Modelling the decay of concentrations of nitrogenous compounds with distance from roads

Abstract Passive sampler concentration measurements of nitrogen dioxide (NO 2 ) and ammonia (NH 3 ) were performed in the framework of a transect study to investigate the impact of vehicle emissions on ecosystems dissected by highways. The concentrations of both gases decrease markedly with distance from highway to regional background pollution values. Modelling the functional form of the decay is of interest for reducing the amount of measurements, for exposure assessment, and for predicting background concentrations. Three modelling approaches are compared: the exponential decay function, the shifted power-law function, and the linear-logarithmic function. The models were fitted to four compound- and year-specific data sets from one transect, applying mixed-effects models for repeated-measurement designs. The goodness-of-fit did not differ consistently between the model classes. Combined data from four transects with different characteristics were analysed with the exponential decay model, allowing for transect-specific random coefficients. From the empirical point of view, none of the three model classes is consistently superior to the others. But for prediction beyond the observed distance range it is essential to consider a model with meaningful parameters. The final choice of a model depends on the amount of data and on the characteristics to be represented by the model.

[1]  Andrew J. Kean,et al.  On-Road Measurement of Ammonia and Other Motor Vehicle Exhaust Emissions , 2000 .

[2]  Matthew P. Fraser,et al.  Detection of Excess Ammonia Emissions from In-Use Vehicles and the Implications for Fine Particle Control , 1998 .

[3]  D. Bates,et al.  Mixed-Effects Models in S and S-PLUS , 2001 .

[4]  David M Stieb,et al.  Ambient nitrogen dioxide and distance from a major highway. , 2003, The Science of the total environment.

[5]  C. Kölling,et al.  Nitrogen Deposition and Nitrate Leaching at Forest Edges Exposed to High Ammonia Emissions in Southern Bavaria , 2004 .

[6]  David R. Anderson,et al.  Model selection and multimodel inference : a practical information-theoretic approach , 2003 .

[7]  Bert Brunekreef,et al.  Air pollution from traffic in city districts near major motorways. , 1998 .

[8]  D. Fowler,et al.  Ammonia emissions from non-agricultural sources in the UK , 2000 .

[9]  A. Fischer,et al.  Changed vegetation composition in coniferous forests near to motorways in Southern Germany: the effects of traffic-born pollution. , 2006, Environmental pollution.

[10]  David M. Holland,et al.  Variations of NO, NO2 and O3 concentrations downwind of a Los Angeles freeway , 1981 .

[11]  Anton Fischer,et al.  Elevated NH3 and NO2 air concentrations and nitrogen deposition rates in the vicinity of a highway in Southern Bavaria , 2005 .

[12]  P. Hug,et al.  Three-way catalyst-induced formation of ammonia : velocity- and acceleration-dependent emission factors , 2006 .

[13]  Wenhua Wang,et al.  Shifted power-law relationship between NO2 concentration and the distance from a highway: A new dispersion model based on the wind profile model , 2006 .

[14]  H. Pleijel,et al.  On the logarithmic relationship between NO2 concentration and the distance from a highroad. , 2004, The Science of the total environment.

[15]  A. Kasper-Giebl,et al.  Field intercomparison of diffusive samplers for measuring ammonia. , 1999, Journal of environmental monitoring : JEM.

[16]  S C F Palmer,et al.  Concentrations of ammonia and nitrogen dioxide at roadside verges, and their contribution to nitrogen deposition. , 2004, Environmental pollution.

[17]  J. Cape,et al.  Vegetation composition of roadside verges in Scotland: the effects of nitrogen deposition, disturbance and management. , 2005, Environmental pollution.

[18]  A. Kasper-Giebl,et al.  Monitoring ammonia in urban, inner alpine and pre-alpine ambient air. , 2002, Journal of environmental monitoring : JEM.