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Pnumber lor.
memt
writting
Assigment
5.15
by email
CALIFORNIA STATE UNIVERSITY, FULLERTON
DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING
EG-CE 428L Hydraulics Laboratory
Pue
Effect of PCBs in Water Systems
Background
environmental contaminants found in air, water, sediments, and soils around the globe. PCBs
Polychlorinated biphenyls (PCBs) are synthetic organic chemicals that are widespread
are not simple compounds, but are complex mixtures of individual chlorobiphenyls that
contain 1 to 10 chlorine atoms. They were manufactured in the United States from 1929 to
1977. PCBs are a group of synthetic organic chemicals that contain 209 individual
compounds (known as congeners) with varying harmful effects. Some commercial PCB
mixtures are known in the United States by their industrial trade name, Arochlor. The name,
Arochlor 1254, for example, means that the molecule contains 12 carbon atoms (the first two
digits) and approximately 54% chlorine by weight (second two digits). Their low reactivity
and high chemical stability made them useful in a number of industrial applications,
particularly in electrical transformers and capacitors. These same qualities make many
individual chlorobiphenyls slow to degrade upon their release to the environment relative to
most other organic chemicals. PCBs bind strongly to organic particles in the water column,
atmosphere, sediments, and soil. The deposition of particle-bound PCBs from the atmosphere
and the sedimentation of them from water are largely responsible for their accumulation in
sediments and soils.
As PCBs move through the environment, the absolute and relative concentrations of
individual chlorobiphenyls change over time and from one environmental medium to another
because of physical and chemical processes and selective bioaccumulation and metabolism
by living organisms. These processes result in mixtures that are substantially different from
the original mixtures that were released to the environment. The identification, quantification,
and risk assessments are complicated by these changes in the composition of the PCB
mixtures.
Numerous bodies of water in the United States contain PCB-contaminated sediments that
pose current and potential future risks. PCBs in sediments can enter the aquatic food chain,
thus contaminating aquatic organisms, including fish, and ultimately placing humans and
wildlife at risk of adverse health effects from consumption of these organisms.
Acknowledging the human health risks posed by exposure to PCBs at many contaminated
sites, some state health and environmental agencies have issued fish and wildlife
consumption advisories to caution sport fishers and hunters and their families against eating
the fish or wildlife from these sites. The risks of PCB-contaminated sediments, however,
extend beyond direct health effects to humans and wildlife. For example, the establishment of
fish and wildlife advisories might result in economic hardship for people who rely on the
consumption of fish and in erosion of culture for native communities that have a fishing
tradition. The presence of contaminated sediments might curtail the recreational use of the
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body of water for swimming or fishing or lead to restrictions on maintenance dredging,
thereby potentially affecting water-borne transportation.
In recent years, substantial progress has been made in the scientific understanding of the
dynamics of PCBs in the environment and the effects of PCBs on humans and ecosystems.
However, important issues remain regarding the overall risks of PCB-contaminated
sediments and the management strategies best suited to reduce them.
The management of PCB-contaminated sediments has been the subject of much scientific
enquiry, technical innovation, regulatory confusion, public debate, and litigation. At
contaminated sites around the country, management plans have been proposed, implemented,
or completed, with varying levels of satisfaction from the involved parties. PCBs have been
associated with a variety of risks to humans and ecosystems.
2 page backgroud Sigleline size 12
Based on the work published, you need to submit a page writeup (not including the
references) that addresses the various issues of pcbs in sediments beneath water and pcbs in
sediments. You can find some direct literature relating to the pubs in Hudson river
(http://www.clearwater.org/pcbs/index.html, http://www.epa.gov/hudson/). A web search can
give you many other leads of information for Hudson river. The information present in the
above websites will give you a good overview of the pcb issues in water bodies.
Your writeup, after a background introduction should address to the following questions. You
need to cite published references for all your answers and some data, if available.
Task description
21099,
1. Do pcbs stick to the sediments in water or do they penetrate into the sediments? If
they stick, is the coating uniform across the perimeter?
2. Do pcb coated sediments release/transfer pcbs to water? If so, is this release rate
constant? On what factors does this transfer rate depend on? Does it depend on flow
velocity, water temperature, pH, depth of water, pcb concentration in the sediment?
3. When a sediment is suspended from the river bottom and is relocated to a new
location, will its pcb concentration increase or decrease? Why does it increase or
decrease? Is there any definite data that you can support your answer with?
PCBs in water systerms
Reference 5 refeance MLA format
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