Pollutants & Sources

Phosphorus Ammonia & Nitrite Combined Sewer Overflows Mercury & Other Industrial Wastes Sediment Loading: Tully Valley Mudboils Salinity Nonpoint Source Pollution

Major pollutants and pollution sources in Onondaga Lake include phosphorus, ammonia, combined sewer overflows (CSOs), mercury, excessive sedimentation, high salinity, and nonpoint source pollution.

Onondaga Lake is one of the most polluted lakes in the United States. The lake's present condition is the result of more than a century of domestic and industrial pollution. The major sources of Onondaga Lake pollution can be divided into two main areas: those related to wastewater collection and treatment and those related to past industrial operations and uses. Othr pollution problems include excessive sedimentation and nonpoint source pollution.

Municipal wastewater (sewage) has been a major source of pollution to Onondaga Lake, resulting in excessive levels of phosphorus, ammonia and nitrite (from the Onondaga County Metropolitan Syracuse Wastewater Treatment Plant — Metro), and bacteria and viruses (from combined sewer overflows — CSOs).
Allied Corp. (Honeywell), a major industrial discharger to the lake, shut down in 1986. Water quality has improved significantly since the company closed its facility, but problems associated with Allied's and other companies' industrial operations remain, including mercury contamination and high salinity.
The Tully Valley mudboils contribute to excessive sedimentation of Onondaga Creek and the lake.
A variety of activities contribute nonpoint pollution to the lake, including pollutants that increase the lake's ammonia and phosphorus levels.

Major pollutants and pollution sources are listed below. Follow the links below or in the menu to learn more about each pollutant or pollution source. Some of the pollutants affect the lake's dissolved oxygen supply, which affects fish and other aquatic life. See The Importance of Oxygen to learn more about the relationship between pollution and dissolved oxygen.

Phosphorus

Phosphorus from Metro and other sources stimulates the excessive growth of algae in the lake. This decreases the lake's water clarity and eventually causes the loss of oxygen in the lake's bottom waters.

Ammonia and Nitrite

Ammonia and nitrite are nitrogen compounds which can be toxic to fish and other aquatic life. Ammonia and nitrite are discharged into the lake in amounts that can be harmful to fish. Metro is the source for more than 90% of the lake's ammonia.

Combined Sewer Overflows

During heavy storm periods, a mixture of raw sewage and street runoff overflows from the sewer system through relief structures called combined sewer overflows (CSOs). The mixed sewage and runoff flows directly into several of the lake's tributaries, releasing harmful bacteria and viruses that eventually reach the lake.

Mercury and Other Industrial Wastes

Mercury and other toxic contaminants associated with industrial processes have been detected in the lake's sediments and aquatic life. In 1970, fishing in Onondaga Lake was banned because of mercury contamination. Catch and release fishing is now allowed, but health advisories limit eating fish from the lake.

High Salinity

Although the lake's pre-Columbian (before Christopher Columbus) salt content might have been higher than in other area lakes, wastebeds continue to elevate the lake's salt content. The of the lake's water reduces the diversity of aquatic life and alters the lake's natural stratification cycle.

Sediment Loading: Tully Valley Mudboils

Mudboils occur to the south of Onondaga Lake in the Tully Valley. The mudboils are responsible for continuous sediment loading to Onondaga Creek, which has an adverse effect on water quality in the creek and lake.

Nonpoint Source Pollution

Nonpoint source pollution refers to water pollution which does not originate from a single clearly identifiable source like a pipe which discharges from a factory into a water body. Nonpoint pollution originates over a broad area and a variety of sources. Nonpoint source pollution contributes to increased phosphorus and ammonia levels in teh lake, as well as contributing to reduced aesthetics and other water quality problems

For More Information

More details on the pollution and restoration history of Onondaga Lake are available on the Pollution History Timeline.