Air sampling and analysis method for volatile organic compounds (VOCs) related to field-scale mortality composting operations

A critical review on characterization, human health risk assessment and mitigation of malodorous gaseous emission during the composting process

Composting has emerged as a suitable method to convert or transform organic waste including manure, green waste, and food waste into valuable products with several advantages, such as high efficiency, cost feasibility, and being environmentally friendly. However, volatile organic compounds (VOCs), mainly malodorous gases, are the major concern and challenges to overcome in facilitating composting. Ammonia (NH3) and volatile sulfur compounds (VSCs), including hydrogen sulfide (H2S), and methyl mercaptan (CH4S), primarily contributed to the malodorous gases emission during the entire composting process due to their low olfactory threshold. These compounds are mainly emitted at the thermophilic phase, accounting for over 70% of total gas emissions during the whole process, whereas methane (CH4) and nitrous oxide (N2O) are commonly detected during the mesophilic and cooling phases. Therefore, the human health risk assessment of malodorous gases using various indexes such as ECi (maximum exposure concentration for an individual volatile compound EC), HR (non-carcinogenic risk), and CR (carcinogenic risk) has been evaluated and discussed. Also, several strategies such as maintaining optimal operating conditions, and adding bulking agents and additives (e.g., biochar and zeolite) to reduce malodorous emissions have been pointed out and highlighted. Biochar has specific adsorption properties such as high surface area and high porosity and contains various functional groups that can adsorb up to 60%-70% of malodorous gases emitted from composting. Notably, biofiltration emerged as a resilient and cost-effective technique, achieving up to 90% reduction in malodorous gases at the end-of-pipe. This study offers a comprehensive insight into the characterization of malodorous emissions during composting. Additionally, it emphasizes the need to address these issues on a larger scale and provides a promising outlook for future research.

Putative volatile biomarkers of bovine tuberculosis infection in breath, skin and feces of cattle

Bovine tuberculosis (bTB) is an infectious disease with significant impact on animal health, public health and international trade. Standard bTB screening in live cattle consists in injecting tuberculin and measuring the swelling at the place of injection few days later. This procedure is expensive, time-consuming, logistically challenging, and is not conclusive before performing confirmatory tests and additional analysis. The analysis of the volatile organic compounds (VOCs) emitted by non-invasive biological samples can provide an alternative diagnostic approach suitable for bTB screening. In the present study, we analyzed VOC samples emitted through the breath, feces and skin of 18 cows diagnosed with bTB from three farms from Romania, as well as of 27 negative cows for bTB from the same farms. Analytical studies employing gas chromatography coupled to mass spectrometry revealed 80 VOCs emitted through the breath, 200 VOCs released by feces, and 80 VOCs emitted through the skin. Statistical analysis of these compounds allowed the identification of 3 tentative breath VOC biomarkers (acetone; 4-methyldecane; D-limonene), 9 tentative feces VOC biomarkers (toluene; [(1,1-dimethylethyl)thio]acetic acid; alpha-thujene; camphene; phenol; o-cymene; 3-(1,1-dimethylethyl)-2,2,4,4-tetramethyl-3-pentanol; 2,5-dimethylhexane-2,5-dihydroperoxide; 2,4-di-tert-butylphenol), and 3 tentative skin VOC biomarkers (ammonia; 1-methoxy-2-propanol; toluene). The possible pathway of these volatile biomarkers is discussed.

