Nitrogen (N)
Nitrogen is an essential element for both
plants and animals to survive. It enters waterways naturally either
from the breakdown of dead organic matter or via atmospheric nitrogen
gas fixation by specially adapted plants. Excess nitrogen in rivers
enhances nutrient enrichment, leading to algal blooms, fish kills and
weed infestation. High levels of dissolved forms of nitrogen (nitrate,
nitrite and ammonia/ammonium) can also be toxic to many aquatic
organisms and can prevent the water from being used as a potable
supply. Anthropogenic sources of nitrogen include fertilisers, animal
droppings, combustion of fossil fuels and plant debris.
Total nitrogen is a measure of all forms
of nitrogen in the water including ammonia, nitrate, nitrite and
organic nitrogen. Ammonia can be a nutrient or a toxicant. Ammonium is
the ionised form and is a non-toxic nutrient and Ammonia is the
unionised form and is a toxin. Sources of ammonia include a range of
industrial processes, agricultural fertilisers and the decomposition of
organic wastes. Total oxidised nitrogen is the sum of the oxidised
forms of nitrogen, and includes nitrite and nitrate. Total oxidised
nitrogen is a stimulant for algal growth and is a common ingredient in
fertilisers.
Phosphorus (P)
Phosphorus is an essential element for
both plants and animals to survive. It enters waterways either from the
breakdown of dead organic matter or via the gradual weathering and
leaching of rocks and soils in the catchment. Excess phosphorus in
rivers enhances nutrient enrichment leading to algal blooms, fish kills
and weed infestation. Elevated phosphorus levels in rivers are
typically associated with pollution from fertilisers, detergents,
industrial waste or plant and animal waste.
Total phosphorus is a measure of all the
dissolved, sediment-bound, precipitate and organic forms of phosphorus
in the water including the bioavailable (soluble reactive phosphorus)
and unavailable (or potentially available) forms. Soluble reactive
phosphorus measures only the dissolved phosphorus in water and provides
a measure of the immediately available phosphate in the system at the
time of sampling; it is also referred to as orthophosphate. As this
form of phosphorus is readily available for biological uptake it is
more likely to stimulate algal blooms. This can lead to more decaying
vegetation which alters river characteristics, including elevated
temperature, reduced oxygen and fish kills.
pH
pH is a measure of how acidic or basic a
water sample is. Its uses a logarithmic scale ranging from 0 (extremely
acid) to 14 (extremely basic) with 7 representing neutral conditions.
Most life forms generally tolerate pH in water between 6.5 and 8, but
outside of these ranges many problems begin to occur, especially if the
change in pH is sudden. Lower pH extremes can result in the death of
many aquatic organisms and can also result in mobilisation of toxic
heavy metals. Higher pH extremes can result in precipitation reactions
(see total suspended solids - TSS) and can also kill aquatic organisms.
Some waterways in Western Australia are known to be naturally acidic
(due to organic acids in peaty sub-soils) or naturally basic (due to
carbonate deposits). Mining and industry wastes and land clearing
activities are also known to have contributed to pH disturbances in
some areas.
Turbidity
Turbidity represents the extent of light
penetration through the water column. It can be measured with a
turbidity photometer or with a Secchi disc. Turbid or 'cloudy' water
can be the result of high levels of suspended or colloidal particles
including clay, silt, sand, organic matter, algae and micro-organisms.
It may also be the result of dissolved metals (e.g. iron or copper) or
dissolved organic matter (e.g. tannins) which gives the water a
coloured appearance. Highly turbid rivers influence the biologic
productivity by limiting light availability and can also irritate fish
if fine particulates are present. It may indicate erosion problems,
nutrient enrichment or other types of agricultural, commercial or
industrial pollution.
Total suspended solids (TSS)
Suspended solids are a measure of the
total amount of particulate material in a water sample that include all
types of sediments (silt, clay, sand), precipitates, colloids,
inorganic and organic matter larger than 0.45 micrometers. They are
produced in a variety different ways including erosion by wind and
water, construction and demolition operations and the wear of roads and
vehicles. High levels of suspended solids can make the water more
turbid (see Turbidity) and may indicate erosion problems in the
catchment. Fine particulate matter can also provide a means of
transport for nitrogen, phosphorus, toxic heavy metals, pesticides,
bacteria and may be an irritant for some fish. Longer term impacts of
high suspended solids include alteration of in-stream dynamics and
receiving water bodies (e.g. blocking channels and filling river
pools), potential flooding problems and loss of aquatic flora and fauna
habitat.
