Monitoring and Analysis of Nonpoint Source Pollution - Case study on paddy fields in a watershed
化學肥料 ； 水稻 ； 氮 ； 磷 ； 非點源汙染 ； 迴歸水 ； Chemical fertilizers ； Paddy field ； Nitrogen ； Phosphorus ； Nonpoint source pollution ； Return flow
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數十年來，化學肥料之使用已帶來許多負面影響，主要來自農耕施肥之氮、磷等營養鹽對水體之污染，集約施肥使氮、磷累積於地下及地面水體。水體遭受污染後產生諸多環境問題，包括藻類大量繁殖及水體之優養化，甚至對人類健康產生潛在性之威脅。而水稻為台灣主要作物，每年期作面積達25萬公頃以上，其施用之化學肥料占農業作物肥料消耗量中極大比例。 為了瞭解集水區上游水田施肥導致之非點源汙染，本研究以新竹縣新埔鎮實驗梯田為研究區域，藉由現地監測實驗田區完整耕作期間之地表、地下水體營養鹽濃度變化，評估分析農業迴歸水水質受施肥影響及其對集水區水環境所造成之汙染潛勢。水質監測結果顯示，水稻田施肥對於地表水體之影響，主要在於歷次施肥初期造成銨氮及硝酸鹽氮較明顯上升，其他時間則維持相對穩定之低濃度，約與灌溉水質相當。水井地下水質監測結果則顯示，銨氮、硝酸鹽氮與總磷濃度有較明顯之變化，與入滲至地下水井之路徑長度有關，水深愈深者，較不易受到田區施肥之影響，其檢測之營養鹽濃度也愈低。田區之氧化還原電位結果顯示，水稻田長期湛水導致土壤表面下1cm深度以下呈現還原狀態。研究結果進一步顯示，田區排水量及肥料管理為水稻田營養鹽污染潛勢之主要控制因子，可據此提出降低水田因施肥對於溼地生態與人體危害之水/肥份管理策略，包括減少基肥時期之排水量或截留天然降雨進行深水灌溉，迴歸水之重複利用以及合理化施肥等。此外，目前廣為世界各國重視或採用之SRI法(The System of Rice Intensification)，亦可加以研究應用。本研究成果可提供作為農業非點源汙染控制措施及評估農業迴歸水再利用之參考依據。
The use of chemical fertilizer has negatively impacted on environments in recent decades, mainly through water pollution by nitrogen and phosphate originating from agricultural activity. Intensive use of fertilizer for crops is responsible for nitrate and phosphate accumulation in both groundwater and surface waters. Water bodies polluted by nutrients create many environmental problems, including algal blooms and eutrophication in aquifers or in surface water bodies, and may pose potential hazards to human health. As a main crop and with the cultivation area about 0.25 million ha per year in Taiwan, Rice paddies account for a significant share of fertilizer consumption among agriculture crops. The aim of this study is to evaluate the fertilization of paddy fields impacting on return flow water quality. Water quality monitoring continued for two crop-periods around subject to different water bodies, including the irrigation water, drainage, and shallow groundwater was conducted in the Hsinpu experimental paddy field located at Hsinchu County, north Taiwan. The results indicated that obviously increasing of ammonium-N, nitrate-N and TP concentrations in the surface drainage water were observed during the early stage of fertilizer applications, but reduced to relatively low concentrations in the remaining period of cultivation. Groundwater quality monitoring from three observation wells with difference water levels showed that the observation wells with the more shallow water depth, the more significant variation of concentrations of ammonium-N, nitrate-N and TP could be observed, which means that the major difference between the high and low contamination potential of nutrient of groundwater is related to the length of percolation route in this area. The ORP values of around –200 mV were measured within the 1 to 10 cm depth, indicating that the redox potential of the most part of root zone is dominated by the reduced condition after long-term flooding. The monitoring analysis also showed that the potential pollution load of nutrient could be further reduced by well drainage water control and rational fertilizer management, such as deep-water irrigation, reuse of return flow, the rational application of fertilizers, and the SRI (The System of Rice Intensification) method are recommended. The results of this study can provide as an evaluation basis to formulate effective measures for agricultural non-point pollution control and the reuse of return flow.
工程學 > 土木與建築工程
工程學 > 市政與環境工程