Article Laboratories

On Stony Ground

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Tags: analysis laboratories

How standardised is MCerts analysis in stony samples? 

Despite articles such as that by Mark Perrin (Ground Engineering, April 2007), many engineers, consultants and regulators still appear to be largely ignorant of the differences in soil sample preparation methods between laboratories and the effect this can have on the results produced.  Many assume that the MCerts accreditation commonly required by Local Authorities and the Environment Agency has ‘standardised’ laboratory analysis such that the reported contaminant concentration will be that of the soil tested without any significant variance.  Unfortunately, whilst the MCerts scheme focuses on quality procedures to ensure repeatability within an individual laboratory, it does not standardise the test method itself, and thus variations between laboratories remain.

The MCerts scheme requires comparison trials between labs to be carried out on a standard homogeneous matrix, which generally produces a high degree of comparability between laboratories; unfortunately most soils that are sent for analysis tend not to be like this homogeneous matrix.  Typically most analysis is carried out on samples of near surface made ground which is by its very nature largely heterogeneous, and usually with a high stone content.  As an extract can not be produced from the stones, sample preparation including either grinding of the stones to a fine powder or excluding them such that the sub-sampling uncertainty can be reduced or eliminated.  However, the methods adopted to achieve this are by no means standardised between laboratories.

How do laboratory methods vary?
All commercial laboratories with MCerts accreditation for PAHs and toxic metals were asked about their sample preparation methods. Responses were received from 18 of these laboratories with 17 being accredited for metals and 17 for PAH.  A surprising number of laboratory managers were unsure of the sample preparation method and had to check their procedures before being able to reply; however the responses received are summarised below;

Metals

No of labs using this method

Percent of labs that responded
Dry and crush to less than 0.5mm

8

47%
Remove stones greater than 2mm diameter

2

12%
Remove Stones Greater than 10mm diameter

6

35%
Remove all ‘inert’ stones

1

6%

 

For metals the main difference appears to be whether the stones are removed or are crushed and when removed what size stones are removed. However, with PAH a greater range of sample preparation methods were apparent;

 

PAH

No of labs using this method

Percent of labs that responded
Test as received sample but avoiding stones

8

47%
Dry and crush to less than 0.5mm

4

24%
Remove Stones Greater than 2mm diameter

2

12%
Remove Stones Greater than 4.75mm diameter

1

6%
Remove Stones Greater than 10mm diameter

2

12%

 

Of those labs that dried the samples, two did so at 28 oC, five at 30 oC, one at 35 oC and one at 37 oC.  Variation in the extraction solvent was also apparent as set out below.

 

Extraction solvent for PAH analysis

No of labs using this method

Percent of labs that responded
Dichloromethane (DCM)

13

76%
DCM & Hexane

1

6%
Hexane:Acetone

2

12%
Pentane

1

6%

 

This variation has been further complicated recently, as during the recent recession, the partial shut down of the car industry reduced the demand for foam rubber, a bi-product of the production of which is DCM.  Therefore the price of DCM rose significantly and several laboratories switched from using pure DCM to a mix of DCM and hexane or acetone or even hexane:acetone:triethylamine.  Once the car industry recovered and the price of DCM fell these laboratories reverted back to using pure DCM.

What are the effects of variation in preparation methods?

In a soil where the contaminant concentration is distributed evenly between the matrix and the stone content, removing or crushing the stones would clearly have no effect on analysis results.  However, where the metallic contaminants are expected to be concentrated in the coarser particles, as in a slag or clinker, crushing of the stones will produce a higher contaminant concentration than would be produced in a laboratory that removes the stones.  Similarly, as the bulk of the made ground which is present in garden areas that have been used for a considerable period will have been subject to bonfires and the active digging in of ash, part burnt fragments of coal or timber are common.  Such relatively coarse fragments could be expected to be a source of PAH (including benzo(a)pyrene) and therefore a sample which was crushed prior to analysis could be expected to yield a higher concentration than one from which the larger particles had been removed. Conversely, where the burning of painted wood has resulted in elevated lead concentrations in a fine ash, or where soot has been dug into the soil, the presence of natural stones in the sample will act to ‘dilute’ the measured concentration if they are crushed during the analysis rather than removed..  However where the weight of the stones removed is back-calculated into the reported result this effect should be eliminated.

