Net Present ValueThe value of a personal portfolio, product, or investment after depreciation and interest on debt capital are subtracted from operating income.
neutral detergent fiberOrganic matter that is not solubilized after one hour of refluxing in a neutral detergent consisting of sodium lauryl sulfate and EDTA at pH 7.
Night-sky impactAn interference with enjoyment of dark night skies resulting from light pollution.
Nighttime mean rural background levelNighttime (10 p.m. to 7 a.m.) average sound level in the rural environment, from all sources, rather than a particular noise that is of interest.
Nitrogen dioxide (NO<sub>2</sub>)(NO2)A toxic, reddish-brown gas that is a strong oxidizing agent, produced by combustion (as of fossil fuels).
Nitrogen fixationThe conversion of atmospheric nitrogen to biologically usable nitrates.
nitrogen oxides(NOx) A product of photochemical reactions of nitric oxide in ambient air, and the major component of photochemical smog.
Nitrogen Oxides (NOx)(NOx)The products of all combustion processes formed by the combination of nitrogen and oxygen.
NoiseAny unwanted sound that interferes with speech and hearing, causes damage to hearing, or annoys a person.
Noise criteriaQuantitative noise limits, below which it is acceptable for people to hear. Typically, noise criteria are specified in ordinances, regulations, or…
Non-point source pollutionPollution whose source is not specific in location; the sources of the pollutant discharge are dispersed, not well defined or constant.
non-renewable resourceA non-renewable energy resource is one that cannot be replaced as it is used. Although fossil fuels, like coal and oil, are in fact fossilized biomass…
Nonattainment AreaThe EPA's designation for an air quality control region (or portion thereof) in which ambient air concentrations of one or more criteria pollutants exceed…
Nonattainment area (NAA)(NAA)A geographic area in which air quality is worse than that allowed by federal air pollution standards.
Noncommercial speciesTree species that do not normally develop into suitable trees for conventional forest products because of small size, poor form, or inferior quality.
Nongame speciesThose species not commonly harvested either for sport or profit.
Nonmarket valueMost environmental goods and services, such as clean air and water, and healthy fish and wildlife populations, are not traded in markets, meaning that…
Nonpoint light sourceA light source that is sufficiently large in size and close enough to the viewer to appear as an illuminated surface rather than a star-like point of…
Nonpoint sourcesDiffuse pollution sources (i.e., without a single point of origin or not introduced into a receiving stream from a specific outlet).
Nonroad mobile sources (emissions)Sources such as farm and construction equipment, gasoline-powered lawn and garden equipment, and power boats and outdoor motors that emit pollutants.
Noxious weedsThose plants regulated by law or those that are so difficult to control that early detection is important.
Null hypothesisThe assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes.
Nurse plantsMature plants that create favorable conditions for seeds to germinate and for seedlings to survive and grow.
Octane enhancerAny substance that is added to gasoline to increase octane.
octane rating (octane number)A measure of a fuel’s resistance to self ignition, hence a measure as well of the antiknock properties of the fuel.
Off-highway vehicle (OHV) or off-road vehicle(OHV)Any motorized vehicle designed for or capable of cross-country travel on or immediately over land, water, sand, snow, ice, marsh, swampland, or other…
Off-road vehicle (OHV) designations(OHV)OPEN: Vehicles are allowed without restrictions. LIMITED: Vehicle travel off existing roads and trails would be allowed only for authorized or permitted…
Off-site facilityA hazardous waste treatment, storage, or disposal area that is located away from the generating site.
offsetYou offset an options or futures position by taking a second position in a contract with identical terms, buying if you sold initially or selling if you…
Oil and gas leasing (on BLM land)The BLM leases oil and gas rights to explore for and produce oil and gas resources from federal lands or mineral rights owned by the federal government.
Old growthTimber stands with the following characteristics: large mature and over-mature trees in the overstory, snags, dead and decaying logs on the ground and a…
Onroad mobile source (emissions)Any mobile source of air pollution such as cars, trucks, motorcycles, and buses that travels on roads and highways.
OpacityThe degree to which smoke or particles emitted into the air reduce the transmission of light and obscure the view of an object in the background.
Organic compoundAn organic compound contains carbon chemically bound to hydrogen. Organic compounds often contain other elements (particularly O, N, halogens, or S).
Organic compoundsChemical compounds based on carbon chains or rings and also containing hydrogen, with or without oxygen, nitrogen, and other elements.
