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| 9/2/2009 10:35:00 AM Email this article • Print this article |
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Cornell researcher Douglas Haith, in front of Cayuga Lake, has been a part of recent studies into phosphorous pollution in the lake. (Photo by Rachel Philipson) |
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Cornell researchers examine sources of pollution
- Bill Chaisson
This is the third in a continuing series of articles on the problem of phosphorus pollution in the southern end of Cayuga Lake and the apparent consequence of rampant plant and algae growth. Recent local coverage and opinion has largely focused on the Cornell Lake Source Cooling (LSC) discharge as the culprit in the absence of any evidence other than disputed statistical analyses.
In the first article ("Pollution Patrol," Ithaca Times, July 22, 2009) Steve Penningroth of the Community Science Institute cited data that showed the LSC discharge includes lower concentrations of phosphorus than the wastewater treatment plants. Walter Hang of Toxic Targets maintained that LSC was one point source to many in a challenged lake environment.
In the second article ("DEC engineer weighs in on Lake Source Cooling," Ithaca Times, Aug. 12, 2009) environmental engineer Cliff Callinan maintained that the worsening of the lake environment since the inception of LSC and the statistical analysis used by the DEC in a before/after study point toward the LSC discharge as the culprit.
An email and a phone call to Todd Cowen, a Cornell research engineer monitoring water conditions at the south end of Cayuga Lake, were not returned.
Two recent studies by Cornell researchers have examined the extent of non-point sources of phosphorus and other pollutants in Cayuga Lake. "Point sources" of pollutants are those that can be narrowed down to a specific location, such as an outfall pipe or a buried gas tank. "Non-point sources" are more diffuse; the collective input of many acres becomes concentrated as it moves from source to sink. In the case of phosphorus, the Cayuga Lake watershed is the source and the lake itself is the sink.
A paper by Zachary M. Easton (biological and environmental engineering) and A. Martin Petrovic (horticulture department) uses data collected in urban and rural portions of the Fall Creek drainage to show levels of phosphorus input from areas with different land uses. The phosphorus levels are higher from disturbed and urban areas, but they comprise a much smaller percentage of the watershed than does agricultural land, which accounts for xx percent of the Fall Creek watershed.
A study by Douglas Haith, Nicholas Hollingshead, Matthew L. Bell, Stephen W. Kreszewski, and Sara J. Morey (Department of Biological and Environmental Engineering) models the input of phosphorus and nitrogen compounds from the entire watershed into Cayuga Lake. (The text of this paper is available for download at the Web site of the Cayuga Lake Watershed Network (www.cayugalake.org).) Haith and his coworkers noted that the Cayuga Lake Watershed covers 1871 square kilometers, and overall land uses are 52 percent agriculture, 34 percent forest and brush, 12 percent urban and the remaining 2 percent other rural uses, such as water, abandoned, barren and disturbed land areas. Their stated objective was to determine sediment and nutrient loads from both point and non-point sources, both their magnitude and their spatial distribution.
Cornell's Lake Source Cooling was mentioned exactly once in Haith's 107-page report: "The Draft Cayuga Lake Watershed Restoration and Protection Plan (Genesee/FingerLakes Regional Planning Council, 2001) estimated mean annual TP loads from these tributaries plus the Ithaca and Cayuga Heights wastewater treatment plants and Cornell University's lake source cooling outlet as 18 megagrams per year." Haith et al.'s model estimated that point sources contribute only 7 megagrams per year and that agricultural land contributes 26 megagrams per year.
Haith does not think that LSC is a significant phosphorus-loading factor. "It's moving phosphorus from the bottom to the top, so it doesn't have an impact in terms of load," he explained. "Anything that big will have an environmental impact, but non-point sources have a significantly larger impact than point sources." In Table 23 of the Haith et al. paper the GWLF (generalized watershed loading functions) model estimates that 50 percent of the load of total phosphorus is derived from agriculture in the Fall Creek watershed (a non-point source), while all point sources in the watershed, which includes the Cayuga Heights wastewater treatment plant, constitute nine percent of the load of total phosphorus.
