Typical Site Research Articles

Urban ventilation assessment with improved vertical wind profile in high-density cities – Comparisons between LiDAR and conventional methods

The vertical wind speed profile is crucial to urban ventilation assessment and urban planning/design. This study uses Light Detection and Ranging (LiDAR) observation as benchmark to evaluate accuracy of wind profiles estimated by conventional methods. The conventional methods include Boundary Layer Wind Tunnel (BLWT), Regional Atmospheric Modeling System (RAMS), Power Law (PL), and Weather Research and Forecasting (WRF). The evaluation involves two typical urban sites with different densities under summer weak-wind conditions. Large Eddie Simulations (LES) are conducted to further investigate the sensitivity of urban ventilation assessment results to the deviations of wind profiles. The results indicate significant deviations in LES caused by conventional methods. The largest deviations of wind velocity ratio are found in mesoscale meteorological models (RAMS and WRF (>65%)). Deviations caused by physical and empirical models are smaller but still significant (BLWT (>25%) and PL (>40%)). Consequently, large deviations (>100%) of wind-relevant criterion for outdoor thermal comfort are observed. Finally, to balance accuracy and data availability, we recommend power law method as the optimal method to provide inflow boundary condition for numerical simulations when LiDAR observation is not available. We provide new and valuable understandings to improve urban ventilation assessment in high-density cities.

Implantation of two generations of Bonebridge after mastoid obliteration with bioactive glass S53P4

PurposeAfter radical surgery for chronic cholesteatoma (CWD mastoidectomy), patients have the option to have the posterior wall of their external auditory canal surgically reconstructed with S53P4 bioactive glass. The procedure eliminates some of the restrictions related to having a postoperative cavity and extends the options for a hearing prosthesis. If classic reconstruction is not possible and a hearing aid is not used, we suggest use of a Bonebridge implant. MethodsThis study describes, over 18 months of follow-up, 16 patients after a two-stage surgical procedure: obliteration of the mastoid cavity with bioactive glass followed by Bonebridge implantation. There were 7 patients who received the first generation implant (BCI 601) and 9 who used the second (BCI 602). Before and after implantation, pure tone audiometry, sound field thresholds, and free-field audiometry were performed. Speech reception thresholds in noise were assessed using the Polish Sentence Matrix Test. Subjective assessment of benefits was done using the APHAB (Abbreviated Profile of Hearing Aid Benefit) questionnaire. ResultsDuring the observation period, no serious complications were found. The study demonstrated the safety and validity of the procedures and confirmed the safety of using S53P4 bioactive glass in otosurgery (antibacterial effect, nonrecurrence of cholesteatoma, and no effect on the inner ear). The audiological benefits expected from using the Bonebridge implant processor were also confirmed. ConclusionIt is concluded that, after reconstructing the posterior wall of the external auditory canal with bioactive glass, two-stage implantation of a Bonebridge implant in a typical site is a safe solution for patients who have difficult anatomical conditions following their CWD mastoidectomy.

Field test and numerical reconstitution of natural winds at the tunnel entrance section of high-speed railway

PurposeThe purpose of this paper is to understand the natural wind field characteristics of the tunnel entrance section and analyzing the aerodynamic performance of high-speed railway trains (HSRTs) under natural winds.Design/methodology/approachThree typical tunnel entrance section sites, namely, tunnel–bridge in a dry canyon (TBDC), tunnel–bridge in a river canyon (TBRC) and tunnel–flat ground (TF), are selected to conduct a continuous wind field measurement. Based on the measured wind characteristics, the natural winds of the TBDC and TF sites are reconstituted and imported into the two corresponding full-scale computational fluid dynamics models. The aerodynamic loads of the HSRT running on TBDC and TF with reconstituted winds are simply analyzed.FindingsThe von Kármán spectrum can be used to describe the wind field at the tunnel entrance section. In the reconstituted natural wind condition, a time-varying feature of wind speed distribution and leeward side vortex around the HSRT caused by the wind speed fluctuation is found. The fluctuating amplitude of aerodynamic loads at the TBDC infrastructure is up to 97.9% larger than that at the TF infrastructure.Originality/valueThe natural wind characteristics at tunnel entrance sections on the high-speed railway are first measured and analyzed. A numerical reconstitution scheme considering the temporal and spatial variation of natural wind speed is proposed and verified based on field measurement results. The aerodynamic performance of an HSRT under reconstituted natural winds is first investigated.

