泥炭沼泽源酚酸对铁有机复合体的溶解作用及其环境意义

Dissolution of Fe-Organic Associations by Peatland-Derived Phenolic Acids and Its Environmental Significance

泥炭沼泽是具有全球意义的湿地类型,研究泥炭沼泽源酚酸对铁有机复合体的溶解作用有助于深入了解铁碳耦合地球化学循环过程.以中国东北金川泥炭沼泽为研究对象,提取了泥炭腐殖质,并实验合成了铁有机复合体及一系列的铁氧化物.选择原儿茶酸、咖啡酸和没食子酸等代表性泥炭沼泽源酚酸对铁有机复合体以及铁氧化物等系统开展了不同条件下的溶解试验.结果表明酚酸对无定型的水铁矿和新合成的铁有机复合溶解能力相对较弱,而对结晶态的赤铁矿、针铁矿和老化后的铁有机复合体的溶解能力较强.pH值、酚酸浓度和铁氧化物自身的结构和组成都对铁矿物的溶解作用产生影响.反映了铁有机复合体在酚酸溶液体系中比无机铁氧化物更稳定,这与泥炭沼泽中有机结合态铁比例较高、而普通矿质土壤中结晶态铁氧化物占比更大的事实相吻合.证明了铁有机复合体是泥炭沼泽中影响铁碳循环耦合的关键载体.泥炭沼泽中铁碳作用十分复杂,既能以铁有机络合物形式向海洋等水生生态系统输出大量的溶解性铁,也能通过铁有机复合体的形成促进泥炭沼泽有机碳的保存,进而影响全球铁碳循环耦合,具有重要的生态环境意义.

Peatland is a type of wetland with global significance, and the study of the dissolution of phenolic-iron complexes by peat derived phenolic acids helps us to understand better the iron-carbon coupled geochemical cycle. In this study, humic substances were extracted from Jingchuan peatland soils and hematite, goethite, ferrihydrite and Fe-organic associations were synthesized. After that, a series of dissolution experiments were performed with three representative peatland-derived phenolic acids, including gallic acid, caffeic acid and protocatechuic acid. Results show that the amorphous ferrihydrite and the newly synthesized humic-Fe have weaker dissolution capacities, but the well-crystallized goethite, hematite and the humic-Fe after ag- ing have better dissolution capacities, meanwhile the humic-Fe could be more stable in the phenolic acids solution than the pure iron oxides. It is confirmed that the organic iron makes up higher proportion in peatland soil, while the crystallized iron oxides make up higher proportion in mineral soils. The interaction between iron and carbon in peatland is complicated, where iron could be exported to aquatic ecosystem such as the ocean by complexing with iron, and organic carbon could also be preserved by forming Fe-organic complexes, thus affecting the global iron-earbon coupled geochemical cycle.