隨著工業的發展與社會的變遷，許多有害物質被蓄意或無意地排放至環境中，使得環境污染的問題日益嚴重，也讓農地遭受重金屬污染的事件層出不窮。由於農產品的安全攸關國民的健康與生活品質，因此一直是大眾所關注的重要議題，同時也是政府的施政重點之一。在所有的農作裡，稻米因為是亞洲地區(包括身處其中的東協等開發中國家)人民的主食，因此食米的安全品質，特別是米粒內重金屬超量累積與否的問題格外引人注意。而水田在稻作栽種期間涵蓋著厭氧與好氧兩種狀態，如此特殊的環境演化也加深在探討重金屬污染物於此生態系統傳輸與化性轉換時的複雜度。在台灣，即使土壤中的鎘濃度未達管制標準，但鎘米事件仍是時有所聞，造成農政與環保單位的困擾。有鑑於此，本研究以過去幾年我們對於與鎘化性相近的汞在水田系統的生物地質化學循環轉換的機制調查結果為基礎，進一步以文獻上相對應的底泥汞污染現地整治的方法與學理為依據，並在保留土壤資源及無損稻作生長收成的考量下，擬以施加亞鐵及硫酸鹽的地球化學調控法、以及施用由農業廢棄物轉製而成且對金屬與溶解性有機物有不同吸附特性的活性碳、生物炭與水熱合成炭等的吸附材添加法，藉由土壤植栽與縮模吸附試驗，有系統的同時探究此等具環境友善的現地工法對於有效降低受污染稻田土中親硫金屬汞、鎘的植作生物可利用性之潛力。除此之外，本研究也將同步評估兩種農藝技術的整合對於推廣至資源較為匱乏的發展中國家之可能性，以呼應國家政策的推動。本研究所得的成果預期可作為未來國內外農地污染管理與整治的參考。 ;Industrialization and societal development have led to many harmful substances deliberately or inadvertently released to the environment, causing farmlands increasingly polluted with heavy metals. Given that the safety of agricultural products is intimately linked to people's health and quality of life, farmlands free-of-contamination or remediation has been one of the government's priorities and also an important issue of public concern. Of all the crops, rice is a staple food for people in most Asia, including the developing countries such as Association of Southeast Asian Nations (ASEAN), and thus the safety and quality of rice (especially the problem with heavy metal accumulation in rice grains) is a particular issue that draws public attention. Hoever, the unique characteristic of paddy rhizosphere evolving from anaerobic to aerobic stages during rice cultivation deepens the complexity of studying the fate and transport of heavy metal pollutants in this sensitive ecosystem. In Taiwan, although cadmium (Cd) concentrations in farmland soils are not in excess of regulatory standards, incidents of "Cd-tainted rice" are still reported all the time, causing troubles on both agricultural and environmental protection agencies. Accordingly, on the basis of (i) our previous investigation results of Hg cycling and transformations in the paddy rhizosphere and (ii) the successful in situ remediation efforts reported in the literature that deal with sediments contamination with Hg, here we propose to use two eco-friendly approaches that include geochemical amendments (i.e., application of ferrous iron and sulfate species into paddies) as well as sorbent (i.e., activated carbons, pyrochars and hydrochars produced from agricultural wastes) amendments to mitigate phyto-availability of chalchophile metals (i.e., Hg and Cd) in rice paddies. Pot tests and microcosm isotherm experiments will be carried out to systematically assess the efficacy of the two in situ agronomic technologies. In addition, we will evaluate the potential to extend these practices to ASEAN in response to the current national policies. Results obtained in this study are expected to serve as a reference for future pollution management and remediation on agricultural land in general.
