High Mixing Ratios Research Articles

Spatial distribution pattern and long-term trend of atmospheric methane in the Atlantic-Mediterranean transition region based on TROPOMI and GOSAT measurements.

Methane (CH4) spatial distribution and its trends in the Atlantic-Mediterranean transition region of southwestern Europe were studied using TROPOMI and GOSAT observations. TROPOMI XCH4 provided insights into the distribution across the entire Iberian Peninsula, highlighting the high XCH4 mixing ratios in the two main valleys and the southern sub-plateau, characterized by agricultural and livestock activities. The marine-continental region in the southwestern Iberian Peninsula was identified as a major CH4 hot spot. Focusing on this region, the seasonal distribution of CH4 and its trends were studied. The lowest XCH4 levels were recorded in a semi-natural landscape in a mountain range with an average mixing ratio of 1871.9±18.5nmolmol-1, while the highest trend was recorded at 10.9±0.7nmolmol-1year-1 for the period 2019-2023. Conversely, the highest XCH4 levels were obtained over an inland wetland, averaging 1888.7±15.8nmolmol-1; while recording the lowest regional trend, 6.4±0.9nmolmol-1year-1. Aiming to identify potential regional changes in the XCH4 trend, GOSAT observations were used, revealing a long-term trend of 8.7±0.3nmolmol-1year-1 from 2009 to 2023. Focusing on the first and last five years of the series, trends of 6.5±0.9nmolmol-1year-1 and 14.9±1.2nmolmol-1year-1 were detected, indicating a trend acceleration ratio of 2.3. An analogous pattern was found in the Atlantic Ocean and central Mediterranean at the same latitude, with ratios of 2.7 and 2.4 respectively. Furthermore, these outcomes were corroborated by ground-based observations from the Azores and Lampedusa stations, which belong to the NOAA network. Despite CH4 increasing globally and its trend accelerating, this work highlights the complexity of its dynamics, with regional variations in its mixing ratios, horizontal distribution, and temporal trends.

Influence of sewage effluent discharge on putative pathogen community in drinking water sources: insights from full-length 16S rRNA gene amplicon sequencing

ABSTRACT The discharge of sewage effluent is a major source of microbial contamination in drinking water sources, necessitating a comprehensive investigation of its impact on pathogenic bacterial communities. This study utilized full-length 16S rRNA gene amplicon sequencing to identify putative pathogenic bacteria and analyze their community structures in drinking water sources subjected to different levels of fecal pollution: urban rivers with low, moderate, and high sewage effluent mixing ratios, and mountain streams with minimal human impact. The sewage effluent itself was also analyzed. Mountain streams primarily harbored environmental pathogens, whereas urban rivers exhibited significantly higher concentrations of fecal indicator bacteria (FIB) (i.e., Escherichia coli and Clostridium perfringens) along with markedly more diverse enteric pathogens with a higher relative abundance. Furthermore, within urban rivers, the putative pathogen communities displayed significant variation, closely aligning with the sewage effluent mixing ratios. The effectiveness of FIBs as indicators of enteric pathogens was found to be largely dependent on the levels of fecal pollution. This study offers novel insights into the impact of sewage effluent discharge on putative pathogenic bacterial communities with enhanced species-level resolution.

