东辽河流域河湖光学吸收特性的季节变化

吸收特性是水体重要的光学特性,也是建立水色反演分析模型的基本参数.本文利用2011年6、9、10月在二龙湖和2012年10月在东辽河的实测数据,通过测定水体营养水平和颗粒物、有色可溶性有机物(CDOM)等光学活性物质的吸收系数,分析了东辽河河湖的光学物质吸收特性和季节变化.结果表明: 二龙湖水体9月处于富营养状态,6月营养水平较低,10月则处于中营养水平;东辽河随采样点位置的差异呈现不同程度的富营养化.水体各组分的吸收系数均随营养水平的增加而逐渐增大.6、10月二龙湖水体总悬浮颗粒物吸收光谱与非色素颗粒物吸收光谱相似,在总吸收中占主导作用的是CDOM;9月总悬浮颗粒物吸收光谱则与浮游植物吸收光谱类似,浮游植物的吸收对总吸收的贡献率最大.6、9月二龙湖浮游植物吸收系数[a_ph(440)]与总磷(TP)呈正相关,6月二龙湖a_ph(440)与溶解有机碳(DOC)呈正相关,非藻类颗粒物吸收系数[a_d(440)]仅与叶绿素a浓度(Chl a)具有相关性.二龙湖(9月)与东辽河a_ph(675)均与Chl a、卡尔森指数(TLI)相关性较好.东辽河流域的河湖水体光学特性存在比较明显的差异:东辽河水体的浮游植物吸收光谱曲线展现出了两种不同类型,浮游植物、非藻类颗粒物、CDOM的贡献率随采样点的不同而相差较大;营养水平较高的9月二龙湖与东辽河水体浮游植物主导了水体光谱吸收,而在二龙湖营养水平较低的月份中(6、10月),颗粒物与CDOM共同主导水体光谱吸收;6月二龙湖与10月东辽河水体CDOM的组成为大分子颗粒物,而9与10月其组成更趋向于小分子颗粒物.     

辽河水体光学吸收特性的季节变化

吸收特性是水体重要的光学特性,也是建立生物光学模型的基本参数。利用2013年5月和9月辽河流域水体实测数据对总悬浮颗粒物、浮游植物、非藻类颗粒物以及有色溶解有机物(CDOM)的吸收特性、季节变化进行了研究。研究表明,总颗粒物的吸收光谱曲线与非藻类颗粒物的吸收光谱基本保持一致并且与非藻类颗粒物的吸收[a_d(λ)]以及浮游植物的吸收[a_(ph)(λ)]都呈现显著相关。两个季节,a_d(440)均是总吸收的主要组成部分,CDOM的吸收[a_(CDOM)(440)]则大于a_(ph)(440)的贡献率,但9月a_d(440)的吸收所占比例较5月高。辽河水体非藻类颗粒物中矿物颗粒物的含量较其他一般水体要高。通过分析5月及9月的aph(440)/a_(ph)(675)发现浮游植物中辅助色素与叶绿素a浓度(Chla)的组成季节性变化不大,但其空间特征表现较为明显。另外,CDOM的吸收特性与非藻类颗粒物的吸收相似,呈现出较大的空间差异性;辽河S_(CDOM)基本小于其它河流、湖泊、河口等水体,其CDOM主要由大分子物质组成。     