In addition to the effect of stone content, where a sample is dried the variation in drying time and temperature will surely have an effect upon the more volatile compounds such as naphthalene which could be lost to some extent, especially where the sample is dried overnight at 37oC.  The reported naphthalene concentration of a dried and crushed sample would thus be expected to be lower than that of a sample tested in the as received condition.

The variation in extraction efficiency of the different solvents and solvent mixes would also be expected to induce variability.

So which is the right method?
Unfortunately, there is no right or wrong method of analysis, as the applicability of each method is dependent on the use to which the results are to be put, which is beyond the control of the laboratory.  The onus therefore ,has to be placed upon the consultant scheduling the testing and interpreting the results to use an appropriate method.

For example; waste classification is based upon a hazard assessment and the analysis is required to be representative of the whole load being disposed of, and thus a dried and crushed approach may be applicable.  However, for human health a risk based assessment is adopted and thus consideration needs to be given to the likely exposure pathways.

For Benzo(a)Pyrene some 56% of the total exposure for the residential land use arises from the ingestion of soil and indoor dust.  As soil Pica has not been included as an exposure route in the CLEA model, the bulk of the ingestion of soil will be from accidental ingestion from hand to mouth contact and as such larger particles are unlikely to be involved.  Similarly, dermal contact, which amounts to 36% of the total exposure for the residential land use is unlikely to be significantly affected by the larger particles which will have a far lower surface area to volume ratio.  Therefore, for a Benzo(a)Pyrene risk assessment, an analysis of the fine particles following sieving and the exclusion of the stone content from the calculated results would appear to be far more appropriate.  This would also be the case with the majority of the PAHs and toxic metals.

Conclusions
Engineers and consultants scheduling laboratory analyses need to be aware of the sample preparation method that is to be adopted by the laboratory and the effect that this will have on the results for the specific soil which is being tested.  It would also be helpful if laboratories published a basic summary of the sample preparation method along with the results to aid those interpreting the results and to assist where comparisons between different sets of data on the same site are being carried out, be it by different laboratories or by the same laboratory over a prolonged period.  Furthermore, when the chemical analyses indicate that the soil in a garden contains contaminant concentrations close to or a little in excess of the adopted threshold values, it would be worth considering the effect of the sample preparation method and whether retesting a sieved sample may produce a more appropriate concentration to compare with the adopted threshold, considering the assumed critical exposure pathways.

Mike Plimmer
GEA Associates

 

Article Contaminated Land Laboratories

UKWIR – GUIDANCE FOR THE SELECTION OF WATER SUPPLY PIPES TO BE USED IN BROWNFIELD SITES

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Tags: analysis brownfield contaminated investigation laboratories

Peter Boyd, AECOM Limited and Neil Parry, Geotechnical Engineering Limited

The UK Water Industry Research (UKWIR) has produced this document to replace the heavily criticised 2002 WRAS guidance on water supply pipe materials for contaminated land. Unfortunately there remain several similar problems with the new document. It has been produced by UKWIR with the footnote “Promoting Collaborative Research” but there does not appear to have been any collaboration or consultation with practitioners in the industry. As a result the document fails to reflect commonly accepted industry practice and terminology.

The basis of the document is highly conservative, for example making reference to identifying whether “any chemical may have ever been on a site” and that “samples should be collected at a frequency and depth that will identify any contamination”.  Although it rightly advocates a risk based approach to sampling and assessment many of the recommendations ignore this premise and current guidance, with the end result likely to be overdesign and significantly increased costs for end users.

The document was recently revised, where some of the initial errors were corrected, unfortunately several errors remain and the opportunity to gain widespread acceptance was missed.

