Examining the fate of WWTP effluent nitrogen using δ 15N–NH4 +, δ 15N–NO 3 − and δ 15N of submersed macrophytes     

Jennifer L. A. Hood  William D. Taylor  Sherry L. Schiff 《Aquatic Sciences - Research Across Boundaries》2014,76(2):243-258

The use of submersed macrophyte tissue δ ¹⁵N to quantify the level of WWTP effluent use in a highly urbanized and agricultural river was evaluated using several methods. Macrophytes, NH₄ ⁺ and NO₃ ^? were collected by canoe along two 10 km reaches of river, upstream and downstream of two major municipal WWTPs over 3 years. NH₄ ⁺ decreased in concentration while δ ¹⁵N–NH₄ ⁺ increased as a function of distance downstream of both WWTPs, changing in one survey from 13 to 31 ‰ over 1 km. This increase is attributed to the combined effects of volatilization, nitrification and uptake. While NO ₃ ^? concentrations increased downstream of the WWTP over one of the survey reaches, δ ¹⁵N–NO ₃ ^? showed no prominent trend with distance at either. Macrophyte tissue δ ¹⁵N increased with distance downstream of both WWTPs, with a slope not significantly different from that of δ ¹⁵N–NH₄ ⁺ suggesting that macrophytes incorporate effluent NH₄ ⁺ as their main N source in those areas. However, mixing models suggest that towards the end of the reach, where source separation is distinct, macrophytes may utilize background NO ₃ ^? . Our study indicates the difficulty of deriving precise estimates of effluent use by macrophytes in a system where the δ ¹⁵N of the effluent changes rapidly. It also illustrates the utility of macrophytes in describing those changes where the effluent is too attenuated to allow for direct isotopic analysis.  相似文献   

苏州城市游憩场点系统空间结构分形   总被引：7，自引：2，他引：5  

黄泰  保继刚  戴学军 《地理科学进展》2009,28(5)

城市游憩场点系统是和谐城市规划建设的核心对象,也是一种结构复杂的自然-人文复合系统.本文选取随机聚集维数、空间关联维数、网格维数三项指标.以苏州市区为例,对新时期我国城市游憩场点系统的空间结构分形及优化进行了系统论证与解析.研究发现:①城市游憩场点系统的空间结构是具有分形特性的;②各分维指标能够准确地刻画城市游憩场点系统的空间结构及其分异,也为环城游憩带理论及城乡二元游憩结构分异现象等提供了分形解释依据;③苏州游憩场点系统的空间结构呈现出一种核心松散-外围紧致、白组织能力离心化现象比较严重的结构递变趋势,这种结构模式与游憩需求的空间分布结构基本吻合,它准确反映了成熟型游憩场点系统的空间发展态势,也说明加强对游憩场点系统的自组织能力的引导和提升,是和谐城市规划建设中的一项不可或缺的重要工作;④与以往研究结论相对比,发现游憩场点系统与旅游景区(点)系统在空间结构上存在合理的分形差异.  相似文献   

Analysis of water consumption using a regional input–output model: Model development and application to Zhangye City,Northwestern China     

Y. Wang  H.L. Xiao  M.F. Lu 《Journal of Arid Environments》2009,73(10):894-900

Based on a regional input–output model, we developed a method to identify the relationships between production activities and the related water consumption, as well as the relationships established between different sectors concerning water resources (i.e. indirect consumption). This method is applied to Zhangye City, an arid area of northwestern China that is characterized by water shortages. Our results confirm that although Zhangye suffers from a serious water shortage, the city's economic structure is based on sectors that consume large quantities of water. On the one hand, food production and forestry consume large quantities of water, reflecting the large scale of these water-intensive forms of land use. On the other hand, the industrial and service sectors use a smaller amount of water directly in production, but to produce the intermediate inputs that they incorporate into their production processes, a high consumption of water is often necessary. At present, there is no evidence that the city alleviates its water scarcity by importing virtual water in the form of economic inputs produced in other regions, suggesting that planners should include both direct and indirect water consumption in their resource allocation planning.  相似文献   

Quantifying the temporal dynamics of wood in large rivers: field trials of wood surveying,dating, tracking,and monitoring techniques     

B.J. MacVicar  H. Piégay  A. Henderson  F. Comiti  C. Oberlin  E. Pecorari 《地球表面变化过程与地形》2009,34(15):2031-2046