中亚热带不同类型米槠林凋落枝溶解性有机质动态及光谱学特性

以中亚热带不同类型米槠林为对象,研究了米槠天然林、次生林和人工林凋落枝在生产量持续增加阶段、高峰阶段、持续减少3种生产阶段溶解性有机质的动态及光谱学特性。结果表明:凋落枝生产阶段和森林类型显著影响米槠凋落枝溶解性有机质含量及光谱学特征。米槠天然林在凋落枝生产量持续减少阶段溶解性有机碳(DOC)含量较高,溶解性有机质在254、260和280 nm处的特征紫外吸光值(SUVA₂₅₄、SUVA₂₆₀、SUVA₂₈₀)较低,表明该阶段天然林凋落枝质量较高,具有较高的以溶解性有机质为载体的物质循环效率。米槠人工林在凋落枝生产量高峰阶段具有较高的总氮(TN)、总磷(TP)、溶解性总氮(TDN)和溶解性总磷(TDP)含量以及较低的DOC∶TDP和TDN∶TDP值,但次生林凋落枝溶解性有机质含量及其光谱学特征在各阶段无显著差异。米槠天然林和次生林凋落枝DOC、TDN和TDP与气温和降水量呈负相关,人工林凋落枝TDN、TDP与气温和降水量呈正相关。人工林凋落枝生产量在高峰阶段具有较高的养分含量,可能具有相对快速的物质循环效率,天然林在凋落枝生产量下降阶段以凋落枝溶解性有机质为载体的物质循环效率相对较高。     

干湿交替对亚热带人工林常见树种凋落物源溶解有机碳数量和特性的影响

在亚热带人工林中，凋落物经常经历干湿交替的现象。本研究选取我国亚热带典型人工林中常见的6种落叶阔叶树、4种常绿阔叶树和2种常绿针叶树的凋落叶作为研究对象，采用40天室内培养试验设置了干旱(维持凋落叶：水的重量比小于20∶1)、湿润(维持凋落叶：水的重量比为1∶1)和干湿交替(干旱4天湿润4天共计5个循环)3个处理，测定了凋落叶源溶解有机碳(DOC)数量和光谱特性(SUVA₂₅₄、SUVA₂₈₀和SUVA₃₅₀值)的变化以及凋落叶质量损失，探究干湿交替对凋落物源DOC数量和特性的影响。结果表明：(1)湿润和干湿交替处理的凋落叶质量损失均显著高于干旱处理，且干湿交替处理凋落叶的质量损失与湿润处理相当；(2)对于落叶和常绿阔叶树而言，干湿交替处理凋落叶产生的DOC总量高于干旱处理，但低于湿润处理；对于常绿针叶树而言，干湿交替处理凋落叶产生的DOC总量均低于干旱处理和湿润处理；(3)在培养期间，干湿交替处理凋落叶源DOC的SUVA₂₅₄、SUVA₂₈₀和SUVA₃₅₀     

亚热带人工林不同植物生长型凋落叶溶解性有机质数量和光谱学特征

凋落叶淋溶过程产生的溶解性有机质(DOM)在森林土壤有机碳和养分循环中发挥着重要作用，然而亚热带不同植物生长型(阔叶、针叶和林下蕨类)淋溶产生的DOM数量、化学组成及结构等基本特征还不明确，尤其缺乏多树种的实验数据。基于此，本研究选取江西省亚热带人工林中常见的11种阔叶树、3种针叶树和4种林下蕨类植物的凋落叶为研究对象，通过室内淋溶试验比较不同植物生长型凋落叶源DOM数量和光谱学特征的差异，并分析DOM数量和光谱结构与凋落叶初始性质的相关性。结果表明：凋落叶淋溶产生的DOM数量和化学组成在植物生长型间存在显著差异，阔叶树凋落叶溶解性有机碳(DOC)和溶解性全氮(DTN)数量最多，而蕨类植物凋落叶的溶解性全磷(DTP)数量最高；阔叶树和蕨类植物凋落叶DOM有更高的SUVA₂₅₄和SUVA₂₈₀值以及更低的S_275-295和S_R值，意味着它们有更高的DOM芳香化程度和更大的分子质量；相关分析和多元线性回归分析结果显示，凋落叶初始元素含量、化学计量比及叶片物理性质(比叶面积、组织密度和饱和持水量)能够很好...     

