National Atmospheric Deposition Program 2006 Annual Summary

published or submitted for publicationis peer reviewe

Nitrogen in the Nation's Rain

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Total Deposition 2015 Annual Map Summary

In October 2011, the National Atmospheric Deposition Program (NADP) Executive Committee formed the Total Deposition (TDEP) Science Committee. The mission of TDEP is to improve estimates of atmos-pheric deposition by advancing the science of measuring and modeling atmospheric wet, dry, and total deposition of species such as sulfur, nitrogen, and mercury by providing a forum for the exchange of information on current and emerging issues within a broad multi-organization context including atmos-pheric scientists, ecosystem scientists, resource managers, and policy makers.published or submitted for publicationis peer reviewedOpe

Steering effects on growth instability during step-flow growth of Cu on Cu(1,1,17)

Kinetic Monte Carlo simulation in conjunction with molecular dynamics simulation is utilized to study the effect of the steered deposition on the growth of Cu on Cu(1,1,17). It is found that the deposition flux becomes inhomogeneous in step train direction and the inhomogeneity depends on the deposition angle, when the deposition is made along that direction. Steering effect is found to always increase the growth instability, with respect to the case of homogeneous deposition. Further, the growth instability depends on the deposition angle and direction, showing minimum at a certain deposition angle off-normal to (001) terrace, and shows a strong correlation with the inhomogeneous deposition flux. The increase of the growth instability is ascribed to the strengthened step Erlich Schwoebel barrier effects that is caused by the enhanced deposition flux near descending step edge due to the steering effect.Comment: 5 page

Mercury deposition in southern New Hampshire, 2006–2009

The atmospheric deposition of mercury (Hg) occurs via several mechanisms including wet, dry, and occult processes. In an effort to understand the atmospheric cycling and seasonal depositional characteristics of Hg, event-based wet deposition samples and reactive gaseous Hg (RGM) measurements were collected for approximately 3 years at Thompson Farm (TF), a near-coastal rural site in Durham, NH, part of the University of New Hampshire AIRMAP Observing Network. Total aqueous mercury exhibited seasonal patterns in Hg wet deposition at TF. The lowest Hg wet deposition was measured in the winter with an average total seasonal deposition of 1.56 μg m−2compared to the summer average of 4.71 μg m−2. Inter-annual differences in total wet deposition are generally linked with precipitation volume, with the greatest deposition occurring in the wettest year. Relationships between surface level RGM and Hg wet deposition were also investigated based on continuous RGM measurements at TF from November 2006 to September 2009. No correlations were observed between RGM mixing ratios and Hg wet deposition, however the ineffective scavenging of RGM during winter precipitation events was evidenced by the less frequent depletion of RGM below the detection level. Seasonal dry deposition of reactive gaseous Hg (RGM) was estimated using an order-of-magnitude approach. RGM mixing ratios and dry deposition estimates were greatest during the winter and spring. The seasonal ratios of Hg wet deposition to RGM dry deposition vary by up to a factor of 80

Anomaly of Film Porosity Dependence on Deposition Rate

This Letter reports an anomaly of film porosity dependence on deposition rate during physical vapor deposition - the porosity increases as deposition rate decreases. Using glancing angle deposition of Cu on SiO2 substrate, the authors show that the Cu film consists of well separated nanorods when the deposition rate is 1 nm/second, and that the Cu films consists of a more uniform (or lower porosity) film when the deposition rate is 6 nm/second; all other deposition conditions remain the same. This anomaly is the result of interplay among substrate non-wetting, density of Cu nuclei on the substrate, and the minimum diameter of nanorods

2015 Summary of Critical Load Maps

This summary is a collection of critical load maps for the U.S., developed by CLAD members using critical load data that are publically available as part of the NADP CLAD National Critical Load Database (NLCD).published or submitted for publicationis peer reviewedOpe

Deposition of La2Zr2O7 Film by Chemical Solution Deposition

La2Zr2O7 (LZO) formation of bulk powders and of films by Chemical Solution Deposition (CSD) process have been studied using propionates. The treatment involved a one step cycle in the reducing forming gas (Ar-5%H2) to be compatible with Ni-5at%W RABITS. Large amount of residual carbon was found in LZO powders formed in these conditions (10 wt %). The volume fraction of the cube texture in LZO films on Ni-5at%w RABITS was found to be a function of the speed of the gas flown above sample. This phenomenon is discussed in considering the C deposited from the carbon-containing gases emitted during the pyrolysis of the precursor. Using proper conditions (950 ^\circC and the speed of gas of 6.8\times10^{-2} m/s), LZO films with good surface crystallinity could be obtained on Ni-5at%W RABITS as demonstrated by X-ray diffraction, electron backscattered diffraction and RHEED. The existence of residual carbon in oxide films is a common question to films deposited by CSD processes under reducing condition

Deposition velocities of airborne microbe-carrying particles

The deposition velocity of airborne microbe-carrying particles (MCPs) falling towards surfaces was obtained experimentally in operating theatres and cleanrooms. The airborne concentrations of MCPs, and their deposition rate onto surfaces, are related by the deposition velocity, and measurements made by a microbial air sampler and settle plates allowed deposition velocities to be calculated. The deposition velocity of MCPs was found to vary with the airborne concentration, with higher deposition rates occurring at lower airborne concentrations. Knowledge of the deposition velocity allows the deposition on surfaces, such as product or settle plates, by a known airborne concentration of MCPs to be predicted, as well as the airborne concentration that should not be exceeded for a specified product contamination rate. The relationship of airborne concentration and settle plate counts of MCPs used in Annex 1 of the EU Guidelines to Good Manufacturing Practice to specify grades of pharmaceutical cleanrooms was reassessed, and improvements suggested