Sampling points, rate

Before a source analysis program is undertaken, it is important to decide which information is really required. Sampling sites must be selected with care. Choice of the site can significantly affect accuracy and cost. Care must also be taken in the selection of sampling points at the site. Measurement usually involves the deterrnination of temperature, concentration, and characterization of the gas contaminants. It also requires the mass rates of emission of each contaminant, therefore concentration and volumetric flow data are required. 

Velocity and Volumetric Flow Rate The U.S. EPA has published Method 2 as a reference method for determining stack-gas velocity and volumetric flow rate. At several designated sampling points, which represent equal portions of the stack volume (areas in the stack), the velocity and temperature are measured with instrumentation shown in Fig. 25-27. 

Sampling points for analysis should be planned in order to give the whole record of analysis, e.g. in oil production from the well via processing facilities to the export facilities. Correlation with plant parameters such as temperatures, pressures, flow rates and, stream compositions can provide valuable records. Emphasis on chemical analysis should be incorporated in the design of process plant. Automatic analysis systems especially those using ion-sensitive electrodes with recording of data are recommended. 

The monitoring work to be performed (such as measuring the rate of dirt pickup), the frequency of testing, and the sampling points... 

DTso value. The sampling points should occur at regular, evenly spaced intervals with four to five sampling points prior to the T1/2 or DT50 value. If the data are heavily skewed towards the ends of a regression line, with few sampling points in between, erroneous estimates of the dissipation rate will occur. 

Spatial trends in LAS concentrations in marine and estuarine environments show clear relationships with the location of sampling points relative to point sources of wastewater discharges and a rapid rate of decrease is observed as one moves downstream from these. LAS tend to be degraded relatively rapidly in summer, whereas in winter a higher recalcitrance is observed. Sediments constitute the final sink of LAS that have not been degraded. 

The cross-correlation function of the concentrations of any compound, which are observable in a stream and which scatter like heavy metals, is a possible means of measuring transport rates in flowing systems. The maximum of the cross-correlation function indicates the time which is needed for transporting these compounds. For this purpose, the time series of heavy metal concentrations (Cd, Cr, Cu, Fe, and Zn) at two sampling points in the river 4.5 km apart taken at exactly the same time were cross-correlated (Tab. 6-2) [EINAX et al., 1994],... 

X, is the mole fraction of species i in the exhaust duct on a wet basis Ve is the actual volumetric flow rate at the sampling point (m3/s)... 

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