Coastal reservoirs as a source of nitrous oxide: Spatio-temporal patterns and assessment strategy

Ping Yang; Miaohui Lu; Kam W Tang; Hong Yang; Derrick Y F Lai; Chuan Tong; Kwok Pan Chun; Linhai Zhang; Chen Tang

doi:10.1016/j.scitotenv.2021.147878

Coastal reservoirs as a source of nitrous oxide: Spatio-temporal patterns and assessment strategy

Sci Total Environ. 2021 Oct 10:790:147878. doi: 10.1016/j.scitotenv.2021.147878. Epub 2021 May 21.

Authors

Ping Yang¹, Miaohui Lu¹, Kam W Tang², Hong Yang³, Derrick Y F Lai⁴, Chuan Tong⁵, Kwok Pan Chun⁶, Linhai Zhang¹, Chen Tang⁷

Affiliations

¹ Key Laboratory of Humid Subtropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China; School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China.
² Department of Biosciences, Swansea University, Swansea SA2 8PP, UK.
³ College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control (AEMPC), School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, 219 Ningliu Road, Nanjing 210044, China; Department of Geography and Environmental Science, University of Reading, Reading RG6 6AB, UK.
⁴ Department of Geography and Resource Management, The Chinese University of Hong Kong, Hong Kong, China.
⁵ Key Laboratory of Humid Subtropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007, China; School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China. Electronic address: tongch@fjnu.edu.cn.
⁶ Department of Geography, Hong Kong Baptist University, Hong Kong, China.
⁷ School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China.

PMID: 34090167
DOI: 10.1016/j.scitotenv.2021.147878

Abstract

Coastal reservoirs are widely regarded as a viable solution to the water scarcity problem faced by coastal cities with growing populations. As a result of the accumulation of anthropogenic wastes and the alteration of hydroecological processes, these reservoirs may also become the emission hotspots of nitrous oxide (N₂O). Hitherto, accurate global assessment of N₂O emission suffers from the scarcity and low spatio-temporal resolution of field data, especially from small coastal reservoirs with high spatial heterogeneity and multiple water sources. In this study, we measured the surface water N₂O concentrations and emissions at a high spatial resolution across three seasons in a subtropical coastal reservoir in southeastern China, which was hydrochemically highly heterogeneous because of the combined influence of river runoff, aquacultural discharge, industrial discharge and municipal sewage. Both N₂O concentration and emission exhibited strong spatio-temporal variations, which were correlated with nitrogen loading from the river and wastewater discharge. The mean N₂O concentration and emission were found to be significantly higher in the summer than in spring and autumn. The results of redundancy analysis showed that NH₄⁺-N explained the greatest variance in N₂O emission, which implied that nitrification was the main microbial pathway for N₂O production in spite of the potentially increasing importance of denitrification of NO₃^--N in the summer. The mean N₂O emission across the whole reservoir was 107 μg m^-2 h^-1, which was more than an order of magnitude higher than that from global lakes and reservoirs. Based on our results of Monte Carlo simulations, a minimum of 15 sampling points per km² would be needed to produce representative and reliable N₂O estimates in such a spatially heterogeneous aquatic system. Overall, coastal reservoirs could play an increasingly important role in future climate change via their N₂O emission to the atmosphere as water demand and anthropogenic pressure continue to rise.

Keywords: Coastal reservoir; Greenhouse gases; Nitrous oxide; Spatial heterogeneity; Wastewater discharge; Water management.

MeSH terms

Atmosphere
Nitrification
Nitrogen
Nitrous Oxide*
Rivers*

Substances

Nitrous Oxide
Nitrogen