Acid rain nature

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 ... 

Paerl, H.W. (1985) Enhancement of marine primary production by nitrogen-enriched acid rain. Nature 315, 747-749. 

Sulfur dioxide (SO2) is a pollutant produced by burning high-sulfur coal. It is a major cause of acid rain. Natural zeolites are the most effective filters yet found for absorbing sulfur dioxide from waste gases. As efforts to improve air quafity continue, zeolites can be used to help purify the gases from power plants that burn high-sulfur coal from the Ohio River Valley and other regions. 

P. Brimblecombe D. Stedman, Historical Evidence for a Dramatic Increase in the Nitrate Component of Acid Rain Nature, 298, No 5873, 1982. 

Selection of pollution control methods is generally based on the need to control ambient air quaUty in order to achieve compliance with standards for critetia pollutants, or, in the case of nonregulated contaminants, to protect human health and vegetation. There are three elements to a pollution problem a source, a receptor affected by the pollutants, and the transport of pollutants from source to receptor. Modification or elimination of any one of these elements can change the nature of a pollution problem. For instance, tall stacks which disperse effluent modify the transport of pollutants and can thus reduce nearby SO2 deposition from sulfur-containing fossil fuel combustion. Although better dispersion aloft can solve a local problem, if done from numerous sources it can unfortunately cause a regional one, such as the acid rain now evident in the northeastern United States and Canada (see Atmospheric models). References 3—15 discuss atmospheric dilution as a control measure. The better approach, however, is to control emissions at the source. 

Other problems occur in the measurement of pH in unbuffered, low ionic strength media such as wet deposition (acid rain) and natural freshwaters (see Airpollution Groundwatermonitoring) (13). In these cases, studies have demonstrated that the principal sources of the measurement errors are associated with the performance of the reference electrode Hquid junction, changes in the sample pH during storage, and the nature of the standards used in caHbration. Considerable care must be exercised in all aspects of the measurement process to assure the quaHty of the pH values on these types of samples. 

Natural gas will continue to be substituted for oil and coal as primary energy source in order to reduce emissions of noxious combustion products particulates (soot), unburned hydrocarbons, dioxins, sulfur and nitrogen oxides (sources of acid rain and snow), and toxic carbon monoxide, as well as carbon dioxide, which is believed to be the chief greenhouse gas responsible for global warming. Policy implemented to curtail carbon emissions based on the perceived threat could dramatically accelerate the switch to natural gas. 

Nitric acid occurs naturally, in traces, in the atmosphere in rain w from the electrical discharge of lightning and from nuclear expins. Indeed, the natural nitrates of the world have probably been formed by the action of naturally occurring nitric acid to the extent of 4-6 lbs of combined nitrogen per acre (Ref 30)... 

Rain in equilibrium with atmospheric C02, but uncontaminated by industrial emissions, should have a pH of 5.7. However, atmospheric pollution from burning fossil fuels has resulted in acid rain of pH as low as 3.5 (24). If this condition continues for a long time, it may lead to a change in groundwater composition, which may considerably change the migration of plutonium in nature. 

Why Do We Need to Know This Material Chapter 9 developed the concepts of chemical equilibria in gaseous systems this chapter extends those ideas to aqueous systems, which are important throughout chemistry and biology. Equilibria between acids, bases, and water in plant and animal cells are vital for the survival of individual organisms. To sustain human societies and protect our ecosystems, we also need these ideas to understand the acidity of rain, natural waters such as lakes and rivers, and municipal water supplies. 

Rainwater is naturally slightly acidic due to the dissolved carbon dioxide. Acid rain results when acidic sulfur and nitrogen oxides produced during the combustion of coal and oil react with rainwater (see Box 10.1). 

Figure 7.2 Acid rain occurs when water comes into contact with sulfur and nitrogen oxides in the atmosphere, which can come from natural sources or from man-made sources like cars or power plants. These acid rain-damaged coniferous trees live in the Karkonosze National Park in Silesia, Poland.

The low pH of acid precipitation can destroy forests and kill fish. Some lakes and streams lie in soil that has the natural ability to buffer the increased acidity of acid rain, usually because the soil contains a high amount of lime. Other lakes and streams, however, have no such buffering capacity. The pH of the water is not the main problem—at least not directly. The problem lies in the amount of aluminum compounds that are leached out of the soil surrounding the lake or stream at lower pHs. Aluminum is toxic to many aquatic species. 

The environmental benefits are related to energy savings and will in most cases support the usage of ATES in any country. The obvious benefit is the reduction of CO2 by using a large portion of natural renewable heat and cold in the systems. Besides the reduction of CO2, there are also fewer emissions of NOx and acidity (acid rain) to the atmosphere. 

Acid rain is caused primarily by sulfur dioxide emissions from burning fossil fuels such as coal, oil, and natural gas. Sulfur is an impurity in these fuels for example, coal typically contains 2-3% by weight sulfur.1M Other sources of sulfur include the industrial smelting of metal sulfide ores to produce the elemental metal and, in some parts of the world, volcanic eruptions. When fossils fuels are burned, sulfur is oxidized to sulfur dioxide (SO2) and trace amounts of sulfur trioxide (SC>3)J21 The release of sulfur dioxide and sulfur trioxide emissions to the atmosphere is the major source of acid rain. These gases combine with oxygen and water vapor to form a fine mist of sulfuric acid that settles on land, on vegetation, and in the ocean. 

It is important and beneficial for the environment to reduce the sulfur levels in refinery products, as well as in energy fuel (e.g. natural gas, LPG and heating oil) [1]. It has been previously reported that atmospheric emission of sulfur combustion products contributes to acid rain, ozone, and smog generation. 

---