metals and mercury
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Metals and Mercury. Biological pollution. Discovery of coliform bacteria had the greatest impact on municipal water systems and water treatment. 1/3 weight of average uninfected human waste. - PowerPoint PPT PresentationTRANSCRIPT
Metals and Mercury
Not necessarily a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present
Coliforms are naturally present in the environment; fecal coliforms only come from human and animal fecal waste.
Biological pollution
Discovery of coliform bacteria had the greatest impacton municipal water systems and water treatment.
1/3 weight of average uninfected human waste
Forms of Water Treatment
Suspended SolidsFlocculation
Sand filtration
Flocculation – bringing together of high numbersof small particles to create larger particles whichsettle out of water quickly.
Advanced treatment uses chlorine disinfectionTo remove pathogenic organisms from water.
1880sScientists demonstrate that microorganisms can cause disease.
First application of chlorine disinfectants to U.S. municipal water facilities in Jersey City and Chicago.
1908
First U.S. drinking water bacterial standard.1915
Over 1,000 U.S. cities employ chlorine disinfection.
1918
More than 19,000 municipal water systems operate throughout the U.S.
1960
Biological Pollution and Chlorination
Chlorine is currently employed by over 98 percent of all U.S. water utilities that disinfect drinking water
Effectiveness of Chlorination: Typhoid Yardstick
De
ath
s p
er
100
,00
0
1860 1910 1935
Today: < 40 per 200 million people
bacterium Salmonella typhi
174 per 100,000 persons died of Typhoid in 1891
Metals: Mercury
ArsenicErosion of natural deposits; pesticide waste, runoff from glass & electronics production wastes, treated lumber, groundwater
MercuryErosion of natural deposits; discharge from refineries and factories; runoff from landfills, coal burning
LeadCorrosion of household plumbing systems; natural deposits, paint, fuels, electronics
Heavy Metals and Metalloids
Common Health Effects
Lead
behavioral problemshigh blood pressure, anemiakidney damagememory and learning difficultiesmiscarriage, decreased sperm productionreduced IQ
Mercury
blindness and deafness brain damagedigestive problemskidney damagelack of coordinationcognitive degeneration
Arsenic
breathing problemsdeath if exposed to high levelsdecreased intelligenceknown human carcinogen: lung and skin cancernausea, diarrhea, vomitingperipheral nervous system problems
Wells in Floodplain and Delta Sediments
Water Bearing Muds
Natural erosion ofarsenic to water-bearing units.
Well depths between 20m and 100 m
Arsenic
Majority of wells > 50 ppb arsenic Some wells contain 500 - 1000 ppb
WHO/U.S limit: 10 ppbBangladesh limit: 50 ppb
-lead pipes
-lead acetate sugar of lead
sweetener for wine
Lead (Plumbum)Father of all metals Possible cause of the
dementia which affected Roman Emperors and Citizens.
Contemporary Sources:
Paint, ceramics, glass, soils, pipes,Solder, brass faucets, gasoline
Mercury
Got Fish?
Mercury Advisories
70% of states
Where does it come from?
Mercury is naturally occurring
The number 1 anthropogenic sourceis the combustion of coal
Enters water bodies principally from the atmosphere
(coal, volcanism, rock weathering)
48 tons of elemental mercury to the atmosphere each year.
blindness, deafness brain damagedigestive problems
kidney damagelack of coordination
cognitive degeneration
Mercury
Electrical products such as dry-cell batteries, fluorescent light bulbs, switches, and other control equipment account for 50% of mercury used.
The drinking water standard for Mercury is 0.002 mg/L.
1 gram annually
Fluorescent LightsA 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 phosphor to fluoresce and emit visible light.
Voltage
Hg gasUV
Phosphor Coating
Each year, an estimated 600 million fluorescent lamps are disposed of in US landfills amounting to 30,000 pounds of mercury waste.
Recycling and Handling
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 sedimentparticles (- charge) becoming part of lake bottom sediments (limits availability)
Interaction with Sediment Particles
- charge
- charge
- charge
Hg2+
Small organic andInorganic particles
Hg2+
Hg2+
- charge
sedimentsHg2+
Mercury Bound to Sediments
Hg2+
Negatively charged particles bind mercuryAnd retain it in bottom sediments.
Mercury, however, can undergo chemicalchanges in lakes which render mercury
more environmentally dangerous
Mercury can be converted to more toxic forms in bottom sediments
under anaerobic conditions
Mercury Methylation
Mercury Methylation
Methylation: conversion of inorganic forms of mercury, Hg2+, to an organic form: methyl mercury under anaerobic conditions
Hg2+ (CH3Hg+) metylmercury
Methylmercury is strongly accumulated in the bodyand is generally more toxic than inorganic Hg
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.
Mercury Methylation
When sulfur accepts electrons it is said to be “reduced”.
C6H12O6 + 3SO42- + 3H+ = 6HCO3
- + 3HS-
Sulfate Respiration
Requires 4 elements:• anaerobic conditions• a carbon source (organic sediments)• a source of sulfur (SO4
-)• sulfur reducing bacteria
However, bacterial sulfate respiration requires sulfate.
The addition of sulfate to water stimulates the metabolic activity of sulfate-reducing 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
The exact role of sulfate-reducing bacteriaIn mercury methylation is poorly understood
Sulfate
Hg2+ from coal, volcanism, rock weathering, point sources
Water
Sediments(Bound)
Sulfur reducing bacteria, low O2
methylmercury Aquatic Organisms
Biomagnification: concentration of a chemical in organisms as it moves up the food chain.
Bioaccumulation: concentration of a chemical in organisms relative to the amount in water.
Enhanced Risk
Methylmercury has a half-life in human blood of about 70 days(almost twice as long as inorganic mercury (Hg2+).
Methylmercury attaches to proteins in animals (enters food chain)
Methylmercury is strongly accumulated in the bodyand is generally more toxic than inorganic Hg
Bio-magnification
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.
Bioconcentration and Biomagnification
Chemical Concentration in organismChemical Concentration in waterBAF =
Chisso Corporation, a company located in Kumamoto Japan, dumped an estimated 27 tons of mercury compounds into Minamata BayBetween 1932 and 1968.
As of March 2001, 2,265 victims had been officially recognized (1,784 died) and over 10,000 had received compensation from Chisso
Minamata Bay
1963
acetaldehyde
plastics, drugs, and perfumes
Assessing Your Risk
http://www.edf.org/page.cfm?tagID=17694
http://www.mercuryfacts.org/fSafeFish.cfm
Fish sticks and "fast-food" are commonly made from fish that are low in mercury.
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 mackereland tilefish) pose the greatest risk.
Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.