| Title: | Source apportionment of nutrient loads to a Mediterranean river and potential mitigation measures |
| Authors: | De Girolamo, A.M. and A. Lo Porto |
| Year: | 2020 |
| Journal: | Water |
| Volume (Issue): | 12 |
| Pages: | 577 |
| Article ID: | |
| DOI: | 10.3390/w12020577 |
| URL (non-DOI journals): | |
| Model: | SWAT |
| Broad Application Category: | hydrologic and pollutant |
| Primary Application Category: | BMP and/or cropping system assessment |
| Secondary Application Category: | nitrogen cycling/loss and transport |
| Watershed Description: | 488 km^2 Rio Mannu River, located in southern Sardinia in western Italy. |
| Calibration Summary: | |
| Validation Summary: | |
| General Comments: | |
| Abstract: | The aims of the study were to quantify nutrient loads from point and diffuse pollution
sources in the Rio Mannu stream and to simulate mitigation measures for reducing nutrient loads
delivered to the Santa Gilla wetland. The Soil and Water Assessment Tool model was used for
simulating hydrology, nutrient balance and water quality. At the basin scale, the input from
fertilisers was 80.3 kg ha−1 year−1 total nitrogen (TN) (87.6% of the total input) and 27.6 kg ha−1 year−1
of total phosphorus (TP) (99.8% of the total input). Atmospheric deposition and biological N‐fixation
together accounted for about 12% of the total TN input. The TN and TP from wastewater treatment
plants (WWTPs) were about 14.2 t year−1 and 3.1 t year−1, respectively. Nutrient loads delivered to
the river system differed among the sub‐basins, with TP ranging from 0.2 kg ha−1 year−1 to 2.7 kg
ha−1 year−1, and the sum of organic N and NO3‐N ranging from 1.8 kg ha−1 year−1 to 22.9 kg ha−1 year−1.
Under high flow conditions, NO3‐N and TP accounted for 89% and 99% of the total load,
respectively. The low flow contribution to the total load was very low, with NO3‐N and TP
accounting for 2.8% and 0.7%, respectively. However, the natural hydrological regime in the study
area is intermittent, and low flow represents a critical condition for the water quality due to the high
concentrations of TP and NO3‐N from WWTP discharge. To improve the water quality, the reuse of
treated wastewater from three WWTPs for irrigation purposes on olive cultivation, coupled with a
20% reduction in fertiliser application, was simulated. The results showed a reduction in nutrient
loads at the outlet for all hydrological conditions. However, additional measures are needed for
improving water quality. |
| Language: | English |
| Keywords: | point and non‐point source pollution; Mediterranean basin; temporary river; wastewater reuse; mitigation measures |