## 2 Materials and Methods
### Evaluation of Treatment Effectiveness and Data Analysis  
The overall mean percent reduction for each measured targeted gas was estimated using:  
\[\%\ \mathrm{R}=(\mathrm{C}_{\mathrm{con}}-\mathrm{C}_{\mathrm{Treat}})/ \mathrm{C}_{\mathrm{con}}\ \times\ 100 \tag{1}\]  
where C\({}_{\mathrm{Con}}\) and C\({}_{\mathrm{Treat}}\) are the mean measured concentrations in control and treated air, respectively. For odor and odorous VOCs, odor units (OUE\(\cdot\)m\({}^{-3}\)) and MS detector responses (peak area counts, PAC) were used.  
Emissions were calculated as a product of measured gas concentrations and the total airflow rate through the UV mobile lab, adjusted for standard conditions and dry air using collected environmental data. The overall mean emission of each measured gas was estimated as:  
\[\text{Emission (g\text{-}min^{-1})}=\text{C }\times\text{V}\times(273.15\text{ K}\times\text{MW})/(273.15\text{ K}+\text{T})\times(2.24\times 10^{4}) \tag{2}\]  
where C = the mean measured target gas concentration in control and treated air (mL/m\({}^{3}\), OU\({}_{\text{E}}\)/m\({}^{3}\)). V = the treated airflow rate (m\({}^{3}\)/min). MW = the molecular weight of the targeted gas (g/mol). T = the temperature in the control and treated air. The 2.24 \(\times\) 10\({}^{4}\) is an ideal gas conversion factor for L to moles at 273.15 K [13].  
The electric energy consumption during UV treatment was estimated using the measured power consumption by lamps:  
\[\text{EEC}=\text{P}\times\text{t}_{\text{s}}/(3600\times 1000) \tag{3}\]  
where EEC = electric energy consumption (kWh). P = measured electric power consumption for the UV lamps turned 'on' during treatment (W). t\({}_{\text{s}}\) = treatment time for air irradiated with the UV lamps that were turned 'on' inside the mobile lab (s).  
The mass of mitigated gas pollutant (M) with UV during given treatment time (t\({}_{\text{s}}\)) was estimated by comparing gas emission rate (E) in treatment and control:  
\[\text{M}=(\text{E}_{\text{con}}-\text{E}_{\text{treat}})\times\text{t}_{\text {s}}/60 \tag{4}\]  
where M = mass of mitigated gas pollutant (g). E\({}_{\text{con}}\) = emission rate at the 'control' sampling location. E\({}_{\text{treat}}\) = emission rate at the 'treatment' sampling location.  
The electric energy of UV treatment (EE, kWh/g) was estimated as using electric energy consumption (EEC) needed to mitigate a gas pollutant mass (M):  
\[\text{EE}=\text{EEC}/\text{M} \tag{5}\]  
Finally, the estimated cost of electric energy (Cost) needed for UV treatment was estimated using the mean cost of rural energy in Iowa (USD 0.13/kWh):  
\[\text{Cost}=\text{EE}\times\text{USD 0.13/kWh} \tag{6}\]  
where Cost = estimated cost of electric energy needed for UV treatment to mitigate a unit mass of pollutants in the air (USD/g).  
UV dose was estimated using measured light intensity (I) at a specific UV wavelength (mW/cm\({}^{2}\)) and treatment time (t\({}_{\text{s}}\)). Since the photocatalysis reaction was assumed to be the primary mechanism for the target gas mitigation, the light intensity irradiated on the TiO\({}_{2}\) surface was used. For lamps emitting light at multiple UV wavelengths, the UV dose was calculated using the light intensity of the primary wavelength suggested by the lamp manufacturer.  
\[\text{UV dose}=\text{I}\times\text{t}_{\text{s}} \tag{7}\]  
where UV Dose = energy of the UV light on the surface of photocatalyst (mJ/cm\({}^{2}\)).