New particle formation from isoprene under upper-tropospheric conditions

Aircraft observations have revealed ubiquitous new particle formation in the tropical upper troposphere over the Amazon1,2 and the Atlantic and Pacific oceans3,4. Although the vapours involved remain unknown, recent satellite observations have revealed surprisingly high night-time isoprene mixing ratios of up to 1 part per billion by volume (ppbv) in the tropical upper troposphere5. Here, in experiments performed with the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we report new particle formation initiated by the reaction of hydroxyl radicals with isoprene at upper-tropospheric temperatures of −30 °C and −50 °C. We find that isoprene-oxygenated organic molecules (IP-OOM) nucleate at concentrations found in the upper troposphere, without requiring any more vapours. Moreover, the nucleation rates are enhanced 100-fold by extremely low concentrations of sulfuric acid or iodine oxoacids above 105 cm−3, reaching rates around 30 cm−3 s−1 at acid concentrations of 106 cm−3. Our measurements show that nucleation involves sequential addition of IP-OOM, together with zero or one acid molecule in the embryonic molecular clusters. IP-OOM also drive rapid particle growth at 3–60 nm h−1. We find that rapid nucleation and growth rates persist in the presence of NOx at upper-tropospheric concentrations from lightning. Our laboratory measurements show that isoprene emitted by rainforests may drive rapid new particle formation in extensive regions of the tropical upper troposphere1,2, resulting in tens of thousands of particles per cubic centimetre.

Atmospheric CO2 column concentration over Iran: Emissions, GOSAT satellite observations, and WRF-GHG model simulations

Regarding global warming and climate change, carbon dioxide (CO2) is one of the most important greenhouse gases. Simulating CO2 gas at hourly/weekly time intervals and desired vertical resolution is challenging due to the coarse horizontal resolution of global models. In this study, both column-averaged CO2 mixing ratio (XCO2) and vertical cross sections of CO2 mixing ratio were simulated by the Weather Research and Forecast Green House gas (WRF-GHG) model at spatial resolutions of 30 and 10 km for the Middle East region as the first domain, and Iran as the second domain. Simulations consider the primary CO2 sources (anthropogenic, biogenic, fire, and oceanic) and the Copernicus Atmosphere Monitoring Service (CAMS) dataset. XCO2 retrieved from GOSAT satellite observations was employed to evaluate the simulation results of the column-averaged CO2 concentrations in February and August 2010. The evaluations showed that the spatiotemporal variability of meteorological variables was well simulated by WRF-GHG with correlation coefficients r of 0.86–0.92, 0.67–0.75, and 0.76–0.82 for temperature, wind, and relative humidity, respectively, during February and August 2010. The evaluations also indicated that the WRF-GHG simulations outperformed the global model TM3, with mean bias error values of − 0.79 and 0.45 PPMV for WRF-GHG in February and August, respectively. The percentage contribution of net CO2 emissions from human activities in Iran was calculated as (38.33 % and 23.70 %) of the total emissions, respectively, with values of 4.4 and 0.85 kg/km2 in each month. The net emissions contributions of biogenic, fire, and oceanic sources were evaluated in February and August, with biogenic emissions contributing (31.901 % and 27.66 %), biogenic absorption contributing (24.07 % and 46.63 %), fire emissions contributing (5.7 % and 2.064 %), and oceanic emissions contributing (3.23 × 10−6 % and 2.23 × 10−6 %). Large-scale circulations and biogenic activity are responsible for the major features of the spatial and seasonal distribution of CO2 in the area. In February, column mixing ratios are higher in more northern latitudes; in August, they are higher to the south. Furthermore, the simulated vertical cross sections show high CO2 mixing ratios in the mid-lower troposphere and northerly/northeasterly advection in February; the vertical profile is inverted in August with high concentrations in the lower stratosphere associated with southwesterly advection. However, the interaction between the synoptic and sub-synoptic features with the topography determines the precise dispersion and distribution of CO2. Despite the negligible emissions in central and eastern Iran, these factors play an important role in the observed concentrations in February and August. In August, the areas between the 120-day low-level monsoon flow of Sistan in eastern Iran, and the westerlies over western/southwestern Iran and the Zagros Mountain range, interact with the heat-low in the Iranian plains and with the Arabian subtropical high. In February, the dominant winds in western Asia were west winds, with the main source of pollution coming from the northeastern regions flowing towards central and eastern Iran. The equatorward displacement of the polar jet stream and the passage of low-pressure systems from the west in winter cause a temporary reduction in CO2 concentrations.

