Short-term and diurnal temperature changes alter the response of harmful algal blooms of Pseudo-nitzschia pungens to solar ultraviolet radiation

In this study, we explored the interactive effects of temperature and solar ultraviolet radiation (UVR) on the growth, pigment contents, photochemical efficiency and non-photochemical quenching (NPQ) of Pseudo-nitzschia pungens, which forms harmful algal blooms globally. Cells were first pre-acclimated to temperatures of 20°C, 25°C or 28°C for 10 days. They were then exposed to three different types of solar radiation for 60?min. We then measured the photochemical efficiency of the cells during the 60-min exposure and a 360-min recovery period under dim light (20?μmol?photons?m^?2?s^?1). In addition, we analysed the diural change in photochemical efficiency and NPQ over a 10-h period. We found that P. pungens that were exposed to higher temperatures in the short term (i.e. 20–25°C, 20–28°C and 25–28°C) or long term (i.e. 25–25°C and 28–28°C) exhibited lower levels of photoinhibition and faster recovery rates than samples exposed to a lower temperature (i.e. 20–20°C). This indicated that the deleterious effects of UVR can be minimised by both chronic and acute exposure to higher temperatures within the tolerated temperature range for P. pungens.     

Remote Sensing Indices to Measure the Seasonal Dynamics of Photosynthesis in a Southern China Subtropical Evergreen Forest

The accurate measurement of the dynamics of photosynthesis in China’s subtropical evergreen forest ecosystems is an important contribution to carbon (C) sink estimates in global terrestrial ecosystems and their responses to climate change. Eddy covariance has historically been the only direct method to assess C flux of whole ecosystems with high temporal resolution, but it suffers from limited spatial resolution. During the last decade, continuous global monitoring of plant primary productivity from spectroradiometer sensors on flux towers and satellites has extended the temporal and spatial coverage of C flux observations. In this study, we evaluated the performance of two physiological remote sensing indices, fluorescence reflectance index (FRI) and photochemical reflectance index (PRI), to measure the seasonal variations of photosynthesis in a subtropical evergreen forest ecosystem using continuous canopy spectral and flux measurements in the Dinghushan Nature Reserve in southern China. The more commonly used NDVI has been shown to be saturated and mainly affected by illumination (R²=0.88, p < 0.001), but FRI and PRI could better track the seasonal dynamics of plant photosynthetic functioning by comparison and are less affected by illumination (R²=0.13 and R²=0.51, respectively) at the seasonal scale. FRI correlated better with daily gross primary production (GPP) in the morning hours than in the afternoon hours, in contrast to PRI which correlated better with light-use efficiency (LUE) in the afternoon hours. Both FRI and PRI could show greater correlations with GPP and LUE respectively in the senescence season than in the recovery-growth season. When incident PAR was taken into account, the relationship between GPP and FRI was improved and the correlation coefficient increased from 0.22 to 0.69 (p < 0.001). The strength of the correlation increased significantly in the senescence season (R ²=0.79, p < 0.001). Our results demonstrate the application of FRI and PRI as physiological indices for the accurate measurement of the seasonal dynamics of plant community photosynthesis in a subtropical evergreen forest, and suggest these indices may be applied to carbon cycle models to improve the estimation of regional carbon budgets.     

Photochemical degradation of triadimefon in seawater

The photochemical degradation of triadimefon in seawater was investigated under different reaction conditions in this study. The results showed that triadimefon could be effectively degraded by the irradiation of a high-pressure mercury lamp and the photodegradation rotes were influenced by aquatic media, heavy metal ions and photosensitizers. The photochemical degradation of triadimefon followed the first-order reaction kinetic behavior, with the rate constants ranging from 0.0027 to 0.0128 min-1 under the studied conditions. The photolysis of triadimefon was slower in natural seawater than in distilled water or synthetic seawater. All the heavy metal ions studied in this paper had inhibition effects on the photolysis of triadimefon. Acetone, as a common photosensitizer, could accelerate the photolysis of triadimefon. Three photoproducts were identified by GC-MS analysis. Our study confirmed that photochemical degradation is an effective pathway to remove triadimefon in seawater.     

Dependence of upper atmosphere photochemistry on the shape of the diurnal cycle of the photolysis rates

A photochemical model of the atmosphere constitutes a non–linear, non–autonomous dynamical system, enforced by the Earth’s rotation. Some studies have shown that the region of the mesopause tends towards non–linear responses such as period-doubling cascades and chaos. In these studies, simple approximations for the diurnal variations of the photolysis rates are assumed. The goal of this article is to investigate what happens if the more realistic, calculated photolysis rates are introduced. It is found that, if the usual approximations—sinusoidal and step fiunctions—are assumed, the responses of the system are similar: it converges to a 2–day periodic solution. If the more realistic, calculated diurnal cycle is introduced, a new 4–day subharmonic appear.     

