Carbon dioxide from human activities

Rain unaffected by human activity contains mostly weak acids and has a pH of 5.7. The primary acid present is carbonic acid, H2C03, a weak acid that results when atmospheric carbon dioxide dissolves in water. The major pollutants in acid rain are strong acids that arise from human activities. Atmospheric nitrogen and oxygen can react to form NO, but the endothermic reaction is spontaneous only at the high temperatures of automobile internal combustion engines and electrical power stations ... 

Cathodic reduction is the most promising approach to the removal of carbon dioxide from a closed atmosphere. Methods developed so far provide for electrode materials, electrolytes, and electrolysis conditions where CO2 can be reduced to hquid organic products of low molecular weight such as formic acid. More complex systems are required to regenerate foodstuffs from the rejects of human vital activities during... 

Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases ... 

The metabolism of chloroform is well understood. Approximately 50% of an oral dose of 0.5 grams of chloroform was metabolized to carbon dioxide in humans (Fry et al. 1972). Metabolism was dose-dependent, decreasing with higher exposure. A first-pass effect was observed after oral exposure (Chiou 1975). Approximately 38% of the dose was converted in the liver, and < 17% was exhaled unchanged from the lungs before reaching the systemic circulation. On the basis of pharmacokinetic results obtained in rats and mice exposed to chloroform by inhalation, and of enzymatic studies in human tissues in vitro, in vivo metabolic rate constants (V, 3,C =15.7 mg/hour/kg, = 0.448 mg/L) were defined for humans (Corley et al. 1990). The metabolic activation of chloroform to its toxic intermediate, phosgene, was slower in humans than in rodents. 

Why aren t atmospheric levels of carbon dioxide rising as rapidly as might be expected based on the increased output of carbon dioxide resulting from human activities ... 

Gt CO2 equiv. 29 Gt anthropogenic CO2 discharges/year x 100) to the global warming potential (GWP) of actual carbon dioxide discharges from human activity. 

The main greenhouse gas is carbon dioxide, which is responsible for 49% of the effect. The emissions result chiefly of burning of fossil fuels in the electricity generation, transports and industry (5 Gton of C per year), and deforestation (0.5 to 2 Gton of C per year) [1]. Figure 1 shows the percentage contribution to carbon dioxide emissions from human activities between 1980-85 [4]. 

Human activity, particularly the burning of fossil fuels such as oil and coal, is responsible for the release of some 30 billion metric tons of carbon dioxide into the Earth s atmosphere every year. Most climate engineering proposals fall into one of two fundamentally different approaches-the removal of carbon dioxide from the atmosphere or the reflection of solar radiation from Earth s atmosphere or surface hack into space. 

Acid rain means rain having a pH lower than that of natural rain (pH 5.6). Natural rain dissolves carbon dioxide from the atmosphere to give a slightly acidic solution. The pH of rain in eastern North America and western Europe, however, is approximately 4 and sometimes lower. This acidity is primarily the result of the dissolving in rainwato of sulfiir oxides and nitrogen oxides from human activities. In the northeastern United States, the strong acid components in acid rain are about 62% sulfuric acid, 32% nitric acid, and 6% hydrochloric acid. 

Pure water is pH neutral, but rainwater is acidic. What causes rainwater to be acidic One contributing factor is that carbon dioxide from the atmosphere reacts with water to form carbonic acid, H2CO3, a diprotic acid. For a discussion of the natural sources of acidity in rainwater, and how human activities also contribute, go to the Focus On feature for Chapter 16, Acid Rain, on the MasteringChemistry site. 

Acid rain. Natural (unpolluted) precipitation is naturally acidic with a pH often in the range of 5 to 6 caused by carbonic acid from dissolved carbon dioxide and sulfurous and sulfuric acids from natural emissions of SO and H2S. Human activity can reduce the pH very significantly down to the range 2 to 4 in extreme cases, mainly caused by emissions of oxides of sulfur. Because atmospheric pollution and clouds travel over long distances, acid rain is not a local problem. The problem may manifest itself a long way from the source. Problems associated with acid rain include ... 

Approximately 6 billion tons of carbon dioxide are produced every year by human activity, with 80% from the burning of the... 

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