2011年4—10月我国主要暴雨天气过程简述

利用MICAPS系统日降水资料和常规天气图资料,以1981 —2010 年30 a 平均降水量为气候态,统计了2011 年4—10 月我国的主要暴雨天气过程,并对各主要暴雨过程的影响系统、出现时段、范围及累积降水量进行概述。统计结果表明,2011 年4—10 月我国共出现172 个暴雨日、125 次区域性暴雨,38 次主要暴雨天气过程。汛期主要气候特点是,长江中下游春季干旱,6 月暴雨频繁,部分地区旱涝急转;夏秋季西南、江南伏秋旱严重;9 月华西秋汛显著;9 月底至10月中,海南、两广暴雨强烈。     

桂林漓江水体溶解无机碳迁移与水生光合碳固定研究

河流溶解无机碳含量昼夜变化主要受碳酸盐反向沉积、水生光合利用和脱气作用控制,被水生光合利用的溶解无机碳是岩溶碳汇的组成部分,脱气作用比例的大小是影响碳汇稳定性的决定因素。本文以漓江中游省里—冠岩之间15 km长河段为研究对象,开展昼夜高分辨率水化学自动化监测与高频取样,分析水生植物光合作用利用HCO3-1及相关钙沉降过程。结果表明,监测河段水生光合利用的无机碳转化通量为859 kgC?d-1,单位流程光合作用溶解无机碳转化量和钙沉降量分别为2.06 t?（d?km）-1和0.78 t?（d?km）-1。光合作用与钙沉降消耗DIC约占总转化量的70 %,以光合有机碳和CaCO3形式储存于河床,成为岩溶碳汇组成部分。无机碳转化量约占输入DIC总量的6.0 %（其中1.7%以CO2形式返回大气）,说明夏季低水位期间强烈的水生植物光合利用溶解无机碳,可有效遏制白天水气界面CO2脱气过程发生,低脱气比例证实漓江水体的溶解无机碳还是比较稳定的。     

桂林潮田河水溶解无机碳昼夜变化与通量

小型山区河流系统具有流域面积小、响应时间短、人类活动的水化学影响易识别等特点,是研究生物地球化学过程的理想场所.本文以桂林潮田河为例,通过高分辨率监测与高频取样,研究水化学昼夜动态变化,无机碳移除及其生物地球化学控制机理.受水生光合作用与钙沉积作用的控制,河水pH、DO、SpC、HCO–3和Ca2+离子产生显著的昼夜动态变化,这些水化学指标昼夜变幅大小又与河床基质和水生植物类型有关.砾石类河床藻类发育的鸟岭桥河段Ca2+和HCO3-含量白天下降幅度平均值分别为12%和11%,泥质类河床沉水植物发育的两河沟河段为10.6%和8.9%.DO浓度与pH值主要受局地河流内部过程控制,即水生植物或藻类光合作用控制,而电导率受上游传输影响较大,滞后时间与两点之间信号平流传输时间相关.监测河段水体因光合作用产生的钙沉降与溶解无机碳移除量分别为302 kg/d和997 kg/d,即188.75 g/m/d和623.13 g/m/d,是西南亚热带典型地下河出口河流的4~5倍,小型岩溶河流沿流程发生的无机碳向有机碳转化,对水体碳通量而言,是真正意义上的自然碳汇过程.     

杭州人工湿地与西溪湿地4种植物光合生理生态比较

比较了夏季杭州植物园观鱼池人工湿地和西溪湿地的4种植物,鸢尾(Iris tectorum)、菖蒲(Acorus cala-mus)、美人蕉(Canna indica)和旱柳(Salix matsudana)的生理生态差异。测定了植物的光饱和曲线,蒸腾速率(Tr),计算了表观光量子效率(AQY)、水分利用效率(WUE)和呼吸速率(Rd)等生理参数。研究发现,夏季人工湿地植物的生长状态优于西溪湿地的植物,最大光合速率和蒸腾速率都是人工湿地大于西溪湿地,而呼吸速率则是西溪湿地大于人工湿地。人工湿地为净化鱼池水的沙基质结构以及间歇式供水条件在净化富营养化水的同时也为其中生长的植物创造了好于自然湿地的生长环境。     