Testing the plastic-wrapped composting system to dispose of swine mortalities during an animal disease outbreak

Composting has been used to dispose of animal mortalities and infected materials, such as manure and feed, during major animal disease outbreaks. In this study, we adapted the plastic-wrapped mortality composting system developed by the Canadian Food Inspection Agency during the 2004 highly pathogenic avian influenza outbreak to compost swine mortalities. The goals of the study were to evaluate the performance of the plastic-wrapped composting system to dispose of swine mortalities and to field test its ability to eliminate the spread of airborne pathogens through the aeration ducts. Two cover materials, ground cornstalks and woodchips, were tested using passively and actively aerated composting sheds. The mortalities were inoculated with Salmonella spp. and vaccine strains of Bovine herpesvirus-1 and Bovine viral diarrhea virus. Air samples collected from the upper aeration duct (air outlet) during the first 10 d of composting were negative for Salmonella and the viruses tested, which indicated that aerosol transmission of the pathogens was limited. The aeration plenum placed under the mortalities helped to keep conditions aerobic, as O₂ concentrations of both passively and actively aerated test units were above 11%. Actively aerated cornstalks had the highest degree-hours (1,462 °C h d^-1 ), which was followed by passively aerated cornstalks (1,312 °C h d^-1 ), actively aerated woodchips (1,303 °C h d^-1 ), and passively aerated woodchips (1,062 °C h d^-1 ). After a 7-wk composting period, all three pathogens were inactivated based on quantitative polymerase chain reaction test results. The mortalities were not inoculated with the African swine fever virus, but temperature data showed that if they were, the system had the potential to eliminate this virus.

Physical and chemical indicators of transformations of poultry carcass parts and broiler litter during short term thermophilic composting

Short-term on-site composting of poultry carcasses and broiler litter (BL) is considered as a feasible technology for pathogen elimination during events of mass mortality in poultry houses. However, factors related to mass losses and physical transformation of the poultry carcass, and associated emissions of volatile organic compounds (VOCs) and odors, have not been thoroughly evaluated. This study aims to characterize the degradation of separated carcass parts co-composted with BL and the associated air emissions during 30 days of enclosed composting at 50 °C with constant aeration. The study was carried out in lab-scale simulators using five mixtures containing feathers, rib bones, skins, breast muscles, and hearts and livers, prepared at a 1:2 volumetric ratio (carcass:BL). Dry mass losses reached 59.5, 41.1, 60.8 and 103.5% (based on weight) or 48.4, 29.6, 49.7, and 94.8% (based on CO₂-C and NH₃-N emissions), for rib bones, skins, breast muscles, and hearts and livers, respectively. Visually, most of the carcass parts were degraded, and the typical carcass odor had disappeared by the end of the 30 days. Out of 24 VOCs, dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) contributed 80.7-88.3% of the total VOC flux, considering the partial contribution of each part to the emissions involved with the whole carcass. DMDS, DMTS, benzaldehyde, methanethiol, pentanoic acid, and NH₃, contributed 90.5-97.9% of the odor activity values during composting. DMDS/DMTS ratio is suggested as a potential biomarker of stabilization and readiness of the compost for transportation toward further treatment or safe burial.

A review of the animal disease outbreaks and biosecure animal mortality composting systems

Despite the development of new vaccines and the application of rigorous biosecurity measures, animal diseases pose a continuing threat to animal health, food safety, national economy, and the environment. Intense livestock production, increased travel, and changing climate have increased the risk of catastrophic animal losses due to infectious diseases. In the event of an outbreak, it is essential to properly manage the infected animals to prevent the spread of diseases. The most common disposal methods used during a disease outbreak include burial, landfilling, incineration and composting. Biosecurity, transportation logistics, public perception, and environmental concerns limit the use of some of these methods. During a disease outbreak, the large number of mortalities often exceeds the capacity of local rendering plants and landfills. Transporting mortalities to disposal and incineration facilities outside the production operation introduces biosecurity risks. Burying mortalities is limited by the size and availability of suitable sites and it has the risk of pathogen survival and contamination of groundwater and soil. Portable incinerators are expensive and have the potential to aerosolize infectious particles. Composting, on the other hand, has been recognized as a biosecure disposal method. Research showed that it eliminates bacterial pathogens such as Escherichia coli O157: H7, Salmonella spp., as well as viruses including highly pathogenic avian influenza, foot-and-mouth disease, Newcastle disease, and porcine epidemic diarrhea. This paper summarizes the lessons learned during the major animal disease outbreaks including the 2010 foot-and-mouth disease, 2016 highly pathogenic avian influenza, and recent African swine fever outbreaks. The purpose of this review is to critically discuss the biosecurity of composting as a mortality disposal method during the outbreaks of infectious animal diseases.

