Anders Feilberg

Odorant Emissions from Intensive Pig Production Measured by Online Proton-Transfer-Reaction Mass Spectrometry

Emission of odorous compounds from intensive livestock production is a cause of nuisance in populated rural areas. Knowledge on the chemical composition of odor and temporal variations in emissions are needed in order to identify factors of importance for emission rates and select proper abatement technologies. In this work, a method based on proton-transfer-reaction mass spectrometry (PTR-MS) has been developed and tested for continuous measurements of odorant emissions from intensive pig production facilities. The method is assessed to cover all presently known important odorants from this type of animal production with adequate sensitivity and a time resolution of less than one minute. The sensitivity toward hydrogen sulfide is demonstrated to exhibit a pronounced humidity dependency, which can be included in the calibration procedure in order to achieve quantitative results for this compound. Application of the method at an experimental pig facility demonstrated strong temporal variations in emissions, including diurnal variation. Based on these first results, air exchange and animal activity are suggested to be of importance for emission rates of odorants. Highest emissions are seen for hydrogen sulfide and acetic acid, whereas key odorants are evaluated from tabulated odor threshold values to be hydrogen sulfide, methanethiol, 4-methylphenol, and butanoic acid.

Occurrence and sources of particulate nitro-polycyclic aromatic hydrocarbons in ambient air in Denmark

Abstract The occurrence of selected nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) associated with atmospheric particulate matter has been investigated at an urban site and at a semi-rural site. For this purpose an analysis method based on gas chromatography and tandem ion trap mass spectrometry has been developed and applied. The nitro-PAH levels have been compared with levels of other air pollutants including unsubstituted PAHs, inorganic gases and particulate matter, as well as with meteorological parameters. Correlations and concentration ratios suggest that the dominant source of 9-nitroanthracene at the urban site is direct emissions, whereas at the semirural site its dominant source is atmospheric formation. The atmospheric formation of 2-nitrofluoranthene and 2-nitropyrene generally seems to be initiated by OH radicals during the day rather than by NO3 radicals at night. The average contribution of the OH initiated formation is estimated to be in the range of 90–100%. However, under wintertime conditions with cloudy weather implying low OH radical production, NO3 radicals may also be important as initiators of nitro-PAH formation. Samples influenced by transport of polluted air masses from the European continent have significantly elevated concentrations of atmospherically formed nitro-PAHs. The directly emitted nitro-PAHs, 1-nitropyrene and 3-nitrofluoranthene, do not exhibit elevated levels during such long-range transport episodes.

Stability of Odorants from Pig Production in Sampling Bags for Olfactometry

Odor from pig production facilities is typically measured with olfactometry, whereby odor samples are collected in sampling bags and assessed by human panelists within 30 h. In the present study, the storage stability of odorants in two types of sampling bags that are often used for olfactometry was investigated. The bags were made of Tedlar or Nalophan. In a field experiment, humid and dried air samples were collected from a pig production facility with growing-finishing pigs and analyzed with a gas chromatograph with an amperometric sulfur detector at 4, 8, 12, 28, 52, and 76 h after sampling. In a laboratory experiment, the bags were filled with a humid gas mixture containing carboxylic acids, phenols, indoles, and sulfur compounds and analyzed with proton-transfer-reaction mass spectrometry after 0, 4, 8, 12, and 24 h. The results demonstrated that the concentrations of carboxylic acids, phenols, and indoles decreased by 50 to >99% during the 24 h of storage in Tedlar and Nalophan bags. The concentration of hydrogen sulfide decreased by approximately 30% during the 24 h of storage in Nalophan bags, whereas in Tedlar bags the concentration of sulfur compounds decreased by <5%. In conclusion, the concentrations of odorants in air samples from pig production facilities significantly decrease during storage in Tedlar and Nalophan bags, and the composition changes toward a higher relative presence of sulfur compounds. This can result in underestimation of odor emissions from pig production facilities and of the effect of odor reduction technologies.

Application of proton-transfer-reaction mass spectrometry to the assessment of odorant removal in a biological air cleaner for pig production.

There is an urgent need to develop odor reduction technologies for animal production facilities, and this requires a reliable measurement technique for estimating the removal of odorants. The purpose of the present experiment was to investigate the application of proton-transfer-reaction mass spectrometry (PTR-MS) for continuous measurements at a biofilter from SKOV A/S installed at a pig production facility. PTR-MS was able to handle the harsh conditions with high humidity and dust load in a biofilter and provide reliable data for the removal of odorants, including the highly odorous sulfur compounds. The biofilter removed 80-99% of carboxylic acids, aldehydes, ketones, phenols, and indoles and ca. 75% of hydrogen sulfide. However, only ~0-15% of methanethiol and dimethyl sulfide was removed. In conclusion, PTR-MS is a promising tool that can be used to improve the development of biological air cleaning and other odor reduction technologies toward significant odorants.

Evaluation of biological air filters for livestock ventilation air by membrane inlet mass spectrometry.

