Submarine Groundwater Discharge and Dependent Nutrient Input Based on a Series of Layered Monitoring Wells

Abstract:

The submarine groundwater of a series of stratified vertical wells near the coast of Beihai， Guangxi was monitored and analyzed on-site. The monitoring and sampling analysis show that the salinity in the groundwater in Confined I which is close to the seaside is relatively high， and the difference in salinity is mainly affected by seawater intrusion and high-level mariculture. The concentration of SiO₃-Si in groundwater increases from inland to coastal area due to the “salt effect”， and the low content of PO₄-P which may have been caused by the adsorption and removal of iron oxides. The NH₄-N and NO_x-N concentrations in the phreatic layer are higher than those in confined water. The infiltration of high-level aquaculture pond water results in the highest NH₄-N concentration in the nearshore phreatic layer， while NO_x-N is affected by denitrification. The average N / P ratio of groundwater in the studied area is 595.85， and the discharge of groundwater with a high N / P ratio into the ocean will promote the transformation of nutrient structure of plankton from N limitation to P limitation.

Key words:Beihai;submarine groundwater discharge;nutrients;seawater intrusion;N / P ratio