MetalsMetalsFate and EffectsFate and Effects

OverviewOverview

A.A. History of Metal ToxicityHistory of Metal Toxicity Oldest known toxin? (fall of Roman Empire due to Pb?)Oldest known toxin? (fall of Roman Empire due to Pb?)

Water transported in lead pipesWater transported in lead pipes Wine enhanced by a grape-based syrup, cooked in lead-lined pots (250 Wine enhanced by a grape-based syrup, cooked in lead-lined pots (250

ug/d. vs 45 ug/d. recommended by WHO)ug/d. vs 45 ug/d. recommended by WHO) Minimata Bay, JapanMinimata Bay, Japan

Chisso Corporation dumped Chisso Corporation dumped ~27 ~27 tonstons of Hg into bay starting in 1938 of Hg into bay starting in 1938 Mid-50’s Mid-50’s people began noticing symptoms of strange disease people began noticing symptoms of strange disease

Degeneration nervous systems, numbness in limbs and lips, slurred speech, Degeneration nervous systems, numbness in limbs and lips, slurred speech, constricted vision, serious brain damage, unconsciousness, involuntary constricted vision, serious brain damage, unconsciousness, involuntary movements, uncontrollable shouting. movements, uncontrollable shouting.

Insane cats committing "suicide" Insane cats committing "suicide" Sea birds dropping dead from the sky. Sea birds dropping dead from the sky.

1959 1959 established that Hg had some how worked up through food chain established that Hg had some how worked up through food chain into fish, people, animalsinto fish, people, animals

Chisso denied any wrong-doing, continued dumping Hg until Chisso denied any wrong-doing, continued dumping Hg until 19681968

Developmental and neurological effects of Developmental and neurological effects of Hg on Japanese child, Minimata Bay, JapanHg on Japanese child, Minimata Bay, Japan

Overview (con’t)Overview (con’t)

B. Essential vs. non-essential metalsB. Essential vs. non-essential metals Essential metalsEssential metals - important as - important as

plant/animal plant/animal micronutrientsmicronutrients Includes (Co, Cu, Cr, Fe, Mn, Ni, Mo, Se, Ti, Zn)Includes (Co, Cu, Cr, Fe, Mn, Ni, Mo, Se, Ti, Zn) Over-enrichment can lead to toxicity Over-enrichment can lead to toxicity

Non-essential metalsNon-essential metals Always toxic above threshold levelAlways toxic above threshold level Includes Pb, Cd, HgIncludes Pb, Cd, Hg

Metal ChemistryMetal Chemistry

A.A. Metals are basic elementsMetals are basic elements1.1. Accumulates in organisms Accumulates in organisms not broken down by not broken down by

liver, etc.liver, etc.2.2. Persistent in environment Persistent in environment last long time in last long time in sinks sinks

low/no exposure (no hazard)low/no exposure (no hazard) can come back can come back out out hazardous again hazardous again

B.B. pH effect (acidity = -log[HpH effect (acidity = -log[H++])]) Metal toxicity dependent on pHMetal toxicity dependent on pH1. Speciation- free ionic form usually most 1. Speciation- free ionic form usually most toxic toxic increase free iron as decrease pH increase free iron as decrease pH

Note: exception to the rule Note: exception to the rule aluminum aluminum

Change in Aluminum speciation as pH changes Change in Aluminum speciation as pH changes Note: most toxic form of aluminum is Al(OH)Note: most toxic form of aluminum is Al(OH)33

Metal ChemistryMetal ChemistryA.A. Metals are basic elementsMetals are basic elements

1.1. Accumulates in organisms Accumulates in organisms not broken down by liver, etc. not broken down by liver, etc.2.2. Persistent in environment Persistent in environment last long time in last long time in sinks sinks low/no low/no

exposure (no hazard)exposure (no hazard) can come back out can come back out hazardous hazardous againagain

B.B. pH effect (acidity = -log[HpH effect (acidity = -log[H++])]) Metal toxicity dependent on pHMetal toxicity dependent on pH1. Speciation- free ionic form usually most toxic 1. Speciation- free ionic form usually most toxic increase free iron as decrease pHincrease free iron as decrease pH

Note: exception to the rule Note: exception to the rule aluminum aluminumC. Solubility/PrecipitationC. Solubility/Precipitation

1. decreased solubility and increased precipitation as 1. decreased solubility and increased precipitation as increase pH increase pH both cause decreased toxicity both cause decreased toxicity

Summary – both chemical speciation and precipitation, and Summary – both chemical speciation and precipitation, and thus toxicity, is extremely dependent on pH (level of thus toxicity, is extremely dependent on pH (level of acidity)acidity)

Sources/SinksSources/Sinks

Sources – many different sources = many Sources – many different sources = many different metals entering the environmentdifferent metals entering the environment

SinksSinks [polluted freshwater] > [polluted seawater][polluted freshwater] > [polluted seawater] High [coastal sediment] > high [freshwater High [coastal sediment] > high [freshwater

sediment]sediment]

ConclusionConclusion – final sink is the ? – final sink is the ?