Combined Impacts of Temperature, Sea Ice Coverage, and Mixing Ratios of Sea Spray and Dust on Cloud Phase Over the Arctic and Southern Oceans

AbstractWe analyze the importance of cloud top temperature, dust aerosol, sea salt aerosol, and sea ice cover for the thermodynamic phase of low‐level, mid‐level, and mid to low‐level clouds observed by CloudSat/CALIPSO over the Arctic and the Southern Ocean using an explainable machine learning technique. As expected, the cloud top temperature is found to be the most important parameter for determining cloud phase. The results show also a predictive power of sea salt and sea ice on the phase of low‐level clouds, while in mid‐level clouds dust shows predictive power. Over the Southern Ocean, strong zonal winds coincide with the aerosol distribution. While they can produce high mixing ratios of sea spray at lower levels, the strong zonal winds may prevent the pole‐ward transport of dust. Sea ice may prevent the release of sea salt aerosols and marine organic aerosols leading to higher liquid fractions in clouds over sea ice.

Numerical investigation of CH4/H2/air micro-mixing combustion flow in a micro gas turbine combustor with different head-end structures

In order to investigate the premixed combustion characteristics of CH4/H2/air in a micro-mixing combustor, the effects of different micro-mixing head-ends (HE1, HE2, HE3) and hydrogen mixing ratios on the temperature distribution, heat transfer process, emission characteristic, flames shape are analyzed. The results show that compared with swirl head-end combustion, the micro-mixing combustion performance is better. Among the three head-ends, HE3 has the best combustion characteristics and stable flames. The temperature distribution in the high-temperature zone is uniform, and low-temperature zone is concentrated near the jet, which can suppress the flashback. The velocity and temperature gradient near the central axis of jet streams show a strong synergistic effect. The flames are plume shaped and flames stability is mainly influenced by the H2 combustion process. Increasing the jet diameter, decreasing the jet spacing and increasing the hydrogen mixing ratio all contribute to the flames stability, but these three methods can stabilize the flames by affecting fluid Reynolds number, interaction between small flames and combustion rate, respectively. Moreover, small jet diameter and high hydrogen mixing ratio can reduce OTDF, which contributes to improve outlet temperature uniformity.

Modification of Microphysical Parameterization Schemes and Their Application in the Simulation of an Extremely Heavy Rainfall Event in Zhengzhou

AbstractIn the present study, the Morrison and Thompson microphysics schemes in the Weather Research and Forecasting model were improved and used to simulate a record‐breaking heavy rainfall event occurred in Henan Province over central China during 19–21 July 2021. In the modified schemes, the terminal velocity of graupel and initial cloud droplet concentration were adjusted based on sensitivity tests. Results showed that the modified Morrison scheme (MORR_MOD) better captured the spatial distribution and temporal evolution of precipitation than the original scheme (MORR). Specifically, it produced a 40‐hr cumulative rainfall amount of 963 mm and an extreme hourly rainfall rate of 157.7 mm, which were closer to observations than MORR. Analysis of the dynamic and microphysical structures of the extreme‐rain‐producing convective clusters revealed that MORR_MOD predicted stronger updrafts, higher rain mass content and larger mean mass diameter of raindrops than MORR. By analyzing the tendencies of rain mass and number concentration, it was found that MORR_MOD predicted stronger accretion rates of cloud droplets by rain and weaker auto‐conversion rates of cloud droplets than MORR, which contributed to the high rain mixing ratio and low number concentration, respectively. In addition, MORR_MOD predicted stronger diabatic heating rates than MORR, which were primarily attributed to stronger condensation of water vapor, and may have been the reason why MORR_MOD simulated stronger updrafts.

