Presented By:Zakia SultanaId:110103007

Md.Abu Ali Al HossainId:110303006

Mahbubur RahmanId:110303021

Md.NfdjdgjdjgjgjgjdgId:110203004

ACID RAINSome pollutants molecules released into the atmosphere, like Nitrogen Oxide (NOx) and sulfur dioxide (SO2),are acidic and create acids when mixed with rain water.

These substances released into the air in large quantities by industrial processes and vehicle tailpipes, increase the acidity of rain water to a pH 5 this also known as acid rain.

WHY DO WE HAVE ACID RAINUnlike in deposition, anthropogenic source emissions of SO2, NOx and VOC’s, do not vary from season to season.

The basic components of acid rain are SO2, NOx, VOC’s (volatile organic compounds)and several others. Most of the sulphur present in the atmosphere of the NorthernHemisphere is from anthropogenic sources. Coal and lignite power stationscontribute to a large amount of this pollution.

Other pollutants include particulates, hydrocarbons and carbon monoxide.Trifluoroacetic acid is an atmospheric breakdown product of thechlorofluorocarbon replacements HCFC-123, HCFC-124, and HFC-134a.Trifluoroacetic acid partitions into the various aqueous phases that occurthroughout the environment. HFC’s and HCFC’s have greater reactivity andtherefore lower atmospheric lifetimes than their predecessors, the CFC’s. Becauseof this heightened reactivity and reduced tropospheric residence time, the HFC’sand HCFC’s are less likely to be transported to the stratosphere where they mightmediate the photochemical destruction of ozone. Therefore, the HFC’s and HCFC’sare likely to cause less environmental damage than the CFC’s.

Ammonia is another determinator of acid rain.

HOW OCCUR ACID RAINNITROGEN

In the photochemical relationship between nitric oxide, ozone, and nitrogen dioxide, the concentration of these chemical species is directly affected by the intensity of sunlight. These chemicals are also known to react photo chemically with hydrocarbons and other atmospheric chemicals to form photochemical "smog." NO2 reacts faster with OH to form acid nitrate than does sulphur. In polluted air, NOx can react with organic matter to produce peroxyacetyl nitrate (PAN), a pollutant which can be transported long distances before it is eventually converted to acid nitrate. Reactions between NOx and H2O2 are very slow. HO2 reacts with NO and then nitrous oxide reacts with hydroxyl.

HO2 + NO OH + NO2

NO2 + OH HNO3

SULPHUR:Most airborne acid sulphate appears to be formed in cloud droplets. SO2 dissolves toform HSO3

- which then reacts with hydrogen peroxide (H2O2) to form acid sulphate.H2O2 is the most efficient oxidant in the conversion of dissolved SO2 to H2SO4. Thisreaction is a product of photochemistry. The lower the pH the faster the reactionproceeds. The oxidation of dissolved SO2 is rapid even at a pH value below 5.

PRECIPITATION:

Inputs of trifluoroacetic acid into natural water systems occur through wet and dry deposition, directly from the vapour stage and from runoff from the surrounding watershed.

EFFECTSSOILS AND VEGETATION

• Nitrogen is the growth depleting factor in most ecosystems. Inputs ofnitrogen are usually taken up by vegetation and soils. Hence, soils are quiteresistant to acidification. After the acid rain enters the soil, it causesnutrients such as calcium and magnesium to be leached from the soil. Thisdeprives the plants of their basic nutrients as well as causes harm to nearbywater bodies and to the ground water.

• Sulphur affects plants in a fatal manner by entering through the plant cell.Sulphur dioxide comes in contact with the chlorophyll of the cell and theother constituents of the cells and is converted there into corrosive sulfuricacid which immediately destroys the tissues in its vicinity.

EFFECTSFORESTSTrees in forests have been found to be affected by pollutants in the air. The main causes of this degradation are SO2, NOx, H2SO4 and HNO3. Pollutants can also be absorbed from the soil. This causes the tree to be affected from its roots upward. Infection of the roots is the easiest way to kill a tree.

EFFECTSWATERExcess deposition of nitrogen can lead to increased amounts of nitrate which aid in the acidification of lake waters. Acidic deposition affects aquatic life. Acidification may eliminate sensitive algae species and decrease phosphorous and inorganic carbon concentrations. It can also cause damage to fish populations. Heavy metals removed from the soil during rains could cause death to aquatic life. Fish absorb polluted water through their gills and this can harmful effects on them such as the amount of oxygen taken up by the blood is reduced and the blood circulation is affected.

EFFECTSHUMAN HEALTHEffects on human health are usually seen through the food chain by bioaccumulation and by water contamination. The chemicals that get deposited in the soil and water are consumed either directly by humans or by way of the food chain. In this way they affect human beings. The acid in the water may corrode copper and lead water pipes contaminating the drinking water.

EFFECTSWILDLIFEThe damage from acid rain to terrestrial wildlife is basically through the food chain. Accumulated heavy materials cause great damage through bio-magnification.

BUILDINGSA large variety of materials are affected by acid rain. These extend from sandstone and limestone to metals such as zinc, aluminium, copper, plastics, paper, textiles, electrical contacts e.t.c.

REMEDIESTechnical solutionsMany coal-firing power station use flue-gas desulfurization (FGD) to remove sulfur-containing gases from their stack gases. For a typical coal-fired power station, FGDwill remove 95% or more of the SO2 in the flue gases. An example of FGD is the wetscrubber which is commonly used. A wet scrubber is basically a reaction towerequipped with a fan that extracts hot smoke stack gases from a power plant into thetower. Lime or limestone in slurry form is also injected into the tower to mix with thestack gases and combine with the sulfur dioxide present. The calcium carbonate ofthe limestone produces pH-neutral calcium sulfate that is physically removed fromthe scrubber. That is, the scrubber turns sulfur pollution into industrial sulfates.

Emissions tradingIn this regulatory scheme, every current polluting facility is given or may purchase onan open market an emissions allowance for each unit of a designated pollutant itemits. Operators can then install pollution control equipment, and sell portions oftheir emissions allowances they no longer need for their own operations, therebyrecovering some of the capital cost of their investment in such equipment. Theintention is to give operators economic incentives to install pollution controls.