Various Aspects Of The Environment As Directed From An Online Book (Coursework Sample)

Physical Science: Our Environment
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Water Contamination
Water exists in two forms: ground water and surface water. Surface water refers to the water that is found in streams, lakes, rivers and ponds whereas ground water is that which occurs beneath the earth in soil and rocks due to infiltration of surface water. Water gets contaminated due to various human activities such as industrialization, farming, urbanization and transportation. Below the ground surface, there is a zone known as the vadose zone that contains pores that facilitate infiltration of surface water. The water contained in the vadose zone goes down by gravitational flow to a zone of saturation. It is within the zone of saturation that ground water is stored. This zone of saturation may be an aquifer, aquifage or an aquitard. An aquifer is usually permeable and has the capacity of transmitting substantial amounts of water to wells. An aquitard on the other hand has low permeability and lacks the capacity of transmitting water to wells. An aquifage is completely impermeable and lacks the capacity of transmitting groundwater.
Ground water serves a very large percentage of the population in the U.S as drinking water. This water therefore becomes unsafe for human consumption when it contains a particular percentage of pollutants due to human activities such as agriculture, industrialization, mining activities and transportation. The quality of water is determined by finding a measurement of the total amount of solid particles found in water (in milligrams per liter), which is known as total dissolved solids. Particles present in water take the form of anions such as bicarbonates, carbonates and chlorides as well as cations such as sodium potassium and magnesium. For water to be considered safe for drinking, it is necessary for the standard of water quality to be established before human consumption. Human activities such as indiscriminate disposal of sewage into water sources pose a great threat to human and aquatic life. When the liquid part of a landfill leaches and finds its way into water sources, it leads to contamination. Whenever underground tanks containing dangerous chemicals leak and find their way into ground water, it equally poses a great threat to human and aquatic life. Mining activities of different kinds of radioactive rocks such as uranium radium and thorium, exposes these rocks to ground water which leads to radioactive contamination of water. The figure below shows the common sources of water contamination.
Radioactive wastes
Radioactive wastes are generated through various ways such as: coal-fired power plants, nuclear power plants and nuclear explosions. For instance, in nuclear power plants that generate electricity, there are lots of radioactive materials that are the basic raw material for electricity generation. In the process of generating the electricity, radioactive wastes are also emitted into the air. These radioactive wastes if inhaled by human beings, they may have adverse effects on them such as respiratory problems. Nuclear fuel preparation and medical research are compliment sources of radioactive wastes. When these wastes combine with rain water, the rain water becomes contaminated and unfit for human consumption. A perfect example of the dangers of radioactive wastes is the Chernobyl disaster of 1986 that posed a great threat to human life. Use and test of nuclear weaponry, mining of uranium, nuclear power plants and improper disposal of nuclear waste are the key causes of environmental contamination by radiation. As stated earlier, the mining of radioactive elements such as uranium exposes them to ground water leading to contamination. Radioactive wastes are divided into five categories:
Movement of Contaminants in ground water
Upon reaching ground water, the pollutants get to move through it in two major ways. These are: Advection and Diffusion. Advection is the means through which dissolved particles are transported by groundwater. As the water is being withdrawn from the well for purposes of consumption, the dissolved contaminants flow into the water if the disposal site is not controlled. Diffusion on the other hand however, occurs when dissolved ionic and molecular constituents move from areas of high concentration gradient to areas of lower concentration gradient.
As the pollutants move through ground water, in porous media, dispersion reduces the concentration of the pollutants. At some point, as the pollutants move through the water, they may be retarded due to physical and chemical processes. When this occurs, the movement is then slowed down beyond the advection rate. The diagram below shows a detailed pictorial explanation of the movement of pollutants in ground water.
Environmental Restoration
There being lots of contamination going on in the environment courtesy of human activities, it is upon us to device methods and means of controlling this in order to save lives. Environmental restoration therefore entails all the efforts necessary to ensure that the environment is protected by getting rid of contaminants and pollutions from the soil, water systems, including surface and ground water. Computer-based mapping, computerized regulation, and computer-modeling are widely used in restoration. Environmental restoration may involve professionals or combined efforts of the local community. There are several methods that are applied in carrying out environmental restoration. These methods are: site assessment, mapping remediation, remediation technologies, thermal absorption, excavation or dredging, SEAR-surfactant, enhanced aquifer remediation, soil vapor extraction and many other technologies.
Site Assessment
Prior to acquiring a land for any development, it is important that you understand what it is you are acquiring. In order to do, Phase 1 and Phase 2 Environmental Site Assessments (ESA) have been put in place in order to evaluate environmental issues at site.
Commercial Purposes
If a site is suspected of being contaminated, there is the need to assess the contamination. Often, the assessments begin with a Phase 1 ESA. The purpose of this ESA is to use a consistent systematic approach to identify any existing or potential environmental conditions that may be present or affect a real estate property. Phase 1 ESA usually involves a review of records, site inspection and interviews with owners, occupants, neighbors and local government officials.
Phase 2 Environmental Site Assessments
Supposing Phase 1 ESA identifies potential contamination of the site by hazardous materials, a Phase 2 ESA may be conducted. This Phase involves sampling and laboratory analysis to confirm the presence of hazardous material. Some of the tests that may be carried out include surficial soil and water samples: subsurface soil borings; ground water monitoring, well installation; sampling and analysis, drum sampling, sampling of dry wells, floor drains and catch basins; transformer/capacitor sampling for polychlorinated biphenyls; geophysical testing for buried tanks and drum testing of underground tanks. Depending on the results of the samples, the Phase 2 ESA should outline site investigation needs and potential actions that may be required to clean up the property. The historical use of the site and the materials used and produced on site will guide the assessment strategy and type of sampling and chemical analysis to be done. Often, nearby sites owned by the same company or which are nearby and have been reclaimed, leveled or filled are also contaminated even where the current land use seems innocuous. Also, important to consider is off-site contamination of nearby sites, often through decades of emissions to soil, groundwater and air.
Mapping Remediation
Those sites that are suspected of contamination can be mapped using several tools such as information TOXMAP, which is a geographic information system from the United States National Library of Medicine that uses maps of the US to help users visually explore data from the United States Environmental Protection Agency Toxics Release Inventory and Superfund programs.
Restoration Technologies
These are usually carried out either at the site or outside the site of contaminations. When done outside the site, methods of treatment involve excavation of the affected area and the treatment done on the surface. On-site treatment is done by treating the contamination without excavation.
Thermal Desorption
This involves the desorber volatizing the contaminants, such as oil, mercury or hydrocarbon to separate them from soil or sludge. The contaminants can then be either collected or destroyed in an off gas treatment system as shown in the diagram below.
Excavation or dredging
This process usually involves the hauling of contaminated soil to a regulated landfill. Supposing the contaminants are volatile organic compounds, the excavated and contaminated soil is aerated. This is illustrated in the diagram below.
Bioaugmentation
This is the process of adding actively growing, specialized microbial strains into a microbial community in an effort to enhance the ability of the microbial community to respond to process fluctuations or to degrade certain compounds, resulting in improved treatment.
Biostimulation
This is the modification of the environment to stimulate existing bacteria capable of bioremediation. This is done by the addition of various forms of rate-limiting nutrients and electron acceptors, such as phosphorous, nitrogen, oxygen and carbon.
SEAR, Surfactant-Enhanced Aquifer Remediation
This method is also known as solubilization and restoration. This involves the injection of hydrocarbon mitigation agents such as Bio Solve Pink water that are attracted to both oil and water...