Geo 13

CO2 Carbon Dioxide

the concentrations of both nitrogen oxides and sulfur dioxides are much lower than atmospheric carbon dioxide which is mainly responsible for making natural rainwater slightly acidic. However, these gases are much more soluble than carbon dioxide and therefore have a much greater effect on the pH of the precipitation.

Acid

An acid can be defined as any substance that *when dissolved in water dissociates to yield corrosive hydrogen ions.*

Precipitation pH

*Precipitation* normally has a *pH between 5.0 to 5.6* because of natural atmospheric reactions involving *carbon dioxide.* For comparison, distilled water, pure of any other stubstances, would have a pH of 7.0. *Precipitation* is considered to be *acidic* when its pH falls *below 5.6* (which is 25 times more acidic than pure distilled water). Some sites in eastern North America have precipitation events with pHs as low as 2.3 or about 1000 times more acidic than natural.

Six Air Pollutants

*The Clean Air Act* requires *EPA* to set *National Ambient Air Quality Standards* for six common air pollutants. These commonly found air pollutants (also known as "criteria pollutants") are found all over the United States. They are *particle pollution (often referred to as particulate matter), ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead.* Of the six pollutants, *particle pollution and ground-level ozone are the most widespread health threats.* EPA calls these pollutants *"criteria" air pollutants* because it regulates them by developing human health-based and/or environmentally-based criteria (science-based guidelines) for setting permissible levels. The set of limits based on human health is called *primary standards.* Another set of limits intended to prevent environmental and property damage is called *secondary standards.* These pollutants *can harm your health and the environment, and cause property damage.*

Acid Deposition Formation

Acid deposition can form as a result of *two processes.* In some cases, *hydrochloric acid can be expelled directly into the atmosphere.* More commonly it is due to *secondary pollutants that form from the oxidation of nitrogen oxides (NOx) or sulfur dioxide (SO2) gases that are released into the atmosphere*. Reactions at the Earth's surface or within the atmosphere can *convert these pollutants into nitric acid or sulfuric acid.* The process of altering these gases into their acid counterparts can take several days, and during this time these pollutants can be *transported hundreds of kilometers from their original source.* Acid precipitation formation can also take place at the *Earth's surface* when nitrogen oxides and sulfur dioxide settle on the landscape and interact with *dew or frost.*

Acid Deposition; Aquatic Effects

Acid deposition influences the environment in several different ways. In *aquatic systems*, acid deposition can effect these ecosystems by lowering their pH. However, not all aquatic systems are effected equally. Streams, ponds, or lakes that exist on *bedrock or sediments rich in calcium and/or magnesium* are naturally buffered from the effects of acid deposition. Aquatic systems on *neutral or acidic bedrock* are normally very sensitive to acid deposition because they lack basic compounds that buffer acidification. In *Canada*, many of the water bodies found on the granitic Canadian Shield fall in this group. One of the most obvious effects of aquatic acidification is the decline in fish numbers. Originally, it was believed that the fish died because of the increasing acidity of the water. However, in the 1970s scientists discovered that acidified lakes also contained high concentrations of toxic heavy metals like mercury, aluminum, and cadmium. The source of these heavy metals was the soil and bedrock surrounding the water body. Normally, these chemicals are found locked in clay particles, minerals, and rocks. However, the acidification of terrestrial soils and bedrock can cause these metals to become soluble. Once soluble, these toxic metals are easily leached by infiltrating water into aquatic systems where they accumulate to toxic levels. *Lake acidification* begins with the deposition of the byproducts acid precipitation *(SO4 and H ions)* in terrestrial areas located adjacent to the water body. *Hydrologic processes* then move these chemicals through *soil and bedrock* where they can react with *limestone and aluminum-containing silicate minerals*. After these chemical reactions, the *leachate* continues to travel until it reaches the lake. The acidity of the leachate entering lake is controlled by the chemical composition of the effected lake's surrounding soil and bedrock. If the soil and bedrock is rich in limestone the acidity of the infiltrate can be reduced by the *buffering action of calcium and magnesium compounds*. *Toxic aluminum (and some other toxic heavy metals)* can leach into the lake if the soil and bedrock is rich in aluminum-rich silicate minerals. In the *middle latitudes*, many acidified aquatic systems experience a phenomenon known as *acid shock.* During the winter the *acidic deposits can buildup in the snowpack*. With the arrival of spring, snowpack begins to *melt* quickly and the acids are *released over a short period of time at concentrations 5 to 10 times more acidic than rainfall.* Most adult fish can survive this shock. However, the eggs and small fry of many spring spawning species are extremely sensitive to this acidification.

