淡水河口海域汞的時序研究： 方法、分布、來源及汙染

Abstract

本研究透過建立淡水河口及八里放流管附近海域的「汞」濃度之時序觀測，了解污染毒物汞在河口沿岸的生地化循環及來源。主要分析了水樣和沉積物中的總汞含量，成功發展了快速、簡單及準確之總汞消化及分析方法，確保所得數據的準確性和可靠性。從2005年至2020年共15年，每年四季進行總汞測定及基本水文觀測，提供了淡水河口及離岸汞濃度長期時空分布的資料以及汞污染的控制過程和來源資訊。在沉積物中，平均總汞濃度為58.0 ± 20.6（範圍17.9至122.1 ng g-1, n = 60），且在放流管周圍（D區, 70.8 ± 23.1）顯著高於沿岸區域（B區, 45.2 ± 18.2）；水體中平均為16.6 ± 14.6 （範圍2.1至73.1 ng L-1, n =60)，D區(16.3 ± 14.2)與B區(16.8 ± 15.0)則無明顯差異 (p > 0.05)。時序變化顯示，沉積物中總汞濃度呈現年均下降趨勢2.6 ng g-1 yr-1 (p < 0.05)，而水樣在統計上無明顯增加的趨勢。此外，研究發現水體中的汞濃度隨季節變化，冷季較高，暖季則較低，且存在異常的高值，可能因八里污水排放所致。多變數迴歸及主成分分析進一步證實了八里放流管對區域總汞濃度污染的影響。盒子模式量化顯示，八里放流管每日排放的汞量是淡水河的4倍，表明淡水河口沿岸總汞濃度的逐年升高，除了淡水河河水汞的輸入外，污水處理廠排放的污水的來源不可忽視。研究結果有助於未來北台灣淡水河口地區環境保護和監測工作的設計和改進，減少汞污染，並提供保護生態和人類健康的科學依據。

This study investigated the temporal dynamics of mercury (Hg) concentrations in the Danshuei River estuary and adjacent waters near the Bali outfall, aiming to understand the biogeochemical Hg cycling and pollution sources in coastal zone. The primary focus was on the total Hg (THg) content in water and sediment samples. A rapid, simple, and accurate method for THg digestion and analysis was developed to ensure data accuracy and reliability. Over a 15-year period from 2005 to 2020, THg measurements and basic hydrological observations were conducted seasonally each year. This provided long-term Hg data on spatial and temporal distribution in the Danshuei River estuary and offshore areas, elucidating the processes and sources of Hg pollution. In sediments, the average THg concentration was 58.0 ± 20.6 ng g-1 (range 17.9 to 122.1 ng g-1, n = 60), with significantly higher concentrations around the outfall (Zone D, 70.8 ± 23.1) compared to coastal areas (Zone B, 45.2 ± 18.2). In water samples, the average concentration was 16.6 ± 14.6 ng L-1 (range 2.1 to 73.1 ng L-1, n = 60), with no significant difference between Zones D (16.3 ± 14.2) and B (16.8 ± 15.0) (p > 0.05). Temporal trends showed a decrease rate of 2.6 ng g-1 yr-1 in sediment THg concentrations (p<0.05), while there is no statistically significant increasing trend in the water samples. Additionally, THg levels in coastal waters varied seasonally, being higher in winter and lower in summer, with occasionally anomalous peaks possibly attributed to outfalls from the Bali sewage treatment plant. Multiple linear regression and principal component analyses further confirmed the effect of the Bali outfall to regional mercury pollution. Box modeling quantified that the daily Hg discharge from Bali outfall was four times that of the Danshuei River, highlighting that the annual increase in Danshuei coastal Hg concentrations. This increase is not only due to Hg input from the river but also from wastewater discharged by sewage treatment plants. The findings of this study contribute to the design and improvement of environmental protection and monitoring efforts in the Danshuei River estuarine coast of northern Taiwan, aiming to reduce Hg pollution and provide scientific basis for protecting ecosystems and human health.