Rate Constants for Reaction Between Hydroxyl Radical and Dimethyl Sulfide Under Real Atmospheric Condition

The rate constants of the reaction between hydroxyl radical （OH-） and dimethyl sulfide （DMS） were investigated by using the relative methods in air, N2, and 02. Strong influences of ground state oxygen O（3p） on DMS consumption were found by the photolysis of HONO and CH3ONO as OH. sources, and the rate constants obtained in these systems varied significantly. The rate constants of the reaction between DMS and OH- （generated by photolysis of H2 O2） at room temperature were 8.56 × 10^-12, 11.31× 10^-12, and 4.50× 10^-12 cm3/（molecule.s）, in air, O2, and N2, respectively. The temperature dependence of the rate constants for OH- with DMS over the temperature range of 287-338 K was also investigated in nitrogen and air, and the Arrhenius expression was obtained as follows： kaire=（7.24±0.28）× 10^-13exp[（770.7±E97.2）/T], kN2 =（3.40±0.15） × 10^-11 exp[-- （590.3±165.9）/T].

Adjustment of oxygen vacancy states in ZnO and its application in ppb-level NO2 gas sensor

Oxygen vacancy(VO)is long believed as a key factor influencing the gas sensing properties.However,the concentration of VO is generally focused while the VOstate is neglected,which masks the inherent mechanism of gas sensor.Using a post annealing process,the influence of VO states on the response of ZnO nanofilm to NO2 gas is investigated in this study.The systematical analysis of the results obtained by different methods indicates a transformation of VO from the neutral to the doubly ionized state during post annealing treatment.The results also imply that the gas sensing properties is not directly correlated with the VO concentration.And due to the competitive adsorption of ambient O2,the neutral VO is majorly occupied by the adsorbed O2 while the VO in doubly ionized state can promote the adsorption of NO2.Consequently,the transition of VO from the neutral to the doubly ionized state can lead to a dramatic increase of the response to NO2,from 733 to 3.34×10^4 for 100 ppm NO2.Guided by this mechanism,NO2 gas sensing in ppb-level is also achieved:the response reaches 165%to 25 ppb(0.025 ppm)NO2 with a good repeatability.

Exploring seasonal acidification in the Yellow Sea

The Yellow Sea on the western continental margin of the North Pacific Ocean is of major ecological and economic importance. Four field surveys were conducted during May and November 2012, August 2015, and January 2016, investigating seasonal variations in dissolved oxygen and carbonate system parameters of this marginal sea. Results showed that the Yellow Sea cold water mass accumulated respiration-induced CO_2 in subsurface and bottom waters in summer and autumn, leading to acidified seawaters with critical carbonate saturation states of aragonite(Ω_(arag)) of less than 1.5. These seriously acidified seawaters occupied one third of surveyed areas in summer and autumn, likely affecting local calcified organisms and benthic communities. In a future scenario for the 2050 s, in which the atmospheric CO_2 mole fraction increases by 100 μmol mol-1, half of the Yellow Sea benthos would be seasonally covered by acidified seawater having a critical Ω_(arag) of less than 1.5. The corresponding bottom-water p H_T would be around 7.85 in summer, and 7.80 in autumn. Of the China seas, the Yellow Sea cold water mass represents one of the ecosystems most vulnerable to ocean acidification.