Patterns and Trends in Southern Ontario Lake ice Phenology

An analysis is presented of 46 ice break up and 15 ice free season phenology data series obtained largely through volunteer monitoring efforts in Southern Ontario. Observations spanned the years 1853–2001. Available data included dates of ice formation and ice break up as well as the number of ice free days in a year. A high degree of temporal coherence in ice phenology between lakes was observed (137/365 pairwise correlations significant at P<0.05). Significant monotonic trends towards earlier break up dates and longer ice free seasons were observed across the region both in the entire series and in the last thirty years of data. Trends in longer series may be associated with the end of the Little Ice Age. The significantly longer ice free seasons and earlier ice break up dates observed in the study area have important implications for lakes in other parts of Canada where climate change effects are predicted to be more extreme than in South-Central Ontario.     

Consequences and Correctives Related to Lake Acidification, Liming and Mercury in Fish – A Case-Study for Lake Huljesjön, Sweden, Using the LakeWeb-model

This work exemplifies how a given lake (Lake Huljesjön, Sweden) would likely respond to changes in pH-values and to liming (a standard measure against anthropogenic acidification). The basic questions are: How would a liming influence pH? How long would the changes last? How would the changes influence the structure and function of lake ecosystems? The work uses a comprehensive lake ecosystem model, LakeWeb, which accounts for production, biomasses, predation, abiotic/biotic interactions of nine key functional groups of organisms, phytoplankton, bacterioplankton, two types of zooplankton (herbivorous and predatory), two types of fish (prey and predatory), zoobenthos, macrophytes and benthic algae. LakeWeb is a dynamic model and gives weekly variations. It has been critically tested using empirical data and regressions from many lakes. Those tests are not presented here but have shown that the model can capture typical functional and structural patterns in lakes very well. This gives credibility to the results presented in this work, which would be very costly to obtain in the traditional manner by extensive field studies in one or a few lakes. This work presents for the first time predictions at the ecosystem level of how functional groups of organisms (and not individual species) are likely to respond to acidification and liming. Two existing dynamic models, one for liming, the other for Hg-concentrations in fish, have been added to the LakeWeb-model. These two models have previously been tested and proven to yield good predictions. The results presented here indicate that there are several probable changes in the structure and function of the lake foodweb related to acidification and liming. The predicted changes in macrophyte cover will influence the predation pressure on fish, and thereby the fish biomass. Reductions in primary production at low pH-values will cause reductions in fish biomass. There are several interesting compensatory effects between factors that increase fish biomass and factors that tend to decrease the biomass. Such matters can be handled quantitatively by the LakeWeb-model.     

湖泊营养物参照状态建立方法研究

建立生态分区内各类型湖泊营养物的参照状态是营养物基准制定过程中最为核心的内容之一。在系统分析和评价国外确定湖泊营养物参照状态的若干种方法,包括参照湖泊法、湖泊群体分布法、三分法、回归分析等几种统计学方法以及模型推断和古湖沼学重建方法后,文章根据总磷（total phosphorus,TP）、总氮（total nitrogen,TN）、叶绿素a（chlorophyll a,Chl-a）和塞氏透明度（Secci depth）等四项指标的历史监测数据,应用若干统计学方法建立了巢湖的营养物基准参照状态。通过互相之间的比较分析以及长江中下游湖区古湖沼学重建数据的验证,推荐采用湖泊群体分布法5％点位对应的值作为巢湖营养物基准的参照状态。因此,巢湖营养物参照状态阈值范围为总磷0．023～0．27mg·L^-1,总氮O．62～0．63mg·L^-1,叶绿素aO．65～0．67mg·m^-1,塞氏透明度0．65-0．72m。     

内蒙古若干江湖水体中铜的表观络合容量

本文对内蒙古若干江湖水样中天然配体与铜的表观络合容量进行了阳极溶出伏安法测定，并计算总条件稳定常数和络合容量指数。实验表明，富集电位，ｐＨ值，碳酸根对络合容量的测定影响不同；天然ｐＨ值下，铜的表观络合容量为呼伦湖最大，乌梁素海最小，其余水样相近。     

Speciation study of trace elements in surface sediment of Winam Gulf,Lake Victoria,by sequential extraction,aqua-regia acid digestion,and ICP-OES

