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With the rapid growth of greenhouse gas (GHG) monitoring satellites, more and more studies focused on the issue of inversion/optimization of carbon dioxide (CO2) fluxes using satellite-derived XCO2 observations in recent years. A common and critical challenge in this framework is the separation of background and anomalies from XCO2 observations, which directly affect the performance of the CO2 fluxes’ inversion. We proposed a novel method to accurately extract background XCO2 from satellite observations. A series of observing system simulation experiments (OSSEs) were performed to test the performance of the method. We found that the bias and uncertainty of the background concentration are below 0.01 and 0.05 ppm in the given cases, respectively. Based on this method, we selected five overpasses from 2014 to 2016 to demonstrate a regional-scale flux inversion near Riyadh. The comparison with the two previous methods shows that the posterior simulated XCO2 by the method proposed in this article can match better with the observed XCO2 from Orbiting Carbon Observatory-2 (OCO-2). [ABSTRACT FROM AUTHOR]

Oceans are widely regarded as major offsets for anthropogenic carbon emissions, leading to an evident lower measured atmospheric CO2 concentration than expected. It is thus of great significance to develop effective means to monitor CO2 fluxes over oceans globally. In this work, we utilized observations obtained by an airborne CO2‐IPDA LIDAR to evaluate the potential of such means in estimating sea‐air CO2 flux. During a flight experiment in 2019, we have estimated the CO2 exchange rate, −1.5 ± 0.18 mmol/m2/h, between the Bohai Bay and the atmosphere using equilibrium atmospheric boundary layer theory. These findings indicated that the forthcoming space‐borne CO2‐IPDA LIDAR is capable of identifying CO2 uptakes over oceans qualitatively, which would be a novel means and a basis for monitoring CO2 fluxes over global oceans. Plain Language Summary: Oceans are regarded as important offsets to anthropogenic CO2 emissions, delaying an increase in atmospheric CO2 concentration. However, there is a lack of understanding of the intensity, distribution, and variability of marine carbon sinks. China is due to launch a space‐borne LIDAR for measuring atmospheric CO2 concentration globally in 2021. In this work, we utilized data collected during a flight test for the forthcoming satellite mission to explore the ability of such a novel means in revealing and estimating CO2 fluxes of oceans quantitatively. Results confirmed an evident CO2 uptake in the Bohai Bay and exhibited a promising prospect for the novel CO2 measuring means. Key Points: We detected XCO2 gradient during a flight campaign in ChinaRetrieve XCO2 in the atmosphere boundary layer by cloud slicing methodProvide a model to retrieve CO2 flux over ocean by CO2‐IPDA system [ABSTRACT FROM AUTHOR]

For high-precision measurements of the CO2 column concentration in the atmosphere with airborne integrated path differential absorption (IPDA) Lidar, the exact distance of the Lidar beam to the scattering surface, that is, the length of the column, must be measured accurately. For the high-precision inversion of the column length, we propose a set of methods on the basis of the actual conditions, including autocorrelation detection, adaptive filtering, Gaussian decomposition, and optimized Levenberg–Marquardt fitting based on the generalized Gaussian distribution. Then, based on the information of a pair of laser pulses, we use the direct adjustment method of unequal precision to eliminate the error in the distance measurement. Further, the effect of atmospheric delay on distance measurements is considered, leading to further correction of the inversion results. At last, an airborne experiment was carried out in a sea area near Qinhuangdao, China on 14 March 2019. The results showed that the ranging accuracy can reach 0.9066 m, which achieved an excellent ranging accuracy on 1.57-μm IPDA Lidar and met the requirement for high-precision CO2 column length inversion. [ABSTRACT FROM AUTHOR]

The plasmid-mediated tet (X4) gene has exhibited a high-level resistance to tigecycline (TGC), which has raised concerns globally regarding antibiotic resistance. Although the widespread tet (X4) has been found widely in Escherichia coli , it is scarcely found in other Enterobacteriaceae. This study aimed to characterize a ST469 Salmonella enterica serovar Rissen ( S. Rissen) isolate harboring tet (X4) from pork, which was identified and characterized via antimicrobial susceptibility testing, conjugation assays, plasmid curing testing, whole-genome sequencing, and bioinformatic analysis. Ten ST469 S. Rissen isolates of 223 Salmonella spp. isolates were isolated from food samples in China during 2021-2023. One of 10 S . Rissen isolates, SM2301, carrying tet (X4) conferred high-level resistance to TGC (minimum inhibitory concentration > 8 µg/mL). The tet (X4) could be conjugated into different recipients, including E. coli , S. enteritidis , and K. pneumoniae isolates. Plasmid curing confirmed that tet (X4) was plasmid-mediated. Genetic analysis revealed that the tet (X4) in the SM2301 isolate was located in the IncFIA(HI1)-IncHI1A-IncHI1B(R27) hybrid plasmid, and the structure of tet (X4) was abh - tet (X4)-IS CR2 . To the best of our knowledge, this is the first report of a tet (X4)-positive food-derived S. Rissen isolate. The extending bacterial species of tet (X4)-bearing plasmids suggested the increasing transmission risk of the mobile TGC resistance gene tet (X4) beyond E. coli . This study highlights the emerging and evolution risk of novel resistance genes across various bacterial species. Therefore, further surveillance is warranted to monitor the prevalence of tet (X4) in Salmonella spp. and other bacterial species.