Emission flux measurement methods

Future studies of biogenic emissions should be designed to include sufficient data for uncertainty analyses of flux estimates. It is also important to conduct intercomparisons ot different sampling and measurement methods, as well as the methods used for estimating emissions, i.e. the dynamic chamber vs the micrometerological methods. Additional data are required to confirm emission estimates for those environments which have been characterized, and to extend the emission estimates to environments which have not been studied. Studies in ecosystems such as tropical rain forests should include surveys designed to identify potential terrestrial "hot spots of volatile sulfur emissions. 

Emissions of biogenic sulfur compounds to the atmosphere result from an imbalance between metabolic formation processes and biological or physicochemical consumption processes, determined on the spatial scale of the available methods for measuring emission fluxes. Variability in emissions... 

This area is still in flux. One major problem is that one needs to develop better measurement methods for formaldehyde at low levels, and one needs to have a better field measuring protocol for measuring meaningful formaldehyde levels that are dependent on age of the product, temperature, humidity, and ventilation rate as well as the activities of occupants. All these problems could be reduced, if formaldehyde emission would be effectively controlled at the source. 

Receptor models can also be used together with spatial distribution of measurements to estimate the spatial distribution of emission fluxes. The empirical orthogonal function (EOF) method is one of the most popular models for this. Henry et al. (1991) improved the EOF method by using wind direction in addition to spatially distributed concentration measurements as input. We describe this approach below. 

NO emissions did not exceed 2 ng Nm s and their measurement was only possible by chamber methods. The low NO emissions but high NjO emissions show that denitrification was the main source of NjO at this site. The discrepancies between the chamber and micrometeorological methods illustrated the need to define the flux-footprint of a micrometeorological measurement very carefully, and to use this information in the field to choose the locations in which chambers are placed. Without such an approach, the integration of results from chambers into estimates of field-scale emission remains an uncertain method. 

The emission methods of EEP detection are based on the ability of some metastable particles (N2(A ZJ, metastable atoms of rare gases) to knock electrons out of the surface of metals [59]. The present-day technique of measuring small currents allows one to record any small fluxes... 

There is also a standard test method for determination of major and minor elements in coal ash by inductively coupled plasma (ICP)-atomic emission spectrometry (ASTM D-6349). In the test method, the sample to be analyzed is ashed under standard conditions and ignited to constant weight. The ash is fused with a fluxing agent followed by dissolution of the melt in dilute acid solution. Alternatively, the ash is digested in a mixture of hydrofluoric, nitric, and hydrochloric acids. The solution is analyzed by (ICP)-atomic emission spectrometry for the elements. The basis of the method is the measurement of atomic emissions. Aqueous solutions of the samples are nebulized, and a portion of the aerosol that is produced is transported to the plasma torch, where excitation and emission occurs. Characteristic line emission spectra are produced by a radio-frequency inductively coupled plasma. A grating monochromator system is used to separate the emission lines, and the intensities of the lines are monitored by photomultiplier tube or photodiode array detection. The photocurrents from the detector... 

To complete the overview on sulfur emissions, a brief discussion of methods used to estimate emissions is appropriate. There are primarily two methods that may be used to measure earth-atmosphere flux of gases. In the dynamic chamber method, an open-bottom chamber is placed over a surface of interest such as mud, soil, or water, with or without vegetation, to capture the gases... 

Actually the concentrations of interesting radicals in water radiolysis are about 10 -10 M and it is necessary that they are measured using sensitive methods. The direct absorption spectroscopy is limited by the saturation and the linearity of the detector that must receive a high flux of light to detect a small amount of absorbed light. The emission spectroscopy is more convenient and more sensitive but... 

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