Laboratory Terms

A glossary of science, chemistry, environmental and laboratory terms.

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National Ambient Air Quality Standards NAAQS: Standards established by EPA that apply for outdoor air throughout the country.
National Emissions Standards for Hazardous Air Pollutants NESHAPS: Emissions standards set by EPA for an air pollutant not covered by NAAQS that...
National Environmental Performance Partnership Agreements: System that allows states to assume greater responsibility for environmental ...
National Estuary Program: A program established under the Clean Water Act Amendments of 1987 to develop...
National Municipal Plan: A policy created in 1984 by EPA and the states in 1984 to bring all publicly ...
National Oil and Hazardous Substances Contingency Plan NOHSCP: The federal regulation that guides determination of the sites to be corrected...
National Pollutant Discharge Elimination System NPDES: A provision of the Clean Water Act which prohibits discharge of pollutants in...
National Priorities List NPL: EPA's list of the most serious uncontrolled or abandoned hazardous waste site...
National Response Center: The federal operations center that receives notifications of all releases of ...
National Response Team NRT: Representatives of 13 federal agencies that, as a team, coordinate federal re...
National Secondary Drinking Water Regulations: Commonly referred to as NSDWRs.
Navigable Waters: Traditionally, waters sufficiently deep and wide for navigation by all, or sp...
NDMA: NDMA stands for N-Nitrosodimethylamine (C2H6N2O) and is a semi-volatile organ...
Necrosis: Death of plant or animal cells or tissues. In plants, necrosis can discolor s...
Negotiations: After potentially responsible parties are identified for a site, EPA coordina...
Nematocide: A chemical agent which is destructive to nematodes.
Nephelometric: Method of of measuring turbidity in a water sample by passing light through t...
Netting: A concept in which all emissions sources in the same area that owned or contr...
Neutralization: Decreasing the acidity or alkalinity of a substance by adding alkaline or aci...
New Source: Any stationary source built or modified after publication of final or propose...
New Source Performance Standards NSPS: Uniform national EPA air emission and water effluent standards which limit th...
New Source Review NSR: A Clean Air Act requirement that State Implementation Plans must include a pe...
Nitrate: A compound containing nitrogen that can exist in the atmosphere or as a disso...
Nitric Oxide NO: A gas formed by combustion under high temperature and high pressure in an int...
Nitrification: The process whereby ammonia in wastewater is oxidized to nitrite and then to ...
Nitrilotriacetic Acid NTA: A compound now replacing phosphates in detergents.
Nitrite: 1. An intermediate in the process of nitrification. 2. Nitrous oxide salts us...
Nitrogen Dioxide NO2: The result of nitric oxide combining with oxygen in the atmosphere; major com...
Nitrogen Oxide NOx: The result of photochemical reactions of nitric oxide in ambient air; major c...
Nitrogenous Wastes: Animal or vegetable residues that contain significant amounts of nitrogen.
Nitrophenols: Synthetic organopesticides containing carbon, hydrogen, nitrogen, and oxygen.
No Further Remedial Action Planned: Determination made by EPA following a preliminary assessment that a site does...
No Observable Adverse Effect Level NOAEL: An exposure level at which there are no statistically or biologically signifi...
No Till: Planting crops without prior seedbed preparation, into an existing cover crop...
No-Observed-Effect-Level NOEL: Exposure level at which there are no statistically or biological significant ...
Noble Metal: Chemically inactive metal such as gold; does not corrode easily.
Noise: Product-level or product-volume changes occurring during a test that are not ...
Non-Aqueous Phase Liquid NAPL: Contaminants that remain undiluted as the original bulk liquid in the subsurf...
Non-Attainment Area: Area that does not meet one or more of the National Ambient Air Quality Stand...
Non-Binding Allocations of Responsibility NBAR: A process for EPA to propose a way for potentially responsible parties to all...
Non-Community Water System: A public water system that is not a community water system; e.g. the water su...
Non-Compliance Coal: Any coal that emits greater than 3.0 pounds of sulfur dioxide per million BTU...
Non-Contact Cooling Water: Water used for cooling which does not come into direct contact with any raw m...
Non-Conventional Pollutant: Any pollutant not statutorily listed or which is poorly understood by the sci...
Non-Degradation: An environmental policy which disallows any lowering of naturally occurring q...
Non-Ferrous Metals: Nonmagnetic metals such as aluminum, lead, and copper. Products made all or i...
Non-ionizing Electromagnetic Radiation: 1. Radiation that does not change the structure of atoms but does heat tissue...
Non-Methane Hydrocarbon NMHC: The sum of all hydrocarbon air pollutants except methane; significant precurs...
Non-Methane Organic Gases NMOG: The sum of all organic air pollutants. Excluding methane; they account for al...
Non-Point Sources: Diffuse pollution sources (i.e. without a single point of origin or not intro...
Non-potable: Water that is unsafe or unpalatable to drink because it contains pollutants, ...
Non-Road Emissions: Pollutants emitted by combustion engines on farm and construction equipment, ...
Non-Transient Non-Community Water System: A public water system that regularly serves at least 25 of the same non-resid...
Nondischarging Treatment Plant: A treatment plant that does not discharge treated wastewater into any stream ...
Nonfriable Asbestos-Containing Materials: Any material containing more than one percent asbestos (as determined by Pola...
Nonhazardous Industrial Waste: Industrial process waste in wastewater not considered municipal solid waste o...
Notice of Deficiency: An EPA request to a facility owner or operator requesting additional informat...
Notice of Intent to Cancel: Notification sent to registrants when EPA decides to cancel registration of a...
Notice of Intent to Deny: Notification by EPA of its preliminary intent to deny a permit application.
Notice of Intent to Suspend: Notification sent to a pesticide registrant when EPA decides to suspend produ...
Nuclear Reactors and Support Facilities: Uranium mills, commercial power reactors, fuel reprocessing plants, and urani...
Nuclear Winter: Prediction by some scientists that smoke and debris rising from massive fires...
Nuclide: An atom characterized by the number of protons, neturons, and energy in the n...
Nutrient: Any substance assimilated by living things that promotes growth. The term is ...
Nutrient Pollution: Contamination of water resources by excessive inputs of nutrients. In surface...

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