摘要:

Study of the eVect of pH, salinity and DOC on fluorescence of synthetic mixtures of freshwater and marine salts Valdemar I. Esteves,* Eduarda B. H. Santos and Armando C. Duarte University of Aveiro, Department of Chemistry, 3810 Aveiro, Portugal Received 29th March 1999, Accepted 28th April 1999 In order to provide support for the discussion of the fate of organic matter in estuaries, a laboratory simulation was performed by changing freshwater ionic strength, pH and organic matter content.The change in spectroscopic characteristics caused by variations in salinity, pH and organic matter concentration in the filtered samples was observed by UV-Vis and fluorescence spectroscopy. The increase in emission fluorescence intensity of dissolved organic matter (DOM) due to increasing salinity (in the range 0 to 5 g l-1) is aVected by the pH of the samples. The emission fluorescence intensity at the three maxima observed in the fluorescence spectra, is linearly correlated with dissolved organic carbon (DOC) concentration at several salinity values in the same sample.The increase in organic matter concentration caused a shift in the emission peak wavelength at 410 nm for several salinity values.We concluded that it is necessary to take into account the influence of salinity and pH on emission fluorescence of dissolved organic matter if it is to be used as a tracer in estuarine or near shore areas.Methodology for studying the eVects of the environmental Introduction parameters The behaviour of riverine dissolved organic carbon (DOC) Adequate amounts of freeze dried sea salts were added to when entering an estuarine zone has been studied.Some aliquots of filtered freshwater in order to obtain samples with authors1,2 suggested that fractions of DOC are removed by salinity values of 0 (no adjustment), 2, 5, 10, 15, 25 and mechanisms such as flocculation, precipitation, microbial 35 g l-1. The samples were then adjusted to pH 8.0 with NaOH degradation and particulate adsorption while some others3–5 and HCl and left overnight in a darkroom.The following day, found that DOC shows an overall conservative behaviour samples were filtered through muZed (400 °C, 24 h) GF/F in estuaries. (Whatman, Maidstone, Kent, UK) filters. Filtered samples Fluorescence spectroscopy has been extremely useful as a were characterised by spectral analysis in a UV-Vis spectropho- technique for monitoring dissolved organic matter3 in freshtometer [Shimadzu (Du� sseldorf, Germany) Model UV 2101 water, estuarine or nearshore areas.Both UV-Vis and fluores- PC] and in a fluorescence spectrophotometer (JASCO, Tokyo, cence spectroscopy have also been used to quantify DOC in Japan, Model FP-770).aquatic environments.6,7 In this paper, we report the results Emission fluorescence intensities were measured at 410 nm, obtained in laboratory experiments of the eVects on UV-Vis 440 nm and 460 nm for an excitation wavelength of 360 nm, and fluorescence spectra of changing pH, salinity and DOC which corresponded to the three maxima for the freshwater concentration of freshwater mixed with prepared salt water.sample. The width of the excitation and emission lines was 5 nm. The wavelength accuracy and repeatability were Experimental ±1.5 nm and ±0.3 nm respectively (data from the manufacturer). Preparation of freeze dried salts from coastal water For each salinity value a sample of filtered water was Five litres of seawater from a non-polluted beach (Costa subsampled to obtain pH values of 7.0, 8.0 (no pH correction) Nova, Portugal ) were filtered [0.45 mm Gelman (Ann Arbor, and 8.5 with NaOH and HCl.The samples obtained were MI, USA) membrane filter]. In order to oxidize organic matter characterized by fluorescence spectroscopy. to CO2, the seawater was irradiated with UV radiation In order to study the eVect of dilution, for each salinity (1000 W; l=254 nm) over 12 h: six drops of H2O2 (30% by value, the samples at pH 8.0 were diluted with deionized water volume) were added to 200 ml quartz tubes filled with seawater, prepared at the same salinity as the samples and again and the seawater was exposed to UV radiation.After a 12 h characterized by fluorescence spectroscopy. exposure, the seawater was freeze dried to obtain the salts The fluorescence spectra were corrected for wavelength used for the preparation of solutions with diVerent salinities.dependent eVect using a dynode-feedback control system.8 The same procedure was performed with a series of blanks [Millipore (Milford, MA, USA) Milli-Q 50]. Sampling of freshwater Ten litres of freshwater were sampled in glass containers at Results and discussion Frei-Gil on the Mira channel of the Aveiro lagoon, Portugal.Conductivity, pH and temperature were measured in the field. The eVect of salinity on the UV-Vis spectra The sample was filtered (Gelman 0.45 mm) in the laboratory. Dissolved organic carbon (DOC) of this filtered sample was The variations in absorbance with salinity of a freshwater sample are shown in Fig. 1 where the UV-Vis absorbance of measured using a Dohrmann (Santa Clara, CA, USA) DC-180 Carbon analyser. filtered samples is represented as a function of salinity for two J. Environ. Monit., 1999, 1, 251–254 251Fig. 1 EVects of salinity on freshwater absorbance (250 and 350 nm). Fig. 2 Emission fluorescence spectra of a freshwater sample for an excitation wavelength of 360 nm.wavelengths. A general trend is observed for the wavelengths studied: the UV-Vis absorbance decreases as the salinity increases. The DOC value of the samples was 3.5 mg l-1 of C, before increasing salinity. As the salinity was increased there was a visible increase (not measured) of particulate matter content retained in the GF/F filters associated with the decrease in UV-Vis absorbance of filtered samples.This suggests flocculation of dissolved organic matter (DOM). The extent of decrease in the UV-Vis absorbance due to the salinity is independent of wavelength: for instance, for wavelengths of 365 nm and 250 nm the UV-Vis absorbance decrease was 11% and 5%, respectively, calculated for a salinity value of 35 g l-1. Assuming a strong correlation between DOC and UV-Vis absorbance at 250 nm,7,9 the results confirm the occurrence of flocculation of DOM during mixing of freshwater and seawater.According to Sholkovitz1 3% to 11% of the river DOM is flocculated when in contact with seawater, which is in concordance with our results. The eVect of salinity and pH on emission fluorescence spectra A typical emission fluorescence spectrum of river water is shown in Fig. 2; three peaks are easily identified at wavelengths of 410, 440, and 460 nm. The change in salinity and pH of Fig. 3 Emission peak wavelength (lexc=360 nm), as a function of freshwater did not cause peak wavelength displacement in DOC concentration. Each point is the data average for salinities 0, 5, 15, and 35 g l-1. Confidence interval has a 95% confidence level.fluorescence emission spectra. However, an increase in DOC content for several salinity values caused a small but consistent shift in the first peak wavelength (attributed to Raman scattering or superimposed with the Raman peak) to higher in order to obtain samples with diVerent salinities and the same amount of organic matter. As shown in Fig. 4, the wavelengths as shown in Fig. 3.Correlating