2014-08-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/706425摘要：砷是一種以毒著名的類金屬，在水中溶解型態基本上可區分為有機砷及無機砷，其中無機砷毒性非常強，海洋生物對其有很強的富集能力(富集係數高達3.3×102)。無機砷中又分別分為三價砷(As(III), HAsO32-)及五價砷(As(V), HAsO42-)，有機砷中又分別分為甲基砷 (monomethylarsenic (MMA)，dimethylarsenic (DMA))等。海水中砷的平均濃度約為3 ug/L，呈半守恆海洋垂直分佈狀態，有光層中受生物作用影響而有明顯增減變化。過去研究獨重無機砷，對於有機砷研究卻相當匱乏，而對於砷與懸浮生物/礦物顆粒、奈米粒子、甚至膠體間之反應研究更是付之闕如。台灣近數十年來獨重經濟發展，卻不注意環境保護的情況下，工業及農牧養殖廢水導入河川及近岸海水中，造成嚴重的污染問題。然而，學界至今尚缺乏研究對於污染物被排放至河川中後存在的特性、污染物由河川經河口傳送至沿岸水體與大洋中的過程中存在型態的轉化、污染物輸送至近岸的通量及其擴散、以及污染物對水體生態系中基礎生物分布和生產力的影響。這些對生態環境的有系統研究，都是需要我們更努力取得的資訊。本計劃第一年將探討微量元素砷，由陸上及近岸來源被傳送到海洋的過程中，可能發生的相轉移、物種轉變、反應動力，也將研究其在河水、河口、及海水環境中與懸浮顆粒、膠體、有機物及浮游生物之間發生的作用。河川流域上游經河口抵達海洋的濃度時空變化，微量元素砷在不同環境條件下轉變的機制和不同物種變化的途徑。實驗室內模擬和野外實際測量的時間系列實驗結合化學物種的分析、懸浮顆粒和和膠體的詳細定量與特性分析，將協助解釋各相之間作用的途徑及反應速率和反應常數，從而解釋自然產生和人為污染的微量元素砷在水環境中的循環與通量。簡言之，本計畫的整體目標是研究自然存在和人為影響導入台灣河川、河口、沿岸水域與大洋中微量元素砷的傳輸、轉化、與宿命，結果將會被量化，而其中的控制機制將會是研究的重心。<br> Abstract: Arsenic is notorious for its toxicity to biota. The anionic form in natural waters makes its analytical challenged from those of transition metals. Furthermore, arsenic in nature presents in various oxidation states, such as arsenate (As(V), HAsO42-), arsenite (As(III), HAsO32-), or even organoarsenic compounds like methylated arsenic, these forms of As also contain colloidal and nano-particle phases. The diverse arsenic species in natural increases the difficulty in elucidating the arsenic cycling in the ocean. During the past few decades, highly industrialization and urbanization, accompanied by an increase in heavy metal pollution together with organic pollution in the estuary and coastal environments, have been a critical problem in Taiwan. Arsenic, the metalloid in the VA group in the periodic table, is notorious for its toxicity to biota. Due to widespread pollution of drinking and groundwater by arsenic in several countries,and due to the toxicity of As, its distribution and behaviour has recently been investigated in numerous studies. However, there is no generally accepted explanation scheme for the controlling processes. Because of great differences in toxicity between As compounds, the form in which As enters the environment is important. In oxic natural waters total dissolved As(td-As) occurs primarily in inorganic forms, with pentavalent As being the most stable form but with significant contributions from metastable As (III); organic forms comprise predominantly monomethyarsonic acid and dimethylarsinic acid, which are likely produced by phytoplankton to mitigate toxicity stress. Speciation of a trace element in natural waters and the distinction between the solution, colloids and particles is important to various environmental questions, including those concerning the cycling of toxic elements and especially their transport properties. This proposal will focus on the transformation and transportation processes, the reaction kinetics of As from in-land waters to coastal environments, on their association with suspended particles, colloids, organic matter, and interaction with plankton. Time-series experiment will be performed in the field and laboratory in order to obtain transformation rates and rate constants, together with the speciation study can elucidate the pathways and interactions, hence construct the cycles and fluxes of natural and anthropogenic As in the coastal regimes.砷膠體河水河口灣海水ArsenicSpeciationColloidsEstuary