Page 34 - Plastics News May 2020

TUS Scientists Develop a New Method to Track be ingested by marine organisms, which can negatively
Plastic Emissions from Land to Sea affect ecosystems worldwide. To avoid the emission of
MicP in water bodies, it was important to find out exactly
cientists from the Tokyo University of Science (TUS) in where these emissions were coming from. The scientists
SJapan have come up with a new method to track followed a three-step process to map plastic emissions.
plastic emissions from inland areas to the sea. This First, they measured MicP concentration across 70 rivers
method is useful to identify the “hotspots” of plastic and 90 sites in Japan and examined the relation between
emission and can even help to implement appropriate MicP concentration and land characteristics. They
measures to avoid plastic pollution. Because plastic does collected the ratio of MacP/MicP concentrations to
not decompose in water, it is a serious hazard for marine evaluate the MacP concentration from the MicP
life. To prevent plastic pollution, it is crucial to concentration. Next, to obtain outflow discharge at 1 km
understand exactly how plastic is emitted into the grids, they performed a “water balance analysis” in
oceans. A group of scientists at the Tokyo University of which they measured precipitation of water, distributed
Science, led by Prof Yasuo Nihei, developed a new into three categories: evaporation, surface runoff, and
method to combat plastic emissions. In a study published underground infiltration. Finally, they calculate total
in Water, they generated a “high-resolution map of 1 km plastic emission, which is the product of MicP and MacP
grids of plastic emissions across Japan. Prof Nihei concentrations and outflow discharge. Their findings
explains, “If plastic waste continues to flow into the sea, revealed that MicP concentrations and basin
the amount of plastic waste will increase. To prevent characteristics were significantly correlated, meaning
this, it is necessary to clearly indicate where and how that the physical features of water bodies dictate the
plastic debris is currently being generated.” To begin amount of plastic waste accumulated. Their analysis
with, the scientists focused on the different types of helped the scientists to estimate the annual plastic
plastics: microplastic (MicP), which is less than 5 mm in emission in Japan, which ranged from 210 to 4,776
size, and macroplastic (MacP), which is greater than 5 tons/year of total plastic. The scientists then evaluated
mm. They understood that controlling MicP was crucial a high-resolution map of plastic emission over 1 km grids
because owing to its small size it is particularly hard to across Japan.
recover once it enters the ocean. Moreover, it can easily

They identified the critical areas where plastic emissions were the highest. Their analysis showed that these emissions
were high in rivers near urbanized areas, with a high population density. Among these, cities like Tokyo, Nagoya, and
Osaka were found to be hotspots for plastic emissions.

MAY 2020 34 Plastics News