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Phosphorus

Phosphorus, chemical symbol P, atomic number 15, is one of the 94 naturally occurring elements. It is used in a broad variety of industries and is an essential nutrient to almost every life form on Earth. Phosphorus plays a part in many arenas including chemistry, industry, human health, animal and plant health, crop production, military weapons, the economy, and it is the focus of recent regulatory agency actions in Florida.

PHOSPHORUS IN PLANTS AND ANIMALS

In both animals and plants, phosphorus is an essential component of DNA, RNA, ATP, and phospholipids. The importance of DNA and RNA cannot be overstated. DNA is the molecule in which genetic information is stored, and RNA translates the DNA instructions which dictate the structure and function of each cell. Both plant and animal cells use phosphorus to transfer energy in the form of adenosine triphosphate (ATP). Almost every cellular process obtains the energy needed to function from ATP. Phospholipids make up cellular membranes and allow them to function properly (i.e. keep things out, keep things in, while allowing passage of nutrients in and wastes out). In animals, calcium phosphate salts assist in the hardening of bones.

Phosphorus in the elemental form is rare in nature; it usually occurs combined with other substances as a phosphate molecule. Phosphorus, as phosphate in freshwater, is not harmful to humans. According to the University of Florida: “There is no known level of total phosphorus in waterbodies that poses a direct threat to human health.” [IFAS] That is why sugarcane growers can drink a glass of water from a farm ditch while ridiculing the science behind phosphorus limits and touting the allegedly non-existent “dangers” of their agricultural runoff.

COMMERCIAL USES

The most important commercial use of phosphorus is the production of fertilizers, upon which modern crop production is wholly dependent: there is no synthetically reproducible alternative for phosphorus. Phosphorus is also widely used in explosives, fireworks, tracer ammunition, incendiary bombs, smoke bombs, matches and, ironically, flame retardants. It is also used in nerve agents, pesticides (i.e., the weed killer Roundup), toothpastes, detergents, steel production, specialty glasses, fine china, plasticizers, and water treatment.

EFFECTS IN AQUATIC SYSTEMS

In freshwater surface waters, phosphorus is usually present in such low concentrations that it limits growth of aquatic plants and algae; it is thus frequently called the “limiting factor.” (The Everglades ecosystem is a phosphorus-limited ecosystem.) When all the phosphorus is used up, plant growth ceases, no matter how much nitrogen and other nutrients are present. Available phosphorus is typically scarce because it is attracted to and binds with organic matter and soil particles. Any remaining unattached phosphorus is quickly taken up by algae and aquatic plants.

High concentrations of phosphorus can cause rapid and extensive growth of aquatic plants and algae. Excessive algae and plant growth can lead to depletion of oxygen dissolved in the water. Low dissolved oxygen adversely affects animal populations and fish kills are the most readily observed result. Excessive plant and algae growth can also raise the pH of a water body, altering the ecosystem water chemistry and unbalancing microbial bacteria. High phosphorus concentrations favor the growth of simple algae and plankton over more complicated plants, altering species composition and dominance, markedly reducing species diversity.

The chemical and ecological impacts of high nutrient concentrations can also interfere with recreational and aesthetic water uses by causing reduced water clarity, unpleasant swimming conditions, objectionable odors, blooms of toxic and nontoxic organisms, reduced fish spawning grounds and nursery areas, and interference with boating.

Because phosphorus accumulates in bottom sediments such as deposited clays, silts, and organic matter, a water body may accumulate an “internal phosphorus load.” Subsequent disturbance of bottom sediments releases phosphorus into the water column. Because of this phenomenon, reducing phosphorus input to a water body may not be effective in reducing algal blooms and other phosphorus pollution effects for many years.

The South Florida Water Management District (SFWMD), in its 2009 and 2010 South Florida Environmental Reports, states that, for some of its Water Conservation Areas, high phosphorus loading was expected to continue for decades due to high phosphorus concentration buildup in the soils.

To understand what “high” and “low” phosphorus concentrations are, some sense of scale is essential. Charles Lee (Audubon of Florida) reports that 0.6 parts per billion (ppb) or less is the natural phosphorus concentration in the Everglades; current levels of phosphorus input are more than 200 times that level.

