Abstract + Introduction:

Link to Abstract + Introduction Video:

“Conductivity is a measure of the ability of water to pass an electrical current. Because dissolved salts and other inorganic chemicals conduct electrical current, conductivity increases as salinity increases” (EPA).

Materials and Methods:

Link to Materials and Methods Video:

Map of the Study Area:

Figure 1: A zoomed in view of the first study site by the Glover School: the downstream section of Pine Tree Brook.

Figure 2: A zoomed in view of the second study site on William Gregg's property in the Blue Hills: the upstream section of Pine Tree Brook.

Results:

Each graph is a depiction of Time vs. Conductivity. The blue graphs are the conductivity data from the downstream part of Pine Tree Brook by Glover and the orange graphs are from William Gregg's property.

12/16/2020 21:10 -- 12/17/2020 04:50

12/18/2020 00:40 -- 12/19/2020 10:00

12/24/2020 00:00 -- 12/26/2020 12:10

01/26/2021 15:30 -- 01/28/2021 7:40

The peaks in the Glover data do not coincide with any patterns in the William Gregg (WG) data. Since WG is surrounded by nature and soil instead of pavement and roads, the road salt has no way to get into that upstream part of the brook, thus making it unaffected by snowfall events. Every peak in the Glover data does coincide with a snowfall event in the Milton, MA area. There were snowstorms on December 17, December 23rd, and January 27 which explain the spikes in conductivity in the downstream part of Pine Tree Brook. Furthermore, the average acute concentration was calculated by averaging all of the studied peaks in the Glover dataset. The peaks were 441.4, 365.6, 606.4, and 469.1 μS/cm (microSiemens per centimeter) which averaged to 470.625 μS/cm.

Discussion:

The data suggests that only the downstream conductivity is affected by road salt distribution. As hypothesized, the Glover data peaked during snowfall events unlike the WG data which seemed unaffected. As you can see from the zoomed in views of the study sites, the Glover site is surrounded by pavement and busy roads whereas the William Gregg site is in a deeply forested area. This urban vs rural study in conductivity is severely affected by impervious surfaces.

There was little to no uncertainty in this study because all of the data collection was done by a sensor. The sensor was placed at the bottom on the brook attached to a brick in order to prevent movement which could lead to uncertainty. After a few months we went back to collect the data using a data converter which transferred the readings onto an excel spreadsheet.

The major difference between the two study sites is that Glover, like much of the upstream watershed, is surrounded by pavement. An impervious surface is defined as “a surface that does not allow water to percolate through; eliminating rainwater infiltration and natural groundwater recharge” (City of Pacific Grove). Many people are promoting the replacement of impervious surfaces with previous surfaces because of its many benefits: promote infiltration of stormwater, are easier to repair and replace, prevent flooding etc. In this study, the water travels faster on the pavement which transfers the road salt from the sidewalks and roads into our water bodies like Pine Tree Brook. If you think of impervious surfaces as an independent variable, the data is suggesting that as impervious surfaces increase, the conductivity during snowfall events also increases which in turn suggests that more road salt is accumulating in urban areas.

It is also important to note that road salts can have extremely negative effects on our environment. Salt was first used to melt icy roads in 1938 because it proved to be cheap and effective. However, the need for road salt has grown tremendously over the decades. Today, our country uses approximately 20 million tons of salt on our roads yearly. Road salt keeps the ice and snow off of the road which keeps us human safe, but the excess salts that end up in our rivers, brooks, and streams are unsafe to aquatic animals. In fact, at certain higher concentrations, road salt dissolved in water bodies can be fatal to some animals. Furthermore, the salt can also change the way the water mixes which leads to biological dead zones. These changes ultimately affect water quality. Snow storms that inevitably lead to the distribution of road salts are harming our aquatic ecosystems.

A next step in this study could be analyzing more peaks. I only used four peaks that I found in a two month span. Using more peaks from the same datasets could provide more accurate results. Furthermore, it would be beneficial to look at different environments. Conducting this same study in a different stream or brook could give more data points and ecosystems to analyze. Furthermore, you could also further this study by observing the effect the road salt has on aquatic ecosystems- what concentration becomes fatal and what concentration is tolerable?