Mapping neural circuits is critical for understanding the structure and function of the nervous system.Engineered viruses are a valuable tool for tracing neural circuits.However,current tracers do not fully meet the n...Mapping neural circuits is critical for understanding the structure and function of the nervous system.Engineered viruses are a valuable tool for tracing neural circuits.However,current tracers do not fully meet the needs for this approach because of various drawbacks,such as toxicity and characteristics that are difficult to modify.Therefore,there is an urgent need to develop a new tracer with low toxicity and that allows for long-term studies.In this study,we constructed an engineered Sindbis virus(SINV)expressing enhanced green fluorescent protein(EGFP)reporter gene(SINV-EGFP)and found that it had no significant difference in biological characterization compared with the wild-type Sindbis virus in BHK-21 cells and neurons in vitro.We injected the virus into the visual circuit of mouse brain and found that the virus infected neurons in the local injected site and anterogradely spread in the neural circuits.Although the efficiency of transmission was limited,the findings demonstrate that SINV can be used as a new anterograde tracer to map neural circuits in mouse brain and that it spreads exclusively in the anterograde direction.Further,use of SINV in mouse brain research will provide longer time windows for circuit tracing than is possible with herpes simplex virus and vesicular stomatitis virus tracers.展开更多
Sensory processing is strongly modulated by different brain and behavioral states,and this is based on the top-down modulation.In the olfactory system,local neural circuits in the olfactory bulb(OB)are innervated by c...Sensory processing is strongly modulated by different brain and behavioral states,and this is based on the top-down modulation.In the olfactory system,local neural circuits in the olfactory bulb(OB)are innervated by centrifugal afferents in order to regulate the processing of olfactory information in the OB under different behavioral states.The purpose of the present study was to explore the organization of neural networks in olfactory-related cortices and modulatory nuclei that give rise to direct and indirect innervations to the glomerular layer(GL)of the OB at the whole-brain scale.Injection of different recombinant attenuated neurotropic viruses into the GL showed that it received direct inputs from each layer in the OB,centrifugal inputs from the ipsilateralanterior olfactory nucleus(AON),anterior piriform cortex(Pir),and horizontal limb of diagonal band of Broca(HDB),and various indirect inputs from bilateral cortical neurons in the AON,Pir,amygdala,entorhinal cortex,hippocampus,HDB,dorsal raphe,median raphe and locus coeruleus.These results provide a circuitry basis that will help further understand the mechanism by which olfactory informationprocessing in the OB is regulated.展开更多
A central objective in deciphering the nervous system in health and disease is to define the connections of neurons. The propensity of neurotropic viruses to spread among synaptically-linked neurons makes them ideal f...A central objective in deciphering the nervous system in health and disease is to define the connections of neurons. The propensity of neurotropic viruses to spread among synaptically-linked neurons makes them ideal for mapping neural circuits. So far, several classes of viral neuronal tracers have become available and provide a powerful toolbox for delineating neural networks. In this paper, we review the recent developments of neurotropic viral tracers and highlight their unique properties in revealing patterns of neuronal connections.展开更多
Background: Sentinel lymph node (SLN) biopsy remains a cornerstone in the management of breast cancer, as it provides an accurate staging of the disease while minimizing the morbidity associated with complete axillary...Background: Sentinel lymph node (SLN) biopsy remains a cornerstone in the management of breast cancer, as it provides an accurate staging of the disease while minimizing the morbidity associated with complete axillary lymph node dissection. Advances in SLN detection have been very important in refining surgical techniques and improving patient outcomes. The purpose of the present study is to compare the effectiveness of radiocolloids, blue dyes, and fluorescent tracers in detecting the sentinel lymph node in breast cancer. Materials and Methods: Specifically, we analyzed the detection rate, accuracy, and safety profile of the techniques to outline the most reliable and clinically available. A comprehensive review was conducted, searching key databases, including PubMed, Scopus, and Web of Science, for studies published between 2010 and 2024. The review focused on studies that compared the performance of radiocolloids, blue dyes, and fluorescent tracers in the detection of sentinel lymph nodes in breast cancer patients. A total of 54 studies were included based on specific inclusion criteria. Results: Radiocolloids showed high detection rates in studies. Blue dyes have comparable results, but a small percentage of allergic reactions has been observed. Fluorescent tracers such as indocyanine green have improved visualization and accuracy, but their use requires specialized equipment and expertise. Combining radiocolloids with blue dyes or fluorescent tracers has improved detection rates in several studies. Cost and accessibility challenges have also been pointed out, particularly in low-resource settings. Conclusions: Radiocolloids have attained the status of gold standard in the detection of SLNs in breast cancer for their reliability and accuracy. While combined use with other tracers, like blue dyes or fluorescent agents, enhances overall detection performance, making it more holistic. As expected, further innovation and effort are required to improve accessibility and optimize the technique of sentinel lymph node biopsy worldwide.展开更多
