Development and application of a catchment scale diffuse nitrate modelling tool     

Shuming Liu  Peter Tucker  Martin Mansell  Andrew Hursthouse 《水文研究》2005,19(13):2625-2639

Water pollution from diffuse sources is a problem of increasing concern. Efforts to control diffuse pollution have been confined mainly to agricultural land and forests. Little attention has been paid to sources of diffuse pollution from urban areas. A diffuse nitrate modelling tool (DNMT) has been developed for modelling the fate of nitrate in urban areas. This tool works at the catchment scale and has a modular structure that consists of three components: the hydrological module, the nitrogen cycle module and the nitrate transport module. The hydrological model describes the possible flow pathways. The nitrogen cycle model accounts for the mass balance of nitrate and calculates the amount of nitrate for potential loss. The nitrate transport module simulates the movement of nitrate within and from the soil to the receiving water. This paper demonstrates the development of the tool and its application in the White Cart Water catchment. This implementation of the tool shows that it has a good capability for simulating the fate of nitrate in urban catchments. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Response of surface water chemistry to reduced levels of acid precipitation: comparison of trends in two regions of New York,USA     

Douglas A. Burns  Michael R. McHale  Charles T. Driscoll  Karen M. Roy 《水文研究》2006,20(7):1611-1627

In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984–2001 and 1992–2001) and surface water chemistry (1992–2001) were determined in two of the most acid‐sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO₄^2?), nitrate (NO₃^?), and base cation (C_B) concentrations and increasing pH during 1984–2001, but few significant trends during 1992–2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO₄^2? concentrations at all sites, and decreasing trends in NO₃^?, C_B, and H⁺ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid‐neutralizing capacity (ANC) increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO₄^2? trends, but it caused several significant non‐flow‐corrected trends in NO₃^? and ANC to become non‐significant, suggesting that trend results for flow‐sensitive constituents are affected by flow‐related climate variation. SO₄^2? concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation–surface water comparisons, reflecting a strong link between S emissions, precipitation SO₄^2? concentrations, and the processes that affect S cycling within these regions. NO₃^? and H⁺ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation–surface water comparisons, indicating that variation in local‐scale processes driven by factors such as climate are affecting trends in acid–base chemistry in these two regions. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

硝酸益康唑微囊化技术研究     

范润珍  邱小玲  叶玉儿  巫结顺 《广东海洋大学学报》2006,26(3):74-77

以明胶与阿拉伯胶配比为囊材,Span60为乳化剂,戊二醛为交联剂,采用复凝聚法制备了硝酸益康唑微胶囊,并研究了制备工艺条件对微胶囊形态、粒度、药物包封率及释放特性的影响。结果表明,随药物与囊材配比增大,形成的微胶囊数目越多、粒径越小,包封率降低,释放速度增大;戊二醛的用量对微胶囊膜的机械强度、微胶囊形状和粒度及分散性有显著影响。  相似文献   

Nutrient distributions in an estuary: Evidence of chemical precipitation of dissolved silicate and phosphate     

A.W. Morris  A.J. Bale  R.J.M. Howland 《Estuarine, Coastal and Shelf Science》1981,12(2):205-216

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Relationship of topography to surface water chemistry with particular focus on nitrogen and organic carbon solutes within a forested watershed in Hokkaido,Japan     

Akiko Ogawa  Hideaki Shibata  Kei Suzuki  Myron J. Mitchell  Yoshiyuki Ikegami 《水文研究》2006,20(2):251-265

We studied the relationships between streamwater chemistry and the topography of subcatchments in the Dorokawa watershed in Hokkaido Island, northern Japan, to examine the use of topography as a predictor of streamwater chemistry in a watershed with relatively moderate terrain compared with other regions of Japan. Topographic characteristics of the Dorokawa watershed and its subcatchments were expressed as topographic index (TI) values, which ranged from 4·5 to 20·4 for individual grid cells (50 × 50 m²), but averaged from 6·4 to 7·4 for the 20 subcatchments. Streamwater samples for chemical analyses were collected four times between June and October 2002 from 20 locations in the watershed. The pH of water that passed through the watershed increased from ～5·0 to 7·0, with major increases in Na⁺ and Ca²⁺ and marked decreases in NO₃^? and SO . Distinctive spatial patterns were observed for dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and NO₃^? concentrations of streamwater across the watershed. Statistical analyses indicated significant linear relationships between the average TI values of subcatchments and DOC, DON, and NO₃^? concentrations. Furthermore, the proportion of DOC in streamwaters in the wet season increased with TI values relative to other nitrogen species, whereas NO₃^? concentrations decreased with TI. The gradients of soil wetness and the presence of wetlands explained many of the observed spatial and temporal patterns of DOC, DON, and NO₃^? concentrations in the surface waters of the Dorokawa watershed. Our results suggest that the TI is especially useful for predicting the spatial distribution of DOC, DON and NO₃^? in the surface waters of Hokkaido, where topographical relief is moderate and wetlands more common than in other regions of Japan. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