The responsibility for the selection of supply pipes is confused between the Developer, Self Lay Organisation (SLO) and Designer.  The responsibility for the production of the crucial Site Assessment Report (SAR) is not clear between the “Developer” or the “Designer” without considering whether they have the necessary contaminated land expertise.  Guidance such as the new Eurocodes define competence roles and from an industry perspective it’s yet another missed opportunity to give some further recognition to the SiLC qualification. It seems to be aimed at the layman but also advocates a very wide ranging and unusual range of laboratory implying the user has a detailed knowledge of soil sampling, preservation and laboratory testing. It is also unfortunate that 30 years after the first edition of BS5930 the document blurs the distinction between site investigation and ground investigation.

Desk Study
The document provides some good general guidance on establishing previous site use and the potential for contamination but insufficient information or reference is provided for a general user to adequately complete this.  It suggests that the findings should be summarised on a map to show current and historic land use but show a level of detail at a scale which would not be possible in most practical instances. implying that the authors have not actually performed this exercise with real data or thought about the preparation of a robust conceptual model, which is the basis for most contaminated land assessment.

The document suggests that the Local Authority may request an SAR as part of the planning process.  There is no recognition of the fact that such an assessment could and perhaps should be incorporated into the routine pre-development desk study, intrusive ground investigation and interpretative reporting process.

Investigation
When looking at investigation the application of photoionization detector (PID) screening is meaningless without further guidance. The “suitable survey pattern” is not defined and ignores the shortcomings of PID readings. The extent of suggested PID testing could also be onerous in most circumstance.

The soil sampling section refers to an unspecified “suitable survey pattern” which is easily confused with the PID screening.  Although it recommends the use of BS10175 for more detailed information on the design of a sampling plan no specific information on sampling for proposed services is included. It makes reference to taking “a spadeful” and the use of a “plastic bag” for samples which may be inappropriate and ignore the complexities of sampling.  Investigation and sampling are assumed to be undertaken via trial pits (likely to be machine dug to achieve the recommended depths) which would be difficult in an urban situation where numerous existing services are present and may not present the best method for obtaining the best samples, particularly for groundwater.  It suggests that if groundwater is present within 1m (or 2m in summer) of the base of the intended trench then a water sample should be taken from “a suitably completed narrow borehole” but establishing groundwater depth may be difficult.

Chemical Analysis
One of the most onerous parts of the recommendations is the imposition of a mandatory analytical suite to be undertaken on all samples.  Despite the fact that a desk study and ground investigation has been undertaken, including PID screening for VOCs, it appears that there is a limited choice for the user of the document in respect of what testing is required. The suite is far from routine with several determinands not generally carried out by any of the commercial laboratories in the UK on soils. To cover the lists as provided would probably cost in excess of £300 per sample.  Notably only organic contaminants are considered with the absence of inorganics such as arsenic.

Confusion extends to the proposed testing suites. The extended VOC suite (by GCMS) contains many non VOCs such as Benzo(a)pyrene and propylene glycol, explosives such as nitroglycerine and nitrotoluene (which are analysed by HPLC), Nitrohydrochloric acid (Aqua Regia a mixture of HCL and nitric acid which again cannot be analysed as a VOC) and Naphtha which is petroleum terminology for an ill defined distillate. There are misspelled chemicals such as “Mesityl” oxide and duplicated compounds such as methyl chloroform (which is 1,1,1 TCE) and Monochlorobenzene which is Chlorobenzene.

Other suites contain similar errors. Petroleum ether is incorrectly listed under ethers. Under mineral oil the document contains a turpenoid, a plasticiser, a flavour, a fatty acid and fuming sulphuric acid with no mention of mineral oil C5-C10, C11-C20 and C21-C40 listed in the “mandatory analytical suite”. A random list of chemicals is listed under Conductivity, Redox and pH including a vitamin, food preservatives and a range of compounds that would either not be found or could not be determined by routine analyses.

The simplistic approach to the determination of redox and resistivity in disturbed samples also causes some concern. This should at least reference BS 1377 Part 3:1990 and mention the benefits of in-situ measurements. Other soil conditions, not necessarily associated with a brownfield site, may also need to be examined for classification, for example “Wetness Class” which, although are not directly related to contamination, are used in the examination of sites for existing or proposed ductile iron pipes.

