Eutrophication is caused by excess nutrients in a lake, namely nitrogen and phosphorus. In addition, sunlight and warm temperatures are required for cyanobacteria grow. This study measured nutrient concentrations in Nong Khod Lake, where eutrophication is a serious problem and discuss possible nutrient sources. Twelve samples were collected from six sites on January 23, 2018 and were analyzed for total nitrogen (TN) and total phosphorus (TP) in both surface water and sediment and compared with Thailand's water quality standards. In addition, influence of land use pattern was considered.
Concentrations of TN and TP in the water ranged from 5.7 to 8.8 mg/L and 0.2 to 1.2 mg/L, respectively, while the concentration of TN and TP in sediments ranged from 12.2 to 40.6 mg-N/kg and 1.2 to 7.6 mg-P/kg, respectively. The point was obtained runoff from community area. Where was the highest of TN (8.8±0.2 mg/L), runoff was often worsened by human activities, and could contained nitrogen storm water flows directly into the lake. The point was obtained runoff from agriculture area and that NH4-N concentration was the highest (2.9±0.2mg/L). In contrast, the point was obtained runoff from fresh market area and that cyanobacteria grow, this affected to NO3-N concentration was the highest (0.07±0.0mg/L). Also TN and TP concentration of sediments were the highest (40.6±0.9 mg-N/kg and 7.6±0.7 mg-P/kg,
respectively). This percentage of water content in sediment was 57.8±0.3 that similarly clay. And average of pH was 8.3.
In conclusion, nutrient concentrations of Nong Khod Lake has revealed that related on source. Such as concentration of nitrogen related with runoff from land use pattern while phosphorus even related on sediment. The furfure work, maintain for Nong Khod Lake has been gradually improved. However, we have to survey water quality and sediment about TN and TP.
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