洞庭湖水沙变化分析及影响初探

水沙变化是洞庭湖演变和江湖关系调整的关键因子。综合运用数理统计、小波分析、Mann-Kendall法和累加过滤器等方法,分析1956～2008年洞庭湖入湖和出湖径流和输沙量的变化特征。结果表明:①洞庭湖入湖水量以湘、资、沅、澧四水入流为主,洞庭湖入湖泥沙以荆江三口分沙为主。四水年均入湖水量约占洞庭湖出湖总水量的59.2%;三口入湖沙量约占入湖总沙量的80.9%。②由于荆江裁弯、葛洲坝工程运用、三峡水库拦蓄以及长江上游的水土保持措施的影响,从三口河道进入洞庭湖的水沙呈现明显的衰减趋势,入湖水量所占比重已由荆江裁弯前的42.6%下降到了三峡水库运用初期的21.7%;入湖沙量所占比重已由荆江裁弯前的87.7%下降到了三峡水库运用初期的59.6%。③近50年洞庭湖的泥沙沉积总量达52.9×108t,但泥沙沉积比已由荆江裁弯前的73.3%下降到了三峡水库运用初期的34.0%,洞庭湖泥沙淤积的趋势明显减弱,有利于保持洞庭湖的调洪湖容,延长洞庭湖的寿命;但三峡水库运用初期,三口分流的衰减将加剧洞庭湖区西部地区枯水供水的紧张态势,并使水环境容量下降;同时城陵矶下游长江河道的淤积导致洞庭湖洪水位抬升。     

洱海富营养化影响因素分析

水质富营养化评价表明,洱海现属中营养水平,根据全年平均状态下的某些单项指标评分或近年来某些时段的全湖营养类型综合评分,将洱海评价为从中营养状态向营养营养状态过渡型的湖泊可能更为适宜。与历史资料相比,８０年代至今富营养化进程料快,主要营养盐守趋势。     

青海湖流域50年来(1956-2007年)河川径流量变化趋势——以布哈河和沙柳河为例

通过对青海湖流域布哈河和沙柳河50年来的河川径流量分析发现,布哈河和沙柳河年径流量50年来没有显著的变化趋势,这两条河流的河川径流量对青海湖水位下降所起的作用不明显;布哈河月平均流量的年际变化在1月、2月和3月有减少的趋势,沙柳河月平均流量的年际变化在1月、2月、4月和5月亦有减少的趋势;布哈河的径流量大于沙柳河的径流量,在55%-91%频率范围内,布哈河的径流量小于沙柳河的径流量,在其它频率范围内,布哈河的径流量显著大于沙柳河的径流量,在一年中,布哈河和沙柳河的月径流量具有显著的差异;布哈河来水丰沛期是20世纪60年代,贫乏期是90年代,70和80年代为平水期;沙柳河月径流量从20世纪60年代到90年代一直比较稳定,没有发生显著的变化.     

滇池沉水植物生长过程对间隙水氮、磷时空变化的影响

2015年6-10月通过原位采集滇池沉水植物分布区和无植物对照区柱状沉积物间隙水,分析其溶解性总氮(DTN)和溶解性总磷(DTP)、溶解性无机氮(DIN)和溶解性无机磷(DIP)及溶解性有机氮(DON)和溶解性有机磷(DOP)浓度的时空变化,探讨沉水植物分布对间隙水氮、磷浓度、形态贡献及氮磷比的影响.结果表明:滇池沉水植物生长过程显著影响间隙水氮、磷浓度.与无植物对照区相比,沉水植物生长过程对间隙水氮浓度的削减主要发生在6、8月,而对间隙水磷浓度的削减主要发生在7月,反映了沉水植物对氮、磷两种元素的生物地球化学循环作用机制不同;间隙水氮形态贡献受季节性影响较大,6-7月以DON贡献为主,沉水植物分布区和无植物对照区分别达到61%和84%;而8-10月以DIN贡献为主,沉水植物分布区和无植物对照区分别为76%和75%;沉水植物分布区磷形态贡献随季节波动变化,沉水植物分布区以DOP贡献为主(63%),无植物对照区以DIP贡献为主(62%);沉水植物生长对沉积物间隙水各形态氮磷比影响显著.沉水植物生长显著增加间隙水DTN/DTP比,尤其是DIN/DIP比,相反降低DON/DOP比.沉水植物对间隙水氮、磷吸收及转化过程改变了沉积物氮、磷释放机制,从而影响上覆水氮、磷组成及氮磷比,很可能会影响到浮游植物生长及藻类水华过程,这对于湖泊水质管理具有重要意义.     

