Silver Nanoparticle Fate and Accumulation in the Aquatic Food Web of Stream Microcosms

76 Pages·2017·1.51 MB·English

Georgia Southern University
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Electronic Theses and Dissertations Graduate Studies, Jack N. Averitt College of
Summer 2017
Silver Nanoparticle Fate and Accumulation in the
Aquatic Food Web of Stream Microcosms
Stefan J. Petersen
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Recommended Citation
Petersen, S.J., SILVER NANOPARTICLE FATE AND ACCUMULATION IN THE AQUATIC
FOOD WEB OF STREAM MICROCOSMS, GSU, 2017
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SILVER NANOPARTICLE FATE AND ACCUMULATION IN THE AQUATIC
FOOD WEB OF STREAM MICROCOSMS
by
STEFAN PETERSEN
(Under the Direction of Risa A. Cohen)
ABSTRACT
Silver nanoparticles (AgNPs) are used in 25% of all nano-enabled products and applied
for anti-microbial properties. Silver nanoparticles are discharged into aquatic environments
through wastewater discharge, runoff, and chemical spills. Once in aquatic environments silver
nanoparticles have the potential to harm aquatic organisms. While the fate of silver nanoparticles
in lentic systems has been investigated, limited information is available for the fate of silver
nanoparticles in flowing environments. The purpose of this study was to compare the fate of
AgNPs following a one-time pulsed application simulating a chemical spill, or small repetitive
applications simulating effluent discharge, in artificial stream communities containing river
water, sediment, periphyton, snails, and fish under realistic environmental conditions. In addition
to comparing the fate of AgNPs between application types, the fate of AgNPs were also
compared between 35 and 70 µg L-1 concentrations of AgNPs. Water samples were collected on
days 0, 7, and 14 to quantify total Ag (TAg) in the water column. Periphyton samples were taken
on days 0 and 14, and sediment, snail, and fish samples were taken on day 14 for silver content.
Results from this study show that AgNP concentrations applied to streams only affects the fate of
AgNPs in sediment where the majority of AgNPs settled and in fish which had limited exposure
to AgNPs in the water column. Additionally, application type only affected the fate of AgNPs in
periphyton samples of pulsed treated streams where snails and flowing conditions had a longer
period of time to reduce Ag adsorption to periphyton compared to repetitively treated streams.
In this study, silver nanoparticles rapidly settled in lotic environments placing benthic organisms
at risk for Ag accumulation. Furthermore, exposure to 70 µg L-1 and 35 µg L-1 AgNPs
concentrations in artificial streams was not toxic to aquatic organisms regardless of application
type. This study emphasizes the importance of testing AgNP exposure under environmentally
relevant conditions to assess their fate and toxicity in the environment.
INDEX WORDS: Mesocosms, Ionic strength, Sedimentation, Suspension, Dissolved organic
carbon, Toxicity, Periphyton, Snails, Fish, Settling
SILVER NANOPARTICLE FATE AND ACCUMULATION IN THE AQUATIC
FOOD WEB OF STREAM MICROCOSMS
by
STEFAN PETERSEN
B.S., Buena Vista University, 2012
A Thesis Submitted to the Graduate Faculty of Georgia Southern University in Partial
Fulfillment of the Requirements for the Degree
MASTER OF SCIENCE
STATESBORO, GEORGIA
© 2017
STEFAN PETERSEN
All Rights Reserved
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SILVER NANOPARTICLE FATE AND ACCUMULATION IN THE AQUATIC
FOOD WEB OF STREAM MICROCOSMS
by
STEFAN PETERSEN
Major Professor: Risa A. Cohen
Committee: John Stone
Vinoth Sittaramane
Johanne Lewis
Electronic Version Approved:
July 2017
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ACKNOWLEDGEMENTS
I would like to thank my family for supporting my career goals and encouraging me to
pursue a master’s degree. I would like to thank Jessica Devitt for supporting me during graduate
school and helping me throughout my experiment, as well as Jason Duff, Jack Eschenshroeder,
Lauren Neel, Byron Collins, Garret Strickland, Becky Scott, Preston Pound, Jackson Tomlinson,
Elizabeth Craddock, Allison Lutz, and Anna Wagner for collecting and processing streams
samples. I would like to thank my funding sources the Georgia Southern College of Science and
Mathematics, Georgia Southern Graduate Student Organization, Ogeechee River Project in
addition to the Richmond Hill Fish Hatchery for providing me with the fish used in this
experiment. I would also like to thank John Stone, Stephanie Canonico-May, and the Georgia
Southern Chemistry department for providing the silver nanoparticles and instrumentation
needed to complete my studies. I would like to thank my committee members Vinoth
Sittaramane and Johanne Lewis for providing their insight and help with questions arising during
this project. Lastly, I would like to thank my advisor, Risa Cohen for helping me become a better
scientist and writer.
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS……………………………………………………………………….2
LIST OF TABLES………………………………………………………………………………...4
LIST OF FIGURES…………………………………………………………………………….....5
CHAPTER
1 SILVER NANOPARTICLE FATE AND ACCUMULATION IN THE AQUATIC
FOOD WEB OF STREAM MICROCOSMS…………………………………………...6

