Marine Discharges
Reporting under the UWWTD
Urban Waste Water Treatment Regulations, 2001 – L.N. 340 of 2001 as amended (S. L. 549.22)
This legal notice transposed Directive 91/271/EC on Urban Wastewater Treatment. The aim of this directive is to protect the aquatic environment from the adverse effects of discharges of untreated or improperly treated urban waste water and waste water from industrial sectors and concerns the collection, treatment and discharge of domestic water, mixture of waste water and wastewater from certain indsutrial sectors as illustrated in the figure below:
The obligations under this legal notice can be summarized as follows:
- Provision of urban waste water collecting systems (sewerage) and treatment plants for all agglomerations above 2,000 population equivalents;
- Provision of a legal framework for specific authorization for all discharges of urban waste water and industrial waste water from particular sectors, as well as for all discharges of industrial waste water into urban waste water systems;
- Requires the phase out of any dumping or discharge of sewage sludge into surface waters;
- Requests that the treated urban waste water discharges and their effects are adequately monitored;
Authorizations for discharges from the urban wastewater treatment plants are provided through the environmental permits which are currently issuing under the upcoming Environmental Permit Regulations. The environmental permit stipulates that the discharge from the urban waste water treatment plants must comply with the emission limit values which are given in Annex I table 1 of the said legal notice.
Discharges into the sewerage system from various industrial sectors are permitted by the Water Services Corporation. This authorization ensures that no undesirable chemicals enters the sewerage system and requires operators to carry out regular monitoring of what is discharged into the wastewater network. For industries and companies requiring a sewer discharge permit the relevant form can be downloaded from the Water Services Corporation website.
The urban waste water treatment regulation also require that the competent authorities legal notice requires the Competent Authority to designate sensitive areas and these have been designated through L.N. 120 of 2005.
The technical and administrative requirements under this directive are given under the following articles:
Article 15:
- Monitoring of discharges from urban waste water treatment plants
- Monitoring of waters subject to discharges from the urban waste water treatment plants
This monitoring data is to be made available to the Commission within 6 months of receipt of a request.
Article 16:
This article requires member states to submit of a situation report to inform the Commission and the public on disposal of urban waste water and sludge in the area. This situation report is required every 2 years.
Article 17:
This article requires Member States to provide the Commission with information on the status and programme of implementation of the Directive This report is to be updated every 2 years.
The submission of sites to the European Commission entails the preparation of a datasheet and a map for each site, that is, for each proposed Site of Community Importance (SCI) and for each Special Protected Area (SPA), unless a proposed SCI has the exact boundary as an SPA; in the latter case only one datasheet is prepared comprising all relevant information.
Reference can be made to the Natura 2000 viewer (including datasheets) and to the Natura 2000 database to obtain information on each Natura 2000 site for European Union Member States. Information for the sites nominated by Malta is also available through these links (depending on update dates). Since a few years ago, submission of information to the European Commission is made through the uploading of the relevant material online; hence the most recent submissions made by Malta are publicly available online. The table below provides quick access to the Standard Data Forms (SDFs) and Maps for Malta’s sites.
It is important to highlight the fact that certain information might be lacking or requires updating in the near future, since through further studies and surveys, additional information, especially with respect to habitat types and species present within selected sites, will be collated. The exercise is considered to be an ongoing process, and as such, relevant information is updated accordingly when necessary. Additionally, selected information is not publicly available in view of its sensitive nature when considering the conservation of the sites/habitats/species in question.
A Reference Portal related to the Natura 2000 dataflow provides the relevant material for the dataflow in question.
Standard data forms (SDFs) & maps for terrestrial Natura 2000 sites, designated in Malta:
ERA is currently in the process of updating the Management Plans as well as Standard Data Forms (SDFs) for all Terrestrial Natura 2000 sites. The updated versions will be uploaded on ERA’s website in due course.
