Transects sampling

In either of the above-mentioned cases, two types of information need to be obtained before sampling and analysis are performed. First, information about the background level of the component of interest is needed. It might be assumed that transect samples can be taken in the area starting from one place that is contamination free and continuing across the contaminated area to another point where there is no contamination. This would delineate the area of interest or concern. 

Only the area around the source of contamination need be sampled. As a first step, transect sampling, at random points along dashed lines in Figure 7.5 (also see Figure 7.2), can be done to find the general extent of the contamination, that is, from a point where background levels of contamination are present on both sides of the contamination. 

Transect sampling provides information on the extent of contamination, the intensity of contamination (level), and the area that exceeds the actionable levels2 such that remediation is required. The solid circular lines in Figure 7.5 indicate various levels of contaminant around the leak. 

After transect sampling, a more detailed sampling of the contaminated area can be undertaken. A first approach would be to take random samples from the whole area. This could be done by randomly picking GPS coordinates that occur in the field and randomly sampling these coordinates. Although... 

Figure 7.7. Transect sampling for a nonpoint source analyte. 

Transect sampling for nonpoint sources is done the same way and with the same purpose as it is in point source sampling. Figure 7.7 shows a transect across an area to be sampled. Different markers indicate that different sampling will be accomplished at these sites. These would also be sites for depth sampling if it is called for. 

Figure 1. Map of St. Mary s City, Maryland area (adapted with permission from Reference 13 copyright 1989, Maryland Geological Survey). Inset shows elevation changes along Mattapan Road, up the St. Mary s Hill, with transect sampling sites marked by boxes. Triangles on larger map indicate most recent sampling locations. Sample sites A-F were examined by Armitage et al. (14).

Figure 9.16. Comparison of the BIX and HIXem for an estuarine transect sampled on three dates. BIX and HIXem measurements were nsed to infer regions of different organic matter character, identified by the vertical hues. These differences were attributed to fresh water from the river mixing with saline marine water. (From Hngnet et al., 2009.)...

Manheim FX, Pauli, CK (1981) Patterns of ground water salinity changes in a deep continental-oceanic transect off the southeastern Atlantic coast of the U.S.A. J Hydrol 54 95-105 Martin P, Akber RA (1999) Radium isotopes as indicators of adsorption-desorption interactions and barite formation in groundwater. J Environ Radioact 46 271-286 McCarthy J, Shevenell L (1998) Obtaining representative ground water samples in a fractured and karstic formation. Ground Water 36 251-260... 

Fig. 1. The Honerat kimberlite and the Unknown Site are located in western Quebec, Canada. The labeled points represent sample collection sites along transects at Honerat and Unknown.

Methods and Results At 15 sites along a 1000 m transect across the Talbot deposit, soil profiles were sampled in 10 cm depth intervals, up to 50 cm. The <250 pm (silt + clay) and <2pm (clay) fractions of the soil samples were analysed using an aqua regia digestion and ICP-MS measurement of 53 elements. 

LA-ICP-MS was used to determine the compositional variation in the nodules along transects from the central rock nucleus toward the outside edge. Analytical transects were conducted across nodules from LG1 and LG2 (Fig. 4). On each sample, one transect followed the shortest axis (from the nucleus to the top of the nodule) and a second followed the longest axis (from the nucleus to the... 

Seventy-three soil samples from 0-to-5 cm depth along the N-S transect collected by ultraclean methods were analyzed for selected organochlorine pesticides. Only three of the samples had pesticide concentrations greater than the detection limit of the analytical method. 

Lessons learned from the field sampling for the transects and recognized in the geochemical data lead to the following ... 

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