Characteristics of salt as a pollutant

Characteristics of SALT as a pollutant.

Characteristics of salt (salinity) as a pollutant.“ A Pollutant is something that when released into the environment causes some harm or alters the environment in a negative way.”

Every pollutant needs to be understood in terms of….CHARACTERISTICSSOURCETRANSPORTEFFECTSPERSISTENCESINKS

ABC Salinity News

The term salinity refers to the concentration of dissolved salts in water or soil and is expressed in terms of concentration (mg/L) or electrical conductivity (EC).

Salinity management is one of the most significant environmental challenges facing the Murray–Darling Basin.

If left unmanaged, salinity has serious implications for water quality, plant growth, biodiversity, land productivity and the supply of water for critical human needs. MDBA

Characteristics of SALT as a pollutant.

General CharacteristicsSalinity is a measure of the content of salts in soil or water. Salts are highly soluble in surface and groundwater and can be transported with water movement. Large salt deposits are a natural feature of vast areas of the Australian landscape, stored deep in soils or as surface salt deposits and salt lakes. This natural distribution of salt in the landscape is referred to as 'primary salinity'.

In normal circumstances, the deep roots of native plants absorb most water entering the soil before it reaches the salt contained in groundwater below the plant root zone. However, widespread vegetation clearance, poor land use, irrigation and industrial practices have made it easier for salt to be transported to the soil surface or to waterways. The additional salt from these altered land use and management practices is referred to as 'secondary salinity'.

Excessive amounts of dissolved salt in water can affect agriculture, drinking water supplies and ecosystem health. Salinity is a significant issue in south-western Australia and in some Murray-Darling Basin regions within New South Wales, Victoria, and South Australia.http://www.environment.gov.au/water/publications/quality/factsheet-salinity-and-water-quality

Characteristics of SALT as a pollutant.

Chemical characteristicsSalt is formed when a metal reacts with a base. Table salt (NaCl Sodium Chloride) is an example. Sodium is the metal and chloride is the base.Salt occur naturally with other metals, including heavy metals such as copper (Cu), zinc (Zn), magnesium (Mg), calcium (Ca) and many others. These are important to human health in low levels, but are toxic in high levels. http://www.manoramaonline.com/advt/palathulli/reportspdf/IISC_KERALA_RESULT14_SALINITY.pdf Fertilisers can also contribute salt to the environment. Most chemical fertilisers have combinations of nitrogen, phosphorous and Potassium (N:P:K ratio). Used in excess, salts from chemical fertilisers can pollute waterways. http://www.dubbo.nsw.gov.au/_literature_32912/Fertilisers_and_soil_conditioners

Characteristics of SALT as a pollutant.

Chemical characteristics Synergistic actionAn interaction between two or more individual compounds that produces an effect upon the body (or an organism) GREATER than either of the substances alone would have produced. When the combined result is greater than the sum of it’s parts.Example: Smog – combinations of pollutants.Bioaccumulation and Biomagnification

The effect of salinity is worsened by drought. Plants growing in soils with shallow salty water tables (ground water) only have shallow roots. In drought conditions plants access water deep in the soil profile. Where irrigation salinity, or dryland salinity occurs they are unable to do this and hence the effect is worsened.

Higher groundwater levels mean more water interacts with friable, sandy soil and forms the crust of salt that can accelerate erosion and destroy agricultural productivity. http://www.smh.com.au/environment/water-issues/higher-rainfall-holds-key-to-salinity-20090628-d1az.html#ixzz3A9eGDZ6f

Characteristics of SALT as a pollutant.

SourcesPOINTA point source is when the contaminant comes from a single source – you can pinpoint this location on a map. For example, a sewerage pipe, a chimney or a leaking oil tank. They are shown on a map as an x.

Point sources of salt in the natural environment include,where creeks with a lot of erosion in their catchment enter a larger stream, or which are polluted by human actions such as littering, industrial processes and run-off from roads and rubbish dumps. Point sources of salinity can also include polluted drains and sewage pipes.

Although we talk about sources of salt in the human diet, these are best refered to in another section, ‘pathways’ (into the human body), which would be ingestion (eating and drinking).

Characteristics of SALT as a pollutant.

SourcesDIFFUSEDiffuse sources are when the exact location cannot be determined precisely. For example, exhaust gases on a highway or methane gases leaking from landfill. They are shown on a map by shading an area.

Dryland salinity is a diffuse source, because the exact location cannot be determined accurately; rather it is easier to shade the contributing area on a map. Dryland salinity happens when deep rooted vegetation is removed allowing salty ground water to reach the surface.

Characteristics of SALT as a pollutant.

SourcesDIFFUSEDiffuse sources are when the exact location cannot be determined precisely. For example, exhaust gases on a highway or methane gases leaking from landfill. They are shown on a map by shading an area.

Irrigation salinity is caused when more water is applied to the soil than can be transported away by ground water flows, or evaporated by vegetation. It is often associated with flood irrigation, particularly where deep rooted vegetation, such as trees and native perennial grasses have been removed.

