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Dry Deposition (dry + deposition)

Distribution by Scientific Domains
Earth and Environmental Science60%
Engineering40%

Selected Abstracts

Estimation of net nitrogen flux between the atmosphere and a semi-natural grassland ecosystem in Hungary

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2010
A. Machon
The aim of this work is to estimate the net N balance (deposition , emission) between the atmosphere and a semi-arid, semi-natural grassland (Bugac station, Central Hungary, CarboEurope IP, NitroEurope IP level 3 site). Dry deposition of N compounds has been determined by the inferential method, based on continuous monitoring of NO2 gas and daily 24-hour concentration measurements of HNO3 vapour, NH3 gas, and NH4+ and NO3, particles, using dry deposition velocities from the literature, measured above surfaces with the same characteristics as Bugac station. The bi-directional flux of NH3 within the atmosphere and the canopy (excluding soil emission) has also been estimated by the inferential method. Wet deposition of nitrate and ammonium ions was calculated on the basis of daily precipitation sampling and concentration measurements of nitrate and ammonium ions. To estimate the soil-atmosphere exchange of different gaseous N forms (N2, NO, N2O, NH3), the DNDC model was used as validated by the chamber measurements of NO and N2O soil emission fluxes. Soil emissions of NO and N2O have been determined by dynamic and static soil chamber methods, respectively. The measurement and modelling activity covers a complete year. Using the measured and modelled data, the calculated N balance at Bugac station between August 2006 and July 2007 is estimated at ,8.8 kg N ha,1 year,1 (deposition) as a sum of the deposition and emission terms (,10.4 and 1.6 kg N ha,1 year,1, respectively). Due to the warm and dry weather during the examined period, wet fluxes were substantially lower than usual, which may also have altered the regular yearly course of dry deposition and emission. [source]

Modelling the chloride signal at Plynlimon, Wales, using a modified dynamic TOPMODEL incorporating conservative chemical mixing (with uncertainty)

HYDROLOGICAL PROCESSES, Issue 3 2007
T. Page
Abstract The application of a modified version of dynamic TOPMODEL for two subcatchments at Plynlimon, Wales is described. Conservative chemical mixing within mobile and immobile stores has been added to the hydrological model in an attempt to simulate observed stream chloride concentrations. The model was not fully able to simulate the observed behaviour, in particular the short- to medium-term dynamics. One of the primary problems highlighted by the study was the representation of dry deposition and cloud-droplet-deposited chloride, which formed a significant part of the long-term chloride mass budget. Equifinality of parameter sets inhibited the ability to determine the effective catchment mixing volumes and coefficients or the most likely partition between occult mass inputs and chloride mass inputs determined by catchment immobile-store antecedent conditions. Some success was achieved, in as much as some aspects of the dynamic behaviour of the signal were satisfactorily simulated, although spectral analysis showed that the model could not fully reproduce the 1/f power spectra of observed stream chloride concentrations with its implications of a wide distribution of residence times for water in the catchment. Copyright © 2006 John Wiley & Sons, Ltd. [source]

The Watershed Deposition Tool: A Tool for Incorporating Atmospheric Deposition in Water-Quality Analyses,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2009
Donna B. Schwede
Abstract:, A tool for providing the linkage between air and water-quality modeling needed for determining the Total Maximum Daily Load (TMDL) and for analyzing related nonpoint-source impacts on watersheds has been developed. Using gridded output of atmospheric deposition from the Community Multiscale Air Quality (CMAQ) model, the Watershed Deposition Tool (WDT) calculates average per unit area and total deposition to selected watersheds and subwatersheds. CMAQ estimates the wet and dry deposition for all of its gaseous and particulate chemical species, including ozone, sulfur species, nitrogen species, secondary organic aerosols, and hazardous air pollutants at grid scale sizes ranging from 4 to 36 km. An overview of the CMAQ model is provided. The somewhat specialized format of the CMAQ files is not easily imported into standard spatial analysis tools. The WDT provides a graphical user interface that allows users to visualize CMAQ gridded data and perform further analyses on selected watersheds or simply convert CMAQ gridded data to a shapefile for use in other programs. Shapefiles for the 8-digit (cataloging unit) hydrologic unit code polygons for the United States are provided with the WDT; however, other user-supplied closed polygons may be used. An example application of the WDT for assessing the contributions of different source categories to deposition estimates, the contributions of wet and dry deposition to total deposition, and the potential reductions in total nitrogen deposition to the Albemarle-Pamlico basin stemming from future air emissions reductions is used to illustrate the WDT capabilities. [source]

A coupled dispersion and exchange model for short-range dry deposition of atmospheric ammonia

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 618 2006
Benjamin Loubet
Abstract The MODDAS-2D model (MOdel of Dispersion and Deposition of Ammonia over the Short-range in two dimensions) is presented. This stationary model couples a two-dimensional Lagrangian stochastic model for short-range dispersion, with a leaf-scale bi-directional exchange model for ammonia (NH3), which includes cuticular uptake and a stomatal compensation point. The coupling is obtained by splitting the upward and downward components of the flux, which can be generalized for any trace gas, and hence provides a way of simply incorporating bi-directional exchanges in existing deposition velocity models. The leaf boundary-layer resistance is parametrized to account for mixed convection in the canopy, and the model incorporates a stability correction for the Lagrangian time-scale for vertical velocity, which tends to increase the Lagrangian time-scale in very stable conditions compared with usual parametrizations. The model is validated against three datasets, where concentrations of atmospheric NH3 were measured at several distances from a line source. Two datasets are over grassland and one is over maize, giving a range of canopy structure. The model correctly simulates the concentration in one situation, but consistently overestimates it at further distances or underestimates it at small distances in the two other situations. It is argued that these discrepancies are mainly due to the lack of length of one of the line sources and non-aligned winds. Analysis shows that the surface exchange parameters and the turbulent mixing at the source level are the predominant factors controlling short-range deposition of NH3. Copyright © 2006 Royal Meteorological Society [source]