Disolved organic carbon
Dissolved organic carbon is naturally
derived from the breakdown of organic matter (plant and animal
material) in the catchment or the water column. Many waterways in
south-west Western Australia are typically high in dissolved organic
carbon and are stained deep brown to black with humic compounds. Other
organic molecules including free sugars, amino acids, fatty acids,
proteins and carbohydrates also constitute dissolved organic carbon.
Many of these smaller organic molecules can be consumed by bacteria and
fungi which, in turn, provide a food source for higher organisms. High
levels of dissolved organic carbon may also be indicative of organic
(waste) pollution or a stagnant river system.
Disolved oxygen
Dissolved oxygen is a measure of the
amount of oxygen gas dissolved in a water sample. Oxygen is essential
for most aquatic organisms to live. Diffusion of oxygen from the
atmosphere into the water is extremely slow and is dependent on
atmospheric conditions, water temperature, turbulence and mixing of the
water column. Hypoxic conditions (low levels of dissolved oxygen) may
be due to stagnant waters, high rates of plant and animal respiration
or bacterial decomposition of organic matter. Fish kills and nutrient
release from sediments are common under these conditions and other
sediment bound toxicants such as heavy metals can also be released into
the water column. Low dissolved oxygen concentrations can also increase
the toxicity of certain heavy metals such as zinc, lead, copper,
cyanide, hydrogen sulphides and ammonia (ANZECC & ARMCANZ,
2000). Hyperoxic conditions – supersaturated (excess)
dissolved oxygen – can be associated with temperature
increases, turbulent water flow or by high rates of phytoplankton
photosynthesis. These conditions can also lead to fish deaths with
symptoms similar to 'the bends'.
A relative dissolved oxygen
concentration of between 80–120% is required to sustain
aquatic life in lowland rivers (ANZECC & ARMCANZ 2000). For the
purpose of reporting this data the measurement of dissolved oxygen
concentration is shown in mg/L as it represents a more absolute value
that would affect aquatic life. It is less dependant on factors such as
water temperature and salinity (for example), than that of percentage
saturation. As dissolved oxygen can fluctuate greatly over 24 hours, it
is preferable to measure dissolved oxygen over 2–3 days
(ANZECC
& ARMCANZ 2000). This type of dissolved oxygen monitoring was
not conducted as part of these monitoring programs.
EC (units mS/cm)
Electrical conductivity is the total
concentration of inorganic ions (particularly sodium, chlorides,
carbonates, magnesium, calcium, potassium and sulphates). Conductivity
is often used as a measure of salinity. The conductivity level can
directly affect the use of the water. For example, different types of
plants have varying tolerance levels to salinity, as do different
animals, which is important when considering the watering of stock.
HEAVY METALS (Al, As, Cd, Cr, Co, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Zn)
Aluminium (Al)
Aluminium is toxic to aquatic organisms
and its toxicity increases as pH decreases. Aluminium may be present in
water through natural leaching from soil and rock, but its
concentration is increased in surface water and in groundwater under
acidic conditions, and this may be influenced by the action of acid
sulphate soils.
Arsenic (As)
Arsenic is highly toxic to aquatic life
and bioaccumulates in some animals. Arsenic is very persistent in the
environment and can inhibit plant growth. Sources of arsenic include
the combustion of fossil fuels, primary production of iron, steel,
copper, nickel and zinc, use of pesticides, weed killers and
fungicides, wood treatment products and burning of treated wood. High
arsenic concentrations can also be found in acidic groundwater.
Cadmium (Cd)
Cadmium is highly toxic and accumulates
in the liver and kidneys of animals. It is a known carcinogen (World
Health Organisation 1984). Sources of cadmium include combustion, wear
of tyres and brake pads, possible combustion of lubricating oils,
industrial emissions, agricultural use of sewage sludge, fertilisers
and pesticides, corrosion of galvanised metals and landfill leachate
(presumably contaminated by discarded rechargeable batteries).
Chromium (Cr)
Chromium occurs in both trivalent and
hexavalent forms. Trivalent chromium is considered to be practically
non-toxic. In chlorinated or aerated water, hexavalent chromium is the
predominant form and is toxic to aquatic organisms and a carcinogen to
animals and humans. Chromium in stormwater is mostly associated with
suspended solids.
