Download Background on Chemical Parameters

Background on Chemical Parameters
Dissolved Oxygen
Oxygen is important to all life. We breathe air that contains about 20% oxygen. Aquatic life needs
oxygen to live. Aquatic life uses oxygen that is dissolved in the water and is in much smaller
quantities than in the air. Oxygen, in water, is measured as dissolved oxygen (DO). If more
oxygen is consumed than is produced, dissolved oxygen levels decline and some sensitive
animals may move away, weaken, or die.
Through rain, wind, waves, and currents, oxygen is mixed in from the air above. Water that
moves faster contains more dissolved oxygen because it has more contact with the air than still
water. Underwater plants and algae also contribute oxygen that is given off during
photosynthesis.
Weather, temperature and salinity affect amounts of dissolved oxygen (DO). Cold, fresh water
holds more oxygen than warm or salty water. If DO levels are severely low, large quantities of fish
may die. Low DO is also caused by fertilizer and manure runoff from streets, lawns and farms.
Fertilizers and fecal matter encourage the growth of too much algae, which uses up the oxygen
quickly. Plants and animals die and are decayed by bacteria, which also uses up a great deal of
oxygen.
The stream system gains oxygen from the atmosphere and from aquatic plants as a result of
photosynthesis. Running water, because of its churning, dissolves more oxygen than still water.
Respiration by aquatic animals, decomposition, and various other chemical reactions consume
oxygen.
DO levels fluctuate seasonally and over a 24-hour period. They vary with water temperature and
altitude. Cold water holds more oxygen than warm water (see table) and water holds less oxygen
at higher altitudes. Thermal discharges, such as water used to cool machinery in a manufacturing
plant or a power plant, raise the temperature of water and lower its oxygen content. Aquatic
animals are most vulnerable to lowered DO levels in the early morning on hot summer days when
stream flows are low, water temperatures are high, and aquatic plants have not been producing
oxygen since sunset.
Biochemical Oxygen Demand
When organic matter decomposes, microorganisms (such as bacteria and fungi) feed upon this
decaying material and eventually it becomes oxidized. Biochemical oxygen demand, or BOD,
measures the amount of oxygen consumed by microorganisms in the process of decomposing
organic matter in stream water.
BOD directly affects the amount of dissolved oxygen in rivers and streams. The more rapidly
oxygen is depleted in the stream, the greater the BOD. This means less oxygen is available. The
detriment of high BOD is the same as low dissolved oxygen: aquatic organisms become stressed,
suffocate, and die.
Sources of BOD include leaves and woody debris; dead plants and animals; animal manure;
effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing
plants; failing septic systems; and urban storm water runoff.
Fecal Coliform
Fecal coliform bacteria are found in the feces of human beings and other warm-blooded animals.
Fecal coliform by themselves are generally not pathogenic (a biological agent, such as a
bacterium or virus, that can cause a disease). Pathogenic organisms include bacteria, viruses
and parasites that cause diseases and illnesses. Fecal coliform bacteria are already inside of
you! They occur naturally in the human digestive tract and aid in the digestion of food. However,
when a human being or other warm-blooded animal is infected with disease, pathogenic
organisms are found along with fecal coliform bacteria.
If fecal coliform counts are high (over 200 colonies/100 ml of a water sample) in a river or lake,
there is a greater chance that pathogenic organisms are also present. If you are swimming in
waters with high levels of fecal coliform, you have a greater chance of developing a fever, nausea
or stomach cramps from swallowing disease-causing organisms, or from pathogens entering the
body through cuts in the skin, the nose, mouth, or ears. Some examples of diseases and
illnesses that can be contracted in water with high fecal coliform counts include typhoid fever,
hepatitis, gastroenteritis, dysentery and ear infections.
Why not test pathogens? Pathogens are relatively scarce in water, making it time-consuming and
expensive to monitor them directly. Instead, we monitor fecal coliform because of the possible
correlation between fecal coliform and the probability of contracting a disease from the water.
