According to foreign media reports, plastic is an increasingly serious problem for the global natural ecosystem, especially for our marine and freshwater environment. Rivers are the main source of plastic pollution, because it is estimated that due to poor management of land waste, rivers transport millions of metric tons of plastic to our oceans every year.

The problem is that the amount of plastic flowing out of rivers is estimated to be tens to hundreds of times higher than that floating on the ocean surface. So, where did the plastic in the river go-is there a lost plastic "sink" somewhere in the ocean? Are these estimates correct?

In a paper recently published in the journal Science, Dr. Lisa Weiss from the Mediterranean Center for Environmental Education and Research (CEFREM) and her colleagues, a joint research laboratory composed of the university of perpignan (UPVD) and the French National Center for Scientific Research (CNRS), and research teams from some French research institutions and the University of Barcelona, Spain, proved that the current river flow assessment is two or three orders of magnitude higher than the previous estimate. This will explain why a large number of microplastics seem to disappear in a mysterious ocean "plastic sink".

However, these findings do not mean that there are fewer problems with plastics than previously thought. In fact, through the analysis, the researchers actually found that the time for plastic to stay on the ocean surface is much longer than previously estimated, which further aggravated the impact of plastic pollution on natural systems.

Mysterious marine plastic precipitation

Rivers are the main source of plastics discharged into the sea. According to the current assessment, the stock of microplastics floating on the ocean surface ranges from tens to hundreds of metric tons, which is only a fraction of the millions of metric tons discharged by rivers every year. This unequal balance leads to the hypothesis of "plastic tank", that is, the amount of microplastics in the "plastic tank" plus the plastic on the sea surface will be equal to the plastic discharged into the sea by the river.

The main author of the research paper, Dr. Lisa Weiss of CEFREM Laboratory in university of perpignan, said: "Compared with the earlier empirical model research, the field data of microplastics in rivers we have now enable us to establish a powerful database, and then we can analyze it to obtain a more reliable estimate of the amount of microplastics discharged into the ocean by rivers. This process reveals several main methodological errors in previous traffic estimation. When we correct these mistakes, we find that the estimated flow of global rivers is two or three orders of magnitude less than previously thought. In addition, we found that the average stay time of microplastics on the ocean surface may actually be several years, not a few days previously estimated. "

Miquel Canals, head of the comprehensive research group of marine geosciences at the University of Barcelona and one of the co-authors of the research paper, pointed out: "We can now confirm that the search for the missing' plastic tank' has ended, because the missing plastic has been found through the correction of river flow estimation."

This new study identified the errors of mainstream methods, which led to inaccurate assessment of the global microplastics discharge and overall quality of rivers discharged into the ocean, especially due to systematic overestimation of the average weight of microplastics particles in river samples, integration of incompatible data obtained by different sampling techniques, and assessment based on the relationship between microplastics discharge and MPW index (poorly managed plastic waste), which led to errors.

The borderless struggle to protect the earth's oceans.

Marine garbage knows no boundaries, and it has reached the most remote corner of our ocean. According to Dr. Wolfgang Ludwig, director of CEFREM Laboratory and co-author of the study, "The only way we have a chance to win the fight against pollution in microplastics is to target the source of waste in microplastics. We need to take action at the human level. We need to change our consumption habits and manage our waste better. We need to do this on a global scale. "

"Our research shows that marine microplastics pollution not only comes from developing countries as people think-there is almost no waste management, but also comes from countries with perfect waste management systems," Dr. Ludwig pointed out. "If we stop discharging microplastics from rivers to the ocean today, the number of floating particles and their harmful effects on marine ecosystems will last for at least several years."

Next step ...

The influence of plastics on marine environment is a new field of scientific research, and a large number of scientific publications have been produced in the past few years. However, we are just beginning to understand how plastics circulate in the ocean. There are many plastic size categories, ocean zoning and the transfer process from land to ocean that need to be further studied in order to correctly evaluate the stock size and exchange flux between zoning. Looking ahead, if we have a chance to win the fight against plastic pollution, we will need the best available science. To this end, the scientific community must work together to overcome the inertia of the past, correct mistakes, and work under the same agreements and guidelines to provide the best decision-making suggestions needed to protect our oceans.