The Spatial and Temporal Distribution of Process Gases within the Biowaste Compost

Composting is generally accepted as the sustainable recycling of biowaste into a useful and beneficial product for soil. However, composting processes can produce gases that are considered air pollutants. In this dataset, we summarized the spatial and temporal distribution of process gases (including rarely reported carbon monoxide, CO) generated inside full-scale composting piles. In total 1375 cross-sections were made and presented in 230 figures. The research aimed to investigate the phenomenon of gas evolution during the composting of biowaste depending on the pile turning regime (no turning, turning once a week, and turning twice a week) and pile location (outdoors, and indoors in a composting hall). The analyzed biowaste (a mixture of tree leaves and branches, grass clippings, and sewage sludge) were composted in six piles with passive aeration including additional turning at a municipal composting plant. The chemical composition and temperature of process gases within each pile were analyzed weekly for ~49–56 days. The variations in the degree of pile aeration (O2 content), temperature, and the spatial distribution of CO, CO2 and NO concentration during the subsequent measurement cycles were summarized and visualized. The lowest O2 concentrations were associated with the central (core) part of the pile. Similarly, an increase in CO content in the pile core sections was found, which may indicate that CO is oxidized in the upper layer of composting piles. Higher CO and CO2 concentrations and temperature were also observed in the summer season, especially on the south side of piles located outdoors. The most varied results were for the NO concentrations that occurred in all conditions. The dataset was used by the composting plant operator for more sustainable management. Specifically, the dataset allowed us to make recommendations to minimize the environmental impact of composting operations and to lower the risk of worker exposure to CO. The new procedure is as follows: turning of biowaste twice a week for the first two weeks, followed by turning once a week for the next two weeks. Turning is not necessary after four weeks of the process. The recommended surface-to-volume ratio of a compost pile should not exceed 2.5. Compost piles should be constructed with a surface-to-volume ratio of less than 2 in autumn and early spring when low ambient temperatures are common.

Lab-scale evaluation of aerated burial concept for treatment and emergency disposal of infectious animal carcasses

Nearly 55,000 outbreaks of animal disease were reported to the World Animal Health Information Database between 2005 and 2016. To suppress the spread of disease, large numbers of animal mortalities often must be disposed of quickly and are frequently buried on the farm where they were raised. While this method of emergency disposal is fast and relatively inexpensive, it also can have undesirable and lasting impacts (slow decay, concerns about groundwater contamination, pathogens re-emergence, and odor). Following the 2010 foot-and-mouth disease outbreak, the Republic of Korea's National Institute of Animal Science funded research on selected burial alternatives or modifications believed to have potential to reduce undesirable impacts of burial. One such modification involves the injection of air into the liquid degradation products from the 60-70% water from decomposing carcasses in lined burial trenches. Prior to prototype development in the field, a laboratory-scale study of aerated decomposition (AeD) of poultry carcasses was conducted to quantify improvements in time of carcass decomposition, reduction of potential groundwater pollutants in the liquid products of decomposition (since trench liners may ultimately leak), and reduction of odorous VOCs emitted during decomposition. Headspace gases also were monitored to determine the potential for using gaseous biomarkers in the aerated burial trench exhaust stream to monitor completion of the decomposition. Results of the lab-scale experiments show that the mass of chicken carcasses was reduced by 95.0 ± 0.9% within 3 months at mesophilic temperatures (vs. negligible reduction via mesophilic anaerobic digestion typical of trench burial) with concomitant reduction of biochemical oxygen demand (BOD; 99%), volatile suspended solids (VSS; 99%), total suspended solids (TSS; 99%), and total ammonia nitrogen (TAN; 98%) in the liquid digestate. At week #7 BOD and TSS in digestate met the U.S. EPA standards for treated wastewater discharge to surface water. Salmonella and Staphylococcus were inactivated by the AeD process after week #1 and #3, respectively. Five gaseous biomarkers: pyrimidine; p-cresol; phenol; dimethyl disulfide; and dimethyl trisulfide; were identified and correlated with digestate quality. Phenol was the best predictor of TAN (R = 0.96), BOD (R = 0.92), and dissolved oxygen (DO) (R = -0.91). Phenol was also the best predictor populations of Salmonella (R = 0.95) and aerobes (R = 0.88). P-cresol was the best predictor for anaerobes (R = 0.88). The off-gas from AeD will require biofiltration or other odor control measures for a much shorter time than anaerobic decomposition. The lab-scale studies indicate that AeD burial has the potential to make burial a faster, safer, and more environmentally friendly method for emergency disposal and treatment of infectious animal carcasses and that this method should be further developed via prototype-scale field studies.

