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Stressors in the Great Lakes: Heavy Metals

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

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Stressors in the Great Lakes: Heavy Metals

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  1. Stressors in the Great Lakes: Heavy Metals

  2. Definition • No generally accepted definition exists for heavy metals • Defining factor: 5 g/ cm3

  3. Heavy Metal in the Great Lakes Bernier et al., 1995

  4. Sources Industrial sources of Heavy Metalemissions include: • Waste oil • Solid waste incineration / coal burning and ash • Iron and steel production • Smelting • Battery and lead alkyl manufacturing • Lead-Historically fuels in cars and trucks (regulations and lead free gasoline)

  5. Arsenic • Commonly occurring • Hard to measure direct sources • Use has decreased greatly since 1980

  6. Arsenic Toxicity • Arsenic 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 ATP • Makes it difficult for muscles to fire • Organ systems shut down due to lack of energy • 1 mg/kg/day is the acute lethal dose • 50 ppb will lead to precursors for cancer

  7. Cadmium • 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)

  8. 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

  9. Entrance into the Environment • 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)

  10. Cd Transportation & Fate • 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

  11. Cd Toxicity • 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)

  12. Lead Lead (Pb) is the most abundant toxic heavy metal General Human populations are exposed through air and food in equal proportions

  13. Sources Mainly atmospheric depositions of industrial lead Lead from shots- hunting Side note: Drinking water Found 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)

  14. Lead: Fate • Accumulation of Pb in sediment • Accumulation of Pb organisms: All the way up the food web from plankton to fish • Higher accumulation in crayfish, bottom feeders • Bioaccumulation in humans too: especially fish consumers

  15. Lead: Toxicology Impacts: • Nervous system • increased blood pressure in adults • pathogenic effect: • directly interrupts the activity of enzymes • competitively inhibits absorption of important trace minerals • deactivates antioxidant sulphydryl pools through free-radical induced damage

  16. Mercury • Takes two forms in environment • Inorganic Hg (metallic) • Less worrying as an environmental toxin • Organic MeHg • Methyl Mercury • Bioaccumulates in tissues • Biomagnifies up the food chain

  17. Fate and Transport of Hg

  18. MeHg impacts to organisms and human health • 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

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