Microbial biomass stoichiometry and proportion of Fe organic complexes separately shape the heterogeneity of mixotrophic denitrification and net N2O sinks in iron-carbon amended ecological ditch

IF 11.4 1区环境科学与生态学 Q1 ENGINEERING, ENVIRONMENTAL

Water Research Pub Date : 2024-12-09 DOI:10.1016/j.watres.2024.122945

Bi-Ni Jiang, Ying-Ying Zhang, Yan Wang, Hai-qin Liu, Zhi-Yong Zhang, Yi-Jing Yang, Hai-Liang Song

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Abstract

Coupling of iron-carbon can form a mixotrophic denitrification and is regarded as a promising solution for purifying nitrate-rich agricultural runoff. However, its prevalence and efficacy of the synergistic augmentation of nitrogen elimination and net N₂O sinks remain crucial knowledge gaps in ecological ditches (eco-ditches). Here, we investigated the underlying variability mechanisms by implementing sponge iron (sFe)-coupled Iris hexagonus (IH)- or Myriophyllum aquaticum (MA)-derived biochar produced via microwave-assisted (MW) pyrolysis and conventional pyrolysis. Surprisingly, unamened eco-ditch became net N₂O sink while exhibiting a significant increase in total nitrogen (TN) removal rate of 319% (P < 0.001) compared to soil ditch. The integration of MW pyrolyzed IH-derived biochar with sFe to amend eco-ditch achieved synchronous enhancement in net N₂O sinks (P < 0.01) and TN removal rate (P < 0.001), whereas the remaining amended eco-ditches that significantly intensified TN removal performance, were N₂O emitters. Such heterogeneity primarily depends on Fe organic complexes (Fep) / the total reactive Fe oxides (Fed) ratio, rather than the prevailing nosZ gene, underscoring that low density metastable reactive iron plays a more important role than biological reactions during the mixotrophic denitrification process. As such, iron oxides are not necessarily a bottleneck for denitrification and contribute to N₂O sinks. Conversely, microbial biomass C:(C+N), together with nirK and nosZ genes, mainly explain the TN removal heterogeneity of sFe–biochar eco-ditch. This study revisits the discrepant resilience of iron-carbon coupling to N abatement and N₂O sink-induced cooling and has significant practical implications for better understanding the cascading effects of mixotrophic denitrification driven by iron-carbon interactions.

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来源期刊

Water Research 环境科学-工程：环境

CiteScore

20.80

自引率

9.40%

发文量

1307

审稿时长

38 days

期刊介绍： Water Research, along with its open access companion journal Water Research X, serves as a platform for publishing original research papers covering various aspects of the science and technology related to the anthropogenic water cycle, water quality, and its management worldwide. The audience targeted by the journal comprises biologists, chemical engineers, chemists, civil engineers, environmental engineers, limnologists, and microbiologists. The scope of the journal include: •Treatment processes for water and wastewaters (municipal, agricultural, industrial, and on-site treatment), including resource recovery and residuals management; •Urban hydrology including sewer systems, stormwater management, and green infrastructure; •Drinking water treatment and distribution; •Potable and non-potable water reuse; •Sanitation, public health, and risk assessment; •Anaerobic digestion, solid and hazardous waste management, including source characterization and the effects and control of leachates and gaseous emissions; •Contaminants (chemical, microbial, anthropogenic particles such as nanoparticles or microplastics) and related water quality sensing, monitoring, fate, and assessment; •Anthropogenic impacts on inland, tidal, coastal and urban waters, focusing on surface and ground waters, and point and non-point sources of pollution; •Environmental restoration, linked to surface water, groundwater and groundwater remediation; •Analysis of the interfaces between sediments and water, and between water and atmosphere, focusing specifically on anthropogenic impacts; •Mathematical modelling, systems analysis, machine learning, and beneficial use of big data related to the anthropogenic water cycle; •Socio-economic, policy, and regulations studies.