Plume Detection Research Articles

New semiconductor laser developed at Bell Labs

A new semiconductor laser design that differs in a fundamental way from diode lasers has been demonstrated by researchers at AT&T Bell Laboratories, Murray Hill, N.J. Called the quantum cascade laser, the device can be tailored, using conventional semiconductor materials and fabrication techniques, to emit light at any frequency in the mid-infrared to far-infrared range—a region of the electromagnetic spectrum not easily accessible with diode lasers. Moreover, the device produces an intrinsically narrower line width and is less temperature sensitive than are diode lasers. These characteristics combine to create potential interest in using the new laser for chemical sensing applications—for example,short-range detection (at a distance hundreds of meters) of plumes from industrial smokestacks and vapors from hazardous waste landfills, or very short-range monitoring (10 to 20 meters) of gas emissions, such as natural gas leaks. The laser can operate in the 3.3- to 4.2-µm and the 8- to to 13.3-µm ...

Sensitive detection of laser-ablation plumes in an optical build-up cavity

Cavity-enhanced detection is used to monitor the dynamics of minute vapor plumes produced by focusing a pulsed laser beam onto a surface. The time evolution of the various processes, namely vaporization, acoustic wave generation and photothermal effect range from nsec to msec.

Detection of Contaminant Plumes by Borehole Geophysical Logging

AbstractTwo borehole geophysical methods—electromagnetic induction and natural gamma radiation logs—were used to vertically delineate landfill leachate plumes in a glacial aquifer. Geophysical logs of monitoring wells near two land‐fills in a glacial aquifer in west‐central Vermont show that borehole geophysical methods can aid in interpretation of geologic logs and placement of monitoring well screens to sample landfill leachate plumes.Zones of high electrical conductance were delineated from the electromagnetic log in wells near two landfills. Some of these zones were found to correlate with silt and clay units on the basis of drilling and gamma logs. Monitoring wells were screened specifically in zones of high electrical conductivity that did not correlate to a silt or clay unit. Zones of high electrical conductivity that did not correlate to a silt or clay unit were caused by the presence of ground water with a high specific conductance, generally from 1000 to 2370 μS/cm (microsiemens per centimeter at 25 degrees Celsius). Ambient ground water in the study area has a specific conductance of approximately 200 to 400 μS/cm. Landfill leachate plumes were found to be approximately 5 to 20 feet thick and to be near the water table surface.

Helicopter plume detection by using an ultranarrow-band noncoherent laser Doppler velocimeter

An experimental demonstration of helicopter plume detection by using a range-resolved, narrow-bandwidth, noncoherent laser Doppler velocimeter is presented. The laser Doppler velocimeter detects incoming Doppler-shifted signal photons by using the sharp spectral transmission features in a Faraday magneto-optic atomic line filter.

Volatile processes in Triton's atmosphere and surface

The August, 1989 Voyager encounter with the Neptune system provided the fundamental information required to understand the volatile budget and transport processes on Neptune's large moon Triton. The discovery of nitrogen in Triton's atmosphere at a surface pressure of roughly 15–20 microbars, and surface temperature of 35–40K, combined with earlier ground-based spectra. strongly indicate that the atmosphere is supported by extensive deposits of surface nitrogen frosts, which are moved seasonally through the atmosphere in response to varying insolation. Likewise, Voyager and ground-based data support the notion that methane frost exists on the surface and is resupplying the atmosphere. The simplest model of global volatile transport, in which the albedo of the frost is constant, illustrates heuristically some interesting aspects of this system but does not reproduce the frost distribution seen by Voyager. Instead, models in which the nitrogen deposits have variable albedo, caused by grain size changes or contaminants, must be invoked. The grain growth properties and thermodynamics of pure nitrogen may also determine the radiating properties of the nitrogen frosts, which must be accounted for in the transport models. Finally, simple sublimation of nitrogen from the lit pole is not the only means of transport through the atmosphere: the detection of plumes above the surface may indicate the operation of moist convective processes which affect the transfer of both mass and energy from summer to winter regions.

Orientation of sampling grids for determining the extent of wavefront contamination

Traditionally, sampling grids for the detection of hazardous waste plumes are oriented perpendicularly to the direction of the wavefront of the contaminant. When rotated 45° to the direction of the wavefront, square lattices reduce the maximum waste plume that could go undetected and reduce the number of sampling stations. Improved site characterization and reduced sampling costs can both be achieved through this simple modification.

