The heterogeneous formation of N2O in air containing NO2, O3 and NH3

In a nighttime system and under relatively dry conditions (about 15 ppm H₂O), the reaction mixture of NO₂, O₃, and NH₃ in purified air turns out to result in the formation of nitrous oxide (N₂O). The experiments were performed in a continuous stirred flow reactor, in the concentration region of 0.02–2 ppm.N₂O is thought to arise through the heterogeneous reaction of gaseous N₂O₅ and absorbed NH₃ at the wall of the reaction vessel % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaatCvAUfKttLeary% qr1ngBPrgaiuaacqWFOaakcqWFobGtcqWFibasdaWgaaWcbaGae83m% amdabeaakiab-LcaPmaaBaaaleaacqWFHbqyaeqaaOGaey4kaSIaai% ikaiab-5eaonaaBaaaleaacqWFYaGmaeqaaOGae83ta80aaSbaaSqa% aiab-vda1aqabaGccaGGPaWaaSbaaSqaaiaadEgaaeqaaOGaeyOKH4% Qae8Nta40aaSbaaSqaaiab-jdaYaqabaGccqWFpbWtcqGHRaWkcqWF% ibascqWFobGtcqWFpbWtdaWgaaWcbaGae83mamdabeaakiabgUcaRi% ab-HeainaaBaaaleaacqWFYaGmaeqaaOGae83ta8eaaa!59AC!\[(NH_3 )_a + (N_2 O_5 )_g \to N_2 O + HNO_3 + H_2 O\]In principle, there is competition between this reaction and that of adsorbed H₂O with N₂O₅, resulting in the formation of HNO₃. At high water concentrations (RH>75%), no formation of N₂O was found. Although the rate constant of adsorbed NH₃ with gaseous N₂O₅ is much larger than that of the reaction of adsorbed H₂O with gaseous N₂O₅, the significance of the observed N₂O formation for the outside atmosphere is thought to be dependent on the adsorption properties of H₂O and NH₃ on a surface. A number of NH₃ and H₂O adsorption measurements on several materials are discussed.     

2,3-Dimethylbiphenyl: Kinetics of its cyclisation reaction and effects of maturation upon its relative concentration in sediments

The rate constants of the cyclisation reaction of 2,3-dimethylbiphenyl to give 1-methylfluorene under non-catalytic conditions have been obtained at five temperatures between 460 and 500°C. The activation energy, activation entropy and frequency factor for the reaction have been determined from the experimental data. These kinetic parameters were then used to calculate the temperature ranges where the reaction occurs under natural conditions in sedimentary sequences which have experienced different heating rates. The coincidence of the measured and calculated values has been taken as evidence that the cyclisation reaction occurs in sediments under non-catalytic conditions.     

Kinetic investigation of the OH + CH3Br reaction between 248 and 390 K

The rate parameters for the reaction of the OH radical with CH₃Br have been measured using the discharge flow-electron paramagnetic resonance method. The result isk ₁=(1.86±0.48)×10^–12 exp[–(1230±150)/T] cm³ molecule^–1 s^–1. This value is compared to earlier data and is found to be in excellent agreement with the most recent results, which greatly increases the accuracy of the ozone depletion potential of CH₃Br which can be derived from these kinetic data.     

GEOCHEMICAL KINETIC SIMULATION ON WALL—ROCK ALTERATION ZONING IN THE BAOBAN GOLD FIELD，SOUTH CHINA

The Baoban gold field,located in the area of Hainan Island ,South China ,bears three gold de-posits :Tuwaishan ,Baoban ,and Erjia ,which belong to the wall-rock alteration type.In terms of the petrography data,four alteration zones can be recognized from the ore-vein outwards(1)the silicification zone;(2)the sericitization zone;(3)the chloritization zone;and (4)the calcitization zone.The geochemical kinetic simulation was carried out on sericitization and chloritization .Results of the study showed that the formation of the alteration zones is connected with the properties of hydrothermal fluids:the initial concentration of Al (O H)3,the diffusion coefficient and the velocity of fluid flow.The alteration zones in this field are the result of multiple interaction between hydrothermal fluids and wall rocks.     

