藻型湖区氧化亚氮排放特征及其影响因素

湖泊等内陆水体是大气N₂O潜在的重要排放源,也是全球N₂O收支估算的重要组成部分。目前全球湖泊普遍面临富营养化和蓝藻暴发等问题,明晰藻型湖泊N₂O排放强度及其环境影响因子对准确估算湖泊N₂O排放和预测其未来变化至关重要。本研究选择太湖藻型湖区为研究对象,同时选取人为活动影响较小的湖心区作为对比区域,基于2011年8月至2013年8月为期2年的逐月连续观测,探讨藻型湖区N₂O排放特征及其影响因素。结果表明,藻型湖区呈现极强的N₂O排放,其排放通量为(4.88±3.05) mmol/(m²·d),是参考区域(湖心:(2.10±4.31) mmol/(m²·d))的2倍多。此外,在藻型湖区中不同点位N₂O排放差异显著,受河流外源输入影响,近岸区是N₂O的热点排放区,其年均排放通量高达10.93 mmol/(m²·d)。连续观测表明N₂     

Methane and nitrous oxide fluxes in the polluted Adyar River and estuary, SE India

We measured dissolved N(2)O, CH(4), O(2), NH(4)(+), NO(3)(-) and NO(2)(-) on 7 transects along the polluted Adyar River-estuary, SE India and estimated N(2)O and CH(4) emissions using a gas exchange relation and a floating chamber. High NO(2)(-) implied some nitrification of a large anthropogenic NH(4)(+) pool. In the lower catchment CH(4) was maximal (6.3+/-4.3 x 10(4)nM), exceeding the ebullition threshold, whereas strong undersaturation of N(2)O and O(2) implied intense denitrification. Emissions fluxes for the whole Adyar system approximately 2.5 x 10(8) g CH(4)yr(-1) and approximately 2.4 x 10(6)gN(2)O yr(-1) estimated with a gas exchange relation and approximately 2 x 10(9) g CH(4)yr(-1) derived with a floating chamber illustrate the importance of CH(4) ebullition. An equivalent CO(2) flux approximately 1-10 x 10(10)gy r(-1) derived using global warming potentials is equivalent to total Chennai motor vehicle CO(2) emissions in one month. Studies such as this may inform more effective waste management and future compliance with international emissions agreements.     

基于SWAT模型的南四湖流域非点源氮磷污染模拟

本文利用SWAT模型结合实测数据,对南四湖流域2001-2010年年均非点源氮磷污染进行模拟,分析了南四湖流域非点源氮磷负荷空间分布特征,计算各河流流域对南四湖湖区污染的贡献率,并对非点源氮磷污染严重的关键区进行识别.研究表明:(1)先模拟湖东和湖西的两个典型小流域的非点源氮磷污染,并将模型推及整个南四湖流域,该方法不仅提高了计算效率,且得到了较好的模拟结果.通过对比发现,湖东的模拟效果要好于湖西,一定程度上说明SWAT模型在起伏较大的地区能取得更高的精度.(2)南四湖流域非点源氮磷污染严重,几乎所有区域的氮负荷超标,40%以上的区域磷负荷超标严重.湖东非点源氮磷污染较湖西严重,其中洸府河流域是南四湖湖区非点源氮磷污染的主要贡献者.(3)通过对径流量、泥沙负荷、氮负荷、磷负荷的相关分析可以得出,南四湖流域非点源氮负荷以溶解态为主,随径流进入水体;非点源磷负荷以吸附态为主,随泥沙进入水体.     

