Acid+Deposition

(Standard/Higher Level) Mabbel Tan
 * Acid Deposition **

2.1 State what is meant by the term acid deposition and outline its origins. 2.2 Discuss the environmental effects of acid deposition and possible methods to counteract them.
 * ! Before we start, let's look at the two learning outcomes: **

- It refers to the process by which acidic particles, gases (dry deposition) and precipitation (wet deposition) leave the atmosphere.
 * 2.1 What is Acid Deposition? **

It is not a recent phenomenon and has been observed since the 17th century. Scientists started to notice the severe impacts that industries and acidic pollution have on natual vegatation and people.

** Sources of Acid Deposition **

The whole process starts from the power generating plants and other industrial plants which produce huge amounts of sulfur dioxide (SO2 ), nitrogen oxides (NOx ) and particulate matters. The wind and other weather patterns transport these pollutants which eventually form secondary pollutants: nitrogen dioxide (NO2 ), nitric acid (HNO3 ) and sulfuric acid (H2 SO4 ).

However, acid deposition can also form naturally from volcanoes, sea spray, plankton, rotting vegetation and sour natural gas. The equation for natural formation is given by: 2H2 S(g) + 3O2 (g) → 2SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 (g) + 2H<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 O(l)

The particulate matter that is produced as a by-product of coal burning acts as a heterogeneous catalyst for the direct reaction of SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 to SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 which reacts with moisture to produce sulfuric acid: <span style="font-family: Arial,Helvetica,sans-serif;">2SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + O <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) → 2SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 <span style="font-family: Arial,Helvetica,sans-serif;">(g)SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">O(l) → H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">4 <span style="font-family: Arial,Helvetica,sans-serif;">(aq) <span style="font-family: Arial,Helvetica,sans-serif;"> Another source for the formation of acid deposition is the primary pollutant NO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">x <span style="font-family: Arial,Helvetica,sans-serif;">. The exhaust of vehicles contains both nitrogen monoxide (NO) and nitrogen dioxide (NO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">), which reacts in the following way to produce either nitrous (HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">) or nitric (HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 <span style="font-family: Arial,Helvetica,sans-serif;">) acids: <span style="font-family: Arial,Helvetica,sans-serif;"> N <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + O <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + heat → 2NO(g) 2NO(g) + O <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) → 2NO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) 3NO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">O(l) → 2HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 <span style="font-family: Arial,Helvetica,sans-serif;">(aq) + NO(g)

<span style="font-family: Arial,Helvetica,sans-serif;"> or

<span style="font-family: Arial,Helvetica,sans-serif;"> 4NO(g) + O <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) + 2H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">O(l) → 4HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(aq) The formation of nitrogen (II) oxide [NO] is the result from the combination of nitrogen and oxygen in the air at high temperatures in internal combustion engines. Nitrogen (IV) oxide is formed when NO is released into the air and has further reaction with more oxygen. When it reacts with water, it produces <span style="font-family: Arial,Helvetica,sans-serif;"> nitric acid (HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 <span style="font-family: Arial,Helvetica,sans-serif;">). Alternatively, NO can react with oxygen and water to produce <span style="font-family: Arial,Helvetica,sans-serif;">HNO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2.

The lower concentrations of both nitrogen oxides and sulfur dioxides than atmospheric carbon dioxide are the main reasons for the slight acidity in natural rainwater. In addition to being more soluble than carbon dioxide, these gases have greater effects on the pH of the precipitation.

**<span style="font-family: Arial,Helvetica,sans-serif;">2.2 Environmental Effects ** <span style="font-family: Arial,Helvetica,sans-serif;">Have you seen the building on the right before? Do you know what it is?

<span style="font-family: Arial,Helvetica,sans-serif;"> If you have seen this historic structure before and know what it is, you should most probably know that it is made out of marble. Marble is also known as limestone (CaCO3) and it reacts with sulfuric acid in rain which will corrode and damage the building. The equation of this process is given by:

CaCO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 (s) + <span style="font-family: Arial,Helvetica,sans-serif;">H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">4 <span style="font-family: Arial,Helvetica,sans-serif;">(aq) → Ca<span style="font-family: Arial,Helvetica,sans-serif;">SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">4 (aq) + <span style="font-family: Arial,Helvetica,sans-serif;">H <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">O(l) + CO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 (g) This process is irreversible once it happens and thus explains why countless of irreplaceable monuments, buildings and statues are forever lost. <span style="display: block; font-family: Arial,Helvetica,sans-serif; text-align: left;">Besides affecting historic structures, we can also observe the undesirable effects that acid deposition has caused on our surroundings. When rain falls onto our aquatic environments (lakes, rivers and streams, etc.), the pH value of the water will decrease. The acidity will cause the food chain of the ecosystem to break down which will eventually affect us. The lowering of water's pH value will either directly kill fish or affect their ability to successfully reproduce or for their young to survive. This in turn limits the food supply that is available to birds, snakes and insects whose diet is directly linked to the health of water supplies.

There are many countries with four seasons. Many people love the change in seasons because of the different climate experienced. However, when every winter changes to spring, some parts of the world do not anticipate this change.

