Environ Monit Assess. 2025 Nov 27;197(12):1377. doi: 10.1007/s10661-025-14827-4.
ABSTRACT
Concern over agricultural nutrient contamination is rising in arid Central Asia where a shortage of freshwater resources under climate change exacerbates water supply problems. This study assesses how nutrient loading in the Zarafshan River Basin is affected by the application of nitrogen, phosphorus, and potassium (NPK) fertilizers. We evaluated fertilizer use and river nutrient concentrations using QSWAT hydrological modeling, GIS-based spatial analysis, and long-term water quality data. The model was calibrated and validated for discharge using SWAT-CUP on a monthly time step. The model results were evaluated using the R2 and NSE statistical coefficients, which were 0.78 and 0.76 during the calibration period, and 0.75 and 0.73 during the validation period, respectively, which proved the model’s accuracy. While P and K correlations were weak and not statistically significant, N fertilizer application demonstrated a statistically significant, moderate positive correlation with TNmin (mineral total nitrogen) in river water (ρ = 0.30, p < 0.05). For nutrient export, 37.1% of the basin was in high-risk zones. Modeled monthly averages for the upstream and downstream nitrogen (NO3) loads were 598 kg and 60,318 kg/month per subbasin, respectively. These results highlight nitrogen, in contrast to phosphorus and potassium, as one of the dominant contributors to non-point source pollution, demanding targeted nutrient management in agricultural zones.
PMID:41299005 | DOI:10.1007/s10661-025-14827-4
