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

SUN Leigang  WANG Shaoqiang  Robert A. MICKLER  CHEN Jinghua  YU Quanzhou  QIAN Zhaohui  ZHOU Guoyi  MENG Ze 《资源与生态学报(英文版)》2019,10(2):112-126

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.  相似文献   

长江中游城市群城市活力水平空间格局及影响因素     

毛炜圣  钟业喜 《世界地理研究》2020,29(1):86-95

地理“大数据”的出现为研究城市问题提供了新的契机。基于兴趣点（POI）和位置服务（LBS）的地理“大数据”，采用空间计量模型、数理统计分析等方法，尝试探讨了长江中游城市群城市活力水平及其影响因素。结果表明：①长江中游城市群城市活力整体处于较低水平，武汉、南昌和长沙中心地位突出，城市群边缘形成片状活力“洼地”的空间格局；②长江中游城市群城市活力与经济发展水平存在耦合关系，低度耦合城市少，较高度耦合和高度耦合城市较多；③高校资源、经济密度、基础设施水平和信息化程度4个因素是影响长江中游城市群城市活力的主要因素，各因素的影响效应具有空间异质性。  相似文献   

长三角工业区夏季近地层臭氧和颗粒物污染相互关系研究   总被引：4，自引：0，他引：4  

邵平  辛金元  安俊琳  王俊秀  吴方堃  吉东生  王跃思 《大气科学》2017,41(3):618-628

利用2013年5月15日到8月31日南京江北工业区（长三角典型工业区）同步的观测资料分析了近地层臭氧（O₃）和细颗粒物（PM_2.5）、气溶胶光学厚度（AOD）的变化特征及相互间的关系,并结合光化学箱模式分析了AOD对近地层O₃生成的影响。结果表明,观测期间PM_2.5平均质量浓度为56.2±20.1 μg m-3;AOD（500 nm）均值为1.4±0.9;波长指数α（440~870 nm）均值为1.0±0.3。PM_2.5质量浓度24 h均值超国家二级标准20.2%,超标时AOD均值增加14.7%,α平均值增加23.9%,O₃体积分数均值减少12.3%。O₃超国家二级标准10.1%,超标时段AOD增加34.9%,α变化不显著。高温低湿条件下,O₃日变化峰值（y）和PM_2.5质量浓度（x）存在较高的线性相关。相对湿度＜60%时,两者拟合曲线为y＝0.97x+43.96（拟合度R2=0.60）,温度＞32°C时,两者拟合方程为y＝1.24x+30.61（R2＝0.64）。夏季长三角工业区呈现高浓度O₃与高浓度PM_2.5叠加的大气复合污染。O₃日变化峰值和AOD变化呈显著负相关。模拟结果显示,O₃日变化峰值（y）和AOD（x）呈现极高的负相关[y＝－34.28x+181.62,R2 = 0.93或y＝220.62·exp (－x/3.17)－19.50,R2＝0.99]。  相似文献   

ROx Budgets and O3 Formation during Summertime at Xianghe Suburban Site in the North China Plain     

Min XUE  Jianzhong MA  Guiqian TANG  Shengrui TONG  Bo HU  Xinran ZHANG  Xinru LI  Yuesi WANG 《大气科学进展》2021,38(7):1209-1222

Photochemical smog characterized by high concentrations of ozone (O3) is a serious air pollution issue in the North China Plain (NCP) region, especially in summer and autumn. For this study, measurements of O3, nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), nitrous acid (HONO), and a number of key physical parameters were taken at a suburban site, Xianghe, in the NCP region during the summer of 2018 in order to better understand the photochemical processes leading to O3 formation and find an optimal way to control O3 pollution. Here, the radical chemistry and O3 photochemical budget based on measurement data from 1-23 July using a chemical box model is investigated. The daytime (0600-1800 LST) average production rate of the primary radicals referred to as ROx (OH + HO2+ RO2) is 3.9 ppbv h-1. HONO photolysis is the largest primary ROx source (41％). Reaction of NO2 + OH is the largest contributor to radical termination (41％), followed by reactions of RO2 + NO2 (26％). The average diurnal maximum O3 production and loss rates are 32.9 ppbv h-1 and 4.3 ppbv h-1, respectively. Sensitivity tests without the HONO constraint lead to decreases in daytime average primary ROx production by 55％ and O3 photochemical production by 42％, highlighting the importance of accurate HONO measurements when quantifying the ROx budget and O3 photochemical production. Considering heterogeneous reactions of trace gases and radicals on aerosols, aerosol uptake of HO2 contributes 11％ to ROx sink, and the daytime average O3 photochemical production decreases by 14％. The O3-NOx-VOCs sensitivity shows that the O3 production at Xianghe during the investigation period is mainly controlled by VOCs.  相似文献   

