Anthropogenic influences on riverine fluxes of dissolved inorganic carbon to the oceans

Abstract

Bicarbonate ((Formula presented.)), the predominant form of dissolved inorganic carbon in natural waters, originates mostly from watershed mineral weathering. On time scales of decades to centuries, riverine fluxes of (Formula presented.) to the oceans and subsequent reactions affect atmospheric CO2, global climate and ocean pH. This review summarizes controls on the production of (Formula presented.) from chemical weathering and its transport into river systems. The availability of minerals and weathering agents (carbonic, sulfuric, and nitric acids) in the weathering zone interact to control (Formula presented.) production, and water throughput controls (Formula presented.) transport into rivers. Human influences on (Formula presented.) fluxes include climate warming, acid precipitation, mining, concrete use, and agricultural fertilization and liming. We currently cannot evaluate the net result of human influences on a global scale but (Formula presented.) fluxes are clearly increasing in some major rivers as shown here for much of the United States. This increase could be partly a return to pre-industrial (Formula presented.) fluxes as anthropogenic acidification has been mitigated in the United States, but elsewhere around the world anthropogenic acidification could be leading to decreased concentrations and fluxes.