A comprehensive carbon dioxide reduction framework for industrial site using pinch analysis tools with a fuel cell configuration

Removing anthropogenic carbon dioxide emissions from existing industrial sites is essential to slow down climate change. A multipronged approach is required to reduce the carbon dioxide footprint of an existing industrial site by including carbon dioxide capture and utilisation, industrial symbiosis, heat integration and the introduction of renewable power sources. This work extends the current systematic framework for low carbon dioxide industrial site planning by proposing an alternative carbon dioxide lowering sequential framework for existing high carbon dioxide footprint industrial sites. The sequential framework will set out a four-step process using a suite of optimisation tools to guide industrial site managers to lower the carbon dioxide footprint of an existing industrial site that also features a fuel cell configuration. The framework includes a baseline study to analyse the current carbon dioxide footprint of the industrial site. The study then proposes a carbon capture and utilisation step to collate the carbon dioxide captured for chemical mineralisation for in-situ utilisation. The inclusion of the Direct Methanol Fuel Cell configuration is important to the site because it generates clean carbon-neutral power to the hybrid power system while utilising methanol, a carbon dioxide mineralised product. The following steps involve using Pinch Analysis tools to optimise the energy usage and renewable power usage within the industrial site. The energy produced at the site would be integrated to reduce external utilities required by using the Total Sites Heat Integration technique. The Power Pinch Analysis technique optimises power distribution from the hybrid power system hub. The illustrative case study is a typical industrial site in the Western Cape province in South Africa. It was determined that a potential 105 ton/day of carbon dioxide could be captured from the flue gas from industries on the site. The overall heat utility saving of 79.95% of the hot utility requirements for the participating industries in the site. It was also determined that the renewable sources of power which incorporated the fuel cell configuration would be sufficient to provide carbon-neutral power to the industrial site. The rate of return on the investment of the hybrid power system is found to be 20.68%. The carbon dioxide lowering framework for existing industrial sites could provide a sustainable, impactful guide for site planners to assist the country's commitment to limit greenhouse gas emissions.

Influence of Pile-Soil Interaction on Dynamic Properties and Response of Offshore Wind Turbine with Monopile Foundation in Sand Site

In this study, a sophisticated 3D finite element model of NREL 5MW wind turbine (WT) superstructure is developed using Abaqus, which includes necessary functional features, such as rotor rotation, drivetrain, pitch, servo-control, etc. A multi-step validation process has been conducted in order to verify the reliability of the blade, the Rotor-Nacelle Assembly (RNA) and the entire WT model. In the time domain, a software framework of ABA-OWT is developed for the dynamic analysis of offshore wind turbine (OWT) based on the Abaqus WT structure model and FAST submodules. The framework is capable of computing wind loads, wave loads, and servo-control commands in a fully coupled way. The pile-soil interaction (PSI) is modeled by nonlinear p-y, t-z and Q-z springs and the dashpots parallel with them. A typical sandy site is considered, while several identical analyses are performed for both numerical models including fixed base and PSI. After calculating the eigenvalues of the WT structure and analyzing its dynamic response to the combined action of wind and wave, three representative wind-wave load cases are chosen for subsequent seismic response study. The important conclusions are as follows. Firstly, the PSI reduces the natural frequencies of FA1, SS1 and FA2 by about 12% and SS2 by 23.5%. Secondly, under the combined action of wind and wave, the PSI significantly increases the tower-top peak motion responses in normal operating cases, but its influence on the mudline peak internal force responses is almost negligible; For parking cases, the PSI dramatically enlarges the peaks of the tower-top motion responses and the mudline bending moment, and the effect of PSI on the structural peak responses in parking cases is greater than that in normal operating cases. Finally, under the conjoint action of wind, wave and seismic, the PSI increases the tower-top peak motion responses and reduce the mudline peak internal force responses, and because of the aeroelastic effects, the influence of PSI on the structural peak responses in normal operating cases is always the smallest. In a word, the PSI has a remarkable impact on the natural frequency, dynamic response and seismic response of offshore wind turbine (OWT) with monopile foundation, which should be considered in a reasonable way in the practical offshore wind power project.

