汇流阈值对提取叶尔羌河上游流域面积高程积分的影响

不同地貌单元,其汇流阈值的界定差异较大,而不同的汇流阈值直接影响河流长度、河网密度以及集水区面积的提取结果,因此,汇流阈值的界定是提取流域面积高程积分的关键.以叶尔羌河上游流域为研究对象,基于不同分辨率数字高程模型数据对叶尔羌河上游流域面积高程积分的提取结果,确定适宜分辨率的数字高程模型数据,探讨不同汇流阈值对叶尔羌河...     

Multi-group approximation, scattering and calibration coefficients, uncertainty estimates and detection limits of a NaI(Tl)-based gamma spectrometry set-up for low-level activity analysis

This paper describes a quantitative radioactivity analysis method especially suitable for environmental samples with low-level activity. The method, consisting of a multi-group approximation based on total absorption and Compton spectra of gamma rays, is coherently formalized and a computer algorithm thereof designed to analyze low-level activity NaI(Tl) gamma ray spectra of environmental samples. Milk powder from 1988 was used as the example case. Included is a special analysis on the uncertainty estimation. Gamma sensitiveness is defined and numerically evaluated. The results reproduced the calibration data well, attesting to the reliability of the method. The special analysis shows that the uncertainty of the assessed activity is tied to that of the calibration activity data. More than 77% of measured 1461-keV photons of ⁴⁰K were counted in the range of clearly lower energies. Pile-up of single line photons (¹³⁷Cs) looks negligible compared to that of a two-line cascade (¹³⁴Cs). The detection limit varies with radionuclide and spectrum region and is related to the gamma sensitiveness of the detection system. The best detection limit always lies in a spectrum region holding a line of the radionuclide and the highest sensitiveness. The most radioactive milk powder sample showed a activity concentration of 21 ± 1 Bq g⁻¹for ¹³⁷Cs, 323 ± 13 Bq g⁻¹ for ⁴⁰K and no ¹³⁴Cs.     

Conceptual Framework of Tourism Carrying Capacity for a Tourism City： Experiences from National Parks in the United States

There is no universally-accepted definition of tourism carrying capacity(TCC).Numerical TCC focuses on use level and is considered as"a magic number"of the saturation point for tourism.There are several reasons why numerical tourism capacity is inadequate.Alternatively,tourism capacity can be defined in terms of limits of acceptable change,which shifts the focus from"how much use is too much"to"how much change is acceptable".This article proposes an improved conceptual framework for evaluating carrying capacity for the tourism city based on approaches used in US national parks,which consider the impact of human use on a city's economic,environmental/resource,and socio-cultural conditions.Based on the basic data of indicator values and relevant standards,the framework monitors the current indicators and predicts future indicator values; it can also be used to assess and predict TCC.     

Evaluation of the Temporal Transferability of a Model Describing Dissolved Solids in Streams of the Upper Colorado River Basin1

Kenney, Terry A. and Susan G. Buto, 2012. Evaluation of the Temporal Transferability of a Model Describing Dissolved Solids in Streams of the Upper Colorado River Basin. Journal of the American Water Resources Association (JAWRA) 48(5): 1041‐1053. DOI: 10.1111/j.1752‐1688.2012.00667.x Abstract: The application of a nonlinear least‐squares regression model describing the sources and transport of dissolved solids in streams of the Upper Colorado River Basin, and that was calibrated using data from water year 1991, was evaluated for use in predicting annual dissolved‐solids loads for the years 1974 through 1998. Simulations for each water year were run using annual climate data. To evaluate how well the model captures the observed annual variability across the basin, differences in predicted annual dissolved‐solids loads for each simulated year and 1991 were compared with differences in monitored annual loads. The temporal trend of the differences between predicted annual loads for the simulated years and the load for 1991 generally followed the trend of the monitored loads. The model appears to underpredict the largest annual loads and overpredict some of the smaller annual loads. An underprediction bias for wetter years was evident in the residuals as was an overprediction bias, to a lesser degree, for drier years. A regression analysis on the residuals suggests that the underprediction bias is associated with precipitation differences from 1991 and with previously defined downward trends in dissolved‐solids concentrations in the basin. In general, given the representative climatic conditions, the model adequately performs throughout the period examined. However, the model is most transferable to years with climatic conditions similar to 1991.     

