利用線上流動注入之汞分析儀測定淡水河河口及其近岸海域的總汞

Abstract

本研究發展出一套具可靠性的線上流動注入汞分析儀 (FI-MA)，並應用在淡水河河口及近岸海域之總汞研究。FI-MA是一個半自動雙管線同步分析之測定系統，利用流動注入分析技術，結合二階段金汞齊濃縮法及冷蒸氣螢光光譜法，線上連接三個主要的化學分析裝置和步驟，包含氣液分離、金汞齊預濃縮/熱脫附、偵測/數據處理，使得汞的測定在封閉的管路上進行，減少人為手動操作誤差。FI-MA操作方便，具良好的分析性能，藉由電腦控制以及雙管線同步分析，每一次分析皆獨立進行檢量線校正，可產生高品質、高準確的數據，使系統達到環境測定快、精、準的要求。本研究發表了系統分析性能以及分析設定最佳化的結果，並藉由淡水河總汞分析來驗證系統的可靠性及再現性。本研究在2003年5月、2004年7月、2004年11月、2005年1月四個航次進行表水及沉積物採樣和分析，分成河口、近岸、離岸、海放管周圍四個區域進行比較，發現海放管周圍濃度相對較高，進一步和東亞地區的一些研究進行比較，發現這四個區域的平均值皆比其他研究的參考值來得高，顯示淡水河受到一定程度的汞汙染。此外，本研究發現總汞測定普遍使用的氯化溴氧化劑會對金汞齊吸附造成干擾，進一步解釋其干擾機制和變因並提出解決方法。

A simple and reliable on-line flow injection mercury analyzer (FI-MA) was successfully developed for investigating total mercury (THg) in Danshuei River estuary and adjacent coastal areas. The FI-MA is a semi-automatic dual-channel detection system which provides simultaneous operation. The FI-MA, based on two-stage amalgamation method and cold vapor atomic fluorescence spectrometry, couples the main analytical steps from aqueous Hg reduction, gas-liquid separation, Au amalgamation, thermal desorption to final detection/ data acquisition. All analytical procedures are on-line performed in closed Teflon tubings, so that errors caused by manual operation or contamination are reduced. The FI-MA provides ease of operation and high analytical performance with an excellent data quality. Simultaneous operation of analysis gives a high sample throughput (~ up to 15 samples per hour). Each run analysis is separately calibrated for utmost accuracy. Here, we report the results of system performance tests and reproducibility comparisons regarding the THg determination in water, sediment and bio-tissue samples. Representative field THg data from May 2003, July 2004, November 2004, January 2005 in Danshui River estuary and adjacent coastal areas are also presented. Each cruise covered four areas that was defined below: estuary, near-shore, off-shore, and area around the outfall pipeline, respectively. High THg concentrations were found at the area around the outfall pipeline among them. In addition, higher THg concentrations in Danshui River coastal were observed than those obtained in East Asia marginal seas. This study further found that the widely used BrCl oxidant for THg analysis could diminish the performance of gold amalgamation. The related mechanisms and causes of interference and solutions were proposed as well.