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Dual isotope measurements reveal zoning of nitrate processing in the summer Changjiang (Yangtze) River plume

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posted on 2023-05-19, 17:54 authored by Yan, X, Xu, MN, Wan, XS, Yang, JYT, Trull, TW, Dai, M, Kao, SJ
Riverine nitrogen input into the coastal zone has increased remarkably in recent decades. Yet its transformation and recycling within hydrodynamically active regions remains unclear. Using observations of nitrate concentration and dual isotopic composition across the Changjiang River plume within a three end-member mixing model, we found deviations between the observed and expected values for mixing alone, revealing the nonconservative behavior of nitrate. Using cross correlations between concentrations and dual isotope deviations, we identified three nitrogen transformation zones, which correspond to separate portions of the plume. Nitrification and sedimentary denitrification occurred near the river mouth, nitrification prevailed further offshore under the plume, and finally, phytoplankton assimilation occurred in the outer surface plume (>100 km offshore), where it was fueled by nitrate that had already been strongly modified by microbial processes. Information was assembled into a conceptual model offering an overview of nitrogen transformations in a large river plume.

History

Publication title

Geophysical Research Letters

Volume

44

Issue

24

Pagination

12,289-12,297

ISSN

0094-8276

Department/School

Institute for Marine and Antarctic Studies

Publisher

Amer Geophysical Union

Place of publication

2000 Florida Ave Nw, Washington, USA, Dc, 20009

Rights statement

Copyright 2017 American Geophysical Union

Repository Status

  • Open

Socio-economic Objectives

Measurement and assessment of marine water quality and condition

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