Sampling - Field Sampling: Principles and Practices in Environmental Analysis - page 119

type of contaminant in the sample and its reactivity with sampler materials. For sampling
involving organic contaminants many different materials will be acceptable as long as
they do not react with the sample. When sampling is for metal contaminant the metal
composition of the sampler is of primary concern. In some situations a number of
different samplers of different composition will be required.
There is a great variety of plastics with different contaminant compatibilities. One
widely used plastic is Teflon and Teflon-coated samplers. This plastic is resistant to
almost all chemicals and has a nonstick surface. As with all plastics, however, it is not
good for situations in which the sampler must cut through abrasive material. Also, if the
sampler is Teflon-coated, it is imperative that care be taken to assure that there are no
holes or worn spots in the Teflon, which might lead to contamination or cross-
contamination of sample.
All plastic and plastic-coated samplers are best suited to air and water rather than soil
sampling. Soil is abrasive and can rapidly wear away plastic coatings, which can also
develop gouges and cracks, exposing the underlying material to the sample. Also, cracks
can become filled with sample material and thus cross-contaminate samples.
In addition to plastic, samplers are also made of various metals, including brass, iron,
steel, and stainless steel alloys. Metal samplers are common and robust; however, they
can result in metal contamination of samples. This is particularly a problem when the
contamination of interest is a metal ion, metal, or heavy metal. This can be even more of
a problem when the material being sampled is very acid. Keep these considerations in
mind when choosing a sampler and sampler material.
5.6.2. Sampler Types
There are a large number of samplers designed for different soil types and depths of
sampling. Perhaps the simplest is a metal tube or core type 46 to 50 cm (18 to 20 in.)
long, usually with a section cut out of one side of the tube. (See Figure 5.5.) A piece of
tubing is fixed on the top, making a T, and the mouth at the bottom is shaped to make it
easy to insert into soil. The sampler is inserted, usually using hand or foot pressure, into
soil at the correct site and then withdrawn with the soil sample. The side opening is used
for removing the sample. This sampler is a most useful in fine-textured, moist soils.
When the soil and moisture conditions are favorable, it is only limited in how deep it can
sample by how deeply it can be pushed into the soil using hand or foot pressure.
For deeper sampling a larger, more robust sampler of the same basic design can be
inserted into soil using a manual or powered hammer. For even greater depths, a similar
core-type sampler can be attached to the back of a pickup truck equipped with a hydraulic
or mechanical system for insertion into soil. (See Figure 5.6.) The hydraulic press inserts
a length of pipe into the soil; when removed, the core is pushed out, again using the
hydraulic or mechanical system. In this way, cores of various depths can be easily
obtained. This sampler can be used to quickly and easily sample large areas. (See
Appendix B for sources of samplers.)
Another type of sampler is a rod about 46 to 50 cm long on the end of which is
attached an auger, which is like a wood drill bit. (These are shown in Chapter 3, Figure
3.6.) These samplers are most commonly used and useful for obtaining samples in soil