Hydrochemistry of the Amur River: Weathering in a Northern Temperate Basin

We report the dissolved major element, organic carbon, and delta C-13(DOC), delta C-13(POC), delta D, delta O-18, and Sr-87/Sr-86 composition of 19 summer samples from the Amur River. The Amur transported 2.6 Tg C/year of total organic carbon to the Sea of Okhotsk. The physical weathering rate (PWR) based on suspended particulate material was 13 (1.4-14) tons/(km(2) year), and the chemical weathering rate based on total dissolved solids was 7 (4.3-46) tons/(km(2) year). We further quantified the sources of the dissolved cations using an inverse model: rain accounted for 2 (0.6-5)%, evaporite 3 (0.7-7)%, carbonate 51 (29-74)%, and silicate 45 (25-64)%. The silicate weathering rate (SWR) in the Amur basin was 23 (15-98) x 10(3) mol/(km(2) year) or 0.67 (0.40-2.81) tons/(km(2) year), comparable to those of the Siberian rivers and the Mackenzie at higher latitudes. The SWR of the Amur was negatively correlated with elevation and relief, and positively correlated with runoff.