this movie covers subtopic 6.4 acid deposition under the main topic IBE ss6 atmospheric systems and society recall our discussion from topic 6.3 photochemical smog in which I introduced this slide to you on the primary air pollutants responsible for contributing to photochemical smog and this in this subtopic six point four we are going to focus on the additional impacts of nitrous oxides and sulfur dioxide products of fossil fuel combustion and their role in acid deposition the combustion of fossil fuels produces sulfur dioxide and nitrous oxides as primary pollutants as I just reminded you of in the previous slide these gases may be converted into secondary pollutants of a dry deposition and which is Ash and dry particles or wet deposition you know in rain and snow this is called acid deposition or acid rain as more commonly referred to as defied by the United States Environmental Protection Agency acid rain or acid deposition is a broad term that includes any form of precipitation with acidic components such as sulfuric or nitric acid that fall on to the ground from the atmosphere in wet or dry forms this can include rain snow fog hail or even dust that is acidic recall that a lower substances pH or less than 7 the more acidic it is the higher a substances pH or greater than 7 the more alkaline it is normal rain has a pH of about 5.6 it is very slightly acidic because carbon dioxide does into it forming week or combining acid acid rain usually has a pH between 4.2 and 4.4 but certain pollutants increase acidification of rain which can sometimes fall to lower than pH to stop the movie in review this pH scale reminding yourself of what acidic means and what alkaline means and common and review common substances that are either acidic or basic and again reminding yourself so it rain and acid rain where that falls here is an illustration of the acid rain pathway so emissions of sulfur dioxide and nitrous oxides are released into the air where the pollutants are transformed into acid particles sulfuric and nitric acids that may be transported either locally or longer distances then these acid particles fall to the earth as wet and dry deposition as I mentioned dust rain snow etc and these then particles and depositions may cause harmful effects on soil forests streams and lakes indeed significant idea number one is that as you can imagine acid deposition can impact living systems and the built environment here you see dead or dying trees which are a common sight in areas affected by acid rain like these woods and the Jazira mountains in the Czech Republic the major rivers and tributaries of the southeastern region of Brazil shown here in this map have varying levels of pH in tropical areas with high rainfall natural acidification of soils and surface waters is common however tropical areas are especially further acidification by increased atmospheric deposition of sulfate and nitrate ions higher nitrate ammonia and sulfate contents were determined in rivers crossing urban and industrial areas the same areas that also present a polluted atmosphere these higher levels of nitrate ammonia and sulphate ions are probably due to acid deposition so what is the problem with changes in these ions and pH of fresh waters well some animals can survive in water that is moderately acidic while other man animals can only live in water that is near neutral an animal that can survive in moderately acidic water is said to have a high tolerance for acidity this chart shows the pH tolerance of various animals based on this chart what animals are sensitive to pH look at the survival right as the pH drops down into more acidic reasons regions which animals can no longer survive what does this tell you about the effect of pH on biodiversity as streams and lakes become more acidic the numbers of types of fish and other aquatic plants and animals in these waters decrease well how does that affect biodiversity some types of plants and animals are able to tolerate acidic waters others how often are others however are acid sensitive and will leave or die as pH declines some acidic lakes have no fish because at pH 5 most fish eggs cannot hatch at lower pH levels adult fish also die substances like aluminum that wash into the water from the soil can also harm and kill fish here is an example of the effective acidification on a natural lake acid deposition also affects forests and nutrient levels this is manifested then by leaves and buds showing yellowing or loss of chlorophyll and the damage in the form of lesions thinning and wax cuticles these and other changes reduce growth and allow nutrients to be leached out and washed away and pathogens and insects to gain entry symbiotic root microbes are killed and greatly reduce the availability of nutrients further reducing tree growth it then reduces the ability of soil particles to hold on to these nutrients such as calcium magnesium and potassium ions which are then leached out it releases toxic aluminum ions from soil particles which then damaged root hairs thus trees are weakened and may die stop the movie and study this illustration to compare the acid impact on forests you've heard this idea of aluminum coming up as a consequence of acid deposition well this is why when precipitation is exiting it results in a decrease of soil pH this makes aluminum becoming more soluble so aluminum is released from the soil and eventually ends up in streams and rivers fish are particularly sensitive to aluminum in the water at low aluminum aluminum to stir a little aluminum concentration aluminum disturbs the fish's ability