In response to regulatory agency initiatives to improve understanding of the types and quantities of microplastic particles being discharged into Monterey Bay by municipal wastewater agencies, CCLEAN added microplastics as an emerging contaminant to be measured under the program in 2020. Although there are currently no restrictions for daily loads of microplastics being discharged into Monterey Bay in wastewater, the information provided by this microplastics pilot monitoring program will enable resource managers to assess whether estimated loads from wastewater and rivers are sufficient to warrant further measurements or regulatory actions.
In 2021, the sum of daily loads of anthropogenic microparticles from five effluent sources was almost two times greater than the sum of daily loads from three river sources discharging into Monterey Bay National Marine Sanctuary. Fibers, both plastic and natural-based, were the dominant microparticle morphology type in all effluent and river samples collected in 2021. Fragments were the second most abundant microparticle morphology type for all effluent and river sites, apart from Monterey One Water, where films were the second most abundant. In dry season of 2021, fiber, fragment, and fiber bundle microparticle types were present in Santa Cruz City and County influent sources. The City of Santa Cruz effluent, however, only contained fiber microparticles. Estimated daily loads of anthropogenic microparticles also decreased by about 99.95% between the combined Santa Cruz City and County influent and Santa Cruz effluent stages, suggesting that the majority of anthropogenic microparticles may have been removed, or settled in the storage tanks, during wastewater treatment processes before being discharged as effluent.
