台灣嘉南平原布袋鑽井岩芯硫酸根還原菌與孔隙水水質之研究

Abstract

台灣西南沿海地區的布袋與北門、學甲與義竹等鄉鎮曾同為地方性烏腳病疫區。以往研究證實該病是因為飲用當地含高濃度砷與腐植物質之地下水而引起。前人對此區沈積物中與砷還原作用相關的地質微生物研究尚缺。硫酸根還原菌在厭氧環境中對許多生物化學作用有極大影響，而硫酸根還原菌Desulfovibrio spp.與Desulfomicrobium spp.等對砷及腐植酸亦都有還原能力。 本研究利用布袋鑽井岩芯，分析其孔隙水及沈積物，以瞭解細菌存在的地化背景如有機碳含量、腐殖物質與離子濃度等。利用分子生物的技術萃取沈積物中細菌的DNA，對硫酸根還原菌之16S rRNA基因進行聚合酶鏈合反應(PCR)，分析與砷或腐殖物質有關的硫酸根還原菌屬，探討此鑽井地層硫酸根還原菌的種類與分佈。 分析結果顯示，從深度20至248公尺間所採集之岩芯沈積物中應皆有硫酸根還原菌之存在，應與地層含有濃度較高的硫酸根與有機物，且泥、砂互層頻繁，利於硫酸根還原菌存在有關。Desulfovibrio spp.與Desulfomicrobium spp.普遍存在布袋岩芯孔隙水砷與腐殖物質濃度高的層位。而有能力代謝砷之硫酸根還原菌Desulfotomaculum存在於高腐殖物質濃度之處以及部分高砷濃度的層位。此外，有還原腐殖酸能力的硫酸根還原菌Desulfobulbus propionicus存在於深80公尺處之地層。

The village Putai was one of the four main “blackfoot disease”(BFD) endemic area located on the southwest coast of Taiwan. There have been many studies on accumulation and release of arsenic in sediments in these areas, but geomicrobiologic study is scarce. Sulfate-reducing bacteria contribute a diverse group of prokaryotes that contribute a variety of essential functions in many anaerobic environments. Recently, many studies suggest that sulfate reducers such as Desulfovibrio spp. and Desulfomicrobium spp. might be responsible for arsenate reduction in sediments, and certain sulfate-reducing bacteria might be able to reduce humic substances. This study aims at revealing the geochemical characteristics of sediments and porewater from a core drilling at Putai. Using molecular biological method, DNA was extracted from sediments. PCR primer sets for the 16S rRNA gene of specific sulfate-reducing bacteria were designed to identify principal sulfate-reducing bacteria related to the reduction of arsenic and humic substances, in sediments with higher concentration of arsenic and humic substances. The results show that all sediment samples between 20 and 248 m depth have demonstrated the presence of sulfate-reducing bacteria. High concentrations of sulfate and organic matter within the frequent intercalation of clay, silt and fine-grained sand layers favorite growth conditions of sulfate-reducing bacteria. Desulfovibrio and Desulfomicrobium seem to be commons in the layers which have high concentration of arsenic and humic substances. Desulfotomaculum had been found mostly in layers of high humic substances and in some l high arsenic layers. Humic – reducing bacteria such as Desulfobulbus propionicus have also been found at 80m depth.