ABSTRACT
Carbon dioxide emission in the United States rose by 7% between 1990 and 2013. Scientists have continually raised concern over the implications of these increased levels of carbon dioxide. Evidently, such high emission levels pose a threat to the environment and life in general. The aim of the following essay is to: define weathering and identify the major classifications of weathering. The essay also clearly defines and illustrates the relationship that exists between carbon dioxide levels and the rate of chemical weathering. I will incisively discuss the combination of water and atmospheric carbon dioxide to form carbonic acid. This will prove that indeed, an increase in carbon dioxide in the atmosphere does result in a rise in the rate of chemical weathering. The essay will additionally explore ocean acidification, erosion, global warming and plant growth as aspects of the earth’s environment that are directly affected by the rising carbon dioxide levels.
Atmosphere
Carbon dioxide is a naturally occurring gas that accounts for 0.04% of natural gases. It is vital to the survival and continued presence of life on earth. Over the past decade, carbon dioxide levels have been on an upsurge. A direct consequence of human activities, which have had an effect on the production (increased production since the industrial revolution) and the environments ability to remove carbon dioxide from the atmosphere (deforestation). In the year 2013, carbon dioxide accounted for 82% of greenhouse gases emitted from human activities.
Weathering is the putrefaction and decomposition of rocks in situ, as a direct consequence of changes in temperature and rainfall. There exist three primary classifications of weathering, and these are physical and chemical weathering. On the one hand, Physical weathering results from atmospheric factors such as water, pressure and ice. Chemical weathering, on the contrary, is a consequence of atmospheric chemicals. Biological weathering is mainly facilitated by plants roots which grow through rocks o find ground water. The first two types of weathering sometimes involve biological agents and often occur together with one accelerating the other.
These increased levels of carbon dioxide have had a direct, lasting effect on weathering. The elevated carbon dioxide levels in the atmosphere result in more powerful carbon sink, which accelerates the dissolution of rocks. Primarily there are two types of chemical weathering. These are Oxidation and Carbonation. Oxidation entails a reaction between minerals present in certain rocks and the naturally occurring oxygen gas. This process majorly affects iron mineral containing rocks resulting in a reddish brown color (rust) which subsequently results in disintegration.
Carbonation is a carbon dioxide accelerated chemical process through which atmospheric carbon dioxide leads to weathering. It mainly affects chalk and limestone rocks which are made up of calcium carbonate. Carbon dioxide in the atmosphere readily dissolves in water, forming carbonic acid. The co2 is split into charged bicarbonate and hydrogen ions. The hydrogen ions are a manifestation of the acidity of a solution and thus the higher the hydrogen ion activity, the more acidic a solution and this then predisposes the solution to dissolve other compounds. The acidity of substances is measured on the pH scale; values between 7 and 14 indicate alkalinity while those between 7 and 0 are indicative of acidity. Water at its purest is expected to be a neutral figure of 7. However, the ability of carbon dioxide to dissolve in water serves to lower this pH to a value from 5 to 5.5. The increased levels of carbon dioxide emissions then, mean that there is an influx of carbon dioxide into the atmosphere. When carbon dioxide dissolves in water, it forms carbonic acid that is higher in hydrogen ion concentration hence enhanced acidity level. Through the carbon cycle, the highly acidic water evaporates and articulates rainfall. Carbonic acid containing rain water reacts variably with minerals depending on their chemical stability. Minerals such as gold and quartz (silicon dioxide) are very stable and are thus not affected by the acidity. However, calcium bicarbonate minerals are very unstable, and once this rain falls on them, a chemical reaction ensues. The rocks are altered, and they become soluble and are washed away, resulting in the formation of limestone pavements. This chemical process is accelerated by a decrease in temperatures because of the simple scientific fact that more carbon dioxide dissolves cold water.
Ocean acidification: this is a continued decline in the earth’s ocean water pH value. The ocean absorbs approximately a quarter of all carbon dioxide emissions, over the past few years there has been a drastic increase in carbon dioxide in the atmosphere and, as a result, the co2 levels in the ocean are also alarmingly high. Initially, scientists agreed that the oceans co2 absorption is purely beneficial but after years of study, conclusions have been made that elevated levels of co2 adversely affect marine life. The harmful consequences of this rising acidity include an upset in metabolic processes and rates, and immune responses and subsequently resulting in coral bleaching.
Erosion is quite closely related to weathering; it is a form of soil degradation. The increased levels of weathering have a direct bearing on erosion. As earlier discussed, weathering involves the putrefaction of rocks into smaller particles. This (putrefaction) leaves the particles exposed to the various agents of erosion which are wind and water. If not controlled, erosion will have dire effects on global agricultural productivity.
Global warming: this is the gradual increase in temperature on the earth's surface due to the greenhouse effect. Global warming subsequently results in extreme weather changes.
Plant growth: Carbon dioxide is one of the requirements for photosynthesis. Researchers have now noted that increased carbon dioxide levels positively affect the growth of plants. Additionally, carbon dioxide helps in the healthy development of plants. It serves to narrow the stoma which ultimately makes it harder for air pollutants to penetrate the leaf.
Bibliography
"5. Projected Greenhouse Gas Emissions." U.S. Department of State. Accessed February 11, 2016. http://www.state.gov/e/oes/rls/rpts/car4/90324.htm.
"Chemical Weathering of Rocks: Hydration,Hydrolysis,Carbonation,Oxidation." My Agriculture Information Bank. Accessed February 11, 2016. http://agriinfo.in/?page=topic&superid=4&topicid=249.
"Ocean Acidification." NOAA Pacific Marine Environmental Laboratory (PMEL) |. Accessed February 11, 2016. http://www.pmel.noaa.gov/co2/story/Ocean+Acidification.