| Site code | Natura 2000 site name | SDF | Map |
|---|---|---|---|
| MT0000001 | L-Inħawi ta’ Għajn Barrani | Link | SAC |
| MT0000002 | L-Inħawi ta’ Pembroke | Link | SAC |
| MT0000003 | Il-Ballut tal-Wardija | Link | SAC |
| MT0000004 | Il-Maqluba (limiti tal-Qrendi) | Link | SAC |
| MT0000005 | L-Inħawi tar-Ramla | Link | SAC |
| MT0000006 | Is-Simar (limiti ta’ San Pawl il-Baħar) | Link | SAC / SPA |
| MT0000007 | Is-Salini | Link | SAC |
| MT0000008 | L-Għadira s-Safra u l-Iskoll tal-Għallis | Link | SCI / SAC |
| MT0000009 | L-Inħawi tar-Ramla tat-Torri u tal-Irdum tal-Madonna | Link | SAC / SPA |
| MT0000010 | Ix-Xagħra tal-Kortin | Link | SAC |
| MT0000011 | Għar Dalam | Link | SAC |
| MT0000012 | Wied il-Miżieb | Link | SAC |
| MT0000013 | Iċ-Ċittadella | Link | SAC |
| MT0000014 | Il-Ballut ta’ Marsaxlokk | Link | SAC |
| MT0000015 | L-Inħawi tal-Għadira | Link | SAC / SPA |
| MT0000016 | Filfla u l-Gżejjer ta’ Madwarha | Link | SAC / SPA |
| MT0000017 | Kemmuna u l-Gżejjer ta’ Madwarha | Link | SAC / SPA |
| MT0000018 | L-Inħawi tal-Buskett u tal-Girgenti | Link | SAC / SPA |
| MT0000019 | L-Inħawi tad-Dwejra u tal-Qawra, inkluż Ħaġret il-Ġeneral | Link | SAC |
| MT0000020 | L-Inħawi tax-Xlendi u tal-Wied tal-Kantra | Link | SAC |
| MT0000021 | L-Inħawi tal-Imġiebaħ u tal-Miġnuna | Link | SAC |
| MT0000022 | Il-Gżejjer ta' San Pawl (Selmunett) | Link | SAC |
| MT0000023 | Il-Magħluq tal-Baħar ta’ Marsaskala | Link | SAC |
| MT0000024 | Rdumijiet ta' Malta: Ir-Ramla taċ-Ċirkewwa sal-Ponta ta' Bengħisa | Link | SAC |
| MT0000025 | L-Għar tal-Iburdan u l-Inħawi tal-Madwar | Link | SAC |
| MT0000026 | Il-Qortin tal-Magun u l-Qortin il-Kbir | Link | SAC |
| MT0000027 | Rdumijiet ta' Għawdex: Ta' Ċenċ | Link | SPA |
| MT0000028 | Rdumijiet ta' Għawdex: Id-dawra tas-Sanap sa tal-Ħajt | Link | SPA |
| MT0000029 | Rdumijiet ta' Għawdex: Il-ponta ta' Ħarrux sal-bajja tax-Xlendi | Link | SPA |
| MT0000030 | Rdumijiet ta' Għawdex: Il-ponta ta' San Dimitri sal-Ponta ta' Ħarrux | Link | SPA |
| MT0000031 | Rdumijiet ta' Malta: Ix-Xaqqa sa Wied Moqbol | Link | SPA |
| MT0000032 | Rdumijiet ta' Malta: Ras il-Pellegrin sax-Xaqqa | Link | SPA |
| MT0000033 | Rdumijiet ta' Malta: Wied Moqbol sal-Ponta ta' Bengħisa | Link | SPA |
| MT0000034 | L-Inħawi ta' Ta' Ċenċ | Link | SAC |
| MT0000035 | L-Inħawi ta’ Ħas-Saptan | Link | SCI |
| MT0000036 | L-Inħawi tal-Wej | Link | SCI |
| MT0000037 | Wied il-Mielaħ u l-inħawi tal-madwar | Link | SCI / SPA |
Standard data forms (SDFs) & maps for marine Natura 2000 sites, designated in Malta:
| Site code | Natura 2000 site name | SDF | Map |
|---|---|---|---|
| MT0000101 | Żona fil-Baħar bejn Rdum Majjiesa u Għar Lapsi | Link | SAC |
| MT0000102 | Żona fl-inħawi ta' Għar Lapsi u ta' Filfla | Link | SAC |
| MT0000103 | Żona fil-Baħar fl-Inħawi tad-Dwejra (Għawdex) | Link | SAC |
| MT0000104 | Żona fil-Baħar bejn il-Ponta tal-Ħotba u Tal-Fessej (Għawdex) | Link | SAC |
| MT0000105 | Żona fil-Baħar bejn il-Ponta ta’ San Dimitri (Għawdex) u il-Qaliet | Link | SAC |
| MT0000106 | Żona fil-Baħar fit-Tramuntana | Link | SPA |
| MT0000107 | Żona fil-Baħar tal-Grigal | Link | SPA |
| MT0000108 | Żona fil-Baħar fil-lvant | Link | SPA |
| MT0000109 | Żona fil-Baħar fix-Xlokk | Link | SPA |
| MT0000110 | Żona fil-Baħar fin-Nofsinhar | Link | SPA |
| MT0000111 | Żona fil-Baħar fil-lbiċ | Link | SPA |
| MT0000112 | Żona fil-Baħar Madwar Għawdex | Link | SPA |
| MT0000113 | Żona fil-Baħar fil-Punent | Link | SAC |
| MT0000114 | Żona fil-Baħar fil-Majjistral | Link | SPA |
| MT0000115 | Żona fil-Baħar fl-Inħawi tal-Graben tat-Tramuntana ta’ Għawdex | Link | SAC |
