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Vocus Mobile Laboratory: Landfill Odor Analysis Case Study

Omar El Hajj, Abigail Koss, Veronika Pospisilova

Ambient air is a dynamic reservoir hosting a diverse array of volatile organic and inorganic compounds (VOC & VIC). Their concentrations, composition, and fluctuations across different locations and time periods, offer essential clues about their emission origins, transportation pathways, and atmospheric fate. Utilizing fast and sensitive instrumentation, mobile laboratories offer researchers and regulatory agencies the capability to directly analyze chemical emissions and their spatial distribution in the environment. These versatile features facilitate the identification and characterization of point sources, assessment of ambient concentrations, and thorough examination of real-world VOC emissions. Such data serves as vital input for air quality modeling, informs environmental policy decisions, and supports critical research in public health.

As a demonstration of the Vocus mobile lab capability, we conducted a short landfill odor analysis study to characterize emissions and monitor ambient air quality around three solid waste landfills: North Weld Landfill, Larimer County Landfill & Waste Diversion, and Front Range Landfill.

The Vocus Mobile Lab for Real-Time Mobile Monitoring

The TOFWERK Vocus CI-TOF, a real-time VOC analyzer, provides a seamless solution for the online analysis of VOCs, VICs, and odorous compounds, eliminating the need for sample preparation and slow GC separation. This, combined with its compact size, minimal power demands, robust construction, and the capability to provide high-frequency ambient air measurements, makes the Vocus CI-TOF well-suited for applications in aircraft, vehicles, and other mobile platforms.

With the deployment of a TOFWERK Vocus CI-TOF in mobile laboratory setups, researchers can gain a comprehensive understanding of the surrounding environment. This includes tracking emission sources, quantifying and profiling unique signatures and monitoring the transport of pollutants downwind, yielding a detailed environmental assessment. The system has a proven track record of deployment in mobile laboratories for mapping VOC concentrations in industrial areas and aiding regulatory bodies in source identification and addressing odor complaints in residential neighborhoods.

Landfill odor analysis
Figure 1. Exterior and interior view of the Vocus mobile laboratory.

TOFWERK has recently supplied the Colorado Department of Public Health and Environment (CDPHE) with a second Vocus mobile laboratory for the purpose of conducting local emissions and air quality monitoring. This initiative is particularly dedicated to community monitoring of air toxics and odor-producing compounds.

The Vocus mobile laboratory consists of a van (Mercedes-Benz Sprinter) customized to carry Vocus Eiger and Vocus B Aim chemical ionization mass spectrometers. The two Vocus models are benchtop-sized with a small footprint and low power consumption. The Vocus Eiger, measuring 422 x 630 x 840 mm, consumes approximately 400 watts, while the slightly larger Vocus B, at 480 x 615 x 1335 mm, requires around 600 watts. The van’s power system is outfitted with four 400AH lithium batteries, offering over 10 hours of standalone operation, and a minimum of 3 hours when the air conditioner (13.5 BTU) is in use. An additional 400W are provided by solar panels mounted on the roof to make a surplus of 1800W that could be used for inlet heaters, laptops, or additional instruments. Additionally, the van is equipped with a MaxiMet GMX500 weather station and a Picarro model G2204 CH4 and H2S analyzer.

The mobile lab is equipped with VocusMOBILE software, which collates data from the two mass spectrometers, the Picarro H2S and CH4 analyzer, and the weather station (including wind speed and direction) into a single data set. The collated dataset can then be viewed on a single screen while driving (Figure 2), which simplifies post-processing and facilitates comparisons of the data from different instruments (Figure 3). The concentrations of selected pollutants are depicted in real time on a map, facilitating identification and sources allocation. Furthermore, the data stream from VocusMOBILE is also available for integration into third-party software.

landfill odor analysis
Figure 2. A screenshot captured from VocusMOBILE, showcasing users’ capability to view data from all onboard instruments.
Landfill odor analysis
Figure 3. Time series data of methane (Picarro), toluene (Vocus Eiger), and acetic acid (Vocus B) collected from the North Weld Landfill. All data, including MaxiMet weather station data, is compiled and exported via VocusMOBILE.

Landfill Odor Analysis – Small Scale Study

Air monitoring studies face challenges when focused on landfills, as these sites emit a wide array of unusual and diverse compounds. These emissions can include aromatics, oxygen-containing compounds, sulfur-containing compounds, chlorofluorocarbons (CFCs), alongside methane. Real-time measurement of this diversity of compounds is possible only through the application of online mass spectrometric methods.

The landfill odor analysis animation below provides a visual representation of the measured concentrations of select compounds around the landfills.


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VOC profiles from North Weld Landfill, Larimer County Landfill & Waste Diversion, and Front Range Landfill.

Summary: Real-Time Mobile Monitoring Using the Vocus CI-TOF

  • Versatile and efficient solution for real-time air quality monitoring ideal for the needs of fence line monitoring or source finding.
  • High mass resolving power enables identification of individual compounds from complex industrial emissions (Figure 4).
  • Full spectrum acquisition allows measurements of a wide range of compounds simultaneously, including air toxins like BTEX and heteroatomic odorous compounds.
  • Highest sensitivity available with sub-ppt limits of detection.
  • The two Vocus models installed in the mobile lab are benchtop-sized with a small footprint and low power consumption.
  • Utilizes VocusMOBILE that facilitates data integration and visualization.
  • The Vocus B Aim rapidly and automatically switches between four different reagent ion chemistries, greatly expanding the number of chemical functional groups which can be measured (Figure 5).
Figure 4. The Vocus Eiger, with a resolving power of R = 2200, effectively separates isobaric peaks of Benzaldehyde and Xylene.
Figure 5. Monoterpenes, lactic acid, and ammonia concentrations measured by Vocus B around a dairy farm using benzene cations, iodide, and acetone as reagent ions, respectively.