JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2025, Vol. 49 ›› Issue (2): 153-160.doi: 10.12302/j.issn.1000-2006.202305032

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Effect of biochar application on soil runoff and water quality in green roof

LI Juan1(), XUE Jianhui1,2,*(), XIONG Weiwei1, ZHANG Guowei1, WANG Hankun1   

  1. 1. College of Ecology and the Environment, Nanjing Forestry University, Nanjing 210037, China
    2. Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China
  • Received:2023-05-26 Accepted:2023-10-13 Online:2025-03-30 Published:2025-03-28
  • Contact: XUE Jianhui E-mail:17629383009@163.com;jhxue@njfu.edu.cn

Abstract:

【Objective】Roof greening has become a popular method for increasing urban green spaces and mitigating the urban “heat island effect”. Recently, biochar, known for its lightweight and highly porous nature, has been utilized as a soil amendment in the agricultural and forestry sectors. This study explores the impacts of varying biochar application rates and pyrolysis temperatures on soil runoff and nutrient content in roof greening, to assess biochar’s potential for enhancing urban roof greening practices.【Method】The experiment involved three levels of biochar application (0%, 10% and 20%, volume fraction) and three pyrolysis temperatures (300, 400 and 500 ℃), with four replicates per treatment. Each planting box was filled with a 10 cm thick layer of treated soil matrix and planted with Sedum lineare. Soil runoff was collected and analyzed after each rainfall event.【Result】The findings indicated that biochar application could increase soil pH and significantly reduce the levels of total nitrogen (TN) and dissolved organic carbon (DOC) in the runoff. While a 10% biochar addition decreased the total phosphorus (TP) concentration in the runoff, a 20% addition had the opposite effect. Moreover, biochar was effective in reducing soil runoff and nutrient concentration, thus minimizing nutrient loss from the soil. There was no significant difference in the effects of biochar processed at different pyrolysis temperatures on runoff quality. 【Conclusion】Optimal biochar application can significantly decrease N and P loss in roof soil runoff, indirectly reducing urban runoff pollution. This suggests a promising application for biochar in managing urban stormwater runoff.

Key words: roof greening, biochar, addition amount, pyrolysis temperature, soil, runoff water quality, urban pollution

CLC Number: