CEM - Abstract

Abstract Information :

According to the Environmental Protection Act, the Ministry of Environment and Water (MoEW) is in charge of organizing and conducting the monitoring of the environmental components including air quality and emission measurements, which is of great importance for the human health and sustainable development.

The Executive Environment Agency /EEA/ is established at the Ministry of Environment and Water and carries out the management of the National System for Environmental monitoring. The Agency is a National Reference Centre for the European Environment Agency.

The Air Quality laboratory is engaged in the management and execution of the regular measurements of priority air pollutants in the ambient air and in the emissions. At the moment the laboratory is accredited as a testing laboratory according to EN ISO/IEC 17025:2005/AC:2006 "General requirements for the competence of testing and calibration laboratories".

Regarding the accreditation, the main introduced elements of quality assurance and quality control (QA/QC) are the following:

Harmonisation of measurements methods and ISO/CEN standardization
The Bulgarian legislation transposes very well the common (reference) methods and criteria for assessment and management, which are described in the European legislation. However, , for SO2 the European reference method is wet chemical sampling and analysis, but in the field alternative instrumental method (NDIR), but in the field alternative instrumental method are more generally used.

The equivalence of SO2 measurement by the NDIR with the reference method using spectrophotometric analysis was tested according the requirements of new standard EN 14793:2017 Stationary source emissions. Demonstration of equivalence of an alternative method with a reference method.

Method validation
The laboratory validate non-standardized methods, laboratory-designed/developed methods, standardizes methods used outside their intended range and amplifications of standardized methods to confirm that the methods are fit for the intended use.

Various events that take place from time to time will call for a method validation. A number of such events, for example: new method developed in the laboratory; change of method; implementation of a standardised method; slight modification of method; new instrumentation, etc.

The method of validation must always be based on requirements for the specific method and the use of the data. Method validation is a tool to investigate and document that a selected method fulfils the requirements when applied in the laboratory. Method validation is carried out prior to starting routine work, thus method validation does not substitute any of activities for quality assurance in the daily work.

Type approval of instruments
For every one automatic analyzer for emission control, the following documents are available:
a) certificate for electromagnetic compliance according to the Electromagnetic Compatibility Directive;
b) TUV/ UBA reports on the suitability tests for all the components.

In addition: TUV certificate for implementation a Quality Management System in accordance with EN ISO 9001 Quality management systems - Requirements. The scope of the Quality Management System governs: research, development, manufacture and service of air quality and emissions monitoring instruments and systems.

Reference materials
Good quality control is depends on the use of high quality reference materials with known true concentration. A certified reference materials is traceable to a certificate or other documentation issued by a certifying body and provide the essential traceability in measurements. Certified reference materials are used to demonstrate the accuracy of results, to calibrate equipment and to validate methods.

Intercomparison exercises
The laboratory takes a part in the process of harmonizing emissions measurements by international quality assurance and quality control exercises. EEA takes a part in the proficiency testing (PT) schemes in the stack emissions measurement area: Gas Measurement and Gas Cylinder, orginised from National Physical Laboratory (NPL), Teddington, England (July, 2017). NPL is accredited according to the standard EN ISO/IEC 17043 Conformity assessment - General requirements for proficiency testing.

Uncertainty of measurements
Uncertainty of measurements /U/ is defined according to EA-4/16 Guidelines on the expression of uncertainty in quantitative testing. For a measurement procedure a uncertainty budget is estimated based on the combination of uncertainties for each contribution. The combined uncertainty calculated by taking the square root of the sum of the squared estimates of the standard deviations of all uncertainty contributions. Then the overall uncertainty is obtained by multiplying the combined uncertainty with the coverage factor k = 2. In the case of normal distribution the factor k = 2 means, that the limits of the overall uncertainty are estimated using a confidence level 95%.