Volunteer cleanup efforts reveal differences in anthropogenic litter composition found in shoreline and riverine environments

Abstract:

Anthropogenic litter (AL) is commonly seen on beaches and in streams and is frequently targeted by volunteer cleanup efforts. Streams and rivers are conduits in which AL is able to travel to oceans and beaches, but the human uses and energetics of the environments differ, potentially affecting how AL is generated, transported and deposited. Publicly available databases of cleanups focus on beaches and shorelines, while stream and river cleanup data are less available, so comparisons of differences in AL composition by environment have not been widely made. Here we use data from the Ocean Conservancy and local data sources to compare the composition and material types of AL found in shoreline and riverine environments during volunteer cleanups in northeast Ohio, USA from 2016-2020.

There were more shoreline (180) than riverine (25) cleanups in our database, but volunteer data reveals abundant AL in both environments (>2200 items per cleanup). Compared to shorelines, riverine locations generated >26 kg more AL per cleanup and 1.8 kg more AL per person, and rivers also had 10 more items categorized as “large dump” per cleanup. The percentage of items that could contain plastic at shoreline was higher (95.6%) than riverine cleanups (90.5%). When looking at the identifiability of the plastics, riverine areas had more identifiable plastics (68.1%) than shorelines (55.9%).

Plastics are a higher percent of cleaned materials on beaches and other shorelines, relative to streams, probably due to the lower density of plastic materials allowing them to be transported out of rivers or washed onto shorelines. Shoreline plastics are also more likely to be broken down into unidentifiable fragments than those cleaned from streams, another possible effect of transport processes. On the other hand, construction materials and other large items are more common in rivers, likely because they are heavier and less easily transported. While volunteer cleanup data is beneficial, data quality varies and there are potential seasonal biases. Uncertainty in exact cleanup location is a major limitation to more detailed analyses. More spatially detailed work within shoreline and riverine environments may help explain differences in the types and materials of AL found in these locations.