Development and field evaluation of a new diffusive sampler for hydrogen sulphide in the ambient air

A diffusive sampler for the determination of hydrogen sulphide (H2S) based on collection on a paper filter coated with silver nitrate followed by optical densitometric determination of the metal sulphide was developed. Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity and of interferents, precision and accuracy. The measured uptake rate for H2S was determined in experiments involving sampling at different concentration levels in comparison to a wet standard colorimetric technique. The precision of the measurements for co-located passive samplers was lower than 15%. The accuracy of the data collected is within 20% of the actual value measured by the wet method. The sampler is capable of reliable measurements of H2S at common levels of a polluted atmosphere in urban settings yielding average concentration levels over one month and beyond. Diffusive sampling can be adopted to analyse in detail the temporal and spatial trends of H2S concentration in ambient air and in specific historic buildings or in museums.

Monitoring the air quality around an oil refinery through the use of diffusive sampling

Diffusive sampling has been used to study the spatial distribution of SO(2), NO(2), NO(x), NH(3) and BTX (benzene, toluene and xylenes) near an oil refinery located in Falconara, Italy, over the period from March to October 2001. Three different categories of sampling sites (roadside, residential and background) were studied. In total, 56 sites were monitored. The results were evaluated on the basis of the limit values found in the European Directives. The results of the defined study indicate that the measured concentrations were substantially lower than the ambient air quality standard with the maximum concentrations being generally found much closer to emission sources. The monitoring method described here can be used to assess integrated concentration levels over long periods of time and to identify pollution "hotspots" where concentrations are likely to be consistently high. Identification of these hotspots may help to assess air quality and to implement proper action plans, especially in locations where industrial and urban pollution coexist.

Characterisation and evaluation of the emissions from the combustion of Orimulsion-400, coal and heavy fuel oil in a thermoelectric power plant

An experimental campaign was carried out in a thermoelectric power plant in Southern Italy in order to evaluate the emissions released during the utilisation of three different fuels, Orimulsion-400, coal and heavy fuel oil (HFO) with high content of sulphur. Macropollutant concentrations in the exhaust gases were recorded by the continuous monitoring system and the Institute on Atmospheric Pollution of the Italian National Research Council (CNR) carried out samplings and analysis of Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorodibenzo-p-dioxins (PCDD) and Polychlorodibenzofurans (PCDF), halogenidric acids and metals. The pollutant concentrations, mass flows and emission factors were compared. Each fuel met the air emission limits for all the pollutants. Coal showed the highest emission levels, whilst HFO and Orimulsion were fairly similar. NOx, SO2 and particulate matter showed constant concentration for all the fuels, while Orimulsion and HFO SO2 concentrations were critical at the highest operating power. Orimulsion showed the lowest PAHs values and PCDDs and PCDFs were much lower than the limits, for all the fuels. Particular attention must be paid with vanadium and nickel during Orimulsion utilisation. For these metals mass balances were carried out.

Laboratory development and field evaluation of a new diffusive sampler to collect nitrogen oxides in the ambient air

Diffusive samplers for the determination of NO(x) and NO2 based on collection on a coated carbon paper filter have been developed. NO is first oxidized to NO2 and then collected on the reactive surface. When NO2 and NOx samplers are exposed simultaneously, NO can be calculated by difference. The sampler has been derived from a Palmes design as recently modified by Bertoni et al. for the determination of BTX (benzene, toluene, xylenes). Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity, precision and accuracy. The samplers are capable of reliable measurements of the two species at common levels of a polluted atmosphere in urban settings yielding average concentration levels over 1 month and beyond. The uptake rate of NO2 was found to be 11.7 mL/min in a very good agreement (within 5%) with the value calculated from theory. The measured uptake rate for NO(x) was determined in experiments involving sampling at different concentration levels in comparison to chemiluminescence (CL) measurements. The precision of the measurements for co-located passive samplers was better than 5%. The accuracy of the data collected is within +/-20% of the actual value measured by CL. The laboratory and field results show that the NO(x) and NO2 samplers meet the data quality goal requested by the first EU Directive 1999/30/EU for these pollutants.

Monitoring of atmospheric pollutants by passive sampling for the protection of historic buildings and monuments

When considering the various possibilities to assess the effects of SO2 and NO2 on historic buildings and monuments, a distinction can be made according to the completeness of the scope of the assessment itself. A first approach can be limited to gathering data as they become available through the official bodies established under air quality legislation. This approach is based on a single point measurement where a "general purpose" monitoring station is located, often quite far from the monument to protect and often without investigating local and temporal variations. A more comprehensive assessment should include a generalisation that covers the territory. This can be made on the basis of the knowledge of the spatial distribution of concentrations and the knowledge of the causes of air pollution. Passive samplers allow the measurement of air quality in numerous sites and to assess the pollutant spatial distribution over a large area with a high resolution. As an application of the method, the spatial distribution of SO2 and NO2 in the city of Siracusa, Sicily, Italy, has been studied to identify areas of high deposition fluxes in relation to the protection of buildings and monuments of the historic centre.

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.

Physico-chemical and biological monitoring as integrated tools in evaluating tropospheric ozone in urban and semi-rural areas

The relationship between tropospheric ozone and growth of radish plants during Summer 1991 in an urban and in a semi-rural site located in Central Italy are analyzed. Largest ozone concentrations and largest radish growth reductions are found in the semi-rural site. The importance of integrating the information on physico-chemical processes with biological monitoring to estimate the impact of photochemical oxidants on natural and cultivated vegetation in the Mediterranean area is discussed. Results from photochemical episodes are also reported in terms of physico-chemical evaluation of atmospheric pollutants.