Chapter 1 Introduction……………………………………………………….........6
Chapter 1 Methods……………………………………………………………….12
Chapter 1 Results………………………………………………………………...20
Chapter 1 Discussion…………………………………………………………….22
REFERENCES……………………………………………………………………………..……46
APPENDIX

SILVER NANOPARTICLE AND SILVER ION TOXICITY TO NAVICULA SP.
IN ARTIFICIAL STREAMS

Appendix Introduction………………………………………….………………..54
Appendix Methods…………………………………………………….……........55
Appendix Results………………………………………………………………...58
Appendix Discussion…………………………………………………………….60
REFERENCES……………………………………………………………………………...…...70
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LIST OF TABLES
CHAPTER 1
Page
Table 1: Total water column Ag concentration after initial AgNP exposure and one
and two weeks after the start of the experiment............................................................30

Table 2: Average stream pH, DO, specific conductivity, and temperature in all streams over
two weeks..............................……………………………………................................31

Table 3: Comparisons showing the overall differences between treatments in Ag accumulation
Day 0 periphyton, Day 14 periphyton, snails, fish, and sediment, in addition to the
corresponding Tukey-Kramer, Wilcoxon Each Pair, and Steel-Dwass All Pairs
Post-Hoc tests……………………………………………………………………........32

Table 4: Results of Ag accumulation in Day 14 periphyton, snails, fish, sediment, and water
samples..........................................................................................................................33

Table 5: Comparisons of initial periphyton biomass, water chlorophyll a, periphyton chlorophyll
a, and DOC concentration………………………………………………...……...…...35

Table 6: Analyses of the effects of AgNP concentration and application type on final
periphyton biomass, water chlorophyll a, periphyton chlorophyll a, and DOC
concentrations................................................................................................................36

APPENDIX

Page

Table 1: Average stream pH, DO, specific conductivity, and temperature in artificial streams...67

Table 2: Mean total Ag concentrations in the water column……………………………..….…..63

Table 3: Comparisons of initial DOC concentrations on Day 7 and relationships between DOC
concentrations and Ag concentration in the water column…..………………….……63

Table 4: Comparisons of initial and final water chlorophyll a concentrations on Days 0
and 14……………………………………………………………………….…….…..64

Table 5: Comparisons of Navicula sp. populations over the seven-day experiment and
comparisons of initial and final stream cell counts…………………………………...65
5

LIST OF FIGURES
CHAPTER 1
Page
Figure 1: Artificial stream microcosm showing dimensions, individual microcosm setup,
and experimental set up in the greenhouse....................................................................37

Figure 2: Citrate capped AgNPs (~50nm) used in the experiment................................................38

Figure 3: Concentration of total Ag in the water column measured on Days 0, 7, and 14 by
AgNP treatment.............................................................................................................39

Figure 4: Initial Ag values determined in periphyton samples comparing µg. of Ag. per g. of
periphyton vs AgNP treatments....................................................................................40

Figure 5: Final periphyton Ag values after two weeks comparing µg. of Ag. per g. of
periphyton vs AgNP treatments....................................................................................41

Figure 6: Accumulation of AgNPs by snails after two weeks comparing µg. of Ag. per g. of
snail vs AgNP treatments..............................................................................................42

Figure 7: Accumulation of AgNPs by fish after two weeks comparing µg. of Ag. per g. of
fish vs AgNP treatments................................................................................................43

Figure 8: Ag accumulation in sediment after two weeks shown comparing µg. of Ag. per g.
of sediment vs AgNP treatments...................................................................................44

Figure 9: Diagram showing the recovery of AgNP fate and possible trophic interactions...........45

APPENDIX

Page

Figure 1: Stream and pond mesocosm design…………………………………………………....68

Figure 2: Mean Navicula sp. cell counts in ponds and streams taken on day 0, 1, 3, 5, and 7…..69