In relation to chemical testing reference is made to detection limits – but no discussion on how these limits were arrived at is included. These are set at “at least 10 times lower that the screening values identified” which appears to be arbitrary.

Specification of Water Supply Pipes
The final part of the document, as expected, relates to the process of specification of pipes.  It provides a comprehensive list of standards and guidance for each of the options including ductile iron, steel, polyethylene (PE), PE Barrier, PVC and copper.  Further undefined terms which will have a major effect on the specification are included such as “light chemical contamination”

Unfortunately some of the chemistry in this part is also misleading. It gives a conversion from EC to resistivity, which is not applicable to soils as it does not take into account natural moisture content, compaction, voids or the benefit of in-situ measurements.  Redox is used as a criteria without proper reference to BS1377 or acknowledging the problems likely to be encountered with disturbed samples.

Once all of the results of the extended testing have been received, individual chemicals are summed in groups, which appears to be highly questionable considering the differences between each of them.  Further mistakes are noted on the Pipe Selection Table 3.1, below which is provided to make a final selection, notably with disagreements between these figures and those in F.4 (Derivation of ‘data-supported threshold values’ for PE and PVC).  In this table there would be no requirement for any analysis if Barrier Pipe (PE-Al-PE) is used as it passes on all counts.  It is felt that the selection of barrier pipe for all sites will be a frequently exercised option as this is suitable for all conditions, it would also negate the need for any of the desk study, analysis, site assessment and pipe selection process covered in the rest of the document.  A statement that “barrier pipes should be used for all brownfield sites” would make the whole of this document redundant.

Pipe material

All threshold concentrations are in mg/kg

Parameter group

PE

PVC

Barrier pipe
(PE-Al-PE)

Wrapped Steel

Wrapped Ductile Iron

Copper
 

1

 Extended VOC suite by purge
and trap or head space
and GC-MS with TIC

0.5

0.125

Pass

Pass

Pass

Pass
1a + BTEX + MTBE

0.1

0.03

Pass

Pass

Pass

Pass
 

2

 SVOCs TIC by purge and trap or
head space
and GC-MS with TIC (aliphatic
and aromatic C5 – C10)

2

1.4

Pass

Pass

Pass

Pass
2e + Phenols

2

0.4

Pass

Pass

Pass

Pass
2f + Cresols and chlorinated
   phenols

2

0.04

Pass

Pass

Pass

Pass
3 Mineral oil C11-C20

10

Pass

Pass

Pass

Pass

Pass
4 Mineral oil C21-C40

500

Pass

Pass

Pass

Pass

Pass
 

5

 Corrosive (Conductivity, Redox
and pH)

Pass

Pass

Pass

Corrosive if pH < 7
and conductivity
> 400μS/cm

Corrosive if pH < 5 , Eh
not neutral and
conductivity > 400μS/cm

Corrosive if
pH < 5 or > 8
and Eh
positive
Specific suite identified as relevant following Site Investigation
2a Ethers

0.5

1

Pass

Pass

Pass

Pass
2b Nitrobenzene

0.5

0.4

Pass

Pass

Pass

Pass
2c Ketones

0.5

0.02

Pass

Pass

Pass

Pass
2d Aldehydes

0.5

0.02

Pass

Pass

Pass

Pass
6 Amines

Fail

Pass

Pass

Pass

Pass

Pass

Table 3.1: Pipe selection table

Conclusions

Although the document recommends a staged process of desk study, investigation, assessment and specification there are several areas where it is far from satisfactory.  Lack of suitable detail, ignorance of current guidance and an unwieldy and expensive approach to chemical analysis has made the process of selecting suitable pipe materials almost impossible.

Given the potential complexity and cost of the investigation and analysis to fulfil the requirements of the document it is likely that developers and specifiers will often take the simpler approach of always using barrier pipes in brownfield sites when there is any possibility of contamination.  This will be the case in most existing domestic plots and extensions (where the presence of a garage or garden shed would lead to the onerous investigation procedure) and may in turn lead to barrier pipes being unnecessarily specified.  It is also possible that the replacement of lead water pipes will be prevented by the higher costs caused by following this guidance.

