Paleohydraulic reconstruction of a 40 ka‐old terrace sequence implies that water discharge was larger than today

The evolution of landscapes crucially depends on the climate history. This is particularly evident in South America where landscape responses to orbital climate shifts have been well documented. However, while most studies have focused on inferring temperature variations from paleoclimate proxy data, estimates of water budget changes have been complicated because of a lack of adequate physical information. Here, we present a methodology and related results, which allowed us to extract water discharge values from the sedimentary record of the 40 Ka‐old fluvial terrace deposits in the Pisco valley, western Peru. In particular, this valley hosts a Quaternary cut‐and‐fill succession that we used, in combination with beryllium‐10 (¹⁰Be)‐based sediment flux, gauging records, channel geometries and grain size measurements, to quantitatively assess sediment and water discharge values c. 40 Ka ago in relation to present‐day conditions. We compare these discharge estimates to the discharge regime of the modern Pisco River and find that the water discharge of the paleo‐Pisco River, during the Minchin pluvial period c. 40 Ka ago, was c. 7–8 times greater than the modern Pisco River if considering the mean and the maximum water discharge. In addition, the calculations show that inferred water discharge estimates are mainly dependent on channel gradients and grain size values, and to a lesser extent on channel width measures. Finally, we found that the c. 40 Ka‐old Minchin terrace material was poorer sorted than the modern deposits, which might reflect that sediment transport during the past period was characterized by a larger divergence from equal mobility compared to the modern situation. In summary, the differences in grain size distribution and inferred water discharge estimates between the modern and the paleo‐Pisco River suggests that the 40 Ka‐old Minchin period was characterized by a wetter climate and more powerful flood events. Copyright © 2015 John Wiley & Sons, Ltd.     

中国西部河谷型城市土地利用效益与城市化耦合协调发展研究

土地资源短缺是河谷型城市发展中极为突出的瓶颈问题,如何提高河谷城市土地利用效益以适应快速城市化过程是目前亟待解决的问题。本文以中国西部7个典型的河谷型城市为例,定量测度了其土地利用效益与城市化水平耦合协调关系,以期为城市土地利用效益与城市化协调发展提供参考。研究表明：截止到2012年,7个城市土地利用效益和城市化水平评价指数均有大幅上升,二者耦合协调等级均进入协调发展阶段。土地利用效益与城市化水平两个子系统之间相互关联,土地利用效益中经济效益和生态效益对城市化水平影响最为明显,人口城市化和社会城市化准则层各因子对土地利用效益影响较大。随着经济发展水平差距的缩小,各城市间协调性差距也逐渐缩小。区域发展的非均衡性导致西部河谷型城市与平原城市的土地利用效益、城市化水平以及二者的耦合协调关系的评价指数的增长速率并无明显差别。     

Free Amino Acids Content in Some Halophytes under Salinity Stress in Arid Environment,Jordan

The variation in free amino acids concentration was examined in halophytes under salt stress conditions during spring and autumn in an arid environment, Jordan. The experiment was conducted in the southern region of the Jordan valley, using four different halophytes namely: Atriplex halimus, Atriplex nummularia, Tamarix aphylla L., and Portulaca oleracea L. Free amino acid concentrations showed changeable patterns under salinity stress conditions compared to the non‐stress (control) with respect to plant species and seasonal variation. In general, the amino acid pool during the spring experienced increases in A. halimus with increasing salinity; and decreased in A. nummularia, P. oleracea L., and T. aphylla L., respectively. Whereas, during the autumn, the overall amino acids decreased in A. halimus and A. nummularia, and increased in T. aphylla L. and P. oleracea with increasing salinity. The amino acid pool concentrations of A. halimus L. during the autumn was similar to that in spring under stress condition. Similarly, T. aphylla L. and P. oleracea showed higher rates in the autumn. In contrast, A. nummularia L. exhibited a slight increase in amino acid composition in the autumn under stress conditions. The plantation of salt tolerant plants such as halophytes in saline sodic soils showed an effective decline in soil salinity and can be recommended to be used as a bioreclamation method instead of the traditional leaching method, which requires large amount of fresh water.     