安宁河上游冷渍沟泥石流特征及其发展趋势

冷渍沟是安宁河上游左岸的一级支沟,沟内发育了一大型滑坡 碎屑流,为后续泥石流活动提供充足的松散物质来源。为了研究冷渍沟泥石流的危害特征,在野外调查和实地勘测的基础上,分析了泥石流的形成背景条件及其特征,探讨了泥石流的发展趋势,提出了相应的泥石流防治对策。研究表明,冷渍沟泥石流属于过渡性（亚粘性）高频大规模泥石流,泥石流成灾速度快,危害严重;百年一遇的泥石流容重为21 t/m3,五十年一遇的泥石流容重为20 t/m3,二十年一遇害泥石流容重为19 t/m3,相应的峰值流量分别为12768、8171和3818 m3/s。在常态下,冷渍沟泥石流的发生频率和规模会逐渐减小;但如果近期遭遇强震或者暴雨,一旦滑坡失稳堵塞沟道,将会暴发大规模泥石流,很容易堵断安宁河,对上下游造成严重危害。因此,建议在该流域布设必要的泥石流防治工程;同时加强对沟道两岸和滑坡稳定性监测,做好泥石流发生的监测预警工作     

Investigation of the Curve Number Method For Surface Runoff Estimation In Tropical Regions

This study tests the applicability of the curve number (CN) method within the Soil and Water Assessment Tool (SWAT) to estimate surface runoff at the watershed scale in tropical regions. To do this, surface runoff simulated using the CN method was compared with observed runoff in numerous rainfall‐runoff events in three small tropical watersheds located in the Upper Blue Nile basin, Ethiopia. The CN method generally performed well in simulating surface runoff in the studied watersheds (Nash‐Sutcliff efficiency [NSE] > 0.7; percent bias [PBIAS] < 32%). Moreover, there was no difference in the performance of the CN method in simulating surface runoff under low and high antecedent rainfall (PBIAS for both antecedent conditions: ~30%; modified NSE: ~0.4). It was also found that the method accurately estimated surface runoff at high rainfall intensity (e.g., PBIAS < 15%); however, at low rainfall intensity, the CN method repeatedly underestimated surface runoff (e.g., PBIAS > 60%). This was possibly due to low infiltrability and valley bottom saturated areas typical of many tropical soils, indicating that there is scope for further improvements in the parameterization/representation of tropical soils in the CN method for runoff estimation, to capture low rainfall‐intensity events. In this study the retention parameter was linked to the soil moisture content, which seems to be an appropriate approach to account for antecedent wetness conditions in the tropics.     

集中式污水厂重金属排放限值及其控制进展研究

介绍了中国集中式污水厂污水处理现状,主要包括污水厂进出水监测指标和进出水水质指标设计不足,重金属处理效果不明显;同时对国外污水处理现状以及重金属排放限值进行比较,探讨了中国污水处理厂污水中重金属排放限值及控制的问题,污水中重金属处理工艺未设计,进出水水质指标未将重金属指标纳入设计中,重金属排放限值远高于发达国家限值.结合现状分析,提出加强污水处理厂重金属源头控制与排放限值监管的相关建议,以确保排放水体的环境安全.     

地质构造单元交接带表土中重金属污染特征对比及源解析:以重庆城口地区为例

中国地质构造复杂,不同地质构造区地质演化史差异显著,对其上发育的土壤重金属含量分布、污染特征及来源亦具有影响.以秦岭地槽和上扬子地台交界区重庆市城口县为研究区,采集表层土壤样品115件,综合运用地累积指数、污染指数和正定矩阵因子分解模型（PMF）分析不同地质构造单元区表土重金属含量分布、污染特征和来源.结果表明：①整体上,该区表土重金属处于中度污染水平,其中Cd为主要污染元素;②表土中Cd超标点位主要分布在乌坪断裂以北地区;③发育于秦岭地槽区埃迪卡拉纪-早寒武世地层之上的土壤中重金属含量显著高于上扬子地台区相同时代地层之上的土壤;④研究区表土重金属来源主要为成土母岩风化及交通和燃煤活动,其中成土母岩风化的贡献率为75%,是控制研究区表土重金属含量分布和污染的主要因素.这为研究不同地质构造区土壤重金属含量分布、富集和来源提供了范例和科学依据.     

长江中下游、浙西地区的上石炭统

本文系统阐述了区内上石炭统地层的分布范围、岩性特征、厚度变化及所含生物群面貌。     

The Environmental Limits to Globalization

Abstract:  Criticisms of globalization have been largely based on its socioeconomic effects, but the environmental impacts of globalization are equally important. These include acceleration of climate change; drawdown of global stocks of cheap energy; substantial increases in air, water, and soil pollution; decreases in biodiversity, including a massive loss of crop and livestock varieties; depletion of ocean fisheries; and a significant increase in invasions of exotic species, including plant, animal, and human pathogens. Because of negative feedback from these changes, the future of globalization itself is bleak. The environmental and social problems inherent in globalization are completely interrelated—any attempt to treat them as separate entities is unlikely to succeed in easing the transition to a postglobalized world.