Method for sampling and analysis of volatile biomarkers in process gas from aerobic digestion of poultry carcasses using time-weighted average SPME and GC-MS

A passive sampling method, using retracted solid-phase microextraction (SPME) - gas chromatography-mass spectrometry and time-weighted averaging, was developed and validated for tracking marker volatile organic compounds (VOCs) emitted during aerobic digestion of biohazardous animal tissue. The retracted SPME configuration protects the fragile fiber from buffeting by the process gas stream, and it requires less equipment and is potentially more biosecure than conventional active sampling methods. VOC concentrations predicted via a model based on Fick's first law of diffusion were within 6.6-12.3% of experimentally controlled values after accounting for VOC adsorption to the SPME fiber housing. Method detection limits for five marker VOCs ranged from 0.70 to 8.44ppbv and were statistically equivalent (p>0.05) to those for active sorbent-tube-based sampling. The sampling time of 30min and fiber retraction of 5mm were found to be optimal for the tissue digestion process.

Effect of Substrate on Identification of Microbial Communities in Poultry Carcass Composting and Microorganisms Associated with Poultry Carcass Decomposition

Three composting systems, which consisted of different ratios of chicken manure, sawdust, and poultry carcasses, were used to investigate the effect of substrate on the identification of microbial communities and microorganisms associated with poultry carcass decomposition by characterizing the microbial communities and physicochemical parameters. The physicochemical and Miseq Illumina sequencing results showed the composition of substrate had a significant effect on the identification and metabolic capabilities of microbial communities in decomposting process. Poultry carcasses might be the potential driver for the identification of bacterial communities in poultry carcass composting, whereas the initial C/N ratio may mainly contribute to the diversity of fungal communities and the similar dominant microbial communities in treatments. Poultry carcasses and initial C/N ratio could respectively affect the composition and abundance of microorganisms associated with the decomposition of poultry carcasses. Understanding the potential composting driver could allow development of an efficient carcass degradation system.

Performance of a plastic-wrapped composting system for biosecure emergency disposal of disease-related swine mortalities

