Are temporal variations in the nitrate content of UK upland freshwaters linked to the North Atlantic Oscillation?     

D. T. Monteith  C. D. Evans  B. Reynolds 《水文研究》2000,14(10):1745-1749

Synchronous patterns of variation in NO₃ concentration, observed in upland lakes and streams across gradients of climate, altitude, land use and nitrogen deposition over the last decade, show a strong negative correlation with winter values for the North Atlantic Oscillation Index and mean winter temperature. Variations in a longer term stream NO₃ record validate this relationship, and although mechanisms are yet unclear, may be linked to the length of time the soil profile remains frozen during the winter. These findings are of particular significance to our understanding of the relationship between atmospheric N deposition and concentrations and fluxes of NO₃ in runoff, and the potential response to future climatic changes. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Spatial and temporal variations in surface water nitrate concentrations in a mixed land use catchment under humid temperate climatic conditions     

Y Van Herpe  P. A Troch 《水文研究》2000,14(14):2439-2455

Streamwater nitrate (NO^―₃) concentrations along the main stream and at the outlet of several subcatchments within the 114\3 km² Zwalm watershed in Flanders, Belgium, have been monitored regularly since 1991. Land use within the Zwalm catchment is predominantly agricultural, with forested regions in the south and urban concentrations in the north‐east of the catchment. Streamwater NO^―₃ concentrations increased with increases in stream discharge rates, but in general, discharge rate explained only about 30% of the variation in NO^―₃ concentrations. The low R² values were attributed to the observed anticlockwise hysteresis in the NO^―₃ concentration – discharge relationship and to differences in NO^―₃ concentrations between both seasonal flow and various flow regimes, with winter flow explaining 51% of the variation in NO^―₃ concentrations, whereas summer flow explained only 28% of the variation. A hypothesis was formulated in which flow regime accounts for the seasonal variation in NO^―₃ export, postulating that the catchment seasonally alternates between two hydrological stages. The first stage occurs during wet winter periods, when the catchment drains as a single source area, whereas the second stage occurs during dry summer periods, when the groundwater store disconnects into separate subcatchments. This causes NO^―₃ concentration peaks to be more delayed during summer storm events compared with winter storm events. Regarding flow regimes, differences between high and low flow conditions and between increasing and stable/decreasing flow were not as pronounced a differences between seasons. In contrast to the estimation of NO^―₃ concentrations, discharge was a strong predictor (R²= 0\71) of the NO^―₃ flux within the tributaries of the Zwalm catchment. The NO^―₃ concentrations in the main stream increased with decreasing elevation, whereas the seasonal concentration patterns along the main channel were similar to those observed at the outlet. NO^―₃ concentrations varied considerably among catchments and showed a high variability over time, although in general, the variation in NO^―₃ concentration was higher between catchments than within catchments. The impact of land use is clearly reflected in the streamwater NO^―₃ concentrations, although NO^―₃ concentration patterns were also affected by topography and, to a lesser extent, by soil type. A gradual increase in NO^―₃ concentrations at the outlet of the Zwalm catchment could be observed throughout the 1991 – 1998 study period, providing evidence for the general trends of increase in Flanders, which are attributed to the intensification of agricultural activities. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Component flow processes at four streams in the Catskill Mountains,New York,analysed using episodic concentration/discharge relationships     

C. Evans  T. D. Davies  P. S. Murdoch 《水文研究》1999,13(4):563-575

Plots of solute concentration against discharge have been used to relate stream hydrochemical variations to processes of flow generation, using data collected at four streams in the Catskill Mountains, New York, during the Episodic Response Project of the US Environmental Protection Agency. Results suggest that a two‐component system of shallow and deep saturated subsurface flow, in which the two components respond simultaneously during hydrologic events, may be applicable to the study basins. Using a large natural sea‐salt sodium input as a tracer for precipitation, it is argued that an additional distinction can be made between pre‐event and event water travelling along the shallow subsurface flow path. Pre‐event water is thought to be displaced by infiltrating event water, which becomes dominant on the falling limb of the hydrograph. Where, as appears to be the case for sulfate, a solute equilibrates rapidly within the soil, the pre‐event–event water distinction is unimportant. However, for some solutes there are clear and consistent compositional differences between water from the two sources, evident as a hysteresis loop in concentration–discharge plots. Nitrate and acidity, in particular, appear to be elevated in event water following percolation through the organic horizon. Consequently, the most acidic, high nitrate conditions during an episode generally occur after peak discharge. A simple conceptual model of episode runoff generation is presented on the basis of these results. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Temporal trends of bulk precipitation and stream water chemistry (1977–1997) in a small forested area,Krusné hory,northern Bohemia,Czech Republic     

