[Estimation of Nitrous Oxide Emission from River System Based on Water Discharge and Dissolved Nitrous Oxide Concentration]

Bing-Qing Li; Min-Peng Hu; Ming-Feng Wang; Yu-Fu Zhang; Hao Wu; Jia Zhou; Kai-Bin Wu; Zhi-Zhou Dai; Ding-Jiang Chen

doi:10.13227/j.hjkx.202105005

[Estimation of Nitrous Oxide Emission from River System Based on Water Discharge and Dissolved Nitrous Oxide Concentration]

Huan Jing Ke Xue. 2022 Jan 8;43(1):369-376. doi: 10.13227/j.hjkx.202105005.

[Article in Chinese]

Authors

Bing-Qing Li^{1

2}, Min-Peng Hu^{1

2}, Ming-Feng Wang^{1

2}, Yu-Fu Zhang^{1

2}, Hao Wu^{1

2}, Jia Zhou^{1

2}, Kai-Bin Wu^{1

2}, Zhi-Zhou Dai^{1

2}, Ding-Jiang Chen^{1

2

3}

Affiliations

¹ College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China.
² Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, Zhejiang University, Hangzhou 310058, China.
³ Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058, China.

PMID: 34989521
DOI: 10.13227/j.hjkx.202105005

Abstract

Due to increasing active nitrogen pollution loads, river systems have become an important source of nitrous oxide (N₂O) in many areas. Due to the lack of monitoring data in many studies as well as the difficulty in estimating intermediate parameters and expressing temporal-spatial variability in current methods, a high level of uncertainty remains in the estimates of riverine N₂O emission quantity. Based on the monthly monitoring efforts conducted for 10 sampling sites across the Yonganxi River system in Zhejiang Province from June 2016 to July 2019, the temporal and spatial dynamics of riverine N₂O dissolved concentrations ρ(N₂O), N₂O fluxes, and their influencing factors were addressed. A multiple regression model was then developed for predicating riverine N₂O emission flux to estimate annual N₂O emission quantity for the entire river system. The results indicated that observed riverine ρ(N₂O) (0.03-2.14 μg·L^-1) and the N₂O fluxes[1.32-82.79 μg·(m²·h)^-1] varied by 1-2 orders of magnitude of temporal-spatial variability. The temporal and spatial variability of ρ(N₂O) were mainly influenced by the concentrations of nitrate, ammonia, and dissolved organic carbon, whereas the N₂O emission fluxes were mainly affected by river water discharges and ρ(N₂O). A multiple regression model that incorporates variables of river water discharge and ρ(N₂O) could explain 90% of the variability in riverine N₂O emission fluxes and has high accuracy. The model estimated N₂O emission quantity from the entire Yonganxi River system of 3.67 t·a^-1, with 29% from the main stream and 71% from the tributaries. The IPCC default emission factor method might greatly overestimate and underestimate N₂O emission quantities for rivers impacted by low and high pressures of human activities, respectively. This study advances our quantitative understanding of N₂O emission for the entire river system and provides a reference method for estimating riverine N₂O emission with more accuracy.

Keywords: dissolved concentration; emission flux; model; nitrous oxide; river.

MeSH terms

Dissolved Organic Matter
Environmental Monitoring
Humans
Nitrous Oxide* / analysis
Rivers*
Water

Substances

Dissolved Organic Matter
Water
Nitrous Oxide