秸秆生物炭输入对滨海湿地土壤团聚体碳固持的调控机制研究

Biochar (BC) technology has recently shown great promising application in repairing degraded coastal wetland soils and increasing soil ‘carbon sink’. The input of BC into soils may greatly influence the turnover of soil organic carbon (SOC) and carbon sequestration, and thus may directly affect the stability of carbon sink in the wetlands. Therefore, it has been a key point to clarify the mechanisms underlying the sequestering carbon and decreasing CO2 emissions from the coastal wetland soils amended with biochars. A batch of BC samples pyrolyzed from corn straw (a C4 plant) at different temperature (200-600 ºC) were added into a coastal wetland soil, and the effects of adding BC on the soil physical and chemical properties, the composition of SOC and the aggregate stability were investigated using Automatic Physical-chemical Adsorption Instrument, Scanning Transmission Electron Microscopy, Energy Dispersive X-Ray Spectroscopy and X-Ray Photoelectron Spectroscopy, which were combined with the approaches of the soil wet-sieving, SOC chemical characterization, stability of carbon isotope (13C) tracer. The object of this study were to (1) identify the priming effects of BC on the decomposition of the wetland litter and the accumulation and mineralization of SOC; (2) determine the effects of the labile carbon in the BC samples, the adsorption properties of BC and the interaction between BC and organo-mineral complex on the mineralization of SOC in the wetland soils; and (3) illustrate the mechanisms underlying the adding BC on the enhanced carbon sequestration of the soil aggregates in the coastal wetland soils. These results are useful for assessing the environmental benefits of adding BC into the coastal wetland soils and thus could be useful for producing designer biochars as engineered reagents to remediate the degraded coastal wetlands and sequestrate carbon in the soils.

近年来兴起的生物炭(biochar, BC)技术在修复退化滨海湿地土壤，增加土壤“碳汇”方面具有巨大的应用前景。BC输入对土壤有机碳(SOC)周转和碳固持能力的影响直接关系到湿地碳库的稳定性，阐明其作用机制已成为当前土壤固碳减排研究的热点。本项目以典型C4植物秸秆在不同温度下热解制备BC，利用全自动物理-化学吸附仪、扫描透射电镜-能量色散谱和X射线光电子能谱等新技术，结合土壤筛分、SOC化学表征及碳-13同位素示踪等方法研究BC对滨海湿地盐渍土壤理化性质、团聚体稳定性和SOC组成的改变，探明BC在凋落物分解、SOC累积及矿化中的激发效应，搞清BC中的不稳定碳、BC的吸附特性及与土壤有机-矿物复合体的相互作用对SOC矿化的影响，最终揭示BC输入对滨海湿地土壤团聚体碳固持的调控机制，以期客观评价BC在退化滨海湿地土壤修复及固碳减排中的作用，为构建提高湿地“碳汇”功能的BC技术提供重要理论支撑。

生物炭(biochar, BC)技术在修复退化滨海湿地土壤，缓解“蓝碳”资源损失，增强滨海湿地生态系统碳封存潜能方面作用巨大。阐明BC对土壤有机碳(SOC)周转和碳固持机制是当前土壤固碳减排研究的热点。本研究以农业废弃生物质制备了350ºC和550 ºC的C4植物玉米秸秆生物炭及350ºC花生壳生物炭，利用全自动物理-化学吸附仪、扫描透射电镜-能量色散谱和X射线光电子能谱等新技术方法研究BC对滨海湿地盐渍土壤理化性质、团聚体稳定性和SOC组成的改变，探明了BC在凋落物分解、SOC累积及矿化中的激发效应及影响机制。结果表明：生物炭改善了滨海盐碱土的土壤性质，包括降低了土壤交换性钠和碱化度，增加了土壤有机质和阳离子交换容量，低BC添加条件下提高了盐碱植物田菁和锦葵的生物量；生物炭对微生物和可利用碳底物的吸附作用降低了土壤微生物的碳利用效率，导致生物炭对土壤有机质的矿化表现出负激发效应，生物炭高的pH促进了土壤有机碳矿化向无机碳酸盐沉淀的转化；生物炭提高了碳氮比，降低了尿素酶活性，减少了土壤的净氮矿化；本研究结果发现生物炭对土壤团聚体结构稳定性的强化作用与土壤微生物群落结构的调解作用是生物炭抑制土壤有机碳矿化，降低土壤碳库的流失的关键过程机制。生物炭中丰富的含氧官能团（例如：羧基-COOH, 羟基-OH）和多价阳离子（例如Ca2+和Al3+）等通过配位、阳离子桥联作用促成了生物炭与土壤团聚体中有机-矿物复合体紧密结合，这不仅增强了以有机-矿物复合体为基础的团聚体固定土壤有机物过程，同时通过团聚体的物理保护作用延缓生物炭在土壤中氧化分解，提高了生物炭修复土壤固碳能力的效率。此外，生物炭诱导的低碳矿化细菌种属(例如： Actinobacteria 和Deltaproteobacteria)的促进作用，有利于土壤有机碳的负激发效应。因此，生物炭可作为恢复退化滨海湿地生态系统的理想材料，能缓解“蓝碳”资源从滨海湿地盐渍土壤流失，同时拓宽了生物炭增强陆地生态系统碳封存潜力的应用前景。