CO2, a trace gas, plays a critical role in the greenhouse effect and the global carbon cycle. Over the past few decades, rapid and significant industrial development (resulting in high emissions), transportation advancements and urban-isation (with varying emission levels) have led to a substantial increase in anthropogenic carbon dioxide emissions, particularly in densely populated urban areas. The emission of carbon dioxide into the atmosphere has emerged as a pressing issue with wide-ranging environmental impacts. Human activities, including fossil-fuel combustion and cement production, contribute more carbon dioxide to the atmosphere than natural processes can remove. Roughly 50% of anthropogenic carbon dioxide is absorbed by the biosphere and oceans, while the remainder accumulates, elevating the atmospheric carbon dioxide concentration. Presently, atmospheric carbon dioxide levels are nearly 50% higher than those observed before the industrial revolution began. In October 2022, the average monthly level of CO2 in the Earth’s atmosphere exceeded 416 ppm. Additionally, in April 2023, the monthly average CO2 level at the Mauna Loa observatory surpassed 423 ppm (source:
Monitoring CO2 levels is of utmost importance in understanding the local carbon cycle and various environmental interactions. With recent changes in energy sector policies, research data on CO2 levels can serve as vital information sources for comparing the carbon cycle in selected cities with that of the natural environment. The diurnal pattern of CO2 may be primarily influenced by biological processes such as soil CO2 respiration as well as anthropogenic sources related to fossil-fuel usage (e.g. traffic intensity variations and heating or air conditioning demands), atmospheric transport and planetary boundary layer (PBL) dynamics (Fang
Analysing the CO2 balance in urban areas holds significant importance due to the concentrated human activities and infrastructure present in cities. Urban environments are characterised by high population densities, extensive energy consumption and various emission sources such as industries, transportation networks and residential sectors. Understanding the CO2 dynamics in urban settings provides crucial insights into the efficiency of carbon-management strategies, urban planning and the potential for mitigating greenhouse gas emissions (Fang
In Poland, industrial emissions have been limited, but the contribution from traffic and households remains significant (Różański
The systematic measurement of the CO2 air mole fraction in Gliwice with high temporal resolution and reasonable accuracy to catch the diurnal cycle was started in August 2022 (Sensuła, 2023, Sensuła
In summary, the analysis of the urban CO2 balance plays a vital role in tackling the challenges of climate change, thereby contributing to sustainable urban development. It will help in identifying emission sources, guiding mitigation efforts and shaping policies that aim to create healthier, more environmentally friendly cities.
This study focusses on measuring CO2 concentrations in the atmosphere of Gliwice city and comparing them with the levels measured by two well-established monitoring stations: the Kraków city observatory and the Kasprowy Wierch mountain observatory. Continued research and analysis are necessary to better understand the specific drivers of CO2 concentrations in urban areas and their implications for atmospheric composition and climate change.
CO2 concentrations were measured in the atmosphere of the city of Gliwice and compared with two other long-operating stations: the Kraków city observatory and the Kasprowy Wierch mountain observatory (
The analysis of CO2 levels in the Kraków area was initiated in 1984, while at Kasprowy Wierch, it began in 1994. However, in Kraków, the research was not conducted continuously; regular analysis was carried out from 2012 to 2015, followed by a break from 2016 to 2021. Currently, the analysis has been reinitiated. On the other hand, investigations in Kasprowy Wierch have been ongoing since 1994 without interruption. In Gliwice, a new sampling system was established in 2022.
The KASLAB station is located at the peak of Kasprowy Wierch in the Tatra Mountains. The Kasprowy Wierch peak is situated in the convergence area of three valleys (the Kasprowa, Gasienicowa and Dolina Cichej valleys), approximately 300 m above the tree line. Such a position favours the occurrence of anabatic and katabatic winds. The wind statistics indicate the southern and north-eastern wind directions to be the most frequently observed ones. The measurement laboratory is located in the meteorological observatory building. The air intake is installed ca. 2 m above the roof of the building, 1989 m a.s.l. Apart from short episodes related to the use of snow groomers at the top and specific winds from the northern valley, which are filtered out from the measurement record by quality assurance (QA) and quality control (QC) procedures, the station is free from local anthropogenic influences and represents the regional CO2 background.
