[Research on land use structure optimization based on nonpoint source dissolved nitrogen load estimation in Shuaishui...

Area of Science:

• Environmental Science
• Hydrology
• Agricultural Science

Background:

• Nonpoint source pollution, particularly dissolved nitrogen (DN), poses a significant threat to watershed health.
• Accurate estimation and source apportionment of DN are crucial for effective water resource management.

Purpose of the Study:

• To estimate dissolved nitrogen (DN) load and perform source apportionment in the Shuaishui watershed using the Regional Nutrient Management (ReNuMa) model.
• To analyze the impact of different land uses on DN load intensity.
• To explore land use structure optimization for reducing pollutant loads while maximizing agricultural output.

Main Methods:

• Application of the Regional Nutrient Management (ReNuMa) model for streamflow and DN estimation.
• Calibration and validation of the model using E(ns) and R2 metrics (>0.9).
• Analysis of DN load intensity across various land use types (paddy field, forest, agricultural land).

Main Results:

• The ReNuMa model demonstrated satisfactory performance in streamflow and DN estimation.
• The average nonpoint DN load was 1.11 x 10(3) t x a(-1) with an intensity of 0.75 +/- 0.22 t x km(-2).
• Paddy fields exhibited the highest DN load intensity (28.60 kg x hm(-2) x a(-1)), while forests had the lowest (2.71 kg x hm(-2) x a(-1)).
• Agricultural land was identified as the dominant contributor to nonpoint DN pollution.

Conclusions:

• Human-dominated agricultural activities are the primary drivers of nonpoint source pollution in the Shuaishui watershed.
• Land use optimization can lead to agricultural monetary growth alongside an increase in DN load, provided the output increment surpasses the load increase.
• Integrated watershed management strategies focusing on agricultural practices are essential for mitigating DN pollution.