A NEW DEVICE AND METHOD FOR MEASURING VOLATILE COMPOUNDS IN MONITORING WELLS

Accurate, timely measurement of chlorinated solvents and other volatile contaminants in groundwater is crucial to support responsible environmental management. Traditionally, two distinctly different paradigms have been explored to meet this need--fixed laboratory analysis and ''real-time'' sensors. While these alternatives remain important, field based and field screening tools represent a potentially useful intermediate approach that balances some of the advantages and disadvantages of the traditional ''endmember'' paradigms. The value of accurate, in-field measurements during characterization was recognized in recent sampling/decision methods, such as the TRIAD approach (ITRC, 2003). Strategies that support gathering accurate data on the timescales representative of the rate of change of the system (e.g., months to years, not seconds to minutes) is key for long-term monitoring for chlorinated solvent plumes in which attenuation based remedies are being considered. A team of researchers developed a down-well sampling device that, when used in combination with field gas analysis tools, provides data in the field. The test results indicate this tool, as configured, will provide accurate measurements (as compared with laboratory methods) at concentrations in the hundreds of ppb or higher range, but require confirmatory traditional sampling with laboratory analysis at concentrations approaching 20 ppb and less. The logistics and costs of the sampling device were somewhat complex. The results of the study, while equivocal, generally suggest that future development of this type of in-field technique may be warranted

An in vitro investigation of microbial volatile analysis for diagnosis of wound infection

Microorganisms produce a wide range of volatile compounds as a product of metabolism. As a result of their different metabolic capabilities, the profiles of volatiles produced will differ between species. This research investigates the detection of volatile profiles from bacterial species associated with wound infection, for species discrimination when cultured under wound like conditions.This work shows that by combing the analysis of bacterial culture headspace using Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS) with multivariate statistical analysis it is possible to discriminate wound-associated bacterial species in planktonic culture, in both complex culture media and a simulated wound fluid. Furthermore, this research demonstrates the detection of volatile profiles from discarded clinical wound dressings. To advance the use of volatile analysis of wound-associated bacteria for species discrimination, a novel collagen based biofilm model providing wound-like culture conditions was developed and characterised. Use of this model for the culture of reproducible steady-state biofilms, and analysis of biofilm headspace volatile profiles was successfully undertaken and subsequently employed in combination with SIFT-MS and multivariate statistical analysis. Results show that the discrimination of wound-associated bacterial biofilms based on headspace volatile profiles under wound like conditions was feasible. In addition, SIFT-MS analysis of multispecies biofilms was undertaken and the detected headspace profiles compared to those of single species biofilms. This indicated that identification of multispecies biofilms using detection of volatile metabolites is more complex, as the headspace was dominated by volatile compounds associated with only one of the species present.The results of this research indicate that application of volatile analysis to wound diagnostics may be of use for the identification of the cause of infection, particularly within acute wounds, which are often caused by a single species

Combustive approach for measuring total volatile phosphorus content in landfill gas

A technique was developed to measure the total gaseous phosphorus content in biogas. The amount of air needed for a neutral to oxidising flame was mixed with the biogas. The gas mixture was burnt in a closed quartz burner and the combustion gasses were bubbled through a nitric acid solution. The phosphate content in the bubbling liquid was determined with sector field ICP-MS. The technique was validated in the lab with phosphine. Afterwards the set-up was installed on a landfill. The total gaseous phosphorus content in the landfill gas, measured with the combustive technique, ranged from 1.65 to 4.44 mug P/m(3). At the same time the phosphine concentration in the landfill gas was determined gas chromatographically (GC). The phosphine (PH3) content measured with GC ranged from 7.6 to 16.7 mug PH3-P/m(3). Since the phosphine-P content (GC) was consistently higher than the total gaseous phosphorus content (burner/ICP-MS), the hypothesised presence of highly toxic gaseous phosphorus compounds other than phosphine could not be demonstrated

An in vitro collagen perfusion wound biofilm model; with applications for antimicrobial studies and microbial metabolomics

BackgroundThe majority of in vitro studies of medically relevant biofilms involve the development of biofilm on an inanimate solid surface. However, infection in vivo consists of biofilm growth on, or suspended within, the semi-solid matrix of the tissue, whereby current models do not effectively simulate the nature of the in vivo environment. This paper describes development of an in vitro method for culturing wound associated microorganisms in a system that combines a semi-solid collagen gel matrix with continuous flow of simulated wound fluid. This enables culture of wound associated reproducible steady state biofilms under conditions that more closely simulate the dynamic wound environment. To demonstrate the use of this model the antimicrobial kinetics of ceftazidime, against both mature and developing Pseudomonas aeruginosa biofilms, was assessed. In addition, we have shown the potential application of this model system for investigating microbial metabolomics by employing selected ion flow tube mass spectrometry (SIFT-MS) to monitor ammonia and hydrogen cyanide production by Pseudomonas aeruginosa biofilms in real-time. ResultsThe collagen wound biofilm model facilitates growth of steady-state reproducible Pseudomonas aeruginosa biofilms under wound like conditions. A maximum biofilm density of 1010 cfu slide-1 was achieved by 30 hours of continuous culture and maintained throughout the remainder of the experiment. Treatment with ceftazidime at a clinically relevant dose resulted in a 1.2 – 1.6 log reduction in biofilm density at 72 hours compared to untreated controls. Treatment resulted in loss of complex biofilm architecture and morphological changes to bacterial cells, visualised using confocal microscopy. When monitoring the biofilms using SIFT-MS, ammonia and hydrogen cyanide levels peaked at 12 hours at 2273 ppb (±826.4) and 138 ppb (±49.1) respectively and were detectable throughout experimentation. ConclusionsThe collagen wound biofilm model has been developed to facilitate growth of reproducible biofilms under wound-like conditions. We have successfully used this method to: (1) evaluate antimicrobial efficacy and kinetics, clearly demonstrating the development of antimicrobial tolerance in biofilm cultures; (2) characterise volatile metabolite production by P. aeruginosa biofilms, demonstrating the potential use of this method in metabolomics studies

