Narrow Results

The recent methodological developments and particularly the recent applications of nuclear analytical techniques (mainly PIXE and INAA) for measuring minor and trace elements in various types of environmental samples are reviewed. The sample types covered range from atmospheric aerosols over miscellaneous air topics (e.g., emissions, wet and dry deposition) to various solid environmental materials and samples from the aqueous environment. A fairly comprehensive overview is given of the research on atmospheric aerosols. For the other sample types, the trends in the research are indicated and selected examples of applications are presented. It is shown that the nuclear analytical techniques are very valuable for the multielement analysis of solid environmental samples. Furthermore, PIXE is particularly suitable for analyzing atmospheric aerosol samples.

A high time-resolution system for dry deposition measurement was developed. This employed a modified beta-attenuation dust monitor and PIXE analysis in order to characterize the process of dry deposition. It was demonstrated that PIXE analysis can detect the presence of Al, Si, S and Fe in dry deposition samples for a one-hour sampling time.

The status of current knowledge on size-dependent aerosol removal by dry and wet processes, including dry deposition and impaction and nucleation scavenging, is reviewed. The largest discrepancies between theoretical estimations and measurement data on dry deposition and below-cloud scavenging are for submicron particles. Early dry deposition models, which developed based on chamber and wind tunnel measurements, tended to underestimate dry deposition velocity (V_d) for submicron particles by around one order of magnitude compared to recent field measurements. Recently developed models are able to predict reasonable V_d values for submicron particles but shift unrealistically the predicted minimum V_d to larger particle sizes. Theoretical studies of impaction scavenging of aerosol particles by falling liquid drops also substantially underestimate the scavenging coefficients for submicron particles. Empirical formulas based on field measurements can serve as an alternative to the theoretical scavenging models. Future development of size-resolved impaction scavenging models needs to include more precipitation properties (e.g., droplet surface area) and to be evaluated by detailed cloud microphysical models and available measurements. Several recently developed nucleation scavenging parameterizations for in-cloud removal of interstitial aerosol give comparable results when evaluated against parcel models; however, they need to be verified once suitable field measurements are available. More theoretical and field studies are also needed in order to better understand the role of organic aerosols in the nucleation scavenging process.

Tropospheric ozone (O₃) is nowadays recognized as the most important widespread air pollutant, deteriorating materials and causing adverse effects to living organisms. It occurs at levels potentially phytotoxic, thus influencing cultivated plants and natural ecosystems. In this chapter, we describe the mechanisms of O₃ formation in the stratosphere and the troposphere, its spatial (longitudinal and latitudinal) distribution, its trends, as well as the diurnal and seasonal patterns of its concentrations. Furthermore, the role of plants as indirect “sources” (through the biogenic volatile organic compounds emissions) and “sinks” (through wet and dry deposition) are discussed.