Terrestrial inputs of synthetic musks from Chinese mainland to the East China Sea

Synthetic musks (SMs), widely used in personal care and household products, have been identified as emerging contaminants in aquatic environments. However, large-scale assessment of their terrestrial inputs to coastal oceans and associated environmental implications remain limited. This study firstly conducted a comprehensive, multi-seasonal investigation of SMs in the riverine runoff from major river outlets along the East China Sea coast, as well as in effluents from representative coastal wastewater treatment plants. Fluxes and relative contributions of SMs from both sources were quantified. Rivers in eastern China were broadly contaminated by SMs, particularly the polycyclic musks galaxolide (HHCB) and tonalide (AHTN). Riverine input was the dominant source of SMs to the East China Sea, with an estimated flux of 32.4 metric tons for the sampled year, of which 67% was in the aqueous phase, and over half was delivered during summer. Direct discharge of coastal wastewater treatment plants contributed an additional 2.1 metric tons year^-1, primarily from domestic sources. Seasonal changes influenced SM partitioning between aqueous and particulate phases, affecting their environmental fate and bioaccumulation potential in estuarine and coastal ecosystems. In addition, the different behavior of HHCB and AHTN during land-to-sea transport, reflected by their shifting ratios and partitioning patterns, highlight the influence of environmental processes such as sorption and photodegradation on SM distribution. These findings provide a scientific basis for managing pollution sources of personal care products in coastal zones.