# Flowing Fibers: Subsurface Sampling Is Key to Understanding Natural and Plastic Textile Fiber Pollution in Rivers

## TL;DR

This study shows that sampling only the surface of rivers underestimates textile fiber pollution, including plastic and natural fibers, and highlights the need for subsurface sampling.

## Contribution

The study experimentally quantifies how riverbed roughness affects the transport of different textile fibers, revealing sampling biases.

## Key findings

- Riverbed substrate significantly alters fiber transport pathways for all tested fiber types.
- Surface-only sampling underestimates fiber fluxes regardless of fiber type.
- Subsurface sampling is essential to accurately assess riverine textile fiber pollution.

## Abstract

There is a pressing need to understand the pathways of
textile
fibers as anthropogenic pollutants in the environment. Current efforts
to understand textile fiber pollution in waterways have relied on
surface-sampling methodologies without consideration for environmental
heterogeneity. Moreover, how nonplastic textile fibers behave in the
environment is not known. Here, for the first time, we experimentally
quantify the role that fiber type (cotton, wool, polyester, and acrylic)
and riverbed roughness (flat, fine gravel, and coarse gravel) have
on the vertical distribution of transported fibers using an experimental,
recirculating flume. Analysis of the vertical profile distributions
of 18,793 cotton, wool, polyester, and acrylic fibers indicated that
bed substrate significantly altered fiber transport pathways, which
was consistent across all tested fiber types. Our findings indicate
that surface-only sampling will substantially under-record fiber fluxes,
but such biases did not differ between any tested fiber types. Our
findings provide key insights into fiber/bed interactions and transport
pathways and imply that current monitoring methodologies significantly
underestimate lotic (and potentially lentic) populations of fibers.
We argue that it is crucial to sample for all fiber types, throughout
the water column in all riverbed types, to understand fully the scale
of riverine textile fiber pollution.