Linking Changes in the Fate of Nanoparticles in Soil with Changes in Soil Microbial Populations.

Changes in the microbial community can have a significant impact ecosystem function and health, and little information exists on the how the aging of nanoparticles in soils will impact terrestrial microbial communities.  In the current study the fate, transport and, speciation of copper and zinc oxide nanoparticles in soil mesocosms were evaluated and compared to the changes in the soil microbial community as a function of time and depth.  Soils were collected from an agricultural soil processing center in Long Island, NY, and transferred to a 12 L container, 27 cm in depth.  Nanoparticles were applied to the soil surface and the vessels left outside under field conditions.  Over 162 days of incubation, the results indicated that both nanoparticles tested were leached through the soil matrix at different rates, with zinc oxide nanoparticles exhibiting increased mobility as compared to the copper particles.  Dissolution and changes in nanoparticle speciation were also apparent over time as determined by Cu and Zn solid phase speciation using XAFS spectroscopy.  Analysis of microbial communities using culture-dependent and independent methods clearly indicate that that copper and zinc oxide nanoparticles alter the microbial community structure.  In particular is the sensitivity of organisms found in rhizosphere, Flavobacteriales and Sphingomonadales.  Thus, the migration of NPs through soil matrix and changes in nanoparticle speciation influence the composition of the soil microbial community raising environmental concerns.