210Pb-dating of a lake sediment core from Lough Carra (Co. Mayo, western Ireland): use of paleolimnological data for chronology validation below the 210Pb dating horizon

The chronologies and sediment accumulation rates for a lake sediment sequence from Lough Carra (Co. Mayo, western Ireland) were established by applying the constant initial concentration (CIC) and constant rate of supply (CRS) hypotheses to the measured ²¹⁰Pb_excess profile. The resulting chronologies were validated using the artificial fallout radionuclides ¹³⁷Cs and ²⁴¹Am, which provide independent chronostratigraphic markers for the second half of the 20th century. The validity of extrapolating the derived CIC and CRS dates below the ²¹⁰Pb dating horizon using average sedimentation rates was investigated using supplementary paleolimnological information and historical data. Our data confirm that such an extrapolation is well justified at sites characterised by relatively stable sedimentation conditions.     

太湖蓝藻水华分级及其时空变化

根据MODIS影像和实地监测叶绿素a浓度数据,采用太湖蓝藻水华分级评估方法,对2004~2008年太湖不同类型蓝藻水华类型进行评估并统计分析,探求太湖蓝藻水华特征及其时空变化规律,以期为太湖蓝藻水华预防和预警提供支持。结果表明：（1）2004~2008年,全湖共发生蓝藻水华414次,以小型蓝藻水华为主,发生333次,占总次数的80.43%;随着蓝藻水华级别的增加,发生次数逐渐减少;（2）空间上,蓝藻水华主要发生在太湖的北部和西部区域,并且蓝藻水华发生级别由高到低基本上沿西北-东南方向分布;（3）年际变化上,蓝藻水华发生次数呈逐渐增加趋势,蓝藻水华级别较高、次数较多的年份主要集中于2006年和2007年;（4）年内变化上,4~8月份,蓝藻水华发生次数呈增加趋势,8~11月,蓝藻水华发生次数逐渐减少。并且,蓝藻水华主要集中于5月和7~10月份,尤其是8~10月。     

三峡水库调节典型时段对洞庭湖湿地水情特征的影响

洞庭湖与长江联系紧密,三峡工程运行将改变洞庭湖的水文过程,影响湖泊湿地生态系统。为了评估三峡工程运行对洞庭湖湿地的水文影响,选取水文情势变化大且可能对植被生长产生重大影响的汛末蓄水和汛前腾空两个时段,运用反映江湖水动力交互的水动力学方法计算了三峡水库不同调节流量下湖泊水位与流量的变化特征,并结合湖泊高程和面积关系曲线,分析了不同增减下泄流量对洲滩湿地淹没出露的影响。结果表明,洞庭湖吞吐长江,复杂的江湖水动力交互作用使得湿地水文过程变化有明显的非线性。在恒定流条件下,汛末蓄水减泄4 000 m3/s流量可使城陵矶水位降低1 m。同样抬高1 m水位,汛前腾空约需增泄3 500 m3/s。在空间分布上,三峡水库调节对洞庭湖水情影响具有明显的异质性,受江湖关系和湖盆地形的影响,与长江水力联系紧密的东洞庭湖、南洞庭湖东部和西洞庭湖北部受三峡水库调节影响大,而西洞庭湖南部影响较小     

洞庭湖湿地生态系统管理面临的威胁及应对策略初探

生态系统管理可以实现自然资源的多目标管理。洞庭湖湿地生态系统优越,区域内社会经济发达,但面临保护与发展的双重压力。其中,开展洞庭湖区湿地生态系统管理面临众多威胁,包括自然灾害频发、资源利用不当、工农业污染突出、自然保护能力不足以及季节性缺水等新老问题交织在一起,共同导致了洞庭湖湿地生态系统功能降低,包括生物多样性降低、调蓄能力减弱、洪渍涝灾害加剧、地下水位升高、垸老田低等现象日益突出,而且这种人类不合理活动的后效放大驱动将长期存在,危及到了湖区水产养殖的自然增殖以及自然资源基础的安全性,成为湖区社会经济发展的严重制约因素。为此,建议在遵循生态系统方法的前提下,洞庭湖地区应该加强管理体制机制创新实践,加快湿地保护的立法与执法进程,通过编制洞庭湖区中长期发展总体规划,促进各种利益相关方参与和共管洞庭湖湿地退田还湖等生态恢复工程的巩固、湿地资源合理利用、湿地产业的开发以及湖区湿地生态与环境建设,最终实现湖区生态美好、民生改善的“人地和谐     

洞庭湖区畜禽排泄物的环境效应

洞庭湖湿地是长江中游重要的生态功能区,其生态功能的退化制约了湖区经济的可持续发展。近些年来,随着湖区集约化畜牧业的迅速发展,畜禽粪尿等排泄物对湖区生态环境构成了严重威胁。从畜禽养殖量、粪尿等污染物的年排泄量、粪便猪粪当量及负荷量、土地畜禽粪便负荷承受程度4个方面估算并分析了洞庭湖各县（市区）畜禽养殖业的环境威胁性。结果表明:2007年洞庭湖区各类畜禽粪尿排泄总量为3 17279万t,相当于猪粪当量2 92113万t。全年畜禽粪尿流失总量达1 11048万t。畜禽排泄物中年流失化学需氧量50.80万t,氨氮7. 81万t。从畜禽粪便负荷量警报值及分级结果看,畜禽排泄物对岳阳楼区、汩罗市的环境威胁比较严重,对云溪区、临澧县、武陵区、岳阳县、津市市和湘阴县生态环境亦有一定的影响。〖     

