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Reports & Essays: Science - Earth

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Nitrate Contamination of Groundwater Poses A Serious Health
Threat Nitrates contamination of the world's underground water supply poses as a potentially serious health hazard to the human inhabitants on earth. High nitrate levels found in well water has been proven to be the cause for numerous health conditions across the globe. If we intend to provide for the future survival of man, and life on planet earth, we must take action now to assure the quality of one of our most precious resources, our underground water supply. Ground water can be defined as the water stored in the open spaces within underground rocks and unconsolidated material (Monroe and Wicander 420). Ground water is one of the numerous parts that make up the hydrologic cycle. The primary source of water in underground aquifers is precipitation that infiltrates the ground and moves through the soil and pore spaces of rocks (Monroe and Wicander 420). There are also other sources that add water to the underground aquifer that include: water infiltrating from lakes and streams, recharge ponds, and wastewater treatment systems. As groundwater moves through the soil, sediment, and rocks, many of its impurities are filtered out. Take note, however, that some, not all, soils and rocks are good filters. Some are better than others and in some cases, serious pollutants are not removed from the water before it reaches the underground supply. Now that we have a good working definition of what groundwater is, and where it comes from, just how important is it? Groundwater makes up about 22% of the worlds supply of fresh water. Right now, groundwater accounts for 20% of all the water used annually in the United States. On a national average, a little more than 65% of the groundwater in the United States each year goes to irrigation, with industrial use second, and third is domestic use (Monroe and Wicander 420). Some states are more dependent on groundwater for drinking than others. Nebraska and the corn belt states rely on underground water for 85% of their drinking needs, and in Florida 90% of all drinking water comes from underground aquifers (Funk and Wagnall 2). People on the average in the United States require more than 50 gallons of water each day for personal and household uses. These include drinking, washing, preparing meals and removing waste. A bath in a bathtub uses approximately 25 gallons of water and a shower uses about l5 gallons per minute of water flow while the shower runs. Just to sustain human tissue requires about 2.5 quarts of water per day. Most people drink about a quart of water per day, getting the rest of the water they need from food content. Most of the foods we eat are comprised mostly of water: for example, eggs, are about 74% water, watermelon 92%, and a piece of lean meat about 70%. Most of the beverages we drink are also mostly comprised of water, like milk, coffee, tea and soft drinks. And the single largest consumer of water in the United States, is agriculture. In dry areas, farmers must irrigate their lands to grow crops. It is estimated that in the United States, more than 100 billion gallons of fresh water are used each day for the irrigation of croplands (Funk and Wagnall 2). Since agriculture is the leading user of our groundwater, perhaps it is fitting, that it is also the biggest contributor of contaminating nitrates that work into our water supply each year. Agriculture and livestock production account for 80% of all nitrogen added to the environment ( Terry, et al. 1996). Industrial fertilizers make up 53%, animal manure 27%, atmosphere 14%, and point source 6% (Puckett, 1994). Just how do these nitrates get from the field into our water supply? There are two primary reasons that nitrate contaminates reach our underground water supply and make it unsafe. Number one reason is farmer's bad habits of consistently over- fertilizing and applying too much nitrogen to the soil. In 1995 America's agricultural producers added 36 billion pounds of nitrogen into the environment, 23 billion pounds of supplemental industrial nitrogen, and 13 billion pounds of extra nitrogen in the form of animal manure. Twenty percent of this nitrogen was not used by the crops it was intended. This accounts for about 7-8 billion pounds of excess nitrogen remaining in the environment where much of it has eventually entered the reservoirs, rivers, and groundwater that supply us with our drinking water (NAS 1995). The number two reason these contaminants reach our groundwater supply runs parallel with the first. Over-irrigation causes the leaching of these nitrates past the plants root zone where they can be taken in by crops and used effectively. Not all soils are the same and all have