| MT0000116 | Żona fil-Baħar fl-Inħawi tal-Graben ta’ Medina | Link | SAC |
| MT0000117 | Żona fil-Baħar fl-Inħawi tal-Punet tal-Graben ta’ Malta | Link | SAC |
| MT0000118 | Żona fil-Baħar fl-Inħawi tal-Majjistral tal-Graben ta’ Malta | Link | SAC |
Links to shapefiles of the Maltese Natura 2000 sites:
- Designated under the EC Birds Directive (2009/147/EC)
- Designated under the EC Habitats Directive (92/43/EEC)
Other links
- Commission Implementing Decision (EU) 2021/159
- G.N. 1522 of 2019 – Declaration SACs – International Importance & SPAs
- G.N. 316 of 2017 – Declaration of TPAs
- G.N. 1379 of 2016 – Declaration of SACs – International Importance & SPAs
Each Member State of the European Union has the obligation, under the EC Habitats Directive (92/43/EEC), of contributing to the creation of the Natura 2000 network. This must be in proportion to the Member State’s representation within its territory of the natural habitat types and the habitats of species specified in the Annexes of this Directive; the selected sites are referred to as Sites of Community Importance (SCIs). In addition to this, the EC Birds Directive (2009/147/EC) requires Member States to protect naturally occurring wild birds and their habitats; the measures to be considered in order to affect this include, amongst others, the designation of Special Protection Areas (SPAs).
Consequent to such obligations, Malta has submitted to the European Commission a number of sites to form part of this important network. The first submission was made back in 2004, following an extensive data collation and evaluation exercise, with the assistance of national experts, commissioned through a grant of the Council of Europe as part of the Emerald network project. Further submissions and updates were made along the years, following the collation and review of additional scientific data, as well as discussions with Directorate-General for Environment.
The submission of sites to the European Commission entails the preparation of a datasheet, related to each site, in a format established by the Commission, as presented in the Commission Implementing Decision 2011/484/EU, accompanied by the boundaries for each site. Datasheets and maps for sites designated in Malta are available here.
To date, Malta has the following declared under the:
a) EC Habitats Directive (92/43/EEC):
- 3 Sites of Community Importance (SCIs), and;
- 37 Special Areas of Conservation (SACs)
b) EC Birds Directive (2009/147/EC):
- 22 Special Protection Areas (SPAs).
The above include both terrestrial and marine sites. Some SACs completely overlap with SPAs, whilst some other SACs and SCIs partially overlap with SPAs. When considering land area, over 43.6km2 (13.8%) is covered by Natura 2000 sites; while when considering the marine environment, such sites cover 4,138km2 (35.5% of Maltese waters).
Malta has reached a high degree of sufficiency
Malta is very advanced in its progress to designate terrestrial sites under the EC Habitats Directive (92/43/EEC). Its preparations reached a high percentage under the sufficiency index – 92.64% as of June 2008, as indicated in the Note on Sufficiency. This figure is the highest percentage among the States that acceded the EU in 2004 (see graph below: light green – acceded in 2004; blue – acceded before 2004; dark green – acceded after 2004).
The graph below provides an update on the state of progress by Member States in reaching sufficiency for the designation of Sites of Community Importance under the EC Habitats Directive for 2013.
