Diagnosis of odor issues in water and sediments of a shallow water reservoir: odor fingerprints, odor-causing algae and microbial communities

Determining the key causative odorants and their origins is crucial for addressing the prevalent odor issues in reservoir water sources, while the relation between odorants present in water and sediments to the whole odor formation in shallow reservoirs (with half of the reservoir area being shallower than 5 m) has been rarely assessed. This study aimed to assess the odor characteristics of the water and sediments in the QY Reservoir, a critical water source in a southern city of China. Key odorants were identified, and their potential sources were evaluated using a 100 odorant fingerprint database, algal cell counting and 16S rRNA gene sequencing. The results revealed that musty/earthy and fishy/septic odors were the main concerns. 2-Methylisoborneol (2-MIB) was the primary contributor to the musty/earthy odor in water samples and was detected at relatively higher average concentrations in water samples at near-shore sites, including S1, S3, S5, S6, and S11. The presence of 2-MIB in sediments was mainly attributed to the deposition of odor-producing algae, including Planktothrix and Pseudanabaena. Additionally, thioethers were found to be the primary contributors to septic odors, which are typically found at higher concentrations in sediments than in water. Sedimentary transformation of sulfur-containing substances was an important source of thioethers in the reservoir. This study provides valuable data and insights for future odor management in shallow water reservoirs affected by complex odor issues.