PM₂.₅ sources in Skopje
What’s actually in Skopje’s fine particle air?
Most fine particle pollution (PM₂.₅) in Skopje comes from residential solid-fuel heating, especially in winter, with road traffic as the second key source. Dust, industrial fuel-oil combustion, open burning and secondary particles formed in the atmosphere each add smaller but important shares.
Dominant source
≈ 1/3 of PM₂.₅
Biomass / residential heating annually at the urban background station.
Winter peak
50–60%
Wood / coal heating in some winter months at Karpoš.
Traffic share
≈ 18–23%
Annual PM₂.₅ share from traffic at background vs roadside stations.
Dust & secondary
~25–30%
Combined dust and secondary aerosols across the year, depending on site.
Table notes / legend
PM = particulate matter; PM₂.₅ and PM₁₀ refer to particles ≤2.5µm and ≤10µm. NO₂ = nitrogen dioxide; O₃ = ozone; SO₂ = sulfur dioxide; EC = elemental (black) carbon.
UGD = University “Goce Delčev” Штип. IPH = Institute of Public Health. MASA = Macedonian Academy of Sciences and Arts. MoEPP = Ministry of Environment and Physical Planning.
City-wide picture
What drives PM₂.₅ in Skopje?
Across all studies, the story is consistent: solid-fuel heating dominates, traffic comes second, and everything else layers on top.
Heating as the main source
Residential solid-fuel heating (wood, coal, mixed fuels) is the single largest source of fine particles in Skopje – about one-third of annual PM₂.₅ and up to 50–60% in winter months at the background site.
Traffic as #2
Road traffic (exhaust, brake and tyre wear, resuspended road dust) adds roughly one-fifth of PM₂.₅ at key urban locations, with higher shares near busy roads.
Other layers
Soil and road dust, fuel-oil / industrial combustion, open burning and secondary particles each contribute smaller but important shares (typically 5–15% depending on station and season).
Same mix across the valley
All five receptor sites in the Skopje valley show the same basic source mix: heating + traffic + dust + secondary aerosols, with some areas getting extra traffic, industry or open burning on top.
Source groups
The main PM₂.₅ sources
Biomass / residential heating
Wood, coal and mixed fuels burned in household stoves and boilers. Dominant annual source and main driver of winter peaks.
Traffic
Vehicle exhaust, brake and tyre wear, and traffic-related dust. More important at roadside and commuter corridors.
Dust / soil
Resuspended road dust and soil, especially in dry periods and summer months with little rain.
Industry / fuel oil
Heavy fuel oil and industrial combustion, identified by metals like vanadium and nickel in filters.
Open burning / waste
Burning of agricultural residues and mixed waste, with spikes in spring and early summer.
Secondary particles
Sulfate and nitrate particles formed in the atmosphere from SO₂ and NOx, often regionally transported.
De-icing salt
Road salt and related material used in winter, visible as sodium and chloride peaks on filters.
Other / uncertainty
Remaining small sources and model uncertainty after the main factors are accounted for in PM₂.₅ mass.
Source mix
Annual PM₂.₅ source mix by station
Approximate annual shares from the UGD/UNDP source-apportionment study (PMF) at five sites in the Skopje valley. Values are rounded and grouped into the same source categories as above.
Bars show approximate annual % by source group. “Other” captures remaining small contributions and model uncertainty.
What this means in practice
Karpoš represents an “average city” background. Novo Lisiče is a roadside hot spot where traffic and fuel-oil shares are higher. Gazi Baba and Hrom combine industry and housing, while Volkovo shows more dust and open burning from the rural edge. In all cases, biomass burning is the largest slice.
Monitoring network
Stations and what they represent
These stations appear across the source-apportionment study and the Air Quality Plan. Together they define how we talk about “city”, “neighbourhood” and “background” air in Skopje.
Karpoš
Urban background
Represents an “average city” environment away from direct industrial stacks or the busiest roads. Main reference site for detailed PM₂.₅ source analysis.
Novo Lisiče (Lisiče)
Urban traffic / residential
Near busy roads and dense housing. Often records some of the highest PM levels, with a stronger signal from traffic, fuel oil and open burning on top of heavy heating.
Gazi Baba (Avtokomanda / Železara)
Industrial / residential
Mixed residential and industrial area downwind of major facilities and road links. Used to see how industry, heating and traffic combine here.
Gjorče Petrov – Hrom
Residential + local industry
Western edge of Skopje with household solid-fuel heating and local industrial activity. Captures neighbourhood-level impacts of heating plus nearby plants.
Gjorče Petrov – Volkovo
Peri-urban / rural edge
Transitional zone with fields, scattered housing and open land. Important for understanding dust, open burning and inflow of pollution into the valley.
Centar
Central urban, traffic-influenced
Near the city centre. Shows how denser central areas compare with more exposed outskirts, with lower heating signal but clear traffic influence.
