Draft DEWCP and EPA guidance on managing acid sulfate soils



Cover

Overview

Guidelines

Referral to EPA

Source of Information

Glossary

App. 1: Checklist

 

Draft DEWCP and EPA guidance on managing acid sulfate soils

Glossary of terms

Australian Height Datum (AHD): The datum used for the determination of elevations in Australia. The determination uses a national network of bench marks and tide gauges, and sets mean sea level as zero elevation.

Acid sulfate soils: Soil or sediment containing highly acidic horizons or layers by the oxidation of iron sulfides (actual acid sulfate soils) and/or soil or sediment containing iron sulfides or other sulfidic material that has not been exposed to air and oxidised (potential acid sulfate soils).
Note: The term acid sulfate soil generally includes actual and potential acid sulfate soils. Actual and potential acid sulfate soils are often found in the same soil profile, with actual acid sulfate soils generally overlying potential acid sulfate soil horizons.

Actual acid sulfate soils (AASS): soil or sediment containing highly acidic soil horizons or layers affected by the oxidation of soil materials that are rich in iron sulfides, primarily pyrite. This oxidation produces hydrogen ions in excess of the sediment's capacity to neutralise the acidity, resulting in soils of pH 4 or less. These soils can usually be identified by the presence of jarosite.

Potential acid sulfate soils (PASS): soil or sediment containing iron sulfides or sulfidic material that have not been exposed to air and oxidised. The field pH of these soils in their undisturbed state is pH 4 or more, and may be neutral or slightly alkaline.

Agricultural lime: a neutralising agent commonly used to treat acidic soils; by composition, it is commonly 95-98% pure calcium carbonate (CaCO3); it is insoluble in pure water, with a pH of ˜8.3; application rates will depend on the purity and fineness of the product.

Anaerobic conditions: conditions whereby air (oxygen) is excluded, usually by waterlogging.

Aquifer: rock or sediment in a formation, group of formations or part of a formation that is capable of storing and transmitting water (or another fluid) in significant quantities to bores, wells or springs.

Advice agency: for a development application, means an entity prescribed under a regulation as an advice agency for the application, or if the functions of the entity in relation to the application have been devolved or delegated to another entity, the other entity.

Anoxic: means in the absence of oxygen.

Borehole: the actual hole created when an auger or push-tube is inserted into the soil body; the portion removed (the core) will demonstrate the soil profile.

Drain water: water contained in a drain, which flows into a drain, or flows immediately from a drain.

Dewatering: means the deliberate pumping siphoning, draining or other diversion of waters to render a site or area dry.

Estuary (Estuarine): numerous definitions have been given for estuaries. The standard definition for an estuary only describes the interaction between river and marine currents ' ...a widened mouth of a river valley where freshwater intermixes with seawater and where tidal effects occur' (Lapidus 1990).

Extracting groundwater: this includes drainage, pumping or otherwise removing groundwater.

Flocculation: the process whereby small particles clump together into particles of greater mass; commonly seen as iron flocs in streams.

Framboidal (pyrite): microscopic pyrite crystals aggregated in clusters resembling the shape of a raspberry. Common in ASS.

Groundwater: subsurface water in the zone of saturation, including water below the watertable and water occupying cavities, pores and openings in underlying soil and rock.

Groundwater flows: Water that moves laterally or vertically through the body of soil but is not confined as to direction of flow.

Holocene: a period of time from about 10,000 years ago to the present, an epoch of the Quaternary period.

Jarosite: an acidic pale yellow iron sulfate mineral: KFe3(SO4)2(OH)6. Jarosite is a byproduct of the acid sulfate soil oxidation process, formed at pH less than 3.7; commonly found precipitated along root channels and other soil surfaces exposed to air.

Leachate: the soil constituent that is washed out from a mixture of soil solids.

Mobilise: situation where the naturally occurring metals in soil or sediment are changed from an insoluble to a soluble state.

Neutralising: the process whereby acid produced (by the oxidation of iron sulfides) is counteracted by the addition of an ameliorant such as lime (CaCO3); there are formulae for calculating the amount of ameliorant needed.

Oxidised: process of chemical change involving the addition of oxygen following exposure to air.

pH: a measure of the acidity of alkalinity of a soil of water body on a logarithmic scale of 0 to 14; a pH <7 is acid, pH 7 is neutral, and pH >7 is alkaline. Note that one unit change in pH is a tenfold change in acidity.

Piezometer: a pipe of small diameter installed in a borehole that is used to measure the height (elevation) of the watertable (piezometric or potentiometric surface). The term can also refer to the instrumentation installed in the pipe. Nested piezometers are a group of piezometers established at different depths to measure the height of the watertable throughout an aquifer.

Pyrite: pale-bronze or brass-yellow, isometric mineral: FeS2; the most widespread and abundant of the sulfide minerals.

Quaternary: a geological time period extending from 1.8 million years ago to present time; incorporates both the Pleistocene and Holocene epochs.

Recharge area: the portion of the landscape in which rainwater enters the soil body moving down the profile to the groundwater.

Scalded areas: areas which are bare of vegetation due to extremely adverse growing conditions, such as being too acid.

Soil and sediment: the natural accumulation of unconsolidated mineral particles (derived from weathered rocks) and organic matter that covers much of the earth's surface. The chemical and physical composition varies greatly between soil and sediment types. Clays, silts, sands, gravels, peats, muds and indurated sands (e.g. 'coffee rock') are all examples of soil and sediment.

Soil permeability: a measure of the ease with which water can enter or move through a soil body.

Soil profile: this is an accurate representation of spatial proportions of the different vertical layers in a soil body; each layer has individual chemical and physical properties that govern its behaviour.

Subsoil: Commonly understood as that portion of the soil formed below the A horizon; the depth at which it commences varies enormously (e.g. from 5 cm to 5 metres); it has particular characteristics.

Acid sulfate soils map: risk map units have been classified on the basis of the geomorphological and hydrological properties of the relevence to the formation of acid sulfate soils, including the depth to groundwater and height above sea level in AHD.

Watertable: portion of the ground saturated with water; often used specifically to refer to the upper limit of the saturated ground.

Waters: includes river, stream, lake, lagoon, pond, swamp, wetland, unconfined surface water, unconfined water natural or artificial watercourse, bed and bank of any waters, dams, non-tidal or tidal waters (including the sea), stormwater channel, stormwater drain, roadside gutter, stormwater run-off, and any under groundwater, any part-thereof.


© Copyright 2007 All rights reserved