Soil and Sediment Toxicity

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Soil and Sediment Toxicity

• Getting Down n Dirty

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Introduction

• Nobody cared much about soil at the beginning of
  the environmental movement
• Environmental scientists eventually realized ?
  almost everything ends up in soil or sediments ?
  currently large area of interest

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Magnitude of Soil Contamination Problem

• Large problem ? Soil contamination associated
  with worst toxic dumps in US
• 30 located in Northeast
• 12 in NJ (the Garden State)
• Usually in/near metropolitan areas
• Large economic losses
• Spills contaminate soil, then groundwater,
  farmland (Toxic Real Estate)
• History of mismanagement of waste by
  municipalities (i.e. Love Canal)

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The Love Canal Saga

• William T. Love started a canal in town of Niagra
  Falls, NY to connect upper and lower Niagara
  River for power generation.
• Canal abandoned when invention of AC spawned
  long-distance electric power.
• Hooker Chemicals and Plastics Corp. dumped 22,000
  tons of chemical products in canal from 1920 to
  1953 (with full knowledge of city officials)
• 1953 ? When full, canal backfilled with soil and
  presumed safe.
• City's Board of Ed. bought the dump site in1953,
  ? aware of chemicals (listed in deed), but
  ignored the problem to build a school.
• 1957 ? city punched a sewer line through Canal
  walls, allowing wastes to seep throughout the
  neighborhood sewer system
• Baby Boom ? residential development occurs along
  and on old dump site
• 1968 ? NY DoT builds highway along edge of site,
  disturbs more buried chemicals
• Early 70s ? People begin showing health
  problem, including increased cancer and birth
  defects

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Love Canal changes over time
Love Canal in 1951
Love Canal in 1980
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The Saga Continues

• 1978 ? Jimmy Carter declares area a federal
  emergency and 260 families are relocated
• Homes demolished, land fenced off
• 1980 Comprehensive Environmental Response,
  Compensation and Liability Act (CERCLA,
  Superfund) passed ? EPA used CERCLA to sue
  Hooker, wins 129 million for clean-up.
• Final containment (plastic, clay cap) of most
  polluted soil completed in 1995
• People started to move back into Love Canal
  because newly built houses were cheap.

Demolition and soil containment
Abandoned street in Love Canal,
circa 2005
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CERCLA

• Initiated largely in response to Love Canal
• Designed to identify deep pockets responsible
  for site contamination
• Funded by tax on petroleum and chemical
  industries
• gt 15 billion spent since creation

Photo from Wikipedia
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I. What is soil?

• Types very diverse
• Mix of rock, weathered mineral, and organic
  matter
• 95 is mineral matter by dry weight (but only 45
  by volume)
• Lots of air space (20-30 by volume) ? lots of
  room for infiltration/retention of pollutants

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Soil Classification

• Classified by composition based on particle size
• Sand coarse ? high infiltration, percolation
• Silt intermediate
• Clay finest ? less pore volume, hard to
  penetrate but greater long-term retention

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Clay Composition

• Composed of Al and Si sheets
• large surface area for
• Adsorption
• Large sum of negative charges high cation
  exchange capacity (can hold cations large
  buffering capacity but many cations may be
  pollutants i.e. metals)
• Therefore, clays can be good or bad ? hold more
  (bad) but holding may keep pollutants from being
  available to ecosystem (good)

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II. Sources of Soil Pollution

• Direct pollution dumping, accidental spills
  (trucks, trains, aeroplanes), leaks, landfills
• Deposition from atmosphere (especially acid rain)
• Sediments from water pollution

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III. Factors Affecting Severity of Impact

• Infiltration how fast pollutant gets into the
  soil (how fast need to clean up?)
• Percolation how far down into the soil does it
  go? (reach water table?)
• Retention how long does it stay?
• Buffering capacity (adsorption capacity) soil
  becomes toxic only after binding
  ability/reduction in availability is overcome

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IV. Soil Factors Affecting Toxicology

• Bulk density (g/m3) and porosity
• - compact soils have reduced air space lower
  infiltration and percolation
• pH sorption to soil is often pH dependent
  (note soils are usually good buffers ? hard to
  change pH
• PCBs decreased pH increased adsorption
  decreased toxicity
• Al, Mn become more bioavailable as decrease pH
  increased toxicity
• Ammonia ammonium ion (NH4) converted to
  ammonia (NH3) at high pH

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IV. Soil Factors Affecting Toxicology

• Topography
• Often determines soil properties and pollution
  load
• Ridgetop soils shallower, better drained than
  bottomland soil
• Bottomland soils greater repository for
  pollutants
• collect from ridgetop leaching and what is
  purposely deposited there (remember Alices
  Restaurant)
• Organic Matter Content
• OM has negative ionic charge that can absorb and
  retain pollutants
• High OM soils occur in colder climates and poor
  soil aeration ? both inhibit breakdown of OM

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V. Remediation

• Liming or acid addition adjust/balance pH
• Soil burning
• very costly, not usually done
• way to dispose of dioxin ? burn at 1000 C.
  (reason why Agent Orange burned at sea)
• Soil removal
• common method during early Superfund but really
  just moving pollutants around (Alices Restaurant
  ? one trash pile better than two)
• Now just used for special cases (e.g. Radon? PA,
  NJ, Mn)

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V. Remediation

• Bioremediation
• toxin-eating microbes ? good possibility for
  GMOs?
• Containment
• put up fence and signs to keep away or DIE!
• Pump and Treat
• Contaminated groundwater from contaminated soil,
  may treat chemically or burn

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Sediments
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I. What are Sediments?

• Also very diverse in composition
• Basically aquatic environment version of soils
• 1 repository for biotic and abiotic material
  (including pollutants) in aquatic environment
• Accumulation of sediment pollutants can cause
• Changes in benthic community structure
• Increased body burdens
• Toxicity

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Sediment Classification

• Organic carbon content affects sorption of
  neutral organic chemicals ? increased Kow
  increased sorption
• Particle size distribution larger particles
  tend to sorp fewer pollutants
• Clay content and type can change pollutant
• Cation exchange capacity affect sorption of
  cations
• pH affects metal speciation, sorption

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II. Implications of Sediment Transport

• Wind, Wave and Currents
• Moves sediments around according to particle sise
• Results in
• Clay suspended in water columns
• Sand (or larger) in high energy areas
• Silt in low energy (depositional) areas
• Note can cause sediment focusing
• Sediment Focusing
• Different sediment types carry different
  pollutants ? pollutants accumulate according to
  distribution of sediment to which they are
  attached
• Example Great Lakes ? DDT, methoxychlor found in
  fine clay particles, endosulfan on larger
  particles

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II. Implications of Sediment Transport

• Pore/Interstitial Water
• Water between sediment particles
• Non-polar pollutants ? sediments ? pore water ?
  overlying water column
• Primary source of pollutant exposure to
  sediment-associated organisms
• Sediments may bind pollutants, then get overlayed
  by non-pollution containing sediments ? reduce
  bioavailability
• May be better to leave contaminated sediments in
  place rather than dredging them up, resuspending
  them and making biologially active again (e.g.
  lower Hudson River and New York harbor, Charles
  River and Boston Harbor, Potomac River and
  Washington estuary)