The effect of absorbent grid preparation method on precision and accuracy of ambient nitrogen dioxide measurements using Palmes passive diffusion tubes

A few studies have suggested that the precision and accuracy of measurement of NO(2) by Palmes-type passive diffusion tube (PDT) are affected by the method of preparation of the triethanolamine (TEA) absorbent coating on the grids. Theses studies have been quite limited in extent and have tended to evaluate PDT accuracy as zero bias between PDT NO(2) value and the exposure-averaged NO(2) determined by co-located chemiluminescence analyser. This ignores the well-documented intrinsic systematic biases on PDT-derived NO(2), such as within-tube chemistry and exposure-duration nitrite loss, which may lead to non-zero bias values irrespective of effects of TEA absorbent preparation method on PDT accuracy. This paper reports on a statistical analysis of a large dataset comprising 680 duplicated PDT exposures spanning 146 separate exposure periods, spread over five urban exposure locations and a number of years. In each exposure period, PDTs prepared by between four and six different grid preparation methods were simultaneously compared. The preparation methods used combinations of the following: acetone or water as the TEA solvent; 20% or 50% as %TEA in the solution; and application of TEA solution by dipping grids for several minutes in the solution before drying and tube assembly, or by pipetting 50 microL of solution directly onto grids already placed in the PDT cap. These represent the range of preparation procedures typically used. Accuracy was evaluated as maximised nitrite capture within an exposure. Data were analysed by general linear modelling including examination of interaction between different aspects of grid preparation method. PDT precision and accuracy were both significantly better, on average, when the PDT grids were prepared by dipping in TEA solution, and neither solvent or %TEA used for the dipping solution were important. Where PDT preparation by pipetting TEA solution onto grids is to be used, better performance was obtained using 20% TEA in water. A systematic positive bias in PDT measure of NO(2), consistent with within-tube oxidation of NO to NO(2) and independent of preparation method, was again evident in this work.     

Reliability of nitrogen dioxide passive diffusion tubes for ambient measurement: in situ properties of the triethanolamine absorbent

Factors concerning NO2 uptake by the absorbent triethanolamine (TEA) in NO2 diffusion tubes are examined. Although the nominal freezing point of TEA is 17.9-21.2 degrees C, we show that, for a range of aqueous TEA solutions (0-20%, H2O), no freezing occurs even at -10 degrees C. Therefore NO2 collection efficiency is unlikely to be impaired by low temperature exposure. The recovery of TEA from the meshes of exposed samplers is determined as approximately 98%, even after 42 days, showing that the stability in situ of TEA is unaffected by long-term exposure. A model of a diffusion tube sampling array for simultaneous exposures, with a 0.1 m sampler spacing, shows that NO2 uptake by individual samplers is not affected by the presence of neighbouring tubes in the array. This is confirmed by sampler precision at two Cambridge sites. Four sampler preparation methods are compared for differences in NO2 uptake of exposed samplers. All methods employ TEA as absorbent, transferred by either dipping meshes in a TEA-acetone solution or pipetting aliquots of a TEA-H2O solution onto the meshes. For samplers prepared by three of the methods, no difference in NO2 uptake is found, but for samplers prepared using a 50% v/v TEA-H2O solution, a mean reduction of 18% is found. Student's t-tests show that the difference is highly significant (P < or = 0.001). Reasons for the difference are discussed.     

Systematic Biases in Measurement of Urban Nitrogen Dioxide using Passive Diffusion Samplers