Carbon Monoxide

Carbon monoxide (CO) is a *colorless, odorless gas emitted from combustion processes* Nationally and, particularly in urban areas, the majority of CO emissions to ambient air come *from mobile sources*. CO can cause *harmful health effects* by reducing oxygen delivery to the body's organs (like the heart and brain) and tissues. At extremely high levels, CO can cause *death*. EPA first set air quality standards for CO in 1971. For protection of both public health and welfare, EPA set a *8-hour primary standard at 9 parts per million (ppm) and a 1-hour primary standard at 35 ppm.* In a review of the standards completed in *1985, EPA revoked the secondary standards* (for public welfare) due to a lack of evidence of adverse effects on public welfare at or near ambient concentrations. The last review of the CO NAAQS was completed in 1994 and the Agency chose not to revise the standards at that time.

pH

The *acidity of substances dissolved in water* is commonly measured in terms of *pH* (defined as the negative logarithm of the concentration of hydrogen ions). According to this measurement scale solutions with pHs *less than 7* are described as being *acidic*, while a pH *greater than 7.0* is considered *alkaline*.

Sulfur Dioxide

Emissions of sulfur dioxide are responsible for *60-70% of the acid deposition that occurs globally.* More than 90% of the sulfur in the atmosphere is of *human origin.* The *main sources* of sulfur include: *Coal burning* - coal typically contains 2-3% sulfur so when it is burned sulfur dioxide is liberated. The *smelting of metal sulfide ores* to obtain the pure metals. Metals such as zinc, nickel, and copper are all commonly obtained in this manner. *Volcanic eruptions* - although this is not a widespread problem, a volcanic eruption can add a lot of sulfur to the atmosphere in a regional area. *Organic decay.* *Ocean spray.* After being released into the atmosphere, sulfur dioxide can either be *deposited on the Earth's surface* in the form of dry deposition *or* it can undergo the following reactions to *produce acids that are incorporated into the products of wet deposition*: *SO2 + H2O >>>>>> H2SO3 H2SO3 + 1/2O2 >>>>>> H2SO4*

Acid Deposition; Structural Effects

Finally, acid deposition effects a number *inanimate features of human construction*. *Buildings and head stones* that are constructed from limestone are easily attacked by acids, as are structures that are constructed of iron or steel. Paint on *cars* can react with acid deposition causing fading. Many of the *churches and cathedrals* in Europe are under attack from the effects of acidic deposition.

Air Pollution Trends

For each of these pollutants, *EPA tracks two kinds of air pollution trends:* *air concentrations based on actual measurements of pollutant concentrations in the ambient (outside) air at selected monitoring sites throughout the country* and *emissions based on engineering estimates of the total tons of pollutants released into the air each year.* Despite the progress made in the last 30 years, millions of people live in counties with monitor data showing unhealthy air for one or more of the six common air pollutants.

Ozone

Ground level or "bad" ozone is not emitted directly into the air, but is *created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.* Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major *sources of NOx and VOC*. *Breathing ozone* can trigger a variety of health problems, particularly for children, the elderly, and people of all ages who have lung diseases such as asthma. *Ground level ozone* can also have harmful effects on sensitive vegetation and ecosystems.

Energy Characteristics of Urban Areas

In a city, concrete, asphalt, and glass replace natural vegetation, and vertical surfaces of buildings are added to the normally flat natural rural landscape. *Urban surfaces generally have a lower albedo, greater heat conduction, and more heat storage than the surfaces they replaced.* The geometry of city buildings causes the *absorption of a greater quantity of available incoming solar radiation and outgoing terrestrial infrared radiation.* Even in early morning and late afternoon the urban areas are intercepting and absorbing radiation on their vertical surfaces. *In urban areas, large amounts of heat energy are added to the local energy balance through transportation, industrial activity, and the heating of buildings.* In winter, the amount of heat generated from the burning of fossil fuels in New York City is 2.5 times greater than the heat absorbed from the Sun. Finally, *in rural areas, evaporation and transpiration from various natural surfaces act to cool the land surface and local atmosphere*. In urban locations, *drainage systems* have been created to quickly remove surface water. Thus, little water is available for cooling.