the DOC concentration with the wavelength of the maximum of the first peak increase in fluorescence intensity due to the increase in salinity is clear in the range of 2 to 5 g l-1 and nearly constant for of 32 solutions in a range of salinities between 0 and 35 g l-1 gave the equation y=(4.07×102)+0.75x, and r2=0.926, salinities greater than 5 g l-1.Willey10 attributed this fluorescence increase to the presence in seawater of magnesium which where y is the peak wavelength and x is DOC concentration (mg l-1 of C). The 410 and 440 nm peaks must not be used complexes with fluorescent fulvic and humic acids, enhancing fluorescence by crosslinking the structure between internal to evaluate the organic matter content of solutions with high concentrations, to prevent overlap of the two peaks.oxygens. This crosslinking aVec fluorescence by changing the positions and energy level of p electrons. Furthermore, removal The other two peaks did not produce any displacement with changes in organic matter content. of the quenching eVect of metals such as copper or iron by magnesium could enhance fluorescence.Although fluorescence intensity was aVected by salinity, the largest changes in fluorescence intensity were observed when The eVect of salinity on emission fluorescence intensity becomes more accentuated when the pH is higher. For pH= the organic matter content of the samples was varied. The increase in natural fluorescence intensity observed by 7.0 the increase in emission fluorescence intensity due to the increase in salinity from 0 to 35 g l-1 is 3% (lem=440 nm) and Willey10 during the mixture of freshwater and saltwater in estuaries, was reproduced in this laboratory in terms of salinity, 9% when the pH is 8.5 (lem=440 nm).The results obtained show that the increase in fluorescence due to the change of adding adequate amounts of freeze dried sea salt to freshwater 252 J.Environ. Monit., 1999, 1, 251–254Fig. 5 Fluorescence intensity as a function of DOC, for salinities (Sal.) of 0, 5, 15 and 35 g l-1; pH 8.0. The eVect of dissolved organic carbon content on the emission fluorescence intensity A series of samples with salinities of 0, 5, 15 and 35 g l-1 was used to study the relationship between DOC content and fluorescence intensity (Fig. 5). For each salinity, seven solutions were prepared with diVerent organic matter content, by diluting each solution with Milli-Q water with the same salinity. The fluorescence intensity was measured at three wavelengths: 410, 440, and 460 nm (lex=360 nm). For a given salinity, the fluorescence intensity is linearly correlated with Fig. 4 Variation of emission fluorescence intensity (at pH 7.0, 8.0 and the DOC concentration. The results for all salinity values in 8.5) with salinity (lem=$, 410 nm;&, 440 nm; and +, 460 nm; lexc= this experiment fitted straight lines with correlation coeYcients 360 nm).The Raman peak of Milli-Q water was subtracted from the better than 0.997. Any of the three emission wavelengths (410, fluorescence at 410 nm. 440 and 460 nm) could be used to quantify the content of organic matter, but 440 and 460 nm give higher sensitivity ( larger slope) than 410 nm. The good correlation between fluorescence intensity and pH from 7.0 to 8.5 is remarkable for salinities greater than 2 where this increase is around 10%. DOC concentration shows that in the range of 0 to 35 g l-1 salinity there are no inner filter eVects, hence this is not the Several authors3,5,11 have not observed the increase in fluorescence intensity during the mixture of freshwater and reason for the anomalous increase in fluorescence intensity with salinity. seawater, while others12 have noted a net influence of the salinity in the range 0 to 5, which can be explained by diVerent pH changes.Conclusions Emission spectra of 21 samples with salinities ranging from 0 to 35 g l-1 and pH values of 7.0, 8.0 and 8.5 were recorded The mixing of freshwater and seawater, in laboratory studies, removes 5% to 10% of dissolved organic matter as particulate, and no shift was observed in the three wavelengths corresponding to emission maxima.This fact indicates that the increase measured as absorbance decrease.Changes in ionic strength increase fluorescence intensity for salinities ranging between 0 in fluorescence due to the salinity or change in pH is not a result of a change in the chemical structure of the fluorophores. to 5 g l-1. The good correlation between fluorescence intensity and DOC concentration shows that, in the range of 0 to Therefore, it is possible to compare spectral intensities of samples with diVerent salinities and pH values. 35 g l-1 salinity, there are no inner filter eVects, hence this is J. Environ. Monit., 1999, 1, 251–254 2533 J. E. Dorsh and T. F. Bidleman, Estuarine Coastal Shelf Sci., 1982, not the reason for the anomalous increase in fluorescence 15, 701. intensity with salinity. 4 R. F. C.Mantoura and E. M.SWoodward, Geochim. Cosmochim. The increase (%) of emission fluorescence intensity (lexc= Acta, 1983, 47, 1293. 360 nm; lem=440 nm) due to salinity is aVected by pH and is 5 P. Berger, R. W. P. M. Laane, A. G. Ilahude, M. Ewald and higher for pH=8.5 (9%) than for pH=7.0 (3%). Increased P. Courtot, Oceanolog. Acta, 1984, 7, 309. concentration of organic matter, for several salinity values, 6 P.L. Smart, B. L. Finlayson, W. T. Rylands and C.MBall,Water Res., 1976, 10, 805. caused a small but consistent shift in the emission peak 7 H. De Haan and T. De Boer, Water Res., 1987, 21, 731. wavelength at 410 nm while for the other two peaks (440 and 8 H. Okahana and M. Arita, Model FP-770 Spectrofluorometer 460 nm) no displacement was produced. product description Jasco. Jasco International Co., Ltd. (4–21, To use emission fluorescence of dissolved organic matter as Sennin-cho 2-chome, Hachioji, Tokyo 193, Japan), 1987. a tracer in estuarine or nearshore areas it is necessary to take 9 R. S. Summers, P. K. Cornel and P. V. Roberts, Sci. Total into account the influence of salinity and pH on fluorescence Environ., 1987, 62, 27. intensity. 10 J. D. Willey, Marine Chem., 1984, 15, 19. 11 J. D. Willey and L. P. Atkinson, Estuarine Coastal Shelf Sci., 1982, 14, 49. References 12 S. E. Cabaniss and M. S. Shuman, Mar. Chem., 1987, 21, 37–50. 1 E. R. Sholkovitz, Geochim. Cosmochim. Acta, 1976, 40, 831. 2 E. R. Sholkovitz and D. Copland, Geochim. Cosmochim. Acta, 1981, 45, 181. Paper 9/02529D 254 J. Environ. Monit., 1999, 1, 251–254

ISSN:0960-7919    

DOI:10.1039/a902529d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

