Soil and Sediment Toxicity

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21 Φεβ 2014 (πριν από 3 χρόνια και 3 μήνες)

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Soil and Sediment
Toxicity

Getting’ Down ‘n Dirty

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


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)

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, c
anal 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


r
esidential development occurs along and on old dump site


1968


NY DoT builds highway along edge of site, disturbs more buried
chemicals


Early ’70’s


People begin showing health problem, including increased
cancer and birth defects

Love Canal changes over time

Love Canal in 1951

Love Canal in 1980

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

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


> $15 billion spent since
creation

Photo from Wikipedia

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
pollutant’s


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

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)


II. Sources of Soil Pollution

1.
Direct pollution


dumping, accidental spills
(trucks, trains, aeroplanes), leaks, landfills

2.
Deposition from atmosphere (especially
acid rain)

3.
Sediments from water pollution

III. Factors Affecting Severity of Impact

1.
Infiltration



how fast pollutant gets into the soil
(how fast need to clean up?)


2.
Percolation



how far down into the soil does it go?
(reach water table?)


3.
Retention



how long does it stay?


4.
Buffering capacity



(adsorption capacity)


soil
becomes toxic only after binding ability/reduction in
availability is overcome


IV. Soil Factors Affecting Toxicology

A.
Bulk density (g/m
3
) and porosity


-

compact soils have reduced air space = lower
infiltration and percolation


B.
pH


sorption to soil is often pH dependent (note:
soils are usually good buffers


hard to change pH

1.
PCBs


decreased pH = increased adsorption =
decreased toxicity

2.
Al, Mn


become more bioavailable as decrease pH =
increased toxicity

3.
Ammonia


ammonium ion (NH
4
+
) converted to
ammonia (NH
3
) at high pH


IV. Soil Factors Affecting Toxicology

C.
Topography

Often determines soil properties and pollution
load

1.
Ridgetop soils


shallower, better
drained than bottomland soil

2.
Bottomland soils


greater
repository for pollutants


collect from ridgetop leaching and what
is purposely deposited there (remember
Alice’s Restaurant)


D.

Organic Matter Content

1.
OM has negative ionic charge that
can absorb and retain pollutants

2.
High OM soils occur in colder
climates and poor soil aeration


both inhibit breakdown of OM

V. Remediation

A.
Liming or acid addition


adjust/balance pH

B.
Soil burning


very costly, not usually done


way to dispose of dioxin


burn at 1000
°

C. (reason
why Agent Orange burned at sea)

C.
Soil removal


common method during early Superfund but really
just moving pollutants around (Alice’s Restaurant


“one trash pile better than two”)


Now just used for special cases (e.g. Radon


PA,
NJ, Mn)


V. Remediation

D.
Bioremediation


toxin
-
eating microbes


good possibility for GMO’s?

E.
Containment


put up fence and signs to keep away or DIE!

F.
Pump and Treat


Contaminated groundwater from contaminated soil, may treat
chemically or burn

Sediments

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

1.
Changes in benthic community structure

2.
Increased body burdens

3.
Toxicity

Sediment Classification

1.
Organic carbon content


affects sorption of
neutral organic chemicals


increased Kow
= increased sorption

2.
Particle size distribution


larger particles
tend to sorp fewer pollutants

3.
Clay content and type


can change
pollutant

4.
Cation exchange capacity


affect sorption
of cations

5.
pH


affects metal speciation, sorption

II. Implications of Sediment Transport

A.
Wind, Wave and Currents

1.
Moves sediments around according to particle sise

2.
Results in

a.
Clay suspended in water columns

b.
Sand (or larger) in high energy areas

c.
Silt in low energy (depositional) areas

Note: can cause
sediment focusing


B.
Sediment Focusing

1.
Different sediment types carry different pollutants


pollutants accumulate according to distribution of
sediment to which they are attached

2.
Example: Great Lakes


DDT, methoxychlor found
in fine clay particles, endosulfan on larger particles

II. Implications of Sediment Transport

C.
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


D.
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)