CO2 Concentration Measurements Research Articles

Application of a low‐cost NDIR sensor module for continuous measurements of in situ soil CO2 concentration

AbstractWe tested the performance of a newly developed CO2 probe, K33SOIL [based on the sensor module K33 (Senseair, Sweden)], under harsh temperature and humidity conditions in a laboratory experiment. The K33SOIL, competed well (RMSE = 0.032% CO2) with the often used GMP343 (Vaisala, Finland) in precision and accuracy. A field experiment showed that the K33SOIL is also suitable for in situ applications. Thus, the K33SOIL is a valuable and cost‐efficient tool for measurement of soil CO2 concentration.

Assessment of Qualitative Characteristics of Carbon Dioxide Respiration Rates Evaluation in Wheat Measurements

This study comprises a brief summary of the quantification method for measuring carbon dioxide respiration rate (CO2 RR) in wheat as well as reliability criteria for this method. Assessed accuracy characteristics of the method enabled complex evaluation of the measurement uncertainty. Mathematical model of the CO2 RR measurement was estimated and the uncertainty sources were identified. Expanded uncertainty is calculated according to the measurement process conditions. The sources of uncertainty including sample preparation and method implementation were established using the Ishikawa diagram. A procedure of RR measurement uncertainty estimation based on the ISO GUM method is presented. A case study of CO2 RR measurement of wheat at 19% moisture content and 25 °C temperature is shown. Influence (%) of uncertainty components on the combined uncertainty is presented. Performed calculations revealed that the contributions of CO2 concentration measurement (including sampling), sample moisture content measurement and environmental conditions are the most significant factors, contributing about 97% to the overall uncertainty. The elimination of small uncertainty components was also discussed. CO2 RR for different values, from 10 to 38 (mgCO2/kg wheat/h), in wheat were measured with the expanded uncertainty of ± 2.5–6.1% (k = 2, 95% confidence level).

Workplace exposure to carbon dioxide during routine laparoscopy – is it safe?

Background: Minimally invasive surgeries have increased dramatically during the last decades. Carbon dioxide (CO 2) is the gas used for insufflation during laparoscopies, creating space and visibility. The CO 2 leaks into ambient air through ports where instruments are inserted. If the CO 2 reaches a certain concentration it affects personnel health. There are national occupational exposure limits (OEL) for CO 2, including a level limit value (LLV) of 5000 ppm. We are not aware of any previous studies addressing occupational exposure to CO 2 during laparoscopies. The aim of this study was to assess the compliance to national OELs for CO 2 during laparoscopies. Methods: A gas detector was placed in the breathing zone of personnel in the operating theatre. The detector measured CO 2 concentrations every tenth minute during laparoscopies in three locations. Results: During 27 laparoscopies, the measured CO 2 reached a maximum concentration of 1100 ppm, less than one fourth of the LLV. Median CO 2 concentration was 700 ppm. Conclusion: Results show that the occupational exposure to CO 2 during laparoscopies is well below set OELs. Our findings support personnel safety associated with routine use of CO 2 during laparoscopies.

Farmed calcite δ13C at Ascunsă cave, Romania, and its relation with CO2

When calcite precipitates in caves, its carbon stable isotope signature can be modified by the CO2 outgassing gradient between drip water and cave atmosphere. This effect is modulated by the water residence time in the cave, from its emergence in the cave until the deposition of calcite. Moreover, CO2 solubility, calcite precipitation rate, and isotopic fractionation are controlled by temperature. Here, we present up to date results of an ongoing monitoring study at Ascunsa Cave (Romania), exploring the relationship between farmed calcite δ13C, drip rate, and CO2 outgassing. In addition to measuring CO2 concentration in cave air, we also measured the CO2 concentration in the headspace of a water-air equilibrator that collects drip water without exposing it to cave atmosphere, preventing outgassing. δ13C from calcite farmed at two neighboring stalagmites with different drip rates was also measured. Although caves have generally stable temperatures, we show here that temperature inside Ascunsa and Isverna caves has risen by more than 2°C over the course of a year, bearing important implications for stable isotopic fractionation equations and CO2 dynamics. Our results show that δ13C of farmed calcite has a strong relationship with drip rate at the slow dripping site, but no correlation at the faster dripping site. These two sites are also different when δ13C is compared to the outgassing gradient. At the slower drip site, δ13C and the outgassing gradient are directly correlated, whereas at the faster drip site their correlation is inverse. Our study brings new light onto speleothem δ13C behavior in general, and at Ascunsa Cave in particular, which is crucial for understanding the paleoclimate information captured by speleothems from this cave or elsewhere.

