Dynamics of Nutrient Elements in Three Estuaries of North China: The Luanhe, Shuangtaizihe, and Yalujiang

摘要: Concentrations of nutrients (NO3 −, NO2 NH4 +, PO4 3−, and dissolved SiO2) were examined in three North China estuaries—the Luanhe, Shuangtaizihe, Yalujiang. These riverine-estuarine systems provide distinct geographic hydrodynamic conditions, that is, a shallow water zone embraced by shoals sandbars (Luanhe), the confluence two streams upper estuary with different sediment loads, turbidity maximum estuarine mixing (Yalujiang). Nutrient element concentrations these rivers are high comparison large, less disturbed but similar to those from polluted and/or eutrophic European American rivers. This is attributed intensive weathering erosion extensive use chemical fertilizers. In fresh-marine waters zone, nutrient species can behave either conservatively or nonconservatively, both. Wherever nonconservative behaviours elements observed, remobilization solid phases probably predominant mechanism. The extrapolation dilution curves fresh end-members gives estimated riverine concentrations, which be between ten times higher than field observations. Taking into account N:P ratios (102–104) very low nitrogen Northwest Pacific coastal oceans (e.g., Yellow Sea), estuaries this study may act as regions production limited phosphorus nitrogen.