Fecal Coliform Standards
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Drinking Water = 0 FC/100 mL
Swimming = 200 FC/100 mL
Partial body contact = 1000 FC/100 mL
Treated sewage effluent = less than 200 FC/100 mL
Fecal coliform bacteria are living organisms, unlike the other conventional water quality
parameters. The fecal coliform bacteria multiply rapidly when conditions are good for growth and
die in large quantities when they are not.
E. Coli
E. coli is a species of fecal coliform bacteria that is specific to fecal material from humans and
other warm-blooded animals. EPA recommends E. coli as the best indicator of health risk from
water contact in recreational waters; some states have changed their water quality standards and
are monitoring accordingly.
Enterococci
Enterococcus bacteria are a valuable indicator for determining the extent of fecal contamination
of recreational surface waters. Studies have shown that swimming associated gastroenteritis is
related directly to the quality of the bathing water and that enterococci are the most efficient
bacterial indicator of water quality. Water quality guidelines have been proposed based on
enterococcal density.
Recreational fresh waters should have less than 33 enterococci/100ml and marine waters should
have less than 35 enterococci/100ml.
Enterococci are a subgroup within the fecal streptococcus group. Enterococci are distinguished
by their ability to survive in salt water, and in this respect they more closely mimic many
pathogens than do the other indicators. Enterococci are typically more human-specific than other
fecal groups. EPA recommends enterococci as the best indicator of health risk in salt water used
for recreation and as a useful indicator in fresh water as well.
pH
*Chart from EPA
pH is the percentage of hydrogen ions (H+) in a solution. A solution is more acidic when it
contains more hydrogen ions. The level of acidity of the water is important to the plant and animal
life there. Most animals are adapted to living in neutral conditions. Changes in pH endanger the
lives the organisms in the water.
The level of acidity can be changed by human’s actions. Acid rain, a result of air pollution and
matter emitted from tailpipes and smokestacks affect the pH. When these things combine with
water in the atmosphere, they form sulfuric and nitric acids, then fall to the earth as acid rain,
snow, hail, and fog. This precipitation mixes with water already on the earth, in creeks, rivers,
ponds and wetlands. Other pollutants carried by runoff from the land, also change the acidity of
the water.
A pH of 7 is considered to be neutral. When the pH is less than 7, it is acidic; a pH greater than 7
is basic. A pH value between 7.0 and 8.0 are optimal for supporting a divers aquatic ecosystem.
A pH range between 6.5 and 8.5 is generally suitable.
Total Alkalinity
Alkalinity is a total measure of the capacity of water to neutralize acids. Alkalinity is not a pollutant
and is different from pH. pH measures the strength of an acid or base. Alkalinity indicates a
solution's power to react with acid and buffer its pH, the power to keep its pH from changing.
Alkalinity is important for fish and aquatic life because it protects or buffers against pH changes
(keeps the pH fairly constant) and makes water less vulnerable to acid rain. The main sources of
natural alkalinity are rocks, which contain carbonate, bicarbonate and hydroxide compounds.
Alkaline compounds in the water such as bicarbonates (baking soda is one type), carbonates,
and hydroxides remove H+ ions and lower the acidity of the water (which means increased pH).
They usually do this by combining with the H+ ions to make new compounds. Without this acidneutralizing capacity, any acid added to a stream would cause an immediate change in the pH.
Measuring alkalinity is important in determining a stream's ability to neutralize acidic pollution
from rainfall or wastewater. It's one of the best measures of the sensitivity of the stream to acid
inputs.
Rocks and soils, salts, certain plant activities, and certain industrial wastewater discharges
influence alkalinity in streams. Waters flowing through limestone regions, which are rich in
carbonates, generally have high alkalinity thus a good buffering capacity. In contrast, granite does
not have minerals that contribute to alkalinity. Areas full of granite have low alkalinity and poor
buffering capacity.
Total alkalinity is measured by measuring the amount of acid (e.g., sulfuric acid) needed to bring
the sample to a pH of 4.2. At this pH all the alkaline compounds in the sample are "used up." The
result is reported as milligrams per liter of calcium carbonate (mg/L CaCO3).
