Publication Type:
Journal Article
Source:
Anthropogenically enhanced fluxes of water and carbon on the Mississippi River, Volume 451, p.449-452 (2008)
Abstract:
The water and dissolved inorganic carbon exported by rivers are
important net fluxes that connect terrestrial and oceanic water and
carbon reservoirs1. For most rivers, the majority of dissolved inorganic
carbon is in the form of bicarbonate. The riverine bicarbonate
flux originates mainly from the dissolution of rock minerals by
soil water carbon dioxide, a process called chemical weathering,
which controls the buffering capacity and mineral content of
receiving streams and rivers2. Here we introduce an unprecedented
high-temporal-resolution, 100-year data set from the
Mississippi River and couple it with sub-watershed and precipitation
data to reveal that the large increase in bicarbonate flux that
has occurred over the past 50 years (ref. 3) is clearly anthropogenically
driven. We show that the increase in bicarbonate and water
fluxes is caused mainly by an increase in discharge from agricultural
watersheds that has not been balanced by a rise in precipitation,
which is also relevant to nutrient and pesticide fluxes to the
Gulf of Mexico. These findings demonstrate that alterations in
chemical weathering are relevant to improving contemporary biogeochemical
budgets. Furthermore, land use change and management
were arguably more important than changes in climate and
plant CO2 fertilization to increases in riverine water and carbon
export from this large region over the past 50 years.