云南阳宗海大气氮、磷沉降特征

大气氮、磷沉降是湖泊水体氮、磷入湖的重要途径之一.为了解阳宗海氮、磷沉降对湖泊富营养化的潜在影响,于2012年5月-2014年4月通过监测阳宗海大气氮、磷沉降,估算氮、磷的大气沉降通量,揭示阳宗海大气氮、磷沉降随时间变化的特征,分析其来源、影响因素等.由于阳宗海是磷限制湖泊,本研究在估算大气氮、磷沉降通量的基础上,特别比较了大气磷沉降入湖量与非点源磷的入湖量,以此评估大气沉降输入磷对湖泊富营养化的潜在影响.研究结果表明:阳宗海总氮年平均沉降通量为248 mg/m~2,春、夏、秋和冬季平均分别为200、306、274和214 mg/m~2,其中夏季沉降通量最大,原因与降雨量增加有关;总磷年平均沉降通量为24 mg/m~2,春、夏、秋和冬季平均分别为18、31、19和27 mg/m~2.大气磷沉降与输入阳宗海的总磷量相比很小,对阳宗海富营养化影响较小.     

Simulating estuarine nitrous oxide production by means of a dynamic model

We describe a dynamic model developed from a commercially available modeling package (ECoS-III) to simulate estuarine dissolved inorganic nitrogen (DIN) dynamics, and consequent N(2)O production and atmospheric flux on the timescale of tidal cycles. Simulated model state variables were NH(4)(+), NO(3)(-) and N(2)O concentrations, and salinity. Model outputs were evaluated through comparison with summer field data for the Tyne estuary, UK. The model adequately reproduced the observed axial profiles of NH(4)(+), NO(3)(-) and N(2)O concentrations. Nitrification was shown to be the dominant N(2)O source and estimates of the ratios nitrification to DIN load and N(2)O emission to DIN load are considerably lower than the corresponding values adopted in global scale models of estuarine N(2)O emissions based on DIN transformations. Hence our results are consistent with the requirement imposed by atmospheric N(2)O growth rate constraints that the amount of atmospheric N(2)O arising from agriculturally related sources, including estuarine transformations of N, be revised downward.     

Ice cover,landscape setting,and geological framework of Lake Vostok,East Antarctica

Lake Vostok, located beneath more than 4 km of ice in the middle of East Antarctica, is a unique subglacial habitat and may contain microorganisms with distinct adaptations to such an extreme environment. Melting and freezing at the base of the ice sheet, which slowly flows across the lake, controls the flux of water, biota and sediment particles through the lake. The influx of thermal energy, however, is limited to contributions from below. Thus the geological origin of Lake Vostok is a critical boundary condition for the subglacial ecosystem. We present the first comprehensive maps of ice surface, ice thickness and subglacial topography around Lake Vostok. The ice flow across the lake and the landscape setting are closely linked to the geological origin of Lake Vostok. Our data show that Lake Vostok is located along a major geological boundary. Magnetic and gravity data are distinct east and west of the lake, as is the roughness of the subglacial topography. The physiographic setting of the lake has important consequences for the ice flow and thus the melting and freezing pattern and the lake’s circulation. Lake Vostok is a tectonically controlled subglacial lake. The tectonic processes provided the space for a unique habitat and recent minor tectonic activity could have the potential to introduce small, but significant amounts of thermal energy into the lake.     

Oxygen budget of a perennially ice-covered Antarctic lake

A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as ice by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. Based on these results we suggest that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.     

“引江济太”对2016年后太湖总磷反弹的直接影响分析

针对“引江济太”工程将总磷浓度偏高的长江水引入太湖后对2016年后太湖总磷反弹的影响,本文实测并收集整理了2016年前后“引江济太”调水入湖水量、磷通量及全太湖入湖水量、磷通量与太湖磷存量等数据,对2016年前后“引江济太”调水入湖水量、磷通量、磷形态与其他入湖河道水量、磷通量、磷形态以及全太湖的水质、受水区贡湖的水质进行了分析.结果表明：2016年前后,“引江济太”年均入湖磷通量为97.56 t,年均入湖水量为8.16亿m³,从调水量、入湖磷通量、调水后短期磷响应及各湖区磷增量来看,“引江济太”与2016年后太湖总磷反弹相关性不强.“引江济太”调水累计入湖磷通量为877.97 t,占太湖总入湖磷通量的4.58%,累计入湖水量占太湖累计入湖水量的7.36%,单位水量携带的磷通量仅为其他来水的一半左右,占比相对有限.与太湖主要入湖河流相比,“引江济太”调水属于优质来水,湖泊的入湖河流总磷浓度一般都高于湖泊本身的总磷浓度,“引江济太”调水总磷浓度偏高属于正常范围.目前“引江济太”工程在保证供水安全、缓解水华危机的同时对处于严重富营养化状态的太湖具有一定的改善效果,但未来引水量增加的情况下,必须继续关注引水带来的磷通量与太湖磷循环系统的关系,确保“引江济太”对太湖继续产生良性的影响.     