太湖梅梁湾水体悬浮颗粒物和CDOM的吸收特性

通过测定滤膜上悬浮颗粒物和过滤液中CDOM吸光度的方法计算得到太湖梅梁湾总颗粒物和CDOM的光谱吸收系数,并计算了各吸收组份的贡献份额以及吸收与PAR衰减的比值。总颗粒物的吸收系数从400 nm到600 nm大致呈下降趋势,到675nm附近由于叶绿素a的特征吸收会出现明显峰值,峰值高低随叶绿素a浓度的变化而变化,ap(440)在3.58~9.86 m-1间变化。非藻类颗粒物和CDOM的吸收随波长增加大致按指数规律下降,ad(440)和ag(440)的变化范围分别为2.23~7.07m-1和1.06~1.70 m-1。非藻类颗粒物在400~700 nm波段的指数函数斜率Sd的平均值为(10.91±0.62)μm-1;CDOM在280~500 nm波段指数函数斜率Sg的平均值为(15.52±0.49)μm-1。浮游藻类的光谱吸收表现为在440、675 nm附近存在两个明显的峰值,分别为(2.55±1.14)、(1.34±0.69)m-1。ap(440)与TSS、OSSI、SS均存在显著性正相关,而ad(440)则只与TSSI、SS有显著性相关,aph(440)只与OSS、Chla有显著性相关。CDOM吸收系数与DOC浓度没有显著正相关,但与Chla存在显著幂函数关系,浮游藻类降解产物是水体中CDOM的重要来源之一。水体中物质吸收主要以颗粒物为主,对总吸收的贡献率在70%以上,而颗粒物中又以非藻类颗粒物占主导,一般超过40%,总吸收对漫射衰减的贡献也在40%以上。     

气溶胶光学厚度与PM2.5浓度的时空分布特征及其关系——以京津冀大气污染传输通道城市群为例

城市人口和产业的聚集伴随化石能源消费的迅速增长,导致空气污染物排放量不断增加,对区域气候产生了不可逆的负面影响。以多源遥感数据为基础,对京津冀大气污染传输通道城市群(“2+26”城市群)2015—2019年气溶胶光学厚度(AOD)、PM_2.5浓度的时空分布格局进行分析,从月份、季节、年份三个时间维度定量分析其时空变化规律,并通过计算相关性系数来分析气溶胶光学厚度对PM_2.5浓度的影响。主要得出研究结论如下：(1)PM_2.5浓度整体呈现冬季>春季>秋季>夏季的趋势,并且表现出高度空间自相关性,2015—2019年间,PM_2.5浓度显著下降至40μg/m³以下;(2)AOD平均范围值在0—1之间,总体上呈现春夏季高,秋冬季低的分布特点,到2019年,春夏秋三季AOD浓度呈现明显降低,夏季下降趋势最为显著,AOD同样表现出高度空间自相关性;(3)AOD与PM_2.5浓度存在显著的正相关关系。从季节变化上看,相关性呈现出：秋季>夏季>冬...     

宽幅播种下基本苗密度对小麦旗叶光合特性及叶片和根系衰老的影响

为明确宽幅精播条件下小麦高产高效的适宜基本苗密度,于2018—2019年和2019—2020年在山东兖州大田试验条件下设置4种基本苗密度处理:90×10⁴株·hm^-2(D₁)、180×10⁴株·hm^-2(D₂)、270×10⁴株·hm^-2(山东高产田常用基本苗密度,D₃)、360×10⁴株·hm^-2(D₄),研究基本苗密度对小麦光合特性、衰老特性以及籽粒产量和水分利用效率的影响。结果表明: 与D₁、D₄处理相比,D₂处理显著改善了灌浆期间小麦旗叶光合特性,提高了旗叶和根系超氧化物歧化酶(SOD)活性、可溶性蛋白质含量,降低了旗叶和根系丙二醛(MDA)含量,延缓了旗叶和根系衰老;与D₁、D₃、D₄处理相比,D₂处理显著提高了0~40 cm土层小麦根长、根表面积和根体积。2018—2019年和2019—2020年,与D₁、D₃、D₄处理相比,D₂处理的籽粒产量分别提高11.8%、2.5%、6.4%和22.7%、5.7%、17.1%,水分利用效率分别提高9.2%、8.8%、14.2%和21.1%、6.2%、21.5%。综上,基本苗密度为180×10⁴ 株·hm^-2的D₂处理通过提高小麦灌浆期旗叶光合特性,改善小麦根系形态,延缓了植株衰老,籽粒产量和水分利用效率最高,是山东宽幅播种高产麦田的最优处理。     