AMPA Receptor and PET Tracer Limitation.The alpha-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid receptor(AMPAR)is a subtype of ionotropic glutamate receptor.It functions as a ligand-gated ion channel and is primar...AMPA Receptor and PET Tracer Limitation.The alpha-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid receptor(AMPAR)is a subtype of ionotropic glutamate receptor.It functions as a ligand-gated ion channel and is primarily responsible for rapidly transmitting the signal from glutamate in the central nervous system[1].This receptor plays a crucial role in various cognitive functions including learning,memory,cognition,synaptic plasticity,and neurodevelopment.AMPARs are typically composed of four subunits,namely GluA1,GluA2,GluA3,and GluA4,which can form homo-or hetero-tetramers.These subunits bind directly or indirectly to various scaffolding proteins such as transmembrane AMPA receptor regulatory proteins(TARPs).展开更多
The groundwater(GW)in the floodplain riparian area frequently interacts intensely with surface water(SW).Heat as a tracer is one of the hot research fields in investigating GW-SW interactions,and analytical approaches...The groundwater(GW)in the floodplain riparian area frequently interacts intensely with surface water(SW).Heat as a tracer is one of the hot research fields in investigating GW-SW interactions,and analytical approaches have been proposed for the calculation of exchange flow velocity.However,few studies have considered the effects of very dynamic flow conditions and monitoring instrumentation on the calculation with field measured data.Herein,taking the middle reaches of the Heihe River as the study area,different types of monitoring wells were constructed under the riverbed and near the river,and multiple methods(Darcy’s law,heat tracing,and isotopic mixing methods)were employed to trace the exchanges between the river and groundwater.The results indicate that different methods demonstrate diverse information with obvious unevenly distributed flux along the vertical direction.And the combination of multiple methods has an important role in studying the interaction between GW and SW.Fully screened wells produce intraborehole flow and disturb the heat transport,which is relevant to flow velocity,and further affects the temperature distribution,impacting the temperature-based flow velocity calculation.Dynamic flow conditions aggravate riverbed sediment disturbances,e.g.,scour and deposition,and additionally affect the interaction and monitoring data.展开更多
As an efficient monitoring and prediction tool,chemical tracers have been widely applied in reservoir characterization,production monitoring,water resources monitoring,and various other fields.Chemical tracer technolo...As an efficient monitoring and prediction tool,chemical tracers have been widely applied in reservoir characterization,production monitoring,water resources monitoring,and various other fields.Chemical tracer technology is characterized by high efficiency,high precision,relatively simple operational procedures,and low cost.Owing to the limitations of existing tracers,such as minimal options,limited transport efficiency,and complex detection methods,this study used fluorescein isothiocyanate and a ruthenium complex(Ru(phen_(3))^(2+))to synthesize 50 nm multi-color fluorescent silica nanoparticle tracers using an improved St ober method based on fluorescence resonance energy transfer(FRET).Due to the FRET between the two compounds,the synthesized tracer exhibited the characteristics of multi-color fluorescence,and its fluorescent color varied with the mixing ratio of the two precursor solutions.The fluorescence intensity of the synthesized tracer was significantly higher than that of the monochromatic fluorescent nano-tracer.Fourier-transform infrared spectroscopy,ultraviolet spectrophotometry,and fluorescence spectrometry were used to characterize the structure,maximum absorption wavelength,and fluorescence characteristics of the synthesized tracer,respectively.The experimental results show that the synthesized tracer has a maximum absorption wavelength of 450 nm and an emission wavelength of 576 nm.Under field emission scanning electron microscopy,the tracer appears as uniformly spherical particles with a size of 50±5 nm.It exhibited good dispersibility and fluorescence characteristics in reservoir environments that varied in temperature(25-85°C)and salinity(1000-10000 mg/L).The effects of environmentally sensitive clay minerals,tracer particle size,injection concentration,fluid salinity,and flow rate on the transport characteristics(retention)of tracers in sandstone cores were studied using 12 sets of tracer breakthrough experiments.The experimental results showed that increased sensitivity to clay minerals,salinity,and tracer particle size were not conducive to tracer migration in the core.In contrast,increased tracer injection concentration and flow rate were beneficial to tracer migration in the core.展开更多
