Main Sources of PM2.5 Pollution in Almaty

Analysis of an Academic Article Using PMF and HYSPLIT Methods

Research Objective

The study addresses the question of which types of sources contribute to PM2.5 concentrations in Almaty and their relative contribution to pollution. It is one of the first studies in Almaty to use PMF to determine the source contribution distributions based on the chemical composition of PM2.5.

Methodology

Input data and study period. The study used a year-long series of PM2.5 samples collected from August 2022 to July 2023, with chemical analysis.

Location. Sampling was conducted at a single site in Almaty (the KazNU campus).

Source apportionment. The main method was Positive Matrix Factorization (PMF), which identified five source factors.

Assessment of the spatial context. HYSPLIT was used to assess the role of particle transport by calculating 72-hour backward trajectories of air masses. The Conditional Probability Function (CPF) was also used to relate source contributions to wind direction and speed.

Main finding: five PM2.5 sources and their contributions in Almaty

The PMF analysis produced the following distribution of contributions to PM2.5 in Almaty:

1) Urban road dust (32%)

This source is associated with elevated concentrations of elements linked to brake, tire and road surface wear. These particles originate from the city’s two major highways: Al-Farabi Avenue and the Eastern Bypass Road. Almaty is characterized by slow-moving air masses, indicating the importance of road dust resuspension under conditions of weak winds and limited dispersion.

2) Urban atmosphere (20%)

The urban atmosphere factor is characterized as mixed background pollution, comprising industrial and combustion emissions, as well as the accumulation of pollutants under unfavorable ventilation conditions. Its chemical profile shows evidence of multiple source types mixing, including combinations of different elements and markers.
The accumulation of particles attributed to this factor is explained by Almaty’s geography, which limits vertical and horizontal dispersion, and by the contribution of secondary aerosols.

3) CHP plants and boiler houses (18%)

The CHP plant factor is supported by the characteristics of local coal ash and the typical elemental composition associated with high-temperature coal combustion. The analysis indicates probable source directions, which the authors associate with the locations of major heat supply facilities, including CHP-2 and CHP-3.

4) Residential heating (16%)

The residential heating factor includes markers associated with solid fuel combustion, transboundary emissions and the secondary formation of fine particles, as well as evidence of biomass burning and possible waste burning.
For context, the authors provide an estimate of household fuel use in Almaty, noting that gas is the predominant primary fuel. However, even a small proportion of households using solid fuels may have a significant impact when dispersion is poor during the cold season.
The possible influence of particle transport and aged air masses is also noted and supported by trajectory analysis.

5) Vehicle exhaust (14%)

This factor is characterized by elements typical of traffic-related impacts, together with elements consistent with the use of deicing materials in winter.
In their analysis, the authors associate the probable directions of these particles with areas of heavy traffic near major highways.

The Urban atmosphere and Residential heating factors contain characteristic markers of coal and biomass combustion, while the CHP plant contribution shows evidence of high-temperature coal combustion, consistent with the findings of a similar analysis for Dushanbe.

Study Limitations

1. Spatial representativeness. The results were obtained at a single sampling site. The authors state that the findings reflect urban trends, but interpretation must account for the local nature of the observations and the possibility that source contributions vary across city districts.
2. Uncertainty in the CPF analysis. Spatial uncertainty may arise because the sampling site and the location of the meteorological data used for wind analysis do not coincide.

Implications for urban policy and recommendations for effective air quality management

1) CHP plants and major heat sources

• Reducing CHP plant emissions by switching to natural gas should be prioritized. This is considered a key direction because it reduces emissions and improves heat supply efficiency, but requires infrastructure incentives and the development of public–private partnership mechanisms.
• Emission control technologies must be introduced, such as fabric filters, electrostatic precipitators, and wet desulfurization units. Currently, modern emission control methods are not being used.
• The limitations of these solutions must be considered: high installation and maintenance costs, space requirements and technical operating conditions, which are particularly critical for aging equipment.
• CHP plant modernization is identified as an urgent priority, with an emphasis on commissioning new gas-fired capacity and upgrading existing units. The EU case shows reductions of 92% in SO2 emissions, 90% in PM emissions and 70% in NOx emissions.

2) Coal and biomass combustion in the residential sector

• Coal and biomass combustion in the residential sector is also identified as a top priority. International experience shows that restrictions on solid fuel combustion can significantly improve air quality.
• The main barriers are the availability of alternatives, public acceptance of the measures and low awareness of the risks, making a comprehensive package of measures necessary.
• The core measures include banning solid fuel sales, promoting cleaner fuels, providing financial support to households and systematically informing the public.
• The role of housing energy efficiency measures is emphasized, including low-cost solutions to reduce heat loss, as these reduce fuel demand and facilitate the transition to cleaner sources.
• The potential for reducing PM2.5 emissions by phasing out coal in Kazakhstan’s residential sector is 92%.
• Switching households from solid fuels to cleaner alternatives generally requires active government involvement, including subsidies and the removal of infrastructure constraints.

3) Transport and vehicle fleet emissions

• Reducing transport emissions requires the simultaneous development of public transport infrastructure, stronger enforcement of vehicle inspections and the creation of a convenient pedestrian environment.
• Reallocating street space in favor of public transport and supporting micromobility reduce air pollution.
• Transparent and regular vehicle inspections, together with differentiated charges, encourage the use of cleaner vehicles and proper maintenance, thereby reducing pollution by 12–13% in the EU.

4) Air quality management

• In the absence of annual pollutant standards, achievable interim annual PM2.5 targets are proposed: 25 µg/m³ for Almaty.
• These targets could be established as Environmental Quality Standards through amendments to the Environmental Code, with subsequent revision as emission control technologies improve and monitoring data accumulate.
• For major Category I sources, including CHP plants, it is essential to strengthen enforcement, apply best available techniques (BAT) and introduce payments and fees that encourage emission reductions.
• A major limitation of the current system is insufficient monitoring infrastructure. Without it, source identification, forecasting, early warning, emission inventory development and assessment of the effectiveness of measures are difficult.
• A comprehensive strategy should include regular communication of health risks, standardized alert protocols and transparent communication during periods of elevated pollution.

Key conclusions

• PM2.5 in Almaty originates from several major sources simultaneously. The PMF analysis identified five factors that account for the main contributions to particle concentrations.
• The largest contribution comes from urban road dust (32%), highlighting the importance of dust resuspension and road-related processes alongside fuel-related sources.
• A substantial share comes from coal combustion at CHP plants and in the residential sector: CHP plants and boiler houses account for an estimated 18%, and residential heating for 16%. Meanwhile, the chemical profile of the urban atmosphere factor (20%) clearly contains coal and biomass markers.
• The urban atmosphere factor (20%) reflects the accumulation and mixing of pollutants, explained by limited dispersion due to geography and meteorological conditions, as well as the contribution of secondary aerosols.
• The directions from which vehicle exhaust emissions (14%) arrive are associated with areas of heavy traffic and proximity to major highways.
• Seasonality in Almaty is driven not only by increased emissions but also by poor dispersion, so even sources with relatively small shares may have a noticeable impact during periods of unfavorable ventilation.
• The authors’ recommendations focus on four main areas of management: accelerated CHP plant modernization and conversion to gas; a package of residential heating measures with social support; public transport and vehicle inspection measures; and formalized targets supported by stronger monitoring and enforcement.