Chapter 15. Monitoring of Air Pollution

Table of Contents

15.1. Measurement locations
15.1.1. Classification of measurement sites
15.1.2. Measurement network in Europe and Hungary
15.2. Measurement techniques
15.2.1. Sampling methods
15.2.2. Measurement of gas concentrations
15.2.3. Measurement of aerosol concentrations
15.2.4. Remote sensing
15.2.5. Rainwater analysis
15.3. Conclusion

Atmospheric environmental protection, including air quality management, response scenarios, health effect and risk estimates as well as atmospheric dispersion modeling would be impossible without the quantitative description of air quality with representative and measurable quantities. Air pollution is a complex process with numerous materials that have very different atmospheric lifetime, environmental and/or health effect; therefore air quality description could not be carried out using one simple quantity. In fact, the correct measurement method and location depends largely on the material and also on the aim of the study. In this chapter, we give an overview of the most common measurement techniques for the typical requirements of scientific and authoritative air quality management.

15.1. Measurement locations

15.1.1. Classification of measurement sites

Air pollution involves emission (release), transmission (dispersion) and immission (deposition/reaction) processes (see Chapter 2), which have to be treated and measured separately.

Emission processes can be categorized as anthropogenic and natural emissions. In many countries, industrial organizations are obliged to perform on-release measurement of their emission, which led to large public databases of emission data from certain facilities (see e.g. http://edgar.jrc.ec.europa.eu). However, a large part of anthropogenic emission is not measured directly; such as pollution from traffic, households/heating and agriculture. The effect of these sources are estimated through sample data measured at selected representative points, such as a traffic emission measurement site near a busy road or a micrometeorological station on an agricultural field. Based on these datasets, the magnitude and the temporal and spatial variability of the emission can be estimated.

Natural sources of pollutants are hard to measure because of their large spatial extent and complexity. There are measurement sites to sample emission data from representative points, which, together with the long-term concentration time series of worldwide stations can be used to obtain global- and regional-averaged net emission data of natural sources/receptors.

The optimal measurement location depends largely on the atmospheric lifetime and environmental impact of the material. Materials with long (1–120 years) lifetime are well mixed throughout the atmosphere, thus their annual average concentration can be regarded as spatially constant except in the vicinity of their source regions. This approach is valid for most of the greenhouse gases, like CO2 and N2O, which affect environment globally. It means that we require measurements that are representative for the large-scale concentration field, which is not the case close to the source regions. Thus greenhouse gases are measured in background (i.e. far from significant release points) sites.

The most representative greenhouse gas concentration time series have been measured at locations far from any human activities, like the Mauna Loa Observatory in Hawaii or the Amundsen–Scott Station in the Antarctic (Figure. 15.1). These and other global background measurement sites provide valuable information of the average concentrations, while regional background measurements in rural areas are used to estimate regional variability and transport processes (Table 15.1).

Global background measurement sites

Figure 15.1: Global background measurement sites of the WMO GAW (World Meteorological Organization – Global Atmosphere Watch) project

Table 15.1: Categorization of surface air quality measurement sites

Measurement site

Location

Aim of measurement

Measured quantities

Example

Global background

Far from any human activities

Greenhouse gas global average concentrations

Long-term average concentrations

Mauna Loa Observatory, Hawaii

Regional background / regional emission

Agricultural and rural areas

Greenhouse gas regional average concentrations, regional transport

Long-term average concentrations, fluxes

Hegyhátsál, Hungary

Toxic/irritating material average deposition, regional transport

Sample data to estimate large-scale emission

Residential background

Suburbs, residential areas

Toxic/irritating material concentrations, health effects

High temporal resolution concentrations

Gilice tér, Budapest

Urban emission

Busy roads, industrial areas

Emission estimation, local scale health effects

High temporal resolution concentrations

Kosztolányi Dezső tér, Budapest

In-situ emission

Release points (stacks)

Accurate emission data to fulfill law obligations

Released mass of pollutant

Paks Nuclear Power Plant, Hungary

Air pollutants with short lifetime have several effects on local or regional scale. Their concentrations can vary with magnitudes between source and background locations, both of which are important to estimate. While close to the source, high concentrations have a significant impact on health and environment (e.g. in an urban area), further distances can suffer long-term effects through deposition. Therefore within a local environment such as a residential area (often referred to as residential background sites), concentration measurement with high temporal and spatial resolution is required. Meanwhile in rural areas, long-term average concentrations and calculated or directly measured depositions are important (Table 15.2).