重组藻蓝蛋白与水稻类囊体膜之间光能传递的初步研究

为了研究藻蓝蛋白和高等植物类囊体膜之间的光能传递,本实验将诱导表达的重组藻蓝蛋白和水稻类囊体混合孵育后,检测其77K荧光发射光谱以及类囊体膜的电子传递速率和光化学量子产量,结果表明重组藻蓝蛋白和水稻类囊体膜光系统Ⅰ之间存在能量传递使得光化学量子产量提高.本研究为利用藻胆蛋白构建新型光合系统提供了理论基础和实验依据.     

二甲基硫的海洋化学研究

二甲基硫（ＤＭＳ） 是海洋排放到大气中的最主要的生源硫化物。作者综述了ＤＭＳ在海洋中的分布特征、影响ＤＭＳ转化的因素、ＤＭＳ的海空扩散及其对环境的影响等。ＤＭＳ在海洋中存在很大程度的时空变化,这一变化不仅与海洋初级生产力水平有关,而且还与浮游植物的种类组成密切相关。微生物的降解、光化学的氧化以及海空扩散是ＤＭＳ在海洋中迁移变化的三个最重要的途径。ＤＭＳ的海－ 空扩散也存在较大的时空变化。ＤＭＳ的释放会对全球的气候变化和酸雨的形成产生重要的影响。本文同时就国内外的研究现状和今后的研究方向进行了分析和总结。     

光电化学阴极保护技术研究进展

海洋环境下的金属面临着非常严峻的腐蚀问题,必须采取措施进行防护.光电化学阴极保护是一种绿色环保的新型防腐蚀技术,受到了广泛的关注.本文简要阐述了光电化学阴极保护技术的原理以及对光阳极的要求;详细介绍了以二氧化钛为代表的几种常见光阳极材料及其不同改性方法;此外还介绍了兼具储能与阴极保护功能的光阳极,它有望实现暗态下连续保护的目标;最后讨论了光电化学阴极保护技术的发展趋势.     

Impact of Accurate Photolysis Calculations on the Simulation of Stratospheric Chemistry

The interpretation of atmospheric measurements and the forecasting of the atmospheric composition require a hierarchy of accurate chemical transport and global circulation models. Here, the results of studies using Bremens Atmospheric Photochemical Model (BRAPHO) are presented. The focus of this study is given to the calculation of the atmospheric photolysis frequencies It is shown that the spectral high resolved simulation of the O₂ Schumann–Runge bands leads to differences in the order of 10% in the calculated O₂ photolysis frequency when compared with parameterizations used in other atmospheric models. Detailed treatment of the NO absorption leads to even larger differences (in the order of 50%) compared to standard parameterizations. Refraction leads to a significant increase in the photolysis frequencies at large solar zenith angles and, under polar spring conditions, to a significant change in the nighttime mixing ratio of some trace gases, e.g., NO₃. It appears that recent changes in some important rate constants significantly alter the simulated BrO_x- and HO_x-budgets in the mid-latitude stratosphere.     

Doppler Detection of Hydroxyl Column Abundance in the Middle Atmosphere: 2. Measurement for Three Years and Comparison with a 1D Model

The hydroxyl column abundance in the middle atmosphere is measured for 3 years in Tokyo by ground-based uv absorption spectroscopy utilizing the Doppler shift of the solar spectrum due to the solar rotation. The diurnal and seasonal variations of the measured column abundance are found to be reproduced qualitatively by a one-dimensional photochemical-diffusive model; however, the measured column abundances are smaller than the calculated by 20 to 30% systematically.     

Study of ozone “weekend effect” in Shanghai

Analysis of observed ozone data in 2006 from five monitoring sites (Xujiahui, Chongming, Baoshan, Pudong, Jinshan) in Shanghai reveals that ozone (O_3) concentrations in Xujiahui are higher at week-ends than those on weekdays, despite the fact that emissions of ozone precursor substances, such as oxides of nitrogen (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs) are lower at weekends than those on weekdays. The possible chemical cause of ozone "weekend effect" is that NO_2/NO ratio increases at weekends by 25.61% compared with those on weekdays. In addition, because of an average 12.13% reduction in NOx (NO NO_2) in the early morning (05:00-09:00) at weekends compared with that on weekdays, the ozone inhibition period ends 0.5 h earlier at weekends resulting in the longer duration of ozone accumulation and the higher ozone production rate. The rate of ozone production is a function of VOCs and NOx in the atmosphere. VOCs/NOx ratio in Xujiahui is 4.55 at weekends, and 4.37 on weekdays, belonging to the "NOx-limited". The increasing VOCs/NOx ratio at weekends leads to ozone enhancement from 73 ppbv to 80 ppbv, which are consistent with ozone "weekend effect" in Xujiahui. Furthermore, combining with MICAPS cloud amount data, the fact that ozone "weekend effect" in Xujiahui weakens gradually along with the increasing of cloud amount indicates that ozone photochemical production leads to ozone "weekend effect" in Xujiahui of Shanghai.