Partitioning ecosystem respiration of a Platycladus orientalis forest in the west mountainous area of Beijing, China using stable carbon isotope

Based on stable carbon isotope, we quantitatively partitioned ecosystem respiration in a Platycladus orientalis forest in the west mountainous area of Beijing. Results from this study could lay the foundation for carbon exchange research in forest ecosystems of this region. The spectroscopy technique was used to continuously measure CO2 concentrations and δ13C values at different height of the forest. Soil and branch chambers were used for measuring nighttime δ13C values in underground and aboveground respiration, and then the proportions of respiration components were calculated. Combined with soil respiration efflux measurement, ecosystem respiration was then quantitatively partitioned. The results showed that δ13C values of respiratory components fluctuated, which ranged from -31.74‰ to -23.33‰ in aboveground respiration of plants and from -32.11‰ to -27.74‰ in soil respiration. The δ13C values of ecosystem respiration was at the middle of those ranges. Soil respiration averaged 1.70 μmol·m-2·s-1 at night, accounting for 47%-91% of ecosystem respiration. Aboveground respiration averaged 0.72 μmol·m-2·s-1, contributing less to ecosystem respiration. Daytime respiration based on isotope mixing model calculation had greater variability than that based on temperature response model, with a mean value of 2.31 μmol·m-2·s-1 and 2.28 μmol·m-2·s-1, respectively.

In vitro characterization of PrismaLung+: a novel ECCO2R device

BackgroundInvasive mechanical ventilation is lifesaving in the setting of severe acute respiratory failure but can cause ventilation-induced lung injury. Advances in extracorporeal CO2 removal (ECCO2R) technologies may facilitate more protective lung ventilation in acute respiratory distress syndrome, and enable earlier weaning and/or avoid invasive mechanical ventilation entirely in chronic obstructive pulmonary disease exacerbations. We evaluated the in vitro CO2 removal capacity of the novel PrismaLung+ ECCO2R device compared with two existing gas exchangers.MethodsThe in vitro CO2 removal capacity of the PrismaLung+ (surface area 0.8 m2, Baxter) was compared with the PrismaLung (surface area 0.35 m2, Baxter) and A.L.ONE (surface area 1.35 m2, Eurosets) devices, using a closed-loop bovine blood–perfused extracorporeal circuit. The efficacy of each device was measured at varying pCO2 inlet (pinCO2) levels (45, 60, and 80 mmHg) and blood flow rates (QB) of 200–450 mL/min; the PrismaLung+ and A.L.ONE devices were also tested at a QB of 600 mL/min. The amount of CO2 removed by each device was assessed by measurement of the CO2 infused to maintain circuit equilibrium (CO2 infusion method) and compared with measured CO2 concentrations in the inlet and outlet of the CO2 removal device (blood gas analysis method).ResultsThe PrismaLung+ device performed similarly to the A.L.ONE device, with both devices demonstrating CO2 removal rates ~ 50% greater than the PrismaLung device. CO2 removal rates were 73 ± 4.0, 44 ± 2.5, and 72 ± 1.9 mL/min, for PrismaLung+, PrismaLung, and A.L.ONE, respectively, at QB 300 mL/min and pinCO2 45 mmHg. A Bland–Altman plot demonstrated that the CO2 infusion method was comparable to the blood gas analysis method for calculating CO2 removal. The resistance to blood flow across the test device, as measured by pressure drop, varied as a function of blood flow rate, and was greatest for PrismaLung and lowest for the A.L.ONE device.ConclusionsThe newly developed PrismaLung+ performed more effectively than PrismaLung, with performance of CO2 removal comparable to A.L.ONE at the flow rates tested, despite the smaller membrane surface area of PrismaLung+ versus A.L.ONE. Clinical testing of PrismaLung+ is warranted to further characterize its performance.