Real-time observation of dispersed hydrothermal plumes using nephelometry: examples from the Mid-Atlantic Ridge

As part of the 1984–1985 NOAA VENTS program on the Mid-Atlantic Ridge, nephelometry was used to provide real-time detection and tracking of dispersed hydrothermal plumes. At all nine 1984 study sites, hydrothermal activity was detected by in-situ, real-time nephelometer measurements and later confirmed by dissolved Mn and particulate Fe measurements. These same techniques were employed in a site-specific survey of the Trans-Atlantic Geotraverse (TAG) area in 1985 where large water-column anomalies in turbidity and in dissolved Mn helped lead to the discovery of high-temperature black smokers. The optical response of the nephelometer was to hydrothermally-derived particulate matter. Thus strong correlations existed between the nephelometer readings and total suspended matter ( r = 0.98, n = 34), and particulate Fe ( r = 0.88, n = 32). In addition, digital nephelometer data correlated well with dissolved Mn ( r = 0.88; n = 78) throughout a large concentration range (0.2–31.0 nmol/kg). These data provide good evidence for the utility of in-situ nephelometer measurements for locating and surveying plumes from hydrothermal vents. It also appears possible, within limits, to predict concentrations of in-situ total suspended matter, of particulate Fe and of dissolved Mn.

Assessing hazardous waste problems

Relatively inexpensive methods for delineating subsurface features near hazardous waste sites are needed. During the past 10 years the extensive development of remote-sensing geophysical equipment including field methods, analytical techniques, and associated computer processing, has greatly improved the ability to characterize hazardous waste sites. The use of seismic refraction and resistivity to investigate a subsurface geologic structure is illustrated. A second example is offered using ground-penetrating, electromagnetic induction, and magnetic surveys to locate and estimate the amount of buried wastes. Resistivity surveys have been conducted to map a landfill leachate plume. Electromagnetic induction has aided in the choice of locations of monitoring wells that were used to map another contaminant plume. While in the past most geophysical methods for plume detection have been applied to inorganic contaminants, such as chlorides and sulfates, in groundwater, attention is now being turned to the detection of organics. 8 figures, 1 table.

Detection of forest-fire smoke plumes by satellite imagery

In support of the Canadian research programmes for Long-Range Transport of Air Pollutants (LRTAP), the present study was undertaken to examine the feasibility of using satellite imagery to detect large-scale pollution episodes. Atmospheric Environment Service (AES) satellite imagery records were scrutinized in conjunction with meteorological and air quality data. The LRTAP from large forest fires more than 5000 km away was identified. Further evidence was obtained from analysis of digital data from NOAA satellites by employing a ‘false colour’ technique. Computer enhanced images suggested that a smoke plume was well-defined and separated from clouds when smoke crossed over a lake and ocean. It is suggested that many large forest fires with resulting intense smoke were due to atmospheric lightning. In particular, the area influenced by the widespread smoke, from large fires in northwestern Canada on 27–28 August 1981, exceeded the area covered by dust and smoke clouds in the low-level atmosphere from the Mount St Helens volcanic eruption on 18 May 1980.

Some aspects of the construction and use of atmospheric acoustic sounders

Acoustic sounder design and performance parameters are described. Various atmospheric features as recorded by the acoustic sounder, including thermal plumes, inversions and waves, are presented and their interpretation given. The use of the acoustic sounder to monitor the height of low level layer cloud and the depth of radiation fog is discussed as well as the detection and tracking of plumes of methane gas.

Atmospheric Electrical Plume Detection: Theory and Field Measurements

Abstract Airborne atmospheric electrical measurements may be useful in studies of air pollution, turbulence, and aerosol distributions. A short summary of the electrical nature and behavior of the atmosphere is given relative to the atmospheric electrical detection of aerosol plumes. An example of the efficacy of this approach is illustrated through an experiment in which an aircraft equipped with atmospheric electrical instruments flew side by side with another aircraft equipped to measure particles and gases while tracking a plume out to 90 km. The approach described would be equally viable for the detection of exhaust tracks from ships and submarines and for detecting and monitoring radioactive plumes.