Antibiotic resistance genes in aerosols: a review

Recently, drug resistance resulted from the extensive abuse and over-use of antibiotics has posed a great threat to human health. Scholars have conducted numerous studies on the impacts of antibiotic resistant bacteria and antibiotic resistance genes (ARGs) in different types of environments. Aerosol is not only a potential reservoir for ARGs, but also an important route for transmission of ARGs in the environment. However, a systematic summary of its sources, transmission, human exposure, and health risks is lacking. This review focused on four types of typical sites for aerosol research: human functional living places, farms, urban wastewater treatment plants, and hospitals. The sources, transmission routes, human exposure, and health risks of ARGs in the aerosol of these four typical sites were reviewed. This article also provides a reference for prevention and control of ARGs in aerosols.

Complex mixture toxicology: Evaluation of toxicity to freshwater aquatic receptors from biodegradation metabolites in groundwater at a crude oil release site, recent analogous results from other authors, and implications for risk management

Aquatic toxicity posed by the complex mixture of biodegradation metabolites and related oxygen-containing organic compounds (OCOCs) in groundwater at typical petroleum release sites is of concern to regulatory agencies; several are using results from laboratory studies in older literature that are not appropriate analogs for risk management. Recent field studies from typical sites and natural groundwater should be utilized. In this study, OCOCs downgradient of the biodegrading crude oil release at the USGS Bemidji site were tested for freshwater aquatic toxicity using unaltered whole groundwater samples. This type of testing is optimal because the entire mixture of OCOCs present is tested directly and assessment is not affected by analytical limitations. Ceriodaphnia dubia and Pimephales promelas were tested for toxicity using USEPA Methods 1002 and 1000, which estimate chronic toxicity. OCOCs in representative samples up to the maximum concentration tested of 1710 ug/L Total Petroleum Hydrocarbons (TPH) (nC10 to nC40; without silica gel cleanup) did not result in effects relative to the lab control for C. dubia survival, or for P. promelas survival or growth; and did not result in effects above background for C. dubia reproduction. This is consistent with findings using the same testing methods and species on samples from 14 biodegrading fuel release sites: OCOCs did not cause increased toxicity relative to background at a maximum tested concentration of 1800 ug/L TPH (nC10 to nC28). Based on their toxicity testing using the same species and USEPA methods on groundwater from a biodegrading diesel release site, Washington Department of Ecology recently set a freshwater screening level for OCOCs at 3000 ug/L TPH (“Weathered DRO”). These studies indicate that, in the absence of dissolved hydrocarbons, OCOCs in groundwater from typical biodegrading fuel or crude oil releases are not toxic to C. dubia or P. promelas at typical concentrations.

Tide-driven microplastics transport in an elongated semi-closed bay: A case study in Xiangshan Bay, China

Coastal bays are important containers for plastic wastes before they enter the ocean. Based on field samples, this study presents the main characteristics of microplastics and uses a numerical model to study the distribution and movement of microplastics as they are driven by tidal flows in an extended semi-closed bay in Xiangshan Bay, China. The laboratory analyses of microplastic samples from 27 pollutant source samples collected in three batches provided fundamental data on microplastics. Our results show that the local microplastics are prevalent (mean abundance: 890.6 ± 419.4 particles/m3) in the water. A higher quantity of fibre- and fragment-type microplastics was identified and compared to other plastic types. The detected microplastics varied in colour and composition. The simulation suggests that the bay can trap microplastics inside it, with only 16.92 % discharged into the open ocean. A series of single-source numerical tests at nine typical observation sites were conducted to examine tide-driven microplastic transport. Our results suggest that the release location is crucial to microplastic distribution. Specifically, the microplastics tended to accumulate near the bay mouth and the Tie inlet; the microplastics released from the north shore generally evacuated the bay more easily; and the inner harbour tended to accumulate microplastics during spring tide, as opposed to the departure of microplastics at the outer bay, while the effect was reversed during neap tide. We further considered the deposit effect, which significantly reduces the discharging rate to 0.04 % with a settling velocity of 0.05 mm/s. These results may have great importance to decision-making, management, and control of microplastic pollution.

Incorporating soil mercury species and fractions into multi-objective risk assessment of a residue disposal site in China.