林龄对红松和落叶松人工林土壤温室气体通量的影响

探讨人工林发育过程中土壤温室气体排放及其机制,可为森林温室气体通量估算提供理论依据。采用室内培养方法研究了黑龙江省帽儿山地区不同林龄(15、30和50年生)红松(Pinus koraiensis)和落叶松(Larix gmelinii)人工林土壤温室气体排放/吸收速率及其调控因素。结果表明:30年生红松和落叶松人工林土壤CO₂排放速率(红松:(1724.18±98.57)μg C·kg^-1·h^-1;落叶松:(1306.37±142.27)μg C·kg^-1·h^-1)和CH₄吸收速率(红松:(5.12±0.68)μg C·kg^-1·h^-1;落叶松:(1.91±0.85)μg C·kg^-1·h^-1)显著高于15和50年生(P<0.05)。30年生红松人工林土壤N₂O排放速率显著高于15和50年生(P<0.05),而落叶松人工林土壤N₂O排放速率随林龄增加变化不显著。红松和落叶松人工林土壤N₂O排放速率最大值分别为(0.139±0.016)和(0.137±0.056)μg N·kg^-1·h^-1。红松人工林土壤CO₂排放速率均高于同龄落叶松人工林,15和30年生达到显著水平(P<0.05)。红松人工林土壤CH₄吸收速率均显著高于同龄落叶松人工林(P<0.05)。红松人工林土壤N₂O排放速率与同龄落叶松人工林土壤均无显著差异。混合线性模型分析显示,影响红松和落叶松人工林发育过程中土壤CO₂排放速率的主要因素是土壤全碳含量和微生物生物量氮,其中微生物生物量氮受树种和林龄的影响。CH₄吸收速率受到微生物生物量碳、溶解性有机碳和溶解性有机氮含量影响,其中微生物生物量碳受树种和林龄调控。N₂O排放速率受溶解性有机氮、铵态氮和硝态氮影响,其中溶解性有机氮受林龄影响。综上所述,树种和林龄差异造成的土壤理化性质和微生物生物量碳氮的异质性可在一定程度上解释土壤温室气体排放/吸收速率的差异。     

洱海沉水植物的光合特性与分布水深的关系

为研究沉水植物光合特性与其分布水深的关系,选取黑藻(Hydrilla verticillata)、苦草(Vallisneria natans)、水蕴草(Egeria densa)、大茨藻(Najas marina)、微齿眼子菜(Potamogeton maackianus)、光叶眼子菜(Potamogeton lucens)和穿叶眼子菜(Potamogeton perfoliatus)等15种洱海常见沉水植物,测定其光合作用参数。结果表明:光合速率为2.8—18.1μmol O₂/(g DW·h)、暗呼吸速率为0.3—2.0μmol O₂/(g DW·h)、光补偿点为6.3—63.8μE/(m²·s)、光饱和点为55.6—441.5μE/(m²·s),不同沉水植物间光合作用参数存在显著差异。结合洱海全湖沉水植物分布水深调查结果,沉水植物的光补偿点和光饱和点与分布水深呈显著负相关;苦草与其他物种比较具有更低的光补偿点6.3μE/(m²·s)、光饱和点55.6μE/(m^2...     

