台灣農業非點源污染

Abstract

台灣飲用水水源有三分之二來自水庫，水庫水質影響民眾健康很大，而水庫水質優養造 成藻類過多之繁殖，不但增加原水有機碳含量和三鹵甲烷潛勢，也促使毒藻的過量生長。如 何減少水庫優養保護飲用水安全，是當今環保界最重要之課題。台灣水庫營養鹽的來源有 90% 以上來自非點源污染，除了林地外，農業活動是最重要的來源。本文主要目的是把水庫集水 區較重要的農業非點源污染調查結果加以統計並以模式分析，提供茶園、山葵園、檳榔園、 放山雞養雞場、休閒農場和高粱與小麥輪種農田等非點源污染輸出係數，供從事農業經營者 參考。研究顯示放山雞養雞場氮、磷輸出負荷很高，約為一般農地 10 倍以上；除養雞外，全 年單位面積輸出 TN 負荷為高山茶園 (平均 24 kg/ha)、檳榔園 (平均 8.3 kg/ha)、高粱田 (5.3 kg/ha)、休閒農場 (5.1 kg/ha)及山葵園 (3.3 kg/ha)；TP 部分則依序為山葵園 (6.7 kg/ha)、檳榔 園 (平均 1.2 kg/ha)、休閒農場 (1.0 kg/ha)、高粱田 (0.96 kg/ha)及高山茶園 (平均 0.24 kg/ha)。 Reservoirs are the most important drinking water sources in Taiwan, however, most were eutrophicated due to nutrient overenrichment from watershed nonpoint sources (NPS). Except for the undistributed forest which occupied the largest area of the reservoir watershed, agriculture activities are the most important source of NPS pollution. Based on the NPS monitoring program enabled by Environmental Protection Administration and Water Resources Agency since 1995, data from rural catchments were selected to estimate the event mean concentrations (EMCs) and unit NPS loads. Based on those single-event data, the annual NPS loads for those studied catchments were derived by appropriate models to evaluate the NPS pollution from agriculture in Taiwan. The results indicated that the nitrogen and phosphorus loads from free-ranged chicken farm (FRCF) were almost 10 times to those from other rural catchments. Except for the FRCF, the average annual loads for recreation fruit farm, high mountain tea farm, betel palm farm, wasabi farm and broomcorn farm respectively are 5.1, 24, 8.3, 3.3 and 5.3 kg total nitrogen per hectare; 1.0, 0.24, 1.2, 6.7 and 0.96 kg total phosphorus per hectare.