Seasonal Variations in the Carbonate System of the Razdolnaya River

Abstract

The values of pH, total alkalinity, humic substance, chlorophyll a were measured in water in the Razdolnaya R. within 13 months in 2013–2014 at a station near Razdolnyi Settl. Estimates of the carbonate system of river waters showed that the major portion of the year, the river water was a source of CO2 for the atmosphere with an annual emission flux of ~25 thousands tC/year. The chemical weathering of silicate rocks in the the Razdolnaya R. leads to withdrawal of atmospheric CO2. The mean annual export of the atmospheric CO2 in the form of dissolved inorganic and organic carbon by the Razdolnaya R. into the Amur Bay (the Sea of Japan) was 47 thousands tC/year. Therefore, the the Razdolnaya R. ecosystem in the study period absorbed CO2 (20 thousands tC/year). The period of 2003–2017 showed a tendency toward an increase in the export of alkalinity, dissolved inorganic and organic carbon by the Razdolnaya R.. Estimates of the rate of chemical weathering of rocks, composing the basin, lie within 12–24 t/(km2 year).