洱海动态水环境容量模拟研究

基于环境流体动力学模型EFDC (Environmental Fluid Dynamic Code),建立了洱海湖泊及湖湾的三维水动力水质模型。并利用2001－2010 年的气象水文数据对洱海的水动力水质状况进行了连续10 年的数值模拟,模拟结果与实测结果吻合度较好,表明水动力水质模型计算结果较为合理。应用建立的数值模型分析了洱海的水流、水位和水质的时空变化特征,并在此基础上计算分析主要水质因子的动态水环境容量。结果表明,若以地表水二类水标准为规划目标,洱海总氮(TN)、总磷(TP)、COD_Mn和BOD₅ 的平均环境容量分别为1 150、72、12 780 和10 093 吨/年。洱海三维水动力水质模型的建立,为洱海的水环境保护工作提供了一个重要的管理和分析技术平台,对于洱海地区的污染物总量控制具有重要的意义。     

Cytochrome oxidase and its derivatives. VIII. Formation and properties of the ‘oxygenated’ from of cytochrome oxidase and its reconversion to ferrous and ferric oxidase

1. The ‘oxygenated’ compound of cytochrome c oxidase used in our experiments is more stable than the compound of previous reports. It is quantitatively reversible to ferrous oxidase.

2. It is best formed with an excess of O₂ after reduction with a minimum amount of dithionite. It can also be formed at low O₂ tension, but then contains some ferric oxidase.

3. Its formation from ferrocyanide-reduced oxidase remains incomplete and subsequent reduction by dithionite is also incomplete.

4. Cyanide does not inhibit its formation from ferrous oxidase. If only ferricytochrome a but no ferricytochrome a₃ is reduced in the presence of cyanide by dithionite, there is no reaction with O₂.

5. The anaerobic reduction of ‘oxygenated’ oxidase by dithionite is monophasic and fast. In contrast, that of ferric oxidase is biphasic, with an initial fast reduction of ferricytochrome a followed by a much slower reduction of ferricytochrome a₃. The rate of cytochrome a, but not that of cytochrome a₃ reduction depends on dithionite concentration.

6. In the presence of dissolved O₂, the ferric oxidase reduction comes to a temporary standstill when one-third of the absorbance increase at 444 mμ has been reached.

7. Ethyl hydrogen peroxide reacting with ferrous oxidase forms a compound similar to the ‘oxygenated’ compound.

8. Hydrogen donors known to react with peroxidase-H₂O₂ complexes, particularly pyrogallol, accelerate the transformation of ‘oxygenated’ to ferric oxidase, though not at a rate comparable to that of cytochrome c.

9. These results strengthen the evidence for cytochromes a and a₃ but indicate that this difference has disappeared in ‘oxygenated’ oxidase.     

Photobleaching Response of Different Sources of Chromophoric Dissolved Organic Matter Exposed to Natural Solar Radiation Using Absorption and Excitation–Emission Matrix Spectra

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN∶TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN∶TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0–9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%–5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein-like fluorescence substance. Photobleaching was an important driver of CDOM and nutrients biogeochemistry in lake water.     

Spectroscopic characterization and molecular weight distribution of dissolved organic matter in sediment porewaters from Lake Erhai, Southwest China

Dissolved organic matter (DOM) in sediment porewaters from Lake Erhai, Southwest China was investigated using dissolved organic carbon (DOC) concentration, UV absorbance, fluorescence and molecular weight distribution. DOC exhibited a high concentration at the sediment–water interface with a rapid decrease to the oxic–anoxic interface at approximately 7 cm, and then increased with depth. Similar trends were also found for the UV absorption coefficients at 254 and 280 nm in the porewaters. DNA in the sediment was also measured, which confirmed the high abundance of aerobic bacteria in the upper layer of the sediment. Both humic-like (peaks A and C) and protein-like (peaks B and D) fluorescence were observed in the porewater DOM, and their fluorescence intensities exhibited a similar porewater profile as DOC concentration. A strong correlation was found between the peak fluorescence intensity ratio r(A, C) and r(D, B). Both the fluorescence index and UV absorption coefficient at 254 nm suggested a dramatic increase in aromaticity of porewater DOM across the oxic–anoxic interface. Porewater DOM exhibited a multimodal distribution of molecular weight with a relatively low polydispersity. The results of this study offer significant insight into the nature and properties of DOM in freshwater ecosystems.     

