An investigation of factors influencing the bioavailability of silver nanoparticles within a terrestrial system

Due to the high reactivity and antibacterial properties of silver nanoparticles, they are increasingly being added to consumer products and appliances. With this increased use, however, there will be a resultant increase in the amount released to the environment in one form or another. Studies that describe the environmental fate of silver nanoparticles are lacking, especially in terrestrial systems. A series of experiments were devised in order to determine which soil properties and which nanoparticle characteristics had the most significant impact on bioavailability to plants and insects. Plants and invertebrates make up the base of all terrestrial food webs, so two species of each were chosen to examine: the plants Helianthus annuus and Sorghum vulgare and the insects Acheta domesticus and Tenebrio molitor. Nanoparticle size, concentration, and surface coating were examined in addition to soil pH, humic content, and clay content. All insects in treatment groups with a soil concentration of 25 ppm or higher were found to contain at least trace amounts of silver. Root samples of both plant species were found to contain more silver than the other plant tissues analyzed. By comparing the results from all the various investigations it was found that nanoparticle concentration was the most important nanoparticle characteristic and clay content was the most significant soil property.