Diel and seasonal nitrous oxide fluxes determined by floating chamber and gas transfer equation methods in agricultural irrigation watersheds in southeast China

• Published in: Environmental monitoring and assessment 2018-03, Vol.190 (3), p.122-14, Article 122
• Main Authors: Wu, Shuang, Chen, Jie, Li, Chen, Kong, Delei, Yu, Kai, Liu, Shuwei, Zou, Jianwen
• Format: Article
• Language: English
• Subjects: Agricultural Irrigation; Agricultural practices; Agricultural runoff; Agricultural watersheds; Agriculture - methods; Air Pollutants - analysis; Annual cycles; Atmospheric Protection/Air Quality Control/Air Pollution; China; Cycles; Diel variations; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental Management; Environmental monitoring; Environmental Monitoring - methods; Environmental science; Floating; Fluctuations; Fluxes; Gas exchange; Heavy rainfall; Irrigation; Leaching; Marine environment; Mathematical models; Measurement; Measurement methods; Models, Chemical; Monitoring/Environmental Analysis; Nitrates - chemistry; Nitrogen - analysis; Nitrous oxide; Nitrous Oxide - analysis; Rain; Rainfall; Regional analysis; Runoff; Sampling; Seasons; Soil - chemistry; Variation; Watersheds
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-018-6502-0

Agricultural nitrate leaching and runoff incurs high nitrogen loads in agricultural irrigation watersheds, constituting one of important sources of atmospheric nitrous oxide (N 2 O). Two independent sampling campaigns of N 2 O flux measurement over diel cycles and N 2 O flux measurements once a week over annual cycles were carried out in an agricultural irrigation watershed in southeast China using floating chamber (chamber-based) and gas transfer equation (model-based) methods. The diel and seasonal patterns of N 2 O fluxes did not differ between the two measurement methods. The diel variation in N 2 O fluxes was characterized by the pattern that N 2 O fluxes were greater during nighttime than daytime periods with a single flux peak at midnight. The diel variation in N 2 O fluxes was closely associated with water environment and chemistry. The time interval of 9:00–11:00 a.m. was identified to be the sampling time best representing daily N 2 O flux measurements in agricultural irrigation watersheds. Seasonal N 2 O fluxes showed large variation, with some flux peaks corresponding to agricultural irrigation and drainage episodes and heavy rainfall during the crop-growing period of May to November. On average, N 2 O fluxes calculated by model-based methods were 27% lower than those determined by the chamber-based techniques over diel or annual cycles. Overall, more measurement campaigns are highly needed to assess regional agricultural N 2 O budget with low uncertainties.