Smart Material Serves Other Smart Materials: Comparison of Measurement of CO2 Concentration by Optical and Optoacoustic Methods

In this study, we compare the sensitivity of the Wavelength Modulation Spectroscopy (WMS) to the Quartz enhanced photoacoustic spectroscopy (QEPAS) method on a sample of CO2 gas at various concentrations. We show the advantages of the QEPAS method, the essential part of which is a crystalline segment made of smart material.

Air quality and fossil fuel driven transportation in the Metropolitan Area of São Paulo

In this paper, we use origin and destination mobility surveys and high-resolution assignment and emission models to study air quality and short-lived climate pollutant impacts related to on-road transportation in the Metropolitan Area of São Paulo (MASP). To begin with, we calculate transport carbon dioxide (CO2) emissions from fossil fuel-driven vehicles (light and heavy-duty) at spatial and temporal resolutions of 500 m and one hour, by means of traffic demand forecasting. These estimates, carry out for 2007 and 2012, are based on passenger and freight trips and the height of the atmospheric boundary layer, among other variables. These proxies depend also on ancillary parameters as particulate matter concentrations and dilution rates. In the second place, we evaluate the changes in CO2 emissions from the MASP (3%/year). Transport emission inventories combine mobility surveys and road network assignments with air quality data. In spite of using different methodologies, bottom-up road link assignments versus top-down vehicle activity-based and fuel consumption approaches, the estimated CO2 emissions are consistent with the Official São Paulo State's Inventory. This work found that the CO2 emissions in MASP were 10,044 and 11,503 t Ceq./day in 2007 and 2012 (73% light and 27% heavy vehicles), respectively. On-road emission patterns agree with the spatial-temporal variation of transportation journeys and corresponding passenger and freight network assignments. Temporal patterns, diurnal, weekly and monthly, were determined using traffic counts and congestion surrogates. The patterns were also crosschecked with average CO2 measurements, available for 2014 at the road (western area of MASP) and background sites (Jaraguá Peak). Kerbside road measurements showed two prominent peaks associated to the morning (437 ± 45 ppm) and night rush hours (435 ± 49 ppm), coupled to low values of boundary layer height (313 m) and dilution rate (329 m2/h). Background values (414 ± 2 ppm) were subtracted from on-road measurements to estimate excess CO2 (12 ± 8 ppm) directly attributed to vehicles. The inventory reflects the relationships between traffic patterns and emissions, and the developed methodology could be used to evaluate the impacts of forthcoming urban transport and emission control policies. In the future, our estimates will be verified with ground measurements of CO2 concentrations over a bigger monitoring network in the MASP.

Enhanced regional terrestrial carbon uptake over Korea revealed by atmospheric CO2 measurements from 1999 to 2017.

