Nutrient Dynamic And Exchange Characteristics On The Suspended-water Interface In Estuary

Licun River is a typical polluted river flow through city, the estuary of which locatedin east of Jiaozhou Bay. From1990s, urbanization of areas on both sides of the riverdevelops dramatically. After a long period of sewage discharge, the estuary was indeep pollution. Because it is under dual influences by tides and runoff and itsgeographical position of sea land transitional zone is very special, the estuary is madeas the research region.This paper studied the dynamic changes characteristics of N/P nutrients during tidalcycle and the sorption-desorption behavior on suspended-water interface. Accordingto the characteristics of the study area, field projects and lab experiments werecombined to discuss the effects of salinity, temperature, waves strength, suspendedsolids concentration on the sorption-desorption kinetics. The main conclusions are asfollows:①The vertical migrations and changes of PO₄^3--P, NO₂^--N, NH₄⁺-N are complicated,and there is no clear stratification phenomenon. NO₃^--N presented a low on highstratification phenomenon in the vertical direction. The sediment act as a source toPO₄^3--P, NO₂^--N, NH₄⁺-N in overlying water while a sink to NO₃^--N.②The concentration of PO₄^3--P、NO₂^--N、NH₄⁺-N increased sharply in the beginningof high tide and ebb tide while in the flat boom period it is in a low level. Thedynamic characteristics during a tidal of NO₃^--N is opposite. All the concentrations ofthe nutrients had a larger fluctuation in middle of the river than in the both sides.③PO₄^3--P sorption/desorption kinetics process can be divided into3phases：fastsorption/desorption stage, slow sorption/desorption stage, balance stage. NH₄⁺-N/ NO₃^--N desorption kinetics processes can be divided into3phases: fast desorptionstage, sorption stage, balance stage.④High temperature can promote both sorption and desorption of PO₄^3--P on thesuspended-water interface. The influences of temperature on the sorption ofNH₄⁺-N/NO₃^--N is far more than desorption.⑤Increased salinity improved the ionic strength of the overlying water, promoted theion exchange act and increased the number of competition ion, so it had a positiveinfluence on PO₄^3--P/NH₄⁺-N/NO₃^--N moving into water phase.⑥The concentration of PO₄^3--P/NH₄⁺-N in the overlying water would increasefollowing the suspended concentration, but when the suspended in the water inunusual high, the sorption effect strengthening, so the concentration of PO₄^3--P/NH₄⁺-N will reduce.