With the creation of the Everglades Agricultural Area, phosphorus began to build up due to the use of fertilizers containing high concentrations of phosphorus and tilling of the soil, which releases phosphorus bound to soil particles. The University of Miami reports that, prior to 1991, water leaving the Everglades Agricultural Area contained approximately 173 ppb total phosphorus and, as of 2002, concentrations had dropped to 77 ppb due to farmers recycling stormwater within their fields and construction of SFWMD’s filter marshes. [MIAMI.EDU] However, SFWMD’s 2010 South Florida Environmental Report states that discharges from the Everglades Agricultural Area to the Everglades in 2009 contained 119 ppb total phosphorus. Drainage from the C-139 agricultural basin, also discharging to the Everglades, contained 256 ppb total phosphorus. EPA’s proposed rules (26 January 2010) set phosphorus limits of 10-50 ppb in lakes, 107 ppb in streams in southern Florida, and 42 ppb in canals.

Nutrient-laden water has devastated the Everglades by changing water chemistry, destroying microbial populations, and causing a remarkable loss of biodiversity. The characteristic sawgrass prairies are being overrun by a monoculture of cattails, which thrive in areas of high nutrient pollution by growing faster than other aquatic plants. The excessive growth of cattails prevents sunlight from reaching a variety of slower-growing aquatic plants, limits access for wading birds and fish, and blocks natural water flows to Florida Bay. Although cattails in South Florida are native, because of elevated phosphorus conditions native cattails function as “invasive” plants. [MIAMI.EDU]

The Everglades ecosystem revolves around water: the quality, quantity, distribution, and timing of that water. As we continue efforts to protect and balance those four water parameters in the Everglades, phosphorus pollution continues to be the most significant cause of water quality degradation.

THE MAGNITUDE OF PHOSPHORUS ISSUES

Discussions associated with phosphorus problems utilize a few common terms, such as “nutrient pollution,” which refers to combined nitrogen and phosphorus. High nutrient concentrations result in a process called “eutrophication,” which simply means becoming enriched with nutrients. Another term, “impaired,” refers to waters identified as not being in compliance with goals mandated in the federal Clean Water Act.

Nitrogen and phosphorus pollution is a well-documented problem across all parts of the U.S. in all types of water bodies (rivers, streams, lakes, reservoirs, estuaries, and coasts). The magnitude of the problem has been known for over a decade. In 2002, EPA reported: “As much as half of the Nation’s waters surveyed by states and tribes do not adequately support aquatic life because of excess nutrients.” [EPA 2002]

Nationally, more than 80,000 miles of streams and rivers are impaired due to nutrient pollution, which is considered a substantial under-estimate because only 25 percent of these water bodies have been assessed. Similarly, over 2.5 million acres of U.S. lakes, reservoirs, and ponds are impaired due to nutrient pollution. But only about 43 percent of these areas have been assessed. Approximately 78 percent of coasts and estuaries in the continental U.S. exhibit symptoms of eutrophication, including excess algal growth, low dissolved oxygen, and loss of seagrasses. Again, that is 78 percent of assessed coasts and estuaries; the total impact of coastal nutrient pollution is expected to be larger. [NITG 2009]

In Florida, waters impaired by nutrient pollution include at least 1,000 miles of streams and rivers, 350,000 acres of lakes, and 900 square miles of estuaries. The actual amount of impairment is believed to be higher because not all streams, lakes, and estuaries have been assessed. In the last 20 to 30 years, nuisance algae species in Florida springs have proliferated and are replacing native submerged vegetation. Nutrient pollution in Florida is the main cause of impairment in lakes, the second-largest cause in estuaries, and the fourth-largest cause for rivers and streams. [EPA 2010]

In a 5 March 2009 report, researchers at Kansas State University calculated that nitrogen and phosphorus pollution cost Americans $4.3 billion annually. The reasons given by the researchers: nutrient pollution forces municipal water plants to use more expensive water treatment; $44 million is spent per year protecting aquatic species from nutrient pollution; hidden costs associated with losses of tourism; and, hidden costs associated with devaluation of waterfront property. [KSU 2009]