N. E. Peters  Jiri Cerny  Miroslav Havel  Radovan Krejci 《水文研究》1999,13(17):2721-2741

The Krusné hory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long‐term routine sampling of bulk precipitation (1977–1996) and stream water (1977–1998) in a forested area on the south‐eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux with respect to controlling processes. From 1977 to 1996, the annual volume‐weighted Ca²⁺ and SOconcentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume‐weighted concentrations decreased for most solutes, except H⁺. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H⁺ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H⁺, Ca²⁺, Mg²⁺, SONOwere highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased more gradually from 1983 to 1998. The spruce forest die‐back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca²⁺ concentrations occurred after 1995 and may be due to the depletion of Ca²⁺, which was provided by catchment liming in 1986, 1988 and 1989. Solute flux trends in bulk atmospheric deposition and stream water generally were not significant and the lack of trend is attributed to the large interannual variability in precipitation quantity and runoff, respectively. All solutes except Na⁺ varied seasonally. The average seasonal concentrations varied between the solutes, but for most solutes were highest in winter and spring and lowest in summer, correlating with the seasonal trend in runoff. For Ca²⁺, Mg²⁺ and SOthe concentration minimum occurs in September and the maximum occurs in February or March, correlating with the seasonal baseflow. These solutes are primarily controlled by the contribution of soil water and groundwater to stream flow. During snowmelt, the meltwater generally causes concentrations to decrease as soil water and groundwater are diluted. For NO₃ , average minimum concentrations occur in August at the end of the growing season concurrent with the lowest stream flow, and the maximum occurs in February and March with high stream flow during snowmelt. Seasonal stream water NOconcentration variations are large compared with the long‐term decrease. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Assessing impacts of cemeteries on water quality in an urban headwater watershed with mixed human-built infrastructure     

Samuel Nesheim  Zhongjie Yu  Samuel Tuttle  Jenna Klein  Tao Wen 《水文研究》2024,38(3):e15128

Cemeteries are understudied integral components to urban watersheds, which provide ecosystem services but can also export nutrients, trace elements, and other contaminants to nearby water bodies. In this study, we focus on Meadowbrook Creek, an urban headwater stream in Syracuse, New York (USA), which has shown significant nitrate contributions from a local cemetery. We collected biweekly surface water samples over the course of 1 year from 2022 to 2023 for analysis of major and trace elemental concentrations including Na, Ca, Mg, K, F, Cl, sulfate, and nitrate. Here, we aim to assess the impact of various human infrastructures on urban stream water quality with a particular focus on the cemetery and nitrate. A comparison between the new dataset in this study and previously reported water chemistry data in Meadowbrook in 2012 suggests a decade-long impact of road salting and the cemetery on water quality particularly with respect to Na, Cl, and nitrate. Sulfate, Mg, Ca, and K are likely mainly geogenic. Stable nitrogen isotope data, the usage of concrete or steel vaults in the cemetery in the past 50 years, and the lack of correlation between nitrate and fluoride concentrations in stream water argue against burial decay products being a major source of nitrate to the stream. Instead, other nitrate sources that exist in the cemetery such as, fertilizer, decaying plant material, and wastewater, are more viable dominant nitrate sources. In addition, nitrate loading calculations indicate that the groundwater-connected reach, including the cemetery, acts as an annual net sink for nitrate despite the seasonally varying sink-source patterns.  相似文献   

地下水硝酸盐污染研究综述   总被引：37，自引：0，他引：37  

陈建耀  王亚  张洪波  赵新峰 《地理科学进展》2006,25(1):34-44

地下水为重要的资源,一旦受污染,将难以更新与恢复。近年来,地下水硝酸盐污染问题正日益受到国内外研究者的关注。关于这方面的研究主要在以下方面：地下水硝酸盐的转化过程与机理;地下水硝酸盐污染的来源以及避免污染的方法措施;地下水硝酸盐氮、亚硝酸盐氮的确定方法;如何减少或者除去地下水中的硝酸盐;另外还有一些地下水硝酸污染与人体健康的研究等。在综述有关文献的基础上,提出未来地下水硝酸盐污染的三个方向：水与硝酸盐运移的耦合;界面过程;人文影响与全球角度。  相似文献   

