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[Display omitted] • Na 2 CO 3 and Y 2 O 3 were codoped into Li 4 SiO 4 sorbents to enhance the CO 2 sorption performance. • The optimized sorbent showed high and stable performance with the cyclic conversions of ∼96 %. • The doped material exhibited high and stable heat storage density of 557.8 kJ/kg. • Yttrium doping exerted triple positive effects on the CO 2 sorption reaction. • The positive effects included porosity creation, sintering resistance and producing lattice defects. High-temperature CO 2 capture based on Li 4 SiO 4 sorbents has been well recognized as an effective approach to mitigate the global warming issues. However, the relatively low sorption performance is one of the biggest challenges for the practical application. In the current investigation, Na- and Y-based dopants have been employed to enhance cyclic CO 2 sorption performance of Li 4 SiO 4 sorbents. Various physicochemical properties and cyclic CO 2 sorption performance of the prepared sorbents have been systematically studied. The results indicated that Na 2 CO 3 and Y 2 O 3 codoped Li 4 SiO 4 sorbent (Li 4 SiO 4 -10Na-15Y) exhibited excellent cyclic CO 2 capture performance with stable capacity of >0.27 g CO 2 /g sorbent (corresponding to the carbonation conversion of ∼96 %) during 15 sorption/desorption cycles. Even under lower CO 2 concentration and longer cycles, satisfying conversions of 85 % could be kept in the cyclic tests for the codoped Li 4 SiO 4 sorbent. In addition, the materials also showed high heat storage density of 557.8 kJ/kg and the performance was stabilized in the multicycle energy storage/release tests. The characterization results showed that the introduction of Y-based dopants induced triple positive effects for Li 4 SiO 4 including porosity creation, sintering-resistant ability, and producing Li 4 SiO 4 lattice defects. As a result, the enhanced specific surface area and reduced diffusion resistance were achieved and, thus, the CO 2 sorption performance including sorption capacity (heat storage density) and cyclic stability was obviously improved. [ABSTRACT FROM AUTHOR]

[Display omitted] • AOB population was enriched through long-term inhibition of FA on NOB activity. • FNA-dependent response of the biological nitritation process was investigated. • Hellinga model could perfectly describe the nitritation inhibition by FNA. • FNA reduced the Nitrosomonas abundance, but increased the Paracoccus abundance. • Nitrosomonas was the key biomarker indicating the nitritation to FNA constraint. This work comprehensively deciphered the effect of free nitrous acid (FNA) on the microbial community, inhibitory kinetics, and nitrifiers in nitritation process. Nitritation was first successfully achieved through selective inhibition of free ammonia (FA) on nitrite oxidizers (NOB). Then, batch tests clearly showed that FNA significantly inhibits the ammonia oxidation rate (r su) and the growth rate (μ) of ammonia oxidizers (AOB), which was well described by the Hellinga model (K I = 0.222 mg·L−1). The structural equation model indicated that FNA was significantly and negatively associated with r su , μ , Nitrosomonas, Commamons, Nitrospira, and Nitrotoga and positively correlated with Paracoccus. Furthermore, Nitrosomonas significantly drove the ammonia utilization and growth of AOB and was identified as the most important functional biomarker indicating the nitritation in response to FNA levels using random forest model. This study provides helpful information on the kinetics of the mechanism underlying the FNA inhibition on nitrification. [ABSTRACT FROM AUTHOR]

A numerical wave tank (NWT) based on the RANS equations is established by adding source terms into the momentum equation for generating wave and absorbing the reflected waves effectively. The wave dissipation induced by double curtain-wall breakwater and the flow field nearby under the action of regular wave are simulated. The effects of relative immersed depth of barrier on transmission coefficient are analyzed. The numerical results are identical with the experimental data, while they are different a lot from the results of the Lapa formula. The effects of relative width of horizontal plate, relative depth, wave slope are investigated, and a revised formula is presented based on comprehensive verification with both the experiment and numerical results. [ABSTRACT FROM AUTHOR]

