an agricultural area. Based on data collected in this study and the International Pellet Watch program, pollution in Saronikos Gulf, Greece, is comparable to other heavily industrialized places of the world. The present study demonstrates the potential of pellet watch to be utilized as a detailed-scale monitoring tool within a single country.

Model coupling intraparticle diffusion/sorption, nonlinear sorption, and biodegradation processes.

Diffusion, sorption and biodegradation are key processes impacting the efficiency of natural attenuation. While each process has been studied individually, limited information exists on the kinetic coupling of these processes. In this paper, a model is presented that couples nonlinear and nonequilibrium sorption (intraparticle diffusion) with biodegradation kinetics. Initially, these processes are studied independently (i.e., intraparticle diffusion, nonlinear sorption and biodegradation), with appropriate parameters determined from these independent studies. Then, the coupled processes are studied, with an initial data set used to determine biodegradation constants that were subsequently used to successfully predict the behavior of a second data set. The validated model is then used to conduct a sensitivity analysis, which reveals conditions where biodegradation becomes desorption rate-limited. If the chemical is not pre-equilibrated with the soil prior to the onset of biodegradation, then fast sorption will reduce aqueous concentrations and thus biodegradation rates. Another sensitivity analysis demonstrates the importance of including nonlinear sorption in a coupled diffusion/sorption and biodegradation model. While predictions based on linear sorption isotherms agree well with solution concentrations, for the conditions evaluated this approach overestimates the percentage of contaminant biodegraded by as much as 50%. This research demonstrates that nonlinear sorption should be coupled with diffusion/sorption and biodegradation models in order to accurately predict bioremediation and natural attenuation processes. To our knowledge this study is unique in studying nonlinear sorption coupled with intraparticle diffusion and biodegradation kinetics with natural media.

Impacts of heterogeneous organic matter on phenanthrene sorption: different soil and sediment samples.

Organic petrography has been proposed as a tool for characterizing the heterogeneous organic matter present in soil and sediment samples. A new simplified method is proposed as a quantitative means of interpreting observed sorption behavior for phenanthrene and different soils and sediments based on their organic petrographical characterization. This method is tested under singe solute conditions and at phenanthrene concentration of 1 microg/L. Since the opaque organic matter fraction dominates the sorption process, we propose that by quantifying this fraction one can interpret organic content normalized sorption distribution coefficient (Koc) values for a sample. While this method was developed and tested for various samples within the same aquifer, in the current study the method is validated for soil and sediment samples from different sites that cover a wide range of organic matter origin, age, and organic content. All 10 soil and sediment samples studied had log Koc values for the opaque particles between 5.6 and 6.8. This range of Koc values illustrates the heterogeneity of opaque particles between sites and geological formations and thus the need to characterize the opaque fraction of materials on a site-by-site basis.