How Sinkholes Develop?... With Chemical Equation

How Sinkholes Develop?... With Chemical Equation

•Naturally occurring sinkholes are most commonly found in a type of terrain known as karst topography, which consists of bedrock (rock beneath the soil) filled with nooks and crannies. The underlying bedrock in karst landscapes is usually made of limestone. A great portion of the state of Florida is, in essence, sitting atop one continuous slab of limestone, making it vulnerable to sinkholes. Limestone is composed of calcium carbonate (CaCO3), which primarily comes from the remnants of corals and other types of marine organisms, whose shells are made of calcium carbonate.

•Sinkholes often form when acidic groundwater or acid rain dissolves limestone, a porous 9-rock present in the soil, creating voids and cavities. The soil resting on top of the limestone then sinks or collapses, causing a sinkhole.

•Limestone builds up slowly after these animals die and their shells are deposited and accumulate over time. Other substances composed of calcium carbonate include marble, chalk, Tums antacid tablets, and eggshells. To understand how limestone bedrock contributes to sinkholes, consider what happens when you place an egg in a glass of vinegar, which contains 5% acetic acid (CH3COOH). You will notice that little bubbles of carbon dioxide gas form almost immediately and, within a day or two, the eggshell will have completely disappeared, leaving you with the egg’s translucent membrane to protect the egg. The eggshell, which is composed of calcium carbonate, does not normally dissolve in water, but in the presence of acetic acid, calcium carbonate and acetic acid react with each other, causing the eggshell to dissolve according to the following chemical reaction:

•2 CH3COOH (aq) + CaCO3 (s) Acetic acid + Calcium carbonate
•➞ [Ca2+ (aq) + 2CH3COO– (aq)] + H2O (l)
•➞ Calcium acetate + Water + CO2 (g) + Carbon dioxide

•Any substance made of calcium carbonate will react with an acid. Limestone, being made of calcium carbonate, will react with an acid and will be slowly worn away. But are there acids underground?

•To answer this question, consider what happens to rainfall (which eventually 9-becomes groundwater) as it passes through the atmosphere. While falling through the air, the rain comes into contact with carbon dioxide. Although carbon dioxide comprises only about 0.04% of the atmosphere, that is enough to make rainfall acidic, lowering its Ph to about 5.6. So, by the time rainfall reaches the ground, it has turned into acid. The reaction is as follows:

•H2O (l) + CO2 (g) ➞ H2CO3 (aq)
•Water + Carbon dioxide ➞ Carbonic acid
•Carbonic acid then dissociates to give a hydrogen ion (H+) and a bicarbonate ion (HCO3 –):

•H2CO3 (aq) ➞ H+ (aq) + HCO3 – (aq)

•The ability of carbonic acid to dissociate by producing hydrogen ions is what makes this molecule an acid. Over time, acidic rainwater seeps into the ground and comes into contact with limestone bedrock. Water makes its way into cracks or pockets in the rock, reacting with the limestone and eventually making holes and fissures in the rock. Sinkholes occur when acidic rainwater has eaten away so much of the underlying limestone bedrock beneath the soil that the ground collapses.

•The more it rains, the greater the amount of carbonic acid leaching into the soil below.

•Humid areas have the most rainfall. High humidity in the air leads to cloud formation, which eventually produces rainfall. So it is no surprise that Florida leads the United States in the number of sinkholes because it has both limestone bedrock and high humidity.


•The acidity of rainwater is not the only reason water in the ground is acidic. Decaying organic materials and root respiration also produce carbon dioxide, which dissolves in soil water to form carbonic acid.

Land subsidence

Land subsidence

Land subsidence is a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials.

Causes of  Subsidence 

Subsidence is caused by a diverse set of human activities and natural processes, including :-
1.mining of coal , metallic ores,
2.Limestone , salt, and sulfur; withdrawal of groundwater, petroleum, and geothermal fluids;
3.dewatering of organic soils;
4.pumping of groundwater from limestone;
5.wetting of dry, low-density deposits, which is known as hydro compaction; natural sediment compaction;
6.melting of permafrost; liquefaction; and crustal deformation

Catastrophic Subsidence as Result For Water Level Decline (Sinkholes).

