Photodegradation of organic micropollutants in aquatic environment: Importance, factors and processes.

Photochemical reactions widely occur in the aquatic environment and play fundamental roles in aquatic ecosystems. In particular, solar-induced photodegradation is efficient for many organic micropollutants (OMPs), especially those that cannot undergo hydrolysis or biodegradation, and thus can mitigate chemical pollution. Recent reports indicate that photodegradation may play a more important role than biodegradation in many OMP transformations in the aquatic environment. Photodegradation can be influenced by the water matrix such as pH, inorganic ions, and dissolved organic matter (DOM). The effect of the water matrix such as DOM on photodegradation is complex, and new insights concerning the disparate effects of DOM have recently been reported. In addition, the photodegradation process is also influenced by physical factors such as latitude, water depth, and temporal variations in sunlight as these factors determine the light conditions. However, it remains challenging to gain an overview of the importance of photodegradation in the aquatic environment because the reactions involved are diverse and complex. Therefore, this review provides a concise summary of the importance of photodegradation and the major processes related to the photodegradation of OMPs, with particular attention given to recent progress on the major reactions of DOM. In addition, major knowledge gaps in this field of environmental photochemistry are highlighted.

Sediment dynamics in a large shallow lake characterized by seasonal flood pulse in Southeast Asia.

Most of studies on sediment dynamics in stable shallow lakes focused on the resuspension process as it is the dominant process. However, understanding of sediment dynamics in a shallow lake influenced by flood pulse is unclear. We tested a hypothesis that floodplain vegetation plays as a significant role in lessening the intensity of resuspension process in a shallow lake characterized by the flood pulse system. Therefore, this study aimed to investigate sediment dynamics in this type of shallow lake. The target was Tonle Sap Lake (TSL), which is a large shallow lake influenced by a flood pulse system of Mekong River located in Southeast Asia. An extensive and seasonal sampling survey was conducted to measure total suspended solid (TSS) concentrations, sedimentation and resuspension rates in TSL and its 4 floodplain areas. The study revealed that sedimentation process was dominant (TSS ranged: 3-126mgL-1) in the high water period (September-December) while resuspension process was dominant (TSS ranged: 4-652mgL-1) only in the low water period (March-June). In addition, floodplain vegetation reduced the resuspension of sediment (up to 26.3%) in water. The implication of the study showed that resuspension is a seasonally dominant process in shallow lake influenced by the flood pulse system at least for the case of TSL.