Degradation-fragmentation of marine plastic waste and their environmental implications: A critical review

This review critically evaluates the plastic accumulation challenges and their environmental (primarily) and human (secondarily) impacts. It also emphasizes on their degradation and fragmentation phenomena under marine conditions. In addition, it takes into account the leachability of the various chemical substances (additives) embedded in plastic products to improve their polymeric properties and extend their life. Regardless of their effectiveness in enhancing the polymeric function of plastic products, these additives can potentially contaminate air, soil, food, and water. Several findings have shown that, regardless of their types and sizes, plastics can be degraded and/or fragmented under marine conditions. Therefore, the estimation of fragmentation and degradation rates via a reliable developed model is required to better understand the marine environmental status. The main parameter, which is responsible for initiating the fragmentation of plastics, is sunlight/UV radiation. Yet, UV- radiation alone is not enough to fragment some plastic polymer types under marine conditions, additional factors are needed such as mechanical abrasion. It should be also mentioned that most current studies on plastic degradation and fragmentation centered on the primary stages of degradation. Thus, further studies are needed to better understand these phenomena and to identify their fate and environmental effects.This paper was supported by Qatar University Internal Grant (No. QUCG-CAS-21/22-3). The findings achieved herein are solely the responsibility of the authors

Salinity Effects on Symbiodinium sp. growth rate in Controlled conditions and produced Biomass Biochemical Characterization

Salinity is an abiotic influencer to the growth and the efficiency of the algal Symbiodinium that coexists in symbiosis with corals. In light of the high salinity conditions that prevail in the Arabian Gulf including the waters of Qatar, we observed the effect of salinity above local-ambient levels on Symbiodinium's growth rate, biomass and its photosynthetic efficiency. Symbiodinium sp. extracted from Platygyra daedalea was launched in f/2 media in controlled incubator conditions at salinities of 30, 40 (control), 45, 50, 60 and 70 psu for 11 days. Subsamples were obtained and fixed for cell density counts and growth rate calculations. Photosynthetic efficiency was determined using an Aquapen, and biomass at the end of the experiment was sent for biochemical characterization. A two-way ANOVA test was performed on the data using SigmaPlot software. Our results indicated that at salinities 55 psu and greater, significant decline in both cell density and photosynthetic efficiency was observed. At 70 psu, growth rate was exclusively negatively affected, and biochemical compositions varied at all salinity levels with a notable increase in lipid content at 70 psu. Impact of high salinity has not been widely studied in the Arabian Gulf. Thus, this study will aid conservational efforts while also encouraging further studies on the contribution of abiotic factors to Symbiodinium sp. growth in the region

Insights into the degradation mechanism of PET and PP under marine conditions using FTIR

Plastics possess diverse functional properties that have made them extremely desirable. However, due to poor waste management practices, large quantities eventually end up in the oceans where their degradation begins. Hence, it is imperative to understand and further investigate the dynamics of this process. Currently, most relevant studies have been carried out under benign and/or controlled weather conditions. This study investigates the natural degradation of polypropylene (PP) and polyethylene terephthalate (PET) in more extreme environments. Simulated and real marine conditions, both in the laboratory (indoors) and outdoors were applied for a duration of 140 days and results were assessed using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis. SEM micrographs revealed variations in the morphologies of both plastic types. Degradation signs were shown in both plastic types, under all conditions. Findings indicated that microplastics (MPs) degraded faster than macroplastics, with PP MPs having higher weight loss (49%) than PET MPs (1%) when exposed to outdoor marine conditions. Additionally, the degradation rates of MPs-PP were higher than MPs-PET for outdoor and indoor treatments, with 1.07 ×10-6g/d and 4.41 ×10-7g/d, respectively. FTIR combined with PCA was efficient in determining the most degraded plastic types.This paper was supported by Qatar University Internal Grant (No. QUCG-CAS-21/22-3). The findings achieved herein are solely the responsibility of the authors. The SEM-EDX, DSC, and FTIR analyses were accomplished in the Central Laboratories unit, Qatar University