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde     

Hailiang ZHANG  Yongfu XU  Long JIA  Min XU 《大气科学进展》2021,38(7):1238-1251

Acetaldehyde is one of the important VOC species of O3 precursors in the atmospheric environment. The influences of relative humidity (RH) and initial VOC/NOx ratio (RCN) on the formation of O3 are studied in smog chamber experiments, and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental results. In low-RH conditions (RH= 11.6％±1.1％), the O3 concentration at 6 h increases first and then decreases with the increase of RCN, and the RCN at the inflection point of O3 concentrations is 3.2. In high-RH experiments (RH = 78.8％±1.0％), variation of the O3 concentration at 6 h with RCN is similar to that in low-RH experiments, but the RCN at the inflection point is 2.8. RH has no significant effect on the O3 concentrations under low RCN (< 3), whereas it has a negative effect under high RCN (> 3). Compared with the experimental results, original MCM v3.3.1 greatly underestimates the O3 concentrations. Addition of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO3 on the reactor surface into the original MCM can reduce the difference between the simulated O3 concentrations and the experimental results at 6 h from 24％-35％ and 17％-49％ to 6％-26％ and 10％-42％ under low- and high-RH conditions, respectively. The maximum incremental reactivity (MIR) of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb-1 without considering the effect of other VOCs.  相似文献   

亚甲基蓝在水体系中的光化学降解研究   总被引：1，自引：0，他引：1  

杨桂朋  孙璐霓  周立敏 《中国海洋大学学报(自然科学版)》2009,39(1)

研究水体系中亚甲基蓝的光化学降解.结果表明,在高压汞灯照射下,亚甲基蓝在人工海水中降解得最快,蒸馏水次之,而在天然海水中降解得最慢.通过对比研究发现.重金属离子(Cu2+,Zn2+,Cd2+,Hg2+)和腐殖酸能够在一定程度上抑制亚甲基蓝的光降解;而丙酮能促进亚甲基蓝的光降解.由此可见,重金属离子和腐殖酸可能是造成亚甲基蓝在天然海水中降解缓慢的主要因素之一.  相似文献   

天然水环境中的溶解有机物及其光化学降解对重金属生物可利用性的影响   总被引：1，自引：0，他引：1  

李先国  范晓明  彭学伟  张庆红 《中国海洋大学学报(自然科学版)》2010,40(1)

溶解有机物(DOM)在控制水生生态系统的化学、生物和物理特性中起着重要的作用.DOM不仅能够结合黏土颗粒,而且也能结合对环境和生物有重要影响的Hg,Cu,Pb,Cd,Ni等重金属和有机污染物,从而改变这些物质的迁移、生物可利用性和毒性.本文综述了天然水环境中DOM与重金属的相互作用和对其生物可利用性的影响,并对影响DOM光化学降解的因素及其对重金属生物可利用性的影响做了总结.已有的研究表明:DOM的结构、分子量、浓度、重金属种类、水环境条件等均会影响到DOM与重金属污染物的相互作用;光化学降解会显著改变DOM与重金属的相互作用,从而使其生物可利用性发生变化.  相似文献   

光电化学阴极保护技术研究进展     

蒋继宏  张小影  金祖权 《海洋科学》2021,45(12):150-161

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.  相似文献   

重组藻蓝蛋白与水稻类囊体膜之间光能传递的初步研究     

孙德光  郭雅琳  章峰  尚孟慧  臧晓南  张学成 《海洋湖沼通报》2021,(1):71-76

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。  相似文献   

Photochemical degradation of triadimefon in seawater     

Xiaochun Sun  Guipeng Yang  Xiaoyan Cao  Zhifeng Lin 《中国海洋大学学报(英文版)》2008,7(2):171-176

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.  相似文献