A passively-ventilated plastic-wrapped composting system initially developed for biosecure disposal of poultry mortalities caused by avian influenza was adapted and tested to assess its potential as an emergency disposal option for disease-related swine mortalities. Fresh air was supplied through perforated plastic tubing routed through the base of the compost pile. The combined air inlet and top vent area is ⩽∼1% of the gas exchange surface of a conventional uncovered windrow. Parameters evaluated included: (1) spatial and temporal variations in matrix moisture content (m.c.), leachate production, and matrix O2 concentrations; (2) extent of soft tissue decomposition; and (3) internal temperature and the success rate in achieving USEPA time/temperature (T) criteria for pathogen reduction. Six envelope materials (wood shavings, corn silage, ground cornstalks, ground oat straw, ground soybean straw, or ground alfalfa hay) and two initial m.c.'s (15-30% w.b. for materials stored indoors, and 45-65% w.b. to simulate materials exposed to precipitation) were tested to determine their effect on performance parameters (1-3). Results of triple-replicated field trials showed that the composting system did not accumulate moisture despite the 150kg carcass water load (65% of 225kg total carcass mass) released during decomposition. Mean compost m.c. in the carcass layer declined by ∼7 percentage points during 8-week trials, and a leachate accumulation was rare. Matrix O2 concentrations for all materials other than silage were ⩾10% using the equivalent of 2m inlet/vent spacing. In silage O2 dropped below 5% in some cases even when 0.5m inlet/vent spacing was used. Eight week soft tissue decomposition ranged from 87% in cornstalks to 72% in silage. Success rates for achievement of USEPA Class B time/temperature criteria ranged from 91% for silage to 33-57% for other materials. Companion laboratory biodegradation studies suggest that Class B success rates can be improved by slightly increasing envelope material m.c. Moistening initially dry (15% m.c.) envelope materials to 35% m.c. nearly doubled their heat production potential, boosting it to levels ⩾silage. The 'contradictory' silage test results showing high temperatures paired with slow soft tissue degradation are likely due to this material's high density, low gas permeability and low water vapor loss. While slow decomposition typically suggests low microbial activity and heat production, it does not rule out high internal temperatures if the heat produced is conserved. Occasional short-term odor releases during the first 2weeks of composting were associated with top-to-bottom gas flow which is contrary to the typical bottom-to-top flow typically observed in conventional compost piles. In cases where biosecurity concerns are paramount, results of this study show the plastic-wrapped passively-ventilated composting method to have good potential for above-ground swine mortality disposal.

Volatile organic compounds at swine facilities: a critical review

Volatile organic compounds (VOCs) are regulated aerial pollutants that have environmental and health concerns. Swine operations produce and emit a complex mixture of VOCs with a wide range of molecular weights and a variety of physicochemical properties. Significant progress has been made in this area since the first experiment on VOCs at a swine facility in the early 1960s. A total of 47 research institutions in 15 North American, European, and Asian countries contributed to an increasing number of scientific publications. Nearly half of the research papers were published by U.S. institutions. Investigated major VOC sources included air inside swine barns, in headspaces of manure storages and composts, in open atmosphere above swine wastewater, and surrounding swine farms. They also included liquid swine manure and wastewater, and dusts inside and outside swine barns. Most of the sample analyses have been focusing on identification of VOC compounds and their relationship with odors. More than 500 VOCs have been identified. About 60% and 10% of the studies contributed to the quantification of VOC concentrations and emissions, respectively. The largest numbers of VOC compounds with reported concentrations in a single experimental study were 82 in air, 36 in manure, and 34 in dust samples. The relatively abundant VOC compounds that were quantified in at least two independent studies included acetic acid, butanoic acid (butyric acid), dimethyl disulfide, dimethyl sulfide, iso-valeric, p-cresol, propionic acid, skatole, trimethyl amine, and valeric acid in air. They included acetic acid, p-cresol, iso-butyric acid, butyric acid, indole, phenol, propionic acid, iso-valeric acid, and skatole in manure. In dust samples, they were acetic acid, propionic acid, butyric acid, valeric acid, p-cresol, hexanal, and decanal. Swine facility VOCs were preferentially bound to smaller-size dusts. Identification and quantification of VOCs were restricted by using instruments based on gas Chromatography (GC) and liquid chromatography (LC) with different detectors most of which require time-consuming procedures to obtain results. Various methodologies and technologies in sampling, sample preparation, and sample analysis have been used. Only four publications reported using GC based analyzers and PTR-MS (proton-transfer-reaction mass spectrometry) that allowed continuous VOC measurement. Because of this, the majority of experimental studies were only performed on limited numbers of air, manure, or dust samples. Many aerial VOCs had concentrations that were too low to be identified by the GC peaks. Although VOCs emitted from swine facilities have environmental concerns, only a few studies investigated VOC emission rates, which ranged from 3.0 to 176.5mgd(-1)kg(-1) pig at swine finishing barns and from 2.3 to 45.2gd(-1)m(-2) at manure storages. Similar to the other pollutants, spatial and temporal variations of aerial VOC concentrations and emissions existed and were significantly affected by manure management systems, barn structural designs, and ventilation rates. Scientific research in this area has been mainly driven by odor nuisance, instead of environment or health concerns. Compared with other aerial pollutants in animal agriculture, the current scientific knowledge about VOCs at swine facilities is still very limited and far from sufficient to develop reliable emission factors.

