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Bdale Envir Ch 14 – Water Resources and Water Pollution - page 5 / 7

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14-7 Ocean water pollution

“oceans are the ultimate sink for much of our waste”

oceans dilute a lot of pollution, and some forms of marine life may be “more resilient” to pollution than previously thought

coastal areas “bear the brunt” of ocean pollution (Fig 14-26)

why?

40% of world’s population lives within 100 km (60 miles) of a coast, so there are a lot of people in this area

world’s 15 largest metro areas (each > 10,000,000) are on coasts

coastal areas growing fast

what are some of the sources ?

Municipal sewage & waste, sometimes untreated

Runoff of fertilizer, etc

Deposition from atmosphere

These all bring in nutrients that promote “explosive” algae growth that is ultimately harmful to fish, seafood, birds.  

Good example of this is Fig 14-28, depleted oxygen zone that forms every year off the mouth of Mississippi R., fed by a huge drainage basin in middle of U.S.

Miller cites big problems in Chesapeake Bay Fig 14-29, where there is much pollution due to large population, but only 1% of waste entering the Bay actually gets “flushed” into the ocean.

However, an integrated coastal mgmt program has started to achieve “impressive” results, reducing nitrogen and phosphate

What pollutants do we dump into the ocean?

US has stopped dumping industrial waste offshore, but many countries still do it.

But we still dump “dredge spoils” …these are sediments dredged from bottoms of rivers and harbors to maintain shipping channels….Maintenance of shipping channels is a major task of the US Army Corps of Engineers

Other countries also dump sewage sludge (waste material that is removed from wastewater at sewage treatment plants), but US stopped doing this in 1992.

Effects of oil upon the ocean

The most dramatic incidents (tanker spills and well blowouts) are not necessarily the most damaging…..Miller cites releases during normal oil well operations, pipeline leaks, and washing of oil tankers as more important.

Other sources are natural, such as seeps.

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