I think this may be a good solution for those countries where trash more or less accidentally ends up in rivers. But what percentage of trash ends up accidental

I think this may be a good solution for those countries where trash more or less accidentally ends up in rivers. But what percentage of trash ends up accidentally in the sea, and how much trash is intentionally dumped because it's cheaper or easier? I would assume that's far less than the 8 billion kilos per year quoted on the page.