HSC CHEMISTRY 2015​.

Evidence of Anthropogenic Sources

 

SO2 & NOx in Industrial Areas

SO2 emissions first started to increase following the Industrial Revolution in the early 1800’s, when large amounts of coal was burnt to power factories and machinery. However after a series of nasty pollution episodes in the 1950’s around London and the North-East US causing many deaths (approx. 4000), regulations were introduced to control the amount of emissions produced by factories, dramatically improving air quatility.

 

NOx emissions did not increase until the 20th Century due to the increase in electricity generation and motor car use. Increasing NOx emissions, in conjunction sunlight lead to a problem with photochemical smog in 1960’s (in Los Angeles and other sunny cities).This lead to NOx emission regulations, mainly on motor cars, resulting in improved air quality over the following two decades.

 

Reducing Emissions:

Reduce coal burning: personally reducing our electricity use through using energy-efficient appliances.

 

Burning low-sulfur coal: companies switching the coal they burn or using natural gas which produces much less SO2.

 

Reduce Fossil Fuel Reliance: Using other (renewable) forms of power such as hydroelectricity, wind power or solar power.

 

Collecting SO2: SO2 from smelting metal sulfides can be collected from flumes and used in sulfuric acid production:

 

Reduce acidic emissions through “scrubbing”: Acidic gasses are passed through a base slurry (such calcium oxide) before going out smoke stacks. The SO2 reacts with the calcium oxide forming solid calcium sulfite.

 

Pass car exhaust through catalytic converters: The catalytic converter converts NOx’s back to N2.

 

Despite emission regulations SO2 and NOx continue to increase in urban areas due to increasing populations & increasing vehicle use and km’s drive.

Recent effects of acid rain on industrial centres are considered evidence of increased SO2 and NOx in the atmosphere as Acid Rain is caused by high amounts of the gasses in the air.

 

Global SO2 & NOx

CO2 concentrations over 150 yrs

Studies of the atmospheric gasses trapped in Ice core samples taken from Antarctica and Carbon isotopes ratios in fossils have shown an increase of Carbon Dioxide concentrations of approximately 99ppm over the last 150 years.

280ppm before industrialisation to approximately 379ppm at present.

 

SO2 & NOx concentrations over 150 yrs

Due to a lack of reliable data from periods before the 1950 it is difficult to be sure of SO2 and NOx. However there is some evidence.

• Ice Core samples have shown a 10% increase in Dinitrogen monoxide (N2O) concentrations

• Damage to buildings, forests and aquatic organisms is increasing; due to acid rain, thus signifying increases in SO2 and NOx atmospheric concentrations

• Ozone Measuring Instrument (OMI), orbiting the earth aboard a NASSA satellite measuring air components such as NO2, SO2 and more.

 

Measuring SO2 & NOx

Obtaining evidence of SO2 & NOx changes is much more difficult than that of CO2 due to:

• Solubility in Water: The sulfate and nitrate ions formed by SO2 & NOx are mostly soluble in water, unlike carbonate ions. These ions are not precipitated out and remain in the biosphere and hydrosphere. Thus measurements are less valid as large amounts of the gasses are dissolved.

• Smaller Concentrations: At present SO2 & NOx exist in much smaller concentrations (≈0.001ppm) as opposed to CO2 (≈380ppm)

• Instrumentation: Before the 1970’s instruments able to measure such small concentrations were not available, limiting our reliable data to only 40 years.

 

 

 

 

Anthropogenic Changes

Fluctuations in concentrations of SO2 & NOx over time and area are strong evidence that there has been and anthropogenic increase. This evidence includes:

• Correspondence of the first signs of SO2 increase and the industrial revolution in the 1800’s. The excess burning of coal can be attributed to SO2 emissions

• Followed by a decrease of SO2 emissions after regulations of emission controls were introduced in the 1950’s

• The first major NOx increase corresponded with an increase in electricity production and motor fuel use, which was addressed with emission controls on motor cars followed by improved air quality.

• The effects of acid rain (damage to plants, aquatic organisms, buildings and soils) is more prominent in industrial areas, where SO2 & NOx emissions are high, than that of unindustrialised areas.

• Similarly measurements of SO2 & NOx concentrations are commonly higher in industrial areas.

• OMI measuring a decrease in NO2 pollution despite a growing population of cars on roads, due to regulations and technological developments

 

 

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These correlations provide strong evidence that changes in Sulfur and Nitrogen oxides compositions has been largely triggered by humans. However this is not to say that all changes are due to human activity. There are many natural sources of Sulfur and Nitrogen oxides including:

• Bushfires

• Volcanoes

• Lightening

• Soil bacteria

Despite this the high concentrations of the gasses in industrial areas teamed with the correlations of industrialisation and extended SO2 & NOx increase shows that increases are majorly anthropogenic.

 

References:

Figure 6)

NASA Goddard's Scientific Visualization Studio/T. Schindler, (2011), Before and After Images [ONLINE]. Available

at: http://www.nasa.gov/content/goddard/new-nasa-images-highlight-us-air-quality-improvement/#.VPepcvmUewl [Accessed 05 March 15].