Introduction:
Nutrient contamination, caused by excess nitrogen in the air and water, is one of America's most pervasive and costly environmental issues. Nitrogen is a naturally occurring nutrient in aquatic habitats, and it is the most abundant element in the air we breathe. Nitrogen promotes the growth of algae and aquatic plants, which offer food and shelter for fish, shellfish, and other aquatic creatures. However, when too much nitrogen enters the environment, usually through human activity, the air and water can become polluted. The human-caused sources include fossil fuels, fertilizers, and sewage. For several decades, nutrient pollution has adversely affected many lakes, rivers, streams, bays, and coastal waters, causing significant environmental and human health consequences as well as economic impacts. When too much nitrogen is in the water, algae grows faster than ecosystems can manage. Significant increases in algae affect water quality, food resources, and habitats, and reduce the oxygen required by fish and other aquatic life.
There are two main measures which can be used to for reduce nitrogen in waterbodies: stopping nitrogen from entering waterways in the first place and denitrifying the already contaminated water.
History:
Anthropocentric sources have caused a huge disturbance in the global cycle of nitrogen. The three main causes of nitrogen pollution in the hydrosphere are cultivation-induced mineralization of soil nitrogen, fertilizer, and animal or sewage waste.
Agricultural fertilizers are one of the main contributors to nitrogen pollution in water bodies. These fertilizers are produced to be rich in nitrogen, which induces plant growth to feed the increasing global population. As the population increases, more food is necessary to sustain current-day human health. “Nitrogen (N) fertilizer has made a substantial contribution to the tripling of global food production over the past 50 years. World grain production was 631 million tons in 1950 (247 kg person -1 ) and 1840 million tons in 2000 (303 kg person -1 ); per capita grain production peaked in 1984 at 342 kg person” (Mosier et al.). The correlation between food production and nitrogen pollution is extremely strong and only gets worse as time goes on due to increased global populations. On the other hand, nitrogen-rich fertilizers were a huge technological advancement for developed nations, and many economies now rely on these fertilizers for the adequate production of agricultural crops. This makes fertilizers difficult to rule out when it comes to environmental protection regulations. Ammonia synthesis (how inorganic fertilizers are made) is regarded as one of the greatest scientific discoveries of the twentieth century, earning two Nobel Prizes in Chemistry to two German chemists: Fitzgerald Haber in 1919 and Carl Bosch in 1931 (Prasad and Shivay). Ammonia synthesis is the method that transforms nitrogen into a bioavailable substance; without it, we wouldn't have our current-day fertilizers and other nitrogen-based products.
Animal sewage is another issue that causes nitrogen pollution in waterways. New York State produced 85,755,000 kg of nitrogen in 2007 due to agricultural manure. Surface and groundwater systems frequently get polluted with manure runoff from farmland, pastures, or concentrated animal feeding operations (CAFOs) via infiltration or surface runoff. “Nitrogen (N) availability from applied manure includes the inorganic N (NO3-N and NH4-N) in manure plus the amount of organic N mineralized following application. Nitrogen mineralization differs for different manure types since the inorganic/organic fraction and quality of organic N varies among manure types. Mineralization of organic N is expected to be low for composted manure (∼ 18%) and high for swine or poultry (hens) manure (∼ 55%)” (Eghball, B., et al). This being said, when animal manure from cattle farms gets washed away by rain, all of the nitrogen (and other nutrients) from the manure gets into our waterbodies and pollutes them.
The Problem:
The most critical impact nitrogen pollution has is on water quality. Nitrogen is the nutrient that limits biological productivity the most in estuaries as well as other enclosed waterbodies. Excessive nitrogen causes eutrophication, which is when bodies of water become polluted with excess nutrients. This causes “the excessive growth of algae and macrophytes, the resulting oxygen depletion, and the production of a range of substances toxic to fish, cattle, and humans are now major pollution problems worldwide” (Mosier et al.). The increased biomass of plants and animals that are supported in the nutrient-loaded ecosystem results in more respiration, which contributes to some of the rises in oxygen demand. The majority is frequently caused in large part by bacteria that eat the organic materials created by the increased plant output. This causes hypoxia or anoxia to occur, “Biologists generally refer to the situation where some oxygen is present but where dissolved oxygen levels are less than or equal to 2.0 milligrams per liter (mg l – 1 ) as hypoxia. Anoxia is the complete absence of oxygen” (National Research Council, et al). Reduced oxygen zones can interfere with the migratory patterns of benthic and demersal species, impede the growth and recruitment of species, and result in significant kills of fish and invertebrates that are crucial for the ecosystem as well as our economy. Many states have standards for dissolved oxygen in marine systems which prevent hypoxia and low oxygen levels, but these mandates tend to only focus on areas that are commonly fished, which leaves other waterbodies susceptible to these conditions. One of the more notable examples of this is in the Gulf of Mexico, where there is a “dead zone” that is approximately 20,000 km^2. The “dead zone” has been expanding in size since the 1950s, as greater amounts of nutrients from human activities are loaded into the Gulf of Mexico via the Mississippi and Atchafalaya Rivers. “Nutrient overenrichment can cause individual organisms to experience a range of be-havioral and physiological impacts including reductions in fitness or reproductive capacity, increased mortality from predation, low oxygen, and often toxic hydrogen sulfide in anoxic (i.e., no-oxygen) bottom waters” (Gassman et. al.). This shows that due to an abundance of nitrogen enrichment in waterbodies, there are many ecological as well as economic devastations.
