A Proposed Methodology for the Dynamic Standard Evaluation of Water Quality in Estuaries: A Case Study of the Pearl River Estuary

Currently, China's river water quality evaluation adopts the "Environmental Quality Standards for Surface Water", while the seawater quality evaluation uses the "Seawater Quality Standard". However, estuarine areas, where rivers meet the sea, do not have evaluation standards, and most often, the "Seawater Quality Standard" is applied. At present, the water quality in the estuary area sometimes exceeds the corresponding seawater quality standards, even though the quality of the surface water does not exceed surface water environmental quality standards and the quality of the seawater before mixing also meets the seawater quality standards. This paper proposes a dynamic evaluation standard based on the salinity of estuarine water and uses this standard to evaluate the water quality in estuaries, thus solving the abovementioned issue. The implementation of this method is simple and effective. Taking the Pearl River Estuary as an example, this paper introduces the dynamic standard evaluation method for water quality in the Pearl River Estuary. Compared to the existing seawater quality standards implemented in estuaries, this dynamic evaluation standard can assess the water quality in estuaries more accurately and provide a reference for water quality evaluation methods in estuaries.