大气湿沉降向太湖水生生态系统输送氮的初步估算

测定和分析了2002年7月至2003年6月太湖周边地区太湖站、拖山岛、东山站、无锡、苏州、湖州、常州等7个站点大气降水化学组成,计算了水气界面TN、NH4 -N、NO3--N、T1N、TON的湿沉降率。结果表明,大气降水的TN浓度变化范围为2.06±0.30(常州)-3.71±0.43(拖山岛),太湖流域大气降水已呈富营养化水质的特征;大气降水TN、NH4 -N、NO3--N、TIN、TON的年均湿沉降率分别为2806.75kg/km2、1458.81kg/km2、631.67kg/km2、2090.48kg/km2和716.28kg/km2;每年由湿沉降直接进入太湖水体的TN约为6562.2t,NH4 -N为3410.7t,NO3--N为1476.8t,TIN为4887.5t,TON为1674.7t;TN占入湖河道年输入污染物总量的13.6%.大气湿沉降中,TIN对TN的贡献比较大,平均约占TN的78.78%.TIN的湿沉降率具有季节性分布,夏季高,春季次之,冬秋季低。这种现象无疑对太湖水体的蓝藻爆发和富营养化具有潜在的促进作用.     

特大洪水对浅水湖泊磷的影响:以2016年太湖为例

2016年太湖发生特大洪水,水位达到历史第二,入湖水量比平均年多60.8亿m³.而从2016年开始太湖磷指标改变了2010年以来平缓下降的趋势出现回升,也就是出现所谓“磷反弹”的问题.为了研究磷反弹和特大洪水之间的关系,本研究从2016年入湖水量、水质、磷通量、水中磷存量以及磷在太湖中的迁移过程出发,对大洪水前后太湖磷的变化进行分析.结果表明：洪水期间入湖河道带来大量的磷是引起磷反弹的主要原因.由于洪水的影响,2016年磷净入湖通量比往年平均水平多出579.2 t,约达到1683.0 t.其中,两次洪水贡献极大,约占全年水平的50%（6-7月和10月的洪水分别带入580.5和268.2 t磷）.磷反弹的另一个原因在于太湖存在较高的磷滞留率,磷在入湖后很难经由出湖河道排出.从入湖后磷的归趋上看,洪水过程中高磷浓度水块尽管存在由太湖西北部向东、南部迁移的过程,但途中水体磷浓度出现显著降低（即滞留现象）,导致高磷浓度水块未能到达出湖排泄区（太浦港、望虞河等）.全年净入湖磷通量中仅有小部分（205.3 t）直接引起水体磷浓度上升,而其余的大部分则滞留于底泥之中,明显高于往年水平.2016年滞留在太湖内的磷很可能破坏了往年底泥-上覆水的磷平衡,对后续水质的变化产生间接的影响.     