An automatic monitor of formaldehyde in air by a monitoring tape method Nobuo Nakano*a and Kunio Nagashimab aRiken Keiki Co., Ltd., 2-7-6, Azusawa, Itabashi-ku, Tokyo 174-8477, Japan bFaculty of Engineering, Kogakuin University, 2665-1, Nakanocho Hachioji-shi, Tokyo 192-0016, Japan Received 14th January 1999, Accepted 30th March 1999 An automatic monitor has been developed for measuring formaldehyde in air using a sensitive tape for formaldehyde.It is based on the color change of the tape on reaction with formaldehyde. The porous cellulose tape, containing silica gel as an absorbent and impregnated with the processing solution containing hydroxylamine sulfate, Methyl Yellow (pH indicator; pH 2.9–4.0, red–yellow), glycerin and methanol, was found to be a highly sensitive means of detecting formaldehyde and maintains a stable sensitivity.When the tape was exposed to a sample of air containing formaldehyde, the color of the tape changed from yellow to red. The degree of color change was proportional to the concentration of formaldehyde at a constant sampling time and flow rate, and it could be recorded by measuring the intensity of reflected light (555 nm).The tape could be used to detect down to 0.08 ppm (World Health Organization standard) of formaldehyde with a sampling time of 30 min and a flow rate of 100 mL min-1. Reproducibility tests showed that the relative standard deviation of response (n=10) was 3.8% for 0.1 ppm formaldehyde. The monitor is simple, specific, capable of unattended operation and is recommended for both laboratory and field operation.The standard HCHO gas mixture was generated continu- Introduction ously by purging the diVusion tube containing paraformal- Formaldehyde (HCHO) is a carcinogenic chemical that is dehyde (Tokyo Kasei Kogyo, Tokyo, Japan) with a constant emitted from furniture and is also used in hospitals as a flow of purified air. The gas concentration was calculated from preservative. The World Health Organization (WHO) has set the flow rate and the mass loss of the paraformaldehyde.The a standard of 0.08 ppm averaged over 30 min, and the diVusion tube in the gas generating system (Gastec, Ayase, American Conference of Government Industrial Hygienists Japan; PD-1B) was kept at 30±0.1 °C in a thermostatically (ACGIH) has set a ceiling exposure value of 0.3 ppm.1 HCHO controlled water-bath.aVects residents of newly built houses or oYces, and is Humidified standard HCHO mixtures12 were prepared by considered as a major cause of sick building syndrome. The passing dry air through a Gore-Tex (porous Teflon; 4 mm id, establishment by WHO of the standard of 0.08 ppm HCHO 6 mm od and 50 mm in length) tube immersed in water in air2 has emphasized the need for a sensitive, reliable and (25±2 °C), and then purging the air into the diVusion tube specific method for the determination of HCHO in environ- holder.The relative humidity of the standard gas mixture was mental air. Various methods for the detection of HCHO have determined by a humidity sensor (Visala, Helsinki, Finland; been reported,3–7 but to achieve widespread routine use, the HMI32).method should be simple, specific, capable of unattended operation and also inexpensive. However, few methods exhibit Monitoring tape all of these desirable properties. We chose a tape monitor The porous cellulose tape containing silica gel (Whatman, because of its high sensitivity, selectivity, easy maintenance Maidstone, Kent, UK; SG-81 papers, 20 mm wide, 0.27 mm and easy operation in the automatic mode.8–10 A tape containthick and 25 m in length) was immersed in the processing ing silica gel as an absorbent and impregnated with a prosolution for 1 min, oven dried for 1–10 min at 40 °C and cessing solution containing hydroxylamine sulfate, Methyl stored in a desiccator.Yellow (pH indicator), glycerin and methanol was studied11 in order to determine HCHO concentrations of less than Apparatus 0.1 ppm in air with a shorter sampling time than 30 min.This paper describes the development of an automatic monitor for Fig. 1 shows a block diagram of the monitor (Riken Keiki, the determination of HCHO in air. Tokyo, Japan; FP-250FL, 106 mm wide, 78 mm high and 141 mm deep) and the detector is shown schematically in Experimental Reagents and samples All the chemicals used were of reagent grade quality and were employed without further purification.A processing solution was prepared as follows. In 6 mL of water, 1.0 g hydroxylamine sulfate and 0.02 g Methyl Yellow were dissolved; then 15 mL Fig. 1 Block diagram of monitor for formaldehyde. of glycerin and 79 mL of methanol were added to the solution.J. Environ. Monit., 1999, 1, 255–258 255Fig. 2. The sample gas was passed through a filter (pore size, Reflectance spectra 1 mm) to remove dust and sucked through the sampling After the tape had been exposed to 0.1 ppm HCHO for a chamber at a constant flow rate (100 mL min-1) and a consampling time of 30 min at a flow rate of 100 mL min-1, the stant sampling time (30 min).When the tape was exposed to visible reflectance spectrum of the exposed tapes was recorded HCHO, the Methyl Yellow on the tape reacted with sulfuric with a UV-2200 spectrophotometer (Shimadzu, Kyoto, Japan), acid produced by the reaction of hydroxylamine sulfate with using freshly prepared barium sulfate disk as a reference HCHO to produce a change in color.The reaction of this standard (Fig. 4). The full and broken lines show the reflec- method is represented by tance spectra of the tape exposed to 0.1 ppm of HCHO in air 2HCHO+(NH2OH)2·H2SO4�2H2C=NOH and air (without HCHO), respectively. +H2SO4+2H2O (1) Gas flow rate The color of the tape changed from yellow to red with H2SO4 liberated by this reaction. The degree of color change Table 1 shows the eVect of the sample gas flow rate on the was recorded by measuring the reflected light at 555 nm.Then response for zero gas (40% RH N2) and HCHO (40% RH). the pathway of the tape was renewed by moving the tape The response for N2 (background) increased with increasing every 30 min. The response is defined by A=-logV1/V0, sample gas flow rate, while the response for HCHO (net) where V0 and V1 are the outputs of the blank (atmospheric decreased with increasing sample gas flow rate above air) and of the sample, respectively. A period of 30 min was 300 mL min-1.In this experiment, the sample gas flow rate required to measure the responses after the tape was set in the was fixed at 100 mL min-1. The relative standard deviation tape monitor.All the measurements were carried out at was 3.8% for 0.1 ppm HCHO with a sampling time of 30 min 25±2 °C. and a flow rate of 100 mL min-1. Sampling time Results and discussion The response for a fixed concentration of HCHO was plotted We initially studied a cellulose tape without silica gel against various sampling times. Non-linear graphs between (Whatman; 1Chr) using hydroxylamine sulfate and Methyl response and sampling time were obtained in the range Yellow (pH indicator; pH 2.9–4.0, red–yellow) for the determi- 0.2–1.0 ppm and 10–30 min (Fig. 5).nation of HCHO. However, it was unsuccessful in detecting 0.1 ppm of HCHO within a sampling time of 30 min. In this experiment, we examined a porous cellulose tape containing silica gel (Whatman; SG-81).Fig. 3 shows a scanning electron microprobe photograph of the tape surface. White granules of SiO2 are scattered on the surface of the tape. As shown in Fig. 3, the granule size is between 2 and 10 mm. We concluded that the tape containing silica gel impregnated with hydroxylamine sulfate and Methyl Yellow could serve as a sensitive monitoring tape for HCHO.Fig. 2 Schematic diagram of gas detector. Fig. 4 Reflectance spectra of the tape exposed to HCHO (full line) and air (broken line) (reference, BaSO4 disk). Table 1 EVect of sample gas flow rate on response. Concentration of HCHO, 0.2 ppm; sampling time, 30 min Response Gas flow rate/ mL min-1 N2 HCHO/N2 Net 50 0.006 0.056 0.050 100 0.007 0.056 0.049 150 0.008 0.058 0.050 200 0.008 0.059 0.051 250 0.010 0.057 0.047 300 0.011 0.058 0.047 400.014 0.057 0.043 Fig. 3 Scanning electron microprobe photograph of surface 500 0.017 0.058 0.041 appearance. 