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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

bulletSulfuric Acid is the main ingredient for acid discharge from oxidised sulfidic muds eg - iron mono sulfides and iron pyrites.

Acid Cycle

bulletA 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

bulletAcid discharge describes the discharge of the acidic effluent water as a result of oxidation of sulfidic muds and iron pyrites associated with ASS.

Acidity

bulletWhere the pH is less than 7, where 7 is neutral.
bulletThe pH reading is the amount of hydrogen ions in the solution or available.

Active Acid Neutralization

bulletIs the artificial neutralization to pH 7 by using alkaline reagents as a neutralizer.
bulletReagents used are calcium carbonate, calcium hydroxide.

Acid Run-off from Acid Sulfate Soils

bullet

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.

bullet

CRAB is designed to actively dose acid waterways with crushed limestone and calibrated hydrated lime raising pH levels to an acceptable level.

bullet

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

bulletWhere the pH is greater than 7, where 7 is neutral.

Black Ooze -

bullet see Iron Sulfides or Iron Monosulfides

Calibrated

bulletRefers to the accurate calibratibility of the CRAB to be able to match reagent ouptut for the desired result.

Developing Nations

bullet

Many of the developing nations are situated in the tropics and sub tropic areas which are associated with mangrove deltas.

bullet

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

bulletDisturbing Acid Sulfate Areas by urban development may oxidize PASS areas producing acid and other forms of disturbance and exposure can be from flood scouring.
bulletThis 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.
bulletThe Richmond River had a 'fish kill' as a result of de-oxygenation and eventual acidity.

Eco-systems

bulletEco-systems are ecological systems where all environmental components are in health balance.

Effluent

bullet

Effluent is polluted water in AMD and ASS.

bullet

Drainage the pollution can consist of

  1.                                     Acidity

  2.                                     Dissolved Iron

  3.                                     Dissolved Aluminium

bullet

These can all be in highly concentrated levels, pH & 2.7 450mg p/l aluminium- 600mg p/l iron.

bullet

These have been encountered in Catchment areas of Northern NSW.

 

Earthworks

bulletEarth works for the control of Acid production form Acid Sulphate Soils may take the form of -
  1.                             Capping to stop oxidation of marine muds.
  2.                             Filling in of deep drains to reduce erosion and oxidation.
  3.                             Damming to maintain water levels within the soil profile.
  4.                             Special drainage to manipulate water table.
  5.                             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'.

bullet

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.

bullet

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.

bullet

The actions of sulfuric acid + salt water + organic matter is to produce iron monosulfides, simply shown below.

Iron Sulfides & Iron Monosulfides

bullet 

 

Natural Sea Water

+

Dissolved oxidised sulfur (SO4)-

+

Organic matter, Fuel

Dissolved hydrogen sulfides

HS + 2HCO

 

 

+

Land Leaching

Dissolved Ferric Oxides

FeO

+

Organic Matter, Fuel

CHO

Ferrous ions

'Black Ooze' or Ferrous sulfide or Iron monosulfide FeS
Drains

Ponds

Marshes

=

Anoxic Environment

 

bulletThis 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.

Written without prejudice

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Last modified: 05/06/04

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