**<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">What is Acid Shock? ** <span style="font-family: Arial,Helvetica,sans-serif;">It occurs during spring when large quantities of snow and ice melt and bombard the water supplies with huge amounts of acid all at once. The vast amount of water is often 100 times more acidic than normal rainfall.

<span style="font-family: Arial,Helvetica,sans-serif;">As mentioned before, the ecosystem is affected as a whole, so this does not exclude forests. Acid deposition contributes to the direct effects by damaging the surfaces of leaves and needles which reduce the tree's ability to withstand cold, inhibits seed germination and reproduction.

<span style="font-family: Arial,Helvetica,sans-serif;">Indirect effects include leaching of valuable nutrients from soils when cation exchange happens during acid deposition. Hydrogen ions from the acids replace calcium, magnesium and potassium ions that are found in the soil. When leaching occurs, these ions are washed deeper into the subsoil or washed out of the topsoil instead of aiding the plant to maintain a good growth. In addition, these metal ions can be leached into our drinking water supplies.

<span style="font-family: Arial,Helvetica,sans-serif;">Deterioration of plants, wildlife and water supplies will ultimately lead to a decrease in the economies dependent on the environment such as tourism, camping, aquaculture and fishing.

<span style="font-family: Arial,Helvetica,sans-serif;">As we are strongly dependent on our environment, we do not have the ability to put an end to all activities in the world just to save it and ourselves. Hence, we can only try to minimize the production of acid deposition.
 * <span style="font-family: Arial,Helvetica,sans-serif;">How to Control Acid Deposition? **

<span style="font-family: Arial,Helvetica,sans-serif;">One way of removing SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%;">2 <span style="font-family: Arial,Helvetica,sans-serif;"> when coal is burned in smelting industries is using powedered limestone which can convert SO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%;">2 <span style="font-family: Arial,Helvetica,sans-serif;"> to CaSO <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%;">3 <span style="font-family: Arial,Helvetica,sans-serif;"> and be removed as sludge:

CaCO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 (s) <span style="font-family: Arial,Helvetica,sans-serif;">→ CaO(s) //+// CO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 (g) CaO(s) //+// SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 (g) <span style="font-family: Arial,Helvetica,sans-serif;">→ CaSO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">3 (g) To remove any remaining SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2, an aqueous solution of CaO can be added to the chamber before the gases escape through the smokestack which is a process called scrubbing:

2CaO(aq) //+// 2SO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 (g) <span style="font-family: Arial,Helvetica,sans-serif;">+ O <span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">2 <span style="font-family: Arial,Helvetica,sans-serif;">(g) → 2CaSO<span style="font-family: Arial,Helvetica,sans-serif; font-size: 80%; vertical-align: sub;">4 (aq) Or alternatively, the SO2 can be used in the production of sulfuric acid in Contact Process. The percentage of sulfur in coal could be reduced before combustion by washing the coasl to remove the sulfur or companies could use only low-sulfur coals.

Although many aspects of the world are badly affected by the acid deposition, there are some ways in which they can be saved. In some aquatic environments, many soils and bedrock contain large amounts of limestone which help to protect the aquatic life by creating a natural buffer zone. Thus it is possible to counteract the effects of acid deposition in areas that are rich in natural limestones deposits. In today's advanced world, many famers use lime-based fertilizers to increase the pH value of the water supply so as to increase the chance of plant growth.

In conclusion, we can see that acid deposition is created from both man and the environment. We do not have control over the natural acid deposition and it is impossible for all industrial activities to stop as humans are not willing to stay at status quo. The ways to help ourselves and the environment are to decrease the production of polluted waste gases, invent more ways to balance the pH value of acid deposition and be more environmentally friendly. This will enable us to have a better world to live in.

**Acknowledgement of Sources**
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Environmental Chemistry. In Chemistry: For use with the IB Diploma Programme (pp. 269-272).
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;"> Pidwirny, M. (2006). "Acid Precipitation". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/fundamentals/8h.html
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Ecological Society of America. (2000). ACID DEPOSITION. Retrieved October 01, 2010, from ACID DEPOSITION: http://www.esa.org/education_diversity/pdfDocs/aciddeposition.pdf
 * <!--[if gte mso 10]> <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Environment, A. (2008, January). Acid Deposition. Retrieved October 01, 2010, from Acid Deposition: http://www.environment.gov.ab.ca/info/library/6193.pdf
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Picture 1: Pidwirny, M. (2006). "Acid Precipitation". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/fundamentals/8h.html
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Picture 2: Matt, N. (2008, June 24). Top Ten Historical Sites in the World. Retrieved October 01, 2010, from Top Ten Historical Sites in the World - Nomadic Matt's Travel Site: http://www.nomadicmatt.com/travel-blogs/ten-historical-sites/
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Picture 3: Endicott, D. (2010). Water Quality Modeling . Retrieved October 01, 2010, from Great Lakes Environmental Center: http://www.glec.com/capabilities/environmental_assessment/water_quality_modeling.php
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 90%;">Picture 4:Feichtenberger, K. (n.d). Europe: A Natural History. Retrieved October 02, 2010, from BBC - BBC Four Documentaries - In Pictures: http://www.bbc.co.uk/bbcfour/documentaries/features/photogallery/europe_photogallery1.shtml