•Water is stored in underlying carbonate rocks and moves through interconnected openings along bedding planes, joints, fractures, and faults, some of which are enlarged by solutioning.
•Recharge from precipitation, in response to gravity, moves downward into this system of openings or toward the stream channel, where it discharges and becomes streamflow

•Sinkholes can be separated into categories described as“induced” and “natural.” Induced sinkholes are those caused or accelerated by human activities, whereas natural ones occur in nature. Sinkholes resulting from water level declines

Induced sinkholes

•Induced sinkholes (catastrophic subsidence) are those caused, or accelerated, by human water development/management activities
•activities. These sinkholes commonly result from a water level decline due to pumpage.
•Are most predictable in a youthful karst area impacted by groundwater withdrawals.

Triggering mechanisms resulting from water level declines

(1)loss of buoyant support of the water
(2)increased gradient and water velocity
(3)water-level fluctuations

Effects of Groundwater Contamination

Effects of Groundwater Contamination

Understanding the common sources of groundwater pollution is always a good first step, but from there, you should realize what the effects on your health and the world around you can potentially be when this type of contamination is present. Now that you can recognize what are possible sources of groundwater contamination, read on to find out more about what this means for you and your community.

1-Health

Health effects are some of the greatest risks associated with groundwater pollution. Here are just a few you should be concerned with.

Hepatitis. In areas where septic systems have not been installed or kept up correctly, groundwater may become infected with hepatitis due to human waste present in the water supply. Hepatitis is a very serious condition that causes irreversible damage to the liver.

Dysentery. Much like hepatitis, dysentery can be caused by drinking water where waste is present—either human or animal in nature. Once again, when septic systems don’t operate correctly, the chance for dysentery is much higher, much like with hepatitis. Dysentery causes infection throughout the intestine and digestive system, and can also cause diarrhea so severe it can lead to dehydration and even death when not treated properly.

Poisoning. When wells are not dug or placed correctly, poisons from both nature and from human use of pesticides and solvents can leach into the well water and poison the water supply. When humans then drink this water, they can become very ill very fast from exposure to chemicals and other pollutants that are unsafe for ingestion. This can also make animals sick as well, including animals that might be watered from a well on a farm.

2-Economy

When groundwater becomes contaminated, the economy can also easily suffer. Check out this list of potential economic problems associated with groundwater pollution.

Depreciating value of land. When groundwater becomes more contaminated in a given area, that area becomes less capable of sustaining human, animal, and plant life. If the area is known for its natural beauty and that nature begins to suffer the effects of pollution, the chances of people wanting to live there decrease even more. Although it might not be an immediate result of groundwater pollution, the depreciation of land value is definitely a potential side effect.

Less stable industry. Many industries rely on groundwater to help produce their products and keep their factories running smoothly. Since the pH and quality of groundwater from a given area rarely changes, it becomes a vital part of many industries that rely on water they don’t have to constantly test. However, when groundwater becomes polluted, this convenience is stripped away, and the industries are less capable of stable production. This, in turn, can affect the economy in any given area as industries are forced to move.

3-Environment

Last but certainly not least, the environment can be seriously altered when groundwater is polluted. Here are just some of the ways in which this occurs.

Nutrient pollution. Groundwater pollution can cause certain types of nutrients that are necessary in small amounts to become far too abundant to sustain normal life in a given ecosystem. Fish might start dying off quickly because they are no longer able to process the water in their water supplies, and other animals might become sick from too much of certain types of nutrients in the water they drink. Plants might not be able to absorb water as easily, and the entire ecosystem will suffer

Toxic water in ecosystems. When groundwater that supplies lakes, rivers, streams, ponds, and swamps becomes contaminated, this slowly leads to more and more contamination of the surface water as well. When this happens, fish, birds, animals and plants that live in the area become sick and die off quickly. This is a huge factor in the destruction of the wetlands, which rely heavily on groundwater to recharge their lakes and ponds after drought periods. In turn, people who use this land for hunting, fishing, and even for their own sources of clean water are affected by this type of pollution.

Sources of Groundwater Contamination

Sources of Groundwater Contamination

It’s always a good idea to be able to recognize what causes groundwater pollution so you can help step up and make a difference when you see it in your area. When it comes to this type of pollution, every source can be grouped into one of four categories: direct, indirect, manmade, and natural. Although natural sources of pollution often can’t be changed much, there is always something you can do about other sources.