Water Temperature
The rates of biological and chemical processes depend on temperature.
Temperature affects the oxygen content of water (oxygen levels become lower as temperature
increases); the rate of photosynthesis by aquatic plants; the metabolic rates of aquatic organisms;
and the sensitivity of organisms to toxic wastes, parasites, and diseases.
Causes of temperature change include weather, removal of shading streambank vegetation,
impoundments (a body of water confined by a barrier, such as a dam), discharge of cooling
water, urban storm water, and groundwater inflows to the stream.
Thermal pollution is a way that the temperature of water can increase. Thermal pollution is an
increase in water temperature caused by adding relatively warm water to a body of water.
Thermal pollution can come from stormwater running off warmed urban surfaces (streets,
sidewalks, parking lots) and industries that discharge warm water from their facilities that was
used to cool machinery.
Nitrate/Nitrite
Nitrate is found in nature in very small amounts because of the ongoing growth and decay
process. When plants and animals die and decompose, ammonia is produced. Bacteria usually
turn the ammonia into nitrate (NO3). Pollutants such as sewage or manure however, contain
much higher levels of nitrates. High levels of nitrate may get into groundwater or streams from
fertilized fields, lawns, golf courses, from septic system effluent, or from runoff of manure.
Nitrate is a nutrient that helps plants to grow. An excess of nitrates in the water can result in a
rapid growth of algae and other plants. A massive growth of aquatic plant life can change the
water significantly. Water becomes murky, and the water temperature warms. When the plant life
dies and starts to decompose, bacteria use up all the oxygen. The oxygen level gets so low that
many types of fish and insects can no longer survive in the lake. Excess nitrates can start a chain
reaction that has very serious effects.
Nitrates are a form of nitrogen, which is found in several different forms in terrestrial and aquatic
ecosystems. These forms of nitrogen include ammonia (NH3), nitrates (NO3), and nitrites (NO2).
Together with phosphorus, nitrates in excess amounts can accelerate eutrophication, causing
dramatic increases in aquatic plant growth and changes in the types of plants and animals that
live in the stream. This, in turn, affects dissolved oxygen, temperature, and other indicators.
Excess nitrates can cause hypoxia (low levels of dissolved oxygen) and can become toxic to
warm-blooded animals at higher concentrations (10 mg/L) or higher) under certain conditions.
The natural level of ammonia or nitrate in surface water is typically low (less than 1 mg/L); in the
effluent of wastewater treatment plants, it can range up to 30 mg/L.
Sources of nitrates include wastewater treatment plants, runoff from fertilized lawns and cropland,
failing on-site septic systems, runoff from animal manure storage areas, and industrial discharges
that contain corrosion inhibitors.
Total Phosphorus
*Chart from EPA
Phosphates are a plant nutrient that can also be a pollutant. Phosphates in water contribute to the
growth of algae, similar to nitrates. Adding phosphates to a body of water can accelerate plant
growth and eventually damage an ecosystem by draining the oxygen levels when the plants
decompose.
Phosphorous is usually present in natural waters as phosphate (PO-4-P). Phosphate has two
different forms in our environment: organic phosphate, which is a part of living plants and
animals, their by-products and their remains; and inorganic phosphate, which can be bound to
soil particles or present in laundry detergents.
Phosphorous is an essential element for life, an important nutrient for plants to grow. The number
of aquatic plants growing in a particular area is dependent on the amount of phosphorous
available. In an aquatic ecosystem, inorganic phosphate is rapidly taken up by algae and larger
plants, resulting in algal blooms, increased biochemical oxygen demand and significant impacts
on water quality.
Phosphorous from natural resources, such as forest fires and fallout from volcanic eruptions, is
insignificant when compared to human-caused enrichments of water from nutrients such as
phosphorous. Phosphorous is introduced into the environment from human activities such as:
human and animal wastes, fertilizers, industrial wastes and human disturbance of the land and its
vegetation.