We would recommend that the document goes through a further period of consultation including commercial laboratories, consultants and industry groups (such as EIC, NHBC and AGS).  The limitation of desk studies and PID screening should be added and more guidance and reference on the investigation, preparation of a conceptual model and provision of competent personnel given.  A more flexible approach to analysis should be taken, relating the testing to the previous site usage.  The selection process should also be made simpler, making the choice of other pipe materials more likely.

Article Contaminated Land Laboratories

The problem of made ground

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Tags: analysis brownfield sites Environment Agency Geoscientists laboratory MCERTS soil

The categorisation, analysis and reporting of ‘made ground’ is a recurring nightmare for the modern laboratory. Traditionally a by-product of land reclamation schemes, a container of the stuff can contain traces of anything from steel, concrete and brick to nappies and Coke cans – and that’s on a good day.

Ask anyone from the engineer taking samples at the coalface to the men in white coats analysing them, and you will find that there is no all-encompassing approach to deal with the ‘made ground’ conundrum. Nevertheless, with brownfield sites being universally hailed as the sustainable way forward, now, more than ever before, is the time to seriously evaluate the methods employed both on-site and in the laboratory and try to circumvent the insidious ‘no easy answer’ maxim.

Much of the confusion goes back to the introduction of the Environment Agency’s Monitoring Certification Scheme (MCERTS) for the chemical testing of soils. Any laboratory operating under this banner has to submit results that fulfil both the general requirements of ISO/IEC 17025 and the specific method validation and performance requirements of MCERTS. The latter is problematic for laboratories dealing with made ground, inasmuch as it requires samples to conform to specific sample matrices in order for the results to become accredited. For relatively unadulterated soils, this has meant the creation of soil classification categories such as ‘loamy soil’, ‘sandy soil’ or ‘clay type soil’. It is worth noting that while some geotechnical engineers may see this as a tenuous oversimplification, it is widely regarded as the best available approach and has the full endorsement of the Environment Agency and UKAS – albeit based on economical drivers. Made ground’s inherent ambiguity throws a rather obtrusive spanner in the works when faced with these basic matrices and prompts all manner of interpretive stances and questions. Some good starters for ten: can you report made ground results as accredited? Is it possible to report them as ‘unaccredited’ to make it clear to the engineer that the sample does not fall into a clear defined matrix?

It isn’t just an issue of categorisation – the whole process, from preparation to final report, is divested of any consistency as laboratories adopt their own approach by asking questions such as do we dry the sample? Do we mill the sample to uniform particle size? Do we discard anything over 2mm? Do we ignore everything that is not soil? None of these methods will provide an inaccurate result per se, but each has the potential to give a misleading picture of the site.

If, in addition to that head-scratching list of questions, you consider the fact that the commercially driven nature of redevelopment schemes has turned laboratories into high-tech, scientific conveyor belts, the complexities of the problem becomes increasingly pronounced. It is a crossroads situation reliant on good judgement, experience and, above all, a decent sample. It is impossible to overstate the critical nature of the latter point: without a comprehensive sample, the laboratory cannot do its job. In other words, it cannot capture the essence of a site’s industrial legacy and act as a signpost to the appropriate action.

Though MCERTS has to a certain extent raised the standards in the laboratory, it missed an opportunity by not offering any guidance to the geotechnical engineer on the best available techniques (BAT) for sampling, storage and transportation; nor does it elaborate on the consequences of incorrect, inappropriate or inadequate sampling. The reason the EA has put the onus on the laboratories is understandable – to allow continuity of testing pre- and post-MCERTS – but the resultant confusion and knowledge deficit, particularly with regards to sampling, is less than satisfactory.

As throwing legislation at the problem is unlikely to be constructive, the best achievable course of action is to engender a milieu of interdisciplinary compatibility fuelled by open lines of communication, intellectual communality and the symbiotic sharing of knowledge. Geoscientists should learn how to adequately describe their sample, how to make the sample manageable for the laboratory and to understand the laboratory machinations of sample preparation, analysis and reporting. By the same token, chemists should acquire some field experience, learn about the conditions engineers face on-site and educate themselves on the processes that inform geotechnical sampling techniques.