Measurements and Modeling of the Interhemispheric Differences of Atmospheric Chlorinated Very Short‐Lived Substances

AbstractChlorinated very short‐lived substances (Cl‐VSLS) are ubiquitous in the troposphere and can contribute to the stratospheric chlorine budget. In this study, we present measurements of atmospheric dichloromethane (CH2Cl2), tetrachloroethene (C2Cl4), chloroform (CHCl3), and 1,2‐dichloroethane (1,2‐DCA) obtained during the National Aeronautics and Space Administration (NASA) Atmospheric Tomography (ATom) global‐scale aircraft mission (2016–2018), and use the Community Earth System Model (CESM) updated with recent chlorine chemistry to further investigate their global tropospheric distribution. The measured global average Cl‐VSLS mixing ratios, from 0.2 to 13 km altitude, were 46.6 ppt (CH2Cl2), 9.6 ppt (CHCl3), 7.8 ppt (1,2‐DCA), and 0.84 ppt (C2Cl4) measured by the NSF NCAR Trace Organic Analyzer (TOGA) during ATom. Both measurements and model show distinct hemispheric gradients with the mean measured Northern to Southern Hemisphere (NH/SH) ratio of 2 or greater for all four Cl‐VSLS. In addition, the TOGA profiles over the NH mid‐latitudes showed general enhancements in the Pacific basin compared to the Atlantic basin, with up to ∼18 ppt difference for CH2Cl2 in the mid troposphere. We tagged regional source emissions of CH2Cl2 and C2Cl4 in the model and found that Asian emissions dominate the global distributions of these species both at the surface (950 hPa) and at high altitudes (150 hPa). Overall, our results confirm relatively high mixing ratios of Cl‐VSLS in the UTLS region and show that the CESM model does a reasonable job of simulating their global abundance but we also note the uncertainties with Cl‐VSLS emissions and active chlorine sources in the model. These findings will be used to validate future emission inventories and to investigate the fast convective transport of Cl‐VSLS to the UTLS region and their impact on stratospheric ozone.

Different VOC species derived from fugitive emissions at various altitudes around petrochemical plant

Volatile organic compounds (VOCs) emitted from fugitive sources are crucial for environmental and health risk assessments. However, monitoring these emissions at ground level, according to traditional technical specifications, has made it challenging to identify polluted air masses and collect purposeful samples. In this study, we focused on utilizing an unmanned aerial vehicle system to obtain air samples around a petrochemical industrial park. We conducted a quantitative analysis of 108 VOC species and compared the results between aerial and ground-level samples. The findings indicated a higher presence of reactive compounds in the aerial samples. The sample pairs exhibited relatively homogeneous compositions of hydrocarbons with fewer than eight carbon atoms, suggesting a well-mixed condition for light compounds. Conversely, the aerial samples exclusively exhibited high mixing ratios of C8–C15 compounds, including branched paraffins and aldehydes. Based on the quantified VOCs, we evaluated the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP). The results highlighted aldehydes, alkenes, and aromatics, particularly propanal, 2-butene, m/p-xylene, and benzaldehyde, as priority control compounds. Additionally, the semiquantitative concentrations of these non-quantitative C8–C15 species ranged from 1 to 15 ppbv, with a total content exceeding 150 ppbv, it indicated the significant contribution to ambient secondary pollution. These results provide valuable insights into the identification of potential emission sources and the assessment of environmental repercussions attributed to these intermediate-volatile organic compounds from fugitive emissions around petrochemical plant.

Emissions of Sulphur Dioxide (SO2) from Coal-Fired Power Plants in Serbia and Bosnia-Herzegovina: First Attempts of a Validation of TROPOMI Satellite Products with Airborne In Situ Measurements

