Environmental Engineering Reference
In-Depth Information
group of organisms. Benthic macroinvertebrates are aquatic organisms with-
out backbones that spend at least a part of their life cycle on the stream bot-
tom. Examples include aquatic insects (e.g., stoneflies, mayflies, caddisflies,
midges, beetles), as well as crayfish, worms, clams, and snails. Most hatch
from eggs and mature from larvae to adults. The majority of the insects
spend their larval phase on the river bottom and, after a few weeks to several
years, emerge as winged adults. The aquatic beetles, true bugs, and other
groups remain in the water as adults. Macroinvertebrates typically collected
from the stream substrate are either aquatic larvae or adults.
Macrophyte:
An aquatic plant that grows in or near water.
Magma:
Molten rock within the Earth from which igneous rock is formed by
cooling.
Magnetic survey:
Measurements of the Earth's magnetic field that are then mapped
and used to determine subsurface geology.
Magnetotellurics:
An electromagnetic method of determining structures below the
Earth's surface using electrical currents and the magnetic field.
Mantle:
The Earth's inner layer of molten rock lying beneath the Earth's crust and
above the Earth's core of liquid iron and nickel.
Marshlands:
Areas interspersed with open water, emergent vegetation (hydro-
phytes), and terrestrial vegetation (phreatophytes).
Matrix treatments:
Treatments used to restore or improve the natural permeability
of a reservoir following damage to the near-wellbore area. Matrix treat-
ments typically use hydrochloric or hydrofluoric acid to remove mineral
material reducing flow into the well.
Mature tree size:
The approximate tree size 40 years after being planted.
Mean power output (of wind turbine):
The average power output of a wind energy
conversion system at a given mean wind speed based on a Raleigh fre-
quency distribution.
Median:
The middle number of a dataset when the measurements are arranged in
ascending (or descending) order.
Medium pressure:
For valves and fittings, implies that they are suitable for working
pressures between 125 to 175 pounds per square inch.
Medium-temperature collectors:
Solar thermal collectors designed to operate in
the temperature range of 140 to 180°F but that can also operate at a tem-
perature as low as 110°F. The collector typically consists of a metal frame,
metal absorption panel with integral flow channels (attached tubing for liq-
uid collectors or integral ducting for air collectors), and glazing and insula-
tion on the sides and back.
Megavoltamperes (MVA):
Millions of voltamperes, which are a measure of appar-
ent power.
Megawatt (WM):
One million watts of electricity.
Megawatt-hour (MWh):
One thousand kilowatt-hours or 1 million watt-hours.
Mercaptan:
An organic chemical compound with a sulfur-like odor that is added
to natural gas before distribution to the consumer to give the natural gas a
distinct, unpleasant odor (like rotten eggs). This serves as a safety device by
allowing the gas to be detected when leaks occur.
