Jiang Bi-Ni, Zhang Ying-Ying, Wang Yan, Liu Hai-Qin, Zhang Zhi-Yong, Yang Yi-Jing, Song Hai-Liang
Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Key Laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing, 210014, , PR China; School of Environment, Nanjing Normal University, Jiangsu Province Engineering Research Center of Environmental Risk Prevention and Emergency Response Technology, Jiangsu Engineering Lab of Water and Soil Eco-remediation, Wenyuan Road 1, Nanjing 210023, PR China.
Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Key Laboratory of Agro-Environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Nanjing, 210014, , PR China.
Water Res. 2025 Mar 15;272:122945. doi: 10.1016/j.watres.2024.122945. Epub 2024 Dec 9.
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 NO 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 NO 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 NO sinks (P < 0.01) and TN removal rate (P < 0.001), whereas the remaining amended eco-ditches that significantly intensified TN removal performance, were NO 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 NO 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 NO sink-induced cooling and has significant practical implications for better understanding the cascading effects of mixotrophic denitrification driven by iron-carbon interactions.
铁 - 碳耦合能够形成混合营养反硝化作用，被视为净化富含硝酸盐的农业径流的一种有前景的解决方案。然而，在生态沟渠（生态沟）中，其在协同增强氮去除和净一氧化氮汇方面的普遍性和功效仍是关键的知识空白。在此，我们通过采用经微波辅助（MW）热解和常规热解制备的海绵铁（sFe）耦合的六棱鸢尾（IH）或粉绿狐尾藻（MA）衍生生物炭，研究了潜在的变异性机制。令人惊讶的是，未改良的生态沟变成了净一氧化氮汇，同时与土壤沟渠相比，总氮（TN）去除率显著提高了319%（P < 0.001）。将MW热解的IH衍生生物炭与sFe整合以改良生态沟，实现了净一氧化氮汇（P < 0.01）和TN去除率（P < 0.001）的同步增强，而其余改良的生态沟虽然显著增强了TN去除性能，但却是一氧化氮排放源。这种异质性主要取决于铁有机络合物（Fep）/总活性铁氧化物（Fed）的比例，而非占主导的nosZ基因，这突出表明在混合营养反硝化过程中，低密度亚稳活性铁比生物反应起更重要的作用。因此，铁氧化物不一定是反硝化作用的瓶颈，且有助于形成一氧化氮汇。相反，微生物生物量C:(C + N)，连同nirK和nosZ基因，主要解释了sFe - 生物炭生态沟中TN去除的异质性。本研究重新审视了铁 - 碳耦合对氮减排和一氧化氮汇诱导降温的不同恢复力，对于更好地理解铁 - 碳相互作用驱动的混合营养反硝化的级联效应具有重要的实际意义。
