Experience

Environmental data usually are variable due to variation in true concentrations between different sampling locations and various measurement errors. INFOTOX follows the DQO process to limit the impacts that these variables may have on the outcome of the study. Furthermore, INFOTOX has extensive background experience and understanding of analytical science, laboratory methodologies, and limitations thereof.

Limitations in time and monetary resources are frequent and strong emphasis is placed on cost effectiveness. The sampling plan optimises the cost of sampling and analysis by limiting the number of samples required to adequately represent the true contaminant concentrations in the medium of interest.

Contaminated land is a sampling challenge. Water, soil, sediments and air may be of concern. Site-specific evaluation is critical to determine the most efficient approach to obtain representative samples. A number of approaches may be followed. Probability sampling is a specific method of random selection of sampling locations. Haphazard sampling may be applied only when contamination is homogeneously distributed. Judgement sampling relies on the competence and experience of the sampling specialist and samples are collected for their unique value, rather than for making inferences in a wider context. Sample composites for analysis save costs without compromising data quality. Special procedures exist for the location of hot spots of pollution of predetermined size and shape at a specified level of confidence.

Stockpile sampling often poses challenges in terms of obtaining representative samples. The stockpile is scooped from the bottom towards the top, or dug from the top using a mechanical loader-digger. The material is deposited on a clean hard surface for mixing and quartering. Large stockpiles are best sampled using the principle of random-number sampling. The stockpile is divided into practical areas from an aerial photograph or Google Earth, and each area is divided into square blocks and numbered non-randomly. The number of blocks and size are determined by professional judgement, based on prior knowledge of the homogeneity of the material. A random number generator is than used to select the locations where samples have to be collected.

Preparation of a composite sample for analysis involves standard methods of quartering, milling and subsample collection using a riffle splitter.

Industrial materials or wastes can be sampled from storage bins, or from conveyor belts over time for preparing a representative composite sample.

Sampling is of fundamental importance in the assessment of environmental contamination and it is essential that a high level of certainty be attached to the validity of the data that eventually inform management decisions.

INFOTOX has practical experience in the sampling of complex environmental media and offers expertise in the design and management of a wide spectrum of sampling programmes.