Salt wedge – requires a rapidly moving river. Influence of tidal flow is
negligible. Entrainment of salt
wedge at base of river water causes one-way mixing. Columbia, Hudson and Mississippi Rivers
Well-mixed estuaries – strong tidal mixing and lower
river flow. Salinity uniform with
depth and increases seaward.
Examples: shallow
estuaries such as Chesapeake and Delaware Bays
Partially mixed – strong net seaward flow of fresh
water, with tidal mixing at base:
landward flow of seawater (advection) at depth. deeper estuaries like SF Bay and
Puget Sound
Fjords- deep with small surface-area to voume ratios.. Little influx of seawater at depth with most net flow in surface layer. Bottom layer often stagnant
Circulation patterns very important environmentally. Net circulation out (at the top, including land-generated pollutants) and in (at the bottom, including nutrients) is very important Measured by current meters at different depths
Volume/seaward flow rate = flushing time. High flushing rates occur in smaller estuaries where net circulation is rapid. Here, potential for pollution is less than in larger estuaries with sluggish circulation, such as Chesapeake Bay
Read case histories of Chesapeake and SF Bays (the most-modified estuary in the U.S.). Especially interesting to note that in spite of the CWA of 1972, pollution in the Chesapeake is nearly unabated. Federal permit systems of enforcement are largely self-policing efforts, where dischargers set their own limits. This is a real problem, because of no incentive for compliance.
I’ll ask a question on this topic on exam.
Ocean Dumping Act – 1972 (Marine protection, research and sanctuaries act)
Prohibits dumping in US waters (within 3 miles of shore) except by EPA permit,
Note that the US EEZ extends 200 nautical miles offshore. (1 nautical mile = 1.15 miles = 1 minute of arc on the Earth’s surface.)
Dumping sites are specified by EPA. The law does not include sewage from vessels or oil. Works together with the London Dumping Act, signed by 85 nations.
Amended in 1977 require that dumping of municipal sewage sludge or industrial wastes which unreasonably degrade the environment cease by December 1981. (However, that deadline was not achieved, and amendments passed in 1988 extended the deadline to December 1991. By 1992, dumping of sewage sludge ceased
Also in 1992, Congress amended the Act to permit states to adopt ocean dumping standards more stringent than federal standards and to require that permits conform with long-term management plans for designated dumpsites, to ensure that permitted activities are consistent with expected uses of the site.
Some
of the waste material may be transported to and dumped into the ocean by DOE
under conditions stipulated in a permit issued by the EPA or the Corps of
Engineers (COE or the Corps), depending upon the type of waste involved. Ocean
dumping, however, is only possible if no other reasonable alternatives, such as
landfilling, are available.
Virtually all ocean dumping that occurs today is dredged material – controlled by Corps of Engineers, not EPA. more than 400 million cubic yards of sediment is dredged annually from U.S. waterways, and each year approximately 60 million cubic yards of this material is disposed of in the ocean at designated sites. EPA does develop criteria to ensure that dredged material doesn’t cause environmental degradation.
Disposal by means of a pipe,
regardless of how far at sea the discharge occurs, is regulated by the Clean
Water Act. Clean Water Act of 1972 protects estuaries and
works hand-in-hand with Ocean dumping act.
The dumping act also authorizes research regarding effects of dumping on environment.
A problem exists with dredged material. The sediment is generally contaminated with high levels of toxic chemicals, which can undergo exchange with the water. As of 2003, about 400 million cubic yards of sediment are dredged each year by federal, state and local governments, and private interests such as marinas, to keep the nation's waterways open. One method for disposing of this dredged material is dumping it in the ocean. Some of the material is contaminated by pollutants and does not meet the environmental criteria, which allow it to be dumped into the ocean.
The Shore Protection Act of 1988 (SPA) addresses waste disposal practices at coastal waste transfer stations as well as off-shore mineral exploration mining and drilling platforms. The SPA requires that all vessels used in the transport of solid waste, as well as the on-loading and off-loading facilities involved in these operations, are permitted and that solid wastes are not deposited in coastal waters.
Discharge of wastewater – regulated by CWA of 1972.
Since then, through the year 2000, levels of total suspended solids,
biological oxygen demand substances, oil and grease, and heavy metals have all
diminished drastically.
