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Water Quality Parameters:
What We Sample For & Why
There are many different indicators
of stream health: biological, chemical, pathological, and physical.
The MMN collects data on the following parameters:
Fecal Coliform
Fecal coliform bacteria are an important indicator of potential
pathogens. The results are measured in colony-forming units (cfu)
per 100 milliliters. When fecal coliform counts are high, it is
likely that the water contains other pathogens that are harmful
to human health. Sources of fecal coliform include wild animal
droppings, combined sewer overflows, or illegal connections of
sewers to stormwater drains. The current Massachusetts Surface
Water Quality Standard (MASWQS) for bacteria is based on fecal
coliform.
E. coli
Escherichia coli, or E. coli, is a type of fecal coliform.
Recent studies by the US Environmental Protection Agency have
concluded that E. coli is a better indicator of the potential
risk to human health. The MA Department of Environmental Protection
will probably be changing the MASWQS for bacteria to E. coli.
Dissolved Oxygen
Dissolved oxygen is the measure of how much oxygen is available
in the water for intake by living creatures (fish, insects, etc.).
Results are measured first in parts per million (ppm). However,
the capacity for water to hold oxygen depends on temperature:
cold water can hold more ppm than warm water. Thus, the percent
saturation is also calculated. Causes of poor oxygen saturation
include high biological or chemical oxygen demand, poor hydrology
of the stream.
Nitrate + nitrite
Nitrate is a form of nitrogen, an essential nutrient for aquatic
life, however high levels of nitrates do pose a human health concern.
Results are measured in milligrams/liter. Nitrate enters rivers
and streams from soil, animal wastes, and decomposing plants.
The anthropogenic human sources are sewage, fertilizers, and pet
waste.
Total Phosphorus
Phosphorus is another essential nutrient. Phosphorus is frequently
the limiting agent to plant and algal growth; therefore, elevated
concentrations of phosphorus stimulate aquatic plant growth and
algal blooms. Phosphorus is measured in milligrams/liter. Sources
of phosphorus include animal wastes, human wastes, fertilizer,
detergents, erosion, and storm runoff.
Total Suspended Solids
Total Suspended Solids (TSS) is a measure of dust, dirt, sand,
and other particles stirred up in the water; it is measured in
milligrams per liter (mg/l). Excessive amounts of suspended solids
can bury fish and aquatic plants, and can make rivers and streams
unpleasant for recreation. In addition, other pollutants, such
as oil, heavy metals, and nutrients are frequently attached to
suspended solids. Thus, TSS can sometimes give a very rough indication
of the presence of these other pollutants in a stream.
Specific Conductivity
Specific conductance is a measure of the ability of water to pass
an electrical current. This ability depends on the presence of
ions. Conductivity is a general measure of water quality, with
elevated conductivity in freshwater systems potentially indicating
a source of excess dissolved solids (e.g. road salt used for deicing).
pH
pH is a measure if the acidity of water. pH stands for the negative
log (p) of the hydrogen ion concentration [H+] in a solution.
It is important because water that is too acidic or too basic
can be toxic to fish and other aquatic life. pH also plays an
important role in how other pollutants, such as heavy metals,
behave in the environment. It is measured on a scale from 1 to
14, with 1 being very acidic, 7 being neutral, and 14 being very
basic.
Temperature
Water temperature may not seem like "pollution", but
it is critical for rivers and streams to remain relatively cool
in order for fish and other aquatic life to survive. Water temperatures
can get too hot from a lack of shade along the riverbanks, discharges
of coolant water, or storm water running off hot pavement.
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