Nutrient Budgets,Dynamics and Storm Effects in a Eutrophic,Stratified Baltic Lake

Between 1989 and 1998 the small eutrophic stratified Lake Belau was investigated intensively and multidisciplinarily. This article is a short, comprehensive summary and re‐evaluation of the hydrochemistry of the lake, with focus on nitrogen and phosphorus. In several aspects the lake can be regarded as a typical example of the glacial north German lakes. The 1960's and 1970's are characterised by heavy nutrient inputs and fast eutrophication. During the last two decades the external nutrient load, especially the phosphorus load into Lake Belau was significantly reduced. But phosphorus‐rich sediments and large areas with summerly anoxic sediment surface conditions cause intensive release of phosphorus from older deeper sediment layers. Annual budgets reveal that despite an average sediment accumulation of 3 mm a^?1 the lake has lost its function as net phosphorus sink and it is very likely that internal eutrophication by the sediments will keep the lake in its eutrophic state during the next decades. Despite that, monthly budgets of five vertical layers show that the main phosphorus supplier for the phosphorus depleted epilimnion during summer is the creek Alte Schwentine. The annual nitrogen budget indicates groundwater and interflow water as well as atmospheric input as additional important nitrogen sources. 36% (98 μmol m ^?2 h^?1 N) of all nitrogen input is lost to atmosphere mainly due to denitrification. The example of a heavy storm shows that about 10% of the annual nitrogen loss to the atmosphere can take place during a single day and in form of ammonia. The storm further made obvious that these unpredictable events can have strong impact on nutrient cycling and ecology in Lake Belau and the lake can become an unexpected nutrient source for downstream systems.     

不同强度冷空气对太湖水热交换的定量影响

作为冷季主要的天气事件,冷空气过境会改变湖泊上方的气团性质,对湖泊的水热通量产生影响,进而影响湖泊的生物物理和化学过程.以亚热带大型浅水湖泊——太湖为研究对象,基于2012-2017年5个冷季（11月-翌年3月）的太湖中尺度通量网观测数据,量化不同强度冷空气（寒潮、强冷空气和较强冷空气）对太湖水热通量的影响.结果表明：在5个冷季中,寒潮、强冷空气和较强冷空气发生的总次数分别为4、11和33次,累积持续天数分别为14、31和78天.冷空气过境显著增强太湖的水热通量,3种冷空气过境使太湖的感热通量分别增至无冷空气时的10.3、6.0和4.3倍,潜热通量分别增至无冷空气时的4.0、2.1和2.7倍.虽然冷空气影响天数仅占冷季天数的16.4%,但对整个冷季的潜热和感热通量贡献分别为34.9%和51.7%,以较强冷空气贡献最大.冷空气影响时,水-气界面的温度梯度是太湖感热通量的主控因子,而潜热通量的主控因子为风速.与深水湖泊相比,太湖等浅水湖泊对冷空气过境的响应更快,寒潮过境时尤为明显.     

太湖鱼类产量、组成的变动规律及与环境的关系

湖泊生态系统健康包含两个方面的内涵:满足人类社会合理要求的能力和湖泊生态系统自我维持与更新的能力.获知湖泊生态系统健康状况及其区域分异特征,对于湖泊管理具有重要意义.本文基于对太湖的野外调查,计算了表征湖泊生态系统健康的系统能、系统能结构、生态缓冲容量和湖泊营养状态指数.聚类分析结果表明,太湖不同湖区生态系统健康状况存在一定差异,东部湖区较好,西部湖区较差,呈现由东南部湖区向西北部湖区递减的趋势.该结果对进一步研究湖泊生态系统健康评价指标阈值具有重要的参考意义.     

