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

We report the dissolved major element, organic carbon, and δ¹³C_DOC, δ¹³C_POC, δD, δ¹⁸O, and ⁸⁷Sr/⁸⁶Sr 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/(km² year), and the chemical weathering rate based on total dissolved solids was 7 (4.3–46) tons/(km² 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) × 10³ mol/(km² year) or 0.67 (0.40–2.81) tons/(km² 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.