If the question of how to produce consistently accurate results from made ground is reducible to a single answer, it can only be to ask more questions: what are the limitations of the selected analytical method? If there are limitations, do they matter in this case? On what basis is the data reported? Does it match the basis on which my acceptance criteria are calculated? Has the sample data been generated in ideal conditions using ideal standards which are unlikely to represent the conditions on my site? Add a soupçon of communication, wait for MCERTS to catch up and we’re well on our way.

Andrew Buck PhD, MSc, CSci, CChem, FRSC is the Technical Director of Envirolab (www.envlab.co.uk)

Article Contaminated Land Laboratories

ISO/TC190 Meeting, Paris Note prepared by Peter Rodd

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Tags: analysis chemical and ecotoxicological Geoenvironmental Geotechnical soil quality

For the fourth year running I attended the ISO/TC190 Soil Quality meeting, this year in Paris. The meeting comprises sessions of the various Sub Committees and their working groups plus plenary sessions for the Sub Committees, and the TC190 and CEN TC345 (both Soil Quality) meetings. I attended 7 sessions.

As previously, I was representing the BSI committee EH/4 (Soil Quality) on which I serve, in turn, representing the AGS.

As with last year’s meeting in Brno, the Czech Republic, much of the general discussion concerned the Horizontal Project originally instituted by CEN. The purpose of this project is to harmonize standards across matrices.. Once a Horizontal Standard has been created and endorsed by CEN it becomes a European Standard and supersedes equivalent National Standards and International Standards within the EC. If it is also accepted by ISO the new standard supersedes the equivalent ISO Standard in the rest of the world; if not accepted by ISO it runs side by side with the ISO as a European Standard. It is now ISO TC190’s first function to respond to CEN requests to develop new standards while continuing to develop standards that have international support. Everything clear so far?

Although the function of EH/4, ISO TC190 and CEN TC345 is Soil Quality from the soil science perspective, there are clearly overlaps with geotechnical and geoenvironmental engineering, particularly in light of the Horizontal Project, and this is the reason why the AGS agreed to have representation on the EH/4 committee. Topics of particular relevance are the chemical test methods being developed that will be used for compliance issues arising from the sludge directive.

The function of EH/4 is to assist in the development and review of International and European standards, and to put forward comments received initially from the EH/4 sub committees on early committee drafts (CD), and at a later stage comments from interested parties more generally on draft international standards (DIS). The latter stage is where AGS members get the chance to make comments (which can be funnelled through me) to EH/4 and thence to the ISO TC190 working groups. The annual meeting is the usual forum for discussion of such comments. Following DIS stage the document becomes a final draft (FDIS) at which stage comments are largely restricted to editorial issues. The member countries then vote to determine whether the document should become an International Standard. If BSi give a positive vote and the document is passed as an International Standard it automatically becomes a British Standard. If a member country votes ‘No’ then they do not adopt the ISO standard, even if passed, as their National standard.

The sessions I attended were: ” CEN 345 – Characterisation of soils; ” ISO/TC 190 Plenary – Soil Quality; ” SC7 WG4 – Human Exposure; ” SC7 WG6 – Leaching; ” SC7 WG7 – Background Levels; ” SC7 Plenary – Soil and Site Assessment; and ” SC3 Plenary – Chemical Methods.

The CEN meeting concentrated on various existing standards and whether they were suitable as Horizontal Standards. Previously questionnaires had been sent to member countries to get their views but only brief responses were forthcoming. One standard of particular relevance to the AGS is ISO 11277 ‘determination of particle size distribution in mineral soil material – method by sieving and sedimentation’. It was felt by the delegates that this test method is time consuming and is not generally used, therefore, it will not be recommended as a Horizontal standard but will remain as an ISO and should be used as a reference method. Other test methods discussed were: ISO 10381-3 on safety, ISO 10381-4 Guidance on the procedure for investigation of natural, near-natural and cultivated sites, ISO 10694 organic and total carbon after dry combustion (elementary analysis), ISO 11261 Total Nitrogen, ISO 11263 Phosphorus spectrometric soluble in sodium hydrogen carbonate, ISO 14255 Nitrate, ammonium and total soluble nitrogen using calcium chloride, and ISO FDIS 16772 mercury in aqua regia. It was felt that none of the standards could be recommended to Horizontal without review and that ISO 10381.4 was to general and would conflict with national standards, and ISO 11263 was not used and should also not be recommended.