Measurement of nitrogen dioxide using passivediffusion tube over 22 months in Cambridge, U.K. areanalysed as a function of sampler exposure time, andcompared with NO₂ concentrations obtained from aco-located chemiluminescence analyser. The averageratios of passive sampler to analyser NO₂ at acity centre site (mean NO₂ concentration 22 ppb)are 1.27 (n = 22), 1.16 (n = 34) and 1.11 (n = 7) forexposures of 1, 2 and 4-weeks, respectively. Modellingthe generation of extra NO₂ arising from chemicalreaction between co-diffusing NO and O₃ in thetube gave a ratio (modelled/measured) of 1.31 for1-week exposures. Such overestimation is greatest whenNO₂ constitutes, on average, about half of totalNO_x (= NO + NO₂) at the monitoring locality.Although 4-week exposures gave concentrations whichwere not significantly different from analyserNO₂, there was no correlation between thedatasets. At both the city-centre site and anothersemi-rural site (mean NO₂ concentration 11 ppb)the average of the aggregate of four consecutive1-week sampler exposures or of two consecutive 2-weeksampler exposures was systematically greater than fora single 4-week exposure.The results indicate two independent and opposingsystematic biases in measurement of NO₂ bypassive diffusion sampler: an exposure-timeindependent chemical overestimation with magnitudedetermined by local relative concentrations of NO andO₃ to NO₂, and an exposure-time dependentreduction in sampling efficiency. The impact of theseand other potential sources of systematic bias on theapplication of passive diffusion tubes for assessingambient concentrations of NO₂ in short (1-week)or long (4-week) exposures are discussed in detail.     

Development of a personal monitoring method for nitrogen dioxide and sulfur dioxide with Sep-Pak C18 cartridge sampling and ion chromatographic determination

Personal monitoring methods for the determination of hourly integrated concentrations of NO2 and SO2 in ambient air have been developed. Triethanolamine (TEA)-impregnated C18 Sep-Pak cartridges were used to collect NO2 and SO2 simultaneously. After sampling, NO2 and SO2 as their nitrite, nitrate, sulfite and sulfate analogues were stripped from the cartridges with a solution of 5% methanol in distilled, deionized water (DDW) and then determined by ion chromatography. Laboratory tests were conducted to evaluate the sampling rate, collection and recovery efficiencies, breakthrough volumes, absorption capacity, interference and sample stability on the cartridge during storage. NO2 and SO2 detection limits of 0.3 and 0.4 ppb respectively for 1 h samples were obtained. Recoveries for both NO2 and SO2 exceeded 85%.     

Simultaneous determination of atmospheric sulfur and nitrogen oxides using a battery-operated portable filter pack sampler

We developed a method to analyze atmospheric SO(x) (particulate SO(4)(2-)+ gaseous SO(2)) and NO(x) (NO + NO(2)) simultaneously using a battery-operated portable filter pack sampler. NO(x) determination using a filter pack method is new. SO(x) and NO(x) were collected on a Na(2)CO(3) filter and PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl) + TEA (triethanolamine) filters (6 piled sheets), respectively. Aqueous solutions were then used to extract pollutants trapped by the filters and the resulting extracts were pre-cleaned (e.g. elimination of PTIO) and analyzed for sulfate and nitrite by ion chromatography. Recoveries of SO(2) and NO(x) from standard pollutant gases and consistency of the field data with those from other instrumental methods were examined to evaluate our method. SO(x) and NO(x) could be analyzed accurately with determination limits of 0.2 ppbv and 1.0 ppbv (as daily average concentrations), respectively. The sampler can determine SO(x) and NO(x) concentrations at mountainous or remote sites without needing an electric power supply.     

Use of real-time sensors to characterise human exposures to combustion related pollutants

Concentrations of black carbon and nitrogen dioxide have been collected concurrently using a MicrAeth AE-51 and an Aeroqual GSS NO(2) sensor. Forty five sampling events with a duration spanning between 16 and 22 hours have collected 10,800 5 min data in Birmingham (UK) from July to October 2011. The high temporal resolution database allowed identification of peak exposures and which activities contributed the most to these peaks, such as cooking and commuting. Personal exposure concentrations for non-occupationally exposed subjects ranged between 0.01 and 50 μg m(-3) for BC with average values of 1.3 ± 2.2 μg m(-3) (AM ± SD). Nitrogen dioxide exposure concentrations were in the range 相似文献   