1-Direct

When learning about what causes groundwater contamination, you should first start with direct contaminants, as these are the ones you’re more likely to come into contact with.

Hazardous waste. When hazardous waste is disposed of or dumped incorrectly, the chances of it spilling and leaching into soil and water are great. It’s very likely for this type of spill to occur and go completely unnoticed. Unfortunately, this is also true of more widely recognized hazardous waste spills, but there’s very little that can be done about it. Once a spill occurs, it can almost never be removed from groundwater.

Landfills. Landfills are another direct cause of pollution in groundwater. The longer a landfill remains full of waste, the more the toxins from that waste seep into the soil below and around the landfill. This leads to groundwater contamination almost immediately. When landfills are very large, the amount of groundwater polluted by them is significant.

2-Indirect

But what are some sources of groundwater pollution that are less direct?

Atmospheric pollutants. Sometimes, when surface water in the area becomes polluted, this can lead to those pollutants evaporating into atmospheric air and water. In turn, polluted air can drift into areas where humans are more present, and polluted rain can fall as acid rain. This damages the environment and can also cause serious health risks for people in the area, too.

Petroleum fuels. Diesel and gasoline are well-known indirect causes of groundwater pollution. In some instances, these fuels, when kept in underground storage, can leak significantly and seep into the ground around them, leading to groundwater contamination. Most of the time, however, the use of these fuels pollutes the atmosphere and leads to indirect atmospheric pollution of groundwater through the rain.

3-Man-made

It’s no secret that human beings are a huge polluter of groundwater. These are just some of the manmade ways groundwater gets contaminated.

Septic systems. In much of the United States, city-based water and sewage are unavailable, especially in very rural areas. When this is true, septic systems are usually the go-to solution to provide running water and plumbing to people in these regions. Septic systems are very common in the U.S., and in most cases, they aren’t supposed to cause any groundwater contamination at all. Unfortunately, sometimes they are installed incorrectly or become damaged over time without regular maintenance. This causes human waste to leach into the surrounding soil, which in turn causes a lot of pollution very fast.

Chemicals. Road salts, solvents, and chemicals used on roads, in lawns, and around the home are some of the leading manmade causes of groundwater pollution. When these products are used on land surfaces or homes, they are easily washed away by natural rainfall. From there, since there’s nowhere else for them to go, they seep into the soil and reach the groundwater quickly. When humans and animals then drink this water, they are ingesting these chemicals, which can cause major health problems very fast. Also, when groundwater that has been affected by these chemicals is then used in agriculture or industry, it is unable to provide the proper nutrients and hydration required to get the job done.

Pesticide. Much like chemicals and other man-made solutions, pesticide is prone to washing into the soil after heavy rainfalls, especially when it is used frequently by farmers and other members of the agricultural industry. The chemicals involved in pesticides are very dangerous for both human and animal consumption, and when they reach groundwater, they can almost never be completely removed.

4-Natural

Learning about groundwater contamination involves finding out more about natural contaminants like animal waste, which is not a major source of groundwater pollution.

Animal waste. Although animal waste is usually more of a problem for surface water contamination and often stays out of groundwater, this isn’t always the case. In some situations, especially where animal life is very prevalent, urine and feces left behind by animals seep into the ground and cause some pollution to the groundwater there. When this happens, the type of pollution caused by these contaminants is usually easy to remove by water treatment facilities. However, it does make groundwater unsafe to drink without treatment.

Arsenic. Sometimes, arsenic is naturally present in rocks. When groundwater passes through or sits in these rocks for too long, it can cause arsenic to build up in the groundwater to levels that are capable of poisining animals or people who drink it. This is rare, but it does occur, especially in areas where mining has been present and might have exposed these types of rocks. Again, regular water treatment can usually remove arsenic from groundwater.

Radon. Radon gas is also another natural pollutant that can nevertheless cause serious problems. If a human being or an animal consumes water that has been polluted with radon gas, the results can be potentially fatal. Like the other types of natural pollution in groundwater, radon gas can sometimes be removed by treatment. However, it’s very important not to drink water that could have potentially been polluted with radon until it has been thoroughly tested by professionals.