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by Nick Carne
July 31,
2019
from
CosmosMagazine Website
A controlled burn in Burkina Faso, West Africa.
The
impact may have been felt far afield.
DE AGOSTINI PICTURE LIBRARY / GETTY IMAGES
It may
even have an impact
in the Southern
Ocean,
new study
finds...
Smoke from widespread biomass burning in Africa - mostly the result
of land clearing, brush fires and industrial combustion emissions -
may be the most important source of the phosphorus that
fertilizes the Amazon rainforest, new research shows.
Nutrients found in atmospheric particles, called
aerosols, are transported by winds
and deposited on land and sea, where they stimulate the productivity
of marine phytoplankton and terrestrial plants leading to the
sequestration of atmospheric carbon dioxide.
It has long been assumed that Saharan dust is the main fertilizer to
the
Amazon Basin and the
Tropical Atlantic Ocean, says
Cassandra Gaston from the University of Miami in the US, but her
work with colleagues from UM and the ATMO Guyane in French Guiana
suggests otherwise.
The findings (African
Biomass burning is a substantial Source of Phosphorus deposition to
the Amazon, Tropical Atlantic Ocean and Southern Ocean)
are published in the journal Proceedings of the National Academy
of Sciences.
The researchers analyzed aerosols collected on filters from a
hilltop in
French Guiana, at the northern edge
of the Amazon Basin, for mass concentrations of windborne dust and
their total and soluble phosphorus content.
They then tracked the smoke moving through the atmosphere using
satellite remote sensing tools to understand the long-range
transport of smoke from Africa during time periods when elevated
levels of soluble phosphorus were detected.
From this they were able to estimate the amount of phosphorus
deposited to the Amazon Basin and the global oceans from African
biomass burning aerosols using a transport model.
"To our surprise, we
discovered that phosphorus associated with smoke from southern
Africa can be blown all the way to the Amazon and, potentially,
out over the Southern Ocean where it can impact primary
productivity and the drawdown of carbon dioxide in both
ecosystems," says lead author Anne Barkley.
Gaston says there is a
lot that we don't understand regarding how aerosols affect
radiation, clouds and biogeochemical cycles, which,
"impedes our ability
to accurately predict future increases in global temperature".
"These new findings have implications for how this process might
look in the future as combustion and fire emissions in Africa
and dust transport patterns and amounts change with a changing
climate and an increasing human population."
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