Because phosphorous acts as a plant nutrient, it also causes eutrophication. Eutrophication is the
enrichment of water with nutrients, usually phosphorous and nitrogen, which stimulates the
growth of algal blooms and rooted aquatic vegetation. Eutrophication promotes more plant growth
and decay, which in turn increases biochemical oxygen demand. Phosphates in excess amounts
can have a significant impact on water quality.
Ortho-phosphate
The term "orthophosphate" is a chemistry-based term that refers to the phosphate molecule all by
itself. "Reactive phosphorus" is a corresponding method-based term that describes what you are
actually measuring when you perform the test for orthophosphate. Because the lab procedure
isn't quite perfect, you get mostly orthophosphate but you also get a small fraction of some other
forms.
Total Solids
Total solids are the sum of the dissolved solids and the suspended solids contained in a water
sample. Dissolved solids are the portions of solid matter found in a water sample that pass
through a filter. Suspended solids are those solids trapped by a filter and can include anything
from silt and plankton to industrial wastes and sewage.
High concentrations of total solids in a river or lake can lower water quality and cause water
balance problems for individual organisms. Low concentrations of total solids may limit the growth
of aquatic life.
Optimal Levels of Total Solids
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A total solids level of 25 mg/l or less is optimal
25-80 mg/l is acceptable
80-400 mg/l is poor
A total solids load of over 500 mg/l can be fatal to salmon over several weeks
Total Dissolved Solids
Total dissolved solids is the amount of particles that are dissolved in the water. It may include all
suspended solids that may or may not pass through a filter.
Dissolved solids may come from organic sources such as leaves, silt, plankton, and industrial
waste and sewage. Other sources come from runoff from urban areas, road salts used on street
during the winter, and fertilizers and pesticides used on lawns and farms. Dissolved solids may
come from inorganic materials such as rocks and air that may contain calcium bicarbonate,
nitrogen, iron phosphorous, sulfur, and other minerals. Since rainwater contributes to most of the
water in a watershed, it contributes to the amount of TDS in a watershed. Rainwater is almost
pure with less than 10 mg/L of TDS.
A constant level of minerals in the water is necessary for aquatic life. Changes in the amounts of
dissolved solids can be harmful because the density of total dissolved solids determines the flow
of water in and out of an organism’s cells. Many of these dissolved solids contain chemicals, such
as nitrogen, phosphorous, and sulfur, which are the building blocks of molecules for life.
Concentration of total dissolved solids that are too high or too low may limit the growth and may
lead to the death of many aquatic organisms. High concentrations of total dissolved solids may
reduce water clarity, which contributes to a decrease in photosynthesis and lead to an increase in
water temperature. Many aquatic organisms cannot survive in high temperatures. It is possible for
dissolved ions to affect the pH of the body of water, which in turn may influence the overall health
of many aquatic species. If TDS levels are high, especially due to dissolved salts, many forms of
aquatic life are affected. The salts act to dehydrate the skin of animals. High TDS concentrations
may add a laxative effect to the water or cause the water to have an unpleasant mineral taste.
Levels of Total Dissolved Solids
1. Drinking water may have a TDS reading of 25-250 mg/L. Drinking water should not exceed
500 mg/L TDS.
2. Distilled water will have a TDS reading that will range from 0.5-1.5 mg/L.
3. The amount of TDS ranges from 100-20,000 mg/L in rivers and may be higher in
groundwater.
4. Seawater may contain 35,00 mg/L of TDS.
5. Lakes and streams may have a TDS reading of 50-250 mg/L.
Conductivity
Conductivity is the measurement of a solution's ability to conduct an electrical current. Absolutely
pure water is actually a poor electrical conductor. It is the substances (or salts) dissolved in the
water, which determine how conductive the solution will be.
Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride,
nitrate, sulfate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium,
calcium, iron, and aluminum cations (ions that carry a positive charge). Organic compounds like
oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low
conductivity when in water. Conductivity is also affected by temperature: the warmer the water,
the higher the conductivity. For this reason, conductivity is reported as conductivity at 25 degrees
Celsius (25 C).
