Novel ecological ditch system for nutrient removal from farmland drainage in plain area: Performance and mechanism

• Published in: Journal of environmental management 2022-09, Vol.318, p.115638-115638, Article 115638
• Main Authors: Jin, Jiyuan, Tian, Xin, Liu, Guanglong, Huang, Jiacong, Zhu, He, Qiu, Shaojun, Fu, Xin, Wu, Yanhong, Bing, Haijian
• Format: Article
• Language: English
• Subjects: Chengdu plain; Ecological ditch system; Iron-loaded biochar; Nitrogen and phosphorus; Non-point source pollution; Removal efficiency
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2022.115638

The loading of nitrogen (N) and phosphorus (P) from agricultural drainage as the non-point sources is a worldwide environmental issue for aquatic ecosystem. However, how to remove these nutrients effectively from agricultural drainage remains a big challenge with increasing cemented ditches for better management. Here, we designed a novel ecological ditch system which integrated an earth ditch and a cemented ditch with iron-loaded biochar in the Chengdu Plain to reduce the loss of N and P from farmland. After a two-year monitoring, the removal efficiency of total N and total P reached 24.9% and 36.1% by the earth ditch and 30.7% and 57.8% by the integrated ditch system, respectively. The water quality was evidently improved after passing through the ditch system with the marked decrease in the concentrations of N and P. Dissolved organic N, nitrate, and particulate P became the dominant fractions of N and P loss. Rainfall soon after fertilization increased the concentrations of N and P in the ditch system and markedly affected their removal efficiency. The iron-loaded biochar effectively removed N and P from the drainage, especially at the high concentrations, which was mainly attributed to its high adsorption of the dissolved N and P fractions and the interception of the particulate nutrients. Our results indicate that the designed ecological ditch system has a high potential for alleviating agricultural non-point source pollution in the plain area and can be extended to other lowland agricultural ecosystems. [Display omitted] •A novel ecological ditch system was constructed to reduce nutrient loss in plain area.•Removal efficiency of nitrogen and phosphorus reached 30.7% and 57.8%, respectively.•Ammonia nitrogen and particulate phosphorus were the main removal fractions.•Rainfall with fertilization decreased markedly the removal efficiency of nitrogen and phosphorus.•Iron-loaded biochar effectively removed high-level nutrients from drainage.