Considerations on the application of miniaturized sample preparation approaches for the analysis of organic compounds in environmental matrices

The miniaturization and improvement of sample preparation is a challenge that has been fulfilled up to a point in many fields of analytical chemistry. Particularly, the hyphenation of microextraction with advanced analytical techniques has allowed the monitoring of target analytes in a vast variety of environmental samples. Several benefits can be obtained when miniaturized techniques such as solid-phase microextraction (SPME) or liquid-phase microextraction (LPME) are applied, specifically, their easiness, rapidity and capability to separate and pre-concentrate target analytes with a negligible consumption of organic solvents. In spite of the great acceptance that these green sample preparation techniques have in environmental research, their full implementation has not been achieved or even attempted in some relevant environmental matrices. In this work, a critical review of the applications of LPME and SPME techniques to isolate and pre-concentrate traces of organic pollutants is provided. In addition, the influence of the environmental matrix on the effectiveness of LPME and SPME for isolating the target organic pollutants is addressed. Finally, unsolved issues that may hinder the application of these techniques for the extraction of dissolved organic matter from environmental samples and some suggestions for developing novel and less selective enrichment and isolation procedures for natural organic matter on the basis of SPME and LPME are included.

Harmful and beneficial effects of organic monosulfides, disulfides, and polysulfides in animals and humans

Many organic sulfides (mono-, di-, and polysulfides) are present in our environment. Simple derivatives are produced by some plants and animals, while complex sulfides are secondary metabolites of several genera of bacteria and fungi. Sulfides play an important role in the smell and taste of food, and many such compounds are used as food flavorings. Some sulfides are toxic, and there is evidence that such toxicity is caused by the ability of these substances to generate reactive oxygen species. Some sulfides, however, have been shown to protect against toxicants and carcinogens. These beneficial effects are believed to involve, at least in part, the ability of sulfides to inhibit the enzymatic activation of pro-toxicants and to increase tissue activities of enzymes that protect against electrophiles. Some sulfides also have potential as cancer chemotherapeutics. In this review, the toxic and beneficial effects of sulfides in animals are described, and the possible value of sulfides in cancer chemoprotection and cancer chemotherapy is discussed.

Air sampling methods for VOCs related to field-scale biosecure swine mortality composting

Monitoring specific volatile organic compounds (VOCs) as markers of biosecure carcass degradation is a promising method to test progress and completion of the composting process. The objective of this study was to test the feasibility of using existing aeration ducts in composting units as practical sampling locations. The secondary objective was to test the feasibility of using marker VOC concentrations in aeration ducts to elucidate information about airflow patterns inside composting units. Marker VOC concentrations were significantly higher in the upper aeration duct and this duct can typically be used to collect air samples instead of placing special air sampling probes inside the composting units. Occasionally, the airflow direction inside composting units can change. Marker VOC concentrations can be used to decide the airflow direction inside the composting units. In this study, higher VOC concentrations were measured from the upper aeration duct, and this duct was shown to be an outlet.