Lead

Lead (Pb) is a metal found *naturally in the environment as well as in manufactured products.* The major sources of lead emissions have historically been from *fuels* in on-road motor vehicles (such as cars and trucks) and *industrial sources*. As a result of EPA's regulatory efforts to remove lead from on-road motor vehicle gasoline, emissions of lead from the transportation sector dramatically declined by 95 percent between 1980 and 1999, and levels of lead in the air decreased by 94 percent between 1980 and 1999. Today, the highest levels of lead in air are usually found near *lead smelters*. The major sources of lead emissions to the air today are *ore and metals processing and piston-engine aircraft operating on leaded aviation gasoline.*

Smog

London, England - coal furnaces US Photochemical smog bejing only occurs in the daytime not night

Nitrogen Dioxide

Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as "oxides of nitrogen," or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid and nitric acid. EPA's National Ambient Air Quality Standard *uses NO2 as the indicator for the larger group of nitrogen oxides*. NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of *ground-level ozone, and fine particle pollution*, NO2 is linked with a number of adverse effects on the *respiratory system*. EPA first set standards for NO2 in 1971, setting both a *primary standard (to protect health)* and a *secondary standard (to protect the public welfare)* at 0.053 parts per million (53 ppb), averaged annually. The Agency has reviewed the standards twice since that time, but chose not to revise the annual standards at the conclusion of each review. In January 2010, EPA established an *additional primary standard at 100 ppb, averaged over one hour.* Together the primary standards protect public health, including the health of sensitive populations - people with asthma, children, and the elderly. No area of the country has been found to be out of compliance with the current NO2 standards.

Particulate Matter

Particulate matter, also known as *particle pollution or PM*, is a *complex mixture of extremely small particles and liquid droplets.* Particle pollution is *made up of* a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles. The *size of particles* is directly linked to their potential for causing *health problems.* EPA is concerned about particles that are *10 micrometers in diameter or smaller* because those are the particles that generally pass through the throat and nose and *enter the lungs*. Once inhaled, these particles can affect the *heart and lungs* and cause serious health effects. EPA groups particle pollution into *two categories*: "*Inhalable coarse particles*," such as those found near roadways and dusty industries, are larger than 2.5 micrometers and smaller than 10 micrometers in diameter. "*Fine particles*," such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air. China = bad. Sky hardly looks blue. Can increase precipitation in an area.

Sources

Pidwirny, M. (2006). "Introduction to Applied Climatology". Fundamentals of Physical Geography, 2nd Edition. June 2nd, 2015. http://www.physicalgeography.net/fundamentals/7w.html

Nitrogen Oxide

Some 95% of the elevated levels of nitrogen oxides in the atmosphere are the result of *human activities*. The remaining 5% comes from several *natural processes.* The major sources of nitrogen oxides include: *Combustion of oil, coal, and gas. Bacterial action in soil. Forest fires. Volcanic action. Lightning.* Acids of nitrogen form as a result of the following atmospheric chemical reactions *NO + 1/2O2 >>>>>> NO2 2NO2 + H2O >>>>>>HNO2 + HNO3 NO2 + OH >>>>>> HNO3*

Sulfur Dioxide

Sulfur dioxide (SO2) is one of a group of *highly reactive gasses* known as "oxides of sulfur." The largest sources of SO2 emissions are from *fossil fuel combustion at power plants (73%) and other industrial facilities (20%).* Smaller sources of SO2 emissions include *industrial processes* such as *extracting metal from ore*, and the *burning of high sulfur containing fuels by locomotives, large ships, and non-road equipment*. SO2 is linked with a number of adverse effects on the *respiratory system*. EPA first set standards for SO2 in 1971. EPA set a 24-hour primary standard at 140 ppb and an annual average standard at 30 ppb (to protect health). EPA also set a 3-hour average secondary standard at 500 ppb (to protect the public welfare). In 1996, EPA reviewed the SO2 NAAQS and chose not to revise the standards. In 2010, EPA revised the primary SO2 NAAQS by establishing a new 1-hour standard at a level of 75 parts per billion (ppb). EPA revoked the two existing primary standards because they would not provide additional public health protection given a 1-hour standard at 75 ppb.

