scope:

Introduction

VDI guideline 3865 covers methods of analysing soil gas which enable rapid, simple, inexpensive and comprehensive estimation of pollution of ground water and/or soil caused, for example, by volatile organic compounds.

Part 1 [1] provides instructions on measurement planning and measurement strategy for soil gas measurements which are intended to give a rapid preliminary overview of the type, the main areas and the extent of contamination. Part 2 [2] describes various methods of soil gas sampling. Parts 3 [3] and 4 specify analytical methods for determining the organic compounds. The two parts covering soil gas analytical procedures can only be employed in combination with VDI guideline 3865 Part 2 on sampling. Section 3 of Part 4 (analytical determination) is linked directly to the respective sampling variants described in Part 2 (Variants 4 and 5).

This Part 4 covers the analytical determination of volatile organic compounds in soil gas by direct analysis of the soil gas samples. The analysis of the soil gas samples can be performed either at the sampling site (on-site analysis) or in the laboratory.

The methods for analysis of soil gas described in VDI guideline 3865 serve for detecting contamination of soil and ground water, and although they can be used to determine the order of magnitude of pollution, they cannot be used to determine exact pollutant concentrations for soil and ground water. More detailed studies must be carried out to clarify questions with respect to remediation and suitability for remediation (see [2]). Soil gas measurements are thus sitespecific and provide only relative measurement results. To achieve significant results, it will be necessary to perform a greater number of measurements distributed over a three-dimensional grid matched to the specific problem. Individual measurements are not suitable to assess contamination. The significance of the analysis increases with the number of measurement points. A defined correlation between soil gas contamination and total contamination of soil or of ground water is not necessarily given. In each specific case the results will need to be evaluated by an expert.

Since the concentration of volatile organic substances in soil gas is a function of many different factors, a rigid application of guide values to assess the hazard potential is not appropriate.

The comparison of different sample pretreatment methods using calibration gas mixtures is published in [4].