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Ignition delay times (IDTs) were measured in a shock tube facility for NH 3 /n-heptane mixtures with NH 3 concentrations in the blending fuel ranging from 0.3 to 0.95 by molar fraction. The measurements were conducted under low pressure of 2 atm and intermediate temperatures of 1350–1500 K at equivalence ratios of 0.5, 1, and 2. With the increase of n-heptane content or equivalence ratio, there is a decrease in the IDTs of NH 3 /n-heptane mixtures at intermediate temperatures. A detailed mechanism was updated in this study based on the mechanism of Dong et al. Subsequently, the proposed mechanism was compared to existing blending mechanisms of ammonia and n-heptane in terms of laminar burning velocities (LBVs), IDTs, and species profiles reported in literature. The present model improved the predictions in reproducing the performed experimental measurements compared to previous mechanisms. Finally, rate of production (ROP), sensitivity analysis, and instantaneous and cumulative reaction path analysis were performed to interpret the experiment observations and deepen the understanding of auto-ignition kinetics of ammonia and n-heptane. The results indicate that intermediate species, such as C 2 H 4 and C 3 H 6 , characterized by long lifespans and high concentrations during n-heptane decomposition, play a crucial role at elevated temperatures, while the significance of n-heptane dehydrogenation by NH 2 diminishes with increasing temperature. [ABSTRACT FROM AUTHOR]

• IDTs of H 2 /NC 7 H 16 mixture were measured in RCM. • A skeletal H 2 /NC 7 H 16 oxidation mechanism was developed. • Hydrogen diffusion velocity is determined by injection direction. • Hydrogen diffusion velocity influences pre-mixture homogeneity and slipping. • Hydrogen injection timing affects pre-mixture homogeneity and slipping. Achieving efficient lean combustion with homogeneous pre-mixtures is essential in marine low-speed two-stroke hydrogen/diesel engines. However, measures enhancing pre-mixture homogeneity may lead to hydrogen slipping. To address this, the numerical simulation research on injection process was carried out. A skeletal hydrogen/n-heptane oxidation mechanism with 49 species and 174 reactions was developed and validated against experimental ignition delay times in rapid compression machine with temperature range from 600 K to 800 K and pressure of 8 bar and 24 bar. Based on the mechanism, the influence of hydrogen injection parameters on pre-mixture homogeneity and hydrogen slip was investigated by three-dimensional computational fluid dynamic simulation. The angular, radial, and longitudinal velocity of hydrogen diffusion, determined by side and downward angle of hydrogen injectors directly impact the circumferential, radial, and longitudinal homogeneity of pre-mixture. By affecting swirl intensity and friction between fluid and cylinder wall, side angle indirectly influences longitudinal velocity, which dominates hydrogen slipping. Moderate side (10° − 20°) and downward (0° − 20°) angles of hydrogen injectors ensure both pre-mixture homogeneity and prevent hydrogen slipping. Finally, the influences of injection timing on pre-mixture homogeneity and hydrogen slipping were studied. An advanced injection timing (earlier than 226°CA) enhances mixing time but increases hydrogen slip risk. Conversely, delaying injection timing (later than 238°CA) prevents slipping but reduces pre-mixture homogeneity due to shorter mixing time. [ABSTRACT FROM AUTHOR]

