Environmental implications of salinity and flooding induced changes in porewater nitrogen and phosphorous dynamics

This study aimed to investigate the effects of fresh water and seawater flooding on phosphorous (P) and nitrogen (N) dynamics in two calcareous soils (Biscayne and Krome) of South Florida using a 28-day greenhouse flooding experiment. Porewater samples were collected at three depths over four periods (1, 7, 14, and 28 days) of flooding and analyzed for selected water quality parameters. Results showed that seawater-flooded Biscayne soil had a 4.4 fold higher porewater soluble reactive phosphorus (SRP) concentration than freshwater. Additionally, porewater SRP concentration and total phosphorus (TP) in Biscayne soil increased with prolonged flooding duration and column depth. Furthermore, both freshwater and seawater flooding increased porewater NH4+ - N concentration; however, the increase was more pronounced in seawater flooded samples. NH4+ - N concentration also increased with flooding duration. Overall, the study highlights the risks of nutrient leaching from seawater flooded coastal soils that could contribute to the deterioration of surface and groundwater quality.