Krakow, the second-largest Polish city located in Lesser Poland, is populated by almost 1 million inhabitants spread out over an area of 326.8 km2. The city’s area belongs to three geographical regions, i.e. the Polish Uplands, the Western Carpathians and the basin of the Carpathian Foredeep in between. Krakow is located in the Wisla river valley at the altitude of ca. 200 m a.s.l. and is surrounded by highly populated towns and villages located at uplands and hilltops bordering the city and reaching ca. 100 m above the valley floor. In the eastern part of the city, an energy-production and steelworks industry is located. In 2019, the city authorities had banned the use of solid fuels within the city borders, but in the surrounding areas, there are still a number of old-fashioned stoves used for house-heating purposes. Another important anthropogenic CO2 source is the high traffic prevalent within the city area. The measurement site is located in the western part of the city on the AGH University of Krakow campus. The air intake apparatus is installed on the top of 20 m high tower placed on the roof of the faculty building (ca. 40 m a.g.l.).
Gliwice, the third-largest city in the Upper Silesian metropolitan area, has a population of approximately 180,000 residents. It is situated approximately 30 km west of Katowice (with a population of approximately 300,000 inhabitants), 100 km northwest of Kraków, and about 150 km west of the Tatra Mountains. The Upper Silesian metropolitan area represents a typical urban environment characterised by rapid growth in vehicular traffic and significant industrial activities. This region is heavily influenced by large-scale coal mining, steelworks, power plants and chemical factories within the industrial district. The main sources of anthropogenic CO2 emissions in the area stem from the local combustion of coal, gas, oil and bio-mass used for communal and transportation purposes. The measurement site in Gliwice is located on the university campus in the city centre. The air intake device is positioned on the roof of a faculty building, approximately 2 m above the roof and at around 20 m above ground level. The thermal conditions in Gliwice during the investigated period were similar to those in Kraków (as shown in
Based on the thermal data obtained from the local meteorological station (
In the same period of time, the data based on the CO2 observations made at Mauna Loa and Maunakea Observatories are presented by Pieter Tans (
The results presented within the Integrated Carbon Observation System (ICOS) simulation (
At the Silesian University of Technology site in Gliwice, the continuous measurement of atmospheric CO2 began in August 2022. To measure the mole fraction of CO2, the CARBOCAP GMP-343 probe (Vaisala, Finland) was employed, capable of connecting to three different registers: MI70, DL2 and directly to a computer. The GMP-343 probe was equipped with a built-in temperature sensor, allowing for appropriate correction of optical cavity variations. At the AGH stations, measurements were conducted using Cavity ring-down spectroscopy (CRDS) analysers, specifically the Piccaro (USA) G-2311-f and G-2101-i spectrometers.
Meteorological data were obtained from local meteorological stations in Gliwice. Until February, data were collected from the Hydrowskaz platform, and from February 2022 onwards, data were obtained from the database from the local meteorological station installed on the roof the building of the Faculty of Environmental Engineering and Power Engineering (The Silesian University of Technology,
All CO2 concentration data are reported in accordance with the established standardised scale (
The preliminary data collected for the summer and autumn of 2022 (Sensuła, 2023; Sensuła
According to the manufacturer’s specifications, each CARBOCAP GMP343 probe is calibrated using ±0.5% accurate gases at various concentrations. In the range of 370–420 ppm, the expected accuracy is approximately 2 ppm. Calibration of the instrument using reference gases in May 2023 showed relatively low standard deviations (approximately 2 ppm) for each reference gas. However, there was a notable difference between the data recorded by the two loggers (analogue and digital) compared to the expected CO2 levels in the reference gases.
It is important to mention that the concentration of CO2 in the reference gases is regularly monitored. To recheck the parameters of the CARBOCAP GMP343 probe, the same reference gases were simultaneously measured using a Piccaro spectrometer in Kraków. The CO2 concentrations measured by the Piccaro spectrometers were found to be in agreement with the recommended values provided by the manufacturer.
