Analysis of nitrogen flow in the Yellow River Basin over a long time series

Abstract

Based on the basic statistical data and related parameters of The Yellow River Basin (YRB) from 2000 to 2019, the nitrogen flow model of the YRB was constructed by using the full nitrogen flow analysis model (FNFA) and the emission coefficient method to analyze the characteristics of the nitrogen inputs and outputs in the YRB. The results revealed that over the past 20 years, both the total nitrogen inputs and outputs in the YRB have shown a significant increasing trend. Specifically, the total nitrogen input rose from 12,806.69 Gg to 18,553.42 Gg, while the total output increased from 9,250.93 Gg to 12,955.0 Gg. Among the various subsystems, the industrial and agricultural sectors were the largest contributors to nitrogen balance, accounting for 28.30% and 26.22% of the total nitrogen input, and 26.22% and 40.48% of the total nitrogen output, respectively. The overall nitrogen utilization efficiency (NUE) across the subsystems required improvement, particularly within the cropland subsystem, which had an NUE ranging from 25.67–36.10%. In contrast, the livestock subsystem exhibited only half the NUE of the cropland subsystem. High emissions and inefficient nitrogen utilization led to a continuous increase in environmental nitrogen loads, with atmospheric nitrogen loads being particularly pronounced. Additionally, the life cycle analysis of industrial nitrogen revealed that a substantial amount of nitrogen was enriched in the atmosphere. These findings can serve as scientific basis and support for regulating nitrogen inflow and outflow within watershed areas, and formulating more rational integrated management strategies for nitrogen.