The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the...The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the influence of continental and marine air masses over the Pearl River Estuary(PRE)region in winter 2021.The sum concentration of SOA tracers was 6.2–132.8 ng m^(−3),with SOAM and SOAI as the main components in both continental(scenarios A1 and A2)and marine air masses(scenario A3),as well as their combination(scenario A4).The highest and lowest levels of SOAM were observed in A1 and A3,respectively,which were mainly related to the variations in meteorological conditions,precursor concentrations,and the degree of photochemical processes.Higher MBTCA/HGA(3-methyl-1,2,3-butanetricarboxylic acid/3-hydroxyglutaric acid)ratios suggested a less significant contribution fromα-pinene to SOAM.The variations of SOAI in the different scenarios were associated with differences in relative humidity,particle acidity,and isoprene/NOx ratios.The respective highest and lowest concentrations of aromatics SOA tracers in A1 and A3 revealed the influence of anthropogenic precursors from upwind continental areas,which was confirmed by the correlation among biogenic and anthropogenic precursors.The results of the tracer-based-method suggested dominant contributions of SOAs from aromatics and monoterpenes,with the highest concentrations in A1.A WRF-Chem simulation revealed that the SOAs from the above precursors only contributed 12%–25%to the total SOA at DWS,while the spatial distributions of SOAs further highlighted that the abundance of SOAs over the PRE region in winter is highly associated with air masses transported from upwind continental areas.展开更多
High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for und...High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for understanding the dispersion process of tailpipe emissions in street canyons,while a major challenge is the lack of a suitable tracer gas.Carbon dioxide(CO_(2)),which is safe to the public and inexpensive to obtain,can be reliably measured by existing gas analysers.This study investigated the suitability of using CO_(2)as a tracer gas for characterising vehicle emission dispersion in a real-world street canyon.The tracer gas was released via a line or point source,whose dispersion was characterised by a sensors network comprising low-cost air quality sensors.The results showed that the CO_(2)contained in the exhaust gas of a test vehicle itself had unmeasurable effect at roadsides.Both the line and point sources produced obvious CO_(2)level elevations at approximately 30 s after the test vehicle passed by.In addition,for both line and point sources,the CO_(2)elevations were much more distinct at the roadside next to tailpipe exit than the opposite side,and were higher at 0.8 m than 1.6 m above the ground.The present study demonstrated that using CO_(2)as a tracer gas is feasible for investigating vehicle emission dispersion in real-world street canyons.Future studies are needed to improve the gas release rate of the developed tracer gas systems for more reliable measurements and larger street canyons.展开更多
基金supported by the National Natural Science Foundation of China, Nos.31830035, 91732304, 91632303, 81661148053, and 31771156(all to FQX)the Key-Area Research and Development Program of Guangdong Province of China, No.2018B030331001(to FQX)+4 种基金the SIAT Innovation Program for Excellent Young Researchers of China,No.E1G023(to FJ)the Guangdong Basic and Applied Basic Research Foundation of China, No.2021A1515011235(to FQX)Shenzhen Key Laboratory of Viral Vectors for Biomedicine of China, No.ZDSYS20200811142401005(to FQX)the National Basic Research Program(973 Program)of China, No.2015CB755600(to FQX)the Strategic Priority Research Program(B)of China, No.XDB32030200(to FQX)
文摘Mapping neural circuits is critical for understanding the structure and function of the nervous system.Engineered viruses are a valuable tool for tracing neural circuits.However,current tracers do not fully meet the needs for this approach because of various drawbacks,such as toxicity and characteristics that are difficult to modify.Therefore,there is an urgent need to develop a new tracer with low toxicity and that allows for long-term studies.In this study,we constructed an engineered Sindbis virus(SINV)expressing enhanced green fluorescent protein(EGFP)reporter gene(SINV-EGFP)and found that it had no significant difference in biological characterization compared with the wild-type Sindbis virus in BHK-21 cells and neurons in vitro.We injected the virus into the visual circuit of mouse brain and found that the virus infected neurons in the local injected site and anterogradely spread in the neural circuits.Although the efficiency of transmission was limited,the findings demonstrate that SINV can be used as a new anterograde tracer to map neural circuits in mouse brain and that it spreads exclusively in the anterograde direction.Further,use of SINV in mouse brain research will provide longer time windows for circuit tracing than is possible with herpes simplex virus and vesicular stomatitis virus tracers.