电解质水溶液的结构

本文叙述了盐湖中主要离子Ｌｉ＋、Ｎａ＋、Ｋ＋、Ｍｇ２＋、Ｃａ２＋、Ｃｌ－、ＳＯ＿４￣２－、ＮＯ＿３和纯水的结构，介绍了主要研究方法Ｘ射线衍射．分析了溶液结构研究历史和现状，对溶液结构研究的未来进行了展望．     

溶液结构的X射线衍射研究—1实验技术

本文介绍了Ｘ射线衍射法测定液体结构的一些实验技术，包括光源波长和稳定性、单色Ｘ射线的获得、测量条件的选择、实验数据的校正等。     

Percolation theory as a tool for imitation of fracture process in rocks

The statistical models of earthquake focal processes covering topological, kinetic, energetic and scaling aspects of the phenomenon are considered on the basis of the percolation and reliability theories. It is shown that these models do not contradict the basic experimental data of physics of fracture and seismology. Some predictive signs are also considered.     

Heating rate effects on aromatic maturity indicators

Aromatic maturity indicators based upon dimethylnaphthalenes, trimethylnaphthalenes and methylphenanthrenes have been determined for two sedimentary sequences from northwest Western Australia. The rate of change of these indicators with depth has been modelled using a kinetic expression which accounts for the effects of continuously varying time and temperature. Activation energies and entropies of activation have been measured. Maturity indicators with similar and with very different kinetic parameters have been used to construct plots to illustrate their behaviours under a variety of thermal regimes. Maturity indicators with similar activation energies behave almost identically over a wide range of heating rates while those with substantial differences display more diverse behaviour. The former may be used to relate kerogen-based maturity indicators with those determined from crude oils, whereas the latter can provide information about the maximum palaeotemperatures and heating rates of sedimentary hydrocarbons. It was also observed that the kinetic parameters for particular aromatic maturity indicators differed between the two sedimentary sequences, suggesting that source and mineral matrix effects can influence their behaviour.     

Soil carbon dioxide and weathering potentials in tropical karst terrain,peninsular Malaysia: A preliminary model

CO₂ concentrations at depths of 15,30, and 50 cm were determined over a one-year period in six karst soils in the Malay peninsula. Evidence suggests that the highest single CO₂ value (MAXCO₂, per cent) recorded at each site/depth provides the best estimate of conditions during groundwater recharge events. Soil depth (cm) and bulk density (BDEN) are the best predictors of MAXCO₂, with the equation loglo(MAXCO₂) = 1·146 (BDEN) + 0·00698 (DEPTH) - 1·227 accounting for 86 per cent of the variation. This equation is used to model MAXCO₂ at seven, more remote sites. Soil throughflow patterns and groundwater recharge points are estimated from slope pantometer and soil depth surveys in order to assess the CO₂ concentration with which soil waters ultimately equilibrate before entering the limestone. Limestone weathering seems to be predominantly of the open system type, the overall mean MAXCO₂ of 1·65 per cent corresponding with a weathering potential of 167 ppm CaCO₃. Weathering potentials vary markedly, ranging from 62–82 ppm on rocky hilltops to more than 280 ppm on certain tower karst footslopes in Selangor and the Kinta Valley and on moderate hillslopes developed in impure limestones in the Boundary Range.     

Analysis of chlorophyll diagenesis—II. Solvent effects on metal incorporation into chlorophyll diagenetic products

We are attempting to quantify selected transitions in the diagenetic pathway of chlorophyll in deep ocean sediments. To analyze the aromatization from phorbides (less stable) to porphyrins (more stable), we used a model system which closely resembles the compounds identified in oceanic sediments. Kinetic parameters were determined for the incorporation of copper into deoxomesopyropheophorbide a methyl ester (DOMPP) and deoxophylloerythrin methyl ester (DPE) in a series of solvents ranging from highly polar and protic to non-polar and aprotic, representing varying sedimentary environments. In the reaction of copper with these two compounds, the activation parameters for the reaction with DOMPP indicate that DOMPP is more sensitive to the environment than DPE. Also, over the temperature range studied, DOMPP always reacted faster than DPE under similar conditions. These two observations lend support to our previous hypothesis that the phorbide to porphyrin transition includes the metallophorbide as a short-lived intermediate in the reaction sequence.