Environmental problems in soil and water caused by solid waste dumps have become a growing concern. This study proposes an integrated risk assessment model aimed at multi-objectives including human, ecology and groundwater and develops remediation target values at different tiers associated with soil mercury species and fractions in a typical residue disposal site of China. The results show that the residue disposal site was severely contaminated with mercury, with the maximum mercury content in the soil reaching 579.14mg/kg. The average concentration of vapour mercury, bioaccessible mercury, bioavailable mercury and leachable mercury tested in laboratory was 87.65mg/kg, 3.15mg/kg (intestinal phase), 1.654mg/kg and 0.045mg/L, respectively. The hazard index calculated using total mercury, bioaccessible mercury and vapour mercury was 7.43 E + 01, 4.42 E + 01, and the remediation target values were7.79mg/kg and 13.1mg/kg, respectively. The ecological risk for total mercury and bioavailable mercury was calculated using measured site soil mercury background values of 6390.92 and 94.52, and the remediation target was 0.7mg/kg and 47.33mg/kg, respectively. Under Class IV water conditions, the measured and three-phase equilibrium model simulations of leachable mercury resulted in remediation targets of 6mg/kg and 10mg/kg for soil mercury. Compared to total mercury, the remediation target values calculated using mercury species and fractions were significantly larger under human health protection, ecology protection and groundwater protection. This results in a reduction in the area of soil to be remediated by 20.3-85.7%, resulting in significant savings in remediation costs. It was concluded that when conducting risk assessment and reuse of mercury-contaminated sites, it is important to consider the species and fractions of mercury in the soil in order to reasonably determine the remediation criteria and scale of remediation to avoid over-remediation and incomplete remediation. At the same time, a comprehensive protection target remediation mechanism should be established by combining different receptors.

Dominant roles of torrential floods and atmospheric deposition revealed by quantitative source apportionment of potentially toxic elements in agricultural soils around a historical mercury mine, Southwest China

Hg pollution in soils surrounding the Wanshan mercury mine (WMM), once the largest Hg-producing center in China, has been confirmed, neglecting other potential toxic elements (PTEs). Better understanding of the sources and transport pathways of soil PTEs remains insufficient. To response these limitations, eight soil PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) at two typical agricultural sites, namely AZ and WW that are located near and far from the WMM, respectively, were systemically investigated. The results showed that AZ exhibited significantly higher concentrations of all the PTEs in the surface soil than WW (p < 0.01). Hg and Cd were recognized as the priority control PTEs, with their average concentrations of 21.54 and 1.21 mg kg–1 at AZ, and 15.79 and 0.48 mg kg–1 at WW. Those affected PTEs tended to enrich in near-river areas. Atmospheric deposition contributed more to soil Hg than did regular irrigation, but these two sources could not explain the considerable soil Hg accumulation. Three sources, including natural sources, hydraulic transport (torrential floods and regular irrigation) and atmospheric deposition, were identified and quantified based on the positive matrix factorization model, statistical methods and various auxiliary information. Hydraulic transport (mainly torrential floods) dominated the soil Hg input, which could explain 83.8% and 69.8% of the soil Hg input at AZ and WW, respectively. Atmospheric deposition dominated the soil Cd input, explaining 44.3% and 59.9% of the soil Cd input at AZ and WW, respectively. More attention should be given to the safe utilization of agricultural land and long-term monitoring of atmospheric deposition of Hg and Cd. This study could provide insights to prevent PTE diffusion along the above dominant transportation pathways while developing similar mine regions.

Characteristics of the methane (CH4) mole fraction in a typical city and suburban site in the Yangtze River Delta, China

China is the largest emitter of greenhouse gases in the world. However, the atmospheric observation of greenhouse gases is relatively sparse. In this study, surface measurements of CH4 over 5 years at a typical city site (Hangzhou) in an economically developed region in China were conducted to study the temporal variations and the influence of meteorological factors and airmass transport. The CH4 observations from a suburban site (Lin'an station [LAN]) which is a World Meteorological Organization/Global Atmosphere Monitoring Program (WMO/GAW) regional site, were also compared. Our results showed that the atmospheric CH4 mole fraction in Hangzhou was not only affected by meteorological factors and topography, but also by strong local emissions. Although the distance between the two stations was only 50 km, there was a significant difference in the temporal CH4 variations. The strong anthropogenic emissions in the city were responsible for the urban-suburban site difference. The CH4 peaks in the diurnal cycles in Hangzhou corresponded to rush hours, and there were unique variations during special periods (i.e., the National Day holiday, coronavirus disease 2019 [COVID - 19] lock-down). It also led to an annual average CH4 mole fraction at the Hangzhou station (HZ) that was on average 111.1 ± 1.6 ppb higher than that at the LAN from 2016 to 2020. The lock-down measures caused by the outbreak of COVID - 19 decreased the atmospheric CH4 mole fractions by 6.8% in Hangzhou but only 1.9% in Lin'an in 2020 compared to those in 2019. Excluding the data in 2020, the annual growth rate of the CH4 mole fraction was 19.0 ppb yr−1 in Hangzhou. Our results indicated that the CH4 mole fraction in Hangzhou was mainly driven by local anthropogenic emissions, although they were influenced by emissions from surrounding cities such as Nanjing and Ningbo.