Evaluation of the best compromise between the urban air quality monitoring resolution by diffusive sampling and resource requirements

The need to collect data representative of overall urban pollution is all-important in order to monitor the population exposure. High spatial resolution monitoring using diffusive samplers allows studying of the urban pollutant distribution, thus enabling deeper investigation of their generation and diffusion mechanisms. Nevertheless, such a monitoring campaign has a certain cost. In this study we point out how to find the best compromise between the number of necessary measurements and the affordable costs for monitoring campaigns. We also describe an innovative method for the proper design of a fixed urban monitoring network by means of preliminary high spatial resolution campaigns using diffusive samplers. Four European capital cities (Dublin, Madrid, Paris and Rome) were monitored six times, each time for seven days. Benzene, toluene, ethylbenzene, xylenes (BTEX) and NO(2) concentrations were measured at 146 sites in Dublin, 293 in Madrid, 339 in Paris and 290 in Rome. Multiscale grids have been drawn which ranged in mesh size from 500 m to 2 km. The statistical processing of data produced a twofold result: the creation of isoconcentration maps with geostatistical procedures, and an algorithm aimed at locating the minimum number of sampling sites where the fixed monitoring stations should be placed. Average urban levels estimated on the basis of these selected sites differ by less than 8% from those calculated on the whole populations of the sampled points. The aim of this work is to investigate how far the resolution of a monitoring campaign of urban pollution by diffusive sampling can be reduced, thus making the monitoring less expensive in terms of human and financial resources, while preserving the same quality of the results that could be achieved with a higher resolution. We found that there is no significant loss of information when the resolution of the monitoring grid for BTEX is lowered to a mesh size of 1.85 km, that is a sampling site each 3.4 km(2), and that the minimum number of sampling sites to be used is N = 0.29 A, where A is the urban surface to be monitored (in km(2)). As the spatial distribution of NO(2) is less sensitive to the distance from the emission source than that of BTEX, this relationship could be retained as a valid lower limit for the mesh grid size also for NO(2) monitoring.     

A physicochemical model of sorption processes in NO2 passive sampling with air humidity effects

Aqueous triethanolamine (TEA) solutions are widely used as sorption medium for passive sampling of ambient NO₂, with NO₂ trapped and accumulated as nitrite ion. The results of test measurements of ambient NO₂ concentrations using passive sampling method showed that the simple approach commonly used to describe passive sampling process might lead to substantial systematic errors. Presented in the article is a new physicochemical model of the process of passive sampling of gaseous NO₂, with aqueous TEA solution used as a trapping medium. The model is based on the available results of experimental studies of interaction of gaseous NO₂ with TEA/water solutions. The key principles underlying the model are: (1) when absorbed by a trapping solution, NO₂ forms nitrite ion only on the condition that TEA is hydrated; (2) coefficient of conversion of NO₂ to NO ₂ ^? is equal to one when reacting with hydrated TEA; and (3) the fraction of hydrated TEA molecules depends on air humidity at the moment of measurement. Validation of the model was made using the data of the field measurements carried out in the Middle Urals in 2007–2009. The new model was used to calculate average NO₂ concentrations. Concentrations calculated agreed well with the results obtained by reference methods. The difference between the datasets was statistically insignificant.     

低浓度SO_2检测管的研制

通过对常见的几种检测管法的比较，筛选出灵敏度较高的亚硝基铁氰化钠法；同时筛选出载体为６０—８０目的素陶瓷，指示剂浓度为２０％。玻璃管内径为２．０—２．３ｍｍ，采气速度为０．３（Ｌ／ｍｉｎ），采样体积为１２Ｌ，以此条件进行实验．结果表明，检测管变色长度对应ＳＯ２浓度的相关性很好；变异系数均小于１１０％，检测的重现性较好。检测管的测定值与理论值的平均相对误差为５．０９％（＜±１５％），最大相对误差为７．１３％（＜±２５％），准确度较高．测定结果可靠；与化学法比较，两者无显著性差异；浓度小于０．１５ｍｇ／ｍ３的Ｈ２Ｓ及浓度小于０．０１ｍｇ／ｍ３的ＮＯ２对ＳＯ２检测管无干扰．     

