28 Metals - Chemical Pollutants Metals and Non-metals...

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Unformatted text preview: Chemical Pollutants Metals and Non-metals Mercury, Arsenic, and Lead Lead found in blood sample from 1 of 10 Washingtonians Arsenic found in urine samples from 4 of 10 Washingtonians Mercury found in hair samples from 10 of 10 Washingtonians Common Health Effects Lead behavioral problems high blood pressure, anemia kidney damage memory and learning difficulties miscarriage, decreased sperm production reduced IQ blindness and deafness brain damage digestive problems kidney damage lack of coordination cognitive degeneration breathing problems death if exposed to high levels decreased intelligence known human carcinogen: lung and skin cancer nausea, diarrhea, vomiting peripheral nervous system problems Mercury Arsenic Wonderland Mercury Nitrate Symptoms included tremors, emotional instability, insomnia, dementia and hallucinations Natural Groundwater Contaminants Fluoride and Arsenic India Failure of 246 surface irrigation projects 21 million backyard tube wells $600 electric pumps (1% of GDP) 95 % water tables falling by 20 feet per year What do you do when your water table falls? Deeper Wells and Fluoride Naturally occurring element in Granite which dissolves into the groundwater Water near the surface is generally unaffected Lowering water tables = deeper wells Deep wells can contain granite and high fluoride levels Fluoride in water can be a cumulative poison What’s the obvious question? Intentional Fluoridation of Water in the U.S. Fluoridation became an official policy of the U.S. Public Health Service in 1951. By 1960 water fluoridation had become widely used in the U.S. reaching about 50 million people. By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water. How does it work? Tooth enamel is made of a mineral called hydroxyapatite Ca5(PO4)3OH Bacteria in the mouth create acids (H+) Hydroxyapatite is subject to dissolution by acids (H ) + Fluoridation changes the chemical composition of hydroxyapatite to a crystal less subject to acid dissolution Sodium fluorosilicate (Na2SiF6) Sodium fluoride (NaF) NaF Na+ + F- Ingestion of fluoridated water increases the F concentration in saliva F- replaces OH in hydroxyapatite making fluoroapatite F Ca5(PO4-)3 OH Fluoroapatite is less soluble in acid than hydroxyapatite Fluoride concentrations In U.S. tap water 0.5 – 1.0 mg/L Lower values in warm climates Fluoride levels > 1.5 mg/L Dental Fluorosis Intake: 1.6 to 6.6 mg/day Colorado Brown Stain Permissible fluoride limit in India is 1.2 mg/L Fluoride levels between 5-25 mg/L have been found Skeletal Fluorosis Fluoride levels > 10 mg/L Intake 9 mg/day to 12 mg/day Fluorosis has risen from 1 million to 25 million and threatens 60 million people in India. Extra Credit: 1. The chemical that made the Mad Hatter mad _____ 2. Country affected by fluoride poisoning __________ 3. Fluoride is naturally occurring. True or False 4. Colorado Brown Stain is a name for ____________ Groundwater and Arsenic Arsenic is Naturally Occurring occurs primarily in association with sulfur-containing minerals Natural waters, in general, contain low levels of total arsenic Mobilization of arsenic in the environment arises from anthropogenic activities related to mining and ore processing, metallurgy, agriculture, wood preservation, and industry. Inorganic Forms of Arsenic AsO 3 Arsenite -3 AsO4-3 Arsenate Low Oxygen High Oxygen Arsenite is more toxic than arsenate, interfering with enzyme activities which catalyze metabolic reactions Arsenite compounds are also more mobile in the environment due to higher solubility compared to arsenate compounds Both arsenate and arsenite are chronic accumulative toxins “The World’s Largest Mass Poisoning” Bangladesh and W. India ranked among the world's 10 poorest countries Floodplain and Delta of the Ganges and Brahmaputra Rivers. Floodplain: area paralleling a river that is periodically inundated Himalayas Ganges-Brahmaputra Delta Deltas are formed from the deposition of sediment carried by the river as the flow leaves the mouth of the river Accumulation of thick muds in the floodplains and deltas Bangladesh Prior to 1970s One of the highest infant mortality rates in the world Principally due to waterborne disease. Ineffective water and sewage systems Periodic monsoons and floods water-borne pathogens cholera, dysentery Deaths Due to Surface water contamination: 250,000/yr Deaths Due to Surface water contamination: 250,000/yr The Solution: Tap groundwater resources • easy • inexpensive • available First 1 million wells were sunk with aid from World Governments UNICEF World Bank 12 million hand-operated tube wells deliver water to over 80% of the rural village population Infant mortality and diarrheal illness reduced by 50% Wells in Floodplain and Delta Sediments Natural erosion of arsenic to waterbearing units. Well depths between 20m and 100 m Water Bearing Muds WHO/U.S limit: 10 ppb Bangladesh limit: 50 ppb Delta and Floodplain Regions Majority of wells > 50 ppb arsenic Some wells contain 500 - 1000 ppb Exposure Estimates Above 10 ppb: Above 50 ppb: 57 million people 35 million people Accumulative Toxin Early Symptoms: Skin lesions and thickening Strong skin pigmentation Long-term Exposure breathing problems death if exposed to high levels lung and skin cancer peripheral nervous system 2003 Studies 83 million people Bihar: 40% wells contaminated Red River Delta 11 