模拟Fe(III)和盐水输入对闽江河口潮汐湿地沉积物及间隙水Fe和S含量和形态的影响

Effects of saltwater incursion and ferric iron enrichment on abundance and fractions of Fe and S in pore water and sediment of a tidal freshwater wetland in the Min River estuary

河口潮汐湿地沉积物电子受体和盐度的变化将对间隙水、沉积物的地球化学参数及有机碳厌氧矿化途径产生重要影响.本研究于闽江河口塔礁洲淡水野慈姑(Sagittaria trifolia L.)湿地原位施加人造海水及Fe(III)溶液,模拟研究了盐水入侵及径流Fe(III)浓度增强对河口潮汐湿地沉积物、间隙水的地球化学参数(溶解性CH4、DOC、DOC∶DON、Fe2+和ΔSO2-4)和沉积物各形态固相铁(非硫Fe(II)、无定形Fe(III)、晶质Fe(III)、Fe S和Fe S2)含量的影响.结果表明,模拟盐水入侵及径流Fe(III)浓度增强均可降低间隙水溶解性CH4和DOC浓度,径流Fe(III)浓度增强增加了非硫Fe(II)和晶质Fe(III)含量,盐水入侵可减小间隙水ΔSO2-4含量.间隙水ΔSO2-4与DOC、DOC∶DON、溶解性CH4及Fe2+浓度相关.模拟盐水入侵及径流Fe(III)浓度增强可分别促进硫酸盐异化还原和铁异化还原速率,同时减小间隙水CH4浓度,改变河口潮汐湿地土壤有机质厌氧矿化优势途径.

Increases in salinity and electron acceptors have a significant impact on pore water and sediment geochemistry and organic matter mineralization in tidal wetlands. In this study, artificial saltwater and Fe （III） were applied to in situ mesocosms of the tidal freshwater Sagittaria trifolia L. wetland of the Min River Estuary. Pore water geochemistry, including dissolved CH4, dissolved organic carbon （DOC）, the ratio of DOC to dissolved organic nitrogen （DON） , pore water Fe2＋ and ASO42-, and various species of solid Fe （non-sulfidic Fe（ II）, amorphous Fe（III） , crystalline Fe（III） , FeS, and FeS2 ） were analyzed to compare treatments between spring and summer. The results suggest that dissolved CH4 and DOC were suppressed due to seasonal treatment using saltwater and Fe（ III）. The addition of Fe（Ill） increased non-sulfidic Fe（II） and crystalline Fe（ III）, wherea.s the addition of saltwater decreased pore water ΔSO2-4. The pore waler ΔSO2-4 values correlated with DOC, DOC ：DON, Fe2＋, and dissolved CH4. The addition of Fe（III） and saltwater may enhance microbial iron and sulfate respiration, respeetively, as both concurrently inhibit methane production, thus shifting the pathway of orgarede mineralization.