The evaluation of sufficiency is not only based on the range of each habitat and species in the full territory of each Member State, but also within each of the proposed sites. To reach 100% sufficiency, data has to be updated, the proposed sites must be extended, or new sites must be proposed; such work by Malta has already been considered to achieve such objectives, and this has been communicated accordingly with the European Commission.
Reference is made to the additional information provided on the Natura 2000 newsletter.
Other links
Initial Assessment
The Marine Strategy Framework Directive (MSFD) stipulates that the Initial Assessment of the environmental status of the marine waters should comprise the following three components:
- An analysis of the current environmental status of marine waters based on physical, chemical and biological features;
- An analysis of the predominant pressures and impacts on the marine environment;
- An economic and social analysis of the use of marine waters and the costs of degradation of the marine environment.
Within this context, the Initial Assessment for Malta describes and assesses the status of Maltese marine waters based on existing data and information according to Table 1 of Annex III of the Directive. This includes information on predominant habitat types and ecologically important species groups occurring in Maltese marine waters, as well as chemical and physical characteristics of these waters and the seabed.
Good Environmental Status and Environmental Targets
The Marine Strategy Framework Directive (2008/56/EC) defines Good Environmental Status (GES) as: ‘the environmental status of marine waters where these provide ecologically diverse and dynamic oceans and seas which are clean, healthy and productive … and the use of the marine environment is at a level that is sustainable thus safeguarding the potential for use and activities by current and future generations‘. Member States should determine GES of their marine waters on the basis of the status assessment and in accordance with the qualitative descriptors in Annex I of the Directive.
In May 2017, the EU adopted the Commission Decision 2017/848, laying down criteria and methodological standards on good environmental status of marine waters and specifications and standardised methods for monitoring and assessment, and repealing Decision 2010/477/EU. This Decision establishes a set of criteria and indicators for each Annex I descriptor to assess progress towards achievement of Good Environmental Status in marine waters. The Directive also calls for the establishment of environmental targets and associated indicators for their marine waters to guide progress towards achieving GES.
The Initial Assessment and related GES and environmental targets are updated and published every six years.
First Cycle – Malta’s Initial Assessment by theme, GES and targets
Second Cycle – Malta’s Update to the Initial Assessment, GES and environmental targets
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Air pollution causes degradation of air quality. It is a widely acknowledged fact that air pollution has adverse effects on human health and on both natural and built environment. Today, air pollution is recognised as being the single largest environmental health risk in the European Union and has been classified by the International Agency for Research on Cancer of the WHO, as a leading environmental cause of cancer deaths. Some atmospheric emissions are capable of exerting their adverse effect on both human health and the environment directly, while other emissions to the atmosphere are transformed into pollutants through complex atmospheric reactions. In addition to the affects of direct inhalation, air pollutants can make it into the human body through the food chain or water, once they deposit and accumulate in the environment. |
The principal legal instrument through which the European Union implements its policies related to Air Quality is Directive 2008/50/EC of the European Parliament and of the council of the 21 May 2008 on ambient air quality and cleaner air for Europe together with Directive 2004/107/EC of the European Parliament and of the council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air. Both these Directives were transposed into Maltese Law through the Ambient Air Quality Regulations (S.L. 549.59), which:
- Set a general policy framework for dealing with ambient air quality.
- Oblige Malta to put in place systems for assessing ambient air quality based upon common methods and criteria.
- Oblige Malta to maintain ambient air quality where it is good and improve it in other cases, by means of plans and programs of action.
- Lay down provisions for a system of gathering, reporting and publicizing information. This includes both data reported to the Commission and information to the public.
- Set limit values for sulphur dioxide, nitrogen dioxide, carbon monoxide, benzene, ozone, particulate matter (PM10 and PM2.5) and lead, which are not to be exceeded throughout the Maltese Islands.
- Set target values for arsenic, cadmium, nickel and poly aromatics expressed as benzo[a]pyrene, which are to be, as far as is reasonably possible, complied with. The following are the standards which Malta (together with the other EU Member States) is obliged to comply with.