The Solution:
There are two main categories for reducing nitrogen in waterbodies, the first being preventative measures to reduce nitrogen-containing runoff. This includes creating laws and regulations on the sources of these pollutants; nitrogen-based fertilizers and manure. Many organic farmers have learned the defects of using nitrogen-based fertilizers but continue to use them in order to sustain their livelihood. As a result, there have been multiple methods created in order to decrease fertilizer use and the overall runoff amount. Some of these techniques include crop covering (using sheets to cover crops to protect the sensitive topsoil from being washed away by rain) and direct fertilization (putting the fertilizer in specific, measured amounts only where it needs to be instead of spreading it across the whole field). There is also the no-tillage method; tilling is a method that gets rid of weeds in the topsoil after harvesting, but it also makes the soil loose and easily transportable by heavy rain. Instead, they focus on more sustainable methods like cover cropping, as mentioned earlier, and contour farming.
When it comes to manure, there are not too many regulations on what cattle farms have to do with their access to manure, which means there are lots of methods that can be improved when it comes to that industry. Firstly, developing new markets in which manure can be used would reduce the abundance of manure the global economy currently produces. This can include shipping manure globally to areas of less fertile land. It could also be used to restore old farmlands and soils that were stripped of their nutrients. There are also many controversies with the meat industry in general, with many environmentalists wanting there to be more regulations for population control on animal agriculture farms. More regulations and standards need to be set into place both locally and especially country-wide.
The second category for reducing nitrogen in waterbodies is a more complicated process; denitrifying the nitrogen that's already in the water. With a mixture of autotrophic and heterotrophic bacteria, activated sludge processes are frequently developed and utilized to achieve both nitrification and denitrification in a single system. “The main configuration is the two stage activated sludge process (Modified Ludzack Ettinger) which combines an anoxic bioreactor followed by an aerobic bioreactor and a secondary clarifier (Figure 5.1). Sludge is pumped from the bottom of the clarifier to the anoxic stage with a flow of 50% to 100% of the influent flow. In addition, an internal recirculation of mixed liquor is imposed from the aerobic to the anoxic reactor for recycling nitrate produced by nitrification to the anoxic pre-denitrification zone” (“Environmental Technologies to Treat Nitrogen Pollution”). This method is optimal for wastewater but it can be altered to function in all types of different situations.
Conclusion:
One of the most ubiquitous and expensive environmental problems in America is nutrient pollution, which is brought on by too much nitrogen in natural water bodies. Nitrogen is an element that promotes growth, especially in algae blooms and bacteria, but that indirectly makes it a limiting factor. An increase in algae and bacteria creates “dead zones” all across the globe, which has devastating effects on marine organisms, especially those that can not escape these zones of little oxygen. The excess nitrogen is due to anthropocentric sources, although there are ways to limit nitrogen runoff and clean up existing polluted areas.
Citations:
Environmental Technologies to Treat Nitrogen Pollution, edited by Francisco J. Cervantes, IWA Publishing, 2009. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/buffalo/detail.action?docID=3120651.
Created from Buffalo on 2023-04-19 17:29:01.
Agriculture and the Nitrogen Cycle : Assessing the Impacts of Fertilizer Use on Food Production and the Environment, edited by Arvin Mosier, et al., Island Press, 2004. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/buffalo/detail.action?docID=3317459.
Created from on 2023-04-19 18:07:55.
Prasad, R., Shivay, Y.S. A Brief History of the Fertilizer Nitrogen. Indian J Hist. Sci. 56, 60–64 (2021). https://doi.org/10.1007/s43539-021-00006-0
US EPA, OW. “Estimated Animal Agriculture Nitrogen and Phosphorus from Manure.” US EPA, 26 Mar. 2013, www.epa.gov/nutrient-policy-data/estimated-animal-agriculture-nitrogen-and-phosphorus-manure.
National, Research Council, et al. Clean Coastal Waters : Understanding and Reducing the Effects of Nutrient Pollution, National Academies Press, 2000. ProQuest Ebook Central, https://ebookcentral-proquest-com.gate.lib.buffalo.edu/lib/buffalo/detail.action?docID=3375525.
Eghball, B., et al. “Mineralization of Manure Nutrients.” Journal of Soil and Water Conservation, vol. 57, no. 6, 1 Nov. 2002, pp. 470–473, www.jswconline.org/content/57/6/470.short.
Dodds, W.K. (2006), Nutrients and the “dead zone”: the link between nutrient ratios and dissolved oxygen in the northern Gulf of Mexico. Frontiers in Ecology and the Environment, 4: 211-217. https://doi.org/10.1890/1540-9295(2006)004[0211:NATDZT]2.0.CO;2
S. S. Rabotyagov, C. L. Kling, P. W. Gassman, N. N. Rabalais, and R. E. Turner
Review of Environmental Economics and Policy 2014 8:1, 58-79
Environmental Technologies to Treat Nitrogen Pollution, edited by Francisco J. Cervantes, IWA Publishing, 2009. ProQuest Ebook Central, https://ebookcentral-proquest-com.gate.lib.buffalo.edu/lib/buffalo/detail.action?docID=3120651.