The tetrasaccharide repeating unit of Escherichia coli O9a, α-d-Manp-(1→2)-α-d-Manp-(1→3)-α-d-Manp-(1→3)-d-Manp, and the pentasaccharide repeating unit of E. coli O9 and Klebsiella O3, α-d-Manp-(1→2)-α-d-Manp-(1→2)-α-d-Manp-(1→3)-α-d-Manp-(1→3)-d-Manp, were synthesized as their methyl glycosides. Thus, selective 3-O-allylation of p-methoxyphenyl α-d-mannopyranoside via a dibutyltin intermediate gave p-methoxyphenyl 3-O-allyl-α-d-mannopyranoside (2) in good yield. Benzoylation (→3), then removal of 1-O-methoxyphenyl (→4), and subsequent trichloroacetimidation afforded the 3-O-allyl-2,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate (5). Condensation of 5 with methyl 4,6-O-benzylidene-α-d-mannopyranoside (6) selectively afforded the (1→3)-linked disaccharide 7. Benzoylation of 7, debenzylidenation, benzoylation, and deallylation gave methyl 2,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→3)-2,4,6-tri-O-benzoyl-α-d-mannopyranoside (11) as the disaccharide acceptor. Coupling of 11 with (1→2)-linked mannose disaccharide donor 17 or trisaccharide donor 21, followed by deacylation, furnished the target tetrasaccharide and pentasaccharide, respectively. [Copyright &y& Elsevier]

A highly concise and effective synthesis of the mannose octasaccharide of the N-linked glycan in the adhesion domain of human CD2 was achieved via TMSOTf-promoted selective 6-glycosylation of a trisaccharide 4,6-diol acceptor with a pentasaccharide donor, followed by deprotection. The pentasaccharide was constructed by selective 3,6-diglycosylation of 1,2-O-ethylidene-β-d-mannopyranose with 2-O-acetyl-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate, while the trisaccharide was obtained by selective 3-O-glycosylation of allyl 4,6-O-benzylidene-α-d-mannopyranoside with the same disaccharide trichloroacetimidate, followed by debenzylidenation. The mannose hexasaccharide antigenic factor 13b was synthesized by condensation of a trisaccharide donor, 2-O-acetyl-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→3)-4,6-di-O-acetyl-2-O-benzoyl-α-d-mannopyranosyl trichloroacetimidate, with a trisaccharide acceptor, methyl 3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-d-mannopyranoside, followed by deprotection. [Copyright &y& Elsevier]

Based on the annual maximum water level record spanning about 60 years at 34 gauging stations, we conduct flood frequency analysis in the Pearl River Delta (PRD) with generalized extreme value (GEV) distribution. The GEV model performs sound estimation with the correlation coefficient at most stations larger than 0.99. To better understand the flood risk especially in ungauged regions, the spatial distribution of flood-stage is displayed for three given return periods, 10-year, 20-year and 50-year. Similar pattern can be identified for different return periods except the difference in magnitude, which generally exhibits a decreasing trend from the upper region to offshore area with a scope of about 2–9 m. Additionally, a comparison between pre-1980 and post-1980 is carried out to quantify the flood-stage alteration. The results show that most stations display increasing flood risk except for some stations in the upper estuaries, which experienced slight water level decline. Particularly, the lower part of the PRD is vulnerable to the most severe flood-stage increment. The estimated extreme water level increases by 0.35 m (14.96%), 0.59 m (21.23%) and 1.06 m (29.96%) on average at stations corresponding to 10-year, 20-year and 50-year return period, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] The quasi-Monte Carlo (QMC) method was enhanced to solve the population balance model (PBM) including aggregation and fragmentation processes for simulating the temporal evolutions of characteristic sizes and floc size distributions (FSDs) of cohesive sediments. Ideal cases with analytical solutions were firstly adopted to validate this QMC model to illustrate selected pure aggregation, pure fragmentation, and combined aggregation and fragmentation systems. Two available laboratory data sets, one with suspended kaolinite and the other with a mixture of kaolinite and montmorillonite, were further used to monitor the FSDs of cohesive sediments in controlled shear conditions. The model results show reasonable agreements with both analytical solutions and laboratory experiments. Moreover, different QMC schemes were tested and compared with the standard Monte Carlo scheme and a Latin Hypercube Sampling scheme to optimize the model performance. It shows that all QMC schemes perform better in both accuracy and time consumption than standard Monte Carlo scheme. In particular, compared with other schemes, the QMC scheme using Halton sequence requires the least particle numbers in the simulated system to reach reasonable accuracy. In the sensitivity tests, we also show that the fractal dimension and the fragmentation distribution function have large impacts on the predicted FSDs. This study indicates a great advance in employing QMC schemes to solve PBM for simulating the flocculation of cohesive sediments. [ABSTRACT FROM AUTHOR]

