A nanometer is a unit of spatial measurement that is 10-9 meter, or one billionth of a meter. It is commonly used in nanotechnology, the building of extremely small machines.

Nansen bottle
An ocean-water sampling bottle with spring-loaded valves at both ends that are closed at an appropriate depth by a messenger device sent down the wire connecting the bottle to the surface.

An oil distillate. Naphta is an intermediate product between gasoline and kerosene. It is known as a light product because of the low molecular weight of the hydrocarbons making it up.

National Environmental Protection Agency (NEPA)
United States national institution for the protection of the environment. It establishes policy, sets goals, and provides means for carrying out its policy.

National Park
An area designated by the National Park Service as nationally significant, an appropriate addition to the park system best taken care of by National Park Service management rather than some other government agency or private organization. See Natural Reserve.

Natural depression
Concave hollow found on the Earth’s surface.

Natural element
Biotic or abiotic element in the environment, not directly being ascribed to human activities.

Natural gas
Geologically, natural gas is the gaseous phase of petroleum. For the most part it is made up of methane, while the remaining components (superior paraffinic hydrocarbons, such as ethane, propane, butane, pentane, etc.) are variable in quantity, depending on the fields. Natural gas is widely employed in household uses, in industry and in petrochemicals as feedstock. Feedstock: a raw material that can be converted to one ore more end-products(methanol or synthetic natural gas, for example).

Natural reserve
Area usually delimited and protected by specific provisions focused on the preservation of animal and plant species living therein.

Pelagic organisms that are free-swimming and so whose movements are independent of the tides, currents and waves. Such animals include fish, whales, squid, crabs and shrimps. The distribution of nekton is limited by temperature and nutrient supply and decreases with decreasing depth. Compare benthic (see), plankton (see).

Invertebrates with a cylindrical body, a conspicuous body cavity, and a complete digestive tract.

(see National Environmental Protection Agency).

Of, relating to, or inhabiting the shallow water, or nearshore marine zone extending from the low-tide level to a depth of 200 meters. The neritic zone is populated by benthic organisms because of the penetration of sunlight to these shallow depths.

Net-back pricing
A contractual arrangement in which the price of gas at the wellhead is based upon what it sells for at the burner tip less applicable transportation and distribution charges.

A reaction between acid and base which neutralizes both and results in the formation of water plus a salt.

(see Natural Gas Liquefied).

A compound that includes nitrogen and oxygen and contains more oxygen than a nitrite. Nitrate ions have the chemical formula NO3-.Examples: sodium nitrate NaNO3 and lead nitrate Pb(NO3)2.

Nitric acid
Known to alchemists as aqua fortis (strong water), was one of the first strong mineral acids to be discovered. It was obtained by distilling together saltpetre (potassium nitrate) and green vitriol (iron sulphate) or alum (potassium aluminium sulphate). Nitric acid could be used to separate silver from gold, as silver dissolves in the acid while gold does not. Today it is used in many chemical processes, particularly in the making of nitrate-based fertilisers.

Nitrogen oxides
Gas produced in the combustion processes due to the oxygenation of nitrogen contained in both the fuel and the combusting air. In the presence of other pollutants they can determine, as precursors, the formation of photochemical smog in the atmospheres of large urban areas. Like SO2 (see) they can lead to the phenomenon of acid rain.

1. Any sound not occurring in the natural environment, such as sounds emanating from aircraft, highways, industrial, commercial and residential sources. 2. An erratic, intermittent, or statistically random oscillation. It is measured in decibels.

Noise spectrum
The description of a sound wave’s resolution into its components of frequency and amplitude.

Non deformability
Attitude of body to not deforming.

Non hazardous waste
Waste resulting from an industrial or commercial activity but which is comparable to domestic waste and hazardous domestic waste. For example, cardboard, wood, packaging material, etc.

Non traditional energy
Alternative energy sources Energy sources different from those in widespread use at the moment (which are referred to as conventional). Alternative energy usually includes solar, wind, wave, tidal, hydroelectric and geothermal energy. Although they each have their own drawbacks, none of these energy sources produces significant air pollution, unlike conventional sources. Renewable energy Used to describe energy sources that are replenished by natural processes on a sufficiently rapid time-scale so that they can be used by humans more or less indefinitely, provided the quantity taken per unit of time is not too great. Examples are animal dung, ethanol (derived from plant sugars), wood, wind, falling water and sunlight.

Normal Cubic Meter (NCM)
Means the volume of dry gas which occupies a cubic meter measured at twenty five degrees Celsius (25o) at an absolute pressure equivalent to seven hundred sixty (760) mm Hg.

Not humic compounds
Organic compound whose structure has not undergone significant transformations over a period of time.

Nuclear energy
The energy liberated by a nuclear reaction (fission or fusion) or by radioactive decay.

Nuclear fission
A nuclear reaction in which a nucleus is split into fragments, usually two pieces of comparable mass, accompanied by a release of energy.

Nuclear fuel
Fissionable materials that have been enriched to such a composition that, when placed in a nuclear reactor, will support a self-sustaining fission chain reaction, producing heat in a controlled manner for process use.

Nuclear fuel cycle
The series of steps involved in supplying fuel for nuclear power reactors. It can include mining, milling, isotopic enrichment, fabrication of fuel elements, use in a reactor, chemical reprocessing to recover the fissionable material remaining in the spent fuel, reenrichment of the fuel material, refabrication into new fuel elements, and waste disposal.

Nuclear fusion
A nuclear process whereby several small nuclei are combined to make a larger one whose mass is slightly smaller than the sum of the original nuclei. The difference in mass is converted to energy by Einstein’s famous equivalence E=mc2. This is the source of the Sun’s energy and, ultimately, of (almost) all energy on Earth.

Nuclear reactor
A device in which a fission chain reaction can be initiated, maintained, and controlled. Its essential components are fissionable fuel, moderator, shielding, control rods, and coolant.

Nutrients are constituents required by organisms for maintenance and growth.

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