ABSTRACT
In general, people are familiar with sampling, such as food sampling, sampling for cosmetics, or other types of sampling. Although the purpose of these samplings is to ensure that the quality is acceptable, it is still different from soil sampling. Soil sampling essentially consists of aspects related to site selection, selection of tools for sampling, protocol collection, sample collection, sample handling, sample storage, sample preparation, and analysis and interpretation of the data. The quality of sample collection is as important as the quality of analysis or the analytical procedure. When a soil sample of appropriate size and quality that is representative of the study site is provided to a laboratory for analysis, the results can be expected to be of good quality. It is also important to set aside some clear-cut objectives and criteria of success before collecting soil samples. This in turn may indicate the quality of data required to achieve certain benchmarks. According to the USEPA (2002), data quality objectives must address precision, accuracy, representativeness, completeness, comparability, and level of detection. Precision is important when the change in a property of the soil is very low. Accuracy, although used as a synonym for precision, can be controlled by the laboratory. Representativeness refers to the degree to which the samples collected from a given area truly represent the property or variability of the property in question. Completeness and comparability are important for making valid comparisons over space and time between the data collected from two different sites. In spite of these guidelines that a researcher should follow to collect good-quality datasets, one must always remember that soil is highly variable, and various processes occurring in the soil or at the soilatmosphere interface (soil surface) are complex and dynamic in nature and may necessitate employing different sampling strategies for different objectives. In addition to the data quality objectives discussed here, before collecting soil samples from a study site, attempts should be made to gather as much background information as available with different agencies and in the published literature.
