Freshwater microplastic concentrations vary through both space and time

Abstract

Plastic pollution represents one of the most salient indicators of society's impact on the environment. The microplastic component of this is ubiquitous, however, microplastic studies are seldom representative of the locations they sample. Over 12 months we explored spatiotemporal variation in microplastic prevalence across a freshwater system and in atmospheric deposition within its catchment, in one of the most temporally comprehensive studies of microplastic pollution. Microplastics were quantified in low concentrations (max 0.4 particles L -1 ) at all freshwater sites, including upstream of urban areas, and on rivers that do not receive wastewater treatment plant effluent. Extrapolated microplastic abundances at each site varied by up to 8 orders of magnitude over the course of the sampling campaign, suggesting that microplastic surveys that do not account for temporal variability misrepresent microplastic prevalence. Whilst we do not wish to underplay the potential impacts of microplastic particles in the environment, we argue that microplastic pollution needs to be placed in a more critical context, including assessment of temporal variability, to appropriately inform legislators and consumers. CapsuleThe main findings of this research are the extent to which freshwater microplastic concentrations are shown to vary with time, and the influence of this on flux calculations.

Total coliform and Escherichia coli in microplastic biofilms grown in wastewater and inactivation by peracetic acid

“…For the influent experiment, reactors were prepared with LDPE and wood in the same manner. LDPE was chosen for the influent experiment as it is extremely common in environmental samples (Kershaw & Rochman, 2015; Stanton, Johnson, Nathanail, MacNaughtan, & Gomes, 2020) and to reduce the size of the experimental matrix. As an inoculum control, separate reactors were prepared using DI water instead of wastewater to incubate MP (LDPE) and wood particles.…”

Presence and fate of microplastics in the water sources: focus on the role of wastewater and drinking water treatment plants

“…River mouths appears to be often a concentration spot for MPs, while the straight tracts seem to ease MPs flow along the river compared to inner and outer bends [31,[35][36][37]. Atmospheric deposition is also considered: Constant et al [38] evaluated the role of MPs atmospheric deposition as possibly significant; by contrast, Stanton et al [39] considered such contribution being not important but argued that the low values recorded could be linked e.g. to the sampling height and other various environmental and meteorological factors.…”

It's the product not the polymer: Rethinking plastic pollution

“…Plastic has been found in even the most remote locations including Arctic ice floes (Bergmann et al, 2019) and the deep sea (Chiba et al, 2018); however, it is not distributed equally around the planet. Microplastic surveys in particular seldom report very low concentrations, but they do occur (Stanton, Johnson, Nathanail, MacNaughtan, & Gomes, 2020). True indications of global distributions of plastic prevalence are hard to ascertain in a field where monitoring exercises are focused on highly developed and/or connected systems.…”

“…Estimating plastic prevalence is especially complicated for microplastic particles, the majority of which are sourced from the breakdown of plastic in the environment, which is not consistent between products, polymers, and environments. Current understanding of the environmental prevalence of microplastic particles, particularly in the freshwater environment, is also based on research that seldom considers the variability of the environment under investigation (Stanton et al, 2020). Moreover, microplastic concentrations are often presented in units that unduly inflate recorded values.…”

“…Apart from representing poor science, when gross extrapolation is combined with variable methodologies, low sampling volumes and no understanding of temporal variability, the potential for the incorporation of large errors is high. Indeed, collecting 13 samples over the course of 12 months, Stanton et al (2020) found extrapolations from a single site varied over eight orders of magnitude depending on which of their measurements were used. Extrapolations over this scale almost inevitably result in large, misleading numbers, which can lead to alarmist headlines and are difficult to interpret, especially by the public, political groups, and those seeking to manage the problem.…”