大气CO2浓度升高及气候变化对作物冠层光合影响的数值模拟

利用美国Licor-6200光合作用测定仪,对黄淮海地区代表性冬小麦品种鲁麦23号叶片光合作用速率进行了较为全面的测定,分别确定了冬小麦叶片光—光合作用响应曲线和CO₂—光合作用响应曲线,在此基础上,建立了叶片光合作用模式,并进而建立了一个具有瞬时时间尺度,空间积分为叶片尺度的冬小麦冠层模式,利用模式分别分析了大气中CO₂浓度升高和温度变化对冠层光合作用的不同影响,并在此基础上进一步进行了综合数值分析。单因子分析表明:晴天状况下,冠层光合速率随CO₂浓度升高而上升,当CO₂浓度由330×10^-6上升至660×10^-6时,冠层光合日总量可增加19.7%;冠层光合速率随辐射增加而增大,辐射量增加10.0%,冠层光合日总量可增加6.7%;冠层光合速率随温度升高而下降,温度升高1℃,冠层光合日总量减少2.9%。多因子综合数值分析表明:在辐射量较大的气候背景下,冠层光合日总量对温度和CO₂变化响应更加敏感。本文的实测数据为研究气候变化对中国农业影响提供了最基本的可靠模型参数,冠层光合模型为未来改进作物模型提供了理论基础。     

Metabolised Tritium and Radiocarbon in Lichens and Their Use as Biomonitors

Lichens are now well known for their potential as bio-indicators of environmental pollution, but less is known about their suitability as quantitative biomonitors for atmospheric emissions of tritium (mainly as tritiated water, HTO) and radiocarbon (as ¹⁴CO₂) from nuclear facilities, although both radionuclides could result in non-trivial individual or collective radiation doses due to their high environmental mobility and their long half-lives. ³H and ¹⁴C are fixed in lichens mainly by the photosynthesis of the algal partner and then stored in the organic molecules of both alga and fungus. They have the advantage of allowing the monitoring of atmospheric water vapour without interference of soil water or soil organic substances as long as soil-inhabiting species are avoided. Lichens were collected in the surroundings of (military and civil) nuclear facilities, in areas away from any direct source of contamination and some were transplanted from a contaminated area to a non-contaminated one. The influence of the nuclear facilities can be clearly traced, sometimes in a spectacular way and the first results of analyses after transplants give a base for estimating the effective half-life of ³H in lichens.     

我国几种热带海藻的光合作用与光量子通量密度的关系

本文介绍用氧电极法测定海南岛潮下带产的凤尾菜Gracilaria eucheumoides等6种热带红藻和无肋马尾藻Sargassum enerve等3种热带褐藻的光合活性和光量子通量密度的关系。研究结果表明:1.红藻和褐藻的补偿点差别不大,9种热带海藻的光合作用补偿点都在24—28μE/(m~2·s)之间,而光合作用饱和点上的净光合作用速率为0.18—0.66mgO_2/(g鲜重·h),一般而言,红藻的较低,褐藻的较高;2.各种热带海藻的光合作用饱和点的差异,其规律也符合一般海藻的垂直分布规律;3.对人工栽培的凤尾菜、琼枝Eucheuma gelatinae卡帕藻Kappaphycus alvarezii等,可以扩大生长水层,在更深一些的水层中栽培,这对发展生产是非常有利的。     

