海水中铁(Ⅲ)-氨基酸盐配合物的光化学反应研究

系统研究了高压汞灯模拟日光照射下铁(Ⅲ)-氨基酸盐配合物在天然海水中的光化学反应情况,结果发现,在氨基酸盐配体的存在下,铁(Ⅲ)会发生光化学反应生成还原态的铁(Ⅱ),同时生成的铁(Ⅱ)会被容器内的氧再氧化为铁(Ⅲ).铁(Ⅲ)的光还原反应速率会受到配体浓度、pH和光强以及温度的影响.在氨基酸与铁(Ⅲ)浓度配比大于2的情况下,在铁(Ⅲ)氨基酸盐配合物的光还原反应初期铁(Ⅱ)浓度的增长符合一级动力学反应规律,100min后浓度趋于稳定.光强升高和pH降低都能加快光还原速率,而改变温度则基本上对光还原反应速率无影响,这证明铁(Ⅲ)的光还原反应为一自由基引发的电子转移过程.     

海南岛澄黄滨珊瑚共生藻对环境变化的适应性

在全球气候变暖和人类活动加剧导致珊瑚礁严重衰退的背景下,以抗逆性强的澄黄滨珊瑚（Porites lutea）为研究对象,于 2013 年 10 月―2014 年 8 月在海南岛文昌和三亚对其共生藻密度及光合效率开展了季节性调查研究。结果显示：1）澄黄滨珊瑚共生藻的密度及光合效率均存在显著的季节变化,共生藻密度在冬季最低、夏季较高,其光合效率在冬季较高,春夏季较低。2）澄黄滨珊瑚共生藻密度的空间差异远小于其季节变化的差异,但水深 1~2 m 澄黄滨珊瑚共生藻的密度普遍高于水深 4~6 m 的澄黄滨珊瑚,三亚澄黄滨珊瑚共生藻的光合效率明显高于文昌。3）进一步分析发现,在诸多环境因子中,海表温度 SST 和水体营养是驱动海南岛澄黄滨珊瑚共生藻密度及光合效率变化的主要环境因素,而光合效率的空间差异则可能是珊瑚对生存环境长期驯化的结果。由于文昌和三亚沿岸海水养殖和潜水旅游等人类活动频繁,礁区海水面临富营养化的风险,推测海南岛澄黄滨珊瑚面临 SST 上升和营养胁迫联合效应的严重威胁。     

Lagged response of phytoplanktonic photosynthetic competence to variation of nitrogen concentration in Jiaozhou Bay, China

Fluorescence-based maximal photochemical efficiency, Fv/Fm, is widely used as an indicator to photosynthetic competence in marine systems. It has been considered a useful parameter diagnosing the nutrient stress on phytoplankton photosynthesis, but many studies argue its usefulness. In the present study, we try to find a temporal relationship between Fv/Fm and nitrogen concentration, and provide a possible explanation on the controversy. We continuously measured Fv/Fm and nitrogen concentration once every 10 days from September 2003 to March 2004 at two stations in Jiaozhou Bay, northern China. It was found that Fv/ffm did not significantly correlate to synchronous nitrogen concentration, but the variation （i.e. the change between two adjacent cruises） of nitrogen concentration of the previous cruise and the variation ofFv/Fm of the current cruise were strongly correlated. This result indicates that a time lag exists between the variation of nutrient status and the subsequent Fv/Fm response. Length of the time lag seems just matched the interval of our measurements （10 days）. In the field, direct dependence of Fv/Fm on nitrogen concentration may not be found because of the lagged response of Fv/Fm to nitrogen concentration variations or physiological acclimation. Our results provide a possible way to explain the previously reported conflicting results on the relationship between Fv/Fm and nutrient status. To give a more-accurate estimate about the length of the time lag, an investigation that includes more frequent measurements is needed.     

Ground Based FTIR Measurements of Stratospheric Species from Harestua, Norway During Sesame and Comparison with Models

Vertical columns of HF, HCl, HNO3, ClONO2, N2O, ClO and COF2 were measured at Harestua, Norway (60.22° N, 10.75° E, Elevation 600 a.s.l.) beginning on 24 November 1994 and concluding on 1 May 1995 during Phase-III of the SESAME (Second European Stratospheric Arctic and Mid-latitude Experiment) measurement campaign. The vertical columns of HCl, HNO3 and ClONO2 measured on 81 days were compared with columns calculated by the 3-D Cambridge model SLIMCAT. In addition the results were also interpreted by comparison with a photochemical trajectory model. Good agreement was seen for HCl while the nitrogen compounds showed larger discrepancies, especially for ClONO2. Evidence for chlorine activation was seen with 65% reduction of the chlorine reservoirs (HCl + ClONO2) while the levels of ClO were greatly enhanced. Interpretation of the loss with the trajectory model indicated condensation of chlorine on PSCs. The vertical column ratio of COF2 and HF was measured to 0.21 outside the vortex and a factor of two lower inside. The recovery of ClONO2 was seen to be much faster than that of HCl in the early spring.     

金华地区夏秋大气中过氧乙酰硝酸酯的污染特征

过氧乙酰硝酸酯（PAN）是由VOCs和NO_x的光化学反应生成的一种典型二次污染物,比O₃更适合作为光化学污染的指示剂.2019年6—10月对浙江中部盆地金华市大气中PAN进行了在线监测,并对影响其体积分数变化的因素进行了分析,同时还分析了一次典型的光化学污染过程.结果表明,观测期间PAN的平均体积分数为0.656×10^-9,最高体积分数为4.348×10^-9,日均体积分数水平在0.130×10^-9~2.203×10^-9之间.PAN日变化特征显著,9月为明显的双峰变化,其他月份均为单峰.受气象条件的影响,夏季的污染程度显著低于秋季.9月27—30日典型污染时段内,PAN的小时均值是整个观测期均值的2.8倍,污染以本地积累为主.前体物浓度水平差异与去除机制的不同是影响PAN和O₃相关性的重要因素,此外NO/NO₂的比值是影响PAN生成速率的重要因素,PAN的峰值基本出现在NO/NO₂比值较低的时段.在生成PAN的VOCs物种中,丙烷、乙烷和间/对二甲苯所占比例较大.     

