重金屬離子隨著工業及家庭污水排放至河川，河水中重金屬離子因物理沉降、化學混凝、化學沉澱及生物吸附吸收等作用沉降累積於河川底泥基質中。重金屬累積於河川底泥基質之作用方式為有機物鍵結、鐵錳氧化物鍵結、碳酸鹽鍵結等，其中有機物之鍵結為重金屬蓄積於底泥之主要方式。有機物含有許多官能機(如-COOH 、-OH等)對於帶正電荷之重金屬離子具有強鍵結能力，重金屬離子將隨著腐質酸、黃酸自植物組織中流失並存在水體中，部分之腐質酸、黃酸將和底泥顆粒吸附構成底泥中有機態重金屬。種植作物於受重金屬汙染之土壤或自河川浚堞之廢棄河川底泥為目前相當流行之重金屬復育法，即看中於植物體中有機物擁有許多官能基具有和重金屬離子之強錯合能力。本計畫針對遭受不同重金屬及有機物污染程度之鹽水溪、曾文溪、急水溪、朴子溪及北港溪河川底泥中各種重金屬含量（銅、鉻、鋅、镍、鉛、鈷、錳及鐵）和河川底泥中有機物含量間關係性進行探討，發現重金屬含量和河川底泥中有機物含量呈現正相關，且相關係數高達0.95以上。同一河川底泥中有機物含量高，則相對應累積於底泥中之重金屬含量就高。可以經驗公式表示為
底泥中重金屬含量(mg/kg)＝A＋B×底泥中有機物含量(%)
此經驗公式證明底泥中高濃度有機物是決定底泥是否能吸附留滯河水中重金屬離子之重要因素。 Heavy metal ions were discharged into the river water with industrial waste. The heavy metal ions would deposit and accumulate in river sediment matrix by physical-chemical seposition, chemical coagulation, and bioabsorption etc. The fraction of heavy metals existed in river sediment matrix can be divided into carbonate Fe-Mn oxides, and organic matters etc. The heavy metal ions with positive charge will have strong binding capacity with function groups (eg. –COOH, -OH) in organic matters. The heavy metals binded with humic and fulvic acids will discharge into the river in the destruction of plant tissue, some of the them will absorpt with inorganic solid into sediment. The remediation of heavy metals in polluted soil and dredged river sediment with plants are popular depending on the strong binding capacity of heavy metal with organic function groups in plant. The purpose of this study focuses on the correlation between heavy metals(Cu, Zn, Co, Pb, Ni, Cr, Mn, and Fe) and organic matters in five river sediments (The Yenshui River, Tsengwen River, Chishui River, Potzu River and Peikang River). The positive linear correlations were found with 0.95 over. High organic matters coincide with high heavy metal concentration in sediment of each river. The empirical equation can be used to express the correlation as follow.
Heavy metals in sediment (mg/kg)＝A＋B × organic matters in sediment (%)
Organic matters concentration was main factor for the accumulation of heavy metals in river sediment, when river water polluted with heavy metal ions.