256 J. Environ. Monit., 1999, 1, 255–258Table 3 EVect of temperature of sample gas on output of monitor. Concentration of HCHO, 0.2 ppm; sampling time, 30 min Temperature/°C Reading (ppm) 5 0.23 10 0.22 15 0.20 25 0.20 35 0.22 Table 4 Output of monitor for various gases Concentration of Reading Gas examined gas (v/v) (ppm) Ethanol 1% 0 Methanol 1% 0 Trichloroethylene 1% 0 Toluene 1% 0 Xylene 1% 0 Benzene 1% 0 Fig. 5 Relationship between sampling time and response at various Dichlorobenzene 1000 ppm 0 concentrations of HCHO: (a) 1.0 ppm; (b) 0.8 ppm; (c) 0.6 ppm; (d) Ethylbenzene 1% 0 0.4 ppm; (e) 0.2 ppm.Gas flow rate, 100 mL min-1. Hexane 1% 0 Carbon monoxide 100 ppm 0 Calibration graph Nitrogen monoxide 50 ppm 0 Nitrogen dioxide 105 ppm 0 Typical calibration graphs for HCHO using the optimum Sulfur dioxide 15.2 ppm 0 experimental conditions are shown in Fig. 6. By using optimum Carbon dioxide 4.9% 0 Hydrogen 100% 0 conditions, the tape could be used to detect 0.08 ppm of Acetic acid 24 ppm 0 HCHO with a sampling time of 30 min (S/N=3). Hydrogen sulfide 32 ppm 0 Reproducibility tests (n=10) showed that the relative standard Hydrogen fluoride 6.0 ppm 0 deviation of the response was 3.8% for 0.1 ppm HCHO.Hydrogen chloride 0.1 ppm 0.16 Acetone 100 ppm 0.13 Humidity of sample gas Acetaldehyde 13 ppm 0.52 Formaldehyde 0.2 ppm 0.2 Table 2 shows the eVect of the humidity of the sample gas on the response of the tape.The tape was hardly aVected by humidity in the region 0–70% RH used in this experiment at 25 °C. It can be concluded that there is no eVect of humidity Fig. 7 Continuous measurement of the sample gas using the monitor. Sampling time, 30 min. Table 5 Concentration of HCHO measured by the HCHO monitor and acetylacetone method HCHO monitor Acetylacetone method Furniture (ppm) (ppm) Fig. 6 Calibration graphs for HCHO at various sampling times: (a) A 0.04 0.06 30 min; (b) 20 min; (c) 10 min. Gas flow rate, 100mL min-1. B 0.05 0.07 C 0.15 0.11 Table 2 EVect of humidity of sample gas on output of monitor. D 1.00 (over) 1.23 Concentration of HCHO, 0.2 ppm; sampling time, 30 min Humidity (%) Reading (ppm) on the response of the tape under normal conditions (30–60% RH). 0 0.22 20 0.19 Temperature of sample gas 40 0.20 60 0.20 Table 3 shows the eVect of temperature variation of the sample 70 0.18 gas within the range 5–35 °C on the response of the tape. The J. Environ. Monit., 1999, 1, 255–258 257tape is hardly aVected by temperature in the region 5–35 °C was very suitable for the determination of HCHO in air.This monitoring tape method is simple, specific, capable of used in this experiment. It can be concluded that there is no eVect of temperature on the response of the tape under normal unattended operation and is recommended for field operation. We hope that this monitor will be used to establish better the conditions (5–35 °C). HCHO concentration in air.Selectivity The response of the tape for various gases is given in Table 4. References The tape is hardly aVected by gases in the concentration ranges used in this experiment, except for hydrogen chloride, acetone 1 ACGIH, Threshold Limit Values for Chemical Substances and Biological Exposure Indices, American Conference of Government and acetaldehyde. Industrial Hygienists, Cincinnati, OH, 1998. 2 M.Maroni, B. Seifert and T. Lindvall, Indoor Air Quality: A Continuous measurement Comprehensive Reference Book, Elsevier Press, Amsterdam, 1995, Fig. 7 shows the continuous measurement of HCHO using the p. 804. 3 F. Sawicki and T. R. Hauser, Anal. Chem., 1960, 32, 1434. monitor. The monitor showed errors of less than ±10% 4 A. C. Rayner and A. C. Jephcott, Anal.Chem., 1961, 33, 627. continuously and no noticeable lowering of the performance 5 K. Fung and D. Grosjean, Anal. Chem., 1981, 53, 168. in the test period. 6 R. H. Still, K. Wilson, and B. W. J. Lynch, Analyst, 1968, 93, 805. 7 M. E. J. Baker and R. Narayanaswamy, Analyst, 1994, 119, 959. Determination of formaldehyde emitted from furniture 8 N. Nakano, A. Yamamoto and K. Nagashima, Analyst, 1996, 12, 1939. The concentration of HCHO emitted from furniture was 9 N. Nakano, A. Yamamoto, Y. Kobayashi and K. Nagashima, measured by the monitor and by the acetylacetone method13 Talanta, 1995, 42, 641. (absorptiometric method). The results are shown in Table 5. 10 N. Nakano, M. Ishikawa, Y. Kobayashi, and K. Nagashima, The concentration of HCHO emitted from furniture obtained Anal. Sci., 1994, 10, 641. 11 N. Nakano, A. Yamamoto, T. Kawabe and K. Nagashima, by the monitor was in good agreement with that of the Nippon Kagaku Kaishi, 1998, 1998, 506. acetylacetone method. 12 T. Otagawa, S. Zaromb, and J. R. Stetter, J. Electrochem. Soc., 1985, 132, 2951. Conclusions 13 T. Nash, Biochem. J. (London), 1953, 55, 416. The automatic monitor using the sensitive tape for HCHO impregnated with hydroxylamine sulfate and Methyl Yellow Paper 9/00410F 258 J. Environ. Monit., 1999, 1, 255–258

ISSN:0960-7919    

DOI:10.1039/a900410f

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Field intercomparison of diVusive samplers for measuring ammonia M. Kirchner,a S. Braeutigam,a M. Ferm,b M. Haas,c M. Hangartner,d P. Hofschreuder,e A. Kasper-Giebl,f H. Ro�mmelt,g J. Striedner,c W. Terzer,f L. Tho� ni,h H.Werneri and R. Zimmerlingj aGSF-Forschungszentrum fu�r Umwelt und Gesundheit, Institut fu�r O� kologische Chemie, Ingolsta�dter Landstr. 1, D-85764 Neuherberg, Germany bSwedish Environmental Research Institute, P.O.Box 47086, S-40258 Gothenburg, Sweden cUmweltbundesamt, Zweigstelle Su�d, Siriusstr. 3, A-9020 Klagenfurt, Austria dEidgeno�ssische Technische Hochschule Zu�rich, Institut fu�r Hygiene und Arbeitsphysiologie, Clausiusstr. 21, CH-8092 Zu�rich, Switzerland eWageningen Agricultural University, Meteorology and Air Quality Group, Duivendaal 2, NL-6701 AP Wageningen, The Netherlands fInstitute for Analytical Chemistry, Vienna University of Technology, Getreidemarkt 9/151, A-1060 Vienna, Austria gUniversita�t Mu� nchen, Institut fu�r Balneologie und Klimatologie, Marchioninistr. 17, D-81377 Mu�nchen, Germany hForschungsstelle fu�r Umweltbeobachtung, Untere Bahnhofstr. 