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[MIS20-10] Chemical properties of film coatings developed on microplastics distributed on the urban river shore in Mongolia
Keywords:biofilm, polystyrene foam, composition of organic substances, N containing functional groups, micro-FTIR
Plastics released into environment are deteriorated by solar radiation, physical impacts and freeze-thaw cycles, resulting in increase in surface areas of microplastics accompanied by reaction with pollutants. The reactivity of plastics can also be altered by organic matter coating which mainly mediated by microbial activity. Plant residues and minerals participated to the surface coating can induce various reaction on the surface. Environmental conditions where plastics reside also characterize the surface coating of plastics. Composition of plastic coatings can record the fate of plastics after release into environment. This study targets the surface coating of plastics by spectral analyses.
Samples of microplastics were polystyrene foams collected on a river shore along the Tuul River in Ulaanbaatar, Mongolia. Polystyrene foams, which were dominant plastics in the study area, distribute widely from the upper to lower stream. Those polystyrene foams have reached to the present positions through various processes, resulting that some are broken into numerous pieces with different color and others are probably well aged. Components consisting of the coating on the polystyrene surface were evaluated by a micro-FTIR spectroscopy. The differences in spectra between intact and digested surfaces of polystyrene were considered as spectra from the surface coating of polystyrene. IR absorptions at specific wavenumbers were statistically analyzed by the principal component analysis for classification of types of coatings.
Most of absorption peaks were assigned as characteristic organic functional groups mainly consisting of microorganisms, fragments of arthropods and plant debris derived from ligno-cellulose. Contribution of the assigned organic constituents were diverse in various coatings on polystyrenes which distributed in different environments. The nitrogen containing functional groups such as amino residues and peptides coupling with carbonyl groups strongly contributed to PC1 and classified polystyrene foams well. Polystyrene foams coated with living or dead microorganisms can be separated by PC1. The second principal component was characterized by lignin moieties consisting of aromatic rings with carbonyl stretching vibration, indicating that positive scores mean participation of plant residues into the surface coating developed on polystyrene distributed a dry shore region covered with vascular plants. The collected information from organic coatings explained the status of polystyrene foams under several different environmental conditions.
Samples of microplastics were polystyrene foams collected on a river shore along the Tuul River in Ulaanbaatar, Mongolia. Polystyrene foams, which were dominant plastics in the study area, distribute widely from the upper to lower stream. Those polystyrene foams have reached to the present positions through various processes, resulting that some are broken into numerous pieces with different color and others are probably well aged. Components consisting of the coating on the polystyrene surface were evaluated by a micro-FTIR spectroscopy. The differences in spectra between intact and digested surfaces of polystyrene were considered as spectra from the surface coating of polystyrene. IR absorptions at specific wavenumbers were statistically analyzed by the principal component analysis for classification of types of coatings.
Most of absorption peaks were assigned as characteristic organic functional groups mainly consisting of microorganisms, fragments of arthropods and plant debris derived from ligno-cellulose. Contribution of the assigned organic constituents were diverse in various coatings on polystyrenes which distributed in different environments. The nitrogen containing functional groups such as amino residues and peptides coupling with carbonyl groups strongly contributed to PC1 and classified polystyrene foams well. Polystyrene foams coated with living or dead microorganisms can be separated by PC1. The second principal component was characterized by lignin moieties consisting of aromatic rings with carbonyl stretching vibration, indicating that positive scores mean participation of plant residues into the surface coating developed on polystyrene distributed a dry shore region covered with vascular plants. The collected information from organic coatings explained the status of polystyrene foams under several different environmental conditions.