Irrigation has been more controlled since the Murray Darling Basin Plan was first introduced in 2010. Some areas of the Campaspe are no longer irrigated because farmers were not able to afford the cost of upgrading existing channels.Leaking channels contributed to rising water tables.

Characteristics of SALT as a pollutant.

SourcesDIFFUSEDiffuse sources are when the exact location cannot be determined precisely. For example, exhaust gases on a highway or methane gases leaking from landfill.

Groundwater seepage is the prime contributing cause of salinity in the Campaspe Basin. Saline ground water enters the river in multiple undetermined locations. Salinity in groundwater is a natural occurrence, however levels would be expected to be higher where deep rooted vegetation such as trees and perennial grasses has been removed.

Characteristics of SALT as a pollutant.

TransportDispersal and TransportThe way that a pollutant is spread or moves around the environment. Dispersal can be airborne, water borne or in soils.

Salt is carried through soil as ground water, in rivers dissolved in water, and through the air as soil particles and sea spray.

In our Victorian landscape today, there are three main sources of salt:

1. Many areas, such as the Mallee, were once covered by an inland sea. When the sea retreated about 10 million years ago, the sediments it left behind contained large quantities of salt . Many soils in the Mallee region have been derived from these materials.

2. Salt from the sea is carried inland by strong wind, to fall in rain. As you would expect, salts in rainfall are highest near the coast, decreasing inland. A surprising average of 6-8 kilograms/hectare/year falls on inland Victoria.

3. Salt is one of the products of the weathering of rocks. Salts are present in rocks and are released by weathering and dissolved by rainfall. In arid regions, where there is not enough rainfall to flush the salt through the soils, the products of rock weathering accumulate in the soil over millions of years.

(ref: Saltbook 1998 DNRE p1).

Characteristics of SALT as a pollutant.

TransportThe salinity of groundwater can vary, even in the one area, because of the presence of impervious layers which keep waterbodies separate. When boring for water, the water with the lowest levels of salinity are targeted. Fracking endangers these supplies of fresh water because the fractures that are caused allow the movement of gas, oil and water between these layers. Ovwerirrigation and the removal of trees lead to the upward movement of water tables (groundwater) towards the surface. In Australia, this is often saline and can reduce the suitability of land for farming.

Dispersal and TransportThe way that a pollutant is spread or moves around the environment. Dispersal can be airborne, water borne or in soils.

Characteristics of SALT as a pollutant.

Effects on the environmentSafe levels (EC units).

Characteristics of SALT as a pollutant.

Effects on the environmentNatural environment.

Declining yields and plants turning reddish, yellowish or brown, or plants with dead leaf tips or margins are often the first indication of a salt problem. By the time more salt tolerant plants begin to take over, up to 30% of a farmer’s crop or pasture production may have been lost!

There are many signs of salinity such as:• salt tolerant plants• dying trees• wilting• waterlogging• loss of legumes e.g. clover, medics (so that grasses lack nitrogen)• reduced yield• slow germination• bare patches

As the salt levels in the soil have increased, first the clovers and medics, then the improved grasses have disappeared and the area has become dominated by ‘salt indicator plants’ - sea barley grass and spiny rush. Eventually even these plants may die, leaving patches of bare ground and salt crystals visible on the surface. Ref: Saltbook DNRE 1998 p10.

Salinity management is one of the most significant environmental challenges facing the Murray–Darling Basin. If left unmanaged, salinity has serious implications for water quality, plant growth, biodiversity, land productivity and the supply of water for critical human needs.

High salinity can:● reduce crop yields● affect aquatic ecosystems and vegetation● damage infrastructure. Ref: MDBA

Researchers in Adelaide are using new breeding techniques to develop plant varieties that can better cope with drought and salinity.

These environmental stresses are reducing the quality and yields of many of our grain crops, when with an increasing population we need production to dramatically increase. Catalyst

Increased salinity can reduce crop yields when it impairs the growth and health of salt-intolerant crops and may result in corrosion of machinery and infrastructure such as fences, roads and bridges. env.gov.au

At the end of the last drought the Coorong was being choked by salt. ABC Splash

Characteristics of SALT as a pollutant.

Effects on the environmentHuman environment.

Salinity: Australia’s silent flood. ABC

Characteristics of SALT as a pollutant.

Effects on human health

In most people, the kidneys have trouble keeping up with the excess sodium in the bloodstream. As sodium accumulates, the body holds onto water to dilute the sodium. This increases both the amount of fluid surrounding cells and the volume of blood in the bloodstream. Increased blood volume means more work for the heart and more pressure on blood vessels. Over time, the extra work and pressure can stiffen blood vessels, leading to high blood pressure, heart attack, stroke,. It can also lead to heart failure. There is also some evidence that too much salt can damage the heart, aorta, and kidneys without increasing blood pressure, and that it may be bad for bones, too. Harvard School of Public Health

ToxicityThe measure of harm (death or illness) a substance can cause in humans and other living things. Toxicity is defined as acute and chronic respectively this refers to single and repetitive exposure. (Include safe levels).