Biological air filters have been proposed as a cost-effective technology for reducing odor emissions from intensive swine production facilities. In this work we present results from the application of membrane inlet mass spectrometry (MIMS) for continuously monitoring the removal of odorous compounds in biological air filters. The sensitivity and selectivity were tested on synthetic samples of selected odorous compounds, and linearity and detection limits in the lower ppb range were demonstrated for all compounds tested (methanethiol, dimethyl sulfide, carboxylic acids, 4-methylphenol, aldehydes, indole, and skatole) except trimethylamine. The method was applied in situ at two full-scale filters installed at swine houses. The results have been compared with analyses by thermal desorption gas chromatography-mass spectrometry (TD-GC/MS), and odor was measured by olfactometry. By comparison with TD-GC/MS, observed MIMS signals were assigned to 4-methylphenol, 4-ethylphenol, indole, skatole, the sum of volatile reduced organic sulfur compounds (ROS), and three subgroups of carboxylic acids. The removal rates were observed to be related to air-water partitioning with removal efficiencies in the range of 0 to 50% for low-soluble organic sulfur compounds and high removal efficiencies (typically 80-100%) for more soluble phenols and carboxylic acids. Based on the results and published odor threshold values, it is estimated that the low removal efficiency of ROS is the main limitation for achieving a higher odor reduction.

The variation of street air levels of PAH and other mutagenic PAC in relation to regulations of traffic emissions and the impact of atmospheric processes

The occurrence of particle associated PAH and other mutagenic PAC was determined in 1996 in the street air of Copenhagen. In addition, particle extracts were tested for mutagenicity. The measurements were compared with previous measurements in 1992/1993. The levels had decreased in this period. The decrease was caused by an implementation of light diesel fuels for buses and the exchange of older petrol-driven passenger cars with catalystequipped new ones. About 65% of the reduction was caused by the application of the light diesel fuels. Under special conditions, chemical processes in the atmosphere produced many more mutagens than the direct emissions. The concentrations of S-PAC and N-PAC were 10 times lower than those of PAH, while the levels of oxy-PAH were in the same order of magnitude as those of PAH. Benzanthrone, an oxy-PAH, is proposed to be formed in the atmosphere in addition to direct emissions. Benzo(a)pyrene, often applied as an air quality criteria indicator, was photochemically degraded in the atmosphere. A strong increase in the mutagenic activities was observed to coincide with a depletion of benzo(a)pyrene.

Prediction of odor from pig production based on chemical odorants.

The present work was performed to investigate the use of odorant measurements for prediction of odor concentration in facilities with growing-finishing pigs and to analyze the odorant composition in facilities with different floor and ventilation systems. Air was sampled in Nalophan bags, odor concentrations were measured by dilution-to-threshold olfactometry, and concentrations of odorants were measured by proton-transfer-reaction mass spectrometry (PTR-MS). Olfactometry and chemical analyses were synchronized to take place at identical time intervals after sampling. A principal component analysis revealed that different facilities for growing-finishing pigs can be distinguished based on the odorants. Pit ventilation comprising a small amount of the total ventilation air (10-20%) in facilities with both room and pit ventilation can be used to concentrate odorants, whereas the room ventilation contains lower concentrations of most odorants. A partial least squares regression model demonstrated that prediction of the odor concentration based on odorants measured by PTR-MS is feasible. Hydrogen sulfide, methanethiol, trimethylamine, and 4-methylphenol were identified as the compounds having the largest influence on the prediction of odor concentration, whereas carboxylic acids had no significant influence. In conclusion, chemical measurement of odorants by PTR-MS is an alternative for expressing the odor concentration in facilities with growing-finishing pigs that can be used to increase the understanding of odor from different types of facilities and improve the development of odor reduction technologies.

Real time monitoring of a biogas digester with gas chromatography, near-infrared spectroscopy, and membrane-inlet mass spectrometry.

Four methods of monitoring the anaerobic digestion process were studied at pilot scale. The methods employed were Micro Gas Chromatography (μ-GC) and Membrane Inlet Mass Spectrometry (MIMS) for measurements in the gas phase, Near Infrared Spectroscopy (NIRS) and pH in the liquid phase. Micro Gas Chromatography accurately measured H(2), CH(4), H(2)S, N(2) and O(2) in the headspace whereas the MIMS accurately measured CH(4), CO(2), H(2)S, reduced organic sulfur compounds and p-cresol, also in the headspace. In the liquid phase, NIRS was found to be suitable for estimating the concentrations of acetate, propionate and total volatile fatty acids (VFA) but the error of prediction was too large for accurate quantification. Both the μ-GC and NIRS were low maintenance methods whereas the MIMS required frequent cleaning and background measurements.

Observations of the effect of atmospheric processes on the genotoxic potency of airborne particulate matter

Abstract In this study, the relationship between genotoxic potency and the occurrence of polycyclic aromatic hydrocarbons (PAH), including benzo(a)pyrene (BaP), and nitro-PAH in urban and semi-rural air masses has been investigated. The Salmonella/microsome assay has been used as a measure of genotoxic potency. We find that the ratios of BaP/mutagenicity and PAH/mutagenicity are highly variable. The processes responsible for the variation are formation and degradation of mutagens and transport of polluted air masses from heavily industrialized regions. Air masses from Central Europe are shown to be highly enriched in mutagens as well as in PAH and nitro-PAH. However, the mutagenic activity is much more elevated than the PAH levels when these air masses are mixed with local urban air. Part of the variation in the PAH/mutagenicity ratio can be explained by photochemical transformation. Since BaP has been used in the past as an indicator of the carcinogenic risk of airborne particles, it is suggested that the cancer risk of air pollution has to be re-evaluated.

Minimisation of artefact formation of dimethyl disulphide during sampling and analysis of methanethiol in air using solid sorbent materials.

Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography-mass spectrometry method (TD-GC-MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC-MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to ≤0°C gives acceptable results. 80°C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage.