Wingra Watershed Phosphorus Leaching
Solutions to phosphorus leaching
Effect of Roadsalt on Phosphorus Leaching in Quercus macrocarpa and Quercus rubra.
Abstract
By measuring the rate of phosphorus leaching in two different types of leaves
found among the Wingra Watershed, we were able to determine the affects that
NaCl had on plant nutrition. The two different leaf species used were the Red
Oak (Quercus rubra) and the Bur Oak (Quercus macrocarpa); two jars for each
species containing the leaves and deionized water while two others had NaCl or
road salt added. Using the Hach PhosVer 3 method, the leaves were tested in
intervals of every other day for ten days resulting in five consecutive tests.
Our prior hypothesis was that the NaCl would cause phosphorus to be released
from the leaves more rapidly that the control. Our results showed that the
phosphorus was generally the highest on day 6 for the Bur Oak leaves with and
without NaCl added. Phosphorus leaching within the Red Oak leaves was different
where on day 4 the leaching was the highest for the leaves that did not have
NaCl added and day 1 for Red Oak leaves with the NaCl added. From our results
we concluded that the NaCl added lessened the amount of phosphorus leaching
within the Bur Oak leaves and the Red Oak leaves.
Introduction
Phosphorus is one of the key nutrients affecting aquatic plant growth and the
amount of algae and weeds found within lakes, which is true for 80% of
In the roadsalt used, NaCl is one of four chemical compounds used. Among NaCl
were Potassium Chloride (KCl), (NH2CONH2), and (C2O6H14)
We asked, how will phosphorus leaching in Quercus macrocarpa and Quercus rubra
be affected by NaCl? Will prolonged exposure to roadsalt speed or slow the
leaching process? Will the phosphorus be greater or less over the ten day
period?
We hypothesized that the roadsalt would speed the leaching process of the
leaves, because the chemicals present in the roadsalt would speed the decay of
the leaves in turn leaching the phosphorus more rapidly than in the constant.
Methods
The two specimens chosen for phosphorus testing were Red Oak (Quercus rubra)
Bur Oak (Quercus macrocarpa). The two specimens were divided, Red Oak labeled
group A and Bur Oak labeled group B. To answer our question “how does road salt
affect the leaching of phosphorus from leaves?” each group was separated in to
two jars; a jar containing specimen A with deionized water and a jar containing
specimen A with deionized water and road salt. The same was done with Group B.
After further review from are first set of data, we decided that replicate
sample jars would be made for each A and B, with and without roadsalt. Replicate
samples will determine whether differences are meaningful or random.
Each jar was given the same values for each material. These values were based
on the usage instructions on the Safe Step Ice Melter container, as provided by
the company. For every square yard a quarter of a pound is recommended. Each
specimen of leave was placed over a square yard. Each specimen of leave was
placed over a square yard, and weighed 20 g. A quarter of a pound or 112 grams
of road salt was mixed with the appropriate sample jars. 1000ml of deionized
water was put in to each jar.
All eight jars were left with the leaves to soak for one day. Each jar was
rinsed with deionized water and hands were washed so phosphorous values were
accurate. A sample was collected from each jar over a ten day period
alternating days so samples were taken on Day 2, Day 4, Day 6, Day 8 and Day
10. Phosphorus amounts were calculated using the Hach Phosphorus Test. Along
with this test there was also a test of plain de-ionized water to serve as a
control.
Results
The period of ten days showed roadsalt had an effect on the leaching of
phosphorus from the two species of leaves. Figure 1 illustrates a difference in
phosphorus amounts in the jars with roadsalt. Over the ten day period, the
constant samples of Quercus macrocarpa and Quercus rubra had higher amounts of
phosphorus leaching than the samples with NaCl.
The samples in the jars marked constant released phosphorus on a gradual scale
in increments of .01-.02 mg/L each day. This gradual release of phosphorus in
the constant samples is an example of how leaching occurs in nature. Looking at
Figure 3 which compares the leaching processes by days shows that the leaching
process was greatly stunted by the NaCl added to each species of leaves, while
each group of leaves not affected by NaCl had high levels of phosphorus with
the highest level reaching 20.21 mg/L for Bur Oak leaves and 18.11 mg/L for Red
Oak leaves. We can compare this number to the leaves that were affected by
NaCl; the highest level of phosphorus for Bur Oak leaves was 10.97 mg/L and Red
Oak leaves were at 12.00 mg/L.
Fig.1 Phosphorous leaching in Red Oak leaves
Fig.2 Phosphorous leaching in Bur Oak Leaves
Discussion
The studies results show that NaCl has a direct effect
on the leaching of phosphorus from leaves. It is difficult to determine why the
samples containing roadsalt leached phosphorus nearly half the amount of the
phosphorus leached from the samples not containing roadsalt. In the roadsalt
used, NaCl is one of four chemical compounds present. Among NaCl were Potassium
chloride (KCl), (NH2CONH2), and (C2O6H14). It is possible that the chemical
compounds contained in the roadsalt had an effect during the leaching of the
phosphorus in the sample jars. This error bar is also included in the data
collected during the Hach Phosphorus Test.
In order to gain a better understanding of effects of roadsalt on phosphorus
leaching, the amount of time allowed for collecting data needs to be expanded.
A ten day period did not allow enough time for a total release of phosphorus in
each sample. It can be assumed that the phosphorous release peeked over the ten
day period, but that is undeterminable without a longer period for sample
collecting.
Through our research and testing we came up with possible alternatives to using
NaCl roadsalt that would be less harmful to the Watershed ecosystem. Wegner and
Yaggi suggest that using Calcium Magnesium Acetate (CMA) would be less harmful
to plants and animals, less destructive to concrete and noncorrosive to metals.
It has been found by the research of Cheng and Guthrie that CMA, “may actually
stimulate plant growth by improving soil structure and permeability” (Wegner
and Yaggi). The Friends of Lake Wingra suggest the use of sand in the
replacement of salt, otherwise decreasing the amount of salt used on the roads.
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