The impact of pipe flow in riparian peat deposits on nitrate transport and removal     

Alan R. Hill 《水文研究》2012,26(20):3135-3146

The effect of preferential flow in soil pipes on nitrate retention in riparian zones is poorly understood. The characteristics of soil pipes and their influence on patterns of groundwater transport and nitrate dynamics were studied along four transects in a 1‐ to >3‐m deep layer of peat and marl overlying an oxic sand aquifer in a riparian zone in southern Ontario, Canada. The peat‐marl deposit, which consisted of several horizontal layers with large differences in bulk density, contained soil pipes that were generally 0.1 to 0.2 m in diameter and often extended vertically for 1 to >2 m. Springs that produced overland flow across the riparian area occurred at some sites where pipes extended to the peat surface. Concentrations of NO₃^?–N (20–30 mg L^?1) and dissolved oxygen (DO) (4–6 mg L^?1) observed in peat pipe systems and surface springs were similar to values in the underlying sand aquifer, indicating that preferential flow transported groundwater with limited nitrate depletion. Low NO₃^?–N concentrations of <5 mg L^?1 and enriched δ¹⁵N values indicated that denitrification was restricted to small areas of the peat where pipes were absent. Groundwater DO concentrations declined rapidly to <2 mg L^?1 in the peat matrix adjacent to pipes, whereas high NO₃^?–N concentrations of >15 mg L^?1 extended over a larger zone. Low dissolved organic carbon values at these locations suggest that supplies of organic carbon were not sufficient to support high rates of denitrification, despite low DO conditions. These data indicate that it is important to develop a greater understanding of pipes in peat deposits, which function as sites where the transport of large fluxes of water with low biogeochemical reaction rates can limit the nitrate removal capacity of riparian zones. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

浅谈地下水硝酸盐污染   总被引：5，自引：0，他引：5  

浮海梅  金云霄 《地下水》2009,31(3):85-87,119

地下水不仅是水文循环的一个重要组成部分,还是人类的一种重要淡水资源,尤其是对于郊区和农村地区的用水.现在,地表水水源普遍受到污染,人类对地下水的依赖程度不断增加.目前我国的地下水资源污染严重.全国多数城市的地下水都不同程度的受到了点源和面源污染,多种元素超标,"三氮"污染最为严重[1].通过对地下水硝酸盐污染现状、危害和来源的分析,提出地下水硝酸盐污染的控制对策.  相似文献   

胶态微泡沫在非饱和多孔介质中的迁移规律及影响因素     

秦传玉  郭超  何宇 《吉林大学学报(地球科学版)》2019,49(6):1732-1740

传统原位土壤淋洗修复存在淋洗效率低、淋洗液迁移难控制、污染范围易扩大的弊端。胶态微泡沫（CGAs）密度轻、粒径小、流动性好,可以有效解决传统液相淋洗修复中的问题。在修复过程中,压力作为一项重要的指标,可以有效地反映CGAs在介质中的迁移分布;因而本研究通过一维和二维动态模拟实验探讨了介质粒径、介质含水量、聚合物（黄原胶）添加等对土壤修复体系压力的影响以及CGAs在土壤中的运移规律。研究表明：随着介质粒径、介质含水量、黄原胶质量浓度的增大,体系中压力总体呈现降低趋势;CGAs从模拟槽一侧单点注入介质时,其在介质中的迁移轨迹呈现近似半圆形,在覆盖区域分布均匀,能够有效克服重力对其迁移分布的影响;随着介质粒径的增大,CGAs在介质中的波及效率先增大后减小,介质粒径为0.8~1.0 mm时波及效率最大,为34.77%;随着含水量的增加,CGAs的波及效率随之增加;黄原胶的添加有效增加了CGAs在介质中的波及效率,黄原胶质量浓度为500 mg/L时CGAs波及效率最大,为40.28%,是未添加黄原胶时的1.48倍。  相似文献   

基于有机-无机杂化材料的硝酸还原酶电极的研究     

赵林  于洋  闫博  谭欣  李若璞 《吉林大学学报(地球科学版)》2007,37(2):355-360

在制备由聚乙烯醇和二氧化硅溶胶凝胶掺杂而成的有机-无机杂化材料的基础上,将硝酸还原酶用此杂化材料包埋固定在金盘电极上,利用甲基紫精为电子媒介体,制得高性能的安培型硝酸还原酶电极。此酶电极可以在-0.68 V（SCE）下对硝酸根进行测定,最适pH值为7.0,载酶量为7.2 mU。在选定的工作条件下,此酶电极的灵敏度和线性范围分别为2.53 nA/(μmol·L^-1)和0.01～0.36 mmol/L ,平均响应时间为12.1 s左右。  相似文献   

Daily Variations in Nutrient Concentrations of Seawater at 321 m Depth in Toyama Bay, Japan Sea     

Masami Watanabe  Jun Ohtsu  Akira Otsuki 《Journal of Oceanography》2000,56(5):553-558

Nutrient concentrations (nitrate + nitrite, phosphate and silicate) in deep seawater (321 m depth) of Toyama Bay, Japan, were measured from August 1996 to July 1997 to determine the magnitude of daily variations. Significant daily variations were observed; concentrations ranged from 4.42 to 22.4 µM for nitrate + nitrite, from 0.86 to 1.98 µM for phosphate, and from 9.91 to 47.7 µM for silicate, respectively. However, there were not significant relationships between nutrient concentrations and water temperature, or between nutrients and salinity. Since temperature and salinity in the >300 m depth layer were constant through the year, the results suggest that there may be water masses with different nutrient concentrations in the deep layers (at about 320 m depth) of the bay, and a horizontal advection of these water masses may be responsible for the observed daily variations.  相似文献   

