Transcript Lignite Acid Mining Lakes

Acid Lakes
from Lignite Mines
Dan Henderson
Lignite
 Brown/soft
coal .
 Used for steam electric power generation.
 Mined in open pits.
 Production declining in most countries.
Where
 Germany
(Lusatia)
 Russia
 United
States (SE)
 Australia
 Greece
Acid Mining Lakes (AML)
 Artificial
Lakes form in open pits when
mining ceases.


Groundwater recharge
Stream inputs
 Natural
Lakes receive Acid Mine Drainage
(AMD) from nearby mines.
 pH as low as 2 recorded in some lakes.
Acid Mine Drainage
 Outflow
of acidic water from mines.
 High Concentrations of sulfate and iron
 Result from pyrite (iron sulfide) and other
sulfides from mine tailings oxidizing in
water.
 Bacteria found in rock may promote
acidification (acidophiles).
 Vary depending on local geology.
Effects on Lake Chemistry
 Metals
are more soluble at lower pHs.
 High concentrations of dissolved Fe.

Light Attenuation
 High

concentrations of Al.
May limit P
 May
also increase levels of Mn, Zn, As,
and Pb.
 Depend on acid neutralizing capacity.
Effects on Vegetation
 Low
pH Limits species diversity and
richness.
 Many plants cannot tolerate high metal
concentrations.
 Tolerant species may thrive.
 Vegetation may increase surface
concentrations of metals by
evapotranspiration.
Phytoplankton
 Development
not directly related with pH
decrease.
 Decrease
related to limitations of inorganic
carbon, phosphorus, and underwater light.
Effects on other Biota
 Limits
lake food for birds and wildlife that
find food in lake.
 Low pH decreases fish diversity and
richness.
 Insect larvae and crustaceans not likely to
be found below pH of 4.
 Usually enough silica still present for
diatom development.
Why treat AMLs
 Ecosystem
 Wildlife
 Recreation
 Aesthetics
Health
Main Treatment Methods
 Preventative
measures best approach.
 Altering mine site hydrology.
 Sulfate reducing bacteria.
 Application of organic wastes.
 Application of alkaline materials
(Limestone).
 Wetlands.
Sulfate reducing bacteria
 Good
method for treatment.
 Require anaerobic conditions which may
be limited in well mixed lakes.
 Increase alkalinity and help eliminate Fe
and sulfate.
 Most are heterotrophs which require and
may be limited by organic carbon.
Biobags (Organic Wastes)
 Bags
of organic material placed into lakes.
 Form anoxic microbial reaction
compartments.
 Increase organic carbon and P
concentrations which promote sulfate
reducing bacteria.
 Increase primary production by increasing
nutrients. (Eutrophication)
 Use local organic material.
Application of Limestone and/or
Phosphorus
 Limestone
increases pH levels needed for
biological growth.
 Reduces metal concentrations by making
them less soluble.
 Phosphorus is frequently limited in AMLs.
 Phosphorus promotes phytoplankton
development and biological growth.
Wetlands
 Used
extensively in last two decades to
remove metals from AMD.
 Precipitation of sulfides.
 Roots of wetland plants release oxygen
and form Fe plaque taking other metals
with it.
 Biological Uptake.
More treatment methods
 Inundation
 Bacteriacides
 Coating
 More
for acidophiles
pyrite to prevent oxidation
needed
Progression
 Some
lakes may take decades to recover.
 Allochthonous alkalinity of river water will
promote progress.
 Bottom of food chain must be established
first to support the rest.
 Ultimate goal is to establish fish
populations.
Results
 All
methods have been shown to work.
 Best methods are very site specific.
 A combination is usually the best
approach.
 Certain species found to recover much
faster than others.
 Neutralized AMLs have much greater
species richness.
Importance
 Treatment
of AMLs may produce circumneutral lakes much faster than if left alone.
 May
prevent the loss of diversity.
 Treated
lakes may be used for recreation
and promote ecosystem health.
Research Needed
A
low percentage of AMLs have been
studied.
 Recovery methods can be expensive and
time consuming.
 AMLs continue to grow in number even
though mining is in decline.
 Many effects of AMD may yet to be
identified and understood.
Conclusion

Raising pH to near circum-neutral level is how
most AMLs are treated, but this is not sufficient
to meet all ecological demands.
 Effects on ecosystems, treatment processes,
and recovery times all vary greatly.
 Lake acidification is a worldwide problem and
limnologists are needed to continue to refine,
identify, and implement new strategies for
remediation.
Questions
?