氣候變遷情境下土壤有機質與集水區水質的潛在交互關係

Potential Interactions between Soil Organics and Watershed Water Quality under Climate Change Scenarios

盧丁魁(Din-Kuei Lu)

指導教授 ： 王根樹

國立臺灣大學/公共衛生學院/環境與職業健康科學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002836

摘要

土壤顆粒是集水區中最為常見的一種污染來源，而土壤中的有機質則會貢獻大量的溶解性有機物(dissolved organic matter, DOM)到原水中成為消毒副產物(disinfection byproducts, DBPs)的前質，並且對飲用水水質造成嚴重的影響。除此之外，水資源是非常的脆弱且對於周遭環境的變化非常的敏感，例如:土地利用的情形、人類活動的影響以及氣候的變遷等。先前已有諸多研究顯示許多與氣候變遷相關的因子(例如:溫度、降雨的強度與雨量、各式各樣的極端天氣事件等)都與過去幾十年來地表水中溶解性有機物濃度逐漸上升有非常高度的相關性。然而，僅有有限的研究著眼於氣候變遷的效應下探討土壤的性質與下游的水質之間的交互作用。因此本研究的主要目的在探討不同性質、種類的土壤在氣候變遷所產生的效應下對於原水水質的衝擊，及對飲用水水質的影響，以及評估傳統水處理的效能是否能夠因應原水水質的變化。
研究結果顯示，以上游集水區處採集來的不同土壤樣本所配置之模擬水樣在不同溫度下培養七天之後，水樣中溶解性有機碳濃度以及消毒副產物生成潛能會隨著培養過程中環境溫度的升高而有所上升。而水中非消毒副產物前質(non-DBP precursors)的特性會決定經有機質濃度(Dissolved organic carbon, DOC)標準化後消毒副產物生成潛能(DBP/DOC)對於環境溫度改變的變化，顯示土壤中消毒副產物前質傾向於在水土交互作用的前期便自土壤顆粒釋放到水中。此外，降雨的特性(特別是酸鹼值)會影響到雨水沖刷出土壤中溶解性有機碳之組成，可能原因為台灣的北部區域因氣候環境等因素導致土壤大多呈現酸性，而鹼性的降雨能透過酸鹼中和的作用淋洗出更高比例的消毒物產物前驅物質。至於海平面上升導致溴離子入侵到淡水系統方面，溴離子會使得原水經過加氯消毒後產生更多的含溴消毒副產物，由於含溴消毒副產物相較於含氯消毒副產物有更高的毒性，使得飲用水水質安全方面有更高的風險；而土壤在這當中能夠扮演緩衝的角色，減少海水中溴離子帶來的衝擊並稀釋經處理後清水中含溴消毒副產物的生成濃度。

關鍵字

氣候變遷 ； 土壤 ； 水質 ； 水處理 ； 消毒副產物

並列摘要

Soil particles are the most ubiquitous source of pollutants that are all around the watershed and the soil organics can contribute to the releases of tremendous amount of dissolved organic matter (DOM) in water sources. DOM is the primary precursor of many kinds of disinfection byproducts (DBPs), and hence poses great threat to the drinking water quality. Moreover, water resources are very vulnerable and susceptible to the environmental changes such as the type of land uses, human activities, as well as different kinds of climate change effects. Previous studies have shown that many climate-related factors, such as temperature, amount and intensity of rainfalls, different kinds of extreme weather event and et cetera, are considered highly correlated to the up-going trend of DOM concentration in the surface water during the past decades. However, only limited studies have focused on the interactions between the soil properties and downstream water quality under climate change scenarios. Therefore, the objective of this study is to figure out how different kinds of soil affect the source water quality when exposed to different climate change effects and to estimate the impact on drinking water quality as well as to evaluate the efficacy of the traditional water treatments on source water quality alternations.
After seven days of incubation with soil samples collected from different sites of the upstream watersheds under different temperature, the overall dissolve organic carbon (DOC) concentration and DBP formation potential (DBPFP) increase with rising of the incubation temperature. However, properties of non-DBP precursors will determine the standardized DBPFP (DBP/DOC) alternation with the increase of environmental temperature while the DBP precursors are tended to be washed out in the early days of soil-water interaction. Moreover, the properties of precipitation, especially the pH value, will affect the composition of DOM washout. For the northern area of Taiwan, due to the effects of environment and climate factors, soils are mostly acidic and higher proportion of DBP precursors can be washed out by alkali rainfall because of the strong reactivity of acid-base neutralization. Furthermore, the intrusion of bromide into fresh water system on account of the sea level rise will alter the composition of DBPs in finished water after chlorination, forming more brominated DBPs that possess higher toxicities. However, the presence of soil particles can buffer the impact of bromide intrusion and dilute the concentrations of brominated DBPs.

並列關鍵字

climate change ； soil ； water quality ； water treatment ； disinfection byproduct

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