Understanding changes in terrestrial carbon balance is important to improve our knowledge of the regional carbon cycle and climate change. However, evaluating regional changes in the terrestrial carbon balance is challenging due to the lack of surface flux measurements. This study reveals that the terrestrial carbon uptake over the Republic of Korea has been enhanced from 1999 to 2017 by analyzing long-term atmospheric CO2 concentration measurements at the Anmyeondo Station (36.53°N, 126.32°E) located in the western coast. The influence of terrestrial carbon flux on atmospheric CO2 concentrations (ΔCO2 ) is estimated from the difference of CO2 concentrations that were influenced by the land sector (through easterly winds) and the Yellow Sea sector (through westerly winds). We find a significant trend in ΔCO2 of -4.75ppm per decade (p<.05) during the vegetation growing season (May through October), suggesting that the regional terrestrial carbon uptake has increased relative to the surrounding ocean areas. Combined analysis with satellite measured normalized difference vegetation index and gross primary production shows that the enhanced carbon uptake is associated with significant nationwide increases in vegetation and its production. Process-based terrestrial model and inverse model simulations estimate that regional terrestrial carbon uptake increases by up to 18.9 and 8.0TgC for the study period, accounting for 13.4% and 5.7% of the average annual domestic carbon emissions, respectively. Atmospheric chemical transport model simulations indicate that the enhanced terrestrial carbon sink is the primary reason for the observed ΔCO2 trend rather than anthropogenic emissions and atmospheric circulation changes. Our results highlight the fact that atmospheric CO2 measurements could open up the possibility of detecting regional changes in the terrestrial carbon cycle even where anthropogenic emissions are not negligible.

Comparison between Linear and Branched Polyethylenimine and Reduced Graphene Oxide Coatings as a Capture Layer for Micro Resonant CO2 Gas Concentration Sensors.

The comparison between potential coatings for the measurement of CO2 concentration through the frequency shift in micro-resonators is presented. The polymers evaluated are linear polyethylenimine, branched polyethylenimine and reduced graphene oxide (rGO) by microwave reduction with polyethylenimine. The characterization of the coatings was made by using 6 MHz gold-plated quartz crystals, and a proof-of-concept sensor is shown with a diaphragm electrostatic microelectromechanical systems (MEMS) resonator. The methods of producing the solutions of the polymers deposited onto the quartz crystals are presented. A CO2 concentration range from 0.05% to 1% was dissolved in air and humidity level were controlled and evaluated. Linear polyethylenimine showed superior performance with a reaction time obtained for stabilization after the concentration increase of 345 s, while the time for recovery was of 126 s, with a maximum frequency deviation of 33.6 Hz for an in-air CO2 concentration of 0.1%.

CO-concentration and temperature measurements in reacting CH4/O2 mixtures doped with diethyl ether behind reflected shock waves

The oxidation of CH4/diethyl ether mixtures was studied with laser absorption-based time-resolved temperature and CO concentration measurements behind reflected shock waves. Fuel-rich (equivalence ratio ϕ = 2.0) mixtures were studied because of their relevance for mechanism development for partial oxidation reactions in the context of polygeneration processes and measurements at ϕ = 0.5 and 1.0 were used to verify the mechanism performance in an extended range of equivalence ratios. Temperature and CO concentration were measured via absorption using two fundamental vibrations of CO (ν" = 0, P20 and ν" = 1, R21) with two mid-IR quantum-cascade lasers near 4.8546 and 4.5631 µm. Interference from broadband absorption of CO2 in the region near 4.56 µm was quantified based on measured temperature-dependent CO2 absorption cross-sections and mechanism-based prediction of CO2 concentrations. The measured temporal CO-concentration and temperature profiles were compared with simulations based on two mechanisms (Fikri et al., 2017; Yasunaga et al., 2010). For mixtures with ϕ = 0.5, the two mechanisms show similar results, and well reproduce the experimental data. At ϕ = 1.0 and 2.0, the Fikri et al. mechanism shows very good agreement with the experiments whereas the Yasunaga et al. mechanism predicts a too fast CO-concentration and temperature rise.

