In recent years the presence of contaminants in bodies of water, both fresh and salt varieties, has become an issue of both public and governmental interest. In addition, air quality with respect to pollution from industrial or bellicose activities deeply affects the daily lives of most of the world's population. With the changing political situation in the world as well as concern over contamination from industrial and agricultural activity, a new intense interest has developed in monitoring water and air sources for pollutants and trace quantities of materials. As technology progresses, it has become increasingly important to know immediately the content of a body of water or air, thus necessitating the development of new analytical systems to give precise information on the presence and/or quantities of microbial and chemical contaminants.
To date, the available methods and devices have been concerned with “capturing” a sample for transportation to a laboratory for analysis and, in the case of trace quantities, concentration of the suspect species for that analysis. In addition, many of the available devices include sophisticated sensors and pumping apparatus that make the devices cumbersome as well as expensive to assemble and to maintain. Even though towed or tethered samplers are known in the art, their uses have been limited to physical characteristics and not the monitoring of chemical or biological species.
U.S. Pat. No. 3,537,316 to Stewart et al. shows a towed underwater sampler having an internal cavity that houses sensor circuits. In this device, water is permitted to flow through the analysis chamber so that temperature and pressure may be evaluated. However, the sensors here are measuring physical parameters and not the chemical or biological content of the water passing through the sensor cavity. In fact, there is no actual sample reading made by the instrument because only the desired parameters of temperature and pressure are immediately evaluated, and the actual sample is captured in a bottle for later analysis.
Another towed sensor system is disclosed in U.S. Pat. No. 4,713,967 to Overs et al. Again the sensors are only concerned with physical properties—temperature and water speed. The temperature and speed are then equated to the presence of fish bait, but no information is obtained about any compositional make-up of the environment or the nature of the fish bait itself.
Inner chambers in contaminant sensing devices for water analysis are described previously as well. One example is U.S. Pat. No. 6,272,938 to Baghel et al. Baghel et al. describes an inner chamber formed by a semi-permeable membrane in communication with an inner chamber containing a sensor that monitors contaminants in a tethered-style apparatus. Water diffuses through the membrane until a threshold is reached and then the diffusion is stopped. In this system, the quantity of contaminants is a function of diffusion time and, thus, is controlled by an unpredictable parameter.
U.S. Pat. No. 6,306,350 to Mereish et al. describes a portable water sampling device that captures the sample in a chamber that is then removed and sent to a lab for analysis. The concentration of the sample is determined as a function of time, because a timer is used to determine the sample collection period. A pump is also used to force the water being tested into the system and past the extraction membrane.
Similar devices that incorporate sampling chambers are described in U.S. Pat. No. 5,844,147 to Fiedler et al. and U.S. Pat. No. 5,167,802 to Sandstrom et al. Again, the samples are collected and sent to a remote lab for analysis.
In addition to aquatic environments, similar devices have been used in the atmosphere. Examples of these are U.S. Pat. No. 6,321,609 to Mengel et al. and U.S. Pat. No. 6,354,135 to McGee et al. Again, these systems include suction devices or pumps to facilitate the flow of effluent through the monitoring apparatus.
A system for immediate analysis of contaminants in situ is needed to overcome the disadvantages of the previously available systems. There is also a need for a system that incorporates reliability and sensitivity in performing the necessary analyses that is low-cost and easy to maintain. It is, therefore, to the provision of such an instrument that the instant invention is directed.