خيارات البحث
النتائج 31 - 40 من 101
The effects of artificial aeration on lake ecology
1972
Fast, Arlo W.
Monitoring mercury vapor near pollution sites
1972
Jepsen, Anders F. | Langan, Lee
Field and laboratory measurements were made to demonstrate that mercury vapor in the air near mercury-polluted water or sediment can be detected using an extremely sensitive detector, the Barringer Airborne Mercury Spectrometer. Areas were visited where the presence of mercury was known from fish, water, or sediment analyses; anomalous mercury levels ranging from 50 to more than 20,000 nanograms per cubic meter were detected. Anomalous concentrations of atomic mercury vapor in air may be classified as natural or man-made. Laboratory studies demonstrated that the mercury spectrometer is sensitive only to atomic mercury. By means of pyrolysis or combustion, organic compounds could be detected. To detect mercury pollution in water, pyrolysis appears necessary to convert combined mercury to the atomic state for measurement by rapid spectrophotometric techniques.
اظهر المزيد [+] اقل [-]Aquatic and wetland plants of southwestern United States النص الكامل
1972
Correll, Donovan Stewart,
Hypochlorite generator for treatment of combined sewer overflows
1972
Leitz, F. B. | Michalek, Steven A. | Greatorex, J. L.
The Economic impact of pollution control
1972
Filtration of municipal waste with a moving bed contactor
1972
Mixon, F. O.
Erosion and sediment pollution control
1972
Beasley, R. P. (Robert Patrick)
Trickling filter treatment of fruit processing waste waters
1972
Rose, Walter W. | Mercer, Walter A.
Role of bacteria in the nitrogen cycle in lakes
1972
McCoy, Elizabeth
Biological nitrification as contributing nitrite and nitrate to lakes and streams was explored by determining: nitrifiers, growth sites and activity; denitrifying bacteria numbers and their potential activity as opposing nitrification; field data on nitrite-nitrogen and nitrate-nitrogen in terms of nitrifier and denitrifier populations. Biological nitrification, both heterotrophic and autotrophic, was demonstrated. Even though opposing processes, nitrification and denitrification can coexist in close succession or in adjoining microhabitats. Field values for nitrate-nitrogen and nitrite-nitrogen vary considerably and must be viewed as net values at any given time. Thirteen species of fishes varied greatly in resistance to nitrite-nitrogen. Nitrite toxicity may influence fish species dominance in a eutrophic lake.
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