Key factors influencing sensory quality of scenic waters and its improvement by constructed wetlands

Abstract

Sensory quality is very important for scenic waters. It's necessary to find out the key factors influencing sensory quality of scenic waters and then take corresponding measures to improve it. In this study, transparency, turbidity and surface chroma were chosen as the main sensory quality indexes whose key influencing factors were analyzed by structural equation model (SEM). The results indicated that water's transparency, turbidity and surface chroma were all mainly influenced by suspended solid (SS). Meanwhile, transparency was also influenced by Chlorophyll a (Chl a), pH, dissolved oxygen (DO), particle size and nutrients. Turbidity was influenced by Chl a and particle size as well. To verify this result and improve water's sensory quality, three constructed wetlands (CWs) were set up and operated. CWs could effectively improve the sensory quality of water bodies. When hydraulic retention time (HRT) was 2 days, the water’ transparency increased from 18.00 ± 2.83 cm to about 100 cm, the removal rate of turbidity was 56.26% ∼ 97.11%, and the average removal rate of surface chroma of the three CWs was 72.56%, 70.31% and 63.36%, respectively. To get a better improvement effect, planting and extending HRT were feasible measures. The mechanism analysis showed that removing SS, especially large particles in water was the main reason for improving sensory quality by CWs, followed by removing Chl a. The operational results of CWs proved that SS was certainly the key influencing factor of water's sensory quality.