新武呂溪流域之硫酸鹽來源與微生物黃鐵礦氧化作用

Sulfate source and microbial pyrite oxidation in the Shinwulu river system

吳易峰(I-Feng Wu)

指導教授 ： 王珮玲

國立臺灣大學/理學院/海洋研究所/碩士(2020年)

https://doi.org/10.6342/NTU202000316

摘要

河流傳輸的硫酸鹽是海水硫酸鹽重要來源，與全球硫循環有密切的關係。前人研究大多關注硫酸鹽來源、估算風化速率及調控氣候的機制，對於風化過程中是否有微生物作用的參與並未闡明。河川中的硫酸鹽的主要來源是硫化礦物氧化及硫酸鹽類礦物溶解等化學風化作用產物，也包含大氣沉降或人為活動所貢獻，其中硫化礦物氧化可能與微生物作用關係密切。卑南溪流域是台灣河川沉積物傳輸通量最高及高化學風化速率的流域，流域內以板岩和片岩為主，考量缺乏蒸發岩與有限的人為活動，過去的研究顯示其硫酸鹽的來源即可能為黃鐵礦風化而來，可做為探討硫氧化菌與黃鐵礦風化關聯性的良好題材，釐清化學風化過程微生物作用的角色。
本研究於 2017 年 5 月至 9 月間定期採取卑南溪上游新武呂溪流域河流懸浮沈積物，並對 7 月底發生的兩次颱風事件進行高頻率採樣，希望藉由地球化學和分子生物技術，探討此流域硫氧化菌群組成、豐度及與黃鐵礦風化之間的關聯性。綜合各種分析結果顯示大水事件前、中、後的河水離子濃度、同位素及分子生物結果皆有時序上的變化，推斷河水化學風化路徑並非恆定，且強降雨造成的水量變化對水化學及微生物影響力之甚。此外，針對Betaproteobactria與 Epsilonproteobacteria兩菌群之 soxB 基因數量與懸浮顆粒濃度、硫酸根、硝酸根都呈現弱相關性，代表微生物參與的硫氧化作用強弱無法直接連結現地環境相關水文化學資料的變化，顯然微生物與環境因子之間有著複雜的關聯性。針對Betaproteobactria菌群定序分析顯示，樣品中的硫氧化菌族群多樣性高，樣品間結構穩定且相似，以 Thiobacillaceae、Comanmonadaceae、Gallionellaceae菌科為主。新武呂溪流域偵測到硫氧化菌的存在，可證實區域內河水硫酸鹽的來源與微生物促進的黃鐵礦風化作用有密不可分的關係。

關鍵字

新武呂溪 ； 河水硫酸鹽 ； 黃鐵礦氧化 ； 硫氧化菌

並列摘要

Riverine sulfate is an important source of marine sulfate, thereby driving the global sulfur cycle. Previous studies focus mostly on examining the source of sulfate, weathering rate, and the effect on climate regulation. However, the role of microorganisms in weathering processes is not well known. Riverine sulfate is sourced from the weathering of sulfide minerals, evaporite minerals, atmospheric deposition, or human activities. The Beinan River catchment is dominated by slate and schist and has demonstrated high sediment flux and high chemical weathering rate in Taiwan. Due to the lack of evaporite and the limited anthropogenic activities in this area, pyrite oxidation might largely attribute to riverine sulfate, providing an ideal subject to explore the microbial roles in chemical weathering processes.
This study collected monthly samples from the Shinwulu River, the upstream Beinan River between May and September of 2017, and frequent samples during two consecutive typhoons in late July. Geochemical and molecular analyses were conducted to investigate pyrite oxidation pathways, and abundances and diversities of sulfur-oxidizing bacteria (SOB). The sulfate and nitrate concentrations, sulfur and oxygen isotopes in sulfate, and molecular results all varied through time, suggesting that the chemical weathering pathway is not constant. Moreover, the change of water discharge caused by heavy rainfall exerted a great influence on water chemistry and the sox gene abundance of Betaproteobactria and Epsilonproteobacteria. However, the weak correlations between soxB gene abundance and either the concentration of suspended particles or anion concentration suggested that the hydrogeochemical data can only be explained partly by the strength of microbially-mediated sulfur oxidation. The soxB sequencing results of Betaproteobactria demonstrated that the SOB communities are diverse and stable through time, regardless of the impact of typhoons. The SOB affiliated with Betaproteobactria is composed of Thiobacillaceae, Comanmonadaceae, and Gallionellaceae. Overall, the presence of abundant SOB in the Shinwulu River suggests that the production of riverine sulfate is closely related to the microbial pyrite oxidation.

並列關鍵字

Shinwulu River ； riverine sulfate ； pyrite oxidation ； sulfur oxidizing bacteria

參考文獻

中文部分

王奕傑 (2019) 卑南溪流域化學風化作用對二氧化碳收支的影響，國立臺灣大學海洋研究所碩士論文，共 89 頁。

英文部分

Andermann, C., Longuevergne, L., Bonnet, S., Crave, A., Davy, P., and Gloaguen, R., 2012, Impact of transient groundwater storage on the discharge of Himalayan rivers: Nature Geoscience, v. 5, no. 2, p. 127-132.

Balci, N., Shanks, W. C., Mayer, B., and Mandernack, K. W., 2007, Oxygen and sulfur isotope systematics of sulfate produced by bacterial and abiotic oxidation of pyrite: Geochimica Et Cosmochimica Acta, v. 71, no. 15, p. 3796-3811.