Registration of new work items for CEN and their terms of reference will be controlled by BT TF151, a task force set up for that purpose and to receive the Horizontal draft CEN standards. They will also co-ordinate the CEN response to these standards.

One item of interest from the ISO TC190 plenary meeting was that methods for the analysis of asbestos were considered to be outside the scope of soil quality and that TC146 will develop methods although TC190 will be involved in the handling and sampling aspects.

The SC7/WG4 session considered to documents; ISO 15800 on the characterisation of soils with respect to human exposure that was reported as having been issued as a full standard, and CD 17924 on the bioavailability of metals in contaminated soils – physiological based extraction method which will be amended in light of the discussions and comments received and issued as a DIS in June 2005. The stated aim of this document is to establish a list of parameters and is aimed at risk assessors.

I attended the second session of SC7/WG6 and discussion focused on CD 19492 ‘Leaching procedures for subsequent chemical and ecotoxicological testing of soils and soil materials – influence of pH on leaching with initial acid/base addition’. The procedure is considered to be generic. An annex will be added to explain the use of the various pH levels and extraction solutes. Validation of the method is required but funding will be required and so the document, initially, will be a technical specification. The delegates did not agree with the UK’s definition of ‘leaching’ but in any case it is defined in the document. It was considered that the agitation levels given in the document are likely to break most glassware, guidance was requested from the delegate countries. A guidance document was also discussed but this was at a very early stage of development.

SC7/WG7 discussed DIS 19258 ‘Guidance on the establishment of background values’ which was issued late due to a problem with obtaining the French translation. The DIS was approved prior to the meeting with only the UK disapproving. Although such a guidance document would be useful the EH4 committee considered that there is too much confusion in the document particularly with the terms that are used. In particular the term ‘usual background’ was considered to be somewhat imprecise and the main definitions will be re-written. Another problem with the document is that if it becomes a standard and the UK approve it, there may well be a conflict with BS 10175 which would probably have to be withdrawn.

On that alarming note I shall end my report. The next meeting will be in Japan in October.

Article Contaminated Land Laboratories

THE EXTENSION OF MCERTS TO CHEMICAL TESTING OF SOILS

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Tags: analysis Contaminated Land Land Quality Policy Statement MCERTS

Bruno Guillaume, Arup Geotechnics

In October 2001, the Environment Agency launched proposals to extend its Monitoring Certification Scheme, MCERTS to the chemical testing of soils. The aim of the scheme is to deliver quality environmental measurements with product certification of instruments, the competency certification of personnel and the accreditation of laboratories based on an international standard. In its Land Quality Policy Statement (EAS/2703/1/6/Final 3, available on http://www.environment-agency.gov.uk/commondata/105385/lqpol6re.pdf ), the Agency notes that it will only accept chemical testing data on contaminants in soils that has been produced by laboratories that have been accredited to the BS EN ISO/IEC 17025:2000 quality standard for the testing methods used.

The Agency has provided separate MCERTS performance standards in guidance available from www.environment-agency.gov.uk/business/mcerts. To allow reasonable time for laboratories to complete validation of their testing methods to the Agency’s specification, the Agency will implement this policy over a period of twelve months from 1st April 2002. From the 31st March 2003*, the Agency will require that all chemical testing data on contaminants in soils, which is presented to it in support of regulatory compliance, must have an accompanying estimate of bias and precision and a description of the testing method used, with the laboratory being accredited to the BS EN ISO/IEC 17025:2000 standard for the test method.

