Relative effects of wind-induced disturbances and vegetation on tetrabromobisphenol A cycling in shallow lakes: Direct and indirect effects

The environmental concerns regarding the possible threats of tetrabromobisphenol A (TBBPA) to aquatic environments are increasing. However, information about TBBPA cycling in the water-vegetation-sediment systems of shallow lakes is limited. In a shallow lake, wind-induced disturbance is considered as the key factor of affecting the cycling of contaminants. To address this issue, the TBBPA distribution and elimination processes were simulated for three typical wind speeds by using an annular flume. Four forms of TBBPA were studied in these systems, including water, suspended solids (SS), vegetation and sediment. The results showed that the mass distributions of TBBPA in water, SS and vegetation increased remarkably while enhancing the wind-induced disturbances, which resulted from the release of TBBPA from the sediment through resuspension and adsorption-desorption processes. However, most of the TBBPA (up to 94%) still accumulated in the sediment. Wind-induced disturbances and vegetation both increased the TBBPA elimination rate in the water-vegetation-sediment systems. The half-life (T₁/₂) of TBBPA in the fast wind condition was 16.1 ± 0.2 days, which was shorter than that in the static condition (29.8 ± 0.9 days). Compared to the systems without vegetation, the presence of vegetation shortened the T₁/₂ by 7.3 days in the static condition. Furthermore, a structural equation model (SEM) was used to assess the direct and indirect effects of environmental factors on the TBBPA amounts in each form. The main effects of wind speed and vegetation in the TBBPA cycling of each form (except for the TBBPA on vegetation) were indirect by affecting the dissolved oxygen (DO), velocity and suspended solids concentration (SSC). Overall, the findings provide useful information about the fate of TBBPA and other related organic contaminants in shallow lake systems.