Evaluation of Water Quality of a Blue Lake at An Son Commune, Thuy Nguyen District, Hai Phong City by Water Quality Index (WQI), Trophic State Index (TSI) and Heavy Metal Pollution Index (HPI)

Abstract

A blue lake in An Son Commune, Thuy Nguyen District, Hai Phong City has been recently discovered to have a beautifully blue color. There is an urgent need to answer the question whether the water is safe or not for using. Therefore, this research evaluated the lake water quality by combining 3 indices, Water Quality Index (WQI), Trophic State Index (TSI), and Heavy Metal Pollution Index (HPI). The results showed that WQI = 1 with pH = 10.21 indicating that the lake water is heavily polluted. It is not safe to use for B1 and B2 purposes of QCVN 08-MT:2015. TSI was 28,9, showing that this lake was oligotrophic. This result was confirmed by very low ammonium and phosphate concentrations of <0,02 mg/l and <0,05 mg/l, respectively. The lake was not polluted by heavy metals with HPI = 3,89. The reasons of high pH value and the deep blue color of the lake were also primarily studied in this research.