Middle deep borehole heat exchanger (DBHE) has become widely known as one of the main ways of geothermal energy development and utilization, and the use of middle DBHE system for heating buildings has received much attention. More accurate analytical models for a coaxial borehole heat exchanger (CBHE) have been built using the convolution theorem, however, a U-shaped deep borehole heat exchanger (U-DBHE) has not been reported. Therefore, in this paper, to obtain more accurate fluid temperature distribution, an analytical model of middle DBHE considering geological stratification phenomenon is developed by using convolution theorem. The relative error of the analytical model is verified within 5% by numerical simulation. At the same time, the interaction between the three factors was analyzed and studied by response surface method: mass flow, inlet temperature and geothermal gradient on heat extraction and heat loss rate. The results reveal that for thermal extraction, the significance levels of the three factors are from large to small: geothermal gradient > inlet temperature > mass flow, for heat loss rate, the two factors of flow rate and inlet temperature are significant, and the impact of geothermal gradient is not significant. In this engineering project, when the inlet water temperature is 10 °C, the flow rate is 26.65 kg/s and the geothermal gradient is 4.5 °C/hm, there is a maximum heat extraction of 2424.16 kW. [ABSTRACT FROM AUTHOR]

Highlights • The optimal filler/sand ratios of sand concrete using GGBS and FA fillers are 0.13 and 0.11 respectively. • The mechanical properties of sand concrete increase and then decrease with filler content increasing. • Sand concrete made with superfine waste sand presents an excellent abrasion resistance. • Sand concrete with the GGBS filler has higher amount of hydrate products and lower porosity than that with FA. Abstract In this paper, superfine waste sand generated in waterway regulation engineering was used as the main raw material to produce sand concrete. The effects of ground granulated blast-furnace slag (GGBS) and fly ash (FA) on the mechanical properties, abrasion resistance, and microstructure of sand concrete were measured and compared. The results show that the mechanical properties of sand concrete increase and then decrease with increasing filler content. The optimal filler/sand (F/S) ratios of sand concrete using GGBS and FA fillers are 0.13 and 0.11, respectively. With 300 kg/m3 of cement content, the incorporation of 200 kg/m3 and 150 kg/m3 of GGBS and FA filler, respectively, results in maximum compressive strengths of 36.1 MPa and 30.5 MPa, respectively, at 28 days, and the corresponding splitting tensile strengths are 3.03 MPa and 2.15 MPa, respectively. This optimum mix with weight losses of 6.58% and 8.01% for GGBS and FA fillers, respectively, presents an excellent abrasion resistance. Furthermore, the test results of scanning electron microscopy and mercury intrusion porosimeter indicate that sand concrete with the GGBS filler has higher amount of hydrate products and lower porosity than that with FA. These findings verify the potential usage of sand concrete made with superfine waste sand as a substitute for ordinary concrete in local hydraulic engineering. [ABSTRACT FROM AUTHOR]

Calcium–modified water hyacinth biochar (WHCBC–400 and WHCBC–600) was prepared using water hyacinth as raw material and calcium chloride as modifier at two pyrolysis temperatures of 400 °C and 600 °C. The effectiveness for removal of malathion, a typical organophosphorus pesticide from water were comparatively examined by the prepared adsorbents. The impacts of the pyrolysis temperature on performance of the biochar and adsorption behavior of malathion on the modified biochar were systematically studied by surface analysis, removal efficiency tests under different solution conditions, as well as data simulations. The adsorption mechanisms and reusability of the modified biochar were also investigated and experimented, respectively. The results indicated that the WHCBC–600 had a larger specific surface area and pore volume than the WHCBC–400, while WHCBC–400 had a greater polarity and hydrophilicity. Both of the two prepared biochars followed pseudo–second–order kinetics and their adsorption isotherms conformed to the Sips model. The maximum adsorption capacities of WHCBC–400 and WHCBC–600 were 128 mg/g and 32.7 mg/g, respectively. It was found that the adsorption of malathion by the biochars were dominated by chemisorption. Diffusion at the liquid film was the rate–limiting step in the adsorption process. The difference in the form of the calcium loadings, polarity of biochar, and the rate–limiting step of adsorption were important factors affecting the adsorption capacity of the biochar. In comparison, the specific surface area and pore volume of the prepared absorbents had less significant effects on the adsorption capacity. The main adsorption mechanism of the two modified biochars was surface complexation. In addition, the solution pH and coexisting material had little effect on the adsorption of malathion by WHCBC–400 and WHCBC–600. Both of the modified biochar had good regeneration performance. The study provided a new adsorbent for the removal of malathion from water. [Display omitted] • Low temperature biochar had greater polarity. • High temperature biochar had larger specific surface area and pore volume. • WHCBC–400 (128 mg/g) had higher adsorption capacity than WHCBC–600 (32.7 mg/g). • Polarity and liquid film diffusion were affecting the adsorption effect of biochar. • The main adsorption mechanism was surface complexation. [ABSTRACT FROM AUTHOR]