Ambient Carbon Dioxide in Industrial and Commercial Area Measured by Unmanned Aerial Vehicle (UAV)

The CO2 gas is a gas produced from various activities related to industrial activities and people activities in residential or commercial areas. Conventionally, measurements of CO2 concentrations are carried out using the NDIR method with stationary devices. Still, the tool has a disadvantage that is difficult to do in locations that are difficult to reach with height. So this research is intended to measure ambient CO2 in the Industrial Estate and Commercial area using Unmanned Aerial Vehicle (UAV) technology. We sampled in 10 sites at each location. The output of measurements were then plotted with Surfer software to know the spatial distribution. The results of the study show the CO2 concentrations varied between sites. CO2 concentration was higher at industrial area than at commercial area. At Industrial and Commercial area the transport sector may the main causes of high ambient CO2.

Effect of protrusion amount on gas ingestion of radial rim seal

In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO2 concentration and pressure, in order to obtain the optimal protrusion amount. The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 105 and the rotating Reynolds number was 1.05 × 106. The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible. But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion. The variation of power consumption is the same. A complex vortex structure will appear at the high radius region when the protrusion is installed. On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity. Furthermore, considering the sealing efficiency and power consumption, the best range of the protrusion amount is about 36. The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.

Urban land cover type determines the sensitivity of carbon dioxide fluxes to precipitation in Phoenix, Arizona.

Urbanization modifies land surface characteristics with consequent impacts on local energy, water, and carbon dioxide (CO2) fluxes. Despite the disproportionate impact of cities on CO2 emissions, few studies have directly quantified CO2 conditions for different urban land cover patches, in particular for arid and semiarid regions. Here, we present a comparison of eddy covariance measurements of CO2 fluxes (FC) and CO2 concentrations ([CO2]) in four distinct urban patches in Phoenix, Arizona: a xeric landscaping, a parking lot, a mesic landscaping, and a suburban neighborhood. Analyses of diurnal, daily, and seasonal variations of FC and [CO2] were related to vegetation activity, vehicular traffic counts, and precipitation events to quantify differences among sites in relation to their urban land cover characteristics. We found that the mesic landscaping with irrigated turf grass was primarily controlled by plant photosynthetic activity, while the parking lot in close proximity to roads mainly exhibited the signature of vehicular emissions. The other two sites that had mixtures of irrigated vegetation and urban surfaces displayed an intermediate behavior in terms of CO2 fluxes. Precipitation events only impacted FC in urban patches without outdoor water use, indicating that urban irrigation decouples CO2 fluxes from the effects of infrequent storms in an arid climate. These findings suggest that the proportion of irrigated vegetation and urban surfaces fractions within urban patches could be used to scale up CO2 fluxes to a broader city footprint.

Microplasma emission spectroscopy of carbon dioxide using the carbon monoxide Ångström system

The present paper describes a system and method for indirect emission spectroscopy of CO2 in the visible spectrum. This is achieved by using a microplasma spectrometer that first converts CO2 into CO and then measures emissions from the CO Ångström system (B1Σ + → A1Π) at 560 nm. The experiments were performed on gaseous samples of CO2, mixed in both N2 and air, to concentrations between 0.01% and 100%. In addition to the microplasma spectrometer, the process was monitored by mass spectrometry with a residual gas analyzer. The CO2 to CO conversion efficiency was found to be very high, reaching a maximum of 41% at close to 100% selectivity. Furthermore, the CO Ångström system was shown to facilitate excellent spectroscopic measurement of CO2 concentrations below 10%, with a linearity of R2 &amp;gt; 0.99 and an expected limit of detection in the parts-per-thousands range. The most promising aspect of the results was that the analysis was performed on extremely small total sample amounts where the gas flow through the systems was in the 0.1 µmole/s range. Hence, the present system has the prospect of filling a void in current sensor technology, where inexpensive and easy-to-use optical systems, such as nondispersive infrared sensors, cannot handle small sample amounts, while mass spectrometers, which can handle such samples, still are expensive, complex, and bulky.

