doi：10.16186/j.cnki.1673-9787.2021100070

Received:2021/10/29

Revised:2022/01/30

Published:2024/01/25

Migration and transformation behavior of DOM from landfill leachate in sandy soil

ZHAO Li1,2,3,  ZHANG Yiyang1,2,3,  JIN Yi1,2,3,  ZHANG Qing1,  LIU Jingyu1,  WEI Jie4,  HE Shichang1

1.School of Resources & Environment，Henan Polytechnic University，Jiaozuo 454000，Henan，China；2.Henan Key Laboratory of Coal Green Conversion，Henan Polytechnic University，Jiaozuo 454000，Henan，China；3.Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region，Henan Polytechnic University，Jiaozuo 454000，Henan，China；4.Jiaozuo Urban Garbage Disposal Management Station，Jiaozuo 454350，Henan，China

Abstract: Objectives Jiaozuo municipal solid waste sanitary landfill has been in operation for over 10 years, with issues such as an aging anti-seepage layer and a high risk of leachate leakage into groundwater. Methods In this study, aged landfill leachate diluted 5 times was used as the injected leachate, and silty sand from the landfill served as the medium. An indoor soil column simulation experiment was conducted with a hydraulic retention time of 32 hours to analyze the migration and transformation behavior of dissolved organic matter (DOM) in the aged landfill leachate. Results The results indicated that, over 0~2 618 hours, the dissolved organic carbon (DOC), chemical oxygen demand (COD), and UV absorbance at 254 nm (UV₂₅₄) exhibited similar variation patterns in groundwater, with significant linear correlations among them, suggesting that the DOM was primarily composed of aromatic compounds. Fitting results from CXTFIT2.1 software indicated low blocking coefficients for DOC (3.01) and COD (1.96), as well as low attenuation coefficients, demonstrating limited adsorption of organic matter by the sand. During the early stage of the experiment, the fluorescence index (FI) of the leached solution was consistently higher than that of the original leachate, indicating rapid microbial growth. All FI values were above 1.9, suggesting a predominantly biogenic source for the DOM in the leachate. The Landfill leachate DOM contained substantial amounts of fulvic acids (peaks A and C) and humic acids (peak E), along with smaller amounts of protein-like substances (peak T₂). Microbial metabolites (peak B) in S1 originated from the sandy soil used in the experiment, and peak B in S1 as well as peak T₂ in S2 disappeared over time, leaving behind the more recalcitrant peaks A, C and E. The organic composition of the leachate evolved significantly, with simpler protein-like compounds gradually disappearing while more complex, recalcitrant humic substances accumulated. Throughout the experiment, the total fluorescence intensity per unit of organic carbon in the leachate exceeded that in the original leachate, indicating an increase in aromatization and humification of the leachate during migration and transformation. Conclusions The findings provide a reference for landfill leachate treatment and environmental risk assessment.

Key words:landfill leachate; dissolved organic matter; groundwater; 3D fluorescence; biodegradation; adsorption