There is plenty of stuff out there to spend your time reading about marine litter. It is good to get some guidance to find the most relevant right away e.g. as a entry to know where to start or as a quick reference in case one is asking.
One example is Nick Wehner's article on www.marinedebris.info which provides a set of Top 10 must read articles about marine debris allowing to take a first dive into the subject.
Also good to visit NOAA's page on marine debris.
If you like check out the link collection here at Floating Horizon which focuses (on this website) mainly on things helpful to assess the right technology for one or the other purpose around marine litter.
Perhaps one of the tricky things is that the collection has to filter out not only the low quality sources but also sources which are very good in quality but not relevant for one or the other interest, so it might become equally interesting to read what is not written ;) .
Enjoy the Day!