Holly Elsberry, Marie Nikolay, Marissa Van Dyke
Index
Introduction
Methods
Results
Conclusion
Effects of Sodium Chloride on
Earthworm Populations
Holly Elsberry, Marie Nikolay, Marissa Van Dyke
Index
Introduction
Methods
Results
Conclusion
Sodium Chloride is used as road salt to de-ice the Wisconsin
roads in the winter season. Excess use of sodium chloride can seep into the soil
and become harmful to the Lake Wingra watershed.
Sodium chloride concentrations can affect animals living in the soil, such as
earthworms.
The purpose of this study was to determine if sodium chloride concentrations
have an effect on earthworm population on the Edgewood Campus.
Earthworms can be used as a measure of the health of the soil. They aerate the
soil and break up organic material and also aid in the decomposition of plant
litter, such as the thatch layer, and in recycling of nutrients (Townsend,
Potter, & Powell, 2003).
In order to determine the health of the Lake Wingra Watershed we compared
earthworm populations on the Edgewood Campus in relation to the sodium chloride
concentrations of the earthworm’s habitat.
Four locations were tested on the Edgewood College Campus; the
Dericci Courtyard, Raingarden A (behind the Edgedome), Raingarden B (in front of
the Edgedome), and behind Regina near the walkway.
A mustard slurry was used to extract the earthworms from the soil in order to
measure the population.
Core samples of soil were taken at each location. Core samples were separated
into top soil samples and bottom soil samples.
We assessed the type of soil taken from each of the four sites by using a
standard procedure for soil type identification (Environmental Concern, 1995).
Sodium chloride concentrations were obtained by using the Hach Chloride Test
Kit: Model 8-P low range 0-100 mg/L. We converted our results mg/L into mg
of chloride per gram of dry weight soil so we could determine the ratio of
chloride to soil.
Soil conductivity was obtained through a handheld conductivity device.
Soil types ranged from clay loam to sandy loam.
Chloride concentrations ranged from 33.3 - 166.7 mg/g and conductivity ranged
from 38.5 µS/g - 249 µS/g.
There was a strong correlation between each location’s conductivity and its
chloride concentration.
There were fewer earthworms where there were higher concentrations of chloride,
and areas with lower concentrations had larger earthworm populations
The association of fewer earthworms and higher chloride concentrations was also
shown when we averaged each location’s top and bottom soil samples .
Figure 1. Chloride concentrations of each test location in relation to
respective conductivity. T (Top Soil); B (Bottom Soil)
Figure 2. Earthworm counts as a function of Chloride concentrations from the top
and bottom 1.5 inch core sample of soil measured mg/g
Figure 3. Earthworm counts as a function of the average Chloride concentrations
from the top and bottom core samples of each test location
Figure 4. Top and bottom core sample averages of chloride and conductivity
Results indicate the lack of earthworms in the soil of
certain locations may be due to high concentrations of chloride. Locations with
lower populations of earthworms had higher sodium chloride concentrations and
locations with higher populations of earthworms had lower sodium chloride
concentrations. The absence of earthworms in the soil results a determinant of
soil quality and health as earthworms serve to aerate the soil and break up
plant litter. The use of road salt by the City Madison and the Edgewood College
Campus contributes to the sodium chloride concentrations on campus and in the
Lake Wingra Watershed.
We reccomend that the City of Madison and the Edgewood College Campus limit the
amount of road salt applies to city streets, roads and sidewalks in an effort to
protect the soil quality and health of the Lake Wingra Watershed.