In order to avoid the abnormal combustion in high-power hydrogen engine, a 3D CFD numerical model of a direct-injection spark-ignition hydrogen engine was built up based on a large-bore medium-speed four-stroke marine diesel engine using CONVERGE software. To obtain the influence of injection parameters on mixture homogeneity, a dimension reduction optimization method was proposed. The results revealed that the turbulence intensity and the penetration distance varied with the injection parameters, determined the level of mixture homogeneity. The performance comparison between the hydrogen engine and prototype diesel engine showed a great potential of hydrogen in internal combustion (IC) engines. • Process of improving homogeneity can be simplified by optimizing turbulence intensity and injection penetration distance. • Turbulence intensity and injection penetration distance varied with injection system parameters. • The higher the turbulence intensity, the faster the mixing rate. • Neither too long nor too short injection penetration distance was conducive to mixing. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly selective Hg2+ sensor QPE was developed based on quinolimide. • QPE had high sensitivity, low LOD and LOQ, wide pH range, and rapid response. • QPE -loaded test strips were fabricated for the visual detection of Hg2+. • QPE had been used for tracing Hg2+ in real water and soil samples and living cells. Herein, a novel fluorescent sensor QPE based on quinolimide was developed, which displayed the highly selective response to Hg2+ through the turn-on signal in aqueous media. The corresponding recognition mechanism of QPE for Hg2+ was investigated by the titration experiments, Job's plots, HRMS, and DFT calculations analysis. QPE could detect Hg2+ in a broad pH range (pH = 4–9) with the LOD of 20 nM and the LOQ of 66 nM. Meanwhile, QPE -loaded test strips were demonstrated in the visual detection of Hg2+. Importantly, QPE exhibited the reliable capability to track Hg2+ in real water and soil samples and yeast cells, indicating that QPE could be used as a prospective tool for monitoring Hg2+ in wide fields. [ABSTRACT FROM AUTHOR]

In Jiaozhou Bay, there are four wetland types, including sandy beaches, mud flats, tidal marshes, and estuarine intertidal zones. Four typical transects representing each of the wetland types were selected to investigate the flow dynamics, seawater-groundwater exchange and nutrients carried by submarine groundwater discharge (SGD). Based on field measurements of groundwater heads and salinity along each transect, the SGD averaged over the observation period was estimated using generalized Darcy's law. The SGD along the four transects ranges from 3.6 × 10 −3 to 7.6 cm/d with the maximum occurring at the sandy beach. The SGD rate has a good correlation with the hydraulic conductivities of the wetland sediments. There is a positive correlation between the ratio of NO 3 -N/DIN and SGD rates. The SGD-associated nutrient output rate ranges from 3.3 × 10 −2 to 9.5 mmol/m 2 /d for DIN (dissolved inorganic nitrogen), and from 6.2 × 10 −5 to 1.8 × 10 −2 mmol/m 2 /d for DIP (dissolved inorganic phosphorus). Compared to the nutrients delivered by the river, nutrients carried by SGD provide a more important source for the phosphate-limited environment to plankton in Jiaozhou Bay. [ABSTRACT FROM AUTHOR]

• Ignition properties of H 2 /n-C 7 H 16 mixture was revealed by shock tube and mechanism. • H 2 /n-C 7 H 16 mixtures with more hydrogen and lower equivalence ratio have shorter IDT. • More active n-C 7 H 16 consumes before H 2 and triggers later radicals' reactions. • A skeletal hydrogen/PRF mechanism was proposed based on a skeletal PRF mechanism. In the present work, the experiments of measuring ignition delay times (IDTs) of the hydrogen/ n -heptane mixture at high temperature (1130–1485 K) and low pressure (1.25 atm) by a shock tube is implemented. The results show that mixtures with higher hydrogen proportion and lower equivalence ratio present shorter IDT. In the case of high hydrogen proportion, the n -heptane addition causes an obvious inhibition effect on the ignition of the mixture. Whereas, as the hydrogen proportion decreases, such inhibition effect weakens. As the experimental values are consistent with the predicted IDTs by NUI (National University of Ireland) mechanism, the NUI mechanism was selected to conduct the kinetic study. The consumption of n -heptane at the initial stage of reaction is earlier than that of hydrogen because the activities of n -heptane's H-abstraction and decomposition reactions are relatively high. With shock tube experimental data as the calibration basis, a skeletal hydrogen/PRF (Primary Reference Fuel) mechanism, was updated from a skeletal PRF mechanism. The skeletal hydrogen/PRF mechanism, consisting of 49 species and 162 reactions had been validated against shock tube experiment of hydrogen, n -heptane, isooctane pure fuel, PRF, and hydrogen/ n -heptane mixture. [ABSTRACT FROM AUTHOR]