different drainage characteristics. Soils with as higher amount of sand and gravel are going to filter liquids down to the aquifer faster than soils comprised of more silty finer sorted particles. Today's farmers not only need to know when it is time to irrigate, they also need to know how much and for how long. When the two problems are added together, over-fertilization, and over-irrigation, the potential for harmful nitrate contamination runs terrifyingly high. Just how harmful are nitrates in our drinking water? Nitrates levels that exceed the Federal standard level of 10 parts per million can cause a condition known as Methemoglobinemia, or Blue Baby Syndrome in infants. Symptoms of Methemoglobinemia include anoxic appearance, shortness of breath, nausea, vomiting, diarrhea, lethargy, and in more extreme cases, loss of consciousness and even death. Approximately seven to ten percent of Blue Baby Syndrome cases result in death of the infant (HAS 1977, Johnson et al. 1987). When nitrate is ingested it is converted into another chemical form, nitrate. Nitrate then reacts with hemoglobin, the proteins responsible for transporting oxygen in the body, converting them to methemoglobin, a form that is incapable of carrying oxygen. As a result, the victim suffers from oxygen deprivation, or more commonly stated, the individual slowly suffocates (HAS 1977, Johnson et al. 1987). Although, Methemoglobinemia is the most immediate life-threatening effect of nitrate exposure, there are a number of equally serious longer-term, chronic impacts. In numerous studies, exposure to high levels of nitrate in drinking water has been linked to a variety of effects ranging from hypertrophy (enlargement of the thyroid) to 15 types of cancer, two kinds of birth defects, and even hypertension (Mirvish 1991). Since 1976 there have been at least 8 different epidemeology studies conducted in 11 different countries that show a definite relationship between increasing rates of stomach cancer and increasing nitrate intake (Hartmann, 1983; Mirvish 1983). The facts speak for themselves, increasing levels of nitrates in our groundwater are slowly poisoning our society. We have only discussed contamination of our groundwater supply by nitrates through the misuse of resources involved in agriculture. Be aware that there are hundreds of other substances and practices that add to the further contamination of our groundwater every day. Time does not allow for an in-depth analysis of all aquifer contaminates in this paper, however, I would like to mention a few that are at the top of the list just briefly. Storm water runoff. Streets and parking lots contain many pollutants including oils, greases, heavy metals and coliform, that can enter groundwater directly through sinkholes and drainage wells. Pesticides and herbicides can end up in the water supply much the same way as do nitrates. Septic tanks that are improperly or poorly maintained, can contaminate groundwater. Underground storage tanks, hazardous wastesites, landfills, abandoned wells, accidents and illegal dumping all threaten the quality of our drinking water. We must be aware of the potential hazards and take measures to ensure the safety of our drinking water supply for generations to come. What can we do to prevent unnecessary contamination of our groundwater? Farmers will and must continue to use nitrogen fertilizer. They do not, however, need to overuse it. By following a few simple guidelines, such as accounting for all sources of nitrogen in the system, refining estimates of crop nitrogen requirements, synchronizing application of nitrogen with crop needs, using nitrogen soil tests, and practicing good water management, farmers can not only help keep our aquifers safe from contamination, but can probably enjoy the same yields as before and spend less money on fertilizer, thus increasing their net profits, (Halberg et al. 1991, Iowa State University 1993). How about the rest of us? What can we do to help drinking water safe? There are many hazardous substances around the house that frequently need disposal. Please don't dump them on the ground, pour them down the drain, and always use fertilizers and chemicals in moderation. Take proper care and maintenance of your septic system at all times. Finally, when in doubt, ask. Many areas have local Amnesty Days. For information or to request an Amnesty Day, call your local public works department. Nitrate contamination poses a serious health threat to all of us. Each of us uses a little more than 50 gallons of fresh water every day. When all our fresh water is contaminated beyond use, our world will not be a pleasant environment to live in. We must all act now to maintain a fresh water system that will be capable of sustaining us, and many generations into the future.

 



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