Industrial odor pollution remains one of the most challenging environmental issues to address. Unlike visible emissions or easily quantifiable pollutants, odors are transient, spatially variable, and often escape detection by conventional fixed-site monitoring stations. A new study published in Atmospheric Environment demonstrates how mobile monitoring technology can transform our understanding of industrial odor emissions, and points toward more effective regulatory strategies.
The Challenge: Persistent Odor Complaints Despite Low VOC Levels
The Tuoketuo Industrial Park in Hohhot, Inner Mongolia, hosts a dense cluster of biopharmaceutical, coal-chemical, and food processing facilities. Despite reporting relatively low total volatile organic compound (TVOC) concentrations, the region has experienced a 15% year-on-year increase in odor complaints. This disconnect between measured pollutant levels and community experience highlights a fundamental limitation of mass-based air quality metrics.
Our research team, including collaborators from Zhigan Technology, Northeast Agricultural University, RISE Research Institutes of Sweden, and the Ministry of Agriculture’s Agro-Environmental Protection Institute, conducted a 15-month mobile monitoring campaign to investigate this paradox.
Mobile Monitoring: A Game-Changer for Odor Assessment
Between January 2024 and March 2025, a specially equipped monitoring vehicle traversed over 4,000 kilometers of routes throughout the industrial park, collecting real-time data on odor units and eight key odorant compounds. This approach offered several advantages over traditional fixed-site monitoring: high spatial resolution enabling identification of localized hotspots, temporal flexibility to capture emissions during peak complaint periods, rapid coverage of large industrial areas, and direct source attribution through spatial correlation analysis.
The portable multi-sensor odor analyzer simultaneously measured ammonia (NH₃), hydrogen sulfide (H₂S), trimethylamine (TMA), methanethiol, dimethyl sulfide, dimethyl disulfide, carbon disulfide, and styrene, compounds associated with the region’s dominant industries.
Key Findings: Night-time, Seasonality, and the Limits of TVOC Metrics
Odor pollution peaks at night. Mean odor unit values in Priority Monitoring Zones reached 10.2 at night compared to 8.3 during daytime, a statistically significant increase attributed to reduced atmospheric mixing and potential shifts in industrial production schedules.
Seasonal patterns reflect meteorological conditions. Summer (July-August) and winter (December) showed elevated odor levels, corresponding to periods of low wind speeds and temperature inversions that trap pollutants near ground level.
Spatial hotspots correlate with specific industries. Two locations emerged as persistent problem areas: J Avenue (65% night-time anomaly probability) surrounded by chemical and pharmaceutical plants, and the H Street/F Road intersection (48%) near food and feed additive manufacturers.
TVOC concentrations do not tell the full story. While total VOC levels remained consistently low (0.11–0.15 mg/m³), odor activity values (OAVs) revealed that compounds like trimethylamine and methanethiol, with exceptionally low odor thresholds, contributed disproportionately to perceived odor impact.
From Mass-Based to Perception-Based Metrics
Perhaps the study’s most significant finding is the inadequacy of TVOC-based regulation for addressing odor nuisance. Hydrogen sulfide and ammonia dominated mass concentrations, but when assessed by odor activity values, trimethylamine and methanethiol emerged as key contributors despite their relatively low concentrations.
This matters because regulatory frameworks often rely on mass-based thresholds that fail to account for compounds with ultra-low detection thresholds. A facility may be fully compliant with TVOC standards while still generating substantial odor complaints, exactly the situation observed in Tuoketuo.
Implications for Industrial Pollution Management
The findings support several targeted interventions: enhanced night-time enforcement in identified high-risk corridors, OAV-based odor assessment frameworks to complement existing mass concentration standards, sector-specific Best Available Techniques (BATs) for odor-intensive industries including fermentation, chemical, and pharmaceutical manufacturing, and improved waste management protocols for microbial fermentation byproducts and sulfur-containing residues.
Looking Ahead
While mobile monitoring offers excellent spatial resolution, it cannot provide continuous measurements at fixed locations. Future research should combine mobile and fixed-site approaches, integrate health exposure assessments, and incorporate citizen-reported odor events to strengthen the public health relevance of odor studies.
As industrial parks worldwide grapple with balancing economic development and community well-being, this work provides a scientifically grounded foundation for improving odor monitoring, regulation, and management.
This research was published in Atmospheric Environment (Volume 366, January 2026) and was supported by the Fujian Provincial Science and Technology Innovation Fund, Tianjin Science & Technology Program Project, and National Foreign Experts Individual Project.
Reference: Li, C., Jia, Y., Qiu, Y., Cordeiro, C.M., Li, S., Chen, Y., Liu, J., Siesler, H.W., Wu, H., & Zhao, R. (2026). Analysis of odor and VOCs pollution in industrial parks of central inner Mongolia autonomous region based on mobile monitoring. Atmospheric Environment, 366, 121703. https://doi.org/10.1016/j.atmosenv.2025.121703