to regulate salt and water in the body this inhibits normal intake of oxygen and salt leading to death higher aluminum concentrations a solid forms on fish's gills leading to death by suffocation so another impact of acid deposition this effective aluminum ions and aluminum becoming available in the wrong ways the impacts of acid deposition on likens a white hen is not a single organism remember it's the symbiosis between different organisms a fungus and an algae or cyanobacteria light can grow on trees and buildings and they are particularly sensitive to pollutants like sulphur dioxide look at this graph indicating likened diversity as a function of sulphur dioxide concentration immediately downwind from heavily polluted industrial regions very few tolerant lichen species are found lichen are thus an indicator species of high level of air pollution lichen species can be used to determine pollution levels acid deposition affects human constructions limestone buildings and statues including those with great historical value react with acid and simply dissolve here you see the impact of years of exposure to acid rain in Mexico the country's cultural heritage of the Mayan ruins is at risk of being dissolved by acid rain even the famous Taj Mahal in India has become discolored due to air pollution and acid rain acid deposition also affects human health dry deposition in the is in the form of small particles of sulfates and nitrates and these penetrate into our houses and our lungs premature death and from lung disease such as asthma and bronchitis can result from this too summarize the effects of acid deposition the possible effects of acid deposition on soil water and living organisms include direct effects such as acid on aquatic organisms and coniferous forests indirect effects such as the solubility of metal or aluminum ions on fish and indirect nutrient effects such as the leaching of plant nutrients all of these have been discussed in the previous slides stop the movie and study this figure for review on acid rain be aware that the impacts of acid deposition may be limited to areas downwind of major industrial regions but these areas may not be in the same country as the source of the emissions to understand this idea take a look at this map here are regions of polluted air emissions right the purple leading to acid rain but notice that the acid rain occurs mainly downwind of major industrial regions for example the Amazon forest it's affected from acid rain originating in Columbia resulting from air pollution generated in Ecuador and Peru what responsibilities do you have to minimize the presence of acid rain in summary acid precipitation affects our regional dry deposition oftenly occurs quite close to the source while wet deposition occurs is at slightly longer distances from the source of primary pollutants right due to the impact of wind carrying the pollutant which leads us to the significant idea number two the pollution management of acid deposition often involves cross-border issues you need to be able to evaluate pollution management strategies for acid deposition remember the table with which you evaluate pollution management strategies these are the three levels of management at the human activity producing the pollutant level at the release of the pollutant into the environment level or at the impact of the pollutant on ecosystems you will apply these same criteria to pollution management of acid deposition altering human activity producing the pollution what can you do right you can conserve energy turn off the lights and use energy efficient bulbs drive less walk take the bus or bike reduce your carbon footprint volunteer to help clean up trash and litter in local streams and rivers recycle conserve water here is a sample evaluation of altering human activity producing the pollution right if we try to incorporate using alternative energy ethanol to run cars ring and renewable energy for sources of electricity right you know the pros and cons of alternative energy recall you're learning on this we know that they help reduce co2 emissions they start an end nitrous oxide and sulfur dioxide emissions leading to acid deposition there is start there are startup and maintenance expenses and geography depends the dependence of those alternative energies can we reduce the overall demand for electricity through education campaigns in the population to turn off lights insulate houses etc well yeah we can but we do live in a fossil fuel reliant economy so it's hard can we encourage people to use less private transport to carpool use public transport to walk cycle yes yes we can but you need buy-in for that right and there is just increasing demand for power especially an Indian chai China as they industrialized so something needs to happen use low sulfur fuels remove sulfur buffer burning or burn mixed with limestone again their costs associated with that you need buy-in but it can make a difference an example of regulating and reducing the pollutants at the point of emission includes chimney scrubbers right this would be a type of management the second level it's very effective on a multiple of gases odors in particulate matter its stages can be designed to address specific pollutants right like nitrous oxides and sulfur dioxides for acid deposition however it's expensive to implement and maintain it creates other effluent stream requiring disposable disposal requires a higher level of water usage that may be a challenge in some local locales and it may require special consideration to not negatively impact ventilation