'P' solubilization potential of plant growth promoting Pseudomonas mutants at low temperature

Pseudomonas fluorescens strain GRS₁, PRS₉ and their cold tolerant mutants were examined for their tricalcium phosphate (TCP) solubilizing activity in NBRIP (broth) media at 10°C and 25°C. Invariably, all the cold tolerant mutants of GRS₁ and PRS₉ were found more efficient than their respective wild type counterparts for ‘P’ solubilization activity at 10°C as compared to 25°C. ‘P’ solubilization potential of CRM was found maximum among all the strains followed by CRPF₆ and CRPF₄. To the best of out knowledge, this is the first report regarding low temperature ‘P’ solubilization activity.     

ESR characteristics of Photosystem I in deuterium oxide: Further evidence that electron acceptor A1 is a quinone

The appearance of ESR signals from Photosystem I (PS I) electron acceptors A₁ and A₀ in water or deuterium oxide suspension was followed using a low-temperature photoaccumulation technique. In deuterated samples the A₁ signal was narrowed by a factor of 0.66 compared with the control. This effect was fully reversible upon resuspension of treated samples in H₂O. The narrow ESR signal from deuterated A₁ had similar power saturation characteristics to the normal signal; however, a signal from a second component resolved by deuteration was saturated at higher microwave powers than the control. The power saturation behaviour of A⁻₁ in un-modified reaction centres indicated that it is an anionic semiquinone in a ‘protic’ environment. Deuteration reversibly modified the relative extents of reduction of iron sulphur electron acceptors A and B such that centre B became the more stable electron acceptor. The g-value and line-width of iron sulphur centre X was not modified by deuteration although it appeared to become more efficiently reduced. These results are discussed in the light of current evidence from optical, electron spin polarisation and extraction experiments that suggest that A₁ is a quinone, probably vitamin K-1.     

Modeling ecosystem impacts of the invasive Japanese smelt Hypomesus nipponensis in Lake Erhai,southwestern China

Introductions or alien species invasions will induce changes in aquatic ecosystems but are rarely reported in Chinese highland lakes. The Japanese smelt (Hypomesus nipponensis) invaded and has become a dominant fish species in Lake Erhai, a highland lake in southwestern China, since 2016. Here, we engineered Ecopath models for two different periods, 2008–2009 (preinvasion) and 2016–2018 (postinvasion), in Lake Erhai to model ecosystem impacts from the Japanese smelt invasion. In the dynamic Ecosim model based on the 2016–2018 Ecopath model, we ran three 50-year scenarios to simulate the potential effects of Japanese smelts on the system. Our results showed competition between invasive and native species as well as changes in trophic structures, highlighting the impacts of the invasive species over time. The lake ecosystem additionally experienced significant degradation after invasion, mainly reflected in several related indicators, such as total biomass/total system throughput (TB/TST), total primary production/total biomass (TPP/TB), total primary production/total respiration (TPP/TR), Finn's mean path length (FML), Finn's cycling index (FCI) and the Connectance Index (CI). The simulation results indicated that the relative biomass of icefish (Neosalanx taihuensis), bighead carp (Hypophthalmichthys nobilis), sharpbelly (Hemiculter leucisculus), and zooplankton were significantly affected by increasing the strength of the top-down control of the Japanese smelt on its prey. It is also important to do ecological regulation of planktivorous fishes in the studied Lake Erhai, especially the Japanese smelt.