热分解法测定水盐体系中硝酸铵和水含量研究          下载免费PDF全文

汪琼  俞秀丽  尹霞  曾德文 《盐湖研究》2012,20(4):25-29

针对复杂硝酸铵水盐体系溶解度的测定,传统分析方法操作步骤繁琐,且试剂较贵,引入一种简单准确的分析方法,即热分解法,对LiNO3-KNO3-NH4NO3-H2O体系和NaNO3-KNO3-NH4NO3-H2O体系中硝酸铵和水的含量进行精确分析。结果表明,热分解温度控制在230～240℃,若控制样品质量为1.5 g,分解时间不低于36 h,能将LiNO3-KNO3-NH4NO3-H2O体系中的硝酸铵和水彻底分解,且随着样品中硝酸铵含量增加,热分解时间也将延长,分析相对误差能控制在0.2%以内。针对复杂NaNO3-KNO3-NH4NO3-H2O体系,热分解温度控制在230～255℃,若控制样品质量为1.5 g,分解时间不少于44 h,且随着样品中硝酸铵含量的增加,相应延长热分解时间,能将复杂NaNO3-KNO3-NH4NO3-H2O体系中的硝酸铵和水彻底分解,分析相对误差能控制在0.2%以内。  相似文献   

High spatial-resolution monitoring to investigate nitrate export and its drivers in a mesoscale river catchment along an anthropogenic land-cover gradient     

Izabela Bujak  Christin Müller  Ralf Merz  Kay Knöller 《水文研究》2021,35(12):e14361

Nitrate monitoring is commonly conducted with low-spatial resolution, only at the outlet or at a small number of selected locations. As a result, the information about spatial variations in nitrate export and its drivers is scarce. In this study, we present results of high-spatial resolution monitoring conducted between 2012 and 2017 in 65 sub-catchments in an Alpine mesoscale river catchment characterized by a land-use gradient. We combined stable isotope techniques with Bayesian mixing models and geostatistical methods to investigate nitrate export and its main drivers, namely, microbial N turnover processes, land use and hydrological conditions. In the investigated sub-catchments, mean values of NO₃⁻ concentrations and its isotope signatures (δ¹⁵N_NO3 and δ¹⁸O_NO3) varied from 2.6 to 26.7 mg L⁻¹, from −1.3‰ to 13.1‰, and from −0.4‰ to 10.1‰, respectively. In this study, land use was an important driver for nitrate export. Very strong and strong positive correlations were found between percentages of agricultural land cover and δ¹⁵N_NO3, and NO₃⁻ concentration, respectively. Mean proportional contributions of NO₃⁻ sources varied spatially and seasonally, and followed land-use patterns. The mean contribution of manure and sewage was much higher in the catchments characterized by a high percentage of agricultural and urban land cover comparing to forested sub-catchments. Specific NO₃⁻ loads were strongly correlated with specific discharge and moderately correlated with NO₃⁻ concentrations. The nitrate isotope and concentration analysis results suggest that nitrate from external sources is stored and accumulated in soil storage pools. Nitrification of reduced nitrogen species in those pools plays the most important role for the N-dynamics in the Erlauf river catchment. Consequently, nitrification of reduced N sources was the main nitrate source except for a number of sub-catchments dominated by agricultural land use. In the Erlauf catchment, denitrification plays only a minor role in controlling NO₃⁻ export on a regional scale.  相似文献   

