Grid systems, sampling

This chapter provides guidance on several basic aspects of soil sampling, such as systematic sampling on a grid system, sample compositing, and sampling for specific chemical parameters, such as PCBs and VOCs. 

Increments must be spaced systematically. Stationary sampling employs a grid system, which may be a simple left front-middle center-right rear grid for samples from a railroad car or a surveyed grid system to take samples from a storage pile. 

There are a number of options for sampling on a grid system. For example, when justified by the project DQOs, instead of collecting samples in the grid nodules, we may collect one random sample within the boundaries of each grid unit or collect several samples from each grid unit and composite them for analysis. 

Overlay a square grid system with a grid unit length of 1.5 meter (m) over the entire area to be sampled. 

Sampling. A sample was drawn at random from a list of randomly combined x and y coordinates that indicated location points for pseudo-morphic evidence. The location point is defined as the field of vision at 10 X magnification that allowed attribute data occurring in the field to be observed. The spearpoint was placed upon a special microscope stage that had a centimeter grid system. The x axis was identified by letters A-Y, and the y axis was identified by numbers 1-10. These combinations of coordinates led to the spatial location points or subunits of the site. Photomicrography was used to record the mineralized fabric attributes at 101 location points. 

The most commonly used grid systems are rectangular and triangular. The first critical decision in developing a grid system is to decide upon the desired sample number. As a guide, the sample number n can be determined from the following equation ... 

FIGURE 3 Diagram of a sample grid system typically used in performing general circulation experiments. 

Figure Bl.23.5. Schematic illustration of tlie TOE-SARS spectrometer system. A = ion gun, B = Wien filter, C = Einzel lens, D = pulsing plates, E = pulsing aperture, E = deflector plates, G = sample, PI = electron multiplier detector with energy prefilter grid and I = electrostatic deflector.

The systematic, or grid, search is only possible for small molecules. For larger systems tlrere are methods which can be used for perturbing a geometry from a local minimum to another minimum. Some commonly used methods for conformational sampling are ... 

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