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Lecture 9

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Environmental Science
Tanzina Mohsin

EESA09H WIND Lecture 9 Notes Wind and Pollutant Transport Part 1 Long range transport of pollutants in the Arctic 1.1 Arctic Haze 1.2 Persistent Organic Pollutants (POPs) Part 2 Arctic Pollutant Research Torsten Meyer Part 3 Acid Rain in Southern Ontario 3.1 What is acid rain? 3.2 Acid rain precursors 3.3 Deposition of acid rain 3.4 Acid rain in Southern Ontario Part 1 Long range transport of pollutants in the Arctic We are examining two aspects of Arctic pollutants, Arctic haze and persistent organic pollutants (POPs). 1.1 Arctic Haze 1.1.1 What is it? Arctic haze was first noted in the 1950s by aircraft pilo. Since the Arctic was considered a pristine environment, this was surprising. Theynoted seasonal variation with the haze peaking in spring. Pooling of the pollutants appeared to occur. In 1972, Glen Shaw suggested that long range transport was the likely mechanism for the appearance of pollutants in the Arctic. Removal of the haze in th e Arctic environment is likely via the ArcticOceanand surrounding waters. Arctic haze consists mainly of sulfate (90%) and the remainder is largely soot (carbon) and dust . The s ulfate levels a10 to 20 ti mes greater than normal and vanadium has been de tected. The sulfates are m ixed with uncombusted carbon to form aerosols which block light and appear greyish or brownish in colour . Coal burning is the major culprit. Trace metals such as vanadium and manganese indicate origin of the pollutants. Trace cons tituents such as metals and persistent organic pollutants (POPs) can adhere to the aerosols and pool in the Arctic . 1.1.2 Why do the pollutants pool in the Arctic? They pool because of a stable atmosphere due to a persistent temperature inversion, particularly in the winter . The ground near the poles is quite cold in the winter due to lack of sunlight; this means that temperatures do not decrease with height as sharply as in other regions. Often the temperature may actually increase with height (this is callea temperature inversion). All of these prevents air from rising and so inhibits mixing and also precipitation, which would otherwise wash out the haze. The pooling is accentuated by the c ircumpolar circulation, a closed circulation around the Polar Regions (as seen in Lecture 2). The major source is Eurasia due to coal burning plants which are located further north than in North America and China. Arctic haze has a pronounced seasonal cycle, peaking in the spring. This is a result of the atmospheric sta bility. Pollutants pool in the winter and early spring during the seasonal temperature inversion. Spring solar radiation destroys the temperature inversion and pollutants mix vertically and dissipate. One impact of Arctic haze is reduced visibility, espec ailly in the spring. Snow and ice in the Arctic become contaminated as a result of haze deposition. This can lead to bioaccumulation of pollutants, a point more important for POPs. 1.1.3 Remediation The remediation of Arctic haze is easy to identify. Essentially it is the reduction of emission of sulfates, particularly from coal burning plants. However this as we have seen in earlier lectures is difficult to implement. The focus of the reductions should be in Eurasia as this has been identified as the most signifi cant source of Arctic haze pollutants. This may be one case in which the US is not the major culprit. 1.2 Persistent Organic Pollutants (POPs) 1.2.1 What are they? POPs are long lasting organic compounds that become concentrated as they move through the food chain. POPs bioaccumulate (accumulate in living things) and biomagnify (concentrations get larger higher up the food chain) . Most POPs are hydrophobic (dont dissolve easily in water) and lipophilic(bonds easily to fats). This latter characteristic leads to the bioaccumulation in biotic matter. Examples include PCBs, DDT, Chlordane and Heptachor, among many others. PCBs are Polychlorinated biphenyls . They were introduced in 1929 by Monsanto Corporation. They are actually a mixture of over 200 chlorinated compounds. They have been used as coolants and lubricants in electronic equipmen.t Production ceased in 1977 in US and elsewhere. They have been linked to skin conditions and liver damage. PCBs were released in the Great Lakes . Because they are hydrophobic they partition into the sediment , accumulate in biota or volatilize readily into the atmosphere. The Great Lakes food chain biomagnifies (chemical levels are higher in organisms higher up the food chain)PCBs to dangerous levels . There are concerns for fishconsumption by pregnant women,and First Nations populations in general. DDT is Dichlorodiphenyltrichloroethane. It was introduced in 1939 as an insecticide to combat malaria and typhus. It was b anned in 1972 in US (and most other western nations). However, 675,000 tons were applied in US . They are s till found in the environment. It is likely a carcinogen and other deleterious health effects have been reported. Chlordane is C 10H 6l 8Octachlorodihydrodicyclopentadiene ). It was used as an insecticidefrom 1948 to 1983. It has been b anned except for fire ant control in power transformers. It has been linked to cancer and behaviour disorders. Heptachlor is C 10H 5l 7Heptachlorodicyclopentadiene ). It also is an i nsecticide (termiticide). It is a w hite powder (smells like mothballs). It was b anned in 1988except for use on fire ants in power transformers . Production ceased in 1997 . It has been linked to damage to the nervous system . 1.2.2 POP Transport (Wania and Mackay, 1993) Frank Wania is an Associate Professor at UTSC. H e is an award winning environmental chemist whose research has focused on the transport of POPs in the environment. Mackay was his PhD supervisor. The Wania and Mackay (1993) paper reviewed the POP data from various sources and then conceptualized a chemic al and dynamical model. POPs are ubiquitous in the Arctic in spite of there being no local sources. The ban of POPs has not resulted in any significant reduction of levels. The conceptual model is as follows. POPs are released into the atmosphere in a process called volatilization (partitioning as a gas into the atmosphere). As the POP travels via air currents poleward, cooling occurs and the POPs (depending on the chemical characteristics of the POP) deposits in liquid and solid form in a process similar to condensation referred to as fractionation. Then during a warmer time (day time or summer) the POP re-volatilizes and travels further north. This process continues until the POP reaches the polar region. This is a process called grasshoppering. Anotherpathway is for POPs to adsorb (bond) onto sulfates (which occurs more readily at lower temperatures) and enter the Arctic via the Arctic haze route. 1.2.3 Why does pooling take place in the Arctic? Cold temper
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