Ventilation and laboratory confirmed acute respiratory infection (ARI) rates in college residence halls in College Park, Maryland

Strategies to protect building occupants from the risk of acute respiratory infection (ARI) need to consider ventilation for its ability to dilute and remove indoor bioaerosols. Prior studies have described an association of increased self-reported colds and influenza-like symptoms with low ventilation but have not combined rigorous characterization of ventilation with assessment of laboratory confirmed infections. We report a study designed to fill this gap. We followed laboratory confirmed ARI rates and measured CO2 concentrations for four months during the winter-spring of 2018 in two campus residence halls: (1) a high ventilation building (HVB) with a dedicated outdoor air system that supplies 100% of outside air to each dormitory room, and (2) a low ventilation building (LVB) that relies on infiltration as ventilation. We enrolled 11 volunteers for a total of 522 person-days in the HVB and 109 volunteers for 6069 person-days in the LVB, and tested upper-respiratory swabs from symptomatic cases and their close contacts for the presence of 44 pathogens using a molecular assay. We observed one ARI case in the HVB (0.70/person-year) and 47 in the LVB (2.83/person-year). Simultaneously, 154 CO2 sensors distributed primarily in the dormitory rooms collected 668,390 useful data points from over 1 million recorded data points. Average and standard deviation of CO2 concentrations were 1230 ppm and 408 ppm in the HVB, and 1492 ppm and 837 ppm in the LVB, respectively. Importantly, this study developed and calibrated multi-zone models for the HVB with 229 zones and 983 airflow paths, and for the LVB with 529 zones and 1836 airflow paths by using a subset of CO2 data for model calibration. The models were used to calculate ventilation rates in the two buildings and potential for viral aerosol migration between rooms in the LVB. With doors and windows closed, the average ventilation rate was 12 L/s in the HVB dormitory rooms and 4 L/s in the LVB dormitory rooms. As a result, residents had on average 6.6 L/(s person) of outside air in the HVB and 2.3 L/(s person) in the LVB. LVB rooms located at the leeward side of the building had smaller average ventilation rates, as well as a somewhat higher ARI incidence rate and average CO2 concentrations when compared to those values in the rooms located at the windward side of the building. Average ventilation rates in twenty LVB dormitory rooms increased from 2.3 L/s to 7.5 L/s by opening windows, 3.6 L/s by opening doors, and 8.8 L/s by opening both windows and doors. Therefore, opening both windows and doors in the LVB dormitory rooms can increase ventilation rates to the levels comparable to those in the HVB. But it can also have a negative effect on thermal comfort due to low outdoor temperatures. Simulation results identified an aerobiologic pathway from a room occupied by an index case of influenza A to a room occupied by a possible secondary case.

Study of Air Quality in the Office Building

This paper is devoted to assessment of air quality in an office space of a public building. Analysis of the results of researches made in this area by Russian and foreign authors showed that state of human health deteriorates at CO2 concentration level of 600-800 ppm and more and this can lead to decrease in performance and increased fatigue of office workers. Long-term human exposure to carbon dioxide can lead to chronic diseases. Results of experimental study of changes in carbon dioxide concentration in 30 m2 office space of a public building when 5 people are continually present in the office are given in this paper. CO2 concentration measurement was carried out during 24 hour period using MT 8057 portable carbon dioxide detector. According to the measurements results, a graph of CO2 concentration changes versus time was drawn. Conclusion that, in some periods of working day, air quality was unsatisfactory (from 10:40 to 13:30 and from 14:45 to 19:00: CO2 concentration exceeded 1000 ppm) indicates insufficiency of existing ventilation system and excessive room sealing (due to application of plastic windows). There is a need in technical solutions to improve efficiency of supply and exhaust ventilation.