Rektorat (Rectorate)
Urban background / university
Campus-adjacent station capturing a mix of background city air and nearby traffic.
Miladinovci
Suburban / rural background
East of Skopje. Tracks regional background and refinery / industrial influence outside the dense urban core.
Lazaropole
Remote regional background
High-altitude station used to characterise regional background air in North Macedonia; not in the Skopje valley but useful for comparison.
Full-year PM₂.₅ source percentages are only available for Karpoš and Novo Lisiče. Gazi Baba, Hrom and Volkovo have shorter campaigns mainly used to check whether the source mix is similar across the valley. The Air Quality Plan and health studies usually aggregate all Skopje urban stations to describe city-wide concentrations.
Seasonal story
Winter vs summer: how the recipe changes
PMF results show a sharp seasonal shift: heating + secondary nitrate in winter, dust + traffic in dry summer months.
Approximate contribution shares based mainly on the Karpoš background site. Winter values include a strong secondary nitrate and de-icing salt signal; summer values show dust and traffic domination.
Neighbourhood differences
Same main mix across Skopje, local twists by area
The source apportionment shows that all five main study sites share the same basic set of sources: biomass, traffic, dust, fuel oil, open burning, secondary aerosols and road salt. Each area has its own emphasis.
Karpoš
“Cleaner” background
Less direct traffic and industrial impact; strong biomass and dust with relatively lower fuel-oil share. Used as the main reference background site.
Novo Lisiče
Roadside hot spot
Higher shares of traffic, fuel-oil combustion and open burning on top of strong biomass. Busy residential and commuter corridor with frequent peaks.
Gazi Baba / Železara
Industry + housing
Strong influence of industrial and combined sources together with household heating, reflecting its mixed residential–industrial character.
Gjorče Petrov – Hrom
Local industry + heating
Western neighbourhood where local industry and solid-fuel heating combine, producing clear winter peaks and notable metal signatures in the filters.
Gjorče Petrov – Volkovo
Dust + open burning
Stronger influence of dust and open burning from surrounding fields and the rural edge, on top of the common Skopje heating and traffic background.
Across Skopje, biomass burning dominates PM₂.₅ everywhere. These local differences show where traffic, industry or open fires add extra layers on top of the valley-wide background.
Behind the charts
How the source study was done – and its limits
Short version for humans, with expandable sections if you want the nerdy details.
How the PM₂.₅ source study works
- Researchers collected 24-hour PM₂.₅ samples on filters at five sites in the Skopje valley over about one year.
- Each filter was analysed for metals, major ions and different forms of carbon in the laboratory.
- A statistical method called Positive Matrix Factorisation (PMF) grouped chemicals that rise and fall together into factors matching wood smoke, traffic, dust, fuel oil, open burning, secondary aerosols and road salt.
- The model then estimated how much each factor contributed to the measured PM₂.₅ mass at each station and in each month.
Key limitations to keep in mind
- Only Karpoš and Novo Lisiče have full-year chemical data; Gazi Baba, Hrom and Volkovo are shorter campaigns, so annual percentages there are less robust.
- PMF cannot perfectly separate overlapping sources (for example exhaust vs road dust), so some dust and traffic signal is merged, especially at Novo Lisiče.
- Regional transport shows up mainly as secondary sulfate and nitrate factors – the model does not identify individual stacks outside Skopje.
- Results reflect one specific study year. The exact numbers may change, but the overall structure (heating > traffic > others) is expected to hold.
How scientists recognise each source in the lab
Each factor has its own “fingerprint” – typical combinations of chemical species:
- Biomass burning: high potassium (K), chloride (Cl), nitrate, organic and elemental carbon.
- Traffic: elemental carbon, copper, zinc, iron and barium from brake and tyre wear.
- Soil / dust: aluminium, silicon, calcium, iron and titanium.
- Fuel / residual oil: vanadium and nickel plus sulfur, pointing to heavy fuel oil combustion.
- Open fire burning: EC/OC, K, Cl plus metals like Cu, Zn, Pb, As from burning mixed waste.
- Secondary sulfate / nitrate: sulfate, nitrate and ammonium formed in the atmosphere from regional SO₂ and NOx.
- De-icing salt: very strong sodium and chloride, sometimes calcium and magnesium, peaking in winter along roads.
Health context
How bad are the levels for people?
Health-focused research using Skopje’s monitoring data finds that annual PM₁₀ and PM₂.₅ concentrations are roughly two to three times higher than current EU annual limit values and WHO guideline levels. These elevated levels are linked to significant premature mortality and hospital admissions, compared with a scenario where air quality meets guideline values.
The health studies group the main sources of outdoor air pollution as solid-fuel household heating, industrial facilities and traffic – the same mix shown in the source diagrams on this page.
Where this page comes from