Microplastics, which are plastic debris with a particle diameter of less than 5 mm, have attracted growing attention in recent years. Its widespread distributions in a variety of habitats have urged scientists to understand deeper regarding their potential impact on the marine living resources. Most studies on microplastics hitherto are focused on the marine environment, and research on risk assessment methodology is still limited. To understand the distribution of microplastics in urban rivers, this study investigated river sediments in Shanghai, the largest urban area in China. Seven sites were sampled to ensure maximum coverage of the city's central districts, and a tidal flat was also included to compare with river samples. Density separation, microscopic inspection and μ-FT-IR analysis were conducted to analyze the characteristics of microplastics and the type of polymers. The average abundance of microplastics in six river sediment samples was 802 items per kilogram of dry weight. The abundance in rivers was one to two orders of magnitude higher than in the tidal flat. White microplastic spheres were most commonly distributed in river sediments. Seven types of microplastics were identified, of which polypropylene was the most prevailing polymers presented. The study then conducted risk assessment of microplastics in sediments based on the observed results, and proposed a framework of environmental risk assessment. After reviewing waste disposal related legislation and regulations in China, this study conclude that in situ data and legitimate estimations should be incorporated as part of the practice when developing environmental policies aiming to tackle microplastic pollution.

Microplastics in Freshwater River Sediments in Shanghai, China: A Case Study of Risk Assessment in Mega Cities

https://par.nsf.gov/servlets/purl/10172004

Valorization of hydrothermal liquefaction aqueous phase: pathways towards commercial viability

Conversion and removal strategies for microplastics in wastewater treatment plants and landfills

Oil from plastic via hydrothermal liquefaction: Production and characterization

Enhancement of depolymerization slag gasification in supercritical water and its gasification performance in fluidized bed reactor

In order to solve the problem of marine microplastics and realize the harmless resource utilization of plastics, the gasification experiments of polycarbonate (PC) microplastics were carried out in supercritical water and a novel seawater gasification of microplastic experiment was investigated. In this paper, the effects of different operating conditions (temperature, time, feedstock concentration, pressure) on gasification performance were discussed. The gasification kinetic of microplastics in supercritical water was calculated. The experimental results showed that the increase in gasification temperature and time enhanced the cracking reaction and free radical reaction of the microplastics to increase the gasification efficiency, while the reduction in feedstock concentration improved the gasification efficiency by increasing the gasification level of unit feedstock. The change in pressure had no significant effect on gasification due to the fact that the properties of the supercritical water were not significantly changed. It was found that the valuable results that all alkali metal salts in seawater promote hydrogen conversion, while in terms of carbon conversion, only KCl, CaCl2, NaHCO3 and seawater had a significant catalytic effect on the gasification. Seawater gasification of microplastics was a potential resource utilization method. Finally, it was considered that the PC plastic gasification conformed to the random nucleation and subsequent growth model (n = 3), and the reaction activation energy was 230.45 kJ/mol, which was smaller than that of traditional pyrolysis.

Experimental investigation on gasification characteristics of polycarbonate (PC) microplastics in supercritical water

The emulsification of heavy oil and water into a W/O emulsion would increase the viscosity of the W/O emulsion and reduce the mobility of heavy oil. As we know, addition of a viscosity reducer such...

Wei Zhang

Papers

Experimental investigation on gasification characteristics of polycarbonate (PC) microplastics in supercritical water

Study on the Re-emulsification Process of Water in Heavy Oil Emulsion with Addition of Water-Soluble Viscosity Reducer Solution

Progress in Bohai Offshore Heavy Oil Thermal Recovery

Treatment Technology of Steam Breakthrough for Offshore Heavy Oil Reservoirs Developed by Huff and Puff with Multi-Component Thermal Fluid

Integrated Tubing for Both Steam Injection and Oil Production of Thermal Wells Based on ESP in Offshore Oilfield China