Dynamic Interception Effect of Internal and External Nitrogen and Phosphorus Migration of Ecological Ditches

Ecological ditch technology and development prospect based on nature-based solutions: a review

The core of the concept of nature-based solutions (NBS) is ecological protection, which is the same direction as China's double-carbon goal and has attracted much attention in China. Ecological ditch sewage treatment technology has been widely used in controlling agricultural non-point source pollution because of its advantages of high pollutant removal efficiency and low energy consumption. Suppose the NBS concept of sustainable management, restoration, and ecological protection is integrated into the research and development and application of ecological ditch technology. In that case, it can not only improve the effective removal of pollutants, achieve the purpose of recycling water resources and nutrient elements, but also realize economic, environmental, and social benefits. This paper describes the ecosystem service functions provided by ecological ditches in detail, evaluates their economic values through literatures review, so as to raise people's awareness of natural resource conservation and realize the sustainable management of ecological ditches.

Inhibition of sediment internal phosphorus release in agricultural drainage ditches by ceria nanoparticle capping

In this study, ceria nanoparticles (CNPs) were introduced as an in-situ capping agent to inhibit the release of phosphorus (P) from sediments of agricultural drainage ditches. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin film (DGT) techniques were used to measure the concentrations of P and iron (Fe) in the overlying water and sediments. The results showed that the CNP capping not only decreased the soluble reactive P (SRP) in the overlying water by 55.36% but also decreased the SRP in the pore water by 30.06%. More importantly, after the CNP capping, the flux of SRP from the pore water to the overlying water decreased by 34.12%, indicating that CNP capping can effectively inhibit the release of P from sediments to the overlying water. In addition, 38.38% of DGT-labile P was immobilized using CNP capping. Furthermore, the results of P speciation showed that CNP capping led to the change of P species from easily released NH4Cl-extractable P (NH4Cl-P) and Na2S2O4/NaHCO3-extractable P (BD-P) to more stable HCl-extractable P (HCl-P) and residual P (Res-P). These results show that CNP capping can further decrease the release of P from sediments to the overlying water. The present study shows that CNP is a feasible and effective capping material to inhibit the release of P from sediments of agricultural drainage ditches.

An Experimental Study of Paddy Drainage Treatment by Zeolite and Effective Microorganisms (EM)

Eco-ditch systems have increasingly been designed and applied as a strategy to decrease the risks of water eutrophication and contamination pollution for sustainable agriculture. The main goal of this study was to evaluate the water quality of eco-ditch substrates amended with zeolite and Effective Microorganisms (EM), such as pH, dissolved oxygen concentration (DO), ammonium nitrogen concentration (NH4+-N), and nitrate nitrogen concentration (NO3−-N). Laboratory experiments were conducted with four single substrates (soil, none substrates, natural zeolite, and zeolite loaded with EM bacteria) and two mixed substrates (soil and varying proportions of the additives, 0, 5 and 15%, m/m). Results showed that the concentration of NH4+-N was decreased with the increasing rates of additives, and zeolite loaded with EM bacteria had the highest nitrogen removal rate (97.90%) under static experimental condition. The application rate of 15% zeolite loaded with EM bacteria on the eco-ditch exerted a better effect on NH4+-N and NO3−-N removal without pH reduction, decreased by 87.19% for NH4+-N and 30.33% for NO3−-N, respectively. Path analysis showed that zeolite addition had a rapid effect (path coefficient = −0.972) on free NH4+-N ions adsorption in early 1–3 days, then EM loaded at zeolite further decreased NH4+-N (path coefficient = −0.693) and NO3−-N (path coefficient = −0.334) via bacterial metabolism. Based on the results, the applications of natural zeolite and Effective Microorganisms (EM) at an appropriate rate (15%, m/m) can significantly improve water quality of paddy drainage via exerting effects on nitrogen removal.