东海北部营养盐分布的季节变化及成因探讨   总被引：2，自引：0，他引：2  

张建平  康建成  任惠茹  李卫江  谢小进 《海洋科学》2010,34(1):35-43

基于美国国家海洋大气管理局(NOAA)2007年发布的全球海域营养盐数据库资料和美国国家地球物理数据中心(NGDC)2006年发布的全球地貌数据库资料,在MATLAB计算机平台上,利用研发的数值分析与成图技术,对东海北部海域营养盐分布的季节变化特征进行分析。结果表明:(1)东海北部海域NO3--N、PO43--P分布总特征为由沿岸向离岸递减,由表层向底层递增;西北高,东南低,呈扇形向东南扩展;SiO3--Si有两个浓度高值区,一个为研究区域的西北角,另一个在东北角;(2)在0~50 m的表层营养盐平均浓度均是冬季最高;50~200 m的中层NO3--N、SiO3--Si夏季最高;200 m以下的底层四季变化微弱,其中400~500m层PO43--P、SiO3--Si浓度值秋季最高。NO3--N变异系数表层最大,PO3--P中层最大、SiO3--Si底层最大,其中NO3--N相应各层变异系数大于PO43--P、SiO3--Si;(3)研究区域四季均存在高营养盐水团。高PO43--P、SiO3--Si水团中心分别位于125.5°E、30.5°N和128.5°E、30.5°N;高NO3--N水团中心,随冬-春-夏-秋、从南往东北再向西、最后向东南,在125°~128°E、29°~31°N范围内移动。  相似文献   

以可生物降解聚合物为碳源去除海水闭合循环养殖系统中的硝酸盐     

谭洪新  赖才胜  罗国芝  孙大川  阮赟杰  周炜 《海洋科学》2010,34(6):22-27

针对海水闭合循环养殖系统废水脱氮过程中低C/N的问题,采用室内试验装置,研究了以可生物降解聚合物材料(BDPs)PBS为碳源和生物膜载体的填料床反应器对含盐水体中硝酸盐的去除效果及其影响因素。结果表明,反应器能有效去除含盐水体中的硝酸盐,出水DOC浓度小,出水pH值随反硝化反应的进行有上升的趋势。温度和水力停留时间对反应器的脱氮效率影响较大,在温度为14~30℃范围内,温度为30℃时的反硝化速率比14℃时的2倍还要大,反硝化温度常数为0.039;水力停留时间对NO3?-N去除率起重要作用,NO3?-N去除率随水力停留时间的延长而提高。进水NO3?-N浓度对反应器的处理效率有一定影响,浓度过高会导致NO3?-N去除率下降。反应器对进水pH值和DO冲击负荷的适应能力很强,当进水pH值在5.0~9.0与进水DO在2.1~6.8 mg/L范围内变化时,反应器的NO3?-N去除率基本没有变化。  相似文献   

硝酸钠改良半咸水凡纳滨对虾(Litopenaeus vannamei)池塘底质和水质的研究          下载免费PDF全文

江兴龙  关瑞章  Claude E. Boyd 《海洋与湖沼》2009,40(5):557-562

采用在8口土池开展半咸水养殖凡纳滨对虾施用NaNO3对比实验的方法,进行了硝酸钠对半咸水对虾养殖池塘底质和水质的改良效果、机理及应用前景的研究。结果表明,NaNO3处理组显著提高了池塘底泥表层的氧化还原电位,显著降低了底泥的BOD5和可利用磷的浓度;显著降低了池塘水中的蓝藻相对密度;处理组的养殖成活率、产量和饲料系数分别比对照组显著提高8.2%、10.1%和降低9.2%(P<0.05);处理组养殖效益明显高于对照组,每公顷池塘养虾净增加收入人民币9765元;NaNO3的施用起到了有效改良池塘底质和水质的作用。因此,NaNO3的应用可为半咸水对虾养殖池塘底质和水质的改良开辟一个新的途径,具有一定的应用前景。  相似文献   

胶体磷在河口区随盐度变化的研究   总被引：1，自引：0，他引：1       下载免费PDF全文

陈丁  郑爱榕  陈敏 《海洋学报》2009,31(1):71-78

研究了胶体磷在河口海区随盐度变化的趋势,并将其与颗粒态、真溶解态磷随盐度的变化趋势进行对比,分析胶体态磷在河口的行为与颗粒态磷和真溶解态磷二者的异同。探讨磷在颗粒相、胶体相和真溶液相之间的分配及其与悬浮颗粒物浓度的关系,研究胶体磷在河口海区中的迁移转化作用。研究结果表明,胶体相中总磷、有机磷和活性磷浓度由河端向海端降低,表明陆源输入是其主要来源。胶体有机磷占总磷比例随盐度增加而下降,表明有机磷受胶体去除过程的影响较明显,胶体磷在河口海区的浓度变化趋势及胶体中有机磷和活性磷的比例都与真溶解相接近而与颗粒相差别较大。  相似文献