湖泊水情遥感研究进展

湖泊作为最直接的淡水资源之一,在人类的生产、生活各方面都占据至关重要的地位.受到全球气候变化与人类活动的影响,湖泊正在发生急剧变化,因而有必要对其进行快速、准确的时空变化监测,从而为水资源管理与保护、未来气候变化预警提供依据.遥感技术的产生与发展为大范围、实时动态的湖泊变化监测提供了难得的契机,它克服了人类对湖泊实地考察的局限性.本文对现有国内外湖泊水情遥感监测技术与方法进行了综合梳理,主要综述了国内外在湖泊水域范围提取、湖泊水位提取、湖泊水量估算、流域水文过程等方面的遥感研究进展情况,重点总结了该领域近年来提出的新方法和新技术.最后,结合当前遥感技术的发展,对未来遥感在湖泊动态变化监测中的应用潜力和趋势进行了简要论述,并对多源遥感数据融合与云计算平台的结合在地表水体连续变化监测中的应用进行了展望.     

Sensitive response of desert vegetation to moisture change based on a near-annual resolution pollen record from Gahai Lake in the Qaidam Basin, northwest China

We present a 50-year pollen record at near-annual resolution from Gahai Lake in the Qaidam Basin on the northeastern Tibetan Plateau. Chronology of a 22-cm short core was established by ²¹⁰Pb and ¹³⁷Cs analysis. The pollen results at 0.5 cm intervals show large changes in Artemisia/Chenopodiaceae (A/C) ratios from < 0.2 to 0.95 in the last 50 years. High (low) A/C ratios represent increase (decrease) in steppe pollen production, which correspond to high (low) relative humidity observed at nearby Delingha weather station. On the basis of good correspondence with instrumental records and carbonate content from Gahai Lake, we conclude that A/C ratio is sensitive to moisture change and can be a very useful index in reconstructing paleoclimate of arid regions. Comparison with pollen and snow accumulation data from Dunde ice core suggests that effective moisture at low and high elevations shows the opposite relationship when mountain precipitation was extremely high, possibly due to topography-induced uplifting and subsiding air dynamics.     

A 16 ka climate record deduced from δ^13C and C/N ratio in Qinghai Lake sediments, northeastern Tibetan Plateau

1 INTRODUCTION δ13C in organic matters from lacustrine sedi- ments varies with several factors including aquatic plants, vegetation type in the catchment, atmos- pheric CO2 concentration, climate (temperature and precipitation), and properties of water, …     

Holocene environmental evolution recorded by core sediments of Judian Lake in the east of Lubei Plain,Shandong Province

Judian Lake in the east of Lubei Plain is located in the monsoon area of northern China,which is sensitive to global climate change and provides abundant lake sedimentary data for the study of the past climate and environment evolution in the land-sea interaction area. Based on the sporopollen identification,grain size analysis and AMS¹⁴C dating of core sediments from the drilling hole of the Judian Lake,the evolutional process of climate and environment since 8900 cal a BP in the northern Lubei Plain was discussed. The results show that: 8900-7625cal a BP,the temperature and precipitation increased and the climate changed from cold-dry to warm-wet;7625—6810 cal a BP,the overall climate was becoming cooler and drier;6810—4435cal a BP,the temperature rose and the precipitation increased,showing an overall warm and humid climate in the middle Holocene;4435—3150cal a BP,the climate was generally cold and humid with some low-amplitude fluctuations of cold and warm. During the middle Holocene,there were two obvious cold and dry events in 5450—5280cal a BP and 4160—4090cal a BP,which was consistent with the geological and climatic records in China and even in the world. It may be due to the southward movement of the equatorial convergence zone caused by the change of solar radiation,the change of ocean surface temperature and the feedback of surface vegetation.     

环境因子及生态补水对乌梁素海“黄苔”年际暴发面积的影响(1986—2021年)

“黄苔”是丝状绿藻大量增殖并漂浮聚集在水面的一种藻类水华,是乌梁素海面临的重大水环境问题之一。本研究基于文献数据整合和Landsat TM/OLI系列卫星影像反演,追溯了乌梁素海近35年(1986—2021年)的水质变化和“黄苔”暴发历程,通过相关性分析和多元线性回归等方法,分析了乌梁素海“黄苔”暴发的年际影响因子。乌梁素海水体化学需氧量、总氮(TN)、总磷(TP)浓度在年尺度上呈下降趋势,但仍处于富营养状态(TLI(∑)>50)。相关性分析结果表明,乌梁素海“黄苔”暴发面积与TP、TN、氨氮、气温呈显著正相关,与出水量、风速、沉水植被面积、入水量呈显著负相关;多元线性回归结果表明,沉水植被面积和出水量是影响乌梁素海“黄苔”暴发面积的主要因子。生态补水工程的实施增加了乌梁素海出入水量,降低了水体TP、TN浓度,也造成沉水植被退化,使“黄苔”暴发的扩张趋势得以遏制。然而,乌梁素海现有营养条件、基质条件仍适宜附着藻生长和“黄苔”暴发。在全球气候变化背景下,气温升高和风力减弱可能会加剧这一现象。建议采取多种措施以防控乌梁素海“黄苔”暴发,如生态补水、外源营养盐管控、沉水植被调控、引水活...