stressors in the great lakes: heavy metals
DESCRIPTION
Stressors in the Great Lakes: Heavy Metals. Definition. No generally accepted definition exists for heavy metals Defining factor: 5 g/ cm 3. Heavy Metal in the Great Lakes. Bernier et al., 1995. Sources. Industrial sources of Heavy Metal emissions include: Waste oil - PowerPoint PPT PresentationTRANSCRIPT
Stressors in the Great Lakes: Heavy Metals
No generally accepted definition exists for heavy metals
Defining factor: 5 g/ cm3
Definition
Heavy Metal in the Great Lakes
Concentrations in the Great Lakes (ppt)
Mercury
Cadmium
Lead
Lake Huron
60 16 38
Lake Superior
98 27 39
Lake Michigan
52 42 260
Lake Erie
42 98 910Bernier et al., 1995
Industrial sources of Heavy Metal emissions include:
Waste oil Solid waste incineration / coal burning and
ash Iron and steel productionSmelting Battery and lead alkyl manufacturingLead-Historically fuels in cars and trucks
(regulations and lead free gasoline)
Sources
ArsenicCommonly occurringHard to measure
direct sourcesUse has decreased
greatly since 1980
Arsenic ToxicityArsenic is used to kill
Insecticides, herbicides, fungicides, preservatives
Arsenic kills by disrupting the cellular process that produces ATP.Blocks and competes with chemicals that form
ATPMakes it difficult for muscles to fireOrgan systems shut down due to lack of energy
1 mg/kg/day is the acute lethal dose50 ppb will lead to precursors for cancer
Transition metal like zinc and mercury (happy in oxidation state of +2)
Rare metal- 0.1 ppm in Earth’s crust most in zinc ores
A byproduct/impurity from zinc production (mining, smelting, refining)
Cadmium
Cadmium Uses Resistant to corrosion-
Used for electroplating of iron
Used as color coating/pigments in paints ( mid 20th century) various salt forms
Carboxylate forms of cadmium (laureates & stearates) for stabilizing PVC
Growing demand for nickel-cadmium batteries in 21st century
Solar cells
Burning of fossil fuels (coal) creation of cadmium oxide (CdO)
High cadmium conc. of phosphate fertilizers from mined rocks into soils
Dissolved by acid to create chlorides, sulfates, and nitrates Reclaimed from iron/steel recycling in dust Solid waste incineration (Milorganite)
Entrance into the Environment
Intake normally through inhalation and ingestion
Absorbed into kidneys Bioaccumulation in marine life No known useful role for Cd in higher
organisms Certain marine diatoms in low zinc conc.
Utilize Cd for carbonic anhydrases
Cd Transportation & Fate
Metal fume fever- Inhalation of certain metal oxides (flu like symptoms
Compounds containing Cd are carcinogenic Inhalation leads to respiratory and kidney
issues. Ingestion causes immediate
poisoning/damage to kidneys and liver May cause osteoporosis- loss of bone
mineral density Kidneys lose function to remove acids in
blood (proximal renal tubular dysfunction)
Cd Toxicity
Lead
General Human populations are exposed through air and food in equal proportions
Lead (Pb) is the most abundant toxic heavy metal
Mainly atmospheric depositions of industrial lead
Lead from shots- hunting
Sources
Side note: Drinking waterFound in piping: lead pipes, welding for copper pipes
City of Milwaukee adds phosphate to drinking water to prevent lead in pipes from dissolving into drinking water (adding to lake nutrient load)
Accumulation of Pb in sediment Accumulation of Pb organisms: All the way up the food web from plankton to
fishHigher accumulation in crayfish, bottom
feedersBioaccumulation in humans too: especially
fish consumers
Lead: Fate
Impacts:Nervous system increased blood pressure
in adultspathogenic effect:
directly interrupts the activity of enzymes
competitively inhibits absorption of important trace minerals
deactivates antioxidant sulphydryl pools through free-radical induced damage
Lead: Toxicology
Takes two forms in environment Inorganic Hg (metallic)
Less worrying as an environmental toxin Organic MeHg
Methyl MercuryBioaccumulates in tissuesBiomagnifies up the food chain
Mercury
Fate and Transport of Hg
Central Nervous system Damage Sensory and motor skill Impairment
Reproductive Effects Readily transferred across placenta Concentrates in fetal brain Physical behavioral defects Fetal death
Immunotoxicity Dose-dependent correlation in T-cell proliferation an MeHg
Genotoxicity Chromosome Breakage DNA strand Breakage
MeHg impacts to organisms and human health