LD50Is the term used to describe the dose of a substance that is sufficient to kill a percentage (50%) of the specified test animal within a specified period. The smaller the LD50 dose the more toxic a substance is.The lethal dose figures refer to acute toxicity and do not give an indicator of cumulative effects over time.

Salt is a chemical compound (electrolyte) made up of sodium and chloride. It is commonly used to preserve and flavour foods, and is the main source of sodium in our diet. A small amount of salt is important for good health – it helps to maintain the correct volume of circulating blood and tissue fluids in the body. However, most people consume much more sodium than they need for good health. The kidneys are the main regulators of sodium levels in the body. Too much sodium can cause high blood pressure and many other health conditions… Betterhealth.vic.gov.au

Excessive sodium intake has been linked to high blood pressure, as well as other conditions, such as:• heart failure• kidney problems and kidney stones• oedema (fluid retention)• stroke• stomach cancer• left ventricular hypertrophy (thickening of heart muscle)• osteoporosis.A high level of salt intake increases the amount of calcium excreted in the urine, which may alsocontribute to osteoporosis and increased risk of fracture. Betterhealth.vic.gov.au

Characteristics of SALT as a pollutant.

Effects on human healthExposureThe degree of time spent near or in contact with the pollutant. The level of exposure is related to the properties of the pollutant.

Pathways● Inhalation: when toxicants make their way into

the human body through the lungs.● Ingestion: when toxicants make their way into

the human body through the stomach.● Absorption: when toxicants make their way into

the human body through the skin.

Types of exposure and toxicity.● Chronic Exposure/Chronic Toxicity: repeated

exposure and/or absorption over a long period of time.

● Acute Exposure/Acute Toxicity: a single, severe case of exposure, absorption and harm caused.

Around 75 per cent of the salt in our diet comes from processed foods. Nutritionists recognise that it may be difficult for many people to reduce their salt intake to the ideal level, given our current food supply. Heart Foundation advice is that all Australians should at least reduce their salt intake to less than 6 g of salt a day (approximately 2,300 mg of sodium a day) as a first step towards reaching the recommended levels. This is approximately 1½ teaspoons of salt. Betterhealth.vic.gov.au

Characteristics of SALT as a pollutant.

PersistencePersistenceA property of a pollutant which relates to the time that the pollutant takes to break down. Substances that are not easily broken down are said to be persistent. A pollutant is degradable if it breaks down with sunlight, soil, water or in chemical reactions.

Regulation in the human bodyPersistence in the environmentRepairing salinity affected environmentsEnvironmental flows to remove saline water from rivers.

Salt is readily excreted from the human body and as such is not persistent. It is removed from the blood by the kidneys and excreted in the urine and through pores in our skin as sweat. In the environment salt can be more persistent, not because it cannot be broken down, but because it can be more difficult to remove - especially in the case of dryland and irrigation salinity. To remove salinity from these environments, ground water levels need to be reduced. This means planting deep rooted, salt tolerant natives such as perennial native grasses, salt bush and river red gums. In the case of irrigation salinity, it also means using less water. Salinity in waterways can be flushed out using environmental flows, or natural floods, diluting the saline water and transporting it to the sea.

Characteristics of SALT as a pollutant.

SinksPollution SinksA place or process that removes, stores or absorbs the pollutant. Wetlands are a pollutant sink for heavy metals and other materials. Atmospheric carbon dioxide dissolves in sea and is stored in organic matter such as plants and vegetation.

Salt interception schemes

The MDBC operates eight jointly funded salt interception schemes (SIS) along the Murray River, from Waikerie in South Australia to Pyramid Creek in Victoria. These schemes intercept saline groundwater flows and saline surface drainage that would have otherwise entered the River.

Barr Creek Drainage Disposal Scheme (Victoria)

The Barr Creek Drainage Diversion Scheme has once again been effective in reducing base salt loads in the Murray River by diverting drainage flows and intercepting saline groundwater from the Barr Creek to the Tutchewop disposal basins. During the year the scheme operated according to the agreed rules and diverted approximately 11 078 ML of drainage water, containing approximately 54 112 tonnes of salt, to the disposal basins. This represents approximately 96 per cent of the flow and salt load in the Barr Creek catchment that would otherwise have reached the Murray River.

The $13 million salt interception scheme on the upper reaches of Pyramid Creek will lower the adjacent groundwater table, preventing about 22 000 tonnes of salt from entering the creek each year. This will result in reduced salinity in downstream waterways including the Loddon River, the Ramsar-listed Kerang Lakes and the Murray River.

There are three types of sinks for salinity in inland Australia: salt lakes (groundwater evaporation), salt interception schemes (pumping away from rivers) and export to the sea.