太湖流域土地利用变化特征与机制分析

太湖流域土地总面积36 895 km²,包括了上海、江苏、浙江两省一市的部分区域,其中,江苏占53%,浙江占33%,上海占14%。太湖流域土地利用按下垫面可以分为耕地、建设用地、水域和其他用地4种类型。采用2005年土地详查数据与上次防洪规划数据进行比较。研究发现：耕地是太湖流域最重要的下垫面,占土地总面积的36.6%,建设用地占土地占面积的23%,与耕地的矛盾十分尖锐,水域面积较大,占土地总面积的14.5%。1996~2005年,土地利用变化的总体趋势是,耕地面积减少,减少幅度最大的地区在太湖流域江苏部分,两省一市建设用地均有30%左右的增长幅度,土地围垦得到有效控制,水域面积略有下降。人口增长和城市化快速发展、经济发展、效益驱动与土地管制差异是造成土地利用变化的主要原因     

大型水生植物对骆马湖氮磷元素及磷酸酶活性的影响

在骆马湖中选择有大型水生植物生长区域及无草对照区,测定主要水质指标,采集沉积物柱状样,分层测定沉积物氮磷元素含量及磷酸酶活性,探讨大型水生植物对骆马湖生态系统中氮磷元素及磷酸酶活性影响特征,结果表明：（1）大型水生植物生长区上覆水透明度明显高于对照(CK),是对照(CK)19倍;但有草区凯氏氮(KN)、可溶性氮(DN)含量低于对照(CK),方差分析表明二者差异极显著(〖WTBX〗p〖WTBZ〗≤001);（2）大型水生植物生长能降低磷酸酶的活性,有草区不同深度沉积物酸（碱）磷酸酶活性总体小于对照(CK),但沉积物表层磷酸酶活性最强;（3）有草区不同深度沉积物TP含量低于对照(CK),但有草区表层沉积物凯氏氮(KN)含量高于对照(CK ).     

Assessment of Biological and Environmental Phenology at a Landscape Level from 30 Years of Fixed-Date Repeat Photography in Northern Sweden

A 30-year series (1978–2007) of photographic records were analysed to determine changes in lake ice cover, local (low elevation) and montane (high elevation) snow cover and phenological stages of mountain birch (Betula pubescens ssp. czerepanovii) at the Abisko Scientific Research Station, Sweden. In most cases, the photographic-derived data showed no significant difference in phenophase score from manually observed field records from the same period, demonstrating the accuracy and potential of using weekly repeat photography as a quicker, cheaper and more adaptable tool to remotely study phenology in both biological and physical systems. Overall, increases in ambient temperatures coupled with decreases in winter ice and snow cover, and earlier occurrence of birch foliage, signal a reduction in the length of winter, a shift towards earlier springs and an increase in the length of available growing season in the Swedish sub-arctic.     

Sexual difference in mercury concentrations of lake trout (Salvelinus namaycush) from Lake Ontario

We determined total mercury (Hg) concentrations in 50 female lake trout (Salvelinus namaycush) and 69 male lake trout from Lake Ontario (Ontario, Canada and New York, United States). Results showed that, on average, males were 8% higher in Hg concentration than females in Lake Ontario. We also used bioenergetics modeling to determine whether a sexual difference in gross growth efficiency (GGE) could explain the observed sexual difference in Hg concentrations. According to the bioenergetics modeling results, male GGE was about 3% higher than female GGE, on average. Although the bioenergetics modeling could not explain the higher Hg concentrations exhibited by the males, a sexual difference in GGE remained a plausible explanation for the sexual difference in Hg concentrations of the lake trout. In an earlier study, male lake trout from Lake Ontario were found to be 22% higher in polychlorinated biphenyl (PCB) concentration than females from Lake Ontario. Thus, although males were higher in both Hg and PCB concentrations, the degree of the sexual difference in concentration varied between the two contaminants. Further research on sexual differences in Hg excretion rates and Hg direct uptake rates may be needed to resolve the disparity in results between the two contaminants.     

Historical mercury contamination in sediments and catchment soils of Diss Mere, UK

A 5.3 m sediment core and soil samples were taken from Diss Mere and its catchment. The sediment core was dated and Hg analysed on the sediment and soil samples. The Hg record of the sediment core shows that Diss Mere has been contaminated for the past thousand years and the historical trends in sediment contamination are in good agreement with the development of the weaving industry in Diss and hemp cultivation in the region. Mercury contamination in Diss Mere has been significant and reached a peak in the mid-19th century with sediment Hg concentrations over 50 μg g⁻¹. Elevated Hg concentrations were also found in contemporary soils in residential areas with former industrial land use. Although local hemp cultivation and the traditional weaving industry were abandoned a hundred years ago, Hg contamination caused by these activities still exists in the catchment, and affects the lake.