• The effects of anionic, cationic and neutral organic matters on the aggregation of microplastics are investigated. • All of the organic matters show positive effects on the growth of biofilm-coated microplastic aggregates. • The two-class population balance model is used to track the small and large microplastic subgroups under turbulence. Biofilm-coated microplastics are omnipresent in aquatic environments, carrying different organic matter (OM) that in turn influences the flocculation and settling of microplastic aggregates. In this study, the effects of chitosan, guar gum, humic acid, and xanthan gum on the flocculation of anthropogenic microplastics are examined under controlled shear through the mixing chamber experiments. The results show that all of the selected OMs have positive effects on biofilm culturing and thus enhance the growth of microplastic flocs, with more evident promoting effects for cationic and neutral OMs (i.e., chitosan and guar gum) than anionic OMs (i.e., humic acid and xanthan). No critical shear rate is observed in the size vs. shear relationship based on our measurements. In addition, the quadrature-based two-class population balance model is employed to track the development of bimodal floc size distributions (FSDs) composed of small and large microplastic flocs. The model predictions show reasonable agreement with the observed FSDs. The largest error of settling flux from the two-class model is 7.8% in contrast with the reference value measured by the camera-based FSDs with 30 bins. This study highlights the role of different OMs on microplastic flocculation and indicates that a two-class model may be sufficient to describe microplastic transport processes in estuaries. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Spatial variations in grain-size parameters contain information on sediment transport patterns. Therefore, in this study, 106 surficial sediment samples taken from the Pearl River Estuary (PRE), South China, were analyzed, to better understand the net sediment transport pattern in this region. The PRE is an area of fine-grained sediment and shows muddy patches with relatively coarse sediment in the north. The sorting coefficient of surficial sediment over the whole estuary is higher than 2, indicating a very poor sorting in this region. The relationship between the sand, silt and clay contents of the sediments was analyzed by a log-ratio analysis, and it was indicated that the selective deposition is a non-linear function of the sediment mixture composition. The net sediment transport pathways indicate four distinct characteristics of sediment transport over the PRE. The sediment is transported obviously southeastward in the upper part of the estuary due to the relatively stronger fluvial dynamics and northwestward in the lower part, due to the stronger tidal dynamics. However, in the central part of the PRE, the sediment transport vectors display a clockwise rotation trend and net deposition is taking place, as indicated by the convergence of the grain size trend. The trend vectors show that some of the sedimentary material is supplied from upper and lower parts of the estuary to this depocenter. This result is consistent with the residual current circulation pattern near Neilingding Island. The patterns of sediment transport reveal directions with the main areas of deposition and possible dispersal patterns in the PRE. [Copyright &y& Elsevier]

Abstract: This paper focuses on identifying changes in the tidal range and the duration of the flood tide in the Pearl River Delta region, China. Mann–Kendall test and regression methods are employed to verify the existence of trends in the annual tidal range and duration series (from the 1950s to 2005) at 17 stations in the 3 major tributaries of the delta. The research results indicate that generally there is an increasing trend in the tidal range and flood tide duration at most of the stations in the channel network. Moreover, the more upstream the location of the station, the more obvious the change in trend is, and these increasing trends are all significant at the stations in the upper part of the delta. Specifically, the tidal range at Shilong station in the East River has increased abruptly since the middle of the 1980s such that the mean level of post-1990 data is approximately three times that for pre-1985. Most stations near the mouth of the estuary show significant downward trends in the tidal range and flood tide duration. Results of the intersection point of the Mann–Kendall test curves for these Pearl River Delta stations appear mostly in 1980s–1990s, indicating that a noticeable change point occurs during this period. Human activities in the Pearl River Delta reached their peak during the 1980s. Among these, large-scale and long-term sand excavation modified the hydrodynamic regime dramatically in a way that increased the water depth and lowered the level of the riverbed, leading to an increased tidal prism and upstream movement of the tidal limit. Land reclamation is also likely to have had a relatively large effect on the tidal range and flood tide duration at stations near to the estuary mouth. Changes in other factors, such as freshwater flow and sea-level rise, seem to be of relatively minor importance. It is noteworthy that in a dry season the tidal dynamics are greatly enhanced and has resulted in strong saltwater intrusion into the estuary in recent years. [Copyright &y& Elsevier]