Environmental Engineering Reference
In-Depth Information
water use around the Mediterranean, with a single large construction
project as a possible triggering event, leading by a series of perturbations
of natural oceanic and atmospheric circulation patterns to severe and dis-
ruptive climate changes in highly populated areas, with concomitant
economic and social costs. As is frequently the case with environmental
perturbations, the economic and environmental costs and benefits are
differentially realized across classes of people, countries, economic sec-
tors, and geographic regions.
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Egypt benefits from the Aswan High
Dam; Europe and Canada may face adjustment costs. How can institu-
tional, scientific, ethical, and technological systems be evolved to manage
such situations? And, when the system is considered as a whole, where is
(are) the best place(s) to intervene to mitigate forcing functions, system
response, and/or costs?
IRON-ENRICHED PHYTOPLANKTON BLOOMS
This option builds on the basic ecological principle that most communities
are limited in their growth by a single factor. In this instance, growth of
oceanic phytoplankton populations is limited by iron, so artificially intro-
ducing iron into oceanic systems would result in phytoplankton blooms
which would absorb carbon, then die. At least some of the resulting car-
bonaceous material would sink to the bottom of the ocean, thereby
depositing the carbon in a long-term sedimentary sink.This phenomenon
has indeed been verified in tests on the open ocean.
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These experiments
also demonstrated, however, that the iron tended to precipitate out of solu-
tion rapidly, potentially reducing the effectiveness of this mechanism for
capturing carbon.
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In addition, the makeup of the planktonic community
changed as a result of iron fertilization,
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as did emissions of dimethyl sul-
fide (DMS) production by phytoplankton, which could lead to a cooling
effect on the climate. However, even if this work is at a preliminary stage,
it begins to create the knowledge base that will be needed if this option is
to become part of a human-engineered carbon cycle. Of course, the gaps
in the necessary knowledge are also apparent even at this early stage. How-
ever, unlike the proposal for a dam across the Mediterranean, this option
can be explored at small scales, and, if justified, could be implemented
incrementally, perhaps in locations where disruption of existing communi-
ties is minimal.
