| 摘要: | 紅樹林為重要的潮間帶濕地生態系統，具有較高的初級生產力，豐富的碎屑及有機碳。為了解濕地有機質保存埋藏的控制過程，本研究針對現生淺層沉積物進行採樣分析，評估其礦物相、總有機碳(TOC%)、熱裂分析(Rock-Eval)、現地水質資料，並透過生物標記(Biomarker)分析樣品中有機物的材料來源。本研究採台北淡水紅樹林自然保留區之沉積物，依距離淡水河道遠近選擇兩個採樣點進行分析(離陸F及近陸N)，分別採集四種不同深度的樣品(表層0-5cm、5-15cm、15-30cm、30-40cm)。分析結果顯示TOC介於0.17%-0.8%；熱裂分析Tmax為364-443℃，S1、S2分別為0.08-0.19 mg HC/g rock及 0.07-0.47 mg HC/g rock，所有樣品皆屬於低有機豐度及低成熟度的材料。離陸(F)之TOC與S2含量皆較高，TAR顯示有機質來源以低碳鏈的藻類及浮游動物居多；近陸(N) TOC相對較低，有機質在表層以陸生植物來源為主，底層則是海相占多數；Pr/Ph 顯示兩處皆以氧化環境為主。水質資料顯示兩個採樣點皆受海水影響，且離陸地區有較高的溶氧量及導電度。由XRD礦物組成分析，發現所有樣品中均含有石英、長石、伊萊石、高嶺石和綠泥石，其中以石英含量最多。離陸地區主要黏土礦物為伊萊石，近陸地區則以伊萊石及高嶺石為主要礦物，無發現蒙脫石的訊號。根據以上不同位置及深度所造成的樣品特性差異，發現距離淡水河道遠近將會影響沉積物有機質來源，氧化或還原環境將影響有機質的累積。;Mangrove swamp is an important intertidal wetland ecosystem with high primary productivity, abundant detritus, and also rich in organic carbon. In order to understand the process and mechanism of organic materials during burial and preservation processes in a mangrove swamp, we evaluated the mineralogy, total organic carbon (TOC %), Rock-Eval pyrolysis, water quality, as well as biomarker to analyze the depositional characteristics. Study site was a mangrove swamp in Tamsui, NW Taiwan. In this area, we chose two sampling sites, F (Far-off land) and N (Near land). Samples were collected from different depths (0-5cm, 5-15cm, 15-30cm, 30-40cm). We found that TOC varied between 0.17% and 0.8%, Tmax values were 364 to 443oC; S1 and S2 were ranging from 0.08 to 0.19 mg HC/g rock and 0.07 to 0.47 mg HC/g rock respectively. Hydrocarbon potential was immature in all samples. Far-off land samples exhibit higher total organic carbon content and S2 value than near land. Major organic matters we found in far-off land are algae and zooplanktons. However, organic materials in surface and bottom layer of the near land are terrigenous and marine materials, respectively. In addition, water quality data showed that both areas were influenced by sea water. F area also exhibited higher dissolved oxygen and electricity conductivity. Mineralogy from XRD indicated that all of the soils were characterized by quartz, feldspar, illite, kaolinite and chlorite. Major clay mineral in F samples is illite. Besides, illite and kaolinite are major clay minerals in N samples. Finally, biomarker analysis indicates an oxic environment of all samples. Based on the above analyses from different localities and depths, we found that the distance to the sea affects the source of organic materials, and redox conditions further affect the accumulation of organic materials. |
