4:30 PM - 4:45 PM
[MIS20-11] A trial of small microplastics collection by Neuston net
Keywords:Small Microplastics, Neuston Net
Introduction:
The most efficiently as well as widely used sampling method for microplastics is neuston net due to its easy maneuverability, which normally has mesh size around 350μm. Therefore, researchers could be able to estimate the abundance and distribution of microplastics of the sea area. However, the contamination of small microplastics (less than 350μm) in the ocean cannot be researched and known because small microplastics escape from mesh. It is considered that the small microplastics perhaps cause more harm to the ecosystem and marine organism. Thus, we need to research on small microplastics urgently and systematically.
In this study, double neuston net (interior mesh size: 350μm; exterior mesh size: 50μm; 2 cod ends, Rigo Co. Ltd) and normal neuston net (mesh size: 350μm, Rigo Co. Ltd) were used to sample both the large microplastics (>350μm) and the small microplastics (50μm-350μm). Further, the aims of this study examined collecting method of the small microplastics and revealing the pollution of small microplastics in the sea area.
Materials and Methods:
Two observations were accomplished on 2020, in which, the fist observation containing 2 stations (Station 1, Station 2) was complemented from Nov. 9-Nov.11 in Tokai off the sea area, Japan, by T/V Shinyo Maru (986t, 64.6m) of Tokyo University of Marine Science and Technology (TUMSAT), the second observation containing 2 stations (Station 3, Station 4) was conducted on Dec. 12 in Tokyo Bay by T/V Seiyo Maru (170t, 35.5m) of TUMSAT.
Both neuston nets were equipped with flow meter. Moreover, tow speed, tow time were set to 1 knot of log speed, 10 minutes, respectively. Additionally, 2 samples can be obtained by double neuston net at one time. After sampling, samples were kept at refrigerator on cruise then transferred to laboratory. As to samples from 350μm-mesh neuston net, they were processed in a sequence of wet peroxide oxidation (WPO), density separation, picking up, microscope-based morphology recording, FTIR-based (Fourier-Transform infrared spectroscopy) spectrum measuring. On the other hand, the procedures of samples from 50μm-mesh neuston net were as same as 350μm-mesh neuston net samples until density separation, and the samples were filtrated by PTFE filters and the filters were scanned by μFTIR.
Results:
The concentrations of normal neuston net are 0.28 pieces/m3 in Station 1, 0.11 pieces/m3 in Station 2. Comparatively, double neuston net with 350μm mesh has the concentrations of 0.38 pieces/m3 in Station 1, 0.10 pieces/m3 in Station 2. No significant difference was found between these two neuston net. Yet, double neuston net with 50μm mesh has definitely higher concentration than those with 350μm, with the values of 15205±1288 pieces/m3 in Station 1, 3389±1315 pieces/m3 in Station 2.
As to the categories, PE (25.9%), PP (7.1%), PA (4.5%), PS (23.2%), PET (8.0%) have high percentage of large microplastics, while ‘others’ only account for 8.9%. By comparison, PE (5.4%), PP (1.5%), PA (1.5%), PS (0.2%), PET (1.9%) are all the minorities while ‘others’, including PolyHexadeculethylene, PolyOctadecylacrylamide, plastics additives etc., take a large proportion (74.2%) of small microplastics. Particles within 50μm~60μm have the peak concentration in the particle size distribution. Besides, the particle concentrations decrease with increasing size. Therefore, it could be concluded that particles below 50μm have the higher concentration compared to particles above 50μm.
The most efficiently as well as widely used sampling method for microplastics is neuston net due to its easy maneuverability, which normally has mesh size around 350μm. Therefore, researchers could be able to estimate the abundance and distribution of microplastics of the sea area. However, the contamination of small microplastics (less than 350μm) in the ocean cannot be researched and known because small microplastics escape from mesh. It is considered that the small microplastics perhaps cause more harm to the ecosystem and marine organism. Thus, we need to research on small microplastics urgently and systematically.
In this study, double neuston net (interior mesh size: 350μm; exterior mesh size: 50μm; 2 cod ends, Rigo Co. Ltd) and normal neuston net (mesh size: 350μm, Rigo Co. Ltd) were used to sample both the large microplastics (>350μm) and the small microplastics (50μm-350μm). Further, the aims of this study examined collecting method of the small microplastics and revealing the pollution of small microplastics in the sea area.
Materials and Methods:
Two observations were accomplished on 2020, in which, the fist observation containing 2 stations (Station 1, Station 2) was complemented from Nov. 9-Nov.11 in Tokai off the sea area, Japan, by T/V Shinyo Maru (986t, 64.6m) of Tokyo University of Marine Science and Technology (TUMSAT), the second observation containing 2 stations (Station 3, Station 4) was conducted on Dec. 12 in Tokyo Bay by T/V Seiyo Maru (170t, 35.5m) of TUMSAT.
Both neuston nets were equipped with flow meter. Moreover, tow speed, tow time were set to 1 knot of log speed, 10 minutes, respectively. Additionally, 2 samples can be obtained by double neuston net at one time. After sampling, samples were kept at refrigerator on cruise then transferred to laboratory. As to samples from 350μm-mesh neuston net, they were processed in a sequence of wet peroxide oxidation (WPO), density separation, picking up, microscope-based morphology recording, FTIR-based (Fourier-Transform infrared spectroscopy) spectrum measuring. On the other hand, the procedures of samples from 50μm-mesh neuston net were as same as 350μm-mesh neuston net samples until density separation, and the samples were filtrated by PTFE filters and the filters were scanned by μFTIR.
Results:
The concentrations of normal neuston net are 0.28 pieces/m3 in Station 1, 0.11 pieces/m3 in Station 2. Comparatively, double neuston net with 350μm mesh has the concentrations of 0.38 pieces/m3 in Station 1, 0.10 pieces/m3 in Station 2. No significant difference was found between these two neuston net. Yet, double neuston net with 50μm mesh has definitely higher concentration than those with 350μm, with the values of 15205±1288 pieces/m3 in Station 1, 3389±1315 pieces/m3 in Station 2.
As to the categories, PE (25.9%), PP (7.1%), PA (4.5%), PS (23.2%), PET (8.0%) have high percentage of large microplastics, while ‘others’ only account for 8.9%. By comparison, PE (5.4%), PP (1.5%), PA (1.5%), PS (0.2%), PET (1.9%) are all the minorities while ‘others’, including PolyHexadeculethylene, PolyOctadecylacrylamide, plastics additives etc., take a large proportion (74.2%) of small microplastics. Particles within 50μm~60μm have the peak concentration in the particle size distribution. Besides, the particle concentrations decrease with increasing size. Therefore, it could be concluded that particles below 50μm have the higher concentration compared to particles above 50μm.