SOURCES OF PHOSPHORUS POLLUTION

Sources of phosphorus pollution include both “point” and “non-point” sources. The Nutrient Innovations Task Group (NITG) places nutrient pollution sources into five main categories. All are sources of both nitrogen and phosphorus except No. 3 (Air deposition), which is a source of nitrogen only. The five main source categories are:

1. Urban and suburban stormwater runoff from residential developments, roadways, commercial areas, and fertilization of landscapes, yards, and golf courses.
2. Municipal wastewater treatment plants/publicly owned treatment works (POTWs): there are more than 16,500 municipal POTWs nationwide, but only 9.9 percent have numeric limits for phosphorus. These wastewater treatment plants are considered to be the largest point source of nutrient pollution.
3. Air deposition of nitrogen from the burning of fossil fuels (not a source of phosphorus).
4. Agricultural livestock activities including feedlots, stables, pastures, and manure collection facilities.
5. Agricultural row crops: “Currently, stormwater runoff and irrigation return flow from row crop agriculture are exempt from regulation under the [Clean Water Act] generally and the [National Pollution Discharge Elimination System] program specifically.” [NITG 2009]

PHOSPHORUS SUPPLY AND SECURITY

Phosphorus ore is mined from apatite (phosphorus rock) deposits in the ground, which take millions of years to form. About 50 percent of the known global phosphorus reserves are found in the Arab nations. Other large deposits are found in China, Russia, Morocco, and the U.S. (Florida, Idaho, North Carolina, Tennessee, and Utah). Phosphorus is also present under the oceans, but extracting phosphorus from the sea bed presents currently insurmountable environmental, technological, and financial challenges.

As late as 2007, the general belief was that phosphorus supplies would run out in 345 years. However, a 2008 article in Times Online reported that researchers in Australia, Europe and the United States have warned that phosphorus is “being mined, used and wasted as never before.” Therefore, researchers believe that we will exhaust phosphorus supplies much sooner than previously predicted.

The article cited several examples of recent phosphorus shortages, such as the closing of match factories in India due to a shortage of phosphorus. A senior researcher at the University of Technology in Sydney stated: “Quite simply, without phosphorus, we cannot produce food. At current rates, reserves [of phosphorus] will be depleted in the next 50 to 100 years.” She added: “It is amazing that more attention is not being paid to ensuring phosphorus security.” [Times 2008]

AGENCY ACTIONS

The EPA has the duty under the Clean Water Act (CWA) to regulate phosphorus (or any pollutant) discharged into waters of the United States. One of the main methods of regulating pollutants is the National Pollution Discharge Elimination System (NPDES) permit, which is required for discharges into waters of the U.S. The CWA allows EPA to delegate permitting and enforcement of CWA rules to state governments. However, EPA still retains oversight responsibility in states, like Florida, with the authority to implement CWA programs.

In 1988, EPA sued Florida for violations under the CWA. The resulting 1991 Consent Decree required Florida to establish numeric phosphorus limits in the Everglades. The Florida Legislature proposed a limit of 10 ppb phosphorus for the Everglades, after which followed years of efforts, mainly by sugarcane growers, to challenge the appropriateness of the limit. In 2003, Florida adopted the 10 ppb phosphorus limit for the Everglades. However, then-Governor Jeb Bush passed legislation in 2003 that delayed application of the 10 ppb phosphorus limit until 2016.

A decade after EPA’s lawsuit against Florida, environmental groups sued the EPA for CWA violations. The resulting 1998 Consent Decree required Florida to develop numeric nutrient standards for all surface waters in the state. In 2008, environmental groups again sued the EPA, demanding that EPA set numeric nutrient standards which EPA said were required in 1998 but had still not been promulgated by the state of Florida. This Consent Decree, discussed further below, required EPA to establish numeric nutrient standards if Florida did not propose, and EPA approve, state standards. That got the ball rolling and briefly explains why the EPA, on 26 January 2010, proposed numeric nutrient standards for the state of Florida.

