1.1 Air quality monitoring in Gibraltar

The Gibraltar Air Quality Data Digest provides an annual summary of the air pollutant measurements from the Gibraltar Air Quality Monitoring Network for 2019.

The Gibraltar Air Quality Monitoring Network is operated on behalf of the Government of Gibraltar by the Environmental Agency, with assistance from Ricardo Energy & Environment. The principal objective of the Gibraltar Air Quality Monitoring Network is for compliance reporting against the European Air Quality Directive (AQD) on ambient air quality and cleaner air for Europe (2008/50/EC) and the Fourth Daughter Directive (DD4) (2004/107/EC).

The Gibraltar Air Quality Monitoring Network includes a mixture of automatic pollutant monitoring stations and non-automatic air pollutant monitoring sites. The automatic air quality monitoring stations measure:

• Oxides of nitrogen (NO_X) and nitrogen dioxide (NO₂)

• Sulphur dioxide (SO₂)

• Ozone (O₃)

• Carbon monoxide (CO)

• Particulates (PM₁₀, PM_2.5)

• Heavy metals: Arsenic (As), Cadmium (Cd), Nickel (Ni), Lead (Pb)

• Benzene (Bz) and

• Polycyclic aromatic hydrocarbons (PAH), including Benzo[a]Pyrene (B[a]P).

Non-automatic sites measure monthly average concentrations of NO₂ and benzene using a passive diffusion tube based method. Diffusion tube measurements have a much higher uncertainty than automatic measurements and are purely indicative of air pollutant concentrations. As such they cannot be compared against the specific legislative values specified in the European Air Quality Directive. Further information on the air pollutants measured in Gibraltar can be found on the Air Quality in Gibraltar website.

The sites within the Gibraltar automatic air quality monitoring network provide a combination of high resolution hourly measurements and daily average air pollutant concentrations. High resolution information is communicated rapidly to the public. The main platform for information dissemination of air quality measurement in Gibraltar is the Air Quality in Gibraltar website. Non-automatic measurement sites provide an indicative measure of roadside and background air pollutant concentrations at thirty-two sites throughout Gibraltar.

The major objectives of the Gibraltar Air Quality Monitoring Network are:

• Checking if statutory air quality standards and targets are met (e.g., EC Directives)

• Informing the public about air quality

• Identifying long-term trends in air pollution concentrations

• Assessing the effectiveness of policies to control pollution in Gibraltar, as laid out in the Gibraltar Air Quality Action Plan.

The air pollutant measurements from Gibraltar Air Quality Monitoring Network are used for:

• Reporting to the European Commission as required by the Air Quality Directives

• Comparison with air quality objectives prescribed by the Air Quality Directives

• Providing the public with information through air quality bulletins

• Forecasting future air quality levels

• Policy development for human health protection.

This document provides graphical analysis and explanatory summaries of the air pollutant measurements made in Gibraltar. Compliance plots (as discussed in Section 2.2) are used to present concentrations for 2019 in the context of historical data, highlighting whether the Limit Values (LVs) or Target Values (TVs) given in the European Air Quality Directives were achieved. The other plots presented here provide useful information from which the source of air pollutants can be inferred.

1.2 Limit Values and Target Values

A summary of the relevant legislative thresholds prescribed in the Air Quality Directive and Fourth Daughter Directive are presented in Table 1. This shows each pollutant and the relevant metric and threshold applicable. Also shown is the type of threshold: Limit Value (LV), Target Value (TV), Long Term Objective (ozone only) and the year in which each LV or TV has to be achieved. These are represented in the ‘compliance plots’ as red dashed lines and the corresponding metrics are also presented in the summary data tables in this document. The air pollutants covered under the two Directives are:

• Air Quality Directive (AQD)

  • NO_X and NO₂

  • PM₁₀

  • PM_2.5

  • CO

  • SO₂

  • Ozone

  • Benzene

  • Lead

• Fourth Daughter Directive (DD4)

  • Benzo[a]Pyrene (B[a]P)

  • Arsenic

  • Cadmium

  • Nickel

Table 1: Summary of current Limit Values and Target Values (the number of permissible exceedances per year are given in brackets next to the Value)

1.3 Air quality monitoring locations

Information on the air pollutant monitoring methods and the composition of the Gibraltar Air Quality Monitoring Network can be found on the Gibraltar Air Quality Monitoring Network website. Table 2 provides a summary of the air pollutant monitoring stations and air pollutants measured at the automatic monitoring stations and non-automatic monitoring sites in Gibraltar in 2019. Figures 1 and 2 show the locations of the automatic monitoring stations and the non-automatic sampling points in Gibraltar in 2019, respectively. Mobile monitoring has been added into the network since 2018 and these sites and concentrations have been presented in Section 3.8.

Table 2: Summary of automatic monitoring stations and non-automatic monitoring sites in Gibraltar in 2019.

Figure 1: Location of automatic air quality monitoring stations in Gibraltar, 2019 (see interactive map in subsection 2.1)

Figure 2: Location of non-automatic air quality monitoring sites in Gibraltar, 2019 (see interactive map in subsection 2.1)

Table 3: Co-ordinates of non-automatic air quality monitoring sites in Gibraltar, 2019, as shown in Figure 2.

1.4 Data processing

The data summaries and plots presented this document were generated using openair, an open-source air quality analysis toolset written