Sources of chromium include the chemical
manufacturing industry (e.g. dyes for paints, rubber and plastic
products), the metal finishing industry (e.g. chrome plating),
manufacturers of pharmaceuticals, wood, stone, clay and glass products,
electrical and aircraft manufacturers, steam and air conditioning
supply services, cement producing plants (cement contains chromium),
incineration of refuse and sewage sludge, combustions of oil and coal.
Cobolt (Co)
Cobalt exists most commonly as Co2+
or Co3+, in water, although other forms are
possible. It is adsorbed to suspended particles and sediment but its
solubility may be increased by complexing with organic matter, such as
from sewage works (ANZECC & ARMCANZ 2000). Cobalt and its
compounds are highly persistent in water and the environment. They have
an acute (short-term) and chronic (long-term) toxicity on aquatic life,
where they can bioaccumulate in the tissues of some aquatic organisms
and plants. Cobalt can have both beneficial and harmful effects for
humans, where small amounts are essential for good health but larger
doses can be harmful.
Sources of cobalt include the chemical
manufacturing industry (e.g. additives of paint, ceramics, glass, ink,
enamels and fertiliser), automotive repair shops (e.g., batteries) and
the metal industry (in the production of steel and other alloys). Small
amounts have also been found in motor vehicle exhausts.
Copper (Cu)
Copper is commonly found as the Cu2+
ion in natural waters. This ion is potentially very toxic to aquatic
life, both acutely and chronically. It is quickly accumulated in both
plants and animals. The toxicity of copper greatly increases with
decreasing water hardness and dissolved oxygen concentrations. Sources
of copper include wear of vehicle tyres and brake pads, metal industry
and domestic products, corrosion of brass and copper pipes, sewage
treatment plant effluent, electroplating wastes, pesticides,
fungicides, algicides and brake lining.
Iron (Fe)
Iron may be present in natural waters in
varying quantities depending upon the geology of the area and the
chemical components of the waterway. Iron is generally present in the
ferrous (Fe2+) or ferric (Fe3+)
states. In surface waters iron is generally present in the ferric
state, in reducing waters the ferrous form can persist. In the presence
of oxygen, iron is often found as colloidal suspensions of ferric
hydroxide, which may remain suspended in water or settle onto sediments
and aquatic plants, which can cause problems with turbidity, decreased
light penetration and smothering of benthic organisms (ANZECC &
ARMCANZ 2000).
Lead (Pb)
Lead is a cumulative, general metabolic
poison which bioaccumulates in animals, plants and bacteria and is
highly poisonous to both plants and animals. Lead persists in the
environment for long periods and does not readily breakdown. The main
source of lead in urban runoff is from petrol additives. Other sources
include tyres, industrial and mining emissions, manufacturing and
smelting industries, lead water pipes and soldered joints, burning of
fossil fuels, plastic pipes and guttering, and paints.
Manganese (Mn)
Manganese is commonly associated with
dissolved ferrous iron and is a naturally occurring constituent of
groundwater. Other sources of manganese in waterways include
agricultural and gardening applications, alkaline and dry cell
batteries, some fertilisers and some disinfectants.
Mercury (Hg)
Mercury is a highly toxic element that is
found both naturally and as an introduced contaminant in the
environment. Both mercury and its compounds have high acute and chronic
toxicity on aquatic life and are highly persistent in water and the
environment. Although its potential for toxicity in highly contaminated
areas such as Minamata Bay, Japan, in the 1950s and 1960s, is well
documented, research has shown that mercury can be a threat to the
health of people and wildlife in many environments that are not
obviously polluted. The risk is determined by the likelihood of
exposure, the form of mercury present (some forms are more toxic than
others, such as methyl-mercury which have been shown to bioaccumulate
in the tissues of fish and shellfish), the geochemical and ecological
factors that influence how mercury moves and changes that form in the
environment.
Mercury is an extremely rare element in
the Earth's crust. Natural sources such as volcanoes are responsible
for approximately half of atmospheric mercury emissions. Anthropogenic
sources include the combustion of fossil fuels (particularly coal),
gold production, metal smelting, cement production, waste disposal and
incineration, the production of caustic soda, batteries, iron and
steel. Products containing mercury include: automotive parts,
batteries, fluorescent bulbs, medical products, thermometers and
thermostats.
Molybdenum (Mo)
Molybdenum is used in the manufacture of
specialty steel products and electrical apparatus. Its compounds are
used in the manufacture of glass, ceramics, fertilisers and pigments
(ANZECC & ARMCANZ 2000).