30, CH-8640 Rapperswil, Switzerland iUniversita�t Mu� nchen, Lehrstuhl fu�r Bioklimatologie und Immissionsforschung, Am Hochanger 11, D-85354 Freising, Germany jBundesforschungsanstalt fu�r Landwirtschaft, Institut fu�r Agraro�kologie, Bundesallee 50, D-38116 Braunschweig, Germany Received 24th March, Accepted 12th April 1999 Agricultural production systems are recognised as a major source of atmospheric ammonia.Deposition of ammonia and ammonium may contribute to undesired changes in oligotrophic ecosystems.The continuous measurement of atmospheric ammonia requires expensive and sophisticated techniques and is performed only in a very restrict number of ambient air stations in Europe. Therefore, the application of passive samplers, which have the advantage of being easy to handle and cost-eYcient, is useful.In the past the comparability of diVerent passive samplers must be considered as rather scarce. In a joint European project under the leadership of the GSF-Forschungszentrum fu� r Umwelt und Gesundheit, Neuherberg, in 1997 a comparison of diVerent passive ammonia monitoring methods was carried out in a prealpine rural site near Garmisch-Partenkirchen. It was considered valuable to include not only well established systems but also methods still being developed.For the comparative test ten working groups with diVerent methods took part. A wet annular denuder system, which has been developed by the Netherlands Energy Research Foundation for on-line measurement of atmospheric ammonia, served as reference of passive methods. The experiment, which started in June and finished in December, showed that most of the passive samplers fulfil the requirements and can be recommended for further measurements.Additional measurements of meteorological parameters were performed to check the influences of diVerent weather conditions on passive sampling. Ammonia deposition on ecosystems will result in Introduction acidification because of nitrification of the ammonium in the Ammonia emissions are high in Europe.The largest area soil7–9 and eutrofication.10 To calculate deposition and comaveraged emissions of over 6 tonne NH3 km-2 per year are pare results with critical loads,11 a typical resolution of encountered in the Netherlands and Belgium. Large areas of 1×1 km or less is needed.12 Absence of a detailed emission western France, the United Kingdom, Ireland, Denmark, the inventory and/or models to calculate concentrations and Po-valley in Italy and the eastern and southern part of deposition on this scale is a common problem.6 Measuring Germany also exhibit large emissions of NH3.1 Emissions concentrations in air is another option to determine air quality.from industry and use of fertilizer are small compared to The large number of measuring sites needed to obtain a emissions from animal husbandry.2 At a sub-national scale representative picture of ammonia concentrations in a certain area averaged emissions vary considerably.3,4 The deposition area makes passive samplers the ideal instrument to do the velocity of ammonia is large.5,6 The combination of a large job.A number of both tube-type and badge-type passive variation in emission density, emissions close to the surface samplers for measuring ammonia were developed and are and a large deposition velocity will give rise to very local summarised by CEN.concentration patterns for ammonia in ambient air. These In the present paper we describe the results of an intercompaconcentration patterns can be obtained by modelling, using rision of 10 diVusive samplers and a continuously working an emission inventory coupled to a dispersion and deposition denuder system.The measurements were carried out in southern Bavaria in 1997. model, or by measuring concentrations. J. Environ. Monit., 1999, 1, 259–265 259to distinguish: (a) Tube type: the diVusion is determined Description of the experimental procedures through a static air column.DiVusion processes can be calcu- General sampler performance criteria lated according to Fick’s first law of diVusion provided that the diVusion coeYcient is known, as in the case of ammonia. The use of passive samplers is strongly supported by the (b) Badge type: permeation processes can also be described European Union. In the Council Directive 96/62/EC of by Fick’s first law of diVusion.In this case the diVusion is 27 September 1996 on Air Quality Assessment and determined by a static layer of air and a membrane of defined Management a frame work is set for preliminary assessments pore size. The collection rate is calculated analogous to that of air quality, station siting optimisation, supporting generalisof the tube type sampler.The resistance of the membrane is ation measurements, and evaluation of existing measurements. most of the time small compared to the resistance of the In the Guidance Report on Supplementary Assessment under stagnant air layer.19 As badge type samplers are more suscep- EC Air Quality Directives (1997)13 it is concluded that the tible to factors such as formation of stagnant layers in front low cost and easy operation of the diVusive sampling techof the turbulence damping membrane and the eYciency of the niques makes it an ideal tool for large scale air pollution membrane in damping turbulence (because of the low resist- surveys with a high spatial resolution. The diVusive sampler ance against uptake of the sampler), it is advised to test the is also of particular interest as an indicative technique.sampling rate experimentally. In the past, several passive To enhance the quality and comparability of measurements sampler intercomparison campaigns have been performed, but CEN decided to standardise passive sampling. This standardisnone for ammonia.20 ation is on performance not on instruments.The future standard on passive sampling will contain four parts. Part 1 Selected site, material and methods (general requirements)14 and Part 2 (specific requirements and test methods)15 will soon be sent to the member states for In 1997, the GSF-Forschungszentrum fu� r Umwelt und inquiry. Part 3 (guide for selection, use and maintenance)16 is Gesundheit invited European researchers working on passive in preparation. The performance criteria in Part 1 require monitoring methods for air pollution to participate in an unambiguity, selectivity, an overall uncertainty less than 30% international intercomparison of ammonia samplers.21 10 for specified measuring ranges and averaging times.Overall groups decided to take part by including not only well uncertainty (OU) is a combination of precision and bias.The established systems but also methods still being developed; as value of 30% is for components not specified in EC Daughter a compromise to the CEN requirements at least 3 parallel Directives. Ammonia is a non-specified component. tube or badge type samplers were exposed in the campaign. The easiest way to test samplers is to perform tests in a Table 1 gives a brief summary of the diVerent diVusion sis should be plers. Four systems have already been described in the done to prove that the sampler meets the requirements which literature.22–25 are given in CEN (1998 b). Field tests are designed to evaluate The comparative measurements were performed at Aidling/ additional errors arising from the use of the sampler in a wider Riegsee in the district of Garmisch-Partenkirchen (Bavaria) range of environmental conditions existing in the field that are between June and December 1997.Aidling is a typical prealnot adequately covered by the laboratory tests. CEN (1998 b) pine region with agricultural activities such as pasture and requires the use of 6 parallel samplers and a single static application of liquid manure on meadows.In comparison to instrument. Consideration should be given to representa- other intensively used areas in Bavaria and Austria, the number tiveness of location (urban, rural, background), topography of cattle ha-1 near Aidling (ca. 1–1.5) is relatively small. (soil covering, degree of aVorestation), environmental conditions (temperature, relative humidity and wind speed) and Reference method likely interferences.The wet annular denuder system AMOR,26 which has been developed by the Netherlands Energy Research Foundation Theory on passive sampling (ECN) for continuous measurement of ammonia in ambient air, served as reference of the passive