No abstract

This is the first study to quantify the dependence on wind velocity of airborne bacterial emission fluxes from soil. It demonstrates that manure bacteria get aerosolized from fertilized soil more easily than soil bacteria, and it applies bacterial genomic sequencing for the first time to trace environmental faecal contamination back to its source in the chicken barn. We report quantitative, airborne emission fluxes of bacteria during and following the fertilization of agricultural soil with manure from broiler chickens. During the fertilization process, the concentration of airborne bacteria culturable on blood agar medium increased more than 600 000-fold, and 1 m 3 of air carried 2.9 × 10 5 viable enterococci, i.e. indicators of faecal contamination which had been undetectable in background air samples. Trajectory modelling suggested that atmospheric residence times and dispersion pathways were dependent on the time of day at which fertilization was performed. Measurements in a wind tunnel indicated that airborne bacterial emission fluxes from freshly fertilized soil under local climatic conditions on average were 100-fold higher than a previous estimate of average emissions from land. Faecal bacteria collected from soil and dust up to seven weeks after fertilization could be traced to their origins in the poultry barn by genomic sequencing. Comparative analyses of 16S rRNA gene sequences from manure, soil and dust showed that manure bacteria got aerosolized preferably, likely due to their attachment to low-density manure particles. Our data show that fertilization with manure may cause substantial increases of bacterial emissions from agricultural land. After mechanical incorporation of manure into soil, however, the associated risk of airborne infection is low.

Investigations on the metal-organic (MO)CVD of platinum nanoparticles on spherical, chemical vapor synthesis (CVS)produced SiO 2 substrates are discussed in this paper. Commercially available methylcyclopentadienyl trimethyl platinum (MeCpPtMe 3 ) (1) and three newly synthesized cyclooctadienyl platinum precursors are chosen and tested during a continuous CVD/CVS process. The synthesis of this new class of stable, halogen-free precursors for atmospheric pressure (AP)CVD is presented. The complexes [PtMe 2 (R-COD)], where R ¼ Et (2a), n Bu (2b), and i Bu (2c), are shown to be highly suitable for the preparation of platinum nanoparticles. The precursors are characterized and their thermal properties are studied by thermogravimetric analysis (TGA) and infrared (IR). Investigations of the precursor decomposition mechanism, the effect of oxygen, and the autocatalytic effect during CVD are also carried out. Finally, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses prove that continuous CVS of gas-borne support particles combined with MOCVD of these newly synthesized platinum precursors gives ordered, defined platinum nanocatalysts with high dispersion and narrow size distribution (2 À 3 nm).

No abstract

No abstract