Lower Grand Watershed Interactive Tool (WIT) - Metals
Metals are toxic substances, such as mercury and lead, that come from urban runoff or atmospheric deposition
The lower Grand River basin includes several population and industrial centers that have adversely impacted the watershed. Historically, the Grand Rapids area was known for large-scale metal finishing and plating industries that contributed significant amounts of heavy metals to the environment. A large tannery with a historic discharge to the river was located in the Grand Haven area along with a number of metal production facilities. Heavy metals are relatively insoluble in water and are rapidly incorporated in sediments after discharge. Metals do not degrade and remain buried in sediment deposition areas or are transported to Lake Michigan.
Recent studies of the 12 major tributaries of Lake Michigan have found the Grand River to be one of the most significant contributors of contaminant loads to Lake Michigan. Since the industrial sources of metals in the lower Grand River basin have been eliminated due to closure or the implementation of effective waste treatment technology, current contaminant loadings are related to transport of sediments and atmospheric deposition.
Mercury and lead are two of the most environmentally significant heavy metals present in the lower Grand River basin.
Mercury enters the aquatic environment through runoff, atmospheric deposition, and wastewater discharges. It is released to the atmosphere by coal-fired power plants and incinerators. Once mercury is discharged, it remains in the environment for years as it accumulates in sediments and fish tissue. Bacteria and chemical reactions in lakes and wetlands change the mercury into a much more toxic form known as methylmercury. This form of mercury is mobile and accumulates in fish tissue. One million average salmonids from Lake Michigan would contain just a pound of mercury altogether, yet the concentration in each fish would be high enough to call for limits on eating them. Mercury can impact human health because it is toxic to the developing nervous system of a fetus or young child. Damage occurring before birth or in infancy can cause a child to be late in beginning to walk and talk and may cause lifelong learning problems. Unborn children can be seriously affected even though the methylmercury causes no symptoms in their mothers. Fish caught in the Lower Grand River Basin have consumption advisories due to mercury contamination.
Like mercury, lead is a persistent heavy metal that is toxic to aquatic life. In addition to sources related to industrial discharges, the metal can enter the environment from the disposal and combustion of lead based fuels. While lead is toxic to humans, it does not accumulate in fish tissue. Lead accumulates in sediments and can impact the organisms that live on the river bottom.
In the lower Grand River basin, sediments containing heavy metals can be found in point bars and depositional areas associated with islands in the river channel. Historic fill areas such as Harbor Island also contain heavy metals. In addition to potential impacts to human and environmental health, heavy metals also affect the disposal of dredged sediments. The Grand River is dredged on an annual basis to maintain a navigational channel. Elevated levels of heavy metals prevent the disposal of dredged materials in local waters and consequently, additional costs are required for a secure storage on land.
Special thanks to Rick Rediske, AWRI Chemist, for his contribution.