Acid Deposition; Human Effects

The effects of acidic deposition on humans can be divided into *three main categories.* Acid deposition can influence human health through the following methods: Toxic metals, such as mercury and aluminum, can be released into the environment through the acidification of soils. The toxic metals can then end up in the drinking water, crops, and fish, and are then *ingested by humans through consumption.* If ingested in great quantities, these metals can have toxic effects on human health. One metal, *aluminum*, is believed to be related to the occurrence of *Alzheimer's disease*. Increased concentrations of *sulfur dioxide and oxides of nitrogen* have been correlated to increased hospital admissions for *respiratory illness.* Research on *children* from communities that receive a high amount of acidic pollution show increased frequencies of *chest colds, allergies, and coughs*. Acid deposition also influences the *economic livelihoods* of some people. Many lakes and streams on the eastern coast of North America are so acidic that the fish decline significantly in numbers. The reduced *fish* numbers then influence commercial fishermen and industries that rely on sport fishing tourism. *Forestry and agriculture* are effected by the damage caused to vegetation. In some areas of eastern North America and Europe, large die-backs of trees have occurred.*

Acid Deposition; Agricultural Effects

The severity of the impact of acid deposition on *vegetation* is greatly dependent on the *type of soil* the plants grow in. Similar to surface water acidification, many soils have a natural *buffering capacity* and are able to neutralize acid inputs. In general, soils that have a lot of *lime* are better at neutralizing acids than those that are made up of siliceous sand or weathered acidic bedrock. In less buffered soils, vegetation is effected by acid deposition because: *Increasing acidity results in the leaching of several important plant nutrients, including calcium, potassium, and magnesium*. Reductions in the availability of these nutrients cause a decline in plant growth rates. The heavy metal *aluminum* becomes more mobile in acidified soils. Aluminum can damage roots and interfere with plant uptake of other nutrients such as magnesium and potassium . Reductions in soil pH can cause *germination of seeds and the growth of young seedlings to be inhibited*. Many important soil organisms *cannot survive* is soils below a *pH of about 6.0*. The death of these organisms can inhibit decomposition and nutrient cycling. High concentrations of nitric acid can increase the availability of nitrogen and reduce the availability of other nutrients necessary for plant growth. As a result, the plants become over-fertilized by nitrogen (a condition known as *nitrogen saturation*). Acid precipitation can cause direct damage to the *foliage* on plants especially when the precipitation is in the form of fog or cloud water which is up to ten times more acidic than rainfall. *Dry deposition* of SO2 and NOx has been found to affect the ability of leaves to retain water when they are under water stress. Acidic deposition can *leach nutrients* from the plant tissues weakening their structure. The combination of these effects can lead to plants that have reduced growth rates, flowering ability and yields. It also makes plants more vulnerable to diseases, insects, droughts and frosts.

Acid Precipitation

The term *acid precipitation* is used to specifically describe *wet forms of acid pollution* that can be found in *rain, sleet, snow, fog, and cloud vapor.*

Micro-climate

Urban and rural environments differ substantially in their micro-climate. These climatic differences are primarily caused by the alteration of the Earth's surface by human construction and the release of artificially created energy into the environment.

Acid Deposition

can be *deposited from the atmosphere* to the Earth's surface in *wet and dry forms.* The common term to describe this process is *acid deposition* Acid deposition is not a recent phenomenon. In the 17th century, scientists noted the ill effects that industry and *acidic pollution* was having on vegetation and people. However, the term *acid rain* was first used two centuries later when Angus Smith published a book called 'Acid Rain' in 1872. In the 1960s, the problems associated with acid deposition became an international problem when fishermen noticed declines in fish numbers and diversity in many lakes throughout North America and Europe.

Observed Climate of Cities

Urban areas tend to be *warmer* than the surrounding countryside. These differences in temperature are *best observed at night under stable conditions when atmospheric mixing is at a minimum*. Climatologists call this phenomenon the *urban heat island*. The urban heat island is *strongest at the city center* where population densities are highest and industrial activity is at a maximum. The heat island effect has been described in many cities around the world, and *temperature differences between city and country can be as high as 6° Celsius.* *Wind* in urban areas is generally *calmer* than those in rural areas. This reduction in velocity is due the frictional effects of the city's vertical surfaces. However, some street and building configurations within a city can channel the wind and increase its velocity through a *venturi effect.* Certain parts of downtown Chicago and Winnipeg are noted for their unusually high wind speeds. Climatologists have measured about *up to 10% more rainfall in urban areas*. This increase may be due to the combined effect of particulate *air pollution* and increased *convectional uplift*. Air pollution may enhance rainfall by increasing the number of condensation nuclei through the atmospheric addition of smoke and dust particles. The additional generation of heat within the city increases the number of convection currents over that surface. Convection is required to initiate the development of thunderstorms.