title: Low concentrations of silver nanoparticles in biosolids cause adverse ecosystem responses under realistic field scenario.
abstract: A large fraction of engineered nanomaterials in consumer and commercial products will reach natural ecosystems. To date, research on the biological impacts of environmental nanomaterial exposures has largely focused on high-concentration exposures in mechanistic lab studies with single strains of model organisms. These results are difficult to extrapolate to ecosystems, where exposures will likely be at low-concentrations and which are inhabited by a diversity of organisms. Here we show adverse responses of plants and microorganisms in a replicated long-term terrestrial mesocosm field experiment following a single low dose of silver nanoparticles (0.14 mg Ag kg(-1) soil) applied via a likely route of exposure, sewage biosolid application. While total aboveground plant biomass did not differ between treatments receiving biosolids, one plant species, Microstegium vimeneum, had 32 % less biomass in the Slurry+AgNP treatment relative to the Slurry only treatment. Microorganisms were also affected by AgNP treatment, which gave a significantly different community composition of bacteria in the Slurry+AgNPs as opposed to the Slurry treatment one day after addition as analyzed by T-RFLP analysis of 16S-rRNA genes. After eight days, N2O flux was 4.5 fold higher in the Slurry+AgNPs treatment than the Slurry treatment. After fifty days, community composition and N2O flux of the Slurry+AgNPs treatment converged with the Slurry. However, the soil microbial extracellular enzymes leucine amino peptidase and phosphatase had 52 and 27% lower activities, respectively, while microbial biomass was 35% lower than the Slurry. We also show that the magnitude of these responses was in all cases as large as or larger than the positive control, AgNO3, added at 4-fold the Ag concentration of the silver nanoparticles.
authors.affiliation: Department of Biology, Duke University, Durham, NC, USA. benjamin.colman@duke.edu
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Colman
authors.forename: Christina L
authors.initials: CL
authors.lastname: Arnaout
authors.forename: Sarah
authors.initials: S
authors.lastname: Anciaux
authors.forename: Claudia K
authors.initials: CK
authors.lastname: Gunsch
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hochella
authors.forename: Bojeong
authors.initials: B
authors.lastname: Kim
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Lowry
authors.forename: Bonnie M
authors.initials: BM
authors.lastname: McGill
authors.forename: Brian C
authors.initials: BC
authors.lastname: Reinsch
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Richardson
authors.forename: Jason M
authors.initials: JM
authors.lastname: Unrine
authors.forename: Justin P
authors.initials: JP
authors.lastname: Wright
authors.forename: Liyan
authors.initials: L
authors.lastname: Yin
authors.forename: Emily S
authors.initials: ES
authors.lastname: Bernhardt
mesh_terms: D018533:Biomass; D017753:Ecosystem; D053768:Metal Nanoparticles; D046529:Microscopy, Electron, Transmission; D010944:Plants / Q000378:metabolism; D012834:Silver / Q000737:chemistry*; D012835:Silver Nitrate / Q000008:administration & dosage
chemical_list: D012834:Silver; D012835:Silver Nitrate