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Lincoln University

1. Saleeb, Nadir. Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa.

Degree: 2019, Lincoln University

Silver nanoparticles (AgNPs) are frequently synthesised for use in consumer products and appliances because of their antimicrobial properties and ease of incorporation into plastics, industrial materials and solutions. Currently, there are no regulations for the use of AgNPs in consumer products or their disposal. Therefore, there is a need to evaluate the impact of AgNPs in the environment. Because of their chemistry and slow dissociation to reactive Ag ions (Ag+) over time, AgNPs have been shown in both prokaryote and eukaryote models to be cytotoxic. Ionic Ag could bio-accumulate in the environment, thereby causing toxic effects on soil microbes and other organisms, plants, and animals. This thesis examined (1) the mobility of AgNPs and Ag+ (as silver nitrate, AgNO3) in soil and (2) the uptake of Ag by various plants. In particular, it evaluated (3) the chronic toxic effects on sunflower plants, and (4) the acute and chronic toxic effects on Aporrectodea caliginosa earthworms. In the soil mobility study, at a specific pH, the KD value (distribution of Ag between solid and solution phases) for AgNPs was 10-fold higher than for Ag+, indicating that Ag+ is more mobile and more toxic than AgNPs. This could be due to saturation of binding sites in soil. KD increased at higher pHs because of increased sorption to variable charged surfaces in soil. In soil incubation studies conducted at 20°C and 35°C, the solubility of AgNPs/Ag+ was greater at the higher soil temperature. The sorption of AgNPs to soil decreased over time, because all AgNPs were transformed into Ag+ due to degradation over time. Plant uptake of Ag in different parts (root cf. shoot) of perennial ryegrass (Lolium perenne L.) grown in soil amended with different concentrations (ranging from 0.0019% to 1%) of AgNPs and Ag+ indicated that Ag+ was 10-fold more soluble than AgNPs. Soil pH had a significant effect on sorption of AgNPs/Ag+ by plants, with sorption increasing with increased pH. Exposure of ryegrass to various AgNPs/Ag+ concentrations showed that concentrations < 10 mg/kg (dry matter) had a stimulatory effect on plant growth but >200 mg/kg of AgNPs/Ag+ reduced plant growth. In an Ag uptake study of nine vegetables (spinach, parsley, radish, lettuce, rocket, carrot, silver beet, leek, beetroot) grown in Templeton Silt Loam soil amended with 70 mg/kg AgNPs/Ag+, Ag uptake by control plants from naturally present Ag in soil was low (0.5 mg/kg) compared to a 3.5 to 3.8 mg/kg concentration in plants grown in soils spiked with AgNPs/Ag+ respectively. The highest concentration factor (5–9) occurred in carrot, silverbeet and spinach. A more detailed study on Ag concentrations in sunflower following 53-days’ exposure to soil amended with 150 mg/kg AgNPs/Ag+ showed that Ag accumulated in the roots > leaves. In the sunflower, Ag+ > AgNPs increased the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) in a dose- and time dependent manner and also increased the…

Subjects/Keywords: Silver (Ag+); toxicity; soil; Plants; Sunflower; earthworms; Aporrectodea caliginosa; Ag distribution in plants; Chlorophyll; Total soluble protein; Total soluble carbohydrates; Silver nanoparticles (AgNPs); Total phenolic compounds; antioxidant enzymes; antioxidant vitamins; AgNPs mobility; KD value; incubation; vegetable trace elements; cytotoxicity; mobility; ryegrass; 05 Environmental Sciences; 0503 Soil Sciences

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APA (6th Edition):

Saleeb, N. (2019). Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa. (Thesis). Lincoln University. Retrieved from http://hdl.handle.net/10182/10904

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Saleeb, Nadir. “Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa.” 2019. Thesis, Lincoln University. Accessed October 19, 2019. http://hdl.handle.net/10182/10904.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Saleeb, Nadir. “Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa.” 2019. Web. 19 Oct 2019.

Vancouver:

Saleeb N. Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa. [Internet] [Thesis]. Lincoln University; 2019. [cited 2019 Oct 19]. Available from: http://hdl.handle.net/10182/10904.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Saleeb N. Interaction of Silver Nanoparticles and Silver Ions with Soil, Plant and Earthworm Aporrectodea caliginosa. [Thesis]. Lincoln University; 2019. Available from: http://hdl.handle.net/10182/10904

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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