CHAPTER 4Assessment
Duty to assess air quality
12. The Scottish Ministers shall assess the concentration of each pollutant within each zone in accordance with regulations 13 to 16.
Assessment methods
13.—(1) Subject to paragraph (2), the Scottish Ministers shall assess concentrations of a Group A pollutant by fixed measurement where–
(a)the assessment takes place within an agglomeration; or
(b)in any other zone, representative concentrations of that pollutant exceed the relevant upper assessment threshold.
(2) Where the zone concerned is the same as that established under the Air Quality Limit Values (Scotland) Regulations 2003(1) (“the 2003 Regulations”), the Scottish Ministers may continue to use the method by which concentrations of a Group A pollutant were assessed within that zone under the 2003 Regulations (“the 2003 method”).
(3) Except where fixed measurement is required by paragraph (1) or they continue to use the 2003 method in accordance with paragraph (2), and, in the case of nitrogen dioxide, subject to the requirements imposed by regulation 15(7), the Scottish Ministers may assess concentrations of a Group A pollutant by any one of the following methods–
(a)fixed measurement;
(b)combined measurement; or
(c)the sole use of modelling or objective estimation techniques, provided that representative concentrations of the pollutant in the zone concerned are below the relevant lower assessment threshold.
(4) The Scottish Ministers shall assess concentrations of a Group B pollutant by fixed measurement in any zone in which representative concentrations of that pollutant exceed the relevant upper assessment threshold.
(5) Except where fixed measurement is required by paragraph (4), the Scottish Ministers may assess concentrations of a Group B pollutant by one of the following methods:–
(a)fixed measurement;
(b)combined measurement; or
(c)the sole use of modelling or objective estimation techniques, provided that representative concentrations of the pollutant in the zone concerned are below the relevant lower assessment threshold.
(6) For the purposes of paragraphs (1) and (3) to (5), the Scottish Ministers shall determine the representative concentrations in accordance with Part 3 of Schedule 4.
(7) The Scottish Ministers shall review the method by which concentrations of a Group A or Group B pollutant are assessed at least once every five years or earlier if there are significant changes in activities affecting concentrations of the relevant pollutant within the zone concerned.
(8) Where the Scottish Ministers continue to use the 2003 method, the date from which the period of review commences is the later of–
(a)the date the zone was classified under regulation 7(1) of the 2003 Regulations; or
(b)the date on which that classification was last reviewed under regulation 8 of those Regulations.
(9) The Scottish Ministers shall assess concentrations of ozone by fixed measurement if, within the zone concerned, concentrations have exceeded a long-term objective during any of the previous five years of measurement.
(10) In cases where fewer than five years' information on concentrations is available, the Scottish Ministers may assess concentrations of ozone by combining the following:–
(a)measurement campaigns of short duration at times and locations which they consider are likely to be typical of the highest pollution levels; and
(b)results from emission inventories and modelling.
Fixed and combined measurement
14.—(1) Where the Scottish Ministers assess concentrations of a Group A or Group B pollutant by fixed measurement, whether alone or as part of combined measurement, they shall ensure that–
(a)measurements of the relevant pollutant are taken at sampling points either continuously or by random sampling, subject, in the case of nitrogen dioxide, to the requirements imposed by regulation 15(7); and
(b)the number of measurements is sufficiently large to enable concentrations of that pollutant to be properly determined.
(2) Where the Scottish Ministers assess concentrations of a Group A or Group B pollutant by fixed measurement, they may supplement information from sampling points for fixed measurement with information from modelling techniques in so far as they consider this will provide an adequate level of information on ambient air quality.
(3) Where the Scottish Ministers assess concentrations of ozone by fixed measurement–
(a)they shall ensure that–
(i)the measurements are taken at fixed sites continuously; and
(ii)the number of measurements is sufficiently large to enable concentrations to be properly determined;
and
(b)they may supplement information from sampling points with information from modelling techniques or indicative measurements.
Sampling points
15.—(1) Where the Scottish Ministers assess concentrations of a Group A or Group B pollutant by fixed measurement they shall, except in cases falling within paragraph (2)(a), install the number of sampling points required for the zone in accordance with the relevant Part of Schedule 5.
(2) Where the Scottish Ministers assess concentrations of a Group A or Group B pollutant by–
(a)fixed measurement, in cases where they obtain information from modelling techniques under regulation 14(2); or
(b)combined measurement,
they shall install the number of sampling points they determine is sufficient, taken together with the spatial resolution of the other techniques employed, for concentrations of the relevant pollutant to be established within the zone concerned.
(3) The Scottish Ministers shall locate all sampling points for Group A and Group B pollutants in accordance with the requirements set out in the relevant Parts of Schedule 6.
(4) Where the Scottish Ministers assess concentrations of ozone by fixed measurement they shall, except where paragraphs (5) or (6) apply, install the number of sampling points required for the zone in accordance with Part 4 of Schedule 5.
(5) In the case of zones where–
(a)five years of measurement have been carried out; and
(b)during each of those years, concentrations of ozone have been below the long-term objectives,
the Scottish Ministers may determine the number of sampling points in accordance with Part 5 of Schedule 5.
(6) In the case of zones in which the Scottish Ministers supplement the information obtained from sampling points for fixed measurement with information from modelling techniques or indicative measurement in accordance with regulation 14(3)(b), they may reduce the number of sampling points for ozone provided that–
(a)they consider that the modelling techniques adopted provide an adequate level of information for the assessment of air quality with regard to–
(i)the target values;
(ii)the information threshold; and
(iii)the alert threshold;
(b)they consider that the number of sampling points to be installed and the spatial resolution of other techniques are sufficient for the concentration of ozone to be established and to enable the compilation of assessment results as specified in Part 3 of Schedule 7;
(c)the number of sampling points in each zone amounts to–
(i)at least one sampling point per two million inhabitants; or
(ii)one sampling point per 50,000 km2,
whichever produces the greater number of sampling points;
(d)each zone contains at least one sampling point; and
(e)concentrations of nitrogen dioxide are assessed at all remaining sampling points except rural background stations.
(7) The Scottish Ministers shall ensure that–
(a)except where paragraph (6)(e) applies, concentrations of nitrogen dioxide are assessed at at least half of the number of sampling points required to be installed for ozone in accordance with Part 4 of Schedule 5; and
(b)the measurement of nitrogen dioxide taken at any sampling point is continuous, except at rural background stations where other measurement methods may be used.
(8) The Scottish Ministers shall locate all sampling points for ozone in accordance with the requirements set out in the relevant Parts of Schedule 6.
Other assessment requirements
16.—(1) When the Scottish Ministers undertake assessments by methods other than fixed measurement, they shall comply with the requirements of the relevant Part of Schedule 7 when using those other methods.
(2) When conducting any assessment under this Chapter, the Scottish Ministers shall have regard to the relevant data quality objectives set out in Schedule 8.
(3) The Scottish Ministers shall undertake assessments in accordance with–
(a)the relevant reference methods required by Schedule 9; or
(b)any alternative reference methods, where–
(i)they consider that the method in question can be determined to give equivalent results to the relevant method required by Schedule 9; or
(ii)in the case of the sampling and measurement of PM10 only, they consider that the method in question can be demonstrated to display a consistent relationship to the reference method required by Schedule 9.
(4) Measurements of volume of benzene, carbon monoxide, nitrogen dioxide, oxides of nitrogen, ozone and sulphur dioxide shall be standardised at a temperature of 293K and a pressure of 101.3 kPa.
S.S.I. 2003/428 amended by S.S.I. 2003/547 and S.S.I. 2005/300.