The following are the standards which Malta (together with the other EU Member States) is obliged to comply with;
| Pollutant | Concentration | Averaging period | Permitted exceedances each year |
|---|---|---|---|
| Fine particles (PM2.5) | 25 µg/m3 | 1 year | n/a |
| Sulphur dioxide (SO2) | 350 µg/m3 | 1 hour | 24 |
| 125 µg/m3 | 24 hours | 3 |
|
| Nitrogen dioxide (NO2) | 200 µg/m3 | 1 hour | 18 |
| 40 µg/m3 | 1 year | n/a |
|
| PM10 | 50 µg/m3 | 24 hours | 35 |
| 40 µg/m3 | 1 year | n/a |
|
| Lead (Pb) | 0.5 µg/m3 | 1 year | n/a |
| Carbon monoxide (CO) | 10 mg/m3 | Maximum daily 8 hour mean | n/a |
| Benzene | 5 µg/m3 | 1 year | n/a |
| Ozone | 120 µg/m3 | Maximum daily 8 hour mean | 25 |
| Arsenic (As) | 6 ng/m3 | 1 year | n/a |
| Cadmium (Cd) | 5 ng/m3 | 1 year | n/a |
| Nickel (Ni) | 20 ng/m3 | 1 year | n/a |
| Polycyclic Aromatic Hydrocarbons | 1 ng/m3 (expressed as concentration of Benzo(a)pyrene) | 1 year | n/a |
Pursuant to regulation 32 of the Ambient Air Quality Regulations (S.L. 549.59), the Minister for the Environment has declared an Air Quality Management Area (AQMA) through the issuing of an Air Quality Management Order as laid down in Schedule 13 of the said Regulations
National Emissions Ceilings
The Directive on the reduction of national emissions of certain atmospheric pollutants (Directive (EU) 2016/2284), better known as the NEC Directive, together with the various source specific legislative instruments (such as the Industrial Emissions Directive (Directive 2010/75/EU) or the Directives setting Vehicle Emissions Standards) make possible the achievement of the standards above. The NEC Directive sets the maximum amounts (in percentages, based on the emission levels of 2005) of sulphur dioxide, nitrogen oxides, ammonia, non-methane volatile organic compounds, and PM2.5 which, can be emitted by each Member State. The Directive on the reduction of national emissions of certain atmospheric pollutants obliges Malta to achieve the following emission reductions based on 2005 emissions by 2020 and 2030, and to identify indicative emission limits in 2025. The Directive was transposed in Maltese Law through the Limitation of Emissions of Certain Atmospheric Pollutants Regulations (S.L. 549.124).
| Compliance Year | NOx | SO2 | NH3 | NMVOC | PM2.5 |
|---|---|---|---|---|---|
| 2020 | -42% | -77% | -4% | -23% | -25% |
| 2025 | -61% | -86% | -14% | -25% | -38% |
| 2030 | -79% | -95% | -24% | -27% | -50% |
Emission Limits for 2020, 2025 and 2030
Regulation 4 of the Limitation of Emissions of Certain Atmospheric Pollutants Regulations, (S.L. 549.124), obliges ERA to publish on its website the emission limits in tonnes equivalent to the respective emission reductions in sub-regulations 2, 3 and 4 of regulation 4, see the tables below:
Table 1: Emission Limits to be complied with by 2020
| Pollutant | Emission Reductions in Article 4(2), SL 549.124 | Emission Levels in 2005 | 2020 Emission Limits |
|---|---|---|---|
| (%) | (tonnes) | (tonnes) | |
| SO2 | 77 | 12116 | 2787 |
| NOx | 42 | 9830 | 5701 |
| NMVOC | 23 | 3234 | 2490 |
| NH3 | 4 | 1881 | 1805 |
| PM2.5 | 25 | 829 | 622 |
Table 2: Indicative Emission Limits to be achieved by 2025
| Pollutant | Emission Reductions in Article 4(3), SL 549.124 | Emission Levels in 2005 | 2025 Emission Limits |
|---|---|---|---|
| (%) | (tonnes) | (tonnes) |
|
| SO2 | 86 | 12116 | 1696 |
| NOx | 60 | 9830 | 3883 |
| NMVOC | 25 | 3234 | 2426 |
| NH3 | 14 | 1881 | 1617 |
| PM2.5 | 38 | 829 | 518 |
Table 3: Emission Limits to be complied with by 2030
| Pollutant | Emission Reductions in Article 4(4), SL 549.124 | Emission Levels in 2005 | 2030 Emission Limits |
|---|---|---|---|
| (%) | (tonnes) | (tonnes) | |
| SO2 | 95 | 12116 | 606 |
| NOx | 79 | 9830 | 2064 |
| NMVOC | 27 | 3234 | 2361 |
| NH3 | 24 | 1881 | 1429 |
| PM2.5 | 50 | 829 | 415 |
Compliance with these ceilings is assessed through the Atmospheric Emissions Inventory (prepared by the Member States every year) and the projections (prepared by the Member States every two years), which are accompanied by the Informative Inventory Report on an annual basis. The time series for the emission of atmospheric pollutants by the EU Member States can be viewed on this webpage. In addition, ERA reports the spatially disaggregated national emission inventories and large point source inventories, as required under the NEC Directive.