Predicting Housing Evacuation Process during Natural Disaster Event Using Pathfinder Simulation, Puuwatu Kendari Real Estate Complex as A Case Study

Housing site plan should respond to safety standards for disaster evacuation, especially in Kendari City, Indonesia. It is caused by its geological conditions at high risk of natural disasters such as earthquakes, liquefactions, tsunamis, etc. The study on housing accessibility quality for the evacuation process in Kendari was limited. This study was conducted to identify the evacuation access quality of the housing site plan in Puuwatu Kendari as a case study. The main indicators to measure evacuation access quality are user characters, housing unit layouts, and the width of circulation access including the pedestrian path, road system, and the assembly point. These indicators are analyzed by the Pathfinder application. It is identified that the actual time for the total evacuation process outside of housing units is 44,4 seconds and into the assembly point (the nearest open public space) 103,5seconds. The actual time of evacuation to reach outside of housing units is still in the standard range of 2-3 minutes. On the other hand, the actual time of evacuation to reach open public space is 287 seconds still within the standard 30 minutes. It is caused by the distance of the assembly point in a radius of 60-70 meters. The quality of the assembly point is the main problem for the typical housing site plan in this case study. Respectively, the housing site plan in Kendari and the other similar cities have to be managed to comply with the standard for the disaster evacuation process.

Riparian Groundwater Level Variation and Its Impacts on Bank Erosion in the Middle Yangtze River

AbstractThe interaction between groundwater flow and river flow plays an important role in the bank erosion process, but field measurements on riparian groundwater flows remain very limited, especially in large river systems. Three monitoring wells of groundwater flow were constructed at two typical sites of the Middle Yangtze River (MYR) in 2021, with the hydrographs of the riparian groundwater level and river stage being obtained. Results indicated that (a) the variation in the groundwater level generally followed with the river stage during the flood peak period, but decoupled from the river stage during the recession period; (b) the delayed response of the groundwater level to river stage variation was quantified by the ratio of their change rates, which linearly increased with the magnitude of the river stage, but decreased with the change rate of the river stage as a loose power function; and (c) the increasing ground water level resulted in a 61% loss of the cohesion of upper cohesive bank soil and a complete loss of the apparent cohesion of the lower noncohesive bank soil. The major mechanism underlying the influences of the groundwater flow on bank erosion in the MYR is probably the development of pore water pressure that changes the forces acting on soil block and reduces the soil shear strength, whereas seepage erosion is seemingly not intensive. The current study can provide a direct evidence for the response of the riparian groundwater level variation to the river stage change in a large river system.

Ectopic cilia of the eyelid with ectopic lacrimal gland

Ectopic cilia of the eyelid is a rare congenital anomaly. Here we report a case of a 22-year-old patient with an extra tuft of eyelashes with watering since birth. Excision of the tuft and histopathology revealed a “pilosebaceous unit with ectopic lacrimal gland.” Ectopic cilia are caused by the replacement of meibomian glands with skin glands. Associated lacrimal gland tissue is a choristoma. The typical site of occurrence of ectopic cilia is mostly in the junction of the medial two-third and lateral one-third of the eyelid. Proper preoperative planning with complete surgical excision provides gratifying cosmetic results with no recurrence.

Bioavailability and regional transport of PM2.5 during heavy haze episode in typical coal city site of Fenwei Plain, China.