The first discrepancy in the results obtained from the CARBOCAP GMP343 probe was observed between the data recorded by the analogue logger (DL2) and that by the digital recorder (MI70 as indicator and display). This constant shift amounted to 6.9 ppm over time, indicating an underestimation of CO2 levels in all data from the analogue record. Furthermore, multipoint calibration revealed that all digital records were further underestimated by approximately 7–10 ppm compared to the three reference gases (
In the research and analysis, the following corrections were applied to the raw CO2 data obtained from the digital recorder, with their respective effects on precision:
Correction for underestimation by the digital recorder: +6.9 ppm. This correction was necessary to account for the consistent underestimation of CO2 levels in the data recorded by the digital device. Correction based on the response function of the calibration curve: This correction was made to address the underestimation of data compared to the reference gases. The specific effect on precision varied depending on the calibration curve’s response function. Compensation for the effects of humidity and oxygen: The accuracy of the CO2 measurements was affected by humidity and oxygen levels. Humidity compensation ranged between ±0.006% of the reading/g/m3 H2O below 1000 ppm CO2 (not exceeding 0.25% of the reading), while oxygen compensation was −0.09% of the reading/%O2 (not exceeding 0.2% of the reading). Compensation for the effect of temperature: Temperature compensation was necessary due to the impact of temperature on accuracy. The range of compensation varied between 1% and 3% of the reading, as specified in the user guide, with a minimum compensation of 10 ppm. Temperature compensation was performed using an integrated Pt1000 element. Pressure compensation: After measurement, pressure compensation was applied using the formula provided by the manufacturer. In many cases, if the temperature compensation of the GMP-343 was activated, pressure compensation alone was sufficient.
These corrections and compensations were implemented to ensure the accuracy and precision of the CO2 measurements and to account for various factors that could influence the recorded data.
AP2 = −155.36 BP2 = 209.51 CP2 = −68.42 DP2 = 9.2681 EP2 = 0
The iteration loop is repeated until i = 10.
Thus, the effect of pressure on the accuracy range is between 0.5% and 1% of reading (according to
All data collected since August 2022 have undergone recalculation with the aforementioned corrections and their associated effects on accuracy. The shift between the raw results obtained from the analogue register, including the correction for pressure compensation, could be up to approximately 40 ppm for individual data points. The uncertainty of the new single results, after applying all corrections and compensations, does not exceed 12 ppm. This includes the mode of operation mentioned earlier, with adjustments made for ambient pressure compensations. For instrument calibration, it is recommended to follow a three-step process. Firstly, using the analogue signal register as the display, the metres should be checked and verified to ensure consistency with the digital signal. Any discrepancies should be taken into account when correcting the data. Secondly, for long-term analysis, it is advisable to utilise temperature compensation performed by an integrated Pt1000 element. The fixed value for pressure compensation should be turned off and the environmental pressure data from other metres should be considered, applying the formula provided by the manufacturer. Lastly, it is recommended to calibrate the instruments more frequently than the manufacturer’s recommended interval. The preliminary results indicate that calibration should be performed more often, as a shift of approximately 10 ppm was observed after just a few months.
Following these calibration steps and considering the necessary corrections and compensations ensure accurate and precise CO2 measurements and help maintain the reliability of the collected data.
Thermal conditions (minimal, maximal and mean air temperature) and mean value of the CO2 air mole fraction in Gliwice, Kraków, and Kasprowy Wierch from 1 August 2022 to 31 March 2023.
Gliwice | Kraków | Kasprowy Wierch | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Air temperature, °C | CO2, ppm | Air temperature, °C | CO2, ppm | CO2, ppm | ||||||||||
Min | Max | Mean | SD | Mean | SD | Min | Max | Mean | SD | Mean | SD | Mean | SD | |
August 2022 | 11.86 | 35.12 | 21.3 | 4.7 | 437 | 35 | 11.9 | 33.8 | 21.2 | 4.2 | 437 | 29 | 407.0 | 5.7 |
September 2022 | 5.06 | 28.00 | 13.6 | 4.1 | 435 | 22 | 3.9 | 27.4 | 13.6 | 4.1 | 435 | 24 | 409.2 | 4.0 |
October 2022 | 1.28 | 23.00 | 12.3 | 3.9 | 451 | 33 | 1 | 25.2 | 12.0 | 4.4 | 458 | 34 | 409.6 | 4.8 |
November 2022 | −7.90 | 16.94 | 4.5 | 4.8 | 459 | 19 | −6.6 | 18 | 5.0 | 4.8 | 460 | 25 | 414.2 | 2.1 |
December 2022 | −10.90 | 12.90 | 1.5 | 4.3 | 434 | 17 | −12 | 13.6 | 1.3 | 4.3 | 453 | 21 | 415.6 | 3.0 |
January 2023 | −4.00 | 15.60 | 3.8 | 3.5 | 437 | 13 | −2.9 | 16.4 | 3.5 | 3.4 | 449 | 20 | 423.8 | 3.2 |
February 2023 | −12.20 | 10.10 | 1.9 | 4.5 | 443 | 18 | −10.6 | 11.4 | 2.3 | 4.3 | 442 | 14 | 423.6 | 2.0 |
March 2023 | −6.70 | 18.00 | 5.1 | 5.5 | 438 | 15 | −4.4 | 21.8 | 6.6 | 5.5 | 442 | 19 | 424.6 | 1.6 |
SD represents the standard deviations of the presented mean values.
