Assessing Pollutant Interception Efficiency of Eco-Revetments With Sediment Interception Measures, Using an Empirical Method

Eco-revetments serve as essential infrastructure for intercepting agricultural non-point source pollution (ANSP), yet standardised and quantitative evaluation methods remain limited, especially in China where design practices often rely on qualitative experience rather than systematic assessment. This study proposes an empirical method to evaluate the pollutant interception efficiency of eco-revetments equipped with sediment interception measures, based on a design project along the Jinjingtang River in Changshu City, Jiangsu Province. The pollutant removal mechanisms operate via sediment capture in interception ditches, filtration by vegetation, and absorption within sand–gravel media. To enable systematic assessment of pollutant removal efficiency, four formulas were developed to simulate the concentration–time dynamics of key pollutants, including total nitrogen (TN), total phosphorus (TP), and suspended solids (SS), during rainfall events. Additionally, pollutant interception efficiency for both soluble and particulate pollutants, along with flow diversion ratios across different functional modules of the eco-revetment, were defined to support comprehensive evaluation. The empirical method was applied alongside field data on farmland pollution and artificial rainfall experiments to quantitatively assess the eco-revetment's performance of the designed eco-revetment in the Jinjingtang River case study. Results showed that pollutant concentrations decreased continuously over the rainfall event, with the most pronounced reductions occurring within the initial 2 h, emphasising the critical role of early-stage interception. Soil analyses revealed average TP and TN concentrations of 719 and 1256 mg/kg, respectively, with over 90% of these pollutants bound to soil particles, highlighting the importance of sediment control via interception ditches. The assessment demonstrated interception efficiencies of 73.4%, 90.6%, and 99.0% for TN, TP, and SS, respectively, with sediment ditches accounting for over 95% of the intercepted TN and TP, and 99% of the intercepted SS. This empirical approach provides an efficient and practical tool for rapid performance evaluation of eco-revetments without reliance on complex numerical simulations or large-scale field trials, offering valuable guidance for eco-revetment design and ANSP mitigation efforts.