This new standard is intended to raise the reliability of sampling soils for determination of VOCs in the UK, by introducing methods that have been common use in countries such as Australia and the United States for over twenty years. It has been known for decades that the methods commonly used in the UK do not provide reliable results and can lead to loss of VOCs during sampling, and consequentially underestimation of potential risks to humans and other receptors.
The primary purpose of the draft standard is to provide risk assessors and managers with data that is as representative as possible of conditions in the field, in relation to volatile elements that might otherwise be lost in the sampling and analytical processes. In this context, it is the limits of detection of concentrations in the field that are of primary importance, rather than the limits of detection in the laboratory, although of course the latter can also be a major influence on the former.
The introduction of the new standard will have a significant impact on how companies carry out sampling for VOCs and require close cooperation between those carrying out field work and analytical laboratories.
BS 10175:2011 + A2:2017 states in Clause 8.3.2 that when collecting samples for determination of volatile compounds the sampling technique employed should minimise the loss of volatiles. It is noted that a methodology for the collection of soil samples to minimize loss of volatiles is given in BS ISO 18512: 2007 (this refers to methanol immersion). The new standard should make it easier to comply with this recommendation.
BS 10176 will be a standard specification which means that its requirements must be closely followed to claim compliance. It thus differs from other standards such as BS 10175 and the BS ISO 18400 series which provide guidance and permit, and indeed rely on, the user using their judgement when applying them.
The new standard specifies sampling procedures for application in the field.
Analytical procedures are outside of the scope of the standard and the standard makes clear that it is the responsibility of laboratories to adopt analytical procedures that will provide accurate analytical results for samples as presented to them.
Laboratories are required by BS 10176 to provide pre-prepared sample containers complying with the specification provided in the standard. These are to be used in the field in strict accordance with the procedures described in the standard. Samples must be transported to the analytical laboratory in strict accordance with the prescribed method.
Preparation of the New Standard
Approval for the production of the standard was given by BSI committee EH/4 in October 2017. The decision was “advertised” in an -mail dated 31 October 2017 widely distributed to the contaminated land community by Mike Smith, the Vice-Chair of EH/4. Inter alia, the e-mail invited applications to join the Drafting Panel. The Drafting Panel began its work in May 2018 under the leadership of Geraint Williams. The Draft for Public comment (DPC) was circulated in July 2019.
The draft standard was prepared drawing on existing published guidance and standards, and the personal experience of the members of the Drafting Panel and others. It was recognised and anticipated that there were points of detail that laboratories, consultants and others might query. However, none of the comments submitted via the regular BSI process, suggested that there was anything fundamentally wrong with the standard and all such comments were readily dealt with following the usual BSI comment review process.
As mentioned in the Introduction to the standard, the use of methanol immersion to preserve samples containing VOCs is already required or recommended in a number of British Standards. The procedures specified in the standard amplify those in BS EN ISO 15009, BS EN ISO 16558-1, BS ISO 18512 and BS EN ISO 22155 for the application of the methanol immersion method. The specification also introduces procedures for application of the sodium hydrogen sulfate (sodium bisulfate) solution immersion method.
The inclusion of methanol immersion in these existing standards is an indication that it is internationally recognised as a desirable methodology for certain purposes and as noted in the standard, there are also descriptions of the procedure in standards and guidance in the USA and other countries. In addition, a number of major UK consultancies already make use of such methods on a regular basis and there is reference to it being used in the UK at least twenty years ago. It is not a novel procedure and it was consequently considered reasonable to assume that at least some UK laboratories are already familiar with the process.
The use of immersion in sodium hydrogen sulfate solution is not so well known in the UK but it is a standard procedure in the USA and other countries.
The procedures described in the existing BS ISO standards are not very precise and so it was deemed desirable to produce a more detailed specification that would help to ensure consistency of application and would be amenable to auditing (by UKAS etc. or clients as part of QA/QC) if required. Although the specification is of necessity prescriptive, it does recognise the need for flexibility to permit application in a variety of situations. Detailed procedures can always be deviated from provided what has actually been undertaken and the reasons for the deviation are properly justified and recorded.
Feedback to BSI on experiences of application of the new standard will be important to its successful application and help to ensure that it can be updated as necessary in due course. Feedback and queries should be sent to the Jessy Mathew, the Manager of BSI committee EH/4 (firstname.lastname@example.org )
BS 10175:2011 + A2:2017 Investigation of potentially contaminated sites – Code of practice
BS EN ISO 15009 Gas chromatographic determination of the content of volatile aromatic hydrocarbons, naphthalene and volatile halogenated hydrocarbons – Purge-and-trap method with thermal desorption;
BS EN SO 16558-1 Risk–based petroleum hydrocarbons Determination of aliphatic and aromatic fractions of volatile petroleum hydrocarbons using gas chromatography (static headspace method);
BS ISO 18512 Soil quality – Guidance on long and short term storage of soil samples;
BS EN ISO 22155 Gas chromatographic determination of volatile aromatic and halogenated hydrocarbons and selected ethers – Static headspace method
Article provided by Mike Smith