Dhavamani, Jeyakumar (2022) Leaching of Phthalate Esters from Microplastics into Seawater. (PhD/ Doctoral thesis), Christian-Albrechts-Universität, Kiel, Germany, 176 pp.

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Abstract

The current thesis reports a clear understanding of the leaching process of six PAEs from three common consumer plastics, low and high-density polyethylene (LDPE, HDPE) and recycled polyethylene (RP). The effects of salinity, temperature, and ultraviolet irradiation (UVR) on leaching were investigated. Temperature and UVR had a positive effect on the leaching rate while increasing salinity had a negative effect on the leaching rate. The approach used in this study to measure PAEs takes into account the re-adsorption loss of each target compound during the leaching process. Significant re-adsorption of PAEs was observed for all three polymers, which can reduce the amount of actual/total leachate in the dissolved phase by up to 30-80%. This is an important step in understanding the hazards and extent of exposure to additives from plastic pollution. The second major focus of the work is to investigate the relationship between PAEs and PDs in the marine environment. We investigated the abundance of PDs and PAEs in the surface waters of Sharm Obhur Bay and the Red Sea. PAE concentrations in the study area ranged from 0.8 to 1224 ng/L, while the abundance of PDs ranged from (0.0301-0.0374 PDs/m3 ). A positive correlation was observed between the abundance of PDs and the concentration of PAEs, suggesting that a large portion of the dissolved PAE pool may be due to in situ leaching. The calculated ecological risk level (ERL) due to PAEs and PDs for Sharm Obhur and the Red Sea is currently at a low to moderate level. Overall, the work presented in this thesis helps in improving the available knowledge of the leaching process of PAEs from plastics under different environmental conditions. Particularly, in proper assigning the re-adsorption loss in the measurement of total leachates in water. On the other hand, the latest information regarding the distribution of PAEs and plastic waste and their ecological risk in the surface waters of the Red Sea and Sharm Obhur Bay is reported. An improved method for the analysis of PAEs was developed, including the control of blank contamination, and the experimental conditions such as extraction time and temperature were optimized. This information may be useful in the analysis of PAEs where it can be of great importance to obtain a precise determination of plastic additives in the complex environment.

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