title: Sorption capacity of plastic debris for hydrophobic organic chemicals.
abstract: The occurrence of microplastics (MPs) in the ocean is an emerging world-wide concern. Due to high sorption capacity of plastics for hydrophobic organic chemicals (HOCs), sorption may play an important role in the transport processes of HOCs. However, sorption capacity of various plastic materials is rarely documented except in the case of those used for environmental sampling purposes. In this study, we measured partition coefficients between MPs and seawater (KMPsw) for 8 polycyclic aromatic hydrocarbons (PAHs), 4 hexachlorocyclohexanes (HCHs) and 2 chlorinated benzenes (CBs). Three surrogate polymers - polyethylene, polypropylene, and polystyrene - were used as model plastic debris because they are the major components of microplastic debris found. Due to the limited solubility of HOCs in seawater and their long equilibration time, a third-phase partitioning method was used for the determination of KMPsw. First, partition coefficients between polydimethylsiloxane (PDMS) and seawater (KPDMSsw) were measured. For the determination of KMPsw, the distribution of HOCs between PDMS or plastics and solvent mixture (methanol:water=8:2 (v/v)) was determined after apparent equilibrium up to 12 weeks. Plastic debris was prepared in a laboratory by physical crushing; the median longest dimension was 320-440 μm. Partition coefficients between polyethylene and seawater obtained using the third-phase equilibrium method agreed well with experimental partition coefficients between low-density polyethylene and water in the literature. The values of KMPsw were generally in the order of polystyrene, polyethylene, and polypropylene for most of the chemicals tested. The ranges of log KMPsw were 2.04-7.87, 2.18-7.00, and 2.63-7.52 for polyethylene, polypropylene, and polystyrene, respectively. The partition coefficients of plastic debris can be as high as other frequently used partition coefficients, such as 1-octanol-water partition coefficients (Kow) and log KMPsw showed good linear correlations with log Kow. High sorption capacity of microplastics implies the importance of MP-associated transport of HOCs in the marine environment.
authors.affiliation: Division of Environmental Science and Ecological Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 136-701, Republic of Korea.
authors.forename: Hwang
authors.initials: H
authors.lastname: Lee
authors.affiliation: Oil and POPs Research Group, Korea Institute of Ocean Science and Technology, 391 Jangmok-myon, Geoje 656-834, Republic of Korea.
authors.forename: Won Joon
authors.initials: WJ
authors.lastname: Shim
authors.affiliation: Division of Environmental Science and Ecological Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 136-701, Republic of Korea. Electronic address: junghwankwon@korea.ac.kr.
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Kwon
mesh_terms: D000327:Adsorption; D004784:Environmental Monitoring; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D010969:Plastics / Q000032:analysis*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry*; D014866:Waste Products / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D010969:Plastics; D011084:Polycyclic Aromatic Hydrocarbons; D014866:Waste Products; D014874:Water Pollutants, Chemical
keywords: Equilibrium partitioning; Marine pollution; Microplastics; Nanomaterial; New POPs; QSARs