Trends in nutrients in the Changjiang River

Wentao Wu; Junjie Wang; Hao Wang; Jun Liu; Qingzhen Yao; Zhigang Yu; Xiangbin Ran

doi:10.1016/j.scitotenv.2023.162268

Trends in nutrients in the Changjiang River

Sci Total Environ. 2023 May 10:872:162268. doi: 10.1016/j.scitotenv.2023.162268. Epub 2023 Feb 16.

Authors

Wentao Wu¹, Junjie Wang², Hao Wang³, Jun Liu⁴, Qingzhen Yao⁵, Zhigang Yu⁵, Xiangbin Ran⁶

Affiliations

¹ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, PR China; Research Center for Marine Ecology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, PR China.
² Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, the Netherlands.
³ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, PR China; Research Center for Marine Ecology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, PR China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, PR China; Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, the Netherlands.
⁴ Research Center for Marine Ecology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, PR China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, PR China.
⁵ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, PR China.
⁶ Research Center for Marine Ecology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, PR China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, PR China. Electronic address: rxb@fio.org.cn.

PMID: 36801333
DOI: 10.1016/j.scitotenv.2023.162268

Abstract

Better documentation and understanding of long-term temporal dynamics of nutrients in watersheds are necessary to support effective water quality management. We examined the hypothesis that the recent management of fertilizer use and pollution control in the Changjiang River Basin could govern the fluxes of nutrients from the river to the sea. Results based on historical data since 1962 and surveys in recent years show that concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) in the mid- and downstream reaches were higher than those in the upper reaches due to intensive anthropogenic activities, while dissolved silicate (DSi) was distributed evenly from the up- to downstream reaches. Fluxes of DIN and DIP increased rapidly, and DSi declined during the 1962-1980 and 1980-2000. After the 2000s, concentrations and fluxes of DIN and DSi remained almost unchanged; those of DIP remained stable until the 2010s and slightly decreased afterward. The decline in fertilizer use explains 45 % of the variance in the decline of DIP flux, followed by pollution control, groundwater and water discharge. As a result, the molar ratio of DIN:DIP, DSi:DIP and ammonia:nitrate varied largely during 1962-2020, and the excess DIN relative to DIP and DSi lead to increased limitations of silicon and phosphorus. A turning point probably occurred for nutrient fluxes in the Changjiang River in the 2010s, with the pattern of DIN from continuous increase to stability and DIP from increase to decrease. This decline in phosphorus in the Changjiang River has many similarities with the rivers worldwide. The continued basin nutrient management is likely to have a major influence on river nutrient delivery and therefore may control coastal nutrient budget and ecosystem stability.

Keywords: Changjiang River; Nutrients; Policy control; Spatiotemporal changes; Stoichiometric ratios.