Advances in Environmental Instrumentation
Resource constraints have resulted in an undersampling of the environment—temporally, spatially, and with regard to chemical speciation. New developments in biotechnology, engineering, nanotechnology, and information technology provide promise for the development of monitoring networks that will overcome some of these deficits (Steinfeld et al. 2001). Advances in instrumentation that could contribute to the enhancement of the AQM system include the following:
Advances in solid-state tunable diodes that will enable the translation of powerful optical diagnostic techniques from the research laboratory to the field. Methods that provide capability of real-time measurements and remote sensing are differential absorption LIDAR (DIAL), correlation spectroscopy, and Fourier transform spectroscopy (Steinfeld et al. 2002). These laser diagnostics can be used to monitor fluxes (Shorter et al. 1996), in addition to mapping horizontal and vertical concentration distributions of pollutants (Tittel 1998; NASA 2003).
Reduction in the size of diagnostic and data acquisition systems that will permit the use of accurate and fast response instruments on mobile platforms (vehicular or airborne) capable of mapping concentration profiles for model testing and quantifying area sources and for identifying hot spots, leaks, and upset conditions. Miniaturization will also facilitate the development of personal exposure monitors of increased sophistication to monitor vital health-related statistics. Miniaturized near-real-time instruments are already available for many gaseous pollutants and are becoming available for particles through the use of field-deployable desorption gas chromatography and mass spectrometry techniques (Jeon et al., 2001) and aerosol time-of-flight mass spectrometers (Noble and Prather 1996; Bhave et al. 2002; Jayne et al. 2000).
The development of distributed networks of microsensors to monitor HAPs and biotoxins may become feasible as a result of recent developments of “laboratory-on-a-chip” technology initially driven by concerns with homeland security (Frye-Mason et al. 2001; Lindner 2001).
Perhaps the largest potential impact on the current approaches to monitoring will be the development of methods in biotechnology to rapidly screen for impacts of individual chemicals and mixtures. One example of the developments that will be important for the AQM system is that of DNA microarrays that show the potential of differentiating between exposures to different classes of toxicants and different toxicological outcomes (Bartosiewicz et al 2001).
Problems exist in the transitions of these technologies from research tools to commercial products that meet the needs of robustness, ease of use, cost, and equivalence to federal reference methods, problems that have only been partly alleviated by the Environmental Technology Verification Program. Use of instruments or procedures that do not satisfy a rigorous vetting process should be encouraged when valuable new insight is provided. For example, visual plume opacity readings have proved to be of great value, even though they do not provide the mass or composition of any specific pollutant, and cross-road sensors (Stedman et al. 1997; Jiminez et al. 2000) have proved their value in identifying high-emitting vehicles, even though their use for regulatory purposes is problematic. Some of the new methods might be introduced in the AQM system for specialized purposes, such as identifying hot spots, processing upset conditions for stationary sources, identifying breakdown in the emission control for mobile sources, and mapping spatially and temporally concentration distributions for ambient pollutants.