Environmental Engineering Reference
In-Depth Information
extract the desired metal. Next, the well is flooded with
water, which is pumped to the surface, where the de-
sired metal is removed. The water is recycled.
Currently, more than 30% of all copper produced
worldwide, worth more than $1 billion per year, comes
from such
biomining.
If naturally occurring bacteria
cannot be found to extract a particular metal, genetic
engineering techniques could be used to produce such
bacteria.
On the down side, microbiological ore processing
is slow. It can take decades to remove the same amount
of material that conventional methods can remove
within months or years. So far, biological mining meth-
ods are economically feasible only with low-grade ores
for which conventional techniques are too expensive.
toy box of nature—atoms and molecules.... The pos-
sibilities to create new things appear limitless.” You
might want to consider this rapidly emerging field as a
career choice.
So what is the catch? What are some possible un-
intended harmful consequences of nanotechnology?
As particles get smaller, they become more reactive
and potentially more toxic because they have large
surface areas relative to their mass. Also, nanosize par-
ticles could breach some of the natural defenses of our
bodies. They could easily reach the lungs and from
there migrate to other organs, including possibly the
central nervous system and the bloodstream.
In 2004, Eva Olberdorster, an environmental toxi-
cologist at Southern Methodist University, found that
fish swimming in water loaded with buckyballs expe-
rienced brain damage within 48 hours. Little is known
about how buckyballs and other nanoparticles behave
in the human body. Even so, factories are churning out
buckyballs and these and other nanoparticles are start-
ing to show up in products ranging from cosmetics to
sunscreens and in the environment.
Many analysts say we need to take two steps be-
fore unleashing nanotechnology more broadly.
First,
we must carefully investigate its potential ecological,
health, and societal risks.
Second,
we must develop
guidelines and regulations for controlling and guid-
ing its spread until we have better answers to many
of the “What happens next?” questions about this
technology.
Science Case Study: Using Nanotechnology
to Produce New Materials
Building new materials from the bottom up by
assembling atoms and molecules has enormous
potential but could have potentially harmful
unintended effects.
Nanotechnology
uses science and engineering at
the atomic and molecular levels to build materials with
specified properties. It involves finding ways to
manipulate atoms and molecules as small as 1-100
nanometers—billionths of a meter—wide. For compar-
ison, your unaided eye cannot see things smaller than
10,000 nanometers across and the width of a typical
human hair is 50,000 nanometers.
This atomic and molecular approach to manufac-
turing uses abundant atoms such as carbon, oxygen,
and hydrogen as raw materials and arranges them to
create everything from medicines and solar cells to
automobile bodies. Ideally, this bottom-up process
occurs with little environmental harm and without de-
pleting nonrenewable resources. One example is the
creation of soccer ball-shaped forms of carbon called
buckyballs.
Nanotechnology scientists entice us with visions
of a
molecular economy.
They ask us to imagine a super-
computer the size of a sugar cube that could store all
the information in the U.S. Library of Congress, bio-
composite materials smaller than a human cell that
would make your bones and tendons super strong, de-
signer molecules that could seek out and kill only can-
cer cells, and windows, kitchens, and bathrooms that
never need cleaning. The list could go on.
This research is in its early stages and tangible
results remain a decade away. Nevertheless, nano-
technology has already been used to develop stain-
resistant, wrinkle-free materials for pants and sun-
screens that block ultraviolet light.
Nobel laureate Horst Stormer says, “Nanotechnol-
ogy has given us the tools...to play with the ultimate
Science, Economics, and Politics: Getting
More Minerals from the Ocean
Most minerals in seawater cost too much to
extract, and mineral resources found on the
deep ocean floor are not being removed
because of high costs and squabbles over who
owns them.
Ocean mineral resources are found in seawater, sedi-
ments and deposits on the shallow continental shelf,
hydrothermal ore deposits (Figure 12-15), and man-
ganese-rich nodules on the deep-ocean floor.
Most of the chemical elements found in seawater
occur in such low concentrations that recovering them
takes more energy and money than they are worth.
Only magnesium, bromine, and sodium chloride are
abundant enough to be extracted profitably at current
prices with existing technology.
Deposits of minerals (mostly sediments) along
the continental shelf and near shorelines are signifi-
cant sources of sand, gravel, phosphates, sulfur, tin,
copper, iron, tungsten, silver, titanium, platinum, and
diamonds.
Rich hydrothermal deposits of gold, silver, zinc,
and copper are found as sulfide deposits in the deep-
