Nitrogen cycling in aquatic environments of China: Progress and future challenges

Abstract

Aquatic environments are hot spots of nitrogen (N) cycling and nitrous oxide (N2O) emission. Understanding key N biogeochemical processes and N2O dynamics is critical for uncovering the responses of aquatic environments to human activities. In this study, we summarized the development of techniques and approaches for determination of N cycling processes and N2O sources in aquatic environments of China. We also reviewed the main N transformation processes and associated biogeochemical controls in aquatic environments of China (e.g., constructed wetlands, paddy fields, lakes, rivers, aquaculture ponds, and estuaries and coasts). In addition, we further synthesized N2O dynamics in these aquatic environments. The results suggested that N cycling processes have been greatly concerned in various aquatic environments of China, whereas more comprehensive analyses of N cycling processes are still sparse for projecting N fates and dynamics in response to changing environments, largely limiting the implementation of N management strategy of China. Aquatic environments of China may be the important sources of atmospheric N2O, but the production and consumption processes of N2O need to be further studied for effective greenhouse gas mitigation. We also argued that it is urgently necessary to incorporate microbial traits into biogeochemical ecosystem modeling to improve the estimation reliability of N cycling and N2O dynamics. This review highlights the importance of N cycling and N2O dynamics, as well as associated environmental implications, and presents the directions of future research on N cycling in aquatic environments of China.

Progress of physical geography in China: Toward elements correlated, processes coupled, and spatial integrated research

“…Understanding key N biogeochemical processes and N 2 O dynamics is critical for uncovering the responses of China’s aquatic environments to human activities. Hou et al (2022) found that the response of N transformations to oxygen level was not completely consistent and was affected by substrate availability among different aquatic ecosystems; and the biogeochemical processes and microbial activities of sediment in a unit volume might be higher than those of the water body, but the total volume of the water column in aquatic environments was larger than that of sediment with intensively biogeochemical processes. The research frontier is gaining interdisciplinary modeling efforts by incorporating biogeochemical processes and microbial data to understand the N cycle and related environmental implications in China’s diverse aquatic environments.…”