Development of membrane extraction systems for measuring trace level organic compounds in water

The presence of volatile organic compounds (VOCs) in ground and surface water resources poses a threat to public health. The measurement of these trace level contaminants in water is of significant importance. Conventional methods for analysis of trace volatile organic compounds in water include purge and trap, head space analysis, and solid phase microextraction (SPME). While these are excellent laboratory techniques, none of them can be used for continuous, on-line monitoring of water streams. Membrane separation of organic compounds from water provides an exciting possibility for on-line extraction and analysis. In previous investigations, water continuously flowed on the feed side of the membrane and the analytes were continuously removed by an inert gas stream or a vacuum. The measurement was based on steady state permeation. This approach has several limitations. For example, the steady state can not be reached instantly, resulting in a long analysis time. Another limitation is that this instrument can not be used for analyzing small discrete samples. In this study, a novel approach, referred to as pulse introduction membrane extraction (PIME), is presented. This technique eliminates steady state requirements and can be used for continuous monitoring, as well as for discrete analysis of trace levels of VOCs in water. Water samples are introduced as a pulse into a membrane module. An eluent is used to transport the sample onto the membrane. The permeated organic compounds are extracted by an inert gas, concentrated in a micro-sorbent trap and injected into a GC for analysis. An aqueous boundary layer which forms at the membrane surface due to the poor mixing of water with the membrane appears to be the major resistance to mass transfer for the permeation process. Boundary layer effects were reduced by nitrogen purge of the membrane, and by an alternative membrane module design. A mathematical model which takes into account the aqueous boundary layer effects was developed to describe the nonsteady state, pulse introduction process. A qualitative model of extraction efficiency is also presented here to illustrate the factors that affect analytical sensitivity. The combination of system optimization, nitrogen purge and improved module design results in higher sensitivity and faster response than other methods reported in the technical literature. Detection limits are at ppb levels, precision and extraction efficiency are excellent. As the result of this research, the capability of continuous monitoring of trace levels of organic compounds in water has been demonstrated. The PIME system was compared with previously reported steady state membrane permeation system. The advantages of the PIME system include higher sensitive and faster response and can also be used for discrete sample analysis. Comparison of the PIME with the purge and trap technique, which is currently the most popular method for VOCs analysis, showed that the results are in good agreement. Contaminated ground water samples from the Naval Engineering Research Station were analyzed to demonstrate the practicality of the PIME system. This study was extended to the analysis of sernivolatile organic compounds (SVOCs) in water. Continuous monitoring of SVOCs in water using membrane extraction and on-line HPLC analysis was explored. The system was based on continuous extraction rather than pulse introduction. It demonstrated the capability for enriclunent of SVOCs from water into a solvent. Continuous monitoring of SVOCs was demonstrated at ppb level using HPLC. System parameters which affect the enrichment factors were studied

Arsenic contamination in groundwater : some analytical considerations

For countries such as Bangladesh with a significant groundwater arsenic problem, there is an urgent need for the arsenic-contaminated wells to be identified as soon as possible and for appropriate action to be taken. This will involve the testing of a large number of wells, potentially up to 11 million in Bangladesh alone. Field-test kits offer the only practical way forward in the timescale required. The classic field method for detecting arsenic (the ‘Gutzeit’ method) is based on the reaction of arsine gas with mercuric bromide and remains the best practical approach. It can in principle achieve a detection limit of about 10 μg l−1 by visual comparison of the coloured stain against a colour calibration chart. A more objective result can be achieved when the colour is measured by an electronic instrument. Attention has to be paid to interferences mainly from hydrogen sulfide. Due to analytical errors, both from the field-test kits and from laboratory analysis, some misclassification of wells is inevitable, even under ideal conditions. The extent of misclassification depends on the magnitude of the errors of analysis and the frequency distribution of arsenic observed, but is in principle predictable before an extensive survey is undertaken. For a country with an arsenic distribution similar to that of Bangladesh, providing care is taken to avoid sources of bias during testing, modern field-test kits should be able to reduce this misclassification to under 5% overall

Perspectives for synergic blends of attractive sources in south american palm weevil mass trapping: Waiting for the red palm weevil Brazil invasion

Coupling several natural and synthetic lures with aggregation pheromones from the palm weevils Rhynchophorus palmarum and R. ferrugineus reveals a synergy that results in an increase in pest captures. The combined attraction of pure pheromones, ethyl acetate, and decaying sweet and starchy plant tissue increases the net total of mass-trapped weevils. The 2018 entrance of the red palm weevil (RPW) into South America has threatened palm-product income in Brazil and other neighboring countries. The presence of the new A1 quarantine pest necessitates the review of all available options for a sustainable mass-trapping, monitoring, and control strategy to ultimately target both weevils with the same device. The effective lure-blend set for the mass-trapping system will attract weevils in baiting and contaminating stations for entomopathogenic fungi that the same weevils will spread

Air pollution monitoring instrumentation A survey

Air pollution monitoring instrumentation developed for aerospace uses surveyed for industrial application

Distributed environmental monitoring

With increasingly ubiquitous use of web-based technologies in society today, autonomous sensor networks represent the future in large-scale information acquisition for applications ranging from environmental monitoring to in vivo sensing. This chapter presents a range of on-going projects with an emphasis on environmental sensing; relevant literature pertaining to sensor networks is reviewed, validated sensing applications are described and the contribution of high-resolution temporal data to better decision-making is discussed