Dynamics of phosphorus exchange between sediment and water in a gravel-bed river

ABSTRACT

Phosphorus (P) stores in gravel-bed rivers are released for uptake by periphyton when pH levels exceed 8.5. The Tukituki River has low alkalinity water and frequently experiences periphyton blooms, and daytime pH?>?9 during summer low-flows. We measured dissolved reactive P (DRP) and EPC₀, the water concentration of DRP at which no net release or sorption from the river bed occurs, in sediment samples from the Tukituki River subject to controlled pH levels before (2014) and after (2017) changes to two wastewater discharges that reduced P release to the river by 95%. DRP released from 2014 sediments at pH 8.5–10 were 30?±?10?mg/m³ above background (pH 8) whereas those released from 2017 sediments were 5?±?3?mg/m³ above background. EPC₀ levels in 2014 and 2017 were 11?±?6 and 7?±?2?mg/m³, respectively. Field estimates of released DRP calculated from continuous pH and the Redfield equation suggested that most of the readily available DRP released from sediments at elevated pH is derived from material attached to recently deposited sediment. Subsequently, a reduction in wastewater inputs or agricultural runoff should reduce sediment DRP stores, and hence sediment fluxes, within a few years and mitigate periphyton blooms in addition to directly lowering water column concentrations.     

Effects of CO<Subscript>2</Subscript> Enrichment on Marine Phytoplankton

Rising atmospheric CO₂ and deliberate CO₂ sequestration in the ocean change seawater carbonate chemistry in a similar way, lowering seawater pH, carbonate ion concentration and carbonate saturation state and increasing dissolved CO₂ concentration. These changes affect marine plankton in various ways. On the organismal level, a moderate increase in CO₂ facilitates photosynthetic carbon fixation of some phytoplankton groups. It also enhances the release of dissolved carbohydrates, most notably during the decline of nutrient-limited phytoplankton blooms. A decrease in the carbonate saturation state represses biogenic calcification of the predominant marine calcifying organisms, foraminifera and coccolithophorids. On the ecosystem level these responses influence phytoplankton species composition and succession, favouring algal species which predominantly rely on CO₂ utilization. Increased phytoplankton exudation promotes particle aggregation and marine snow formation, enhancing the vertical flux of biogenic material. A decrease in calcification may affect the competitive advantage of calcifying organisms, with possible impacts on their distribution and abundance. On the biogeochemical level, biological responses to CO₂ enrichment and the related changes in carbonate chemistry can strongly alter the cycling of carbon and other bio-active elements in the ocean. Both decreasing calcification and enhanced carbon overproduction due to release of extracellular carbohydrates have the potential to increase the CO₂ storage capacity of the ocean. Although the significance of such biological responses to CO₂ enrichment becomes increasingly evident, our ability to make reliable predictions of their future developments and to quantify their potential ecological and biogeochemical impacts is still in its infancy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Trophic Potential and Photoecology of Endolithic Algae Living within Coral Skeletons

Abstract. The biomass of the endolithic algae Ostreobium quekettii Phyllosiphoniaceae living within skeletons of the scleractinans Mycedium elephantotus and Leptoseris fragilis averages 300 μg protein. cm^-2. This represents approximately 7% of the protein of the zooxanthekie-containing tissue of M. elephantotus and approximately 38% of that of L. fragilis. Oxygen production Pmax_net of 0. querkettii in bare skeletons of M. elephantotus averaged 0.7 μg O₂.cm^-2· h^-1 measured in large skeletal fragments. This amount is approximately 6% of the productivity of the zooxanthellae Symbiodinium microadriaticum living in the same scleractinian species at the same depth Pmax_net 11 μg O₂· Cm^-2· h^-1. Light compensation of O. quekettii - within skeletons - was reached at approximately 10 and saturation at 35 40 μE·m^-2· s^-1. Algae within the M. elephantotus skeletons receive a maximum of 4–6% of the ambient irradiance, which is approximately 0.9 μE · m^-2· s^-1 approximately 0.04% surface irradiance at a depth of 88 m. In L. fragilis at a depth of 145 m, the photon flux decreases to 0.3 μE·m^-2· s^-1, which is less than 0.004% of surface intensity. With increasing depth, the ratio of Chl b to Chl a increased in endolithic algae colonizing L. fragilis, indicating improvement of light harvesting under low light conditions. In free-living O. quekettii cultured at irradiance levels from 0.5–60 μE·m^-2· s^-1, the concentrations of chlorophylls increased and that of siphonein and β-carotene decreased with decreasing photon flux.