Acid Rain

Abstract

Acid rain refers to all types of precipitation- rain, snow, sleet, hail, fog- that is acidic in nature. The recent rapid acidification of many lakes including Lake Atawapaskat can not be attributed to natural causes alone, but instead to the effects of acidic pollution from the burning fossil fuels by mankind. The acidity of this lake is predominantly determined by the soil and rock type of this area because 90% of the water entering this lake comes from ground water and streams. Only 10% of the water that enter this lake comes directly from rainfall. Lake Atawapaskat is more susceptible to freshwater acidification due to its acidic geology such as granite and peat-based soil. Recently acid rain has been entering more than usual through the catchment. Some of the acid rain has been neutralized due to its alkaline-rich soil, so the water entering the lake is of low acidity. (K.M.,Oghenejoboh; 2005) Acidification of the lake occurred with time. The first natural buffering capacity of the lake neutralizes the additional acidity entering the lake, but at some point, the lake buffering capacity ran out and the acidity of the water increased rapidly. The limestone and sediments little by little were being dissolved.

Lake Atawapaskat stabilized at certain acidity, maintaining a small number of species of plants and animals, but usually lacking many fish. The onset acidification of Lake Atawapaskat brought about a clearer bluer water body due to the settling out of decaying organic matter. X, (Zhang; W, He; J, Lu 2005) Most biological life thrives best within a narrow range of pH levels, near neutral or 7.0. Aquatic vegetation and animal life vary in their susceptibility to changes in pH; some species are more acid-tolerant than others. The diversity of different species drop considerably due to many different species of plants and animals depending on one another to survive. Plankton and invertebrates are most sensitive to changes in pH. If the pH levels drop below 5.0 most fish species are affected.(J.R., Kieber; M.S. Long; J.D., Willey; 2005) There has been a large reduction in the number of zooplankton and phytoplankton. There has been a slowdown in the rate of decomposition of dead plants and animals. Fish are directly affected by interfering with their reproductive cycles.

Nitrogen and Sulfur contribute greatly to the acidification of this lake. In the form of sulphuric acid, it is the most important cause acidification.

As you can see in fig 1, most sulfur comes comes from burning coal, and oil, during which the sulfur in the fuel is converted into sulfur dioxide.

. Normal rain is slightly acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5.Sampling of the whole rain was measured from beginning to end. The most important basic point of measuring acid rain is to measure the acidity of rain as it is. It is not a good method to sample only the rainfall of the beginning in order to take the high acidic data intentionally. 80-90% of the precision in measuring acid rain is fixed by how it is sampled. (Y, LI; C, Nie; Z, Dong; 2005) Correct data can not be taken when the sampling method is not proper even how much precise measurement kit or pH meter was used. A container put in a washtub or on a vinyl sheet to keep the rain water away from mud drops. The container was put in an empty can and tied to a post. A hole was made on the bottom of the can to let the rain water go out of the can. The rain

water was collected in a funnel on a plate attached to the fence of the veranda. The funnel and the container were connected in the room with a tube.

Once the water was obtained the acidity was measured. Rain water was sucked into a pipet and poured into a capsule filled with pH indicators. Then the capsule was shuffled to dissolve indicator chemicals. Then the color of the water was compared with the color-chart to determine the value. (T.I. Khan; S, Devpura 2005)

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The biggest concern in Lake Atawapaskat was down effect of limestone outside and inside of the lake. So the effect of acid rain on limestone was tested and measured. Acid rain was put into test tubes in a water bath, so the acid can be heated up. Each test tube contained a different concentration of acid. Simillar sized limestones from the lake were weighed and the results were recorded on the Table. Each piece was put into a test tube with warm acid rain water for about a minute. The pieces of limestones were removed and reweighed and the results were recorded.

Table 1 Before and after data of acid rain reacting and dissolving limestone:

Temperature Mass before/g Average/g Mass after/g Average/g Concentration

/oC 1 2 3 1 2 3 of acid/M

10 | 0.26 0.26 0.26 | 0.25 |