Monitor particle emissions

A more convenient means of media comparison, whilst still retaining some of the above practical elements, is described by Anand et al. In this procedure, a single sleeve of smaller size is mounted on a plastic cage and located in a clear Perspex cylindrical enclosure. A quantity of dust is added and this is then transformed into a cloud by means of compressed air injected at the base of the unit. The dust-laden air is drawn onto the surface of the sleeve and the subsequent pressure differential monitored by computer. Any particle emissions through the fabric are captured by an ultrafilter and measured gravimetricaUy. Once again, the gas velocity, cleaning frequency, pulse pressure, and pulse duration can be adjusted and, by virtue of the clear Perspex cylinder, the effects of these can be visually observed. 

Eailure to monitor the workplace or environment for fugitive particle emissions and... 

Source sampling of particulates requites isokinetic removal of a composite sample from the stack or vent effluent to determine representative emission rates. Samples are coUected either extractively or using an in-stack filter EPA Method 5 is representative of extractive sampling, EPA Method 17 of in-stack filtration. Other means of source sampling have been used, but they have been largely supplanted by EPA methods. Continuous in-stack monitors of opacity utilize attenuation of radiation across the effluent. Opacity measurements are affected by the particle size, shape, size distribution, refractive index, and the wavelength of the radiation (25,26). 

This technique is invasive however, the particle can be designed to be neutrally buoyant so that it well represents the flow of the phase of interest. An array of detectors is positioned around the reactor vessel. Calibration must be performed by positioning the particle in the vessel at a number of known locations and recording each of the detector counts. During actual measurements, the y-ray emissions from the particle are monitored over many hours as it moves freely in the system maintained at steady state. Least-squares regression methods can be applied to evaluate the temporal position of the particle and thus velocity field [13, 14]. This technique offers modest spatial resolutions of 2-5 mm and sampling frequencies up to 25 Hz. 

Fig. 8. Dependence of (A) corrected diffusion coefficient (D), (B) steady-state fluorescence intensity, and (C) corrected number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The diffusion coefficient and number of particles data shown here are corrected for the effect of viscosity and refractive indices of the urea solutions as described in text. For steady-state fluorescence data the protein was excited at 488 nm using a PTI Alphascan fluorometer (Photon Technology International, South Brunswick, New Jersey). Emission spectra at different urea concentrations were recorded between 500 and 600 nm. A baseline control containing only buffer was subtracted from each spectrum. The area of the corrected spectrum was then plotted against denaturant concentrations to obtain the unfolding transition of the protein. Urea data monitored by steady-state fluorescence were fitted to a simple two-state model. Other experimental conditions are the same as in Figure 6.

The techniques of u.SR and p-LCR are based on the fact that parity is violated in weak interactions. Consequently, when a positive muon is created from stationary pion decay its spin is directed opposite to its momentum. This makes it possible to form a beam of low energy (4 MeV) positive muons with nearly 100% spin polarization at high intensity particle accelerators such as TRIUMF in Canada, the PSI in Switzerland, LAMPF and BNL in the USA, KEK in Japan, and RAL in England. Furthermore the direction of position emission from muon decay is positively correlated with the muon spin polarization direction at the time of decay. This allows the time evolution of the muon spin polarization vector in a sample to be monitored with a sensitivity unparalleled in conventional magnetic resonance. For example, only about 101 7 muon decay events are necessary to obtain a reasonable signal. Another important point is that //.SR is conventionally done such that only one muon is in the sample at a time, and for p,LCR, even with the highest available incident muon rates, the 2.2 fis mean lifetime of the muon implies that only a few muons are present at a given time. Consequently, muonium centers are inherently isolated from one another. 

Excerpt 4E is taken from an article in Chemical Research in Toxicology and involves the toxicity of fine particulate matter, airborne particles with effective diameters <2.5 pm (also known as PM2 5). The fine particulate was collected using a PM2 5 monitor. Ambient air is pulled through the monitor, diverting the larger particles (>2.5 pm) and capturing only the smaller ones onto a filter. Such fine particles arise from a number of sources including industrial emissions, vehicle exhaust, and forest fires and may lead to asthma, bronchitis, and possibly cancer. 

EPA has collected data on the emission of PM2 5 particulates since 1992 and on air quality for the pollutant since 1999. These data indicate that the direct emission of PM2 5 particles has decreased about 10 percent over the monitoring period, from about 2.75 million short tons (2.5 million metric tons) in 1992 to about 2.4 million short tons (2.2 million metric tons) in 2001. Over the short span of monitoring, PM2 5 concentration decreased by about 5 percent from about 14 pg/m in 1999 to about 13.3 pg/m in 2001. 

As an example of typical experimental data, Fig. 10.32 is a GC-MS selected ion monitoring (SIM) profile (m/z 247) for the nitrofluoranthenes and nitropy-renes in an extract of ambient particles collected in southern California (Arey et al., 1988b). The 1-nitropyrene (1-NP) and 3-nitrofluoranthene (3-NF) presumably are from diesel emissions (Tables 10.33 and 10.34), but the dominance of 2-nitrofluoranthene and 2-nitropyrene reflects a second major source. 

---