A novel sensor T2 was synthesized through the introduction of N,N -di (pyridin-2-ylmethyl)ethane-1,2-diamine into the quinolimide fluorophore. T2 could detect Cd2+ and Zn2+ via fluorescence enhanced signals, and Cd2+ was distinguished from Zn2+ through the visible color change and the addition of S2−. The T2 -Cd2+ complex exhibited the exceptional selectivity to S2− through the restored fluorescence. Moreover, the combinational logic gate with OR and INHIBIT functions was constructed by using the controlled fluorescence "off-on" states of T2. The recoveries of Cd2+ and Zn2+ in water samples with T2 were in range of 95.6%–106.5%. And T2 was used for the visualization of Cd2+, Zn2+, and S2− in yeast cells. [Display omitted] • The quinolimide-based sensor T2 was developed for sensing Cd2+, Zn2+, and S2−. • T2 could distinguish Cd2+ from Zn2+ through the visible color change and the addition of S2−. • The T2-Cd2+ complex exhibited the exceptional selectivity to S2−. • The combinational logic gate with OR and INHIBIT functions was constructed. • T2 was applied to detect Cd2+, Zn2+, and S2− in water samples as well as in yeast cells. [ABSTRACT FROM AUTHOR]

Steady-state seawater–groundwater interactions are simulated for homogeneous, anisotropic unconfined coastal aquifers using the two-dimensional numerical model MARUN. The spatial salinity distributions are approximately independent of the horizontal hydraulic conductivity K x when α L K x K z ⩾ 10 −6 m 2 /s. Here K z is vertical hydraulic conductivity and α L is longitudinal dispersivity. Both the fresh groundwater discharge rate Q f and seawater recirculation rate Q s depend linearly on K x . These conclusions are validated by a semi-analytical method. The increase of anisotropy ratio pushes the saltwater wedge interface seaward and reduces Q s . The increment of the longitudinal/transverse dispersivity ratio with fixed longitudinal dispersivity decreases the slope of isosalines and Q s . When the seabed slope angle θ increases from 0.01 to π /2, the freshwater–seawater interface moves landward. The increment of θ increases Q s slightly when θ < π /4 and reduces Q s when θ > π /4. The inland recharge rate Q f is independent of the seabed slope. [ABSTRACT FROM AUTHOR]

[Display omitted] A new quinolimide derivative MSH was designed and developed as a highly sensitive Zn2+ fluorescent turn-on sensor in neutral aqueous media. After binding Zn2+ with a 2:1 stoichiometry, the excellent fluorescence enhancement (Φ Zn(II) = 0.555) of MSH was observed, along with the low LOD of 8 nM, wide pH usage range (pH = 4–12), and fast response time of less than 15 s. The combinational logic gate and the memory device were constructed to take advantage of the emission of MSH controlled by Zn2+ and EDTA. Additionally, Zn2+ in actual water samples was detected with the satisfactory recovery rates between 96.6 % and 104 %. And MSH was successfully fabricated into paper strips and used as an imaging tool in yeast cells for tracking Zn2+ levels. [ABSTRACT FROM AUTHOR]

• Auto-ignition properties of ammonia with low n-heptane content were studied using RCM. • The IDTs were measured in the temperature range 620–970 K and pressure range 15–25 bar. • An optimization was conducted based on the existing detailed reaction mechanism. • A small content of n-heptane has a great effect on the IDT and HRR of the mixture. • N-heptane is consumed mainly by the reaction of extracting H atoms by NH2. The low reactivity of ammonia leads to a low combustion efficiency of premixed combustion mode ammonia-diesel engines. In order to overcome this shortcoming, a small amount of diesel is pre-injected into the ammonia pre-mixture to increase the reactivity. Therefore, this study investigated the auto-ignition characteristics of lean-equivalent-rich ammonia/n-heptane mixtures at low n-heptane blending ratios (2 %&5 %&10 %) and wide thermodynamic conditions (Temperature range of 620–970 K, Pressure range of 15–25 bar) via rapid compression machine. The results showed that a small content of n-heptane had a strong ignition-promoting effect: significantly reducing the Ignition Delay Times (IDTs) and increasing the heat release rate. Besides, the IDTs of the mixture decreased with the increase in equivalence ratio, while the stoichiometric mixture showed the highest heat release rate. Moreover, an improved dual-fuel mechanism, which dramatically enhanced the predictive performance of IDTs for ammonia/n-heptane and pure ammonia mixtures, was proposed to illuminate the reaction kinetic properties. N-heptane is consumed prior to ammonia and at a higher rate. The reaction of NH 2 extracting H atoms from n-heptane was the main consumption reaction of n-heptane at low n-heptane content conditions. And the reaction of ammonia consuming OH radicals was the most ignition-inhibiting reaction. Besides, the reaction NH 3 + O 2 = NH 2 + HO 2 plays an important role in the extent of the negative temperature coefficient effect for the mixture under different blending ratios and equivalence ratios. [ABSTRACT FROM AUTHOR]

