Spatial and seasonal patterns of dissolved organic matter hydrophobicity in Lake Taihu revealed by the aqueous two-phase system

Abstract

The hydrophobicity of dissolved organic matter (DOM) is a key property influencing the environmental risks of organic pollutants. Our understanding of the spatial and seasonal pattern of DOM hydrophobicity in aquatic systems and the major controlling factors is still limited. In this study, the hydrophobicity of 124 DOM samples collected from northern Lake Taihu, a typical eutrophic lake, was quantified using the partition coefficient of DOM in the aqueous two-phase system (KATPS). The results revealed high-resolution spatial patterns and seasonal variations of DOM hydrophobicity in Lake Taihu. The riverine input, algae activity, and photodegradation were identified as important processes shaping the spatial and seasonal pattern of DOM hydrophobicity. The riverine input and algae activity strongly affected DOM hydrophobicity in the west part and the central area of the lake. Photodegradation process played a significant role in DOM hydrophobicity in the east part of the lake in summer. The high-resolution spatial and seasonal pattern of the hydrophobic organic pollutant partition affinity of DOM (KOC) was assessed based on the two-phase system model and the KATPS dataset. The KOC values vary significantly in Lake Taihu between spring and summer, especially in the Zhushan Bay and east coast areas, highlighting the need for considering DOM dynamics in sorption assessment. Our results detailly profiled the spatial and seasonal patterns of DOM hydrophobicity and sorption behavior and elucidated the major controlling factors, which is crucial for environmental risk assessment.