School building experimental characterization in Mediterranean climate regarding comfort, indoor air quality and energy consumption

Public school buildings represent an important share of public buildings in Europe, some of them built several decades ago. In Portugal, there are about 5800 public schools, many of them in free-running conditions, with significant thermal discomfort and without any heating strategy due to economic restrictions. This work studies the Portuguese Brandão school model (from the ‘70 s), which comprises about 100 non-refurbished basic schools. This paper suggests the passive refurbishment of these public schools with some affordable interventions, regarding the climate features and the reduced capacity to support the operating costs. A prototype classroom was prepared in a Brandão school, in Porto. The in situ experimental campaign consisted of temperature, relative humidity, CO2 concentration and energy consumption measurements. The prototype construction included the improvement of the envelope and of the technical systems. The main goals of this work are: (1) the comparison of the prototype in-service thermal performance in pre-existing conditions and the improvement after the refurbishment in free-running conditions or with some intermittent heating strategies; (2) the establishment of discomfort indexes for the assessment of the discomfort for Mediterranean temperate climate; (3) the quantification of the energy consumption vs discomfort regarding the passive refurbishment strategy and the intermittent heating strategies. When comparing the before and after refurbishment results, the mean daily discomfort indicator has decreased from 34.7 °C.hour to 25.2 °C.hour in free-running conditions and after the refurbishment has decreased from 25.2 °C.hour to 11.9 °C.hour for 3 heating hours strategy and to 2.5 °C.hour for 10 heating hours strategy. There was an expected increase of CO2 inside the classroom for the corresponding months before and after refurbishment, although the mean CO2 was below the required 1500 ppm.

Assessment of Urban CO2 Measurement and Source Attribution in Munich Based on TDLAS-WMS and Trajectory Analysis

Anthropogenic carbon dioxide (CO2) emissions mainly come from cities and their surrounding areas. Thus, continuous measuring of CO2 in urban areas is of great significance to studying human CO2 emissions. We developed a compact, precise, and self-calibrated in-situ CO2/H2O sensor based on TDLAS (tunable diode laser absorption spectroscopy), WMS (wavelength modulation spectroscopy), and VCSEL (vertical-cavity surface-emitting laser). Multi-harmonic detection is utilized to improve the precision of both measurements to 0.02 ppm for CO2 and 1.0 ppm for H2O. Using the developed sensor, we measured CO2 concentrations continuously in the city center of Munich, Germany, from February 2018 to January 2019. Urban CO2 concentrations are strongly affected by several factors, including vegetation photosynthesis and respiration (VPR), planetary boundary layer (PBL) height, and anthropogenic activities. In order to further understand the anthropogenic contribution in terms of CO2 sources, the HySPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model was applied to calculate six-hour backward trajectories. We analyzed the winter CO2 with the trajectory clustering, PSCF (potential source contribution function), and CWT (concentration weighted trajectory) methods, and found that local emissions have a great impact on urban CO2 concentration, with main emission sources in the north and southeast directions of the measurement site. In situations with an uneven trajectory distribution, PSCF proves somewhat superior in predicting the potential emission sources compared to CWT.

Early-stage concentrations of formaldehydes and TVOCs in a new low-energy building

This paper deals with temporary discomfort caused by characteristic odours from new objects and materials in office buildings. Earlier investigations have shown that increased ventilation rates in residential buildings decrease the indoor concentrations of non-occupant-related indoor air pollutants such as aldehydes and total volatile organic compounds (TVOCs). To study how this basic principle for the control of indoor air pollutants complies with a demand-controlled ventilation, which is an important energy efficiency measure in modern office buildings, the authors have designed and conducted a serial of field tests. Concentrations of aldehydes and TVOCs have been measured in two newly built and identical meeting rooms under different ventilation strategies. By overruling the existing demand control ventilation and increasing gradually but differently the air change rates in the rooms over a course of five weeks, the concentration of formaldehyde and TVOCs decreased for about 75 % from the initial values of ca. 45 μg/m3 and ca. 400 μg/m3 respectively. Impact of door openings on instantaneous indoor air quality has been studied in parallel by combining CO2 measurements and numerical simulations. Good agreement was found between the simulated and measured CO2 concentrations and thereby the door opening model was verified.