以能量观点研究可见光辐射在大气中的衰减

2004年9月至2006年10月,在华北地区的4个站开展了太阳辐射、气象参数等的综合测量,得到了可见光辐射QVIS、总辐射Q等的变化特征。水汽和散射因子对QVIS/Q有明显的影响,同时对QVIS也有明显的作用。基于能量观点,建立了实际天气QVIS小时累计值(时累)的经验模式,得到了较好的计算结果。水汽因子对于QVIS在大气中的传输有一定的作用,应该给予足够重视。计算表明,华北地区受水汽因子衰减到达地面的QVIS以及占地面QVIS的比例分别为8.78W·m-2和4.24%,受散射因子衰减到达地面的QVIS以及占地面QVIS的比例分别为171.91W·m-2和95.76%。华北地区受水汽因子和散射因子影响损失于大气中的QVIS分别为16.54W·m-2和311.07W·m-2,这一能量损失有季节变化和区域差别。敏感性实验表明,到达地面的QVIS对水汽因子、散射因子的变化有不同的响应,QVIS对散射因子的变化比对水汽因子的变化更为敏感。水汽因子与可见光辐射之间的关系密切,水汽因子项的真正含义应该是大气中的各种物质成分(气、液、固态)对可见光辐射直接和间接(通过化学和光化学反应,包括均相和非均相过程)利用的总和。利用QVIS经验模式计算了大气顶的QVIS,其计算误差为3.5%。在目前及未来研究中,应重视和考虑消耗于大气中的这部分与水汽有关的能量。采用能量观点与实测资料相配合来理解和探索大气中的物理化学过程和规律是一种有效、实用的方法。     

太湖藻源溶解性有机质光化学降解研究

蓝藻水华暴发过程会产生大量的溶解性有机质——藻源溶解性有机质(A-DOM);A-DOM的光化学降解影响其迁移转化和在湖泊中的功能.本研究从太湖藻华中提取A-DOM,利用三维荧光光谱-平行因子分析法(EEMsPARAFAC),研究A-DOM中各组分的光化学降解;再研究不同光照强度、溶解氧浓度、A-DOM浓度、波长对A-DOM的降解的影响.结果显示,A-DOM中含有4种EEMs-PARAFAC组分:C1(UVC类腐殖质)、C2(UVA类腐殖质)、C3(类色氨酸)和C4(类络氨酸),对总荧光强度的贡献比例分别为22.2%、8.6%、68.1%和1.1%.当DOC初始浓度为10 mg/L、反应温度为28℃、pH=8.0时,经500 W汞灯(391.7 W/m~2)光照12 h,A-DOM的总光化学降解率(以a_(355)计)为70.4%;荧光组分C1、C2和C3的降解率分别为96.1%、85.4%和99.2%,三者的光反应性为C3C1C2.条件控制实验显示溶解氧的增加和光强的增强均有助于A-DOM的降解;A-DOM光化学降解主要发生在紫外区,可见光不能使C1和C2得到降解.结果表明A-DOM的光化学降解速度较快,且能通过控制光强、照射光波长和引入溶解氧等条件控制降解速度.实验结果可为湖泊蓝藻水华暴发时的应急处理和保障饮用水安全提供理论依据.     

基于HJ1A数据的沈阳市雾霾时空变化模拟研究

基于HJ1A-CCD数据,采用6S大气辐射传输模型,反演出研究区气溶胶光学厚度。采用偏最小二乘法,基于气溶胶空间分布的估算结果,模拟出研究区PM_(2.5)的空间分布。基于GIS和改进的高斯大气扩散模型,进行了研究区PM_(2.5)的扩散模拟。根据我国PM_(2.5)检测网的空气质量新标准,对沈阳市的雾霾进行等级了划分。     

Responses of maximum photosystem II photochemical efficiency of phytoplankton communities to nutrient limitation in the coastal sea of Qingdao,China

Nutrient enrichment experiments with nitrogen (N) and phosphorus (P) were conducted with samples from two stations in the coastal waters of Qingdao, China, during summer to identify limiting nutrients. In late July of 2009, low P concentrations and the maximum photochemical efficiency of photosystem II (F _v /F _m ) in the initial samples together with F _v /F _m and chlorophyll a (Chl a) responses to P addition indicated P limitation at the two stations. In early August, low P levels still limited phytoplankton growth at station A. F _v /F _m and Chl a were the highest in the NP treatments at station B, suggesting an N/P co-limitation. In mid-September, nutrient concentrations and F _v /F _m were elevated and phytoplankton communities were healthy. Greater F _v /F _m and Chl a in the treatments with added P than those without the addition suggested potential P limitation at station A. Lack of F _v /F _m and Chl a responses following nutrient additions indicated N and P repletion at station B. At the end of July 2010, neither N nor P was limited at station B. Additionally, F _v /F _m coupled with 24-h-long nutrient enrichment experiments can be used to detect P limitation and N/P co-limitation to natural populations. This method can be more accurate for assessing co-limitation than the use of criteria of nutrient concentrations and ratios as indicators, and can provide more rapid results than nutrient addition bioassays using chlorophyll response as an indicator, when a population is potentially limited. Compared with the two conventional methods, the results based on F _v /F _m can also provide more detailed information about physiological states of the populations.