GC-MS and GC-NPD Determination of Formaldehyde Dimethylhydrazone in Water Using SPME

Formaldehyde dimethylhydrazone (FADMH) is one of the important transformation products of residual rocket fuel 1,1-dimethylhydrazine (1,1-DMH). Thus, recent studies show that FADMH toxicity is comparable to that of undecomposed 1,1-DMH. In this study, a new method for quantification of FADMH in water based on solid phase microextraction (SPME) in combination with gas chromatography (GC) with mass spectrometric (MS) and nitrogen-phosphorus detection (NPD) is presented. Effects of SPME fiber coating type, extraction and desorption temperatures, extraction time, and pH on analyte recovery were studied. The optimized method used 65 micron polydimethylsiloxane/divinylbenzene fiber coating for 1 min headspace extractions at 30 °C. Preferred pH and desorption temperature from the SPME fiber are >8.5 and 200 °C, respectively. Detection limits were estimated to be 1.5 and 0.5 μg L⁻¹ for MS and NPD, respectively. The method was applied to laboratory-scale experiments to quantify FADMH. Results indicate applicability for in situ sampling and analysis and possible first-time detection of free FADMH in water.

Field scale evaluation of volatile organic compound production inside biosecure swine mortality composts

Emergency mortality composting associated with a disease outbreak has special requirements to reduce the risks of pathogen survival and disease transmission. The most important requirements are to cover mortalities with biosecure barriers and avoid turning compost piles until the pathogens are inactivated. Temperature is the most commonly used parameter for assessing success of a biosecure composting process, but a decline in compost core temperature does not necessarily signify completion of the degradation process. In this study, gas concentrations of volatile organic compounds (VOCs) produced inside biosecure swine mortality composting units filled with six different cover/plant materials were monitored to test the state and completion of the process. Among the 55 compounds identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the process. Temperature at the end of eight weeks was not found as an indicator of swine carcass degradation. However, gas concentrations of the marker compounds at the end of eight weeks were found to be related to carcass degradation. The highest gas concentrations of the marker compounds were measured for the test units with the lowest degradation (highest respiration rates). Dimethyl disulfide was found to be the most robust marker compound as it was detected from all composting units in the eighth week of the trial. Concentration of dimethyl disulfide decreased from a range of 290-4340 ppmv to 6-160 ppbv. Dimethyl trisulfide concentrations decreased to a range of below detection limit to 430 ppbv while pyrimidine concentrations decreased to a range of below detection limit to 13 ppbv.

Screening of transformation products in soils contaminated with unsymmetrical dimethylhydrazine using headspace SPME and GC-MS

The paper describes a novel SPME-based approach for sampling and analysis of transformation products of highly reactive and toxic unsymmetrical dimethylhydrazine (UDMH) which is used as a fuel in many Russian, European, Indian, and Chinese heavy cargo carrier rockets. The effects of several parameters were studied to optimize analyte recovery. It was found that the 85 microm Carboxen/polydimethylsiloxane fiber coating provides the highest selectivity for selected UDMH transformation products. Optimal sampling/sample preparation parameters were determined to be 1-h soil headspace sampling time at 40 degrees C. The GC inlet temperature was optimized to 170 degrees C held for 0.1 min, then 1 degrees C s(-1) ramp to 250 degrees C where it was held for 40 min. Temperature programming resulted in a fast desorption along with minimal chemical transformation in the GC inlet. SPME was very effective extracting UDMH transformation products from soil samples contaminated with rocket fuel. The use of SPME resulted in high sensitivity, speed, small labor consumption due to an automation and simplicity of use. It was shown that water addition to soil leads to a significant decrease of recovery of almost all target transformation products of UDMH. The use of SPME for sampling and sample preparation resulted in detection of the total of 21 new compounds that are relevant to the UDMH transformation in soils. In addition, the number of confirmed transformation products of UDMH increased from 15 to 27. This sampling/sample preparation approach can be recommended for environmental assessment of soil samples from areas affected by space rocket activity.