BayCEER Workshop 2026

An inverse size-space framework for constraining microplastic fragmentation models from particle-size distributions

P 11 in Posters

Understanding how environmental conditions shape microplastic particle-size distributions requires a connection between measurable statistical features and candidate fragmentation mechanisms. We develop an inverse size-space framework that uses the hazard function to establish this connection. An observed distribution is expressed through an effective hazard, which is decomposed into a reference fragmentation law and a dimensionless environmental modulation. This representation brings characteristic-scale and scale-free behaviours into a common framework and allows departures from exponential and power-law distributions to guide physical model construction. We also derive the bias caused by upper measurement truncation and correct the inferred hazard using an assumed tail continuation.

Two environmental models illustrate the approach. For soil microplastics, a pore-related length controls collision activation relative to a characteristic-scale baseline. Increasing activation at small sizes and decreasing cumulative abundance at larger sizes together produce a distribution peak, followed by an exponential tail after activation saturates. For aquatic microplastics, environmental activation modulates a scale-free baseline, introducing a small-size transition while retaining a power-law tail. A model motivated by UV-assisted damage accounts for this behaviour through an activation exponent and a characteristic crossover length. Comparisons with measured soil and aquatic distributions reproduce their principal peaks, shoulders, and decreasing branches.

The framework provides statistical constraints on fragmentation models while making their environmental assumptions explicit. By distinguishing reference size dependence from environmental modulation, it connects observed distribution shapes to characteristic scales and candidate mechanisms that can be examined experimentally.

models of fragmentation in soil and ocean surface

Keywords: microplastics, fragmentation, inverse-evolution, particle-size distribution