Environmental conditions such as drought, changing seasons, heavy rainfall, etc. can cause the
concentration of dissolved salts in water to vary significantly. These dissolved salts (i.e. calcium,
sodium, etc.) can directly affect plants health and over time, render even the best soil useless.
You can monitor your overall water quality by testing its electrical conductivity. The higher the
conductivity, the more salts are dissolved in your water. By comparing your conductivity readings
on a regular basis you can tell if any dramatic changes have occurred. Nutrient deficiencies are
possible when water is too pure (low conductivity) or if the relative concentration of some
nutrients are unbalanced (i.e.. Calcium/Magnesium).
Conductivity in streams and rivers is affected primarily by the geology of the area through which
the water flows. Streams that run through areas with granite bedrock tend to have lower
conductivity because granite is composed of more inert materials that do not ionize (dissolve into
ionic components) when washed into the water. On the other hand, streams that run through
areas with clay soils tend to have higher conductivity because of the presence of materials that
ionize when washed into the water. Ground water inflows can have the same effects depending
on the bedrock they flow through.
Discharges to streams can change the conductivity depending on their make-up. A failing sewage
system would raise the conductivity because of the presence of chloride, phosphate, and nitrate;
an oil spill would lower the conductivity.
The basic unit of measurement of conductivity is the mho or siemens. Conductivity is measured in
micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µs/cm). Distilled water
has a conductivity in the range of 0.5 to 3 µmhos/cm. The conductivity of rivers in the United
States generally ranges from 50 to 1500 µmhos/cm. Studies of inland fresh waters indicate that
streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm.
Conductivity outside this range could indicate that the water is not suitable for certain species of
fish or macroinvertebrates. Industrial waters can range as high as 10,000 µmhos/cm.
Turbidity
Turbidity is a measure of the relative clarity of water: the greater the turbidity, the murkier the
water. Turbidity increases as a result of suspended solids in the water that reduce the
transmission of light. Suspended solids are varied, ranging from clay, silt and plankton, to
industrial wastes and sewage.
So the water is dirty, what's the big deal?
1. With higher levels of turbidity, water loses its ability to support a diversity of aquatic
organisms.
2. Water becomes warmer as suspended particles absorb heat from the sunlight and cause
oxygen levels to fall. Remember- warm water holds less oxygen than cooler water!
3. Photosynthesis decreases because less light penetrates the water, resulting in even
further drops in oxygen levels.
4. The combination of warmer water, less light and oxygen depletion makes it impossible for
some forms of aquatic life to survive.
Suspended solids affect aquatic life in other ways as well. Suspended solids can clog fish gills,
reduce growth rates, decrease resistance to disease and prevent egg and larval development.
Particles of silt, clay and organic materials settle to the bottom, especially in areas of a river or
stream that are slow moving. These settled particles could smother the eggs of fish and aquatic
insects, as well as suffocate newly hatched insect larvae. Material that settles into the spaces
between rocks makes these microhabitats unsuitable for mayfly and stonefly nymphs, caddisfly
larvae and other aquatic insects living there.
Salinity
Salinity is the concentration of dissolved salts in the water. Aquatic animals are adapted to living
within certain salinity ranges. Sunfish, for example, common in ponds and freshwater streams,
could not survive in salt water. Animals living in salty conditions tend to be more tolerant of a
wider range of salinities. Many species of fish migrate from salt to fresh water to spawn.
Salinity is affected by weather, especially at the surface of the water. During dry seasons, water
evaporates, making salty water. When it rains, salty water is diluted by the added fresh water.
After a heavy rain, look for freshwater fish in normally saltier water. During a drought, saltwater
fish may be found.
Salinity is measured as a ratio of salts to water, and is expressed in parts per thousand (ppt),
which means the number of units (parts) of salts per thousand units of water. There are three
main categories of salinity: fresh water (0-0.5 ppt), brackish water (partly salty, or 0.5-30 ppt), and
salt water (full seawater, greater than 30 ppt).
From: http://www.green.org/files.cgi/435_Chem_Parameters.html