Wood plays an important role in stream ecology and geomorphology. Previous studies of wood in rivers have quantified spatial distributions but temporal dynamics remain poorly documented. The lack of such data is related to limitations of existing methods, especially when applied to large rivers. Five techniques are field‐tested to assess their utility for quantifying the temporal dynamics in rivers: repeated high‐resolution aerial surveys, the measurement of wood physical characteristics as proxies for ¹⁴C dating, passive and active radio frequency identification (RFID) tags, radio transmitters, and video. The spatial distribution of wood is surveyed using aerial imagery with a resolution finer than 0·10 m. The estimation of temporal trends by repeated aerial‐based surveys needs to consider vegetation growth and hiding. Wood residence times can be calculated using ¹⁴C analysis, but the assessment of wood physical characteristics including decay status and wood density offers a cheaper, if less accurate, alternative. Wood resistance to penetration is tested but results are not significant. Radio transmitters are reliable for multi‐year (～5 year) surveys and can be detected at 800 m. Passive RFID tags are limited by a read range of 0·30 m but are reliable for longer term (>5 year) studies. Active RFID tags combine a moderate read range (10–300 m) and low cost with in‐flood detection but require more testing. Video monitoring of wood passing on the surface of a river is successfully implemented. For a single flood on the Ain River (France), wood transport rates are an order of magnitude higher on the rising limb of the hydrograph than on the falling limb. Overall, the techniques improve the ability to gather the data needed to understand wood transfer processes and calibrate budgets of wood in rivers. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Quasi-periodic patterns coupling the Sun,solar wind and the Earth     

《Journal of Atmospheric and Solar》2008,70(17):2112-2117

The spectrum of velocity and magnetic fields in the solar wind is self-similar (power-law type) in the frequency range greater than >1/day indicating well-mixed turbulence. But it loses self-similarity for lower frequencies indicating the presence of large-scale patterns, which are intermittently generated inside the Sun and propagate from the Sun to the Earth.Here we discuss the spatia–temporal characteristics and origin of the 1.3-year quasi-periodic pattern found inside the Sun by helioseismic methods and detected in the solar wind. To identify and characterize this pattern on the Sun we use time series of solar magnetic Carrington maps generated at the Wilcox Solar Observatory and independent component data analysis. This analysis shows the latitudinal distribution of the pattern, its variable frequency and intermittent appearance.  相似文献   

西加拿大波利尔平原地表水富营养化管理技术     

E. E. Prepas  T. P. Murphy  G. Lawrence  P. A. Chambers  R. D. Robarts  W. M. Tonn  J. M. Burke  S. Reedyk 《湖泊科学》1998,10(S1):25-30

Surface waters in western Canada often experience eutrophication-related problems with water quality, specifically high internal phosphorus loading rates and excessive phytoplankton and macrophyte production, that lead to water column anoxia and restricted fisheries habitat. A group of researchers from across Canada were involved for a seven-year period in cooperative programs for surface water quality management in western Canada, based at the University of Alberta. This paper summarises information on two techniques, hypolimnetic oxygenation and lime (Ca₂CO₃ and Ca(OH)₂) application, used in western Canada (specifically, the province of Alberta) to manage eutrophication in standing waters (lakes and reservoirs).  相似文献   

A Type-Curve Method for the Analysis of Pumping Tests with Piecewise-Linear Pumping Rates     

Chao Zhuang  Yabing Li  Zhifang Zhou  Walter A. Illman  Zhi Dou  Jinguo Wang  Long Yan 《Ground water》2020,58(5):788-798

Aquifer hydraulic parameters are commonly inferred from constant-rate pumping tests, while variable pumping rates are frequently encountered in actual field conditions. In this study, we propose a generally applicable dimensionless form of the analytical solution for variable-rate pumping tests in confined aquifers. In particular, we adopt a piecewise-linear fitting of variable pumping rates and propose a new type-curve method for estimating the hydraulic conductivity (K ) and specific storage (S_s ) of the investigated confined aquifer. For each test, a series of type curves, which depend on the variable pumping rates, the location of observation wells and the introduced first dimensionless inflection time, need to be provided for matching the observed drawdown data on a log-log graph. We first demonstrate the applicability and robustness of this method through a synthetic pumping test. Subsequently, we apply this method to analyze drawdown data from four pumping tests conducted within a multilayered aquifer/aquitard system in Wuxi city, Jiangsu Province, China. The parameter estimates are then compared with those reported by PEST. The K and S_s values estimated by the new type-curve method are found to be quite close to PEST-based estimates. Parameter estimation results demonstrate the difference in K and S_s values between observation wells. The difference could be attributed to the spatial heterogeneity in K and S_s . A future research topic may focus on the characterization of K and S_s heterogeneity with the currently available drawdown data from variable-rate pumping tests.  相似文献   

阿巴拉契亚造山带(纽芬兰岛)阿克利巨型花岗岩基地球化学填图及其成矿制约     

王朝阳  王涛  林寿发  Cees van Staal 《地质学报》2022,96(2):517-532

阿巴拉契亚造山带加拿大纽芬兰岛东南部发育一晚泥盆纪阿克利巨型花岗岩基(～2500 km2).该岩基侵位于甘德和阿瓦隆地块的多佛-赫米蒂奇湾巨型断层带之间,内部发育钨-锡-钼矿床及相关的矿化.本文锆石年代学研究显示,岩基中Tolt单元侵位于378±2 Ma,各单元年龄基本一致,为同期岩浆多次侵位的产物.岩基中主要岩石类型...  相似文献