I have been assembling a bibliography of marine litter – microplastic research and wanted to give a short update on my findings to date. My current microplastic bibliography is available here.
Springer has just released a 460 page open source book (link) on Marine Anthropogenic Litter which covers the entire marine – freshwater microplastic research field very well.
This book provides up-to-date information by the leading microplastic researchers. Microplastic ingestion has been observed and documented in hundreds of marine species.
More recently, elevated microplastics levels have been found in the Great Lakes, North Shore Channel, Hudson River and Chesapeake Bay, so there is reason to be concerned about expect elevated levels in the Schuylkill – Delaware Rivers.
Sewage treatment plants have been identified as one source of microplastic discharge. Researchers have sampled for microplastics in the Chicago area North Shore Channel, upstream and downstream of Chicago area’s Terrence J O‘Brien Water Reclamation Plant and have found elevated levels of microplastics downstream of the plant discharge.
Table 1 of the paper is reproduced below:
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This Chicago activated sludge treatment plant discharges very high levels of microplastic fibers and fragments with values considerably higher than those found in the Great Lakes and N Pacific, as shown in Figure 1 from the paper.
If follow-up studies confirm the North Shore Channel and TJ O’Brien plant microplastic discharge levels, then urban rivers and municipal treatment plant discharges will be identified as potential significant sources of marine microplastics.
Microplastics in the marine environment has been well researched. Work on microplastics in freshwater is just beginning. The role of wastewater treatment plants and stormwater runoff will be important focus of upcoming research.
Philadelphia is in a particularly difficult situation. Downstream of large – developed basins, Philadelphia’s Schuylkill and Delaware River water supply intakes likely see elevated microplastics levels and the City’s 3 wastewater treatment plants and stormwater runoff likely contribute microplastics to the Delaware Estuary and Bay.
We know microplastics present a serious challenge to the marine environment, recent freshwater research is showing that microplastics are also a freshwater challenge. Clearly we need a research program focused on microplastics in the Schuylkill – Delaware Rivers.