The National Air Pollution Control Programme for Malta outlines the measures selected for adoption in the coming years with a view to meet the above-mentioned emission reduction commitments.
The NEC Directive also requires monitoring of the impacts of air pollution upon ecosystems. To assess such impact, the network of the monitoring sites and the associated indicators used for monitoring air pollution is first designated, followed by the reporting of the monitoring of air pollution impacts.
Multilateral Environmental Agreements
The NEC Directive implements the European Union’s obligations under a multilateral environment agreement known as the Convention on Long-Range Transboundary Air Pollution. The main aim of this agreement is to combat acidification, eutrophication and ground-level ozone as well as, to limit and, as far as possible, gradually reduce and prevent air pollution including long-range trans-boundary air pollution.
Sources
According to the European Environment Agency the major contributors to air pollution in Europe are:
- Power generation [SO2 and NOX];
- Transport [NOX, CO, PM2.5, and PM10]; and
- Agriculture [NH3].
However in Malta, road transport is the major contributor to air pollution in urban areas. High levels of particulate matter (PM10 and PM2.5) and of nitrogen oxides (NOX) are normally associated with areas exposed to heavy traffic flows. In rural areas, away from anthropogenic sources, levels of ozone (O3) are the chief air quality concern.
As far as the regulated air pollutants are concerned the following are considered to be the major sources:
Pollutant Source(s)
Particulate Matter Fuel Combustion in Power Generation.
Fuel Combustion in Road Transport
Incineration
Tyre and brake wear
Road wear
Ozone Is not emitted directly but results from reactions involving precursor gases such as volatile organic compounds and nitrogen oxides.
Nitrogen Oxides (NO and NO2) Combustion Sources (results in NO mostly, which is subsequently oxidized to NO2).
Sulphur Dioxide (SO2) Combustion of fuels containing high levels of sulphur (e.g. Heavy Fuel Oil in thermal power plants).
Benzo[a-]pyrene Incomplete combustion of fuels in road transport and rubber-tyre wear.
Carbon monoxide Incomplete combustion of fuels in road transport.
Benzene Incomplete combustion of fuel in road transport.
Handling and distribution of petrol.
Arsenic Metal smelters.
Coal combustion.
Cadmium Non-ferrous metal production.
Iron and steel production
Cement production.
Waste Incineration.
Stationary combustion of fossil fuel.
Nickel Combustion of fuel oil and coal in stationary plants.
Combustion of fuel in ships.
Waste Incineration.
Steel manufacture.
Electroplating.
Lead Combustion of fossil fuel.
Waste incineration.
Production of non-ferrous metals.
Production of iron and steel.
Production of cement.
Mercury Combustion of coal.
Effects
According to the WHO, cardiovascular disease is the most common reason for premature death as a result of poor air quality; lung diseases (including lung cancer) follow. Air pollution is not only the cause of premature mortality, but is also known to increase the incidence of various diseases.
The diagram below summarises the major health effects of air pollution. A more detailed description on the health effects of particulate matter, nitrogen dioxide, sulphur dioxide and ozone can be obtained from the following document.
The real time air quality monitoring network is complemented by a passive diffusive tube network. The Environment and Resources Authority (ERA) has deployed 100 NO2 tubes and 100 volatile organic compounds (VOC) tubes throughout Malta and Gozo. The tubes are exposed for a period of 4 weeks (for a total of 13 exposure periods in one year) after which they are sent to a laboratory for analysis. The annual averages can then be interpolated to provide pollution maps as follows:
