基于时序InSAR的覆砂石尾矿坝形变演化研究

为解决目前采用在尾矿坝坝体及滩面覆盖砂石进行防尘治理与闭库，但传统监测手段难以实现坝体整体监测的问题，采用时序InSAR技术对2014年10月至2018年7月的Sentinel-1A影像进行处理，提取了对应时间段内卡房尾矿坝的形变信息，并结合实地调查及尾矿坝建设资料，研究了卡房尾矿坝的时序形变演化规律。结果表明:SBAS InSAR监测到坝体出现第1次异常形变加速运动时间与坝体开始铺设砂石工程的施工时间节点完全吻合，体现SBAS InSAR技术在受人为工程影响的坝体形变监测方面具有极高的敏感性。坝体在施工结束后，坝体形变加剧趋势并未缓解，并且出现2次加速现象，分析认为是由于在坝体铺设约2 m厚的碎砂石极大地增加了坝体荷载，打破了坝体原有的应力平衡状态，且识别出雨季对坝体形变影响显著，表明铺设砂石会使得降雨在坝体中的停滞时间加长，进一步引发非雨季期间坝体形变加剧。研究结果不仅能还原坝体出现异常形变的时间与演化过程，而且还可以对引起异常形变的内在影响因素进行分析与论证，对指导尾矿坝灾害识别、分析与治理具有重要的指导意义。     

重庆城口地区下寒武统黑色岩系重金属富集特征及其生态环境效应

重庆城口地区广泛发育有下寒武统黑色岩系。测定了城口地区下寒武统黑色岩系中多金属富集层、黑色岩系岩石及其风化土壤、硅质岩样品中Cr、Co、Ni、Cu、Zn、As、Cd、Sb、Pb含量。结果表明多金属富集层中重金属相对比较富集,其中Cd、Zn、As的富集程度较高,富集系数平均分别为119.67,10.73,7.30。运用地质累积指数法和生态危害指数法评价了重金属的潜在生态环境效应,其中Cd、As的生态危害较大,黑色岩系尤其以多金属富集最为明显,在未来的研究中关注多金属富集层中Cd、As的生态环境效应。     

双壳类壳体时间序列的建立方法及存在的问题

利用双壳类壳体提取古气候古环境信息是生物碳酸盐研究的热点,而壳体定年一直是研究中的难点。相关研究主要观点是先找到一些时间控制点,再按照线性内插法来确定壳体的时间序列。本文综述了国内外目前双壳类壳体定年的常用方法,根据时间控制点的获得将这些方法归为以下几类:壳体日生长层法、壳体氧同位素法、数字图像技术法和微量元素法,介绍并讨论了每种方法的应用和存在的不足。研究者应该根据具体研究的生物和环境选择适合的方法。     

PM_(10)浓度时间序列多时间尺度分析的小波方法

文章利用Morlet小波函数进行小波变换,以乌鲁木齐市的大气污染物时间序列为例,分析了当地PM10的多时间尺度的演变特性。研究结果显示,其年际变化和季节性变化的时间尺度在尺度空间中分布不均匀,受气象和污染源因素影响,具有较明显的局部化特征。     

华北地区1951-2009年气温、降水变化特征

基于华北五省(市)64个基本气象站的1961-2009年逐年逐月气温、降水资料, 利用泰森权重计算了华北地区面平均降水及面平均气温,并建立了7个长序列气象站的气温、降水与面平均值的回归方程,展延了研究区1951-1960年面平均降水和气温资料。对展延后的1951-2009年序列数据,应用Mann-Kendall检验、Mann-Whitney检验、9 a滑动平均等方法进行趋势分析,分析结果显示: 该区59 a间年气温上升了1.5 ℃,年气温序列存在显著上升趋势,年气温序列在1993年前后有一个突变点,年气温距平以1989年为低温期与高温期的分界线,年气温平均每10 a增长2.2%;年降水序列无显著趋势,亦无显著跳跃趋势,年降水距平大致以1976年为多雨期与少雨期的分界线,年降水平均每10 a增长-1.3%。研究成果为深入分析华北地区气候变化规律、未来气候变化影响,以及水资源对气候变化的响应提供了基础。     

苯系化合物在硝酸盐还原条件下的生物降解性能

运用驯化的反硝化混合菌群进行了苯系化合物(BTEX)的厌氧降解试验.结果表明,混合菌群能够在反硝化条件下有效降解苯、甲苯、乙苯、邻二甲苯、间二甲苯和对二甲苯.BTEX的降解规律符合底物抑制的Monod模型,当初始浓度小于50mg·L^-1时,6种受试基质的厌氧降解速率顺序为:甲苯>乙苯>间二甲苯>邻二甲苯>对二甲苯>苯.整个试验过程中NO₃^-的消耗与苯、甲苯、乙苯、邻二甲苯、间二甲苯及对二甲苯生物降解之间的摩尔比分别为:9.47,9.26,1     

Robustness of Meteorological Droughts in Dynamically Downscaled Climate Simulations

We examine the robustness of a suite of regional climate models (RCMs) in simulating meteorological droughts and associated metrics in present‐day climate (1971‐2003) over the conterminous United States (U.S.). The RCMs that are part of North American Regional Climate Change Assessment Program (NARCCAP) simulations are compared with multiple observations over the climatologically homogeneous regions of the U.S. The seasonal precipitation, climatology, drought attributes, and trends have been assessed. The reanalysis‐based multi‐model median RCM reasonably simulates observed statistical attributes of drought and the regional detail due to topographic forcing. However, models fail to simulate significant drying trend over the Southwest and West. Further, reanalysis‐based NARCCAP runs underestimate the observed drought frequency overall, with the exception of the Southwest; whereas they underestimate persistence in the drought‐affected areas over the Southwest and West‐North Central regions. However, global climate model‐driven NARCCAP ensembles tend to overestimate regional drought frequencies. Models exhibit considerable uncertainties while reproducing meteorological drought statistics, as evidenced by a general lack of agreement in the Hurst exponent, which in turn controls drought persistence. Water resources managers need to be aware of the limitations of current climate models, while regional climate modelers may want to fine‐tune their parameters to address impact‐relevant metrics.     

Optimal Reorganization of NASA Earth Science Data for Enhanced Accessibility and Usability for the Hydrology Community

A long‐standing “Digital Divide” in data representation exists between the preferred way of data access by the hydrology community and the common way of data archival by earth science data centers. Typically, in hydrology, earth surface features are expressed as discrete spatial objects (e.g., watersheds), and time‐varying data are contained in associated time series. Data in earth science archives, although stored as discrete values (of satellite swath pixels or geographical grids), represent continuous spatial fields, one file per time step. This Divide has been an obstacle, specifically, between the Consortium of Universities for the Advancement of Hydrologic Science, Inc. and NASA earth science data systems. In essence, the way data are archived is conceptually orthogonal to the desired method of access. Our recent work has shown an optimal method of bridging the Divide, by enabling operational access to long‐time series (e.g., 36 years of hourly data) of selected NASA datasets. These time series, which we have termed “data rods,” are pre‐generated or generated on‐the‐fly. This optimal solution was arrived at after extensive investigations of various approaches, including one based on “data curtains.” The on‐the‐fly generation of data rods uses “data cubes,” NASA Giovanni, and parallel processing. The optimal reorganization of NASA earth science data has significantly enhanced the access to and use of the data for the hydrology user community.     

Tracking a half century of media reporting on gray wolves

Natural resource and wildlife managers must balance the disparate priorities of a diversity of stakeholders. To manage these priorities, a firm understanding of topics salient to the public is needed. The media often report on issues of importance to the public; therefore, these reports may be a useful measure of public interest. However, efficient methods for distinguishing diverse topics related to a wildlife management issue reported in the media and changes in the salience of those topics have been lacking. We used latent Dirichlet allocation, a Bayesian mixture model, to quantitatively assess the salience of topics surrounding the gray wolf (Canis lupus), which was reintroduced to Idaho (U.S.A.) in 1995. We analyzed articles published from 1960 to 2015 in an Idaho newspaper. We identified 6 distinct topics associated with gray wolves: policy, hunting, biological status, implementation of management, recovery, and human-wolf conflict. The salience of topics pre- and postreintroduction of wolves (1995) and pre- and postdelisting of wolves from the U.S. Endangered Species Act (2009) differed significantly, underscoring that these events were turning points in how issues were being publicly discussed and framed. Articles written by the local reporters were more likely to report on topics regarding conflict between humans and wolves, whereas articles sourced from a national outlet reported more on topics pertaining to wolf policy and biological status. In the context of managing a contentious, far-ranging, and long-lived wildlife species, our methods can help guide the location and timing of a suite of management strategies (e.g., media relation plans and stakeholder engagement) that promote human-wildlife coexistence across different landscapes.     

Recent Changes in Stream Flashiness and Flooding,and Effects of Flood Management in North Carolina and Virginia

The southeastern United States has undergone anthropogenic changes in landscape structure, with the potential to increase (e.g., urbanization) and decrease (e.g., reservoir construction) stream flashiness and flooding. Assessment of the outcome of such change can provide insight into the efficacy of current strategies and policies to manage water resources. We (1) examined trends in precipitation, floods, and stream flashiness and (2) assessed the relative influence of land cover and flow‐regulating features (e.g., best management practices and artificial water bodies) on stream flashiness from 1991 to 2013. We found mean annual precipitation decreased, which coincided with decreasing trends in floods. In contrast, stream flashiness, overall, showed an increasing trend during the period of study. However, upon closer examination, 20 watersheds showed stable stream flashiness, whereas 5 increased and 6 decreased in flashiness. Urban watersheds were among those that increased or decreased in flashiness. Watersheds that increased in stream flashiness gained more urban cover, lost more forested cover and had fewer best management practices installed than urban watersheds that decreased in stream flashiness. We found best management practices are more effective than artificial water bodies in regulating flashy floods. Flashiness index is a valuable and straightforward metric to characterize changes in streamflow and help to assess the efficacy of management interventions.