Non-invasive measurement of carbon monoxide burden in Guatemalan children and adults following wood-fired temazcal (sauna-bath) use

The use of wood-fired steam baths, or temazcales, is a potentially dangerous source of CO exposure in Guatemalan Highland communities where adults and children use them regularly for bathing, relaxation, and healing purposes. Physical characteristics of children predispose them to absorb CO faster than adults, placing them at greater exposure and health risks. Efforts to quantify temazcal exposures across all age groups, however, have been hampered by the limitations in exposure measurement methods. In this pilot study we measured COHb levels in children and adults following use of the temazcal using three field-based, non-invasive CO measurement methods: CO-oximetry, exhaled breath, and by estimation of COHb using micro-environmental concentrations and time diaries. We then performed a brief comparison of methods. Average CO concentrations measured during temazcal use were 661 ± 503 ppm, approximately 10 times the 15 min WHO guideline. Average COHb levels for all participants ranged from 12-14% (max of 30%, min 2%), depending on the method. COHb levels measured in children were not significantly different from adults despite the fact that they spent 66% less time exposed. COHb measured by CO-oximetry and exhaled breath had good agreement, but precision of the former was affected substantially by random instrument error. The version of the field CO-oximeter device used in this pilot could be useful in screening for acute CO exposure events in children but may lack the precision for monitoring the burden from less extreme, but more day-to-day CO exposures (e.g. indoor solid fuel use). In urban settings, health effects in children and adults have been associated with chronic exposure to ambient CO concentrations much lower than measured in this study. Future research should focus on reducing exposure from temazcales through culturally appropriate modifications to their design and practices, and targeted efforts to educate communities on the health risks they pose and actions they can take to reduce this risk.     

Viable fungi and bacteria in personal exposure samples in relation to microenvironments

Personal exposures to viable fungi and bacteria were compared with the concentrations being assessed by stationary samplers in home and workplace microenvironments. A random sample of 81 elementary school teachers in eastern Finland performed two 24-hour measurement periods in wintertime. Concentrations and prevalences of viable fungi and bacteria on the collection filters were determined by cultivation method. The geometric mean concentration was 3-12 cfu m(-3) for total viable fungi, 0.6-3.7 cfu m(-3) for Penicillium and mainly under 1 cfu m(-3) for other fungi. The samples with higher fungal concentrations also had higher diversity of fungi than samples with lower concentrations. The total number of fungal genera recovered was 39 for personal, 34 for home and 23 for work samples. The variation in concentration of Penicillium explained even 25-95% of the variations of total fungal concentration in personal exposure, home and workplace environments. There was an association between personal exposure and home concentration of viable fungi and between personal exposure and home and work concentrations of viable bacteria. Personal exposure and home concentrations of fungi were higher in rural areas than in urban areas. Our results also indicate that presence of a certain fungus in a microenvironment does not necessarily mean similar findings in personal exposure samples.     

武汉市城区大气监测优化布点研究

对武汉市城区网格布点实测ＴＳＰ、ＳＯ２获取了城区大气污染总体水平的数据，运用Ｆｉｓｈｅｒ最优分割方法，求出城区５个优化测点数，运用模糊聚类方法对武汉城区４８个网格测点的ＴＳＰ、ＳＯ２污染强度置信水平进行聚类；运用日均值和百分位数逼近方法检验；结合优化布点原则等，最终确定的ＴＳＰ、ＳＯ２的５个优化测点能集中反映城区大气环境中ＴＳＰ、ＳＯ２的总体污染水平。     

Diurnal, seasonal and weekdays–weekends variations of ground level ozone concentrations in an urban area in greater Cairo

