{Reference Type}: Journal Article
{Title}: Deciphering and quantifying nitrate sources and processes in the central Yellow Sea using dual isotopes of nitrate.
{Author}: Zhong X;Ran X;
{Journal}: Water Res
{Volume}: 261
{Issue}: 0
{Year}: 2024 Sep 1
{Factor}: 13.4
{DOI}: 10.1016/j.watres.2024.121995
{Abstract}: Anthropogenic activities pose significant challenges to the accumulation of coastal nitrogen (N). Accurate identification of nitrate (NO3-) sources is thus essential for mitigating excessive N in many marginal seas. We investigated the dual isotopes of NO3- in the central Yellow Sea to elucidate the sources and cycling processes of NO3-. The results revealed significant spatial variability in NO3- concentrations among the Yellow Sea Surface Water (YSSW), Changjiang Diluted Water (CDW), Yellow Sea Cold Water Mass (YSCWM), and Taiwan Warm Current Water (TWCW). Stratification played a crucial role in restricting vertical nutrient transport, leading to distinct nutrient sources and concentrations in different water masses. The dual NO3- isotopic signature indicated that atmospheric deposition was the primary source of surface NO3-, contributing approximately 30 % to the NO3- in the YSSW. In the NO3--rich CDW, the heavier δ15N-NO3- and δ18O-NO3- suggested incomplete NO3- assimilation. Organic matter mineralization and water stratification played crucial roles in the accumulation of nutrients within the YSCWM and TWCW. Notably, regenerated NO3- accounted for approximately half of the NO3- stored in the YSCWM. A synthesis of NO3- dual isotope data across the coastal China seas revealed significant spatial and seasonal variations in the N source. The study emphasized the dynamics of coastal NO3- supply, which are shaped by the complex interconnections among marine, terrestrial, and atmospheric processes. Our approach is a feasible method for exploring the origins of N amidst the escalating pressures of anthropogenic nutrient pollution in coastal waters.