Boston Harbor was a notable exception until 1985, when requests for extensions for cleanup were finally denied. The Deer Island sewage treatment plant construction was begun in 1989 and online in 1995. Modeling has suggested that “water quality in Boston Harbor should improve significantly with little or no adverse impacts on water quality in Massachusetts or Cape Cod Bays. The reason that the outfall will have little impact of Massachusetts Bay and Cape Cod water quality is due, in part, to the fact that the outfall plume will be trapped below the pycnocline of the water column during the summer months. Therefore, nutrient inputs to the surface waters of northern Massachusetts Bay will not be increased as a consequence of outfall relocation. This is an important finding, in that it suggests that nutrient reduction or removal at the MWRA wastewater treatment facility is not required in order to maintain present water quality in Massachusetts and Cape Cod Bays.” Of course, deeper water currents will move the effluent away from this area into other localities where it could conceivably do harm. Extensive monitoring program by Batelle Institute at discharge site into Massachusetts Bay. Benthic communities and nutrient dynamics, toxicants, species health and effects on human consumers, and tracking of effluent are all monitored.
Southern CA Bight is another area of concern. Most contamination of waters in the
bight have been from four large treatment plants. Thanks to the CWA, this point source pollution has been
drastically reduced.
Flotables –
The discharges of harmful substances and other items from
ships or vessels are addressed in the International Convention for
Prevention of Pollution from Ships, or MARPOL Agreement. The MARPOL Agreement was enacted into
U.S. law by the Act to Prevent Pollution from Ships (APPS).
To address land-based sources of plastic materials in the marine environment, the APPS was amended in 1987 by the marine Plastic Pollution Research and Control Act (MPPRCA). As required under the MPPRCA, EPA completed a study of the sources, fates and effects of plastics in the marine environment and on the solid waste stream. The study showed a number of sources of marine debris: ships, offshore oil platforms, fishing boats, combined sewage overflows, storm drains and litter from human activity on land. No international enforcement.
Enforcement
“enforcement has a significant role in EPA's pollution control programs, but we have found it to be resource intensive. Therefore, we are also moving forward on other fronts, such as voluntary compliance and public education, in order to effectuate an holistic approach to protecting our oceans. We think that we are making significant progress as we have stopped industrial waste dumping in the ocean, we are not permitting incineration at sea, and dumping of sewage sludge will soon end. However, other tasks remain. Our focus in the years ahead will be on proper disposal of dredged materials and controlling pollution caused by marine debris. Enforcement will be utilized in these areas where appropriate. It has been, and will continue to be, an effective tool to assist in efforts to protect our ocean environment.”
Dumping at sea is very difficult to detect and even more difficult to enforce.
Toxicants:
Heavy metals, DDT, and PCB’s (polychlorinated biphenyls), which are mutinogenic and carcinogenic. PCB’s strictly regulated by the Toxic Substances Control Act of 1976 (for levels above 50 ppm), and DDT has been banned by the EPA since 1971. Even chlorine in drinking water and chlorine added to sewage effluent as a bactericide can react with organic compounds in water to form chlorinated hydrocarbons toxic in the marine environment
often monitored by studying mussels and oysters, which have an unusual ability to adsorb and concentrate contaminants
Gulf of Mexico Dead Zone –
February to summer peak to fall decline when storms mix the water. Mobile organisms move out. Slow moving bottom dwellers succumb. 80% of the water column is affected. Cause is nitrogen discharge from fertilizers. Algal blooms result, using up most of the available oxygen. Size of dead zone fluctuates with seasonal use of fertilizer and amount of runoff. Not an isolated occurrence.
Often, cleanup in coastal areas is as harmful as the spill
Abyssal plain mud as place
to dump “pollutants.”
Now we are into international waters, which would best be handled by UN regulations or international treaties. Even radioactive waste might be disposed of in such settings. We might also consider dumping as an environmental industry, with economic as well as environmental value.
Loss of marine wetlands because of infill and loss of
mangroves to timber.
The CWA included enacting the Coastal Zone Management Act to
protect tidal wetlands. But
legal interpretations of definition of a wetland still allow destruction of
wetlands
Biological Invaders:
both plant and animal. Reduce animal invaders by regulating release of ballast water