[AHW32-02] The Processes Controlling Stream Water Chemistry at the Terrestrial-Aquatic Interface, Great Lakes Region, USA
キーワード：Stream water chemistry, Diagnostic tools of mixing models, Concentration-discharge analysis, End member mixing, Great Lakes Region
The diagnostic tools of mixing models (DTMM) and concentration-discharge (C-Q) analysis were applied to understand the processes that control stream water chemistry at the terrestrial-aquatic interface in Great Lakes region, USA. Streamflow discharge and chemical data from 2005 to 2008 at eight sub-catchments (ranging in size from 0.5 to 168 km2) were acquired from the US Geological Survey, including major ions, nutrients, and trace metals. The results of DTMM showed that specific conductance (SC), Ca2+, Mg2+, Na+, HCO3-, Si, Al, As, Ba, and U in stream water behaved conservatively and their concentrations resulted from mixing of two end-members in eight catchments. Significant (p < 0.01, n =10) C-Q power-law relationship occurred in all catchments for these conservative solutes above, further suggesting that the concentrations of these solutes in two end-members were relatively constant and their contributions to streamflow were persistent over time. Both DTMM and C-Q analysis indicated that K+, Cl-, SO42-, DON, and Mn were conservative only in some catchments mostly at larger scales but NO3-, P, Cr, Co, Cu, Fe, Pb, Ni, Se, and Zn were strongly impacted by chemical equilibrium in stream water in all catchments. These analyses enable us not only to develop two end-member mixing models with constant but distinct chemical signatures in end-members for all catchments at various scales but also to help understand the fate of nutrients and trace metals in stream water.