细菌反硝化法测试硝酸盐氮、氧同位素的研究与应用          下载免费PDF全文

崔坤磊  尹希杰  李艳利  杨海丽  裴盛祥  苏静 《应用海洋学学报》2021,40(4):629-635

为了验证细菌反硝化法对水体中硝酸盐氮、氧同位素组成测定的适用性、重现性及准确性, 在不同时间(2019年7月28日、8月19日、8月26日)利用反硝化细菌分别将海水、湖水和自来水样品中的硝酸盐转化为氧化亚氮（N₂O）, 并进行氮、氧同位素测定。结果表明, 不同时间段3个批次实验的硝酸盐氮同位素校准曲线斜率都接近理论值1, 相关性系数均高于0.999, 说明反硝化细菌在将样品中的硝酸盐全部还原为N₂O的过程中氮同位素分馏效应很小; 同一样品3个批次测定的硝酸盐的氮同位素值基本相同, 表明细菌反硝化法对硝酸盐氮同位素的测定在长时间周期内具有很好的重现性和准确性。3个批次氧同位素校准曲线斜率稳定在0.61～0.63之间, 相关性系数均高于0.99, 单批次内海水、湖水和自来水3类样品中硝酸盐氧同位素比值的标准偏差范围在0.18‰～0.69‰之间, 表明经过氧同位素校准曲线的校正, 可以准确反映样品中硝酸盐氧同位素组成; 同一样品3个批次测定的氧同位素值差异较大, 其变化范围为1.33‰～16.38‰, 可能是由于样品储存过程中硝酸盐与水之间发生的氧同位素交换作用所致。  相似文献   

铵锌镉还原法测试硝酸盐氮、氧同位素方法研究          下载免费PDF全文

尹希杰  杨海丽  郭浩然  陈淳青  崔坤磊 《应用海洋学学报》2021,40(4):721-727

本研究利用铵锌镉还原法将海水、湖水和自来水水体中硝酸盐转化为N₂O气体测试氮、氧同位素, 结果表明当反应体系的pH值在6～8之间, NO₃^-还原为NO₂^-的转化率大于95%, NO₂^-还原为N₂O的转化率大于99%。配置5种丰度的硝酸盐氮、氧同位素标样, 将实验结果与理论值绘制校准曲线, 氮同位素校准曲线斜率为0.48, 相关性良好(R²=0.999 8), 5种丰度δ¹⁵N_N2O标准偏差在0.18‰～0.43‰之间(n=5);氧同位素校准曲线斜率为0.70, 相关性良好(R²=0.999 6), 5种丰度δ¹⁸O_N2O标准偏差在0.27‰～0.46‰之间(n=5)。铵锌镉还原法与镉柱还原法测定硝酸盐氮、氧同位素结果的精密度和准确度一致, 同时海水、湖水和自来水3种不同类型水样的硝酸盐氮、氧同位素测试数据满足实验要求, 而且在实验流程的简洁性和高效性方面更具优势。  相似文献   

Watershed-scale vegetation,water quantity,and water quality responses to wildfire in the southern Appalachian mountain region,United States     

Peter V. Caldwell  Katherine J. Elliott  Ning Liu  James M. Vose  David R. Zietlow  Jennifer D. Knoepp 《水文研究》2020,34(26):5188-5209

Wildfires are landscape scale disturbances that can significantly affect hydrologic processes such as runoff generation and sediment and nutrient transport to streams. In Fall 2016, multiple large drought-related wildfires burned forests across the southern Appalachian Mountains. Immediately after the fires, we identified and instrumented eight 28.4–344 ha watersheds (four burned and four unburned) to measure vegetation, soil, water quantity, and water quality responses over the following two years. Within burned watersheds, plots varied in burn severity with up to 100% tree mortality and soil O-horizon loss. Watershed scale high burn severity extent ranged from 5% to 65% of total watershed area. Water quantity and quality responses among burned watersheds were closely related to the high burn severity extent. Total water yield (Q) was up to 39% greater in burned watersheds than unburned reference watersheds. Total suspended solids (TSS) concentration during storm events were up to 168 times greater in samples collected from the most severely burned watershed than from a corresponding unburned reference watershed, suggesting that there was elevated risk of localized erosion and sedimentation of streams. NO₃-N concentration, export, and concentration dependence on streamflow were greater in burned watersheds and increased with increasing high burn severity extent. Mean NO₃-N concentration in the most severely burned watershed increased from 0.087 mg L⁻¹ in the first year to 0.363 mg L⁻¹ (+317%) in the second year. These results suggest that the 2016 wildfires degraded forest condition, increased Q, and had negative effects on water quality particularly during storm events.  相似文献