ElementElement SeaSea

water water

((µµg/L)g/L)

Marine Marine

SedsSeds

(mg/kg)(mg/kg)

Fresh Fresh

water water

((µg/L)µg/L)

Freshwater Freshwater SedimentsSediments

(mg/kg)(mg/kg)

AnthropoAnthropo

-genic -genic sourcessources

CopperCopper 0.2-5000.2-500 2-7002-700 0.3-90000.3-9000 <5-2000<5-2000 Mining, smelting, Mining, smelting, steel, fossil fuelssteel, fossil fuels

MercuryMercury 0.001-0.70.001-0.7 0.01-8000.01-800 0.01-300.01-30 0.02-100.02-10 Coal combustion, Coal combustion, fungicidesfungicides

LeadLead 0.005-0.40.005-0.4 10-20010-200 0.2-9000.2-900 3-20,0003-20,000 Lead smelting, Lead smelting, lead alkyl prodnlead alkyl prodn

ZincZinc 0.01-200.01-20 5-100,0005-100,000 0.1-50,0000.1-50,000 <10-10,000<10-10,000 sewage sludge, sewage sludge, miningmining

IronIron 20-10,000,00020-10,000,000 Coal mining, Coal mining, smelting, irrigat’nsmelting, irrigat’n

ManganeManganesese

5-116,0885-116,088 Coal mining, Coal mining, irrigationirrigation

AluminumAluminum 0.1-2,000,0000.1-2,000,000 Coal mining Coal mining leached acid rainleached acid rain

Concentration Ranges of Selected Trace Metals Concentration Ranges of Selected Trace Metals

Lower values in ranges are typical baseline concentrations; higher values are concentration reported at sites affected by human activities

ToxicityToxicity

Ranges from slight Ranges from slight reduction to rapid reduction to rapid deathdeath

Very dependent on Very dependent on other environmental other environmental factors (especially factors (especially water pH, hardness, water pH, hardness, and temperature)and temperature)

Different mechanisms Different mechanisms of toxicity depending of toxicity depending on whether exposure on whether exposure is acute or chronicis acute or chronic

Acute toxicityAcute toxicity

1.1. Most acute toxicity due to Most acute toxicity due to adsorptionadsorption to gills (often little to gills (often little metal gets into animal, only body surface exposed)metal gets into animal, only body surface exposed)

2.2. Many metals cause body ion loss Many metals cause body ion loss ECF loss ECF loss circulatory collapse circulatory collapse death death

3.3. Generally mollusks, fish more tolerant than other phyla Generally mollusks, fish more tolerant than other phyla important to test several tropic levels for effect of important to test several tropic levels for effect of any toxicantany toxicant

4.4. In general In general Cu > Hg > Zn > Pb to aquatic organisms Cu > Hg > Zn > Pb to aquatic organisms5.5. Results of acute toxicity test used to set allowable Results of acute toxicity test used to set allowable

environmental limits (which will be chronic in nature) environmental limits (which will be chronic in nature) because hard to test metal effect over a long term because hard to test metal effect over a long term pH, hardness, etc change)pH, hardness, etc change)

Effect of metals on body Na levels of the Effect of metals on body Na levels of the stonefly stonefly Acroneuria carolinensisAcroneuria carolinensis

from Grippo and Dunson, 1996

Chronic toxicityChronic toxicity

1.1. Most often associated with assimilation into Most often associated with assimilation into organism (high [metal] inside organism)organism (high [metal] inside organism)

2.2. [chronic LOEC] <<< [acute LOEC][chronic LOEC] <<< [acute LOEC]3.3. EffectsEffects

a.a. Fish – Fish – embryonic/larval most sensitive (spawning/hatching)embryonic/larval most sensitive (spawning/hatching) TeratogenesisTeratogenesis Growth reduction – due to reduced assimilation efficiencyGrowth reduction – due to reduced assimilation efficiency

b.b. Invertebrates – Invertebrates – each successive developmental stage more resistant than each successive developmental stage more resistant than

former stageformer stage Period of larval settlement is crucial Period of larval settlement is crucial any delay will increase any delay will increase

mortality due to predation, disease and dispersion (wrong mortality due to predation, disease and dispersion (wrong place at wrong time)place at wrong time)

Effect of metals on scope-for- growthEffect of metals on scope-for- growth

Metal contaminated sites

• Depressed scope-for-Depressed scope-for-growth growth theoretical theoretical instantaneous growth rate instantaneous growth rate after ingestion, after ingestion, assimilation and assimilation and respiration taken into respiration taken into accountaccount

• Positive scope-for-Positive scope-for-growth = energy for growth = energy for growth, reproductiongrowth, reproduction

• Negative “ “ Negative “ “ “ = animal is “ = animal is losing energylosing energy

Regulation of metalsRegulation of metals

A.A. Water Quality Criteria (WQC)Water Quality Criteria (WQC) Suggested maximum concentration Suggested maximum concentration

suggested (set) by EPA suggested (set) by EPA state sets state sets standardstandard = allowable limit of metal = allowable limit of metal

Many metal standards based on hardnessMany metal standards based on hardness

Note: hardness may not have most effect on Note: hardness may not have most effect on toxicity but effect is most well-known (most toxicity but effect is most well-known (most studied)studied)

Hardness-based WQCsHardness-based WQCs

General formulaGeneral formula

C = C = expexp {a[ln(hardness)] + b}{a[ln(hardness)] + b}

wherewhereexp = base of the natural logexp = base of the natural log

a,b = constants determined by linear a,b = constants determined by linear regression of ln(hardness) against the natural regression of ln(hardness) against the natural log of the median acutely lethal concentration log of the median acutely lethal concentration (LC(LC5050))

C = allowable concentration (WQC)C = allowable concentration (WQC)

Examples of hardness calculated WQCs Examples of hardness calculated WQCs (based on hardness value of 100 mg/L (based on hardness value of 100 mg/L

hardness as CaCOhardness as CaCO33

MetalMetal EquationEquation Calculated Calculated valuevalue

CadmiumCadmium expexp {0.7852[ln(hardness)]{0.7852[ln(hardness)] – 3.490} – 3.490} 1.13 1.13 µµg/Lg/L

CopperCopper expexp {0.8545[ln(hardness)]{0.8545[ln(hardness)] – 1.465} – 1.465} 11.82 11.82 µµg/Lg/L

Note: if hardness value entered in mg/L then calculated value will be in units of µg/Lµg/L