Ground level ozone (O3) concentration was monitored during the period of December 2004 to November 2005 in an urban area in Greater Cairo (Haram, Giza). During the winter and summer seasons, nitrogen dioxide (NO2) and nitric oxide(NO) concentrations and meteorological parameters were also measured. The mean values of O3 were 43.89, 65.30, 91.30 and 58.10 ppb in daytime and 29.69, 47.80, 64.00 and 42.70 ppb in whole day (daily) during the winter, spring, summer and autumn seasons, respectively. The diurnal cycles of O3 concentrations during the four seasons revealed a uni-modal peak in the mid-day time, with highest O3 levels in summer due to the local photochemical production. The diurnal variations in NO and NO2 concentrations during the winter and summer showed two daily peaks linked to traffic density. The highest levels of NOx were found in winter. Nearly, 75%, 100%, 34.78% and 52.63% of the mean daytime concentrations of O3 during spring,summer, autumn and the whole year, respectively, exceeded the Egyptian and European Union air quality standards (60 ppb) for daytime (8-h) O3 concentration. About, 41.14% and 10.39% of the daytime hours concentrations and 14.93% and 3.77% of the daily hour concentrations in summer and the whole year, respectively, exceeded the Egyptian standard (100 ppb) for maximum hourly O3 concentration, and photochemical smog is formed in the study area (Haram) during a periods represented by the same percentages. This was based on the fact that photochemical smog usually occurs when O3 concentration exceeds 100 ppb. The concentrations of O3 precursors (NO and NO2) in weekends were lower than those found in weekdays, whereas the O3 levels during the weekends were high compared with weekdays. This finding phenomenon is known as the "weekend effect". Significant positive correlation coefficients were found between O3 and temperature in both seasons and between O3 and relative humidity in summer season, indicating that high temperature and high relative humidity besides the intense solar radiation (in summer) are responsible for the formation of high O3 concentrations.     

Laboratory and field comparison of measurements obtained using the available diffusive samplers for ozone and nitrogen dioxide in ambient air

This study presents an evaluation of the extent of differences between measurements performed by O(3) and NO(2) diffusive samplers and by the reference methods for diffusive samplers commercially available. The tests were performed in an exposure chamber under extreme conditions of controlling factors and under field conditions. For NO(2), the results of the laboratory experiments showed that most of the diffusive samplers were affected by extreme exposure conditions. The agreement between the samplers and the reference method was better for the field tests than for the laboratory ones. The estimate of the uptake rate for the exposure conditions using a model equation improved the agreement between the diffusive samplers and the reference methods. The agreement between O(3) measured by the diffusive samplers and by the reference method was satisfactory for 1-week exposure. For 8-hour exposures, the diffusive samplers with high uptake rates quantified better the O(3) concentration than the samplers with low uptake rates. As for NO(2), the results of the O(3) field tests were in better agreement with the reference method than the ones of the laboratory tests. The field tests showed that the majority of diffusive samplers fulfils the 25% uncertainty requirement of the NO(2) European Directive and the 30% uncertainty requirement of the O(3) European Directive for 1-week exposure.     

Influence of environmental parameters on the accuracy of nitrogen dioxide passive diffusion tubes for ambient measurement