Abstract: Model calculations for the n+56Fe reaction have been performed by using extended UNF code, which is based on the unified Hauser–Feshbach and exciton model. Based on the excellent agreement with the experimental double-differential cross-sections of neutron, alpha and proton, the total kerma coefficients are derived naturally with the formula (), which contains more comprehensive parameter information. The discrepancies of total kerma coefficients between the experimental data, evaluated data and the calculated results of this paper have been further analyzed, and one can have some confidence in predicting the kerma coefficients derived naturally by this model calculation. [ABSTRACT FROM AUTHOR]

The development of methanol/diesel dual-fuel engines urgently requires further study on chemical kinetic models for binary fuels. Ignition delay of lean and stoichiometric methanol/n-heptane mixtures (30/70, 50/50, 70/30, and 90/10) diluted with argon was investigated at high temperature (T = 1195 K–1514 K) and low pressure (p = 2 bar) using an aerosol shock tube and a detailed LLNL3.1 mechanism. The results indicated that LLNL3.1 mechanism agreed well with the current measurements. An increase in methanol can accelerate the ignition process at Ф = 1, because of the key radical---HO2, produced by CH2OH + O2=CH2O + HO2, which was affected by the methanol concentration. HO2 would subsequently attack the parent fuels and combine with H radical (HO2+H = 2OH), leading to the booming radical pool. For lean mixtures, n-heptane promoted the reactivity of system due to its high sensitivity to reaction H + O2=O + OH. The higher initial O2 concentration expedited this reaction and shortened the IDT. Besides, both methanol and n-heptane undergo H-abstraction reaction mostly by H radical, however, these reactions showed an inhibition effect on reactivity. This is caused by the competition for H radical between O2 and the parent fuels. Also, the fuel radicals, produced by C7H15-3, had a low decomposition reaction rate thus slowing down the chain branching and suppressing the reactivity of system. • Ignition characteristics of methanol/n-heptane mixtures were studied by shock tube and mechanism. • Methanol accelerated the auto-ignition for stoichiometric mixtures due to the HO2 radical. • N-heptane promoted the reactivity for lean mixtures due to its high O2 sensitivity. • H-abstraction of the parent fuels by H radical showed an inhibition on auto-ignition. [ABSTRACT FROM AUTHOR]