The Western Balkan region is known for emitting alarmingly high sulphur dioxide amounts from coal-fired power plants. Though a number of environmental regulations have been introduced in recent years (e.g. desulphurisation installations, construction of modern power plants), the pollution burden is still much higher than recommended by the authorities. A number of different montoring systems are required to observe the growing pollution situation in the Western Balkan region, partly caused by a high energy demand from outside (e.g. Western Europe).Several of the top ten SO2 polluters in Europe are located in Bosnia-Herzegovina and Serbia. Here we present the first in situ measurements of sulphur dioxide in this region conducted with a German research aircraft in cooperation with local scientists in Bosnia-Herzegovina and Serbia. Two of the strongtest emitting coalfired power plants were selected for the measurements in autumn 2020: Tuzla in Bosnia-Herzegovina and Nikola Tesla in Serbia (Nikola Tesla). The measurements were mainly conducted in the boundary layer (below ~1 km altitude in winter). Downwind of the power plants, extremely high SO2 mixing ratios exceeding 100 parts per billion (ppb = nmol mol-1 ) were measured at a distance of ~20-40 km from the sources. The SO2 plumes from the power plants were trapped in well-defined inversion layers between ~500-1000 m altitude. The airborne measurements can be used to validate synchronous spaceborne SO2 measurements from the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5P satellite. A first intercomparison indicates some problems with dense smoke clouds frequently covering these countries in the winter months. However, it turned out that the Nikola Tesla flight is to some extent suited for a TROPOMI-SO2 validation, since it was obtained during cloud-free conditions with a well-defined vertical extension of the probed SO2 plume (needed to estimate the Vertical Column Density, VCD, measured by the satellite). In addition, these airborne measurements accompanied by model simulations can be used to determine the SO2 emission strength of the power plants and to compare it to the source strength reported by the power plant operators. The results indicate a reasonable agreement between the airborne measurements, model results, emission inventories, and satellite measurements for the Nikola Tesla power plants.

Characterization of the Spatial Distribution of the Thermodynamic Phase Within Mixed‐Phase Clouds Using Satellite Observations

AbstractModels assume that mixed‐phase clouds consist of uniformly mixed ice crystals and liquid cloud droplets when observations have shown that they consist of clusters, or “pockets,” of ice crystals and liquid cloud droplets. We characterize the spatial distribution of cloud phase over the Arctic and the Southern Ocean using active satellite observations and determine the relative importance of collocated meteorological parameters and aerosols from reanalysis to predict how uniformly mixed mixed‐phase clouds are for the first time. We performed a multi‐linear regression fit to the data set to predict the spatial distribution of the ice and liquid pockets. Contrary to what models suggest, mixed‐phase clouds are rarely perfectly homogeneous. Our results suggest that high temperatures are associated with homogeneously mixed ice and liquid pockets. We also find that a high mixing ratio of black carbon is associated with heterogeneously mixed ice and liquid pockets.

Experimental Investigation of Diesel-WCOB Engine Performance with A Small Proportion of Ethanol/Isobutanol as A Fuel Additive

The globe is beginning to face fast-expanding global warming concerns that require immediate treatment. Biodiesel can be considered the most widely used and versatile sustainable fuel for a variety of uses. Because it is biodegradable, environmentally friendly, and renewable, it offers a viable solution to the looming energy crisis. Waste cooking oil is among the locally available sources that might be utilized as an extra source in different countries at a reasonable cost. Combining used cooking oil and diesel is a viable option for diesel engines because it has been certified for use at blending ratios as low as 20% as a commercial fuel. However, when it comes to fuel additives, the best alternative is to use waste cooking oil at high mixing ratios with diesel to power diesel engines. The goal of this research is to examine the various performance parameters of a diesel engine and the characteristics of biodiesel blended fuels by measuring the specific fuel consumption of the brakes and the thermal efficiency of the brakes and to investigate the impact of isobutane and ethanol additions at rates of 5% and 10% on the properties of the fuel and engine efficiency to enhance the specifications of the blended fuel in high proportions B40. Mixed fuel B40 with 10% ethanol (B40E10) can be used as a highly mixed fuel to enhance diesel engine performance. The density, kinematic viscosity, and flash point of diesel fuel were the lowest and rise with the amount of WCOB in the mixture, while the blended fuel B40 had the greatest value and improved with the percentage of additives. Increases in the proportion of additives also result in a visible rise in the braking force and fuel consumption.