The speciation of trace metals in surface sediment in Kisumu Carwash area of Winam Gulf, was studied and results compared with those found at Usoma beach which was found to be several orders of magnitude less polluted. High proportions of the metals were bioavailable (fractions 1–6) with BA% ranging from 21.7% (Al) to 94.5% (Pb) at Carwash and 19.6% (Al) to ～100% (for Cd and Pb) at Usoma beach. The readily mobilizable fraction (fractions 1–4) decreased in the order: Pb > Mn > Sn > Cu > Co > Zn > Mg > Cd > Mo > Ni > Cr > Fe > Al at Carwash and Mn > Mo > Sn > Pb > Cd > Mg > Cu > Zn > Co > Ni > Fe > Cr > Al at Usoma beach. The total Zn, Cd, Cr, and Cu sediment concentrations at Carwash were higher than the threshold effect concentrations (TECs), although their bioavailable concentrations were lower than these limits. Both the total and bioavailable concentrations of Pb in surface sediment at Kisumu Carwash area were higher than the TEC threshold limit indicating significant contamination from this heavy metal. Although there was a general good agreement on data obtained by sequential extraction as compared with those obtained by direct aqua-regia digestion, there were large discrepancies for some specific metal analytes which could be accounted for in terms of analytical variations and lack of uniformity in physical and chemical composition of the sediment samples analyzed.     

四川绵竹清平乡文家沟“8·13”特大泥石流灾害

2010年8月13日四川绵竹市清平乡文家沟暴发特大规模泥石流灾害(简称"8.13"特大泥石流)。在野外调查的基础上,分析了此次泥石流灾害的特征,并从其形成条件入手,探讨了此次灾害的成因和未来发展趋势。文家沟流域在2010年8月12日16时至13日04时的降雨量达227 mm,暴雨形成强大洪水冲刷流域内在地震期间形成的滑坡-碎屑流堆积体,并形成高容重粘性泥石流。泥石流依次冲毁沟内19座谷坊和1座拦挡坝,冲出总量达429.3×104 m3,完全堵断绵远河,形成长约1 650 m、宽约420 m、高约12 m的堰塞坝,堰塞湖回水长1.5 km。泥石流共造成6人死亡或失踪,379间房屋被冲毁掩埋,汉(旺)清(平)公路中断,2座桥梁被毁。研究表明,松散物质的极大丰富和堵溃是导致"8.13"特大泥石流规模巨大的主要原因;文家沟在短期内泥石流仍会频发,但规模要比"8.13"泥石流小。     

基于直觉模糊距离法的堰塞湖减灾方案选优

针对堰塞湖减灾群决策信息的不确定性与模糊性,为解决不完全信息条件下属性指标及专家之间存在的相互关联群决策问题,综合运用直觉模糊集理论、海明距离原理和熵权理论,将直觉模糊距离群决策方法运用到堰塞湖减灾决策过程中。工程实例研究表明,运用直觉模糊距离法决策出的最优方案具有较高的区分度和敏感性,增强了决策的客观性、科学性,能为堰塞湖减灾决策提供更为可靠的依据,具有较强的实用价值。     

古洪水研究途径及其在减灾中的作用

本文根据史料记载特点,提出了古洪水鉴别原则,并就历史洪水序列的检验、洪水发生频率的划分、洪水演变趋势的定量刻划等问题进行了讨论。     

艾比湖湿地生态效应能值评价

湿地是地球上具有多功能的独特生态系统,是自然界最富生物多样性的生态景观和人类最重要的生存环境之一。内陆干旱区的湿地则因其所处地理环境的特殊性更具有巨大保护价值。艾比湖湿地在我国内陆荒漠自然生态系统中具有一定典型性。其生态系统极不稳定,具有很强的敏感性和脆弱性。人类社会经济的迅猛发展,引起一系列以土地荒漠化为代表的生态逆向演替,严重的水土流失和锐减的生物多样性使其不可更新资源的能值投入远远超过其可更新资源,同时,肆虐的盐尘严重危害着天山北坡经济带甚至更远地区工、农、牧业生产和人们的生活环境。从能值角度评价环境的贡献,注重其生态效应,以期引起人们警醒,加强湿地资源的保护和管理,维护其可持续发展。     

Fe和Al对湖泊沉积物中磷赋存形态的影响

利用连续提取法研究了东部平原4个富营养化湖泊沉积物中磷的赋存特征,探讨了Fe、Al对沉积物中磷形态的影响.结果表明,富营养化程度越重的湖泊,其w(TP)(527.35～1 432.80 mg/kg)较高,w(TFe)和w(TAl)(分别为8 496.63～23 071.35和6 219.20～14 164.46 mg/kg)也较高.w(Fe)与w(Al)对各形态磷含量及分布的影响有所不同,其中对w(Fe-P)和w(Al-P)及其分布影响较大.w(Fe-P)、w(Al-P)和w(BD-Fe)之间存在相关关系,这主要与Fe、Al吸附部分沉积物释放的磷有关;w(Fe)与w(Al)对NH4Cl-P的含量及分布影响较小,而对NaOH85-P的含量及分布影响较大,w(NaOH85-P)与w(NaOH85-Fe)和w(NaOH85-Al)显著相关(P<0.01),这可能与NaOH85-P的形成机理有关.沉积物中w(TFe)/w(TP)、w(TAl)/w(TP)、Fe/P和Al/P等比值可能与湖泊富营养化程度有关,比值越小,湖泊富营养化程度越重.