• Influence of exhaust gases on the ignition of CH 4 /n-C 7 H 16 mixture were revealed. • Thermal, chemical and third-body collision effects are qualitatively compared. • CO 2 suppressed ignition due to its thermal and chemical effect. • H 2 O accelerated ignition due to its third-body and chemical effect. • The addition of CO 2 /H 2 O mixture slightly fastened auto-ignition of CH 4 /n-C 7 H 16. To further optimize the combustion performance of natural-gas/diesel engine under exhaust gas recirculation (EGR) condition, influence of physicochemical impacts of H 2 O and CO 2 on the ignition characteristics of n-heptane/methane mixture (Φ = 0.5/1.0) under various thermodynamic conditions (p = 2 bar/1199 K < T < 1568 K, p = 60 bar/700 K < T < 1200 K) were investigated by shock tube and NUI mechanism. Experiments indicated at p = 2 bar/1199 K < T < 1568 K, CO 2 and H 2 O additions increased and shortened ignition delay times (IDT) respectively. Mixture of CO 2 and H 2 O slightly accelerated ignition. Original and minor modified NUI mechanism well captured the inhibition and acceleration effect of CO 2 and H 2 O on ignition respectively. Both thermal and chemical effects of CO 2 (R36:CO + OH = CO2 + H) were responsible for its ignition inhibition impacts at higher temperatures. Whereas thermal effect of CO 2 became the dominant factor at lower temperatures. Chemical effect of H 2 O (H 2 + OH<=>H + H 2 O&O + H 2 O<=>2OH) promoted OH formation and enhanced whole system reactivity, which suppressed its thermal effect and accelerated ignition process. At p = 60 bar/700 K < T < 1200 K, CO 2 addition significantly retarded ignition due to its thermal effect. At 900 K < T < 1200 K, the higher third-body efficiency of H 2 O promoted ignition (R21:H 2 O 2 (+M) = 2OH(+M)&R34:H + O 2 (+M) = HO 2 (+M)). At 700 K < T < 900 K, thermal effect of H 2 O, which suppressed its third-body effect, inhibited ignition progress. These observations implied that the impact of exhaust gases on the ignition of n-heptane/methane depended on the coupled influence mechanisms of physicochemical effects, the composition of exhaust gases and located thermodynamic conditions. At intermediate-temperature high-pressure conditions (typical thermodynamic conditions of dual-fuel engine), raising the concentration of H 2 O or CO 2 in exhaust gases accelerated or delayed the combustion progress of natural-gas/diesel engine at EGR condition by enhanced third-body effect or thermal effect respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple FA sensor H2 was developed based on quinolimide for the first time. • H2 had highly selective and sensitive to FA by the pseudo -first-order reaction. • H2 -loaded test strips were fabricated for the visual detection of FA. • H2 had been successfully applied to detect FA in living cells. A simple fluorescent sensor H2 containing quinolimide as a fluorophore and hydrazine as a reaction site was designed and synthesized for the detection of formaldehyde (FA). H2 had the high selectivity and sensitivity to FA through the pseudo -first-order reaction (k = 0.048 min−1), exhibiting the significantly enhanced fluorescence signal. The quantitative determination range of H2 for FA was 0–180 μM, and the LOD of FA is 1.7 μM. Moreover, H2 -loaded test strips were demonstrated in the visualization of sensing FA. And H2 was successfully applied for imaging FA in living cells. [ABSTRACT FROM AUTHOR]

Naturally occurring radon ( 222 Rn) and radium isotopes are widely used to trace water mixing and submarine groundwater discharge (SGD) in the coastal zones. However, their activities in groundwater are variable both spatially and temporally. Here, time series sampling of 222 Rn and radium was conducted to investigate their behavior in intertidal groundwater of Laizhou Bay, China. The result shows that groundwater redox conditions have an important impact on the behavior of tracers. The activities of tracers will decrease under oxidizing conditions and increase under reducing conditions. Radon and radium mass balance models were used to evaluate the flushing time and SGD based on spatial surveys in Laizhou Bay. The flushing time is estimated to be 32.9–55.3 d with coupled models, which agrees well with the result of tidal prism model. The trace-derived SGD in the whole bay ranges from 6.1 × 10 8 to 9.0 × 10 8  m 3 /d and the re-circulated seawater (RSGD) ranges from 5.5 × 10 8 to 8.5 × 10 8  m 3 /d. The average SGD and RSGD fluxes are 22.8 and 21.1 times greater than the Yellow River discharge in April 2014, respectively. The study provides a better understanding of the dynamics of coastal groundwater and behavior of tracers in a well-studied bay system. [ABSTRACT FROM AUTHOR]

