Silver nanoparticles (AgNPs) are the most common nanomaterials incorporated in commercial products due to their antimicrobial activity. Recently, AgNPs were detected in surface waters suggesting the potential for bioavailability in the aquatic receptor organisms. This dissertation research attempts to understand the potential toxicity of AgNPs on water quality indicators, focusing on the microbial community and amphipods. This study evaluated whether: (1) the antimicrobial properties of AgNPs pose potential risks to microbial communities in pathogen impaired streams; (2) AgNPs can cause a shift in functional diversity and metabolic fingerprinting of microbial communities; (3) survival and growth of Hyalella azteca (amphipods) could be affected by AgNPs; and (4) surface coating agents influence AgNP toxicity in H. azteca. Microbial community responses to AgNPs were assessed using standard plate count, microbial enzyme assays, and carbon substrate utilization with Biolog EcoPlates™. Ten-day and 28-d toxicity tests were conducted in a static system to assess AgNP effects on H. azteca. AgNPs caused a 69% decrease in microbial concentration and a 77% decrease in β-glucosidase activity at 0.32 mg Ag kg-1 dry sediment. The substrate utilization pattern of the microbial community was altered by AgNPs at 0.33 mg Ag kg-1 dry sediment. Ten-day LC50s for the survival of H. azteca were 3.3, 9.2, and 230.0 µg Ag L-1 for AgNO3, citrate-AgNP, and PVP-AgNP, respectively, whereas the 28-d LC50s were 3.0, 3.5, and 66.0 µg Ag L-1 for AgNO3, citrate-AgNP, and PVP-AgNP, respectively. The EC20s for growth (calculated as biomass) for the 10-d test were 1.6, 4.7, and 188.1 µg Ag L-1 for AgNO3, citrate-AgNP, and PVP-AgNPs; while the 28-d EC20s for AgNO3, citrate-AgNP and PVP-AgNP were 3.2, 0.5, and < 50 µg Ag L-1. The NOECS for dry weight were 4 and 1, and 100 µg Ag L-1, while those for biomass were 2, 0.5, and < 50 µg Ag L-1 for AgNO3, citrate-AgNP, and PVP-AgNP, respectively. The overall toxicity followed the trend: AgNO3 > citrate-AgNP > PVP-AgNP. The studies suggest that AgNPs pose potential risks to microbial communities and epibenthic macroinvertebrates used as bioindicators of water quality to protect public health and ecosystem health.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etd-5260 |
| Date | 01 August 2020 |
| Creators | Kusi, Joseph |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations |
| Rights | Copyright by the authors. |
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