method. Ambient air is Integrating air monitoring methods are based on passive transport of gases from the atmosphere onto an absorbing pumped through a rotating annular denuder. Ammonia is absorbed by a weak acid solution passing the denuder in medium.17,18 There are basically two types of passive samplers Table 1 Description of diVusive methods used in the intercomparison Collection rate/ Integration Detection limit/ No.Type Inlet Collection medium ml min-1 Analytical method time/weeks mg m-3 week I Badge Membrane Impregnated filter 45 FIA 2, 4 0.8 (citric acid) II Badge Membrane Impregnated filter 45 Indophenol segment 1, 2, 4 0.3 (citric acid) flow analyser III Badge 5 mm teflon filter Stainless steel grid 77.3 Ion chromatography 1, 2, 4 0.2 (phosphoric acid) IV Ventilated sampler 5 wholes Impregnated filter 2000 Berthelot reaction 1, 4 0.05 Ø 5 mm (sulphuric acid) V Multi tube type 300 open Prepared membrane 53.8 Autoanalyser Not exposed 0.5 glass tubes (citrid acid) VI Palmes type Membrane Solution 13.4 Ion chromatography 1, 2, 4 0.6 (hydrochloric acid) VII Badge Membrane Impregnated filter 31.5 Indophenol 2, 4 0.8 (phosphoric acid) VIII Badge Teflon filter Impregn. glass surface 56 Ion chromatography 2, 4 1.0 (phosphoric acid) IX Palmes type Membrane Stainless steel grid 2.73 Conductance 2, 4 0.2 (sulfuric acid) (ECN-method) 260 J.Environ. Monit., 1999, 1, 259–265Fig. 1 Wet annular denuder system AMOR as a reference device in passive sampler intercomparison. counterflow direction. Downstream from the denuder the and yi=reference concentration of ammonia determined with the denuder.absorption solution is combined with an alkaline solution, which results in the formation of gaseous ammonia. Via a (ii) Correlation coeYcient r2 and regression coeYcients (k slope, d intercept) semi-permeable membrane, ammonia is transferred into a stream of demineralized water. The ammonium concentration For the determination of r2, k and d, the mean values obtained from 3 to 6 samplers exposed in parallel, were related in the water is determined conductometrically (Fig. 1). The calibration is made with aqueous solutions containing diVerent to the concentrations determined with the denuder. (iii) Precision. The precision of the diVerent passive sampler concentrations of ammonium. The method is very selective and independent from ambient humidity.Interferences were methods is calculated by the relative standard deviations (RSD): RSD(x)=[s(x)/x: ]×100 (%), where s(x)=standard only determined for volatile amines, which generally show concentrations much lower than ammonia. With a time reso- deviation of the results of 3–6 passive samplers exposed in parallel. lution of two minutes the measuring range is between 0.05 and 1000 mg m-3.(iv) Overall uncertainty (OU): OU={[|x: i-yi|+2s(x)]/ yi}×100, where x: i=mean concentration of ammonia obtained In order to guarantee the performance of the diVuse sampler intercomparison, a second less sophisticated denuder devel- from 3 to 6 diVusive samplers exposed in parallel and yi= reference concentration of ammonia determined with the oped by the Forschungsstelle fu� r Umweltbeobachtung (FUB), Rapperswil (Switzerland), delivered comparative data.The denuder. inside of this tubular denuder is coated with citric acid in methanol. After passing the denuder, aerosol compounds are Results and discussion collected on a filter. Extraction of the denuder and the filter, Conditions during the sampling period and the subsequent analyses by ion chromatography, are performed in the lab.The agreement between this denuder, Daily average concentrations of ammonia, determined with which has been exposed for one week periods, and the continu- the wet denuder system described above, varied between the ous flow denuder used as reference was rather good.21 limit of detection (0.05 mg m-3) and 20 mg m-3.Shorter time Regression analyses of 26 data points (weekly averages) gave averages reached up to 120 mg m-3 (30 min average). The site a linear relationship statistically significant at a 99% confi- was in close vicinity to several sources of ammonia. No marked dence. The correlation coeYcient (r2) is 0.83, the slope is 0.69 seasonal variations were visible (Fig. 2). Concentrations of and the intercept is 1.02. The annular denuder system AMOR particulate ammonium were determined with the denuder represents the x-axis. system operated by the FUB.21 Regarding weekly averages, In order to establish the influence of weather conditions on the ammonium concentrations ranged from 0.5 to 4 mg m-3; the ammonia measurements, the air temperature, relative there was no correlation between concentrations of particulate humidity, wind velocity and wind direction were registered by ammonium and ammonia.an automatic weather station. As the intercomparison started in April 1997 and lasted until December 1997 it covers late spring to early winter and Quality control thus diVerent meteorological conditions. Weekly averages of air temperature, humidity and wind velocity ranged from-0.4 Quality control included the handling of passive samplers and to 18 °C, 0.4 to 2 m s-1 and 64 to 99%, respectively.As could the statistical treatment of the data. Handling and storage of be expected, the comparison between ammonia concentrations passive samplers before and after exposure were controlled by measured by the denuder system and the meteorological GSF according to the individual requirements.21 parameters showed that low temperatures and high humidity The statistical analyses of the results obtained from the both favour low concentrations of ammonia in air.Lowest intercomparison comprises the following parameters: concentrations were determined when the ground was covered (i) Mean square error.The mean square error (MSE) with snow. describes the deviation between two measurements: Comparison between diVusion samplers and the active sampling MSE= 1 n]n i=1 bi2, where n=number of measurements (periods), system The concentrations of ammonia measured by the participating bi=x: i-yi, bi=bias, x: i=mean concentration of ammonia obtained from 3 to 6 diVusive samplers exposed in parallel groups are shown in Figs. 3–5. The results are given for 8 J. Environ. Monit., 1999, 1, 259–265 261Fig. 2 30 min average ammonia concentration measured by AMOR 6/97–12/98. Fig. 3 1 week exposure of selected passive samplers compared with an active monitor at the Aidling station. sampler types, grouped for the diVerent times of exposure (1, Mean square error 2 and 4 weeks).No results are given for method V. This The MSE calculated for the single diVusion samplers versus method was introduced too late into the investigation. the denuder method ranges from 0.1to 2.59. Minimum values Similar trends were determined by all diVusion samplers were obtained for PS I and PS III (4 week exposure) and PS and the active denuder method, but some diVerences become IX (6 samplers in parallel, 2 week exposure).These parameters visible. As expected, the time pattern of the integrated quantify the deviation of passive samplers measurements from ammonia concentrations for 2 week and monthly those obtained with the denuder as demonstrated in Figs. 3–5. measurements are not as pronounced as those of 1 week exposures. Regression analyses Tables 2–4 summarise the statistical analyses of the comparison of the single diVusion samplers with the denuder A linear relationship between the diVusion samplers and the reference denuder method, being statistically significant at the system AMOR and, in brackets, the second denuder delivered by FUB.The results are grouped for the samplers exposed for 95% level, was obtained mainly for shorter periods of exposure. Just one diVusion sampler (PS III ) meets these requirements 1, 2 and 4 weeks, respectively. 