Florida’s current “narrative standard” regarding nitrogen and phosphorus pollution reads, in part: “…in no case shall nutrient concentration of a body of water be altered so as to cause an imbalance in natural populations of flora and fauna.” [FAC 62-302.530] Numerous entities, including EPA, USGS, NITG, a federal judge, and myriad environmental groups, consider this narrative standard to be inadequate. For example:

Conservancy of Southwest Florida: “As shown by the increasing frequency and magnitude of toxic algae outbreaks in both coastal and freshwaters, this standard has been a failure as a means of regulating pollutant sources.” [CSwFl]

EPA, in its recently proposed numeric standards for Florida: “EPA determined that Florida’s reliance on a case-by-case interpretation of its narrative nutrient criterion in implementing an otherwise comprehensive water quality framework of enforceable accountability was insufficient to ensure protection of applicable designated uses.” [EPA 2010]

On 14 January 2009, the EPA formally determined that numeric nutrient standards should be established for Florida. EPA Assistant Administrator for Water, Benjamin Grumbles, explained in a letter to FDEP Secretary, Michael Sole, exactly why EPA found it necessary to establish numeric nutrient standards for Florida. The letter, which provides a good summary of Florida’s current efforts to control nutrient pollution, can be accessed here.

The most recent Consent Decree (19 August 2009) involved the EPA and the groups that sued in federal court: Florida Wildlife Federation, Sierra Club, Conservancy of Southwest Florida, Environmental Confederation of Southwest Florida, and St. Johns Riverkeeper. The court required the EPA to set numeric nutrient standards unless the state of Florida proposed such standards and EPA approved them first. [EPA 2010]

EPA published its proposed numeric nutrient criteria for flowing waters and lakes in the Federal Register on 26 January 2010 and must finalize those criteria by 15 October 2010. Standards for coastal and estuarine waters must be proposed by 15 January 2011 and finalized by 15 October 2011. Florida’s Department of Environmental Protection (FDEP), which has spent nearly $20 million developing nutrient standards allegedly scheduled to be adopted by the end of 2010, has been highly critical of EPA’s proposed numeric nutrient standards.

THE FUTURE OF NUTRIENT STANDARDS

The Nutrient Innovations Task Group (NITG), which consists of EPA and state water managers, was created in 2008 for the purpose of identifying key nutrient pollution issues and options for reducing nutrient pollution at state and national levels. NITG produced a report in August 2009 titled An Urgent Call to Action – Report of the State-EPA Nutrient Innovations Task Group, which was sent with a cover letter to Lisa Jackson, the EPA Administrator appointed by the Obama Administration. In the letter to Ms. Jackson, they state:

As outlined in the enclosed report, the spreading environmental and drinking water supply degradation associated with excess levels of nitrogen and phosphorus in our nation’s waters has been studied and documented extensively. Current efforts to control nutrients have been hard-fought but collectively inadequate at both a statewide and national scale. Concern with the limitations of current nutrient control efforts is compounded by the certain knowledge that as the U.S. population increases by more than 135 million over the next 40 years, the rate and impact of nitrogen and phosphorus pollution will accelerate – potentially diminishing even further progress to date. [NITG 2009]

As part of the introduction in the report, NITG states that

nitrogen and phosphorus pollution has the potential to become one of the costliest, most difficult environmental problems we face in the 21st century.

That statement should probably be read twice to more fully comprehend its impact.

The report includes documentation of the size and scope of nutrient pollution in the U.S., and summarizes the methods by which state and national agencies are currently handling the issues. One conclusion:

Over the past decade, there have been numerous major reports, a substantially large number of national and international scientific studies, and a growing number of quantitative analyses and surveys at the state and national levels indicating that we are falling behind.

The Task Group believes that national numeric standards are needed to prevent one state with strict nutrient standards from losing business to a state with less rigorous standards. The group also points out that national standards are needed to prevent strict controls for some nutrient pollution sources, while ignoring or being less strict with other sources. They conclude: “Combating the challenge of widespread nutrient pollution will require a renewed emphasis on prevention and a profound change in how we share accountability and responsibility between sources, within watersheds, and across state lines.” The Task Group believes only national leadership can accomplish this.