Table 15.2: Categorization of surface air quality measurement sites for environmental / health effect estimation

Typical pollutants

Atmospheric lifetime

Scale of impact

Representative quantity

Measurement location

Greenhouse gases

CO2, N2O, CH4

> 1 year

Global

Concentration

Global background

Toxic / irritating air pollutants

NOx, O3, SO2

< 1 month

100 – 1000 km

Deposition

Regional background

0 – 100 km

Concentration

Residential background

While surface measurements are representative for a given location, and provide wealthy information about air quality of different regions, more accurate large scale simulations of transport-exchange processes require concentration data on a much finer grid. Remote sensing techniques, especially satellite observations have become a uniquely efficient tool of large scale air quality measurement, and are able to measure vertically integrated total pollutant mass as well as vertical concentration profile for any location with a fine spatial and temporal resolution.

15.1.2. Measurement network in Europe and Hungary

The European Monitoring and Evaluation Programme (EMEP) was funded in 1979 to organize an international co-operation in order to provide public large scale emission and immission data and solve transboundary air pollution problems (http://www.emep.int). EMEP consists of five suborganizations:

  • Centre on Emission Inventories and Projections (CEIP), Vienna, Austria

  • Chemical Coordinating Centre (CCC), Kjeller, Norway

  • Meteorological Synthesizing Centre – West (MSC-W), Oslo, Norway

  • Meteorological Synthesizing Centre – East (MSC-E), Moscow, Russia

  • Centre for Integrated Assessment Modelling (CIAM), Vienna, Austria

CEIP maintains an emission inventory of the most important air pollutants (CO, NH3, VOC, NOx, SO2, PMs, heavy metals and POPs) on a 0.1 degree resolution grid based on emission reports of member countries. The detailed and long-term time series of emission data is publicly available from CEIP’s website (http://www.ceip.at/) and is widely used in air quality studies of different European regions.

While CEIP holds the emission database, CCC is responsible for immission measurement. EMEP measurement network consists of hundreds of regional background monitoring and/or precipitation analyzer sites. These sites perform a measurement programme defined by EMEP guidelines to provide reliable and comparable results for the whole continent. The measurements mostly focus on acidic components and ozone, but heavy metals and PMs are also measured at numerous sites. Both the archive and actual database of European air quality are available from the CCC website (http://www.nilu.no/projects/ccc/index.html). In Hungary, the K-Puszta station in the Kiskunság region is part of the EMEP monitoring network.

The two MSC centers are responsible for high quality atmospheric dispersion modeling and software development. MSC’s Eulerian dispersion model provides reliable analyses fields and forecasts of the continent’s air quality as well as a mapping of source-receptor relationships to point out the contribution of each country to the total transboundary air pollution. The model uses CEIP and CCC measurements as input data. Besides the dispersion model’s results, its source code is also freely available.

CIAM focuses on climate change and air pollution relationships, with an attached treatment of greenhouse gas and pollutant emission. Based on the more decades long EMEP time series, CIAM provides emission projections, dispersion and health effect modeling using attached multidisciplinary simulation performed by the GAINS model.

In Hungary, air quality measurement sites are operated by the Hungarian Meteorological Service (OMSZ) and the Ministry of Rural Development’s Air Quality Network (OLM). Five regional background stations (Fig. 15.2) are maintained by the Hungarian Meteorological Service to measure concentrations and soil-atmosphere fluxes of acidic components, ozone, VOC and greenhouse gases. In addition, a precipitation analyzer station is located in Siófok.

Two additional regional background stations in Kisszentmárton and Sarród are operated by OLM to estimate pollution suffered by environmental protection areas. However, OLM mostly focuses on urban air quality monitoring, and its measurement sites are present in almost all larger towns of the country, including both residential background and urban emission sites (Fig. 15.3–15.4).

Figure 15.2: Regional background measurement sites in Hungary operated by the Hungarian Meteorological Service (red) and the Hungarian Air Quality Network (green)

Urban measurement sites

Figure 15.3: Urban measurement sites operated by the Hungarian Air Quality Network (OLM)

Urban background measurement site

Figure 15.4: Urban background measurement site in Budapest, Hungary (source: Hungarian Air Quality Network).