262 J. Environ. Monit., 1999, 1, 259–265Fig. 4 2 week exposure of selected passive samplers compared with an active monitor at the Aidling station. Fig. 5 4 week exposure of selected passive samplers compared with an active monitor at the Aidling station.at exposure periods of 4 weeks. This seems to be due mainly and elevated concentrations is at about 4 mg m-3. Although this trend can be seen for most of the samplers, we want to to the small number of data points available for the longer exposure periods. In most of the cases slope and intercept point out that the extent of the deviation is very diVerent for each type of sampler.were significantly diVerent from 1 or 0, respectively, at the 95% confidence level. This indicates both a proportional and a constant bias between the diVusion samplers and the denuder Relative standard deviation method. Most of the cases in which no diVerence could be obtained were cases with an extremely small number of data The RSD calculated from multiple sampling was in the range 2–49%.Regarding the single diVusion samplers, longer expo- points and a rather high overall uncertainty. Several of the diVusion samplers tend to overestimate low and to underesti- sure periods generally lead to smaller values of the RSD. RSDs below 5% were obtained for PS I, PS III, PS IV and mate high ammonia concentrations compared to the results of the active sampling method.The discrimination between low PS VI (4 weeks), PS I (2 weeks) and PS IV (1 week). Table 2 Comparison of the diVusion samplers and the reference denuder method (in brackets: FUB denuder); 1 week exposurea n bm s(b) MSEr 2 k d RSD (%) OU (%) PS II 26 (28) 0.49 (0.67) 1.31 (1.00) 1.89 (1.44) 0.45b (0.56) 0.57c (0.84) 2.11c (1.24) 15.2 75 (64) PS III 25 (27) 0.37 (0.53) 1.28 (1.08) 1.71 (1.42) 0.45b (0.52) 0.62c (0.91) 1.75c (0.84) 7.8 54 (46) PS IV 26 (28) 0.34 (0.53) 0.92 (0.62) 0.92 (0.68) 0.75b (0.78) 0.58c (0.92) 1.91c (1.20) 4.7 41 (34) PS VI 23 (25) 0.03 (0.14) 0.79 (0.71) 0.60 (0.50) 0.77b (0.78) 0.80c (1.02) 0.76c (0.05) 10.9 45 (38) an: number of measurements, bm: bias, s(b): standard deviation of bias, MSE: mean square error, r2: coeYcient of correlation, k: slope, d: intercept (mg m-3), RSD: relative standard deviation, OU: overall uncertainty.bLinear relationship statistically significant at 95% confidence level. cSlope or intercept significantly diVerent from 1 or 0 respectively at 95% confidence level. J. Environ. Monit., 1999, 1, 259–265 263Table 3 Comparison of the diVusion samplers and the reference denuder method (in brackets: FUB denuder); 2 week exposurea n bm s(b) MSEr 2 k d RSD (%) OU (%) PS I 13 0.12 (0.32) 0.72 (0.55) 0.49 (0.38) 0.74b (0.77) 0.69c (0.91) 1.32c (0.65) 4.5 25 (21) PS II 12 0.40 (0.57) 0.65 (0.60) 0.54 (0.67) 0.81b (0.77) 0.77c (0.98) 1.29c (0.64) 10.3 41 (42) PS III 12 0.13 (0.29) 0.64 (0.58) 0.39 (0.40) 0.69b (0.74) 0.87c (1.16) 0.61c (-0.25) 6.7 33 (31) PS VI 12 -0.25 (-0.03) 1.01 (0.71) 0.99 (0.47) 0.48 (0.58) 0.53c (0.76) 1.62c (0.90) 11.3 40 (36) PS VII 11 0.07 (0.30) 1.00 (0.77) 0.92 (0.64) 0.57 (0.62) 0.61c (0.86) 1.55c (0.80) 10.5 45 (43) PS VIII 12 1.36 (1.45) 0.72 (0.73) 2.33 (2.78) 0.79b (0.80) 0.92c (1.23) 1.68c (0.61) 13.1 79 (77) PS IX (3) 7 0.30 (0.73) 1.59 (1.64) 2.26 (2.85) 0.66 (0.76) 1.27 (1.81) -0.77 (-2.17) 48.9 147 (155) PS IX (6) 7 -0.16 (0.26) 0.40 (0.45) 0.16 (0.24) 0.95b (0.91) 0.93c (1.08) 0.49c (-0.05) 13.1 35 (41) an: number of measurements, bm: bias, s(b): standard deviation of bias, MSE: mean square error, r2: coeYcient of correlation, k: slope, d: intercept (mg m-3), RSD: relative standard deviation, OU: overall uncertainty.bLinear relationship statistically significant at 95% confidence level.cSlope or intercept significantly diVerent from 1 or 0 respectively at 95% confidence level. Table 4 Comparison of the diVusion samplers and the reference denuder method (in brackets: FUB denuder); 4 week exposurea n bm s(b) MSEr 2 k d RSD (%) OU (%) PS I 6 0.07 (0.18) 0.56 (0.28) 0.26 (0.10) 0.79 (0.95) 0.81c (1.13) 0.81 (-0.30) 3.1 16 (12) PS II 6 0.16 (0.44) 0.65 (0.32) 0.38 (0.28) 0.72 (0.86) 0.60c (0.94) 1.73c (0.66) 11.5 43 (39) PS III 6 0.05 (0.15) 0.36 (0.56) 0.11 (0.28) 0.87b (0.65) 0.87c (0.89) 0.54 (0.56) 4.2 18 (22) PS IV 6 0.25 (0.48) 0.80 (0.57) 0.60 (0.50) 0.45 (0.61) 0.56c (0.81) 2.09 (1.21) 1.9 22 (22) PS VI 7 -0.11 (0.08) 0.67 (0.35) 0.39 (0.11) 0.63 (0.84) 0.65c (0.94) 1.31 (0.31) 4.8 23 (18) PS VII 3 -0.71 (-0.22) 0.77 (0.81) 0.90 (0.48) 0.70 (0.41) 0.58 (0.64) 1.07 (1.13) 9.0 31 (34) PS VIII 6 0.61 (0.89) 0.94 (0.66) 1.11 (1.15) 0.53 (0.39) 0.22 (0.27) 3.67 (3.54) 17.4 77 (76) PS IX (3) 3 -1.44 (-0.95) 0.88 (0.76) 2.59 (1.30) 0.64 (0.36) 0.42 (0.45) 1.04 (1.14) 31.1 74 (67) PS IX (6) 3 -1.18 (-0.69) 0.44 (0.34) 1.52 (0.56) 0.99 (0.85) 0.68c (0.91) 0.18 (-0.34) 18.4 54 (46) an: number of measurements, bm: bias, s(b): standard deviation of bias, MSE: mean square error, r2: coeYcient of correlation, k: slope, d: intercept (mg m-3), RSD: relative standard deviation, OU: overall uncertainty. bLinear relationship statistically significant at 95% confidence level. cSlope or intercept significantly diVerent from 1 or 0 respectively at 95% confidence level.Overall uncertainty The OU ranged from 16 to 147%.Disregarding the maximum value above 100% because of the low number of comparisons, the upper limit of the overall uncertainty is 79%. An overall uncertainty below 30% (as demanded by the CEN) is obtained Table 5 Dependence of the diVerence between active and passive by PS I (2 and 4 week exposure), PS III (2 and 4 week measurements (2 week sampling) on averaged air temperature, wind velocity and relative humidity exposure), PS IV (4 week exposure) and PS VI (4 week exposure). Temperature Performance of the diVusion samplers compared to <5 °C 5–15° C >15 °C environmental conditions Bias/mg m-3 Bias/mg m-3 Bias/mg m-3 Furthermore the results from 1 and the 2 week sampling were PS I 0.32 -0.03 0.10 grouped according to the average temperature, relative OS II -0.04 0.80 0.42 humidity and wind speed determined at the site.To examine PS III -0.41 0.16 0.48 PS VI -1.50 0.11 0.23 any variations of the performance of the sampler, the average PS VII -0.78 0.62 0.50 bias was related to the average environmental conditions. PS VIII 0.87 1.57 1.66 These comparisons, which could not be performed for PS IX Wind velocity due to the delayed beginning, are given for 2 week sampling in Table 5.