Despite the decrease in anthropogenic emissions, haze episodes were still frequent in the Fenwei Plain, which was identified as one of the three key areas for air pollution control. Herein, PM2.5 samples were collected to investigate the influence of festival effect during the Chinese Spring Festival from February 2rd to 13th, 2019, in Linfen on the Fenwei Plain. The characteristics of element pollution, enrichment factor, source apportionment, regional transport of PM2.5, and health risk assessment were discussed. Meanwhile, the simulated lung fluid method (SLF) was carried out to accurately assess the inhalation risks of heavy metals (HMs). Results indicated that the average concentration of PM2.5 was 195.6μg·m-3 during the studying period. Road fugitive dust (15.6%), firework burning source (25.6%), industrial emission (30.5%), and coal combustion (28.3%) were identified by positive matrix factorization (PMF) modeling. Using the HYSPLIT trajectory model, air masses from the central Shaanxi, southern Hebei, and northern Henan were the dominant transport paths during the Spring Festival, which contributed 21.9 and 41.2% of total trajectories, respectively. The findings that high PSCF and CWT levels were found in central Shaanxi, southern Hebei, and northern Henan were confirmed. The SLF mean bioaccessibility (%) of the solubility of particulate metals was in order of Mn > Ni > Sb > Ba > Zn > Pb > Cr. However, the carcinogenic risk value of Cr was the highest, exceeding the maximum acceptable risk. The present study provided important information for further analyzing the air pollution cause of Fenwei Plain.

Hormone therapy and fractures in postmenopausal women.

Fracture rates have been reported to be higher among older women living with HIV (WLWH) than HIV- women. Hormone therapy with estrogen can reduce vasomotor symptoms (VMS) associated with menopause and prevent fractures. As data are limited on the benefits of hormone therapy use in WLWH, we examined associations of hormone therapy, use and fractures. A prospective study of 1765 (1350 WLWH and 415 HIV-) postmenopausal Women's Interagency HIV Study (WIHS) participants was performed, including self-reported hormone therapy, use and fracture data from 2003 to 2017. Proportional hazard models determined predictors of new fractures at any site or at typical fragility fracture sites (hip, spine, wrist). At the first postmenopausal visit, the median (IQR) age of WLWH was slightly younger than HIV- women [49.8 (46.4-53) vs. 50.7 (47.5-54), P = 0.0002] and a smaller proportion of WLWH reported presence of VMS (17% vs. 26%, P < 0.0001). A greater proportion of WLWH than HIV- women reported hormone therapy use (8% vs. 4%, P = 0.007) at the first postmenopausal visit. In multivariate analyses, white race and smoking were significant predictors of incident fracture at any site but hormone therapy ( P = 0.69) and HIV status ( P = 0.53) were not. Our study did not find evidence of benefit or harm with regards to fracture outcomes in postmenopausal WLWH receiving hormone therapy. Further research is needed to determine whether hormone therapy has benefits beyond treatment of VMS, such as prevention of adverse aging-associated outcomes.

Ag Atom Anchored on Defective Hexagonal Boron Nitride Nanosheets As Single Atom Adsorbents for Enhanced Adsorptive Desulfurization via S-Ag Bonds.

Single atom adsorbents (SAAs) are a novel class of materials that have great potential in various fields, especially in the field of adsorptive desulfurization. However, it is still challenging to gain a fundamental understanding of the complicated behaviors on SAAs for adsorbing thiophenic compounds, such as 1-Benzothiophene (BT), Dibenzothiophene (DBT), and 4,6-Dimethyldibenzothiophene (4,6-DMDBT). Herein, we investigated the mechanisms of adsorptive desulfurization over a single Ag atom supported on defective hexagonal boron nitride nanosheets via density functional theory calculations. The Ag atom can be anchored onto three typical sites on the pristine h-BN, including the monoatomic defect vacancy (B-vacancy and N-vacancy) and the boron-nitrogen diatomic defect vacancy (B-N-divacancy). These three Ag-doped hexagonal boron nitride nanosheets all exhibit enhanced adsorption capacity for thiophenic compounds primarily by the S-Ag bond with π-π interaction maintaining. Furthermore, from the perspective of interaction energy, all three SAAs show a high selectivity to 4,6-DMDBT with the strong interaction energy (−33.9 kcal mol−1, −29.1 kcal mol−1, and −39.2 kcal mol−1, respectively). Notably, a little charge transfer demonstrated that the dominant driving force of such S-Ag bond is electrostatic interaction rather than coordination effect. These findings may shed light on the principles for modeling and designing high-performance and selective SAAs for adsorptive desulfurization.