Based on field measurements from two typical intertidal transects at Dan’ao Estuary, groundwater-surface water and associated nutrient exchanges are quantified. Both groundwater discharge rate (39.1 ± 7.0 cm d −1 ) and surface water inflow rate (7.7 ± 1.4 cm d −1 ) at the upstream mangrove swamp transect are much higher than those (1.6 ± 0.3 and 2.1 ± 0.4 cm d −1 , respectively) at the downstream bare flat one. This large difference leads to their contrasting nitrogen forms. Much higher water exchange rates at the upstream transect generate much higher net dissolved inorganic nitrogen (DIN, including NH 4 + , NO 2 - , and NO 3 - ), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi) fluxes (− 160.3 ± 39.2, − 14.6 ± 2.7, − 38.6 ± 7.0 mmol m −2 d −1 , respectively) than those (2.9 ± 0.9, − 0.08 ± 0.03, 1.1 ± 0.4 mmol m −2 d −1 , respectively) at the downstream one. The mangrove swamp at the upstream transect discharges substantial groundwater and associated nutrients to the estuary. The net nutrient loads by water exchange in this estuary can reach 23.5–78.7% of those by local river discharge. [ABSTRACT FROM AUTHOR]

• A quinolimide-based reversible sensor QPC for Cu2+ and S2− was developed. • QPC and its Cu2+ complex had the high specificity to detect Cu2+ and S2−. • QPC possessed high quantum yield, short response time, and low cytotoxicity. • The INHIBIT logic gate was simulated by the addition of Cu2+ and S2−. • QPC had been applied to detect Cu2+ and S2− in water samples and living cells. A quinolimide-based reversible fluorescent sensor QPC with carboxamidoquinoline as the receptor was prepared for the relay recognition of Cu2+ and S2−. QPC displayed the high selectivity and anti-interference ability to Cu2+ through the 1:1 binding mode. Subsequently, the selectively sensing S2− with the QPC Cu2+ complex gave a remarkable recovery of the emission. The LODs of QPC and its Cu2+ complex for Cu2+ and S2− were calculated to be 47.8 nM and 0.178 µM, respectively. Moreover, QPC and its Cu2+ complex had the satisfactory recoveries 93.5–105.8% for Cu2+ and 97.7–104.0% for S2− in water samples, and exhibited low cytotoxicity, which enabled them to image Cu2+ and S2− in yeast cells. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel quinolimide derivative (BNAL), bearing the amide-DPA receptor at position 9 of the heterocyclic ring, was synthesized for sequential detection of Cd2+ and S2−. BNAL could discriminate Cd2+ from Zn2+, showing the turn-on response upon interaction with Cd2+. After adding S2−, the fluorescence of the BNAL -Cd2+ solution was reverted through the displacement strategy. The limits of detection (LODs) of BNAL for Cd2+ and the BNAL -Cd2+ complex for S2− were found to be 17.9 nM and 1.51 μM, respectively. Finally, cell imaging experiments showed BNAL could be successfully employed for sequentially imaging Cd2+ and S2− via the off-on-off behavior in yeast cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Ignition characteristics of n -hexadecane/methane mixture under low-pressure high-temperature (P : 2.0 bar, 5.0 bar & T : 1269–1887K) and high-pressure low-temperature (P : 40–140 bar & T : 700–1200 K) conditions were studied by aerosol shock tube and CHEMKIN with LLNL C16 mechanism. The results indicated that at low-pressure high-temperature conditions, increasing initial pressure and decreasing equivalence ratio could reduce ignition delay times (IDT) by 39% and 52% respectively. N-hexadecane's addition and n -hexadecane's replacement also shortened IDT by 88% and 96% separately. Raising n -hexadecane's replacement further reduced IDT. The reduction degree of IDT dramatically decreased when n -hexadecane's content was high. N-hexadecane was fully consumed earlier than methane. Radicals that formed from n -hexadecane's decomposition induced H-abstraction of n -hexadecane, which advanced methane's slow oxidation. H was the crucial radical in n -hexadecane's H-abstraction reactions. At ultra-high-pressure low-temperature condition, adding n -hexadecane and increasing n -hexadecane content dramatically reduced IDT. With n -hexadecane's H-abstraction dominating ignition process, n -hexadecane's decomposition was significantly inhibited at low-temperature condition. OH was the key radical in n -hexadecane's H-abstraction reactions. The obviously suppressed n -hexadecane's decomposition was responsible for the same end time point of complete consumption of two fuels. These results are helpful for providing control methods for natural-gas preignition and abnormal combustion triggered by lubricating oil in dual-fuel marine engine. • Ignition characteristics of n -hexadecane/methane mixture was investigated by aerosol shock tube and kinetic study. •The addition of n -hexadecane obviously shortened ignition delay times of methane mixture. •The replacement of methane with n -hexadecane further shortened ignition delay times. •At low-pressure high-temperature, time point of complete n -hexadecane consumption was earlier than that of methane. •At high-pressure low-temperature, time point of complete n -hexadecane consumption was the same as methane. [ABSTRACT FROM AUTHOR]