Entropy generation rate analysis of turbocharger radial flow compressor in range from surge to choke

This study compares the local losses of a radial compressor in the range from surge to choke considering shock phenomena, boundary layer separation, and mixing mechanisms. For this purpose, formulation of the local entropy generation rate (EGR) is added to the computational fluid dynamics (CFD) solver, which models the turbulent flow field of the compressor through the RANS approach. For validation, the numerical pressure rise curve of the compressor is compared with the experimental data. The results indicate that at the design point, the impeller, diffuser, and the volute account for approximately 50.8%, 30.0%, and 12.3% of the EGR, respectively, with approximately 5% in the impeller backspace, 1% in the diffuser cavity, and less than 0.5% in the inlet duct. Approaching the surge condition, local losses due to mixing and shock waves decline while boundary layer losses increase. Based on comprehensive analysis of the leading-edge boundary layer, the largest dead-air zone is found at the design point, resulting in a lower diffusion entrance loss and a higher mixing loss. Furthermore, the EGR variation in the diffuser channel is investigated by shedding light on mixing dynamics and classification of the channel flow regime into three different zones based on mixing ratio (MR). The outcomes show that the flow regime tends to mix more quickly at a higher MR, resulting in a slight decrease in EGR, which benefits compressor performance. We demonstrate that the mixing rate of flow regimes decreases in both the leading-edge boundary layer and the radial diffuser approaching the surge margin.

Chemical reaction analysis of auto-ignition behavior for mixed fuel of cyclopentane and paraffin

Knocking due to auto-ignition of fuel greatly hinders the performance enhancement of gasoline engines. Since general gasoline is a mixture of many substances, its knock resistance depends largely on the combination of substances contained. Therefore, it is important to comprehend the chemical reaction process up to ignition in mixed fuels. This study performed various analyses of the detailed chemical reaction process for the case where cyclopentane, a representative of naphthene, is mixed with paraffin. The main purpose of this analysis is to discover a mechanism that enhances the antiknock effect by combining fuels. Analysis of the detailed reaction process suggests that in some cases cyclopentane suppresses the subsequent reactions by consuming the OH produced by paraffin during the initial low temperature oxidation. Therefore, mixing cyclopentane into paraffin greatly extends the ignition delay time by suppressing the subsequent exothermic reactions. When added in a low fraction, the ignition suppression effect exceeds that of the general octane booster toluene. On the other hand, analysis of the detailed reaction process under high mixing ratio conditions showed that cyclopentane has an ignition promotion effect. The reason for this phenomenon is that cyclopentane lowers the ignition temperature because it accumulates a large amount of H2O2 as an intermediate product after the initial reactions. Furthermore, H2O2 advances the ignition reactions by generating OH in the subsequent reactions. Additionally, due to the changing behavior of the low-temperature oxidation reaction, the effect of cyclopentane mixing also changes with the temperature range. In other words, cyclopentane has the opposing effects of suppressing and promoting ignition, which results in a complicated phenomenon that changes depending on the mixing ratio with paraffin and temperature.

Evolution of Earth's oxygen, nitrogen, and carbon polar outflow in the Archean eon

The habitability of Earth significantly depends on the evolution of its atmospheric properties, which are strongly influenced by escape processes. Polar outflow, which encompasses the atmospheric escape of ions through the open field lines of the Earth's magnetosphere, is the dominant escape process for modern Earth and likely played a significant role in Earth's early history as well. In this article, we investigate the evolution of Earth's polar outflow during the Archean eon 3-4 gigayears (Ga) ago for an N2-CO2 atmosphere. For this, we use a kinetic direct simulation Monte Carlo (DSMC) particle code to simulate the interactions between the solar wind and the Earth's upper atmosphere. We explore the effects of different CO2 mixing ratios (10%, 25%, 50%, 75%, 99%) on the polar outflow escape rates of oxygen, nitrogen and carbon. Using the ion production rates as an estimate for polar outflow, our results indicate that during the time 3.6-4.0 Ga ago, a CO2 mixing ratio larger than 25% may have been necessary to avoid excessive escape via polar outflow. Close to 4 Ga ago, even 50% CO2 may have been necessary due to the stronger solar winds. Our results align with other studies also suggesting a similarly high CO2 mixing ratio in the early Archean.

