Analyzing Changes in Salinity and Evaporation on Water Quality
Annie Causey, Renata Lemos, Avion Goordeen, Donna Selch, and Cara Abbott
Florida Atlantic University
Contact : [email protected]
Abstract
Methods and Materials
Project Design
These two images show FAU students measuring the water quality using a digital salinity refractometer,
pH and ORP meters, and a pH/EC/TDS temperature meter.
Results
The evaporation of water in the ocean can lead to hyper salinity caused by the
extra substances left behind during the process. The Florida bay is surrounded by
the Florida loop current and the Florida Keys, its salinity reading has been •.
recorded as high as 70 ppt, double the normal capacity of seawater. The bay
salinity depends on the amount of fresh water released from the Everglades and
the magnitude of water outputted to the Gulf of Mexico and the Atlantic Ocean, as
well as the ratio between the amount of water evaporated and the amount of
precipitates left in the remaining water pool. For this research nine saltwater
treatments from 0 to 40 ppt in increments of 5 ppt were constructed to examine
how evaporation rates are affected by varying salinities. During this study, data
were collected from each of the nine treatments before and after evaporation. The
data recorded included salinity readings, pH and ORP levels and volume of water
evaporated. The analyses of this data will determine the relationship between
salinity levels and evaporation rates.
Purpose
pH VS Salinity
A
ORP VS Salinity
8.8
Salinity VS Salinity
60
300
8.7
50
250
8.6
40
200
8.5
pH
Evaported
8.4
Initial
8.3
Evaporated
150
Initial
100
Salinity (ppt)
Methodology
ORP (mV)
This study will analyze how initial salinity levels effect evaporation rates and
resulting hyper salinity levels. Results can be used to assess how evaporation in
certain natural bodies of water (such as the Everglades) can result in detrimental
water quality effects as a result of evaporation induced hyper salinity. Many of our
local and worldwide water environments are changing very quickly. Increased
salinity can have major detrimental effect on environmental niches and
subsequently local flora and fauna. Results from this study will enable us to
predict, based on initial salinity levels, how a body of water’s water quality may
change over time due to evaporation and as such allow timely intervention to
protect flora and fauna.
Evaporated
30
Initial
20
8.2
50
10
8.1
0
8
0
5
10
15 20 25 30
Salinity (ppt)
35
40
0
5
10 15 20 25 30 35 40
Salinity (ppt)
Discussion
0
0
5
10 15 20 25 30 35 40
Salinity (ppt)
Participants
B
•
Picture A is one of the nine treatment bins. Picture B shows two treatment bins. The black water pump
is within the bin and the black bucket filters the recycled water.
Two sets of data are given in each graph above, values pre-evaporation
(initial) and those after evaporation (evaporated). pH versus salinity data show
that in initial samples, as salinity increases, pH decreases. After evaporation
pH still decreases with increased salinity but at greater than 20ppt, evaporation
causes a more rapid decrease in pH values. This is important as in natural
environments certain species have very narrow pH requirements. ORP data
versus salinity levels indicate that in initial samples the presence of saline
causes an increase in ORP levels over no saline at all. Between 5 and 40ppt
there is only a slight increase in ORP levels. After evaporation, ORP levels are
lower than initially and increase slightly as salinity increases. Evaporation
caused decreased levels of ORP may suggest less electron energy available
for the chemical oxidation and reduction reactions needed to sustain life. The
last graph shows the effects of evaporation on salinity levels and values for
Initial samples are as expected from 0-40 ppt. While evaporation caused an
increase in salinity levels, after 20ppt, even greater salinity values were
seen. This study shows that in saline conditions evaporation affects water
quality. At salinities above 20ppt, evaporation causes more extreme water
quality changes. With some Florida waters having salinities starting at 4070ppt, evaporation could have major detrimental effects natural marines
environments and fragile ecological niches.
I would like to acknowledge my mentors, Donna Selch and Cara
Abbott, who taught me so much during this project I would also like to
thank my many peers who aided in the collection of data.
Finally I would like to thank FAU for providing the greenhouse facility
used for this study.