Organic levelThe amount of organic matter prescribed to be left after logging.
OSHASee Occupational Safety and Health Administration.
OstracodsGroup of small crustaceans with a bivalved carapace which can be closed to completely cover the body; important planktonic fish food.
OutflowThe volume of growing cells that is removed from a bioreactor during a continuous fermentation process.
oven dry tonAn amount of wood that weighs 2000 lb at 0% moisture content.
Oven dry ton (ODT)(ODT)An amount of wood that weighs 2,000 pounds at zero percent moisture content.
Overbank depositsFine-grained sediment (silt and clay) deposited from suspension on a floodplain by floodwaters from a stream channel.
OverdraftWhen the amount of money withdrawn from a bank account is greater than the amount actually available in the account, the excess is known as an overdraft…
Overnight capital costThe capital cost of a project if it could be constructed overnight. This cost does not include the interest cost of funds used during construction.
OverstoryThe portion of the trees forming the upper or uppermost canopy in a forest stand.
OxygenateA cleaner-burning additive in a fuel—usually containing hydrogen, carbon, and oxygen. Examples are ethers and alchohols, such as ethanol and methanol.
OzoneTropospheric ozone (ground-level ozone), or smog, is formed when volatile organic compounds, oxygen and nitrogen oxides react in the presence of sunlight.
Ozone (O3)A strong-smelling, reactive, toxic, chemical gas consisting of three oxygen atoms chemically attached to each other.
Paleontological resourcesFossilized remains, imprints, and traces of plants and animals preserved in rocks and sediments since some past geologic time.
PaleozoicAn era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic, spanning the time between 542 and 251 million years ago.
Palm oasis(1) A desert habitat with permanent water or a water table near the surface that supports a canopy of palm trees.
Palustrine wetlandsShallow freshwater wetlands that often support plant communities of trees, shrubs, emergent plants, mosses, or lichens.
Pan evaporationA measurement that combines or integrates the effects of several climate elements: temperature, humidity, solar radiation, and wind.
Parabolic TroughA solar energy conversion device that uses a trough covered with a highly reflective surface to focus sunlight onto a linear absorber containing a working…
Partial cutA harvest method in which portions of a stand of timber are cut during a number of entries over time. Compare precommercial thinning.
ParticulateA small, discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions.
Particulate emissionsFine liquid or solid particles discharged with exhaust gases. Usually measured as grains per cubic foot or pounds per million Btu input.
Particulate matterFine solid or liquid particles such as dust, smoke, mist, fumes, or smog, found in air or emissions.
ParticulatesThe fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood…
PasserineBirds of the order Passeriformes, which includes perching birds and songbirds such as the jays, blackbirds, finches, warblers, and sparrows.
Peanut-body anthropomorphsObject or drawing having a human-like shape resembling that of a peanut. See also Anthropomorphic; Anthropomorphism
Pediment1. The triangular space forming the gable end of a roof above the horizontal cornice. 2. An ornamental gable, usually triangular, above a door or window.
Perennial yield (groundwater)The amount of groundwater that can be withdrawn from a groundwater basin over a period of time without exceeding the long-term recharge of the basin or…
Perennial/safe/sustainable yieldA specified rate of groundwater pumping that can be sustained for an indefinite period of time without impairing hydrogeologic and ecologic processes…
Perfluorocarbon (PFC)(PFC)Compounds consisting of carbon and fluorine. They do not deplete the stratospheric ozone but are very strong greenhouse gases with long lifetimes in the…
PermeabilityThe rate at which liquids pass through soil or other materials in a specified direction.
Permissible Exposure Limit (PPL)(PPL)The maximum amount or concentration of a chemical that a worker may be exposed to under OSHA regulations.
PermitAny permit other than a Notice to Proceed issued by the Landmarks Preservation Commission in accordance with the Landmarks Law: (a) "PMW shall mean Permit…
Permitted useThe forage allocated by, or under the guidance of, an applicable land use plan for livestock grazing in an allotment under a permit or lease; expressed in…
PermitteeAn individual who holds either a BLM grazing permit or grazing lease that authorizes grazing use of the public lands issued under authority of Section 3…
Personal Protective Equipment (PPE)(PPE)Clothing or devices worn to help isolate or shield a person from direct exposure to a hazardous material or situation.
Pesticide(PES-tih-side) Any substance that is used to kill insects and other pests.
PestleAn elongated, often cylindrical stone used to pulverize food products and other cultural products in a mortar. See also Mortar