Franco De Santis

Integrated ambient ozone evaluation by passive samplers and clover biomonitoring mini-stations

An ozone monitoring network was set up using passive samplers and biological mini-stations of two clones of white clover (Trifolium repens L. cv. Regal), NC-R (O(3)-resistant) and NC-S (O(3)-sensitive). This paper reports on a pilot study performed in the period June-October 1999 in the Rome municipal area by using five biomonitoring mini-stations and ozone passive samplers with a new nitrite based design. This combined methodology can be used to obtain information on the biological implications of the injury due to tropospheric ozone. The two techniques can integrate data for the short-medium period and can be placed in different urban and rural sites, proving to be a very useful tool for ozone concentration mapping.

Heterogeneous reactions of SO2 and NO2 on carbonaceous surfaces

Abstract Four different types of carbonaceous material (active carbon, graphitized carbon black, source samples from a power plant and from an urban heating boiler) were exposed to synthetic gas mixtures of SO2 and SO2 + NO2 in sub-ppm ranges at two different relative humidities (60 and 90% r.h.). The interaction of SO2 and NO2 with the carbonaceous materials led to sulfate and to three other products: NO, HONO and NO2−. Formation of NO and NO2− was observed only on active carbon while the other three materials yielded HONO. It was also found that NO2 enhances the deposition of SO2 only on the source sample from the power plant at 60% r.h., whereas the material from the urban heating boiler had no effect both at low and high r.h. The results obtained show that no general statements on the effect of NO2 on the heterogeneous reaction of SO2 on these carbonaceous materials can be made and also that NO2 reactions in the presence of SO2 on carbon-containing surfaces should be considered as a source for the production of HONO in the urban environment.

Measurements of nitric acid and ammonium salts in lower Bavaria

Abstract Nitric acid and ammonium-containing particulate species were measured by the annular denuder-filter pack technique at Manndorf, a rural site in South Germany, in July 1990. The analyses of filter packs indicated that nitrate was present as ammonium salt which mostly dissociated during sampling. Moreover, due to the NH+4/NO−3 ratios higher than unity found in back-up filters, NH4Cl was assumed to represent an appreciable fraction of the total particulate ammonium. Finally, the molar ratios NH+4/SO2−4 found on front (Teflon) filters, suggested a large predominance of (NH4)2SO4 among the different forms of sulphate. The concentration levels of gaseous HNO3 observed in the daytime were characterised by a maximum after midday, whereas particulate nitrate showed five times out of eight days an opposite trend with early afternoon minima. The total nitrate (HNO3+NH4NO3) showed in turn a diurnal pattern similar to that of sulphate. These findings led to the conclusion that a significant HNO3 production pathway involved the thermal dissociation of NH4NO3 rather than the reaction of NO2 with OH radical.

Measurement of Atmospheric Pollutants Relevant to Dry Acid Deposition

The transfer of acid gases and particles from the atmosphere to the earths surface, where they exert adverse environmental effects, is called acid deposition. Relevant removal processes occur during dry weather conditions, during the formation of clouds or by scavenging of falling rain or other hydrometeors. The first removal process is called acid dry deposition while the last two, known as rainout and washout, respectively, are lumped together into the phenomenon of acid wet deposition.

The use of a new passive sampler for ozone and nitrogen oxides monitoring in ecological effects research.

A simple, cost-effective diffusive sampler is described that is suitable for measuring parts per billion (ppb) levels of ozone and nitrogen oxides. The diffusive sampler makes use of nitrite for ozone determination whereas for nitrogen oxides and nitrogen dioxide an active carbon tissue impregnated with sodium carbonate is used. Nitrate and nitrite, the formation of which is proportional to the pollutant concentration and sampling duration, are the two species analysed, respectively. Diffusion tubes have the advantage of being a low- cost, convenient way of mapping spatial distributions and investigating long-term trends of ozone and nitrogen oxides. The method is extremely useful for assessing long-term concentrations such as the annual mean for nitrogen oxides, as required by the Daughter Directive 1999/30/EC. Field tests to validate the method have been carried out at an urban background location with co-located passive samplers and continuous measurements of O3 and NOx . An application in ecological effects monitoring for ozone is also presented.

Spatial Distribution of Urban Air Pollution in Lanzhou, China~!2009-07-23~!2010-01-27~!2010-04-02~!

Urban air quality, and its variability in space and time, is a critical issue for human exposure and health related studies. In this work, we investigated the intra-urban distribution of SO2, NOx, NO2, Benzene, Toluene, and Xylenes in ambient air in one of the worlds most polluted cities, Lanzhou, China. Measurements were contemporarily carried out at forty locations in four seasonal campaigns during the period 2005-2006. Diffusive samplers allowing a sampling period of one month were used. As a general finding, the selected air pollutant concentrations often exceeded the EU limit values, and varied significantly with space, time, and proximity to relevant point emission sources. A statistical analysis revealed that monthly air pollutant concentrations were normally distributed in space. This suggests that the spatial distribution of urban air pollution was governed by the spatial diffusion of emission sources, at least for its apparent average behaviour. This result might be relevant to link urban air quality measurements and human exposure assessment. To gain insights into the properties of the urban air pollution distribution in space, makes the assessment of homogeneous areas of air pol- lution in the urban area less critical - and, consequently, allows a proper selection of the sites where to monitor air quality for health-effects studies.

The measurement of the sink properties of triethanolamine (TEA) as a coating for collecting NO2 by using annular diffusion denuders

This study evaluates the use of triethanolamine (TEA) as an alternative to routinely used active carbon employed as a coating for collecting NO2 on a diffusion denuder. The study is based on laboratory experiments made by using annular diffusion denuders coated with TEA. The pre-exponential and exponential factors for the first term of the Gormley–Kennedy equation applied to annular geometry were estimated and compared with the corresponding values for other coatings used in previous studies published in the literature. It was found that TEA does not behave as a perfect sink in comparison with other coatings such as treated active carbon and alkaline guaiacol.