Shen ¹, Huan-ting, Qing-hui Huang ², Xin-cheng Liu ¹

¹State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China, E-mail: htshen@sklec.ecnu.edu.cn, and ²State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O.BOX 2871, Beijing, 100085, China

Fluxes of the dissolved inorganic nitrogen and phosphorus through the key interfaces in the Changjiang estuary

Fluxes of the dissolved inorganic nitrogen and phosphorus in the delta area of the Changjiang River have been estimated. In 1999, the net export of dissolved inorganic phosphorus (DIP) and dissolved inorganic nitrogen (DIN) from the Changjiang estuary into the East China Sea were 1.26´10⁹ mol/yr and 2.45´10¹¹ mol/yr, respectively.

The Changjiang River (Yangtze) is one of the longest rivers in the world. It loads huge amount of water, sediments, nutrient and other materials discharged into the East China Sea(Shen, 2001). These materials may have large influence on the environment and ecosystem alongshore, and also on the matter cycle in the western Pacific Ocean. In the last half century, the nutrient concentrations and fluxes of the Changjiang River and its estuary have increased greatly (Zhang et al., 1999; Shen, 2001) just like other major estuaries in the world such as Mississippi estuary (Rabalais et al., 1996), Chesapeake Bay (Boynton et al., 1995), Scheldt estuary, Rhine estuary (Van Bennekom & Wetsteijn, 1990) and Humber estuary (Sanders et al., 1997).Thus, it is very important to study the material fluxes, especially the nutrient fluxes, to the sea via the Changjiang estuary.

In the Changjiang estuary, previous works have been done on the nitrogen and phosphorus fluxes from the Changjiang River to its estuary (Shen et al., 1991; Duan et al., 2000; Liu and Shen, 2001). The mean fluxes of dissolved nutrient in the Changjiang estuary were estimated based on field observations (Shen et al., 1991; Zhang et al., 1996). Shen(2001) used equal-area cells methods (Perillo &. Piccolo, 1998) to calculate the nutrient fluxes through two cross-sections in a spring tide and a neap tide in dry season in the South Branch of the Changjiang estuary. However, these results could not represent the nitrogen and phosphorus fluxes from Changjiang estuary to the East China Sea. There was little work on the non-conservative fluxes of nitrogen and phosphorus in the estuary.

Nutrient budget model is a LOICZ strategy to deal with estimating these CNP fluxes for the global coastal zone (Gordon et al., 1996; Smith, 2001). In our previous work, nutrient budgets in the Changjiang estuary had been developed(see LOICZ Nutrient Budgets Website, http://data.ecology.su.se/MNODE/). In this paper, the fluxes through different interfaces and non-conservative fluxes of the dissolved inorganic phosphorus (DIP) and dissolved inorganic nitrogen (DIN) would be estimated based on the budgets.