<1 m s-1 1–15 m s-1 >1.5 m s-1 Calculating the average bias for three temperature classes Bias/mg m-3 Bias/mg m-3 Bias/mg m-3 (<5, 5–15 and >15 °C) a temperature dependence could be observed for several diVusion samplers. At average tempera- PS I 0.23 -0.02 0.37 tures below 5 °C these samplers show a negative or a relatively PS II 0.24 0.38 0.71 PS III -0.34 0.37 0.34 small positive bias, while a larger positive bias is calculated PS VI -0.78 -0.18 0.60 for higher temperatures.Two possible explanations are given PS VII -0.25 0.00 0.89 for this phenomenon. Thus PS IV was biased by the freezing PS VIII 1.39 1.17 1.99 of the absorbent (sulfuric acid). An improvement of the anti- Relative humidity freeze reduced these problems.For PS VI the underestimation of ammonia at low temperatures can be explained by the <75% 75–85% >85% condensation and the subsequent freezing of water on the Bias/mg m-3 Bias/mg m-3 Bias/mg m-3 entrance membrane of the sampler. This leads to a blocking of the entrance opening. No explanation was given for the PS I -0.39 0.13 0.61 PS II -0.07 0.63 0.31 other diVusion samplers, which showed similar behaviour.No PS III 0.06 0.23 -0.41 uniform trend could be observed for the comparison between PS VI -0.69 0.25 -1.16 the average bias and the relative humidity as well as the wind PS VII -0.26 0.74 -0.58 velocity classes. A negative bias at wind velocities below PS VIII 1.31 1.87 0.92 1 m s-1 might point to a starvation eVect.Since slightly 264 J. Environ. Monit., 1999, 1, 259–265Symp. Den Bosch, Acid Rain Research; Do we have enough contradicting results are obtained for the 1 week and the 2 answers?, (ed. Erisman Heij) Elsevier, Amsterdam, 1995, p. 81–90. week averages, it is diYcult to derive any reliable conclusions. 4 M. A. Sutton, C. J. Place, M.Eager, D. Fowler and R. I. Smith, Due to the relative low number of observations (<25 periods) Atmos. Environ., 1995, 29(12), 1393. the statistical treatment of concentration and weather data did 5 M. A. Sutton, PhD Thesis, University of Edinburgh, 1990. not result in clear dependencies. 6 W. A. J. van Pul, C. J. M. Potma, E. P. van Leeuwen, G. P. J. Draaijers and J. W. Erisman, EDACS: European deposition maps of acidifying components on small scale: model descrip- Sampler handling tion and preliminary results, Report RIVM no 722401005, 1995.To apply a diVusion sampler in a monitoring network, 7 N. van Breemen and H. F. G. van Dijk, Environ. Pollut., 1988, installation and handling in the field as well as the mailing of 54, 249. 8 H. Ellenberg, O� kologische Vera� nderungen in Biozo�nosen durch the samplers should be as simple as possible.To fulfill all these StickstoVeintrag. Symposium ‘Ammoniak in der Umwelt’, 10. bis 12. requirements some improvements had to be made during the Oktober 1990, Bundesforschungsanszalt fu� r Landwirtschaft intercomparison. These improvements included modifications (FAL) Braunschweig-Volkenrode, 1991.of the holding device of several samplers to allow a more 9 La� nderausschuss fu� r Immissionsschutz (LAI), Bewertung von rapid and easier change or the use of air tight contain for the Ammoniak- und Ammoniumimmissionen, Bericht des Untermailing of the samplers. In the final versions of exposure and ausschusses ‘Wirkungsfragen’ Erich Schmidt Verlag, 1995. 10 J. W. Erisman, R.Bobbink and L. van der Eerden, Nitrogen handling all samplers met the above mentioned requirements. pollution on the local and regional scale: the present state of knowledge and research needs, Report RIVM no 722108010, 1996. Conclusions 11 A. Fangmeier, A. Hadwiger-Fangmeier, L. van der Eerden and H. J. Jaeger, Environ. Pollut., 1994, 86, 43. For ambient air monitoring, simple, but reliable instruments 12 J.P. Hettelingh, R. H. Gardner and L. Hordijk, Environ. Pollut., are needed. The field measurements of ammonia conducted in 1992, 77, 177. 13 R. van Aalst, L. Edwards, T. Pulles, E. de Saeger, M. Tombrou Bavaria in 1997 by the GSF-Forschungszentrum fu� r Umwelt and D. Tonnesen, Guidance report on supplementary assessment und Gesundheit demonstrated that several of the diVusion under EC Air Quality Directives, second draft, April 1997, p. 51. samplers for ammonia presently in use fulfil the CEN quality 14 CEN (1998 a) Ambient Air Quality: DiVusive samplers for the requirement and are suitable for applications in rural areas. determination of concentrations of gases and vapours; Requirements Nevertheless, the intercomparision showed that no general and test methods.Part 1: General requirements, draft report, statement can be given about the performance of all passive January 1998. 15 CEN (1998 b) Ambient Air Quality: DiVusive samplers for the samplers, even if very similar designs are used by diVerent determination of concentrations of gases and vapours; Requirements groups. On the other hand it is impossible to favour one and test methods.Part 2: Requirements and test methods, draft special design or analytical method. Furthermore, quite varireport, August 1998. able results were obtained when one sampler type was exposed 16 CEN (1998 c) Ambient Air Quality: DiVusive samplers for the for rather short (1 week) or long (4 week) time periods. determination of concentrations of gases and vapours; Requirements The application of several passive samplers tested during and test methods.Part 3: Guide for selection, use and maintanance, draft report, May 1998. the field campaign give the possibility of extensive screening 17 E. D. Palmes A. F. Gunnison, J. Di Mattio and C. Tomczyk, Am. surveys in large areas. Under certain circumstances, i.e. in lack Ind. Hyg. Assoc.J., 1976, 37, 570. of calibration, passive monitoring can provide an indication 18 R. H. Brown, Pure Appl. Chem., 1993, 65(8), 1859. about reliability of continuous monitors. In any case detailed 19 P. Hofschreuder, W. van der Meulen, P. Heeres and J. Slanina, quality assurance and control is necessary not only in the lab, J. Environ. Monit., 1999, accepted. but also in field intercomparisons. 20 M. Kirchner, Durchfu�hrung von Vergleichsversuchen zur Austestung von Passivsammlern, 1997,Wetter und Leben 49, H.4. 21 M. Kirchner, S. Braeutigam and G. Welzl, Validierung von Acknowledgements Passivsammlern zur Messung von Ammoniak im Freiland, 1998, GSF-Bericht 18/98. This work was funded by the Bavarian Ministry for State 22 A. Blatter, M. Fahrni and A. Neftel, CEC Air Pollut. Res. Development and Environmental AVairs and the European Rep. 41, 1992. Fund for Regional Development. Infrastructional support was 23 M. Ferm and H. Rodhe, J. Atmos. Chem., 1997, 27, 17. given by the Regional Government of Salzburg. One of the 24 A. Kasper and H. Puxbaum, Fresenius’ J. Anal. Chem., 1994, 350, 448. participating groups (IAC) thanks the Austrian Ministry of 25 L. De Temmerman and P. Coosemans, Ammonia and ammonium Environmental AVairs and Regional Government of Salzburg deposition on pine stands in Belgium. Proc. 14th meeting for for financial support. Spezialists in Air Pollution eVects on forest ecosystems (IUFRO p2.05): ‘Air pollution and forest decline’, Interlaken. ed. J. B. Bucher and I. Bucher-Wallin, Interlaken, Austria, 1989, vol. 1, References p. 91–96. 1 W. A. H. Asman, Nova Acta Leopold., NF70, 1994, 288, 263. 26 G. P. Wyers, R. P. Otjes and J. Slanina, Atmos. Environ. Part A, 2 E. Mattews, Global biogeochem. cycles, 1994, 8(4), 411. 1993, 27(13), 2085. 3 J. M. M. Aben, P. S. C. Heuberger, R. C. Acharya and A. L. M. Dekkers, Preliminary validation of ammonia emission data using a combination of monitoring and modelling. Proceedings Acidification Paper 9/02378J J. Environ. Monit., 1999, 1, 2

ISSN:0960-7919    

DOI:10.1039/a902378j

出版商:RSC    

年代:1999

数据来源: RSC