Nickel (Ni)
Nickel is relatively non-toxic and there
is little evidence of bioaccumulation. Nickel in stormwater is usually
associated with suspended solids and organic matter. Sources of nickel
include corrosion of welded metal plating, wear of moving parts in
engines, electroplating and alloy manufacture and equipment used for
food production.
Selenium (Se)
Although selenium is an essential trace
element, it is toxic if taken in excess. Selenium occurs naturally in a
number of inorganic forms. In soils, selenium most often occurs in
soluble forms like selenate (analogous to sulphate), which are leached
into rivers very easily by runoff. Selenium has a biological role, and
is found in organic compounds. Selenium is most commonly
produced from selenide in many sulphide ores, such as those of copper,
silver, or lead. It is obtained as a by-product of the processing of
these ores, from the anode mud of copper refineries and the mud from
the lead chambers of sulphuric acid plants. These muds can be processed
by a number of means to obtain free selenium. Natural sources of
selenium include certain selenium-rich soils, and selenium that has
been bioconcentrated by certain toxic plants. Anthropogenic sources of
selenium include coal burning and the mining and smelting of sulphide
ores.
Zinc (Zn)
Zinc bioaccumulates easily in plants and
animals and is mostly associated with dissolved solids, although it
will adsorb to suspended particles. Sources of zinc in stormwater
include wear from tyres and brake pads, combustion of lubricating oils,
and corrosion of galvanised roofs, pipes and other metal objects.
Total water hardness (for calculating hardness adjusted trigger values for metals)
Total water hardness, expressed as
calcium carbonate (CaCO3), is the combined
concentration of earth-alkali metals, predominantly magnesium (Mg2+),
calcium (Ca2+), and some strontium (Sr2+).
The source of this hardness is limestone dissolved by water that is
rich in carbon dioxide. Hardness levels range from <60 mg/L
(soft) to >400mg/L (extremely hard).
Water hardness can have an effect on the toxicity of certain heavy
metals (chromium, copper, lead, nickel and zinc).
HYDROCARBONS
Polycyclic aromatic hydrocarbon (PAH)
PAH comprise a group of over 100
different chemicals that are produced during the incomplete burning of
fuels, garbage or other organic substances such as tobacco, plant
material or meats. These combustion processes produce a mixture of
chemicals with soot being a well-known example. Most PAH in the
environment are from incomplete burning of carbon-containing materials
including oil, wood, garbage or coal. Automobile exhaust, industrial
emissions and smoke from burning wood, charcoal and tobacco contain
high levels of PAH. Materials containing PAH may also directly enter
the water system via release of crude oil and petroleum products
(ANZECC & ARMCANZ 2000). Some of these PAH are manufactured for
research or are used in medicines, dyes, plastics and pesticides such
as naphthalene found in mothballs. PAH can also be found in coal tar,
bitumen, crude oil, creosote and roofing tar.
BTEX compounds (Benzene, Toluene, Ethyl-benzene, Xylene)
Benzene, toluene, ethyl-benzene and
xylene (collectively known as BTEX) are the simplest C6-C9 aromatic
hydrocarbons. They have many industrial applications such as solvents
used for adhesives, resins, fibres, pesticides and ink, as industrial
cleaners and degreasers, as thinners for paints and lacquers and as
fuel additives. BTEX is commonly associated with contaminated petroleum
sites in soils and groundwater (ANZECC & ARMCANZ 2000). BTEX
compounds are volatile hydrocarbons and degrade quickly, so their
presence in water samples can indicate recent pollution events.
Total petroleum hydrocarbons (recoverable)
Total petroleum hydrocarbon is a term
used to describe a large family of several hundred chemical compounds
that originate from crude oil. Low concentrations of hydrocarbons can
be highly toxic to aquatic organisms and in confined environments,
biodegradation of hydrocarbons will result in the reduction in
dissolved oxygen concentrations and there can be a localised build-up
of toxic fractions (ANZECC & ARMANZ 2000). It is reported as
different groups of carbon chain lengths (C6-C9; C10-C14; C15-C28 and
C29-C36) according to the methods used for analysis in the laboratory.
Surfactants (as MBAS)
Surfactants are complex mixtures
containing a variety of chemical compounds, particularly surface-active
agents, builders, bleaches and additives, blended for specific
performance characteristics. Surfactants are generally nutrient-rich
and toxicity tests have shown that even low concentrations can be toxic
to aquatic organisms.
No comments:
Post a Comment