rates another example at level 2 management regulating and reducing the pollutants at the point of emission is to use catalytic converters this is an exhaust emission control device fitted between the engine and the muffler on automobiles located as part of the exhaust system to remove toxic gases well the pro obviously is clean air from exhaust however it results in decreased horsepower the engine uses more energy for the converter and for burning the elements therefore you get reduced gas mileage again the catalyst slows down the circulation process of the emissions leading to higher consumption of fuel and you might have engine overheating from the additional need to burn more right so there are some some difficulties and challenges with using the catalytic concert' converters here is an example of taking a type of action at level 2 regulating and reducing the Palouse at the point of admission and evaluating them right using clean up technology at the end of pipe locations points of emission like the chimney scrubbers to remove sulfur dioxide again those can be expensive sometimes the cost of that towel technology is passed on to the consumer I mentioned the catalytic converters to convert nitrous oxides back to nitrogen gas those are also can be expensive but they are cost-effective if well maintained an example of pollution management and the cleanup and restoration stage is liming the liming of lakes and rivers which is the addition of limestone calcite primarily calcium carbonate to neutralize acid waters and soils and buffer them from rapid fluctuations in pH adding limestone to maintain a near neutral pH keeps lake and pond water safer aquatic life limestone can be applied to lawns gardens pastures and crop lands it can be applied to lakes ponds and their surrounding watersheds the advantages of lime there it's inexpensive it's available it's not toxic it's a natural mineral it's easy to distribute and it dissolves in water some disadvantages of liming is that liming has to be repeated regularly and that makes it costly liming affects biodiversity in other ways and liming treats symptoms but not the cause to put perspective on another third level management strategy regulation let's go over a timeline of air pollution specifically of course in the context of acid precipitation and deposition during the 1970s evidence for acid rain accumulates to include the death of vast tracts of german forests loss of lake biodiversity and accelerated weathering of buildings in 1970 in the u.s. we had the u.s. Clean Air Act in 1979 the UN Convention on long-range transboundary pair air pollution took place in 1983 the convention modified and 15 European countries the USA and Canada agreed to cult salt cut sulphur emissions by 30% of the 1980 levels by 1993 in 1985 30 countries adopted the Protocol on the reduction of sulphur emissions agreeing to reduce sulfur dioxide emissions by 30 percent this was called the 30 percent Club all of the countries that sign the protocol achieved this reduction and many of those that did not sign have also met these reductions in 1988 the Sofia convention producing nitrogen oxides by 30 percent also took place most countries missed this target due to increase in Motor Vehicles in 1994 the UN Convention further modified to convert cut emissions by 80 percent you might want to stop the slide and take a look at the additional details I have here again stop the movie and study the different stages but realize that by 1999 27 countries signed up to the new protocol on-loan long-range transboundary air pollution to reduce and prevent air pollution the clean air and in North America I mentioned the Clean Air Act and in 1995 the Clean Air Act further targeted sulfur dioxide emissions to below the 1980 levels so have those regulations been effective well yeah by the 2000s you already see recovery signs of recovery showing and studies showing that there have been cost benefits of over a hundred billion due to the acid rain program here is some data from that same time line rain look at the trend of nitrous oxides and sulfur dioxide concentrations over time additional look at the trend of hydrogen ions in the precipitation over time his acid rain increasing or decreasing are these pollutants staying the same or are they decreasing so you could argue by these graphs and by looking at the details of those of that time line that regulations have made a positive impact here is an overview or an example of evaluating types of action on pollution management in the third-level cleanup and restoration liming acidified lakes and rivers right I talked about that in quite detail it is effective in restoring pH but it has to be repeated regularly its cost e costly it affects biodiversity and it treats symptoms and not the cause we've talked about recolonizing damaged areas in the context of other topics liming forests tea plantations is similar to liming lakes and rivers and then I mentioned the effectiveness on regulation and international agreements they're difficult to establish and monitor but they can have positive impact here is a summary of topic 6.4 acid deposition this ends the movie for IBSS topic 6.4 acid deposition under the main topic of IB ESS topic 6 atmospheric systems and society the slides are created by me dr. Nina Markham image sources are indicated with a URL under the image if all images on a slide are from the same source this source is simply cited at the bottom of the slide another resource for you is your IB ESS textbook whether in hardback form or online such as cognitive thank you for listening