Effect of sampling frequency and streamflow on nutrient source apportionment in subtropical rivers

Area of Science:

• Environmental Science
• Water Resource Management
• Ecology

Background:

• Accurate nutrient load estimation is vital for pollution control but challenged by data limitations and hydrological variability.
• Distinguishing between point-source and non-point-source pollution is critical for effective watershed management.

Purpose of the Study:

• To quantitatively differentiate point-source versus non-point-source contributions to total nitrogen (TN) and total phosphorus (TP) loads in the Pearl River Basin (PRB).
• To assess the impact of monitoring frequency and streamflow variability on nutrient source apportionment accuracy.

Main Methods:

• Utilized a process-based load apportionment model (LAM) integrating daily flow and high-resolution water quality data from 41 monitoring stations.
• Employed statistical T-tests to evaluate the sensitivity of source apportionment to monitoring frequency and streamflow variability.

Main Results:

• Non-point sources accounted for the majority of annual TN (85.95%) and TP (92.13%) loads in the PRB.
• Significant regional variations were observed, with the Beijiang sub-basin showing lower non-point-source TN contributions.
• Monitoring frequency had a greater impact on TN source partitioning than TP.

Conclusions:

• Non-point sources are the dominant nutrient contributors in the PRB, necessitating region-specific management strategies.
• High-frequency monitoring and multi-source data fusion are essential for robust pollution source identification and effective water quality management.