97. Determination of CO and CO2, SO2 and NO2 in air samples.

7+8) Determination of CO and CO₂ in air sample, Determination of SO₂ and NOₓ in air samples, determination of lead aerosols and dust in air sample

CARBON DIOXIDE

• -carbon dioxide is a natural constituent of the air concentration (0,03-0,04 vol.%)
• -is generated normally in combustion, using coal, gas or oil, by rot and by breath
• -0,07-0,1 vol.% is the critical value (maximum permissible value – MPV)
• -> it’s determined with barium alkali: CO₂ is combined with solution of barium (Ba(OH)₂) and BaCO₂ is formed->volume of CO₂ is determined by the change of titer of Ba(OH)₂

CARBON MONOOXIDE

• -colorless and tasteless gas which is produced in incomplete combustion of fuel
• -has an affinity to Hb 200-300 times higher than oxygen -> easy formed carbhemoglobin
• -maximal permissible concentration (MPC) is 10 mg/m³ for 8h
• -> working environment maximal concentration: 200 mg/m³
• ->it’s determined based on color reaction with I₂O₅ (direct reading colorimetric, color change from white/colorless to brown/yellow in glass tube)
• -collection: air is aspirated with hand pump (around 10 to 20 samples)

SULFUR OXIDE

• -major source of pollution for many cities, SULFUR (non-metallic) is found in nature either free or combined with other elements -> as impurity in coal and fuel oil
• -when sulfur containing fuels are burned, sulfur joins the oxygen -> sulfur oxides
• -sulfur dioxide (SO₂) combustion -> combination with water vapor -> sulfurous acid (H₂SO₃) -> joins the oxygen in the air -> sulfuric acid (H₂SO₄)
• -sulfur dioxide reacts also with oxygen to form sulfur trioxide (SO₃) -> slow process -> but it builds up substantially -> quick reaction with water vapor to form sulfuric acid
• -determination of SO₂: nephelometer measure the turbidity of liquids -> absorbed into potassium chlorate (liquid) -> 10ml in a test tube -> add 1 ml of HCl -> add 1 ml of BaCl₂ -> comparison of the turbidity on standard scale
• -> calculation: SO₂ (in mg/m³) = M*C/V₀*A
• -where C=quantity of SO₂ by scale; A=analyzed part of sample; M=whole volume of sample; V₀= adapted standard conditions volume of air sample

NITROGEN OXIDES

• -colorless, tasteless and odorless gas -> combines with oxygen to from oxides
• -nitric oxide (N_O) -> formed in cylinders of cars (largest source of nitric oxide), electric power plants…
• -nitrogen oxide (NO₂) -> formed by photochemical actions (industries with explosive manufacturing) -> can react with raindrops of water vapor to produce acid (HNO₃) -> acid rain (respiratory disease, vegetation injury, corrode metal surface)