Effects of the Accumulation of Triclosan and Its By-Products on Soil Levels and Plant Uptake.

Triclosan (TCS), a synthetic antibacterial agent, is commonly found in personal products such as deodorants, toothpaste, antimicrobial soaps, and in some cosmetics. Due to incomplete removal of triclosan from wastewater treatment plants, it can also be found in freshwater systems that are later used for crop irrigation, introducing triclosan into agroecosystems. Accumulation of TCS in soil can inhibit bacterial populations and contaminate crops as high levels of plant uptake can occur in onions. In this study, the effect of triclosan-degrading rhizobacteria on uptake of triclosan by onions will be examined using two water types (molecular water and simulated river water), two concentrations of triclosan (0.0 µg/L and 1.5 µg/L) and five rhizobacterial inoculations (control-no inoculum, OT2-03A, OT2-17, OT1-11C2, and OTMIX-consortium of three isolates). Five replicate pots per treatment contained a 9:1 native to potting soil mixture, and were inoculated with a rhizobacteria treatment before onion planting. Onions were grown in a greenhouse, irrigated every other day with or without triclosan using the two water types, and monitored weekly for height. After 100 days of growth in a greenhouse, soils will be collected for chemical extractions and bacterial counts. Onion plants will be separated into two parts, leaves and bulbs/roots, prior to chemical extraction. Extracts will be analyzed by GC-MS for triclosan and methyl-triclosan (the initial biodegradation product for triclosan). Preliminary data shows that inoculation with onion rhizobacteria results in greater onion growth (based on height) without triclosan; however, this appears to be dependent on water type. It is expected that inoculation will result in greater onion biomass and reduced triclosan levels. This study will help us further understand the influence of triclosan-degrading rhizobacteria on accumulation and plant uptake of triclosan, along with its by-products, when irrigated with recycled waters.