基于实测与模拟的青海湖冰厚时空变化特征

湖冰厚度是湖泊在封冻期的重要物理参数,明晰其时空变化特征对于认识气候变暖背景下的湖冰响应规律具有重要的理论价值和现实意义.基于ERA5 Climate Reanalysis气温数据集、MODIS MOD09GQ数据产品和2019年湖冰钻孔测厚数据及雷达测厚数据,重建2000—2019年青海湖冰厚时间序列并分析其时空变化特征.结果表明:①2019年3月实测青海湖湖冰厚度平均增长速率为0.30 cm/d,高于2月份(0.12 cm/d).基于度日法湖冰生长模型模拟的2018年11月—2019年3月青海湖冰厚平均增长速率为0.34 cm/d,与实际观测数据相比,模拟冰厚误差为±2 cm,但在河流入湖口处和湖区南侧误差较大,且冰厚模拟数值在3月中旬前高估而之后有所低估.②青海湖多年平均冰厚介于32～37 cm,其中2008—2016年湖冰厚度年际变化剧烈,呈现先增大再稳定后减小的趋势.冻结初期湖冰厚度增长迅速,12月和1月湖冰增长速率分别为0.45和0.41 cm/d,2月后冰厚增长速率放缓,2月和3月分别为0.29和0.14 cm/d.③2000—2019年冰厚整体呈现北厚南薄、东厚西薄的空间格局,多年冰厚变化幅度湖区西部较东部稳定,湖冰平均厚度与完全封冻时长及封冻期呈正相关.     

ESTIMATION OF LAKE EVAPORATION FROM A SHALLOW LAKE IN CENTRAL SWEDEN BY OXYGEN-18

Lake evaporation has been estimated for a shallow lake using a combination of water and isotope mass balance, accounting for the isotopic non-steady state of lake water. The main feature of the isotope method is that inflows need not be measured. Knowledge of their isotopic content is sufficient. Oxygen-18 content, i.e. (δ¹⁸O), of lake water, inflows and outflow was measured on a weekly basis, whereas for precipitation it was monitored daily. The discharge from the lake was also recorded daily. Lake water level, relative humidity, air, and lake water surface temperatures were recorded by a logger. The weather data were recorded on a small island in the lake. It was observed that the lake is isotopically well mixed. Furthermore, the atmospheric moisture was not always in isotopic equilibrium with the precipitation. Daily lake evaporation was estimated as an average of six to eight days depending upon the field logistics. Lake evaporation varied from 0.6 to about 5.4 mm/day during the experimental period. It was found that evaporation estimates are very sensitive to small variations in δ¹⁸O of lake evaporate. Induced changes of 10% in δ¹⁸O of lake evaporate caused errors in evaporation estimates of 9–31%, while similar induced changes in δ¹⁸O of inflows caused errors of 8–18%. Thus, an accurate experimental determination of δ¹⁸O of lake evaporate is relatively more important.     

Sudden enhancement of sedimentation flux of~(210)Pb_(ex) as anindicator of lake productivity as exemplified by Lake Chenghai

Recent sediments in lakes and gulfs are a sensi-tive recorder of the information about environmentalchanges in the catchment areas during recent geologi-cal history. Precise determination of the ages of sedi-ments is the key to deciphering the environmental re-cords. The 210Pb dating technique and the markertechnique based on fallout radionuclide 137Cs havefound wide applications in sedimentation rate on atime scale of several tens to one hundred years, as wellas the varve chron…     

青海湖最近25年变化的遥感调查与研究

青海湖是我国最大的内陆水体,它及其流域的生态环境近来一直倍受广泛关注．其水位下降、湖水面积缩小、湖体分离等更是研究的热点问题．本文针对这些问题展开遥感调查与研究,收集了多时相、多种信息源的影像数据;分析了1975年至2000年25年以来湖泊的变迁及成因,湖岸变化及湖体分离状况;用遥感方法反推25年以来湖水位的变化;计算了1975、2000年两个年份的湖水面积,并遥感分析了湖水面积萎缩的原因．此外,对青海湖进行了实地调查与水深测量,建立了该湖泊水深反演模型．     

