hUMaN iMpaCts oN the Biosphere 481hoW do human activities affect Water
supplies and solid Wastes?- Human water supplies are threatened by overuse and pollution.
Our activities also generate trillions of tons of solid wastes
each year. - Landfills are rapidly filling up, and land for new ones is
becoming scarcer. - Recycling helps reduce solid waste and conserve resources.
taKe-Home messaGeIncinerators can add heavy metals and other pollutants
to the air and leave a highly toxic ash that must be dis
posed of safely. Land that is both available and acceptable
for landfills is scarce and becoming scarcer. All landfills
eventually leak, posing a threat to groundwater supplies.
That is one reason why communities increasingly take the
“not in my back yard” (NIMBY) approach to landfills. For
some highly populated areas, the “solution” has been to
ship much of their garbage to rural areas (often in other
states or countries) or dump it in the ocean.
Some components of trash may stay around for decades,
especially if they contain plastic. Plastic bags may still be
intact after 40 or 50 years, and parts of a disposable diaper
will last more than 100 years.
On the plus side, about onethird of the total U.S. trash
is recycled (Figure 25.15). That still leaves many millions
of tons of plastic containers and glass bottles for society to
deal with. To reduce the impact of plastic trash, consumers
can buy fewer disposable items such as razors and avoid
buying plastic when other, less environmentally harmful
products exist. If plastic is used, it can be recycled. These
days most communities make recycling easy with curbside
pickups or recycling centers. Many grocery stores and
other businesses provide free bins where plastic bags also
can be recycled.
Figure 25.14 Industrial wastes polluted Lake Erie. A steel mill
in Lackawanna, New York, discharged industrial wastes into
Lake Erie until 1983, when the mill was closed. Major efforts to
clean up Lake Erie have been under way.
Laurence Lowry/Science SourceA
Bill Bachmann/Science SourceFigure 25.15 Recycling is an important part of efforts to
manage solid wastes. A Recyclable material includes many
plastics, glass containers, metal cans, and often other items.
Many communities have special facilities for recycling items
such as batteries, computers, and paint cans, which contain
hazardous substances such as mercury and lead. B A garbage
barge laden with trash. Most unfortunately, this barge is probably
headed for the open ocean where the trash will be dumped.B
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