淡水河流域中磷物種的分布與型態變化

Abstract

磷，是生物成長主要的營養鹽之一，磷循環在海洋環境中非常重要，在淡水與海水中磷為浮游植物生長的限制因子。本研究藉由正壓過濾以及交流過濾與消化反應來探討淡水河流域中磷的物種與相態。 總溶解態磷(TDP)濃度由高至低依序為基隆河、大漢溪、淡水河、新店溪。都會區域受到人為活動影響，輸入量平均約增加十倍。總溶解態磷主要為無機磷 (DIP ~60 %)，其中接近三成無機磷以膠體型態存在。水體與顆粒體之間的分布係數log Kd約為4.7±0.5 L/kg。河口感潮段地區呈現非守恆混合行為，額外添加約125 %，其中來自顆粒脫附量約佔一成，其餘可能為沈積物再懸浮作用影響。輸出至海洋的溶解磷通量為27,000 mol/day(0.9 tons/day)，其中膠體無機磷(DIPc)約佔三成，過往被認為是無機磷酸鹽，此現象會嚴重高估磷酸鹽(DIPf)所佔比例，導致全球海洋生物地球化學平衡及生態模式計算極度謬誤。

Phosphorus (P) is an essential nutrient for all living organisms. It is a key player in biogeochemical cycle. In freshwater and seawater, phosphorus is the limiting factor for phytoplankton growth. In this study, various filtration methods and chemical digestion method were used to understand phosphorous speciation and fractionation in waters of Danshuei tributary-estuary. In the Danshuei tributary-estuary, total dissolved phosphorus (TDP) was mainly as inorganic phosphorous, average 60 %, in which, nearly 30% are in fraction of ≤1 kDa. As flow through the metropolitan area, the amount of phosphorus increase over 10 times due to anthropogenic activities. The particle-water partition coefficients of dissolved and particulate phosphorous yield log Kd = 4.7±0.5 L/kg, similar to other studies. Non-conservative mixing behavior were observed in tidal mixing zone, with addition of 122 % extra input of TDP, which nearly 10% was from particle desorption, other may due to benthic particle re-suspension. The export flux of TDP was about 27,000 mol/day (0.9 tons/day), in which, colloidal fraction account for more than 30%. This phenomenon would seriously cause overestimation of previously thought of phosphates fluxes to the ocean, and major flaws in the modeling efforts of biogeochemical balance and ecosystem for the global ocean.