Carbon-bearing Molecules in a Possible Hycean Atmosphere

The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet–star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H2-rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9–5.2 μm range. The spectrum reveals strong detections of methane (CH4) and carbon dioxide (CO2) at 5σ and 3σ confidence, respectively, with high volume mixing ratios of ∼1% each in a H2-rich atmosphere. The abundant CH4 and CO2, along with the nondetection of ammonia (NH3), are consistent with chemical predictions for an ocean under a temperate H2-rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.

Optimisation of Bioflocculation Using Anabaena sp. and Navicula sp. for Harvesting of Glagah Microalgae Consortium

One of the problems in microalgae is harvesting. Currently, many chemical methods are used that impact the environment. Not all of them can be used as a filter, so bioflocculation is used because there is no need to change the medium. This method is an environmentally friendly and efficient alternative to chemical flocculants that usually cause contamination of biomass and health. Previous studies have shown that different ratios of auto-flocculated microalgae in cocultures affect the flocculation rate. This research was carried out by the Glagah Consortium bioflocculation using Anabaena sp. and Navicula sp., which had never been done before. The study aims to study the effect of the mixing ratio on the flocculation rate, carbohydrates, and lipid content of the Glagah Consortium. The consortium uses Anabaena sp. and Navicula sp. as bioflocculants. Glagah and Anabaena sp. consortium was cultured in Bold Basal Medium, while Navicula sp. was cultured in F/2 medium. Cell density was measured every 24 hr for 8 days with a hemocytometer. The cultures were harvested in the stationary phase, then mixed between non-flocculated microalgae (Glagah Consortium) and flocculated microalgae (Anabaena sp., Navicula sp.) in a ratio of 1:1, 1:0.5, and 1:0.25 for 24 hr. Bioflocculation was measured by spectrophotometer at 750 nm 0 and 24 hr after mixing. Carbohydrate levels were measured using the phenol sulfuric acid method, while lipid measurements were performed using the Bligh and Dyer method. The addition of Anabaena sp. and Navicula sp. as bioflocculant in Glagah Consortium culture results in an increase in flocculation rate with an effective ratio of 1:0.25 for Anabaena sp. (81%) and 1:1 for Navicula sp. (95%). Mixing of Anabaena sp. and Glagah Consortium results in carbon source competition, reducing carbohydrate content at higher mixing ratios (0.172, 0.364, and 0.500 mg/ml on 1, 1:0.5, and 1:0.25) while increasing lipid content as a result of lipid production in stationary phase (highest on ratio 1:1 = 0.011 mg/ml). Navicula sp. and Glagah Consortium mixture caused no significant changes to carbohydrate content but showed an increased amount of lipid at all ratios as a result of osmotic stress on Glagah Consortium from saline F/2 medium (highest on ratio 1:1 = 0.162 mg/ml).

Measurement report: Assessment of Asian emissions of ethane and propane with a chemistry transport model based on observations from the island of Hateruma