基金supported by grants from the National Natural Science Foundation of China (31400946, 31671120, 31771197, 31329001, 31771156, 91632303, and 81661148053/H09)the Strategic Priority Research Program of Chinese Academy of Science (XDB32030200)the National Basic Research Development Program (973 Program) of China (2015CB755600)
文摘Sensory processing is strongly modulated by different brain and behavioral states,and this is based on the top-down modulation.In the olfactory system,local neural circuits in the olfactory bulb(OB)are innervated by centrifugal afferents in order to regulate the processing of olfactory information in the OB under different behavioral states.The purpose of the present study was to explore the organization of neural networks in olfactory-related cortices and modulatory nuclei that give rise to direct and indirect innervations to the glomerular layer(GL)of the OB at the whole-brain scale.Injection of different recombinant attenuated neurotropic viruses into the GL showed that it received direct inputs from each layer in the OB,centrifugal inputs from the ipsilateralanterior olfactory nucleus(AON),anterior piriform cortex(Pir),and horizontal limb of diagonal band of Broca(HDB),and various indirect inputs from bilateral cortical neurons in the AON,Pir,amygdala,entorhinal cortex,hippocampus,HDB,dorsal raphe,median raphe and locus coeruleus.These results provide a circuitry basis that will help further understand the mechanism by which olfactory informationprocessing in the OB is regulated.
基金supported by the National Natural Science Foundation of China (31671119 and 31871090)the Shenzhen Science and Technology Innovation Commission (JCYJ20160428164440255, JCYJ20170413162938668, JCYJ20170818155056369, and JCYJ20170307170742519)+3 种基金the Shenzhen Discipline Construction Project for Neurobiology (DRCSM [2016]1379)the Japan Society for the Promotion of Science KAKENHI (JP18K08494) the Japan Science and Technology Agency PRESTO (JPMJPR1784)the Ono Medical Research Foundation, and the Novartis Foundation (Japan) for the Promotion of Science
文摘A central objective in deciphering the nervous system in health and disease is to define the connections of neurons. The propensity of neurotropic viruses to spread among synaptically-linked neurons makes them ideal for mapping neural circuits. So far, several classes of viral neuronal tracers have become available and provide a powerful toolbox for delineating neural networks. In this paper, we review the recent developments of neurotropic viral tracers and highlight their unique properties in revealing patterns of neuronal connections.
文摘Background: Sentinel lymph node (SLN) biopsy remains a cornerstone in the management of breast cancer, as it provides an accurate staging of the disease while minimizing the morbidity associated with complete axillary lymph node dissection. Advances in SLN detection have been very important in refining surgical techniques and improving patient outcomes. The purpose of the present study is to compare the effectiveness of radiocolloids, blue dyes, and fluorescent tracers in detecting the sentinel lymph node in breast cancer. Materials and Methods: Specifically, we analyzed the detection rate, accuracy, and safety profile of the techniques to outline the most reliable and clinically available. A comprehensive review was conducted, searching key databases, including PubMed, Scopus, and Web of Science, for studies published between 2010 and 2024. The review focused on studies that compared the performance of radiocolloids, blue dyes, and fluorescent tracers in the detection of sentinel lymph nodes in breast cancer patients. A total of 54 studies were included based on specific inclusion criteria. Results: Radiocolloids showed high detection rates in studies. Blue dyes have comparable results, but a small percentage of allergic reactions has been observed. Fluorescent tracers such as indocyanine green have improved visualization and accuracy, but their use requires specialized equipment and expertise. Combining radiocolloids with blue dyes or fluorescent tracers has improved detection rates in several studies. Cost and accessibility challenges have also been pointed out, particularly in low-resource settings. Conclusions: Radiocolloids have attained the status of gold standard in the detection of SLNs in breast cancer for their reliability and accuracy. While combined use with other tracers, like blue dyes or fluorescent agents, enhances overall detection performance, making it more holistic. As expected, further innovation and effort are required to improve accessibility and optimize the technique of sentinel lymph node biopsy worldwide.
