Study on the diurnal variation characteristics of water transparency and suspended solids in winter for an urban landscape lake in Jiaxing

In November 2023, a 24-hour study was conducted on the dynamic changes in water transparency and suspended solids in Nanhu Lake, a typical urban landscape lake in the plain river network region during winter. The results indicated that in November, Nanhu Lake had an average water depth of 2.98 meters and an average water transparency of 44.48 cm, with a mean water temperature of 15.69°C. Turbidity values ranged from 20.35 to 54.51NTU, with an average of 33.62 NTU. The average values for DO, EC, ORP, and TDS were 9.57 mg/L, 450.89 mV, 157.04 mV, and 225.31 mg/L, respectively, with no significant differences in major water quality indicators across different regions. The 24-hour water transparency variation and patterns at the three sampling stations in Nanhu Lake showed considerable differences, influenced by various factors. Transparency was lowest during the daytime from 06:30 to 18:30, with relatively higher suspended solids content. The content of suspended solids ranged from 13.40 to 39.20 mg/L, with an average of 26.04 mg/L, showing significant variation across different regions. Sampling station one was notably affected by disturbances from docked boats. In terms of composition, inorganic and organic suspended solids accounted for 83% and 17%, respectively, with inorganic particles being predominant. The median particle size of suspended solids in Nanhu Lake ranged from 4.77 to 7.83 μm, with an average size of 6.15 μm. The particle size distribution was 75% for particles ⪅10 μm, 18% for particles between 10-20 μm, and 7% for particles ⪆20 μm. The suspended particles in the surface water of Nanhu Lake were finer than those in the bottom layer, making them more difficult to settle naturally once resuspended.