Keeping it pure and simple
22 Feb 2012 by Evoluted New Media
Wayne Civil discusses the impact of the comprehensive screening capability developed by the NLS technical team
In December 2000, the European Water Framework Directive came into force and became part of UK law in December 2003. Its objective was to provide opportunities to plan and deliver a better water environment with a focus on ecology. The introduction of this Directive aimed to help protect and enhance the quality of surface freshwater (including lakes, streams and rivers), groundwaters, groundwater dependent ecosystems, estuaries and coastal waters out to one mile from low-water.
However, currently there is a range of inconsistent European legislation that covers different aspects of water management. The new Water Framework Directive (WFD) aims to introduce a simpler approach, resulting in greater protection for a vital part of our environment. As a result of the WFD, a number of existing European directives will be replaced.
The WFD looks at the ecological health of surface water bodies as well as achieving traditional chemical standards. In particular, it will help to deal with diffuse pollution which remains a big issue after most point source discharges have been improved. To carry out the WFD, it is important to identify environmental standards to use in protecting ecology from pressures such as damaging engineering works.
In order to address this and, in particular, the ‘chemical challenge’ of the Water Framework Directive, the Environment Agency commissioned the National Laboratory Service (NLS) to develop a low cost and effective way of implementing this element of the WFD that also utilised the new technologies available to laboratories.
The most hazardous chemicals have impacts on the environment at extremely low concentrations. Complex sample matrices can often obstruct the identification of target compounds by high-level chemical noise, resulting in substandard library match factors. Background subtraction is both matrix-and-operator dependent and this can generate inconsistent results.
Current analytical methods traditionally used to analyse for organic pollutants only target a subset of the possible chemicals present. Each subset may require a separate sample to be taken and the combined cost of this analysis can prove expensive.
Due to these restrictions, the NLS developed the GCMS Target Based Screening methods which allow for virtually all GC-amenable pesticides as well as hundreds of other organic pollutants to be identified from a single sample. At the heart of the GCMS screening capability is the Deconvolution Reporting Software (DRS) application for target compound analysis. This application combines results from the GCMS Chemstation, the Automated Mass Spectral Deconvolution and Identification Software (AMDIS) and the NIST08 Mass Spectral Search Program (NIST).
In simple terms, operating in full scan mode combined with DRS enables over 950 target compounds to be analysed for, all from that one sample. The DRS automatically deconvolutes the signal using AMDIS, which dramatically increases the accuracy of target identification.
In more detail; target compounds are first identified using four extracted ions and comparing ion ratios along with retention time (Chemstation). AMDIS deconvolutes the Chemstation data file. These ‘cleaned’ spectra are compared against the NLS generated target database. This comparison uses full spectra. Identified targets are sent to NIST for confirmation. NIST searches all spectra sent by AMDIS against the NIST08 ~ 160,000 compound main library. This is also a full spectrum search but now against a different library than used by AMDIS. The final report combines results from the three techniques.
An additional manual search procedure has also been developed which enables the identification of non-target compounds.
The development programme began in 2006 with the purchase of the Hazardous Industrial Chemicals (HIC) target database. This contained 467 compounds and provided a sound platform to build on. Since then, the target database has been expanded to better reflect monitoring requirements and now contains over 960 compounds. As a 'living' database this number will continue to grow.
There are many applications where these methods are routinely deployed, for example:
- The Environment Agency’s Groundwater Quality and Protection teams use the GCMS Target Based Screening to support their routine statutory monitoring programme. They operate a risk-based programme that follows WFD-UKTAG (United Kingdom Technical Advisory Group) and EU monitoring guidance. - Discharges to ground investigations. - Annual auditing of landfill sites. - Delivering chemical scans for the EU Water Framework Directive by helping to determine where there is a risk of failure and to direct more detailed, quantitative monitoring/analysis. - Sewage effluent treatment processes. - Oslo and Paris Conventions (OSPAR). International reporting on loads to the marine environment, national reporting (SoE), policy on load reductions. Target Based Screening supplements the existing programme of chemical spot samples. - Potable raw waters. - Investigating environmental threats / pollution incidents.
Matrices analysed include fresh water, ground water, saline, sewage effluents, trade effluents, leachates and sediments.
One of the key stages in implementing the WFD is the monitoring programme, which builds on existing water chemistry and ecological monitoring programmes. The WFD monitoring programme began in December 2006 and was developed using the European Commission’s Common Implementation Strategy (CIS) guidance and the UK Technical Advisory Group paper 12a.
This network allows for assessment of the ecological and chemical status of surface waters, and the chemical and quantitative status of groundwater. The programme covers rivers, lakes, estuaries and coastal water, groundwaters and protected areas as required by the Directive.
It is through forward-looking developments in the testing methods that a much greater range of ecological and chemical parameters and waterbody types than ever before can now be monitored. For selected waterbodies, a range of biological, hydromorphological and physical-chemical elements are monitored and priority and priority-hazardous substances for chemical status.
In order to protect and improve water quality, standards and targets are used. By calculating the potential impacts of industry and agriculture on the environment, it is possible to set standards and targets. These also help to check national progress in protecting water quality and identify where action is needed. The standards aim to protect wildlife and nature, control risks to the quality of water abstracted for supply to our homes or used to irrigate crops and ensure that enjoyment of bathing, angling and boating is as safe as possible.
Water quality standards identify the quantity of a pollutant that can safely be present in the water environment without causing harm to the ecology. The Environmental Quality Standards are used for assessing the state of the water environment through classification and is used in the monitoring programme.
Traditionally, these standards and targets were achieved through risk-based planning; using existing and historical knowledge to determine the pressures and impacts on water bodies. These assessments then formed the basis of the risk assessments. This process relied heavily on accurate data and did not enable new compounds or risks to be identified.
The new screening methods fill the gaps created by these historically-reliant risk assessments, and validate the data through a refining of the original risk assessment; so instead of using historical data to determine risk, the GCMS target based screening methods identify many emerging compounds to better inform the risk assessment.
Driven by the WFD legislation, these new screening capabilities provide a powerful monitoring tool in assessing the pressures on a given watercourse, helping to ensure this legislation is met.
The Author: Wayne Civil is technical specialist at the National Laboratory Service
Contact: t: 0113 231 2177 w: www.natlabs.co.uk
