Investigations into the Role of Natural Organic Matter as an Interface between Aquatic Organisms and Environmental Pollutants

The impact of the continuous pollution of freshwater environments by multiple pollutants has not been well-studied. The goal of this research was to evaluate the toxicity of several modern pollutants in a model environment. The prokaryotic, unicellular blue-green algae Synechocystis WT6803 and the eukaryotic, multicellular Utterbackia imbecillis mussel larvae were studied along with Suwannee River natural organic matter (NOM). The toxicity response of the blue-green algae Synechocystis sp. was measured through changes in growth rates. The inorganic pollutant silver nanoparticles (0.044 μM) were toxic. Gold nanoparticles did not affect the growth rate. The addition of 15 mg/L NOM partially inhibited the toxicity of silver nanoparticles. Silver nanoparticles that were synthesized and capped with NOM were not toxic, thus the nanomaterial surface and composition influenced its toxicity. The organic pesticide norflurazon reduced the growth rate. The combination of 0.044 μM silver nanoparticles and 20 μM norflurazon with NOM had an antagonistic effect. However, the combination of 0.044 μM silver nanoparticles and 10 μM norflurazon in NOM had a synergistic effect. Using different chemically modified NOM, it was determined that the lipid components reduced the toxicity of norflurazon, the aromatic and carbohydrates enhanced the growth rate, and the aromatic moieties influenced antagonistic/synergistic interactions. The growth rate was not affected by the presence of 0.4 mg/L multi-walled carbon nanotubes and 15 mg/L NOM. No toxic effects were again observed when carbon nanotubes and 20 μM norflurazon were combined with NOM, indicating that the toxicity of norflurazon was inhibited by carbon nanotubes. Sonicated carbon nanotubes were more toxic the longer they were sonicated. The toxicity response of U. imbecillis mussel larvae to various pollutants was measured via basic standard viability testing and in vivo 31P NMR, a non-destructive technique that provides intercellular information. The internal cellular response to pollutants was measurable using 31P NMR over the course of time. The results for the viability tests were comparable to changes in the chemical peak shift changes for the inorganic phosphate peak for the pesticide atrazine, silver nanoparticles, and higher ionic strength conditions. 31P NMR is a promising technique for toxicological studies for this organism