Flocculation: a key process in the sediment flux of a large,glacier‐fed lake

This study investigates the consequences of flocculation for sediment flux in glacier‐fed Lillooet Lake, British Columbia based on density, fractal dimension, in situ profiles of sediment concentration and size distribution, and settling velocity equations presented in the literature. Sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake, equivalent to at least one‐quarter of the average annual sediment flux. Fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains. This flux varies both spatially and temporally over the observation period, suggesting a link between deposition via flocculation and the properties of bottom sediments. Macrofloc flux increased through June, reached a peak during July, and then declined into August. Macrofloc flux was greatest in the distal end of the first basin, approximately 10 km from the point of inflow. Relatively high excess densities (～0·1 g cm^–3 at 500 µm) for flocs in situ are consistent with a composition dominated by inorganic primary particles. Microlaminations within Lillooet Lake varves have been linked by earlier workers to discharge events, and the action of turbidity currents, emanating from the Lillooet River. While turbidity currents undoubtedly occur in Lillooet Lake, these results demonstrate flocculation as an adjunct process linking discharge, lake level, macrofloc flux, bulk density and microlaminations. In situ measurements of sediment settling velocity in glacier‐fed lakes are required to better constrain flux rates, and permit comparison between flocculation in lacustrine environments with existing studies of estuarine, marine and fluvial flocculation. Copyright © 2009 John Wiley & Sons, Ltd.     

Luminescence chronology for late Quaternary lake levels of enclosed Huangqihai lake in East Asian monsoon marginal area in northern China

Lake level fluctuations of closed lakes in monsoonal regions are direct indicators of regional moisture variability related to the intensity of monsoon activities. In the current study, quartz OSL dating was applied to construct the chronology of two sedimentary sequences from the east and west shores of Huangqihai Lake in the East Asian monsoon area, and the history of lake level fluctuations during the late Quaternary was established. In the current study, we present field investigation findings of highstands of >87 m above the modern lake in enclosed Huangqihai Lake in northern China, and also use luminescence dating to establish the timing for the highstands. We conclude that: (1) Lake highstands occurred during both MIS 5 (>87 m above the modern lake) and early Holocene (∼9–8 ka, >54 m above the modern lake), (2) No highstands were observed for MIS 3 and MIS 2 during which loess has accumulated indicative of much drier climate; (3) The evolution of lakes in East Asian monsoon marginal area (e.g. Huangqihai Lake) is linked with the monsoon variation.     

Evaluation of Gravity and Aeromagnetic Anomalies for the Deep Structure and Possibility of Hydrocarbon Potential of the Region Surrounding Lake Van,Eastern Anatolia,Turkey

The North Anatolian Fault (NAF) is not observed on the surface beyond 40 km southeast of Karliova town toward the western shoreline of Lake Van. Various amplitudes of gravity and aeromagnetic anomalies are observed around the lake and surrounding region. In the gravity anomaly map, contour intensity is observed from the north of Mus city center toward Lake Van. There is a possibility that the NAF extends from here to the lake. Because there is no gravity data within the lake, the extension of the NAF is unknown and uncertain in the lake and to the east. Meanwhile, it is observed from the aeromagnetic anomalies that there are several positive and negative amplitude anomalies aligned around a slightly curved line in the east–west direction. The same curvature becomes much clearer in the analytic signal transformation map. The volcanic mountains of Nemrut and Suphan, and magnetic anomalies to the east of the Lake Van are all lined up and extended with this slightly curved line, provoking thoughts that a fault zone that was not previously mapped may exist. The epicenter of the major earthquake event that occurred on October 23, 2011 is located on this fault zone. The fault plane solution of this earthquake indicates a thrust fault in the east–west direction, consistent with the results of this study. Volcanic mountains in this zone are accepted as still being active because of gas seepages from their calderas, and magnetic anomalies are caused by buried causative bodies, probably magmatic intrusions. Because of its magmatic nature, this zone could be a good prospect for geothermal energy exploration. In this study, the basement of the Van Basin was also modelled three-dimensionally (3D) in order to investigate its hydrocarbon potential, because the first oil production in Anatolia was recorded around the Kurzot village in this basin. According to the 3D modelling results, the basin is composed of three different depressions aligned in the N–S direction and many prospective structures were observed between and around these depressions where the depocenter depths may reach down to 10 km.