Term Paper: Fertilizers Affects on Aquatic Life

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¶ … Chemical Fertilizers on Aquatic Life

Following World War II, innovations in fertilizer production resulted in an explosion in their use. To date, chemical fertilizers have been credited with saving millions of people around the world from starvation, but the accumulated impact of their continued use on aquatic life in surrounding areas has been the source of an increasing amount of concern from the scientific community in recent years. Because the world's water supplies are finite, it is important to recognize and act on these potential threats today before it is too late. To this end, this paper provides an overview of water systems and how they function, followed by a discussion of the different types of chemical fertilizers in use today. An analysis of the impact of chemical fertilizers on aquatic life is followed by an assessment of current and future trends in chemical fertilizer use and their impact on the world's water systems and aquatic life. A summary of the research and salient findings are presented in the conclusion.

Review and Discussion.

Background and Overview. Ordinarily, water systems are naturally self-cleansing by using oxygen to break down the organic pollutants that enter these systems into benign or inoffensive forms; however, when too much of any type of waste enters a water system, the natural purification processes are diminished and the water becomes unsuitable for a variety of human needs (Henning & Mangun 251). Today, waterborne sewage is comprised primarily of various types of wastes, heavy metals, and toxic substances such as pesticides and chemical fertilizers and the major pollution sources are municipalities, industries, and agriculture, especially hog farms (Henning & Mangun 251).

The quality of water systems is determined by the degree to which bodies of water are able to support aquatic life while also meeting standards for the protection of human health and the preservation of human life; this level of contamination is determined by establishing baseline standards to measure the periodic relative quality of each individual water system against these original standards (Henning & Mangun 251). Attempts to either maintain or restore the quality of the water in these systems are developed according to the amounts and kinds of material that are emptied into the waterways; the quality of water in streams, rivers, lakes and oceans therefore depends on the capacity of each of these water systems to clean themselves of the various pollutants. According to Henning and Mangun, this ability depends on the types and amounts of the pollutants as well as with water temperatures, rate of water flow, degree of sedimentation, and mineral content (251). The mineral content of pollutants containing chemical fertilizers already account for the lion's share of the nitrogen being released into the world's water systems, but there are other elements involved in modern chemical fertilizers as well, and these are discussed further below.

Types and Uses of Chemical Fertilizer. Modern chemical fertilizers are typically formulated from a combination of one or more of three basic elements: (a) nitrogen, (b) phosphorus, and -; many such fertilizers also contain secondary ingredients in the form of the elements sulfur, magnesium, and calcium (Fertilizer 2006). Chemical fertilizers are accounting for an increasingly large share of the total pollutants being discharged into the world's water systems. Inexpensive methods for synthesizing ammonia were identified after World War II, resulting in the mass production of artificial fertilizer in what the ecologist and nitrogen expert David Tilman has termed "the 35 most glorious years of agricultural production" (quoted in Nierenberg at 30). According to this author, farmers in industrialized countries as well as those in developing countries as well have access to inexpensive and almost limitless quantities of chemical fertilizers; because these products are cheap, though, much of it is wasted: "Fertilizer is often very inefficiently applied; much of it never reaches the crop. It leaches out of the fields and into the streams, or it's converted into a nitrogenous gas like nitrous oxide and escapes into the atmosphere" (Nierenberg 30). The impact of these increasing discharges of chemical fertilizers into the world's water systems is discussed further below.

Impact of Chemical Fertilizers on Aquatic Life. The increase in the global population has been accompanied by a concomitant increase in the use of chemical fertilizers in more intensive forms of agriculture. "These developments, however, have placed unprecedented pressures and stresses on the world's ecosystems which has a destructive impact on plants, forests, and aquatic life in lakes and rivers" (Coming to Terms with Sustainability 6). The majority of the millions of tons of fixed nitrogen that is discharged into the world's water supplies, approximately 120 million tons, comes from agriculture, but these are unprecedented levels; Table 1 and Figure 1 below provide a breakdown of the amount of chemical fertilizers currently being discharged into the world's water supplies as a component of total manmade sources.

Table 1.

Annual releases of fixed nitrogen caused by human activity.

Source

Millions of tons

Fertilizer

Nitrogen-fixing crops

Fossil fuels

Biomass burning

Wetland drainage

Land clearing

Total human releases

Total natural fixed-nitrogen production *

Terrestrial sources only; marine sources have not yet been reliably estimated.

Source: Nierenberg 30.

Figure 1. Annual releases of fixed nitrogen caused by human activity.

Source: Based on data in Nierenberg at 30.

As can be seen from Table 1 and Figure 1 above, fertilizers account the majority of nitrogen-fixing activity today. According to Nierenberg (2001), "Nitrogen-fixing crops produce about a third of that amount; the rest comes from artificial fertilizer. Fixed nitrogen is the basic component of fertilizer. Through its dependence on artificial fertilizer, modern conventional agriculture has become, in a sense, a form of industrial nitrogen management. This is a relatively recent development in agricultural history" (30). One outcome of this increase in nitrogen in the world's water systems is so-called "red time"; Backer, Baden and Fleming (2005) report that Florida red tide is caused by Karenia brevis, a dinoflagellate that blooms periodically and releases a powerful neurotoxin, brevetoxin, into the surrounding waters and air along the coast of the Gulf of Mexico. According to these authors, "Exposure to Florida red tide toxins has been associated with adverse human health effects and massive fish and marine mammal deaths" (Backer et al. 618).

The chemical impact of some nitrogen pollution, though, is less discernible than these algal blooms, but they may be even more dangerous for aquatic life. For instance, Nierenberg reports that, "Waters that become increasingly acidic support fewer forms of aquatic life. That's partly because the acid releases aluminum ions from the mineral matrix in which they are usually embedded. Free aluminum is toxic to plants -- and to many aquatic organisms if it washes into streams" (30). Unfortunately, it would seem that things are going to get worse before they get better, and these issues are discussed further below.

Current and Future Trends. Not surprisingly, based on the continued explosive growth of chemical fertilizers, almost all crops that are grown in the industrialized countries today are nitrogen-saturated; in other words, these crops are being exposed to more nitrogen than they can metabolize (Nierenberg 30). Nevertheless, chemical fertilizer production continues to increase in response to growing global demand; in fact, at current rates of production, fertilizer is adding some at least 80 million tons of fixed nitrogen to the cycle and by 2020, that discharge is estimated to reach 134 million tons, a total that is just 6 million tons short of representing the total input from all natural terrestrial sources combined (Neirenberg 30). The explosive growth of the world's population in recent years has not created a Malthusian crisis - yet, but the handwriting is on the wall. The earth is running out of sustainable crop land and the use of chemical fertilizers in the future can logically be expected to increase and their… [END OF PREVIEW]

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