半封闭虾池中三氮与溶解氧含量关系的数学模型   总被引：1，自引：0，他引：1  

李兰生  李冰  林洪  卢敬让  赵军  鞠悦 《海洋湖沼通报》2000,(1):52-59

１９９６年４月～１９９８年７月,我们采用次溴酸钠氧化法对胶州湾中的两个半封闭式的虾 池中氮元素的含量时行了实验测试,分别通过将各态氮氧化或还原为ＮＯ２－态氮的方法测定不同时期虾池中ＮＨ４＋＋ＮＨ３态Ｎ,ＮＯ３－戊Ｎ,ＮＯ２－态Ｎ,总Ｎ的含量,并对水中其它一些影响虾池水质状况及其变化的物理化学因子,包括ＰＨ值,溶解氧（ＤＯ）、温度、盐度等进行了测定。得到在不同理化指标下各价态氮营养盐的含量和变化趋势  相似文献   

Factors controlling groundwater chemistry in an agricultural area with complex topographic and land use patterns in mid‐western South Korea     

Dong‐Chan Koh  Eun‐Young Kim  Jong‐Sik Ryu  Kyung‐Seok Ko 《水文研究》2009,23(20):2915-2928

Shallow and bedrock groundwater from granitic aquifers were investigated for the hydrogeochemistry of major and minor constituents in an agricultural area. Nitrate concentrations were observed up to 49 mg/l as NO₃‐N, with 22% of samples exceeding the drinking water standard, which could pose a significant threat because most residents rely on groundwater as their drinking water source. Principal component analysis revealed three principal components (PCs): (1) nitrate contamination, contributed by major cations, Cl^?, SO and NO , (2) reduction processes positively involving Fe, Mn and B, and negatively involving dissolved oxygen and NO and (3) natural mineralization, involving HCO and F^?. Cluster analysis, performed on the PC scores, resulted in seven sample groups, which were successfully identified by total depth, elevation and land use. The nitrate‐contaminated groups had mixed land uses, with locally concentrated residential areas. Uncontaminated groundwater groups were found in the natural environment, including high‐altitude spring water and bedrock groundwater with a higher degree of natural mineralization. Shallow groundwater groups in paddy fields in lowlands were affected by reducing environments, of which one group was characterized by high Fe, Mn and B, and negligible nitrate. Groundwater with intermediate nitrate and lower Cl^? and SO was found primarily in hilly terrains with orchards and vegetable gardens, indicating lower contaminant loadings than lowland areas. Higher concentrations of F^? and nitrate were observed in the nitrate‐contaminated water, which seemed unlikely to be explained by groundwater mixing. The strong acidity generated from nitrification may infiltrate deeper into the aquifer, induce accelerated weathering of bedrock and result in the coexistence of F^? and nitrate, which may be an evidence of intense nitrate loading, leading to soil acidification. Multivariate statistical analysis successfully delineated hydrochemical characteristics of groundwater attained by natural and anthropogenic processes in an agriculturally stressed area with complex topographic land use patterns. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Factors controlling nitrogen release from two forested catchments with contrasting hydrochemical responses     

Sheila F. Christopher  Myron J. Mitchell  Michael R. McHale  Elizabeth W. Boyer  Douglas A. Burns  Carol Kendall 《水文研究》2008,22(1):46-62

Quantifying biogeochemical cycles of nitrogen (N) and the associated fluxes to surface waters remains challenging, given the need to deal with spatial and temporal variability and to characterize complex and heterogeneous landscapes. We focused our study on catchments S14 and S15 located in the Adirondack Mountains of New York, USA, which have similar topographic and hydrologic characteristics but contrasting stream nitrate ( ) concentrations. We characterized the mechanisms by which reaches the streams during hydrological events in these catchments, aiming to reconcile our field data with our conceptual model of factors that regulate nutrient exports from forested catchments. Combined hydrometric, chemical and isotopic (δ ) data showed that the relative contributions of both soil and ground water sources were similar between the two catchments. Temporal patterns of stream chemistry were markedly different between S14 and S15, however, because the water sources in the two catchments have different solute concentrations. During late summer/fall, the largest source of in S14 was till groundwater, whereas shallow soil was the largest source in S15. concentrations in surface water decreased in S14, whereas they increased in S15 because an increasing proportion of stream flow was derived from shallow soil sources. During snowmelt, the largest sources of were in the near‐surface soil in both catchments. Concentrations of increased as stream discharge increased and usually peaked before peak discharge, when shallow soil water sources made the largest contribution to stream discharge. The timing of peaks in stream concentrations was affected by antecedent moisture conditions. By elucidating the factors that affect sources and transport of N, including differences in the soil nutrient cycling and hydrological characteristics of S14 and S15, this study contributes to the overall conceptualization of release from temperate forested catchments. Copyright © 2007 John Wiley & Sons, Ltd.  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   

国外无氯钾肥研究及应用动态   总被引：3，自引：0，他引：3  

许文娟 《化工矿产地质》2000,22(2):86-90

近年来无氯钾肥 (硫酸钾、硝酸钾、钾镁硫酸盐复合肥等 )在农业上的应用品种及数量不断增加。智利、埃及、以色列、约旦、墨西哥、美国等在开采钾矿开发计划中 ,都列入了无氯钾肥的项目。世界上一些主要钾盐生产商不断改进相关的生产工艺并开发出无氯钾盐的新产品。这些研究及应用动态 ,值得关注。  相似文献