Two studies at three sites in the UK provided confirmation that systematic positive bias in NO2 diffusion tube measurement occurred because of changes to "within-tube" chemistry, rather than eddy diffusion at the mouth of the tube. In the first study in Cambridge, UK, sampler overestimation for 1 and 2 week exposures was compared to corresponding time-averaged monitor measurements (NO-NO2-NOx, O3) and weather variables. Noninearity between sampler and monitor NO2 measurements was interpreted in terms of spatial and temporal variations in relative and absolute availability of NO, NO2 and O3 at the site. A maximum overestimation occurred for an exposure mean NO2/NOx approximately 0.5. The separate contributions of reduced NO2 photolysis and eddy diffusion were compared in Study II using samplers of two materials, acrylic and quartz, and of different lengths (40, 55, 71 and 120 mm) at three sites: Norwich background, Cambridge intermediate, London kerbside. For compared sites, NO2 measured by acrylic samplers was significantly higher than for equivalent quartz samplers. For quartz samplers [NO2]mean was only just above the monitor at Norwich and London; sampler/monitor NO2 = 1.04 (P = 0.59) and 1.01(P = 0.76), respectively. For acrylic samplers the order of [NO2]mean was 40 mm > 120 mm > 71 mm > or = 55 mm. Excepting 40 mm samplers, this accords with a chemical bias where co-diffusing NO and 03 molecules in longer tubes have more time to react to form excess NO2. Bias in 40 mm samplers is discussed. Eddy diffusion is negligible for standard samplers because [NO2]mean was equivalent for 55 mm and 71 mm acrylic samplers and close to monitor NO2 for 71 mm quartz tubes. Both studies showed that sampler accuracy was dependent on location. Significantly, overestimation was greatest (approximately 3-4 ppb) where the NO2 annual mean was approximately 20 ppb, close to the UK and EU air quality standard of 21 ppb.     

How does exposure to nitrogen dioxide compare between on-road and off-road cycle routes?

This study demonstrates a simple method to estimate the extent to which the exposure of cyclists to NO(2) is reduced by using off-road cycle routes rather than on-road cycle routes. Diffusion tubes were used to measure monthly NO(2) concentrations on three paired sets of on- and off-road cycle journeys in and around the City of York in August and September 2008. These measurements were combined with estimates of journey times to calculate time-weighted average concentration and exposure on each route. The average concentration of NO(2) was significantly reduced by a mean of 37.5% when off-road routes were used in place of on-road routes and, despite the longer journey times for off-road routes, exposure was also significantly reduced by a mean of 25.5%. The method described in this study could be adopted more widely to provide a cost effective and simple means of assessing the benefits of alternative cycle routes that are provided by Local Authorities.     

TEA(三乙醇胺)挂片测定空气中NO2的滤膜制备方法

介绍了一种用于TEA挂片测定NO2的滤膜制备方法,解决了原方法中存在的滤膜空白值偏高且不稳定的问题.实验结果表明,该方法可用于大面积、多点位同步监侧中大批量滤膜的制备.     

Measurement of styrene-7,8-oxide and other oxidation products of styrene in air

Styrene-7,8-oxide (SO) is generated at low concentrations from the oxidation of styrene during the processing of reinforced plastics. Since exposure to SO has important health implications, we developed air sampling and analytical methods to measure low levels of airborne SO in the presence of styrene and its other oxidation products, namely phenylacetaldehyde (PAA) and acetophenone (AP). Both active and passive air monitors were used. The active sampling method, which employed adsorption on Tenax, was suitable for measuring SO, PAA and AP but had limited capacity for styrene due to breakthrough. The passive monitor employed a carbon adsorbent and was suitable for measurement of styrene and SO but not PAA and AP due to poor recovery. After sampling, the analytes were extracted from the adsorbents with ethyl acetate and measured by gas chromatography with flame ionization detection or mass spectrometry. By maintaining the injection port at 70 degrees C, the thermal rearrangement of SO to PAA was minimized. Recovery of styrene and SO from the passive monitor depended upon loading and was corrected by linearization of the Freundlich isotherm. The limits of detection for SO, PAA, and AP were 0.2 ppb using the active monitor, and for SO was 1 ppb using the passive monitor. The sampling precision for SO (RSD from personal measurements) was 5.0% for the passive monitor and was 13.4% for the active monitor over a range of exposures from 5-150 ppb. The corresponding precision for styrene was 5.3% for the passive monitor for levels ranging from 1.2 to 104 ppm. Measurements of 235 personal exposures with the active monitor in 12 facilities manufacturing fiberglass-reinforced plastics (FRP) showed that levels of AP and PAA were below 7.8 ppb and 5 ppb, respectively. In contrast, SO averaged 30.4 ppb (SE=2.4) in these FRP facilities, ranging from below 0.2 ppb to 190 ppb. The active monitor was also used to detect airborne SO at levels of approximately equals 1 ppb in one facility manufacturing styrene butadiene rubber, suggesting that SO is generally present during the polymerization of styrene. Personal passive monitoring in the 12 FRP facilities (n = 657) revealed mean concentrations of styrene ranging between 1.8 and 55.4 ppm, and for SO between 1.7 and 62.6 ppb. The ratio of the mean styrene level to the mean SO level varied between 449:1 and 1,635:1 among the 12 FRP facilities.     

