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Links found on this page -
acid sulfate soils ,
acid mine drainage ,
artificial sumping ,
CRAB , Calibrated Flood Gate Valve
Photos of oxidized
Acid Sulfate Soils
Click on thumbnail for larger size
Acid Sulfate Soils
Terminology
Acid
 | Sulfuric Acid is the main ingredient for acid discharge from oxidised
sulfidic muds eg - iron mono sulfides and iron pyrites. |
Acid Cycle
| A typical view of the acid cycle would look something like this - |
Sulfur (sea water) + organic matter from estuaries (fuel) + iron from soil
leaching would react to produce a 'black ooze' associated with swamps and tidal
areas (iron mono sulfides).
Acid Discharge
| Acid discharge describes the discharge of the acidic effluent water as
a result of oxidation of sulfidic muds and iron pyrites associated with ASS. |
Acidity
| Where the pH is less than 7, where 7 is neutral. |
| The pH reading is the amount of hydrogen ions in the solution or
available. |
Active Acid Neutralization
| Is the artificial neutralization to pH 7 by using alkaline reagents as
a neutralizer. |
| Reagents used are calcium carbonate, calcium hydroxide. |
Acid Run-off from Acid Sulfate Soils
|
The Acid Sulphate run-off as a product is a matter for concern as it becomes a major
pollution problem causing serious fish kills as was seen in the Lismore &
Grafton floods in early 2001. |
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CRAB is designed to actively dose acid
waterways with crushed limestone and calibrated hydrated lime raising pH levels to an acceptable level. |
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The combination of sound engineering principles has produced a unique
machine for the safe and accurate dosing of problem areas associated with Acid
Sulfate run off. |
Alkalinity
| Where the pH is greater than 7, where 7 is neutral. |
Black Ooze -
| see Iron Sulfides or Iron
Monosulfides |
Calibrated
| Refers to the accurate calibratibility of the CRAB to be able to match reagent
ouptut for the desired result. |
Developing Nations
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Many of the developing nations are
situated in the tropics and sub tropic areas which are associated with
mangrove deltas. |
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These low lying deltas are a constant
source of Acid Sulphate Soils and marine sulfidic muds and present a major
problem for over populated low lying areas. |
Disturbed Areas
| Disturbing Acid Sulfate Areas by urban
development may oxidize PASS areas producing acid and other forms of
disturbance and exposure can be from flood scouring. |
| This happened to the Richmond River in NSW 1998 when
monosulfide 'black ooze' was scoured out and mobilized by flood water
resulting in the scavenging of oxygen form the water column causing oxidation
of the 'black ooze' and the subsequent production of acidity. |
| The Richmond River had a 'fish kill' as a result of
de-oxygenation and eventual acidity. |
Eco-systems
| Eco-systems are ecological systems
where all environmental components are in health balance. |
Effluent
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Effluent is polluted water in AMD and
ASS. |
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Drainage the pollution can consist of
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Acidity
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Dissolved Iron
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Dissolved Aluminium
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These can all be in highly
concentrated levels, pH & 2.7 450mg p/l aluminium- 600mg p/l iron. |
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These have been encountered in Catchment
areas of Northern NSW. |
Earthworks
| Earth works for the control of Acid production form
Acid Sulphate Soils may take the form of - |
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Capping to stop oxidation of marine muds.
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Filling in of deep drains to reduce erosion and oxidation.
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Damming to maintain water levels within the soil profile.
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Special drainage to manipulate water table.
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Ponding to contain effluent for treatment.
Fish Diseases & Fish Kills
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The main fish disease associated with
acid run off from disturbed PASS is known as 'red spot'. |
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This is an ulceration of the fish
skin caused by the mucous protecting the fish being dissolved by low pH
leading to ulceration & death of the fish. |
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Shell fish are also effected and the
general health of the whole river environment is severely effected.
Sulfuric Acid consumes the natural carbonation in salt water reducing the
amount of carbonation available for crustaceans leaving them susceptible to
disease and attack. |
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The actions of sulfuric acid + salt
water + organic matter is to produce iron monosulfides, simply shown below. |
Iron Sulfides & Iron Monosulfides
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Natural Sea Water
+
Dissolved oxidised sulfur (SO4)²-
+
Organic matter, Fuel
Dissolved hydrogen sulfides
H²S + 2HCO³
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+
Land Leaching
Dissolved Ferric Oxides
Fe²O³
+
Organic Matter, Fuel
CH²O
Ferrous ions |
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'Black Ooze' or Ferrous sulfide or Iron monosulfide FeS |
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Drains
Ponds
Marshes
=
Anoxic Environment |
| This very simplified example is the main cause of fish kills and shows
the naturally occurring nature of the production of 'black ooze'. Whilst
left submerged or covered over they remain only in a 'potential state' but
once disturbed in floods or by artificial means they have the ability to
'strip' oxygen from the surrounding water, becoming oxidized and then becoming
acidic. Initial de-oxygenation killing fish. |
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