Fig. 3: Stable silicon isotopic composition of natural waters and amorphous silica from the Arctic.
From: Insights into silicon cycling from ice sheet to coastal ocean from isotope geochemistry
Seawater δ30SiDSi from the Fram Strait74, SW Greenland between Narsarsuaq and Nuuk regions53, the fjord system near Nuuk (Ameralik fjord and Nuup Kangerlua)13 (See Fig. 1), and SW Greenlandic glacial rivers8,10 against (a) the inverse of the dissolved silicon concentration ([DSi]); b natural logarithm of [DSi], where the gradient is the assumed fractionation during Si uptake under closed conditions. Dashed lines show a simple mixing model between a freshwater source ([DSi] = 25 μM; δ30SiDSi = +0.41‰), which are mean values from8,10, and a marine source ([DSi] = 4.8 μM; δ30SiDSi = +1.78‰) from53. Grey bars show the range of δ30SiASi from across the Arctic. Note that while DSi concentrations are generally measured colorimetrically (i.e., “truly dissolved” silicic acid), δ30SiDSi is generally measured on filtered samples (commonly either 0.2 or 0.45 μm) using inductively-coupled plasma mass spectrometric methods, and care must be taken to ensure that there is no fine particulate matter present that influences the measurement28.
