The critical trigger of 2-methylisoborneol in Taihu Lake: Flow velocity

The dynamics of 2-methylisoborneol (2-MIB), a terpene-derived odorant that compromises drinking water safety worldwide, in drinking water sources are influenced by multiple environmental factors. However, the primary driver triggering its peaks has remained elusive, limiting predictive capability and effective management. This study identifies flow velocity (FV) as the pivotal, threshold-dependent factor strongly associated with 2-MIB, by integrating explainable AI (XAI) with sediment transport physics. Analysis of a 7-year dataset (2015-2021) revealed that 82.7 % of 2-MIB peaks (>302 ng L⁻¹) occur within a critical FV window of 0.118-0.376 m s⁻¹. We demonstrate, for the first time, that these empirically derived thresholds correspond to the critical Shields parameter (θ = 0.036-4.5) for incipient sediment motion, providing a consistent physical mechanism for FV-controlled algal mobilization. Experimental validation confirms three hydrodynamic thresholds: (1) suppression at high FV (>0.376 m s⁻¹; washout), (2) peak production at moderate FV (turbulence-enhanced migration), (3) inhibition at low FV (<0.118 m s⁻¹; light limitation for bottom-dwelling algae). An interpretable multivariate long short-term memory (IMV-LSTM) model captures lagged hydrodynamic impacts and thermal memory, enabling 24-hour forecasts (R² = 0.74). This integration provides a novel strategy for controlling taste-and-odor events through targeted hydraulic management.