Abstract. The island of Hateruma is the southernmost inhabited island of Japan. Here we interpret observations of ethane (C2H6) and propane (C3H8) together with carbon monoxide (CO), nitrogen oxides (NOx and NOy) and ozone (O3) carried out in the island in 2018 with the GEOS-Chem atmospheric chemistry transport model. We simulated the mixing ratios of these species within a nested grid centred over the site, with a model resolution of 0.5∘ × 0.625∘. We use the Community Emissions Data System (CEDS) dataset for anthropogenic emissions and add a geological source of C2H6 and C3H8. The model captured the seasonality of primary pollutants (CO, C2H6, C3H8) at the site – high mixing ratios in the winter months when oxidation rates are low and flow is from the north and low mixing ratios in the summer months when oxidation rates are higher and flow is from the south. It also simulates many of the synoptic-scale events with Pearson's correlation coefficients (r) of 0.74, 0.88 and 0.89 for CO, C2H6 and C3H8, respectively. Mixing ratios of CO are simulated well by the model (slope of the linear fit between model results and measurements is 0.91), but simulated mixing ratios of C2H6 and C3H8 are significantly lower than the observations (slopes of the linear fit between model results and measurements are 0.57 and 0.41, respectively), most noticeably in the winter months. Simulated NOx mixing ratios were underestimated, but NOy appears to be overestimated. The mixing ratio of O3 is moderately well simulated (slope of the linear fit between model results and observations is 0.76, with an r of 0.87), but there is a tendency to underestimate mixing ratios in the winter months. By switching off the model's biomass burning emissions we show that during winter, biomass burning has limited influence on the mixing ratios of compounds but can represent a more sizeable fraction in the summer. We also show that increasing the anthropogenic emissions of C2H6 and C3H8 within the domain by factors of 2.22 and 3.17 increases the model's ability to simulate these species in the winter months, consistent with previous studies.

Methodological advances to improve repeatability of SOA generation in environmental chambers

Most laboratory atmospheric chamber studies probing the chemical and physical properties of secondary organic aerosol (SOA) perform such experiments with mixing ratios of volatile organic compounds (VOCs) above atmospheric relevance (≳50 ppbv). When performing ozonolysis of biogenic VOCs at mixing ratios of atmospheric relevance (≲10 ppbv), a major hinderance on the repeatability of replicate experiments is due to the limitations of conventional VOC injection techniques. To overcome these limitations, two novel components (stop/flow and split valves) were embedded in a conventional VOC injection setup, thereby permitting the use of higher VOC volumes of injection to attain low VOC mixing ratios, and the delivery of the VOC to the environmental chamber as a short, discrete pulse for subsequent reaction. Implementation of these novel VOC injection components has resulted in improvements in variability between replicate chamber experiments of up to a factor of 7 with respect to particle number, mass, and size distributions at both high and low VOC mixing ratios (50 and 10 ppbv, respectively). These improvements permit extension of quantitative measurements of SOA formation to VOC mixing ratios at or near atmospheric levels, where new particle formation (NPF) and SOA mass loading are typically within experimental variability.

Rapid and visual detection of specific bacteria for saliva and vaginal fluid identification with the lateral flow dipstick strategy.

Identification of body fluids is critical for crime scene reconstruction, and a source of investigation source of investigative leads. In recent years, microbial DNA analysis using sequencing and quantitative real-time polymerase chain reaction have been used to identify body fluids. However, these techniques are time-consuming, expensive, and require complex workflows. In this study, a new method for simultaneous detection of Streptococcus salivarius and Lactobacillus crispatus using polymerase chain reaction (PCR) in combination with a lateral flow dipstick (LFD) was developed to identify saliva and vaginal fluid in forensic samples. LFD results can be observed with the naked eye within 3min with a sensitivity of 0.001ng/µL DNA. The PCR-LFD assay was successfully used to detect S. salivarius and L. crispatus in saliva and vaginal fluid respectively, and showed negative results in blood, semen, nasal fluid, and skin. Moreover, saliva and vaginal fluid were detectable even at an extremely high mixing ratio of sample DNA (1:999). Saliva and vaginal fluid were identified in various mock forensic samples. These results indicate that saliva and vaginal fluid can be effectively detected by identifying S. salivarius and L. crispatus, respectively. Furthermore, we have shown that DNA samples used to identify saliva and vaginal fluid can also provide a complete short tandem repeat (STR) profile when used as source material for forensic STR profiling. In summary, our results suggest that PCR-LFD is a promising assay for rapid, simple, reliable, and efficient identification of body fluids.