To acquire ignition control methods for dual-fuel marine engine and HCCI engine, ignition characteristics of lean n-heptane/methane mixture under pressure of 2.0 bar and temperature range from 1241 to 1825 K were studied by shock tube and CHEMKIN with LLNL3.1 mechanism. And ignition processes under temperature range from 700 to 1200 K and pressure range from 40 to 140 bar were investigated by CHEMKIN with NUI mechanism. The results illuminate that at low-pressure high-temperature condition, n-heptane's replacement and the increase of n-heptane content obviously reduced ignition delay times (IDT). The reduction degree of IDT decreased when n-heptane content was high. N-heptane's addition also reduced IDT. But this reduction magnitude was less than that of n-heptane's replacement. Methane's addition slightly inhibited n-heptane's auto-ignition. The reaction time of n-heptane was obviously earlier than that of methane. N-heptane decomposition induced radical formation firstly, which triggered subsequent n-heptane's H-abstraction and the advance of methane's oxidation. At ultra-high-pressure low-temperature condition, increasing n-heptane's content enhanced negative temperature coefficient (NTC) behavior. The end time point of complete consumption of two fuels was the same. Low-temperature condition inhibited n-heptane decomposition, with n-heptane's H-abstraction dominating ignition process. • Ignition properties of CH4/n-C7H16 mixture was revealed by shock tube and mechanisms. • Active radicals formed from n-heptane's decomposition advanced methane's oxidation. • Methane's addition slightly retarded the ignition of pure n-heptane mixture. • The results provided ignition control method for natural-gas/diesel dual-fuel engine. [ABSTRACT FROM AUTHOR]

Submarine groundwater discharge (SGD) has been recognized as an important source of dissolved heavy metals to the coastal ocean. Bohai Bay, the second largest bay of Bohai Sea in China, is subjected to serious environmental problems. However, SGD and SGD-derived heavy metal fluxes in the bay are seldom reported. In this study, we present mass balance models considering the radium losses caused by recirculated seawater to estimate water age, SGD and SGD-derived heavy metal fluxes in Bohai Bay during May 2017. The water age is estimated to be 56.7–85.0 days based on tidal prism model. By combining water and salt mass balance models, submarine fresh groundwater discharge (SFGD) is estimated to be (3.5–9.3) × 107 m3 d−1. The SGD flux estimated by the radium mass balance models is (3.2–7.7) × 108 m3 d−1, an order of magnitude larger than the discharge of the Yellow River during the sampling period. SGD-derived heavy metal fluxes were estimated to be (0.2–6.0) × 107 mol d−1 for Fe, (1.2–2.7) × 107 mol d−1 for Mn, (3.0–8.2) × 105 mol d−1 for Zn, (2.7–7.4) × 104 mol d−1 for Cr and (0.6–1.8) × 103 mol d−1 for Cd, which are significantly higher than those from local rivers. This study reveals that SGD is a significant source of heavy metals (Mn, Zn and Fe) into Bohai Bay, which may have important influences on the metal budgets and ecological environments in coastal areas. Unlabelled Image • SGD was evaluated by coupling radium, salt and water mass balance models. • SGD-derived heavy metal fluxes into Bohai Bay, China were estimated. • SGD was a dominant source of dissolved Mn, Zn and Fe into the bay. [ABSTRACT FROM AUTHOR]