Laboratory and field validation of a combined NO2-SO2 Radiello passive sampler

A combined NO2-SO2 Radiello radial-type diffusive sampler was validated under controlled laboratory conditions and compared with NO2-SO2 results of 3 other type of samplers in a field comparison at two locations Ghent-Mariakerke and Borgerhout in Flanders. Laboratory exposures at different temperatures (-5, 10 and 30 degrees C) and relative humidities (0, 50 and 80% RH) in combination with varying concentration levels and exposure times were carried out, with a focus on extreme conditions. Concentration level and exposure time were changed together following suppliers linear working range of samplers and assuring absolute amounts of compounds on the sampler corresponding to those of environmental levels. The average uptake rate for NO2 for 24 hour exposures at 10 degrees C and 50% RH and tested concentration levels (+/-73, 146 and 293 ppb NO2) was 0.076 +/- 0.011 ng ppb(-1) min(-1). Uptake rates during all experiments were lower than the uptake rate given in the instruction manual of the sampler. A significant effect of temperature and relative humidity on NO2 uptake rate was observed. The temperature effect from 10 to 30 degrees C corresponds to the temperature effect given by the supplier of the samplers. High relative humidity (70 to 80%) caused a strong non-reproducible decrease of uptake rate for NO2 at 24 hour experiments but this effect was not observed at longer exposures except for the tests at -5 degrees C. At the tested temperature below zero in combination with high relative humidity the sampler showed anomalous behaviour for NO2. The possible effect of concentration level and exposure time for NO2 needs further research. The average uptake rate for SO2 calculated from all exposures is 0.478 +/- 0.075 ng of sulfate ion each ppb min of SO2 and accords to suppliers uptake rate. No clear effects of temperature, relative humidity or concentration level/exposure time on the uptake rate for SO2 were found, partly due to the large scatter of results. Although NO2 accuracy of Radiello samplers was better during field campaigns than during laboratory validation, IVL and OGAWA samplers gave better results for NO2. In the field, IVL samplers showed best agreement with the continuous analyzers for both NO2 and SO2.     

Is PM10 mass measurement a reliable index for air quality assessment? An environmental study in a geographical area of north-eastern Italy

The aim of this study was to measure the concentration of some metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Ti) in PM(10) samples collected in one urban and one industrial site and to assess that PM(10) total mass measurement may be not sufficient as air quality index due to its complex composition. Metals were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and differential pulsed anodic stripping voltammetry (DPASV). The measured concentrations were used to calculate the content of metals in the PM(10) total mass, and to estimate the enrichment factors and the correlations between PM(10), metal concentrations and meteorological data for the two sites. The mean PM10 concentration during the sampling period in the urban site exceeded the annual European Union (EU) standard (40 microg/m(3)) and, for some sampling days, the daily EU standard (50 microg/m(3)) was also exceeded. In opposite, both EU standards were never exceeded in the industrial site. The overall metal content was nearly double in the industrial site compared to the urban one, and the mean Ni concentration exceeded the EU annual limit value (10 ng/m(3)). The metals with the highest enrichment factor were Cd, Cu, Ni and Pb for both sites, suggesting a dominant anthropogenic source for these metals. Metal concentrations were very low and typical of rural background during Christmas holidays, when factories were closed. PM(10) total mass measurement is not a sufficient air quality index since the metal content of PM(10) is not related to its total mass, especially in sites with industrial activities. This measurement should be associated with the analysis of toxic metals.