Partitioning of Pesticide-Related Residues Between Dissolved and Particulate Phases in River Water

The environmental behaviour of pesticides in river systems is strongly influenced by their partitioning between dissolved water and suspended particulate matter (SPM). While regulatory monitoring programs primarily target dissolved-phase concentrations of pesticide active ingredients, increasing evidence indicates that a substantial fraction of pesticide-related residues—including parent compounds, transformation products, and formulation-derived additives—preferentially associate with particulate phases. This review synthesizes recent advances in understanding the mechanisms governing phase partitioning of pesticide-related residues in river water. Emphasis is placed on physicochemical drivers, hydrological controls, analytical strategies—particularly GC–MS-based non-target screening—and the role of SPM as both a transport vector and environmental reservoir. The implications of phase partitioning for monitoring design, exposure assessment, and ecological risk evaluation are critically discussed. The review highlights the need for integrated dissolved–particulate monitoring frameworks to accurately characterize pesticide contamination in riverine environments. The implications of phase partitioning for environmental monitoring, exposure assessment, and risk evaluation are discussed, highlighting the need for integrated water–SPM monitoring strategies.