The report does not ignore economic realities and states openly that taking control of our nutrient pollution will be expensive. However, the Task Group believes that the costs of implementing a national nutrient pollution control system would be small compared to the benefits attainable by such a program. These benefits would include reduced health care costs, reduced drinking water treatment costs, increased recreational opportunities, increased property values, and increased abundance and diversity of fish and shellfish.

And finally, the last line of the 34-page report reads:

In short, urgent action is needed.

As water quality continues to degrade, more environmental groups will sue the EPA in order to force federal or state action to control nutrient pollution. It is likely that EPA will, instead of being sued repeatedly, eventually implement national nutrient pollution standards. Whether that will happen sooner or later is anybody’s guess.

A note about spelling: those of us who are not chemists should stick to the normal spelling, PHOSPHORUS. However, the word PHOSPHOROUS does exist as an adjective referring to the tri-valent form of phosphorus; just as sulfur forms sulfurous and sulfuric compounds, so does phosphorus form phoshorous and phosphoric compounds.

Michael S. Hubbard
March 2010

Sources and Additional Information

CSwFl Conservancy of Southwest Florida, undated. Numeric Nutrient Standards Q & A Fact Sheet. http://news/caloosahatchee/org/docs/Numeric_Nutrient_Standaards_Fact_Sheet.pdf

EPA 2002 Environmental Protection Agency, October 2002. Fact Sheet – Ecoregional Nutrient Criteria. www.epa.gov/waterscience/criteria/nutrient/ecoregions/files/jan03fmfs.pdf

EPA 2009 Environmental Protection Agency, January 2009. Letter to Michael Sole, Secretary, Florida Department of Environmental Protection. www.dep.state.fl.us/WATER/wqssp/nutrients/docs/benjamin_grimbles_epa_01142009.pdf

EPA 2010 Federal Register, Tuesday, January 26, 2010. Part III, Environmental Protection Agency, 40 CFR Part 131. Water Quality Standards for the State of Florida’s Lakes and Flowing Waters; Proposed Rule.

IFAS University of Florida, Institute of Food and Agricultural Resources, 2003. Plant
Management in Florida Waters. http://plants.ifas.ufl.edu/guide/totpho.html

KSU 2009 Imbrium News Release, March 2009. Phosphorus/nitrogen pollution costs Americans $4.3 billion each year. www.imbriumsystems.com/pdf/Phos_pollution_Mar09.pdf

MIAMI.EDU University of Miami, School of Communication, undated. Phosphorus in the Everglades. http://viscom.miami.edu/oasis/Phosphorus.html

NITG 2009 State-EPA Nutrient Innovations Task Group, August 2009. An Urgent Call to Action – Report of the State-EPA Nutrient Innovations Task Group. www.epa.gov/waterscience/criteria/nutrient/nitgreport.pdf

TIMES 2008 Times Online, June 2008. Scientists warn of lack of vital phosphorus as biofuels raise demand. http://business.timesonline.co.uk/tol/business/industry_sectors/natural_resources/article4193017

Audubon of Florida, undated. Cleaning up Phosphorus Pollution in the Everglades & the 10 ppb Phosphorus Standard. www.audubonofflorida.org/PDFs/pubs_policydocs_Everglades_phosphorus.pdf

Environmental Protection Agency, undated. Why is phosphorus important?
www.epa.gov/volunteer/stream/vms56.html

Michigan Department of Environmental Quality, undated. Phosphorus. www.michigan.gov/documents/deq/wb_npdes_Phosphorus_247234_7.pdf

South Florida Water Management District, 2010. 2010 South Florida Environmental Report. www.sfwmd.gov/portal/page/portal/pg_grp_sfwmd_sfer/pg_sfwmd_sfer_home

South Florida Water Management District, undated. Environmental Restoration Efforts
www.sfwmd.gov/portal/page/portal/pg_grp_sfwmd_watershed/portlet%20-%20watershed%20management/tab179604/env_rest_efforts.pdf

Wikipedia, undated. Eutrophication. http://en.wikipedia.org/wiki/Eutrophication

Wikipedia, undated. Phosphorus. http://en.wikipedia.org/wiki/Phosphorus