Abstract: To comprehensively monitor and analyze the distribution of chloride concentrations in river water as well as to understand its effect on environmental quality monitoring in Dongying, the chloride concentrations in 38 river sections of Dongying were continuously monitored in 2018. The results showed that the monthly chloride concentrations in six sections were less than 1000 mg/L, twenty sections’ concentrations were in the range of 1000~2000 mg/L, six sections’ concentrations in the range of 2000~3000 mg/L and the remaining six sections’ concentrations above 3000 mg/L. This indicates that the river water of Dongying has high chlorion content; the concentration of chlorion also greatly varied with the location of the sections (upstream or downstream) and the time of sampling. Chloride can cause positive interference to certain monitoring items or lead to the inapplicability of certain monitoring methods, especially for COD, ammonia nitrogen, permanganate index and other items. Therefore, the influence of chlorion on environmental quality analysis must be carefully considered, and a series of measures must be taken to eliminate the influence of chloride during water quality monitoring for the rivers of Dongying.

Key words: river water, chloride concentration, environmental quality, Dongying City