基金supported by the National Natural Science Foundation of China(32371066)the Guangdong Basic and Applied Basic Research Foundation(2022A1515010134)+1 种基金the Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions(NYKFKT2019009)the Shenzhen Technological Research Center for Primate Translational Medicine(XMHT20220104005).
文摘AMPA Receptor and PET Tracer Limitation.The alpha-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid receptor(AMPAR)is a subtype of ionotropic glutamate receptor.It functions as a ligand-gated ion channel and is primarily responsible for rapidly transmitting the signal from glutamate in the central nervous system[1].This receptor plays a crucial role in various cognitive functions including learning,memory,cognition,synaptic plasticity,and neurodevelopment.AMPARs are typically composed of four subunits,namely GluA1,GluA2,GluA3,and GluA4,which can form homo-or hetero-tetramers.These subunits bind directly or indirectly to various scaffolding proteins such as transmembrane AMPA receptor regulatory proteins(TARPs).
基金supported by the National Natural Science Foundations of China(No.42425207)the Key R&D Program of the Xinjiang Uygur Autonomous Region(No.2024B03022).
文摘The groundwater(GW)in the floodplain riparian area frequently interacts intensely with surface water(SW).Heat as a tracer is one of the hot research fields in investigating GW-SW interactions,and analytical approaches have been proposed for the calculation of exchange flow velocity.However,few studies have considered the effects of very dynamic flow conditions and monitoring instrumentation on the calculation with field measured data.Herein,taking the middle reaches of the Heihe River as the study area,different types of monitoring wells were constructed under the riverbed and near the river,and multiple methods(Darcy’s law,heat tracing,and isotopic mixing methods)were employed to trace the exchanges between the river and groundwater.The results indicate that different methods demonstrate diverse information with obvious unevenly distributed flux along the vertical direction.And the combination of multiple methods has an important role in studying the interaction between GW and SW.Fully screened wells produce intraborehole flow and disturb the heat transport,which is relevant to flow velocity,and further affects the temperature distribution,impacting the temperature-based flow velocity calculation.Dynamic flow conditions aggravate riverbed sediment disturbances,e.g.,scour and deposition,and additionally affect the interaction and monitoring data.
基金funded by the Sichuan Science and Technology Education Joint Fund,including the mechanism and characterization of CO_(2) geological storage and utilization of carbonate reservoirs in the Sichuan Basin to improve the sealing capacity of mudstone caprocks(No.2024NSFSC1981)also supported by the China Petroleum Science and Technology Innovation Fund,including the experiment of acoustic response mechanism of horizontal well fracturing and the research of DAS big data intelligent inversion method(No.2022DQ02-0305)also supported by the National Natural Science Foundation of China'Study on the mechanism of SNPs improving the sealing ability of mudstone caprock in CO_(2) geological storage(No.42272176)。
文摘As an efficient monitoring and prediction tool,chemical tracers have been widely applied in reservoir characterization,production monitoring,water resources monitoring,and various other fields.Chemical tracer technology is characterized by high efficiency,high precision,relatively simple operational procedures,and low cost.Owing to the limitations of existing tracers,such as minimal options,limited transport efficiency,and complex detection methods,this study used fluorescein isothiocyanate and a ruthenium complex(Ru(phen_(3))^(2+))to synthesize 50 nm multi-color fluorescent silica nanoparticle tracers using an improved St ober method based on fluorescence resonance energy transfer(FRET).Due to the FRET between the two compounds,the synthesized tracer exhibited the characteristics of multi-color fluorescence,and its fluorescent color varied with the mixing ratio of the two precursor solutions.The fluorescence intensity of the synthesized tracer was significantly higher than that of the monochromatic fluorescent nano-tracer.Fourier-transform infrared spectroscopy,ultraviolet spectrophotometry,and fluorescence spectrometry were used to characterize the structure,maximum absorption wavelength,and fluorescence characteristics of the synthesized tracer,respectively.The experimental results show that the synthesized tracer has a maximum absorption wavelength of 450 nm and an emission wavelength of 576 nm.Under field emission scanning electron microscopy,the tracer appears as uniformly spherical particles with a size of 50±5 nm.It exhibited good dispersibility and fluorescence characteristics in reservoir environments that varied in temperature(25-85°C)and salinity(1000-10000 mg/L).The effects of environmentally sensitive clay minerals,tracer particle size,injection concentration,fluid salinity,and flow rate on the transport characteristics(retention)of tracers in sandstone cores were studied using 12 sets of tracer breakthrough experiments.The experimental results showed that increased sensitivity to clay minerals,salinity,and tracer particle size were not conducive to tracer migration in the core.In contrast,increased tracer injection concentration and flow rate were beneficial to tracer migration in the core.
