Partitioning and dissolution behavior of metal-based engineered nanoparticles in sediment and soil suspensions

Nowadays engineered nanoparticles are being used in a whole range of commercial applications and are therefore expected to inevitably find their way into the environment where their fate and behavior are still largely unknown. The objective of this study was to investigate the behavior and fate of a number of engineered nanoparticles (CeO2, SnO2, Ag) in sediment and soil suspensions. In particular, the association of nanoparticles with solid phases, the kinetics of these interactions, and the solubility of the nanoparticulate matter in sediment and soil suspensions were studied. Four different sediments and three different soils were sampled at various locations in Flanders (Belgium), dried, grinded and characterized. Sediment and soil suspensions were prepared with Milli-Q water (1/10 S/L), spiked with the different metallic nanoparticles or corresponding ions, and continuously shaken for 24 hours. At regular time intervals, samples of the suspensions were collected and centrifuged at 500 or 2000 rpm, or left for gravitational settling. The supernatant was analyzed for total metal contents after aqua regia digestion and for dissolved metal ions after centrifugal ultrafiltration. In a second experiment, the impact of centrifugation speed on the amount of suspended matter in the supernatant was also studied. Relations between soil or sediment properties, suspended matter and metals in the supernatant were investigated. First data already point towards a strong association of nanoparticles with suspended material. The remaining data are still being collected and will be presented at the conference

Impact of water composition on association of Ag and CeO2 nanoparticles with aquatic macrophyte Elodea canadensis

In this study, the potential association of (citrate-stabilized) Ag (14.1 +/- 1.0 nm) and CeO2 (6.7 +/- 1.2 nm) engineered nanoparticles (ENPs), or their ionic counterparts, with the submerged aquatic plant Elodea canadensis, was examined and, in particular, parameters affecting the distribution of the nanoparticles (or metal ions) between plant biomass and the water phase were assessed using five distinct aqueous matrices (i.e. tap water, 10 % Hoagland's solution and three natural surface water samples). Individual plants were exposed to varying concentrations of Ag and CeO2 ENPs or Ag+ and Ce3+ ions during 72-h-lasting batch experiments. A dose-dependent increase of silver or cerium in plant biomass was observed for both the nanoparticles and the ions, whereby exposure to the latter systematically resulted in significantly higher biomass concentrations. Furthermore, the apparent plant uptake of CeO2 ENPs appeared to be higher than that for Ag ENPs when comparing similar exposure concentrations. These findings suggest that association with E. canadensis might be affected by particle characteristics such as size, composition, surface charge or surface coating. Moreover, the stability of the ENPs or ions in suspension/solution may be another important aspect affecting plant exposure and uptake. The association of the nanoparticles or ions with E. canadensis was affected by the physicochemical characteristics of the water sample. The silver biomass concentration was found to correlate significantly with the electrical conductivity (EC), dry residue (DR) and Cl-, K, Na and Mg content in the case of Ag ENPs or with the EC, inorganic carbon (IC) and Cl-, NO3 (-), Na and Mg content in the case of Ag+ ions, whereas significant relationships between the cerium biomass concentration and the EC, DR, IC and Ca content or the pH, EC, DR, IC and Cl-, Ca and Mg content were obtained for CeO2 ENPs or Ce3+ ions, respectively. Results also indicated that the Ag ENPs and Ag+ ions might potentially be toxic towards E. canadensis whereas no evidence of phytotoxicity was noted in the case of CeO2 ENPs or Ce3+ ions

Demonstration of an MT-compatible connectorisation of a laser-ablated optical interconnection on a printed circuit board

Integration of optical interconnections on a Printed Circuit Board (PCB) is very challenging, as compatibility should be maintained with standard PCB manufacturing technology. This paper describes the use of laser ablation, a technique already used in PCB manufacturing for drilling microvia's, as a suitable technique for the fabrication of multimode polymer waveguides, micromirrors, alignment features and microlenses. A frequency tripled Nd-YAG laser and a KrF excimer laser are used, both mounted on the same stage, resulting in a very high alignment accuracy. We demonstrate a parallel optical link over about 5 cm long PCB integrated waveguides, fully connectorised using a standard MT-based connector. This proves that laser ablation can be a key technology in optical board manufacturing to reach the stringent coupling tolerances