million people First wells sunk 7 years ago Mercury Got Fish? Mercury Advisories 70% of states Where does it come from? Enters water bodies principally from the atmosphere Mercury is naturally occurring (coal, volcanism, rock weathering) The number 1 anthropogenic source is the combustion of coal 48 tons of elemental mercury to the atmosphere each year. Mercury The drinking water standard for Mercury is 0.002 mg/L. blindness, deafness brain damage digestive problems kidney damage lack of coordination cognitive degeneration 1 gram Electrical products such as dry-cell batteries, fluorescent light bulbs, switches, and other control equipment account for 50% of mercury used. Fluorescent Lights A typical fluorescent lamp is composed of a phosphor-coated glass tube with electrodes located at either end. The tube contains a small amount of mercury vapor. When a voltage is applied, the electrodes energize the mercury vapor, causing it to emit ultraviolet (UV) energy. The phosphor coating absorbs the UV energy, causing the phosphorus to fluoresce and emit visible light. Hg gas UV Phosphor Coating Voltage Recycling and Handling Each year, an estimated 600 million fluorescent lamps are disposed of in US landfills amounting to 30,000 pounds of mercury waste. Forms of Mercury The dominant inorganic forms are Hgo and Hg2+. Hg2+ often occurs as HgCl2 (mercuric chloride) in many aqueous environments. Hg2+ (inorganic) interacts with soil and sediment particles (- charge) becoming part of lake bottom sediments (limits availability) Interaction with Sediment Particles - charge Hg2+ Hg2+ Hg2+ Small organic and Inorganic particles - charge - charge Mercury Bound to Sediments Mercury, however, can undergo chemical Hg2+ changes in lakes which render mercury more environmentally dangerous Hg2+ sediments Negatively charged particles bind mercury And retain it in bottom sediments. - charge Mercury Methylation Mercury can be converted to more toxic forms in bottom sediments under anaerobic conditions Mercury Methylation Methylation: conversion of inorganic forms of mercury, Hg2+, to an organic form: methyl mercury under anaerobic conditions Hg 2+ (CH Hg ) methylmercury 3 + Methylmercury is strongly accumulated in the body and is generally more toxic than inorganic Hg Mercury Methylation Requires 4 elements: • anaerobic conditions • a carbon source (organic sediments) a source of sulfur (SO ) • 4- • sulfur reducing bacteria Occurs primarily in bottom sediments as a byproduct of the life processes of anaerobic sulfate-reducing bacteria (SO4 to HS-) that live in high sulfur, low oxygen environments. Sulfate + 3H = 6HCO + 3HS C H O + 3SO42- Respiration 6 + 3When 12 6 accepts electrons it is said to be “reduced”. sulfur Desulfuromonas, Pseudomonas The exact role of sulfate-reducing bacteria In mercury methylation is poorly understood However, bacterial sulfate respiration requires sulfate. The addition of sulfate to water stimulates the metabolic activity of sulfatereducing bacteria and the inadvertent methylation of inorganic mercury Sulfate concentrations in EAA runoff and Lake Okeechobee average more than 50 times background concentrations than in the pristine Everglades Sulfate Hg from coal, volcanism, rock weathering, point sources 2+ Water Sediments (Bound) Sulfur reducing bacteria, low O2 methylmercury Aquatic Organisms Enhanced Risk Methylmercury attaches to proteins in animals (enters food chain) Methylmercury has a half-life in human blood of about 70 days (almost twice as long as inorganic mercury (Hg ). 2+ Methylmercury is strongly accumulated in the body and is generally more toxic than inorganic Hg Bioaccumulation: concentration of a chemical in organisms relative to the amount in water. Biomagnification: concentration of a chemical in organisms as it moves up the food chain. Bio-magnification Bioconcentration and Biomagnification BAF = Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below. Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades. Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors. Methylmercury in the organs and tissues causes birth defects & disorders of the brain, reproductive system, immune system, kidney, and liver at extremely low levels in food. Chemical Concentration in organism Chemical Concentration in water Minamata Bay Chisso Corporation, a company located in Kumamoto Japan, dumped an estimated 27 tons of mercury compounds into Minamata Bay Between 1932 and 1968. 1963 plastics, drugs, and perfumes acetaldehyde As of March 2001, 2,265 victims had been officially recognized (1,784 died) and over 10,000 had received compensation from Chisso Assessing Your Risk http://www.edf.org/page.cfm?tagID=17694 http://www.mercuryfacts.org/fSafeFish.cfm Nearly all fish and shellfish contain traces of methylmercury. However, larger fish that have lived longer have the highest levels of methylmercury because they've had more time to accumulate it. These large fish (swordfish, shark, king mackerel and Albacore tuna) pose the greatest risk. Some of the most commonly eaten that are low in mercury are shrimp, canned light tuna, salmon, pollock, and scallops. Fish sticks and "fast-food" are commonly made from fish that are low in mercury. Next: Other Bioaccumulative Toxins ...
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This note was uploaded on 02/24/2011 for the course SWS 2007 taught by Professor bonczek during the Fall '09 term at University of Florida.

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