The effect of UV exposure on conventional and degradable microplastics adsorption for Pb (II) in sediment.

Plastic discharged into the environment would break down into microplastics (MPs). However, the possible impact of MPs on heavy metals in the aquatic sediment remains unknown. In order to evaluate the potential role of MPs as carriers of coexisting pollutants, the adsorption capacity of lead ions from sediment onto aged degradable and conventional MPs were investigated as a function of lead ions concentration, contact time, temperature, MPs dosage, aging time, and fulvic acid concentration. MPs were exposed to UV to obtain aged polyethylene (A-PE) and aged polylactic acid (A-PLA). The aging treatment increased the oxygen content, specific surface area and hydrophilicity of MPs. The adsorption capacity of A-PE for Pb(II) in sediment increased from 10.1525 to 10.4642 mg g-1 with the increasing aging time. However, the adsorption capacity of A-PLA for Pb(II) in sediment decreased from 9.3199 to 8.7231 mg g-1 with the increasing aging time. The adsorption capacity of MPs in sediment for Pb(II) was in the following order: A-PE > PLA > PE > A-PLA. Fulvic acid could promote the adsorption of Pb(II) by MPs in sediment. These results indicated that the aging process of the plastics in the environment would affect its role as a carrier of coexisting pollutants.

Effects of virgin microplastics on the transport of Cd (II) in Xiangjiang River sediment.

River sediments are considered as sinks of microplastics (MPs). Although numerous studies have been conducted on MPs pollution in river sediments, the impact of MPs on the environmental behavior of Cd (II) in river sediments is still unknown. In this work, the effects of six MPs (polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate and polylactic acid) on the adsorption of Cd (II) by Xiangjiang River sediment and the transport of Cd (II) in sediment were studied. The results showed that the adsorption ability of sediment to Cd (II) decreased with the increase of the content of MPs in sediment. When the content of MPs in sediment increased to 10%, polypropylene had the greatest effect on the adsorption affinity of sediments to Cd (II). Moreover, the addition of MPs accelerated transport of Cd (II) in sediment, and the transport of Cd (II) in sediment increased with the increase of the content of MPs. The reason may be that after adding MPs, the adsorption capacity of sediment to Cd (II) decreases, and the mass transfer resistance of Cd (II) to sediment reduces, which leads to faster transport of Cd (II) in sediment. Especially, when the content of MPs in sediment increased to 10% (w/w), the saturation point of the breakthrough curve decreased by about 70 pore volumes. This work hopes to provide helpful views on the environmental behavior and risk assessment of Cd (II) in the presence of MPs.

Smoked cigarette butts: Unignorable source for environmental microplastic fibers.

The pollution of microplastics and their potential environmental hazards have attracted considerable attention of the public. Cigarette butts, composed of cellulose acetate, are one of the most common plastic pollutants in the environment. Of all the litter that is discarded at will, cigarette butts are the most acceptable. Cigarette butts are dangerous pieces of plastic, but are usually not handled properly and consist of more than 15,000 detachable strands of plastic fiber. Discarded cigarette butts may be carried into rivers and lakes, and finally into the ocean. The plastic fibers will continuously release microplastic fibers into the environment. About 300,000 tons of potential microplastic fibers may enter the aquatic environment from this source per annum. Additionally, toxic substances, such as nicotine, carcinogenic tar, and polycyclic aromatic hydrocarbons, have strong toxic effect, which will cause serious damage to aquatic organisms. However, the mechanism and rate of microplastic fibers release from smoked cigarette butts and the joint toxicity of microplastic fibers and toxic pollutants to aquatic organisms are still in the initial stage. Therefore, it is necessary to understand the mechanism of cigarette butts releasing microplastic fibers, the potential impact on the environment and possible measures to reduce the impacts of cigarette butt litter. The aim of this paper is to evaluate the potential sources of smoked cigarette butts as environmental fiber microplastics and the potential ecological effects of the released microplastic fibers on the ecosystem. In addition, some ways which could help to tackle problem of smoked cigarette butts pollution have also been proposed.