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant Nos.42230701,91644215)the National Natural ScienceFoundation of China(Grant Nos.42122062 and 42307137)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515010852)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.23hytd002)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.SML2023SP218)L.M.acknowledges the Zhuhai Science and Technology Plan Project(Grant No.ZH22036201210115PWC).
文摘The compositions and distributions of monoterpenes,isoprene,aromatics and sesquiterpene SOA tracers(SOAM,SOAI,SOAA and SOAS,respectively)at an island site(Da Wan Shan Island,DWS)were investigated in the context of the influence of continental and marine air masses over the Pearl River Estuary(PRE)region in winter 2021.The sum concentration of SOA tracers was 6.2–132.8 ng m^(−3),with SOAM and SOAI as the main components in both continental(scenarios A1 and A2)and marine air masses(scenario A3),as well as their combination(scenario A4).The highest and lowest levels of SOAM were observed in A1 and A3,respectively,which were mainly related to the variations in meteorological conditions,precursor concentrations,and the degree of photochemical processes.Higher MBTCA/HGA(3-methyl-1,2,3-butanetricarboxylic acid/3-hydroxyglutaric acid)ratios suggested a less significant contribution fromα-pinene to SOAM.The variations of SOAI in the different scenarios were associated with differences in relative humidity,particle acidity,and isoprene/NOx ratios.The respective highest and lowest concentrations of aromatics SOA tracers in A1 and A3 revealed the influence of anthropogenic precursors from upwind continental areas,which was confirmed by the correlation among biogenic and anthropogenic precursors.The results of the tracer-based-method suggested dominant contributions of SOAs from aromatics and monoterpenes,with the highest concentrations in A1.A WRF-Chem simulation revealed that the SOAs from the above precursors only contributed 12%–25%to the total SOA at DWS,while the spatial distributions of SOAs further highlighted that the abundance of SOAs over the PRE region in winter is highly associated with air masses transported from upwind continental areas.
基金supported by the Environment and Conservation Fund(No.ECF 14/2018)of the Hong Kong SAR Government,China.
文摘High-rise buildings form deep urban street canyons and restrict the dispersion of vehicle emissions,posing severe health risks to the public by aggravating roadside air quality.Field measurements are important for understanding the dispersion process of tailpipe emissions in street canyons,while a major challenge is the lack of a suitable tracer gas.Carbon dioxide(CO_(2)),which is safe to the public and inexpensive to obtain,can be reliably measured by existing gas analysers.This study investigated the suitability of using CO_(2)as a tracer gas for characterising vehicle emission dispersion in a real-world street canyon.The tracer gas was released via a line or point source,whose dispersion was characterised by a sensors network comprising low-cost air quality sensors.The results showed that the CO_(2)contained in the exhaust gas of a test vehicle itself had unmeasurable effect at roadsides.Both the line and point sources produced obvious CO_(2)level elevations at approximately 30 s after the test vehicle passed by.In addition,for both line and point sources,the CO_(2)elevations were much more distinct at the roadside next to tailpipe exit than the opposite side,and were higher at 0.8 m than 1.6 m above the ground.The present study demonstrated that using CO_(2)as a tracer gas is feasible for investigating vehicle emission dispersion in real-world street canyons.Future studies are needed to improve the gas release rate of the developed tracer gas systems for more reliable measurements and larger street canyons.