A noteworthy relationship between temperature and CO2 levels in the air is observed. In Kraków, local peaks in CO2 concentration are observed during nocturnal temperature inversions in the lower troposphere, particularly in summer. On the other hand, Kasprowy Wierch exhibits less variation in the diurnal dynamics of CO2 during summer and fall. During winter, higher CO2 levels are associated with lower air temperatures, particularly when frost occurs. However, when considering the mean values and the scatter of the results (1σ), no significant differences in monthly mean CO2 values are observed between Kraków and Gliwice. The scatter of the monthly mean CO2 levels is evident in both urban areas (Gliwice and Kraków). Nevertheless, when analysing individual days or hours, the differences between the two sites become more apparent.
These findings highlight the complex relationship between CO2 levels, temperature and urban environments. The data suggest that while both cities exhibit similar monthly mean CO2 values, there are distinct variations in diurnal patterns and seasonal dynamics. Further investigation and analysis of these patterns will contribute to a better understanding of the factors influencing CO2 concentrations in urban and mountainous regions.
The previous studies performed in Krakow (Zimnoch
The much lower variability observed at the Kasprowy Wierch station is due to the location of the measurement point most of the time above the boundary layer, which is seen separating the station from the direct influences of nearby CO2 emission sources (Necki
In 2022 and 2023, in both the urban areas, Gliwice and Kraków, the impact of various factors on CO2 is evident. In Gliwice, the mean difference between nocturnal and daytime CO2 levels varied throughout the months, confirming that these results were due to the impact of the anthropogenic (including different fuels’ combustion from different sources) and biogenic factors, including photosynthesis and respiration, in the past years. Unfortunately, the models presented by the ICOS are limited and do not cover the period of time for the measurements conducted within these studies.
For example, in August, the difference was approximately 70 ppm, while in September, it was around 35 ppm. In October, the difference increased to approximately 50 ppm, followed by a decrease to 16 ppm in November. In December, the difference was around 6 ppm, and in January and February, it was approximately 10 ppm. In March, the difference was around 18 ppm. Similarly, in Kraków, the mean difference between nocturnal and daytime CO2 levels showed a similar pattern, with values around 60 ppm in August, 35 ppm in September, 60 ppm in October, 20 ppm in November, 8 ppm in December, 17 ppm in January, 12 ppm in February and approximately 24 ppm in March. These variations in diurnal CO2 levels may be influenced by local effects, contributing to higher or lower concentrations. At Kasprowy Wierch, the differences between nocturnal and daytime CO2 levels were generally minimal, ranging from a few parts per million in summer to 1–2 ppm in fall and winter.
The thermal conversion effect in the atmosphere has been noted, particularly during the nocturnal period. As the temperature decreases at night, the air layer close to the Earth’s surface, enriched with CO2 from plants and soil respiration, can undergo convection and migrate to higher parts of the atmosphere. This phenomenon can lead to dilution and a decrease in CO2 levels if there is sufficient mixing of air masses. However, in situations with limited air mass mixing, such as calm or non-windy weather, higher concentrations of CO2 can persist in the atmosphere for longer durations. Moreover, the biosphere activity has been dominating (but not exclusively) in summer and fall, while anthropogenic sources became more prominent in winter, following the end of the vegetation period. The impact of photosynthesis and plant respiration on CO2 levels becomes limited from late fall until the beginning of the new vegetation period, typically starting in mid-March in Poland. During this period, there was no significant decrease in CO2 levels during the day and an increase at night, as observed during summer. The effects of air mass mixing and fluxes may influence CO2 concentrations in urban areas. Studies conducted in Łódź analysed CO2 exchange above dense built-up city centres, revealing that carbon dioxide emissions generally surpass absorption throughout the year, except for the summer season when lower anthropogenic CO2 emissions coincide with absorption through photosynthesis, resulting in the lowest net flux of CO2 (Pawlak
In summary, our research highlights the complex interplay of various factors influencing diurnal CO2 variations in urban and mountainous regions. Further investigations into these local effects, thermal conversions and air mass mixing will contribute to a better understanding of the dynamics of CO2 concentrations and their spatial and temporal variations.