Can the phosphorus load from non-point sources be reduced? "In principle the biggest thing is to control erosion," said Haith, "but Cayuga [watershed] farmers are already doing that. Erosion control is pretty advanced around here. Another thing that could be done is to entirely eliminate winter manure spreading." Because the ground is frozen a large portion of manure spread during colder months simple get incorporated into runoff on warm winter days.
Different land uses contribute varying amounts of phosphorus to the lake water. Agriculture, because it constitutes the single most widespread land use in the watershed is responsible for most of the dissolved phosphorus (44.8 percent) and total phosphorus (47.0 percent) that goes into Cayuga Lake. Dissolved or "soluble reactive" phosphorus (SRP) consists of particles smaller than 0.45 microns and is made up largely of inorganic orthophosphate, the form of phosphorus most readily taken up by algae (but not higher plants). SRP, along with the soluble unreactive fraction (largely organic matter smaller than 0.45 microns) and particulate phosphorus, add up to "total phosphorus."
All point sources to Cayuga Lake combined are estimated to contribute 12.2 percent of the SRP and 7.2 percent of the total phosphorus load. Urban areas, which make up only seven percent of the entire watershed contribute nothing to the SRP load, but add up to 12.5 percent of the total phosphorus load.
"Anything that accumulates on [impervious] surfaces [in an urban area] is primarily organic matter," explained Haith. When it rains, this accumulated organic load and its phosphorus component wash down into storm drains and out into the lake. "You also have run-off from lawns and pet droppings contribute a significant amount [of phosphorus]."
Another significant source of the total phosphorus load is "disturbed land," which includes any non-agricultural site where the vegetation has been removed, often through construction. "That's an erosion problem," said Haith. "There are regulations to control it, but you're just tearing the cover off." The recent efforts in Tompkins County to prevent development on steep slopes along the lake stem are motivated by attempts to control erosion and loading of the nutrients (phosphorus and nitrogen) that are adsorbed to the sediment particles into creeks and the lake.
Easton and Petrovic's paper appeared in The Fate of Nutrients and Pesticides in Urban Environments (Oxford University Press, 2008). They looked at a single, largely urban subwatershed in the Ithaca area. Their multi-variate statistical analysis showed that fertilized lawns were the land use that contributed the largest portion of dissolved phosphorus (SRP) to streams when runoff was high, but contributed very little when runoff was low. Their data verified the GWLF model's conclusion that barren urban surface are significant contributors of total phosphorus to streams. Like Haith, Easton and Petrovic conclude that reducing runoff is the best way to reduce phosphorus loading from non-point sources.
Easton and Petrovic found that most of the variation in phosphorus loading was caused by changes in the amount of runoff and streamflow, not changes in the concentrations of phosphorus in the runoff. This speaks to the concerns that have been voiced by Jose Lozano, director of the Ithaca wastewater treatment plant, and others, who have noted that LSC outfall represents approximately 30 percent of flow into the lake during July, August and September, when streamflow is at a low for the year and algae blooms are most intense in the lake.
Easton and Petrovic also note most of the phosphorus from fertilized lawns is in the form of SRP. They found that SRP levels were highest in the fall, when the soil was wetter and uptake by plants was declining with decreasing temperatures.
They conclude that improved stormwater management should significant reduce phosphorus loading from urban areas and that phosphorus runoff from lawns would be greatly reduced if people would only fertilize them when they actually needed it.
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Suicide has recently come to Ithaca in a very public, and at times controversial, way. This past academic year, after three years with no suicides, Cornell experienced what is known in the scientific community as a "suicide cluster." OK, so maybe you're like me and you thought this whole JetBlue flight attendant story was good for maybe one news cycle.  |
