17.—(1) The Secretary of State shall install and operate measuring stations to supply representative data on concentrations of PM2.5.
(2) The Secretary of State shall—
(a)determine the number of measuring stations he considers necessary;
(b)locate each measuring station—
(i)together with a sampling point for PM10, where this is possible; or
(ii)in any other case, in accordance with the principles set out in Parts 1, 4 and 5 of Schedule 6 which are relevant to PM10;
(c)use reference methods for sampling and measurement that he considers suitable; and
(d)have regard to the data quality objectives set out in Part 1 of Schedule 8.
18.—(1) The Secretary of State shall install and operate one or, if he considers it necessary, more measuring stations, to supply data on concentrations of the ozone precursor substances set out in Schedule 10.
(2) When complying with paragraph (1), the Secretary of State shall have regard—
(a)generally, to Annex III of the Decision referred to in regulation 11(6); and
(b)in choosing the number and sites of the measuring stations and in their operation, to Schedule 10.
19.—(1) The Secretary of State shall monitor concentrations of—
(a)basic polycyclic aromatic hydrocarbons; and
(b)any additional polycyclic aromatic hydrocarbons which he decides should be monitored,
at monitoring sites designated by him for this purpose.
(2) The Secretary of State shall locate each monitoring site—
(a)together with a sampling point for benzo(a)pyrene, where this is possible; or
(b)in any other case, in accordance with those Parts of Schedule 6 relevant to Group B pollutants.
(3) The total number of monitoring sites and their overall selection shall be such as the Secretary of State considers necessary to ensure that the monitoring provides sufficient information to identify long-term trends and geographical variation in the concentration of each polycyclic aromatic hydrocarbon.
(4) Regulation 16(2) and (3) shall apply to the monitoring required by this regulation as if such monitoring were an assessment under Chapter 4 of Part 2.
20.—(1) The Secretary of State shall install and operate background sampling points to provide the measurements referred to in paragraph (2).
(2) The measurements are indicative measurements of—
(a)concentrations of—
(i)Group B pollutants;
(ii)basic polycyclic aromatic hydrocarbons; and
(iii)total gaseous mercury;
and
(b)total deposition of—
(i)Group B pollutants, within the PM10 fraction;
(ii)basic polycyclic aromatic hydrocarbons; and
(iii)mercury.
(3) For the purposes of paragraphs (1) and (2), the Secretary of State shall ensure that—
(a)at least one sampling point is installed for every 100,000 km²; and
(b)each sampling point is located in accordance with those Parts of Schedule 6 relevant to Group B pollutants.
(4) Regulation 16(2) and (3) shall apply to the taking of the measurements referred to in paragraph (2) as if the taking of these measurements were an assessment under Chapter 4 of Part 2.
(5) The Secretary of State may—
(a)in addition to the indicative measurements referred to in paragraph (2), take further indicative measurements relating specifically to particulate and gaseous divalent mercury from the sampling points installed under paragraph (1); and
(b)coordinate any measurements taken under this regulation with the European Monitoring and Evaluation of Pollutants monitoring strategy and measurement programme.
(6) For the purpose of paragraph (2)(a)(iii), “total gaseous mercury” means—
(i)elemental mercury vapour (Hg0); and
(ii)reactive gaseous mercury.