The MCERTS proposals were discussed at the annual Contest meeting in June at which I was asked to speak on “the client’s view”. There is no doubt that the risk-based approach to contaminated sites and especially quantitative assessment requires greater confidence in data from site investigations. All laboratories should operate quality control and quality assurance schemes with calibrations, blanks, sensitivity checks and duplicate testing. UKAS accreditation is often quoted as evidence of quality assurance, but it gives no indication of the suitability of test for the intended purpose of the end user. Proficiency testing and participation in schemes such as Contest, Aquacheck or LEAP is a far better indication of a laboratory’s ability to undertake tests reliably. However, the results of proficiency testing are seldom available to third parties, such as those organisations commissioning tests from the laboratories. MCERTS has the potential to provide an indication of data reliability with performance standards set by an authoritative body.

Laboratories have expressed concerns over certain aspects of the MCERTS proposals as applied to the chemical testing of soils. Sampling is potentially a far greater source of data errors than is laboratory analysis, and there is as yet no comparable scheme addressing sampling, in-situ and field tests. The performance standards requested by the Environment Agency are too demanding and prescriptive for certain parameters (e.g. limit of detection of 20mg/kg for sulphates) and ill defined for certain parameters (e.g. are “polyaromatic hydrocarbons” represented by the sum of USEPA priority 16 or defined by other means?).

The Environment Agency is considering certification schemes to address field aspects including sampling. It is worth noting, at this point, that the Agency has produced guidance, (including Technical aspects of site investigation, P5-065/TR and Secondary model procedures for development of appropriate soil sampling strategies, P5-066/TR), though this has been poorly publicised.

Accreditation of laboratories to BS EN ISO/IEC 17025:2000 (General requirements for the competence of testing and calibration laboratories) is significant: clause 4.1.2 states that it is the responsibility of the laboratory to carry out its testing and calibration activities in such a way as to satisfy the needs of the client. The requirement for the laboratory to understand the client’s needs is explicit. Currently, too many clients will commission testing without discussing objectives with the laboratory. Unfortunately, the market is driven by price rather than quality and there are still laboratories that offer methods that are inappropriate. An uninformed client cannot distinguish between good and bad service providers. The introduction of MCERTS and accreditation to BS EN ISO/IEC 17025:2000 could act as a catalyst to encourage the engagement of laboratories earlier in the investigation process, thus ensuring that the laboratory methods are fit for purpose.

MCERTS does not specify the methods of analysis, and proficiency testing shows an astonishingly wide variation in results for certain parameters. This is due to the variety of methods in use and economic pressures in a market where there is over capacity, as well as poor parameter definition and lack of performance standards. Method specification through international standards is an extremely slow process and not favoured in the UK. Research has however been undertaken, funded by the Government and the Environment Agency, on appropriate methods of analysis, and the results of this research are still awaited.

Finally, the risk assessment approach to contaminated land requires further guidance which has yet to be provided by the regulators, including suitability of leaching tests, bio-availability and toxicity assessments. The process of investigation and assessment is complex and potential for errors considerable, but MCERTS should at least address one part of the process and raise the importance of appropriate data.

References: Environment Agency, Performance Standard for Laboratories Undertaking Chemical Testing of Soil, May 2002, Version 1 <http://www.environment-agency.gov.uk/commondata/105385/soiltest.pdf> UKAP, Good Regulation and Competitiveness Network – Environment Sector Study, July 2001, <http://www.chemsoc.org/pdf/ukap/enviro.pdf> Hazel Davidson, VAM Bulletin No. 21, 1999, 4 , <http://www.vam.org.uk/news/news_bulletin.asp>

*Note: The intention to implement to this timetable has been withdrawn to allow a more realistic timescale for the accreditation of laboratories. A statement on the EA website reads:

‘Having recently met with UKAS and discussed the concerns of a number of laboratories with respect to the timescales for compliance, the Agency has decided to revise the phased approach to implementation of its requirements to allow a longer lead in time. In addition, the Agency has decided to take this opportunity to review the detail set out in the performance standard with a view to streamlining the additional requirements over EN ISO/IEC 17025:2000 which are already assessed. We will issue a revised implementation policy and performance standard shortly. In the interim, laboratories are urged to seek the accreditation to EN ISO/IEC 17025:2000 for the chemical testing of soils which is already available.