大甲溪流域之果園及農田全年使用各種農藥種類及數量甚高。而石岡水壩所儲備之河水除供灌溉之用外，尚有供應大臺中地區百萬人口及臺中港船舶飲用水之目標，因此河水受到農藥污染之程度，備受政府及民眾之關注。本研究之採樣來自大甲溪及兩岸農田，地點為東勢、石岡、后里、大甲及梨山果園（當對照之用）。時間自民國68年3月至同年底。由結果顯示梨山果園土壤、大甲溪河水、河床土壤及稻田灌溉水皆未含殘留巴拉刈。但水田及田埂土壤之巴拉刈殘留量則極高，尤以東勢地區為最，最高者分別達到6.20及10.00ppm。其次為后里，最高者分別達到3.00及3.75ppm，而大甲及石岡則較低。此種趨勢顯示東勢地區用藥量較多之故。大甲溪流域農田土壤含粘粒成分在7.0至24.5%之間。而此類粘粒屬2:1晶格型之伊來石類(I11ite)，對巴拉刈具有極強之吸附力，土粒與藥劑一旦互相結合則極難分離，致使藥劑不易被微生物及其他環境因子進行有效分解，造成土壤受巴拉刈之嚴重污染。

Applications of pesticide chernicals in orchard lands and ricepaddy fields along the Tachia River have been extrernely heavy.The possibility of water and soil pollutions by pesticides as aresult of such application has been raised repeatedly. The rnainreason of such public concern is rnostly due to the fact that thefunction of the Shihkang Reservoir , which was cornpleted threeyears ago , was partially designed to supply drinking water forTaichung rnetropolitan area and the Taichung Harbor , includingocean liners.Sarnples of water , soil and sedirnents were collected frornthe river and rice paddy fields of four towns along the river.Soil sarnples frorn Lishan orchard , an area never using suchherbicide , were also analysed for the purpose of cornparison.The study covered the whole period of March thru Decernber,1979. Results revealed that none of the waters and sedirnentscontained detectable quantity of paraquat. However , soils frornrice paddy fields and paddy levees of all four towns were heavilycontarninated by this herbicide , particularly those frorn Tungshihand Holi. The highest residues detected in the soils of rice paddyfield and levee were 6.2 and 10.0 pprn respectively for Tungshihand 3.0 and 3.75 pprn respectively for Holi. Soils frorn all samplingsites contain 7.0 to 24.5% of clay particles.The clay material is considered to belong to Illite group,which can firmly absorb cations such as paraquat and prevent itfrom being degradated.