平面SV波在饱和半空间中沉积谷地周围的散射

采用一种特殊的间接边界积分方程法,求解了平面SV波在饱和半空间中任意形状沉积谷地周围的二维散射问题。结合饱和半空间中膨胀波源和剪切波源格林函数,由分布在沉积和半空间交界面附近两虚拟波源面上的波源分别构造沉积内外的散射波场,由交界面连续条件建立方程并求解确定虚拟波源密度,总波场反应即可由自由波场和散射波场叠加而得。然后通过边界条件验算、退化解答与现有结果的比较以及稳定性检验,验证了方法的计算精度。通过一组典型算例,研究了平面SV波在饱和半空间中沉积谷地周围散射的基本规律,详细给出了不同参数情况沉积谷地附近地表位移幅值和孔隙水压,着重分析了入射SV波频率和角度、边界渗透条件、沉积孔隙率等因素对场地反应的影响,得出了一些有益的结论。     

含多个圆弧状沉积层河谷场地对平面SH波散射问题的解析解

利用波函数展开法给出了含多个圆弧状沉积层河谷(盆地)场地对平面SH波二维散射问题的一个解析解,并以具有三个沉积层的河谷为例,分析了河谷中沉积层层数与排列次序对SH波散射的影响。     

大型河谷场地地震动特性研究

采用有限差分方法,通过算例研究了大型河谷场地地震动特性分析中的人工边界的选取方法,对比分析了不同人工边界的选取对数值模拟结果的影响,确定了散射场地震反应分析输入边界的地震动输入方法,认为在进行有限差分动力计算时,模型两侧施加自由场边界的模拟效果要优于两侧施加粘性边界的模拟效果;同时,对FLAC计算软件进行二次开发,对2个地形差异较大的河谷场地,采用线性和非线性摩尔-库仑模型进行了地震反应对比分析,研究了河谷场地地震动幅值和频谱特性随地形变化的规律。模拟数据表明,河谷场地谷底处地震动基本无放大作用,地势凸起处放大作用则较为明显;当考虑土体非线性时,随着地震动强度的增加,放大作用逐渐减小;谱分析结果表明,地势凸起处受高频地震动的影响显著,而地势平坦的谷底则受低频地震动的影响显著。     

长江中游若干湖泊水生植物体内C、N、P及δ^13C分布

本文就长江中游9个湖泊10种水生植物的C、N、P和稳定C同位素进行了测定,水生植物C元素的平均含量为33.2±5.46%,N、P分别为1.58±0.90%和0.30±0.13%,δ13C组成变化在-27.91‰～-17.16‰之间.从水生植物的生长区域来看,叶子中的C、N和δ13C值与其所处的水环境有密切的关系.对于沉水植物,由于受到无机碳的限制,其叶子中C和N含量显著低于挺水植物及浮水植物;而同时由于水体中无机碳δ13C组成较高,使得沉水植物叶子的δ13C大于挺水植物和浮水植物.     

Response to Morgan's comment

We respond to Morgan's comment on our model for cross‐profile morphology for glacial valleys. Copyright © 2005 John Wiley & Sons, Ltd.     

新疆罗布泊东延地区--阿其克谷地生态地质环境现状及保护措施初探

阿其克谷地是罗布泊洼地的东延部分.对谷地内生态地质环境的气候环境、水环境、土壤环境和生物环境4个主要因子的调查表明：谷地内气候极端恶劣，属于极端干旱的温带和暖温带大陆性气候;水资源极度匮乏，以地下水为主;土壤类型有石膏棕漠土、盐土和流动风沙土3类，一般没有什么肥力潜力;生物物种贫乏，以超旱生和耐盐生的荒漠群落为主.当前，人类活动对谷内生态环境的影响主要为采矿、旅游、盗猎、放牧等活动.最后提出了树立全局观念，限制人类活动，建立生态环境保护区和水资源开发与涵养并举等生态环境保护建议。     

鲁北小清河流域土壤中元素分布特征及环境质量评价

对鲁北小清河流域表层和深层土壤样品进行系统采集，分析土壤中元素全量和有效态含量，利用地球化学方法研究元素在土壤中的丰缺和分布规律，认为Se、Pb、Hg在表层土壤中明显富集，与地表污染有关。通过对表层土壤中元素有效态含量和重金属全量的研究，对区内土壤质量和土壤环境质量进行评价，结果表明区内土壤中除Mo、B、Mn出现大面积缺量区外，其他元素均在适量区以上，土壤质量良好，营养水平较高；单元素土壤环境质量除Cr、Hg、cd出现小范围的严重污染区外，其他元素未出现严重污染区，土壤环境质量较好，但多因子综合环境质量评价起始污染以上的面积已接近70％，应予以重视。