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NGM

Nested Grid Model generated every 12 hours by NCEP.

NHC

National Hurricane Center. The office of the National Weather Service in Miami that is responsible for tracking and forecasting tropical cyclones.

Nitrate

The nitrogen ion, NO3-, is derived from nitric acid and is an important source of nitrogen in fertilizers. Nitrate pollution of drinking water, shallow wells being particularly vulnerable, is of concern because infants are especially sensitive. A nitrate drinking water standard has been set under the Safe Drinking Water Act. An Environmental Protection Agency national survey of drinking water wells conducted from 1988 to 1990 indicated that 2.4% of rural domestic wells contained nitrate at or above the 10 mg/L standard. Higher rates of contamination have been found in areas of high vulnerability; for example, surveys along the upper Des Moines river indicate that 20 to 30% of wells exceed the standard.

Nitrogen

An element found in the air and in all plant and animal tissues. For many crops, nitrogen fertilizer is essential for economic yields. However, nitrogen can also be a pollutant when nitrogen compounds are mobilized in the environment (e.g., leach from fertilized or manured fields), are discharged from septic tanks or feedlots, volatilize to the air, or are emitted from combustion engines. As pollutants, nitrogen compounds can have adverse health effects (see nitrate and air pollution) and contribute to degradation of waters (see eutrophication).

Nitrogen cycle

Cyclic movement of nitrogen in different chemical forms from the environment, to organisms, and then back to the environment.

Nitrogen fixation

Conversion of atmospheric nitrogen gas into forms useful to plants and other organisms by lightning, bacteria, and blue-green algae; it is part of the nitrogen cycle.

Nitrogen Oxides (NOx)

Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced, for example, by the combustion of fossil fuels in vehicles and electric power plants. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), impair visibility, and have health consequences; they are considered pollutants.

Nitrous Oxide (N2O)

A powerful greenhouse gas with a global warming potential most recently evaluated at 310. Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

No net loss wetlands policy

An overall policy goal for wetland protection first adopted by the Bush Administration, and more recently by the Clinton Administration. The goal is to halt the decline in the overall number of wetland acres in the country. It refers only to acres and does not compare the functions and values of wetlands gained and lost. Also, this goal does not address the question of whether it is acceptable to destroy some wetlands if at least the same number of acres are created or restored at another site. Currently there are about 100 million wetland acres, compared to about 200 million when the country was first settled.

No Regrets Strategy

A strategy in response to the threat of climate change which argues that energy-saving measures should be undertaken immediately to help reduce global warming and climate change. Even if the threat of climate change is not as pronounced as we now fear, the supporters of this strategy say would not need to be any regrets because we would have benefited from saving the energy.

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