Date of Award
Doctor of Philosophy
Dr. John Miller
Dr. Michael Barcelona
Dr. Steven Bertman
Dr. Steve Kohler
Algal biomass, biosorption, nanoparticles, bloodworms, confocal, laser fluorescence
Pharmaceuticals and nanoparticles are increasingly released into the aquatic ecosystem, while removing these contaminants from waters can be challenging. This study explores the use of periphytic algal turf communities to remove these contaminants. Initially algal turfs from different locations and aquatic systems were analyzed for pharmaceuticals commonly observed in wastewater outflows. Lab-grown turfs were exposed to a mixture of six representative pharmaceuticals of different functionality (acid, base, neutral and steroidal). Analysis of water column and the algal biomass showed pharmaceutical removal rates varied, specific to each pharmaceutical. Caffeine and estradiol had the highest removal rates while carbamazepine was not removed. The relative biomass density of the algae exposed to pharmaceuticals was decreased, suggesting the mixture of pharmaceuticals used may have had a negative effect on the stability of the algal turfs.
Algae exposed to pharmaceuticals were analyzed by CHN and an ashing protocol to determine carbohydrate, lipid, protein, inorganic carbon (CO3 2) and oxygen content. The data showed that the pharmaceuticals did not significantly affect the chemical compositions of the biomass during the exposure. Two factor ANOVA was used and there was no statistically significant (α = 0.05). Experiments also showed that pharmaceuticals decreased the biomass density after exposure. Chlorophyll fluorescence intensity and absorbance of algae exposed to nanoparticles did not show statistically significant (t test > α = 0.05).
Lab-grown algal turfs were also exposed to silver and gold nanoparticles and to the corresponding to silver and gold ions. Atomic absorption measurement was used to quantify noble metal biosorption by the algal turfs. Biosorption was fast, essentially reaching maximum biosorption within 24 hours. The rate constants were almost same for low and high contaminant concentrations. Experiments showed that AgNPs and Ag (I) ions had a small effect on the biomass density. However AuNPs and Au (III) ions did cause decreased biomass density after exposure. Chlorophyll fluorescence intensity and absorbance of algae exposed to nanoparticles did not show statistically significant. The effect of nanoparticles on the compositions of algal biomass was not statistically significant (t test > α = 0.05).
Confocal laser microscopy was used to locate the nanoparticles in the algal cells and bloodworms. To do so, algal turf biomass was exposed to fluorescent paracetamol (PA)-modified AuNPs from the media. Confocal laser micrograph images showed that the PA-AuNPs, at least, are most likely inside the algal cells, though they are most concentrated in the cell walls.
To test whether nanoparticle contaminants sorbed by algal turfs can move to a higher trophic level. Bloodworms (Chironomidae sp. larvae) were fed fluorescent PA-AuNPs exposed algae for seven days, while another group of bloodworms were exposed to PA-AuNPs solution for the same interval. Confocal laser micrograph images showed that nanoparticles are present in, though at lower concentration, than for the bloodworm exposed directly to the PA-AuNPs. Nanoparticles can transfer from one trophic level to another.
Faraj, Haider Abid, "Biosorption of Pharmaceuticals and Noble Metals Nanoparticles by Algal Turf Communities" (2017). Dissertations. 3110.