Internal Loads of Nutrients in Lake Chaohu of China: Implications for lake Eutrophication

This study investigated the impact of internal nitrogen and phosphorus loading on water quality of Lake Chaohu, China. Results showed that the overall mean concentration of TN and TP in lake water was 1.09±0.84 and 0.15±0.84 (SD) mg/L, respectively, indicating Lake Chaohu was highly eutrophic during the study period. Mean benthic flux of NH4+, NO3-, and PO43- were 3.56±1.52 mg N/m2/d, -0.14±0.40 mg N/m2/ d, and -1.54±21.94 µg P/m2/d in summer and were 3.16±1.83 mg N/m2/d, -0.03±0.30 mg N/m2/d, and - 0.11±2.58 µg P/m2/d in fall, respectively. In this study, lake sediments acted as both a source of NH4+ and a sink of PO 4 3-. A scenario was used to understand the role of sediments on lake water quality. Results showed that Lake Chaohu would be eutrophic within a month under the impact of internal NH4+ loading when water was diverted to the lake. This indicates that an integrated project combining both a diversion project and dredging of sediments would be necessary for future lake restoration.