Regional impacts of black carbon morphologies on shortwave aerosol–radiation interactions: a comparative study between the US and China

Abstract. Black carbon (BC) is one of the dominant absorbing aerosol species in the atmosphere. It normally has complex fractal-like structures due to the aggregation process during combustion. A wide range of aerosol–radiation interactions (ARIs) of BC have been reported throughout experimental and modeling studies. One reason for the large discrepancies among multiple studies is the application of the oversimplified spherical morphology for BC in ARI estimates. In current climate models, the Mie theory is commonly used to calculate the optical properties of spherical BC aerosols. Here, we employ a regional chemical transport model coupled with a radiative transfer code that utilizes the non-spherical BC optical simulations to re-evaluate the effects of particles' morphologies on BC shortwave ARI, and the wavelength range of 0.3–4.0 µm was considered. Anthropogenic activities and wildfires are two major sources of BC emissions. Therefore, we choose the typical polluted area in eastern China, which is dominated by anthropogenic emissions, and the fire region in the northwest US, which is dominated by fire emissions in this study. A 1-month simulation in eastern China and a 7 d simulation in the fire region in the northwest US were performed. The fractal BC model generally presents a larger clear-sky ARI compared to the spherical BC model. Assuming BC particles are externally mixed with other aerosols, the relative differences in the time-averaged clear-sky ARI between the fractal model with a fractal dimension (Df) of 1.8 and the spherical model are 12.1 %–20.6 % and 10.5 %–14.9 % for typical polluted urban cities in China and fire sites in the northwest US, respectively. Furthermore, the regional-mean clear-sky ARI is also significantly affected by the BC morphology, and relative differences of 17.1 % and 38.7 % between the fractal model with a Df of 1.8 and the spherical model were observed in eastern China and the northwest US, respectively. However, the existence of clouds would weaken the BC morphological effects. The time-averaged all-sky ARI relative differences between the fractal model with a Df of 1.8 and the spherical model are 4.9 %–6.4 % and 9.0 %–11.3 % in typical urban polluted cities and typical fire sites, respectively. Besides, for the regional-mean all-sky ARI, the relative differences between the fractal model and the spherical model are less than 7.3 % and 16.8 % in the polluted urban area in China and the fire region in the US, respectively. The results imply that current climate modeling may significantly underestimate the BC ARI uncertainties as the morphological effects on BC ARI are ignored in most climate models.

Climatic effects on soil organic nitrogen fractions and amino acid chirality in paddy soils

Soil organic nitrogen (N) accounts for more than 90% of the total N (TN) in paddy soils. An inadequate understanding of the different organic N fractions in paddy soils and their corresponding bioavailability under different climatic conditions has constrained the development of appropriate nutrient management strategies in rice production. Here we apply a modified Bremner method coupled with High Performance Liquid Chromatography (HPLC) to characterize how Soil Organic Nitrogen (SON) fractions and amino acid chirality vary under different climatic conditions by sampling five typical rice production sites along a latitudinal gradient. According to the results, climate had no obvious influence on TN, N form, and individual amino acid concentrations. However, the proportions of various N forms in TN had linear relationships with annual mean temperature, with high correlation coefficients. Amino acid components also exhibited similar trends (with correlation coefficients as high as 0.85). Most notably, consistent linear relationships were observed between the D/L ratios of several amino acids and annual mean temperature in paddy soils (correlation coefficients = 0.18–0.92). The findings of the present study could provide insights on SON and amino acid dynamics in paddy soil systems under intensive production along climate gradients.

Extraction of Long Time-Series Vegetation Indices from Combined Multisource Satellite Imagery.

Extracting vegetation cover information by combining multisource satellite images can improve the time scale of vegetation cover monitoring, realize encrypted observation in short period, and shorten the regional vegetation remote sensing monitoring cycle. The NDVI and RVI datasets from 2007–2019 were extracted using 9 phases of multisource satellite images (Landsat TM/OLI, Sentinel-2 MSI, and GF-1 PMS) covering Xiaxi, Sichuan. Three typical validation sites representing higher vegetation cover in mountains and no vegetation cover in water bodies in the region, respectively, were selected to extract NDVI and RVI at the corresponding locations. Linear regression and Spearman correlation coefficient (ρ) analysis were used to verify the correlation between NDVI and RVI from multisource images. The results showed that the vegetation indices fluctuated smoothly in the time series within the validation sites, and the vegetation indices of multisource satellite images were good measures of long-term vegetation cover in the region; the vegetation indices of the same satellite images showed significant correlations (both R2 and ρ exceeded 0.8), and the vegetation indices of different satellite images (PSM and MSI, PSM and OLI) showed more significant correlations (both R2 and ρ exceeded 0.7); the smaller the difference between the original resolutions of satellite images, the more significant the correlation between the extracted NDVI and RVI.