Assessment of the quantitative and qualitative buffer function of an alluvial wetland: hydrological modelling of a large floodplain (Garonne River,France)     

P. Weng  J. M. Snchez‐Prez  S. Sauvage  P. Vervier  F. Giraud 《水文研究》2003,17(12):2375-2392

For 2 years, water flow‐patterns in the Garonne floodplain of south‐western France were studied in the field and through hydrodynamic modelling (MARTHE Hydrodynamic Software developed by BRGM). Water flow‐paths and the transport of dissolved elements between river and aquifer have been investigated and modelled. In order to quantify the buffer function of the alluvial floodplain, we focused our work on the effect of a major flood on the water flow‐direction, and on nitrate transport. Thus, we showed that the effect of a large flood in the river was rapidly lost with increasing distance from the river. During the observation period, a hydrologically active strip only 300 m wide on either side of the riverbed played a buffering role in absorbing the flood crest. It was also found that meanders favour the exchange between river and alluvial aquifer, shown by the creation of bypasses between the upstream and downstream parts of meanders. This, in turn, contributes to a dilution of nitrates in the phreatic aquifer, which here has higher nitrate content than the surface water; such dilution may result in an overestimation of the denitrification process in the wooded riverbanks. The coupling of chemical measurements—especially of chlorides and nitrate—with modelling of the dissolved‐element transport allows us to establish the water balance for the riparian wetland, and to separate the effect of dilution and denitrification on nitrate concentration. This indicated the existence of areas in the riparian wetlands where denitrification is particularly strong, leading to reductions in nitrate concentrations of 10 to 30 mg/l NO₃^? during the flood. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Nitrate loss and transformation in 2 vegetated headwater streams     

A. Bryce Cooper  James G. Cooke 《新西兰海洋与淡水研究杂志》2013,47(4):441-450

The processes of nitrate removal from the stream waters of 2 headwater catchments were studied. In study stretches where the stream channels were vegetated with thick mats of grass (Gly‐ceria fluitans), nitrate removal processes were particularly active. In such grassed stream channels, c. 75% of the nitrate removal was attributable to plant uptake and the remainder to denitrifica‐tion. Both of these nitrate removal processes were linearly dependent on nitrate concentration, resulting in an exponential decline of nitrate level from the springs along the stream's length. Regeneration of nitrogen, by plant decay within the stream channel, results in export of dissolved organic nitrogen and paniculate nitrogen from the catchments. The overall impact of vegetated stream channels in modifying nitrogen exports from catchments is discussed.  相似文献   

~(15)N示踪法测定海洋反硝化速率中~(29)N_2浓度的准确定量     

曾健  陈敏  郑敏芳  邱雨生 《海洋学报》2014,36(6):10-17

利用15 N示踪法实测南海水体反硝化速率的研究发现,培养水样在长时间密闭放置过程中也会受到外界空气的污染,且其29N2/28N2比值恒定为0.007 35。根据空气背景中29N2/28N2比值恒定的特征,提出基于质量平衡关系校正空气N2污染的方法,通过将样品实测29N2浓度扣除由外界空气贡献的29N2浓度,可获得由生物反硝化作用所产生的29N2准确浓度,进而可计算出准确的反硝化速率。经空气29N2背景校正后,29N2浓度的偏差明显小于未经校正的结果,且29N2浓度与培养时间之间的线性相关性显著加强,凸显出空气29N2背景校正是获取准确反硝化速率的关键。鉴于15 N示踪法已被广泛应用于海洋水体与沉积物反硝化速率的测定中,所提出的空气29N2背景校正方法具有重要的意义。  相似文献   

Geologic controls on the chemical behaviour of nitrate in riverside alluvial aquifers,Korea     

Joong‐Hyuk Min  Seong‐Taek Yun  Kangjoo Kim  Hyoung‐Soo Kim  Dong‐Ju Kim 《水文研究》2003,17(6):1197-1211

To investigate the origin and behaviour of nitrate in alluvial aquifers adjacent to Nakdong River, Korea, we chose two representative sites (Wolha and Yongdang) having similar land‐use characteristics but different geology. A total of 96 shallow groundwater samples were collected from irrigation and domestic wells tapping alluvial aquifers. About 63% of the samples analysed had nitrate concentrations that exceeded the Korean drinking water limit (44·3 mg l^?1 NO₃^?), and about 35% of the samples had nitrate concentrations that exceeded the Korean groundwater quality standard for agricultural use (88·6 mg l^?1 NO₃^?). Based on nitrogen isotope analysis, two major nitrate sources were identified: synthetic fertilizer (about 4‰ δ¹⁵N) applied to farmland, and animal manure and sewage (15–20‰ δ¹⁵N) originating from upstream residential areas. Shallow groundwater in the farmland generally had higher nitrate concentrations than those in residential areas, due to the influence of synthetic fertilizer. Nitrate concentrations at both study sites were highest near the water table and then progressively decreased with depth. Nitrate concentrations are also closely related to the geologic characteristics of the aquifer. In Yongdang, denitrification is important in regulating nitrate chemistry because of the availability of organic carbon from a silt layer (about 20 m thick) below a thin, sandy surface aquifer. In Wolha, however, conservative mixing between farmland‐recharged water and water coming from a village is suggested as the dominant process. Mixing ratios estimated based on the nitrate concentrations and the δ¹⁵N values indicate that water originating from the village affects the nitrate chemistry of the shallow groundwater underneath the farmland to a large extent. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

亚硝酸根作为电子受体的反硝化吸磷特性   总被引：1，自引：0，他引：1  

李相昆  周业剑  高美玲  王立军  焦中志  黄荣新  刘冬峰 《吉林大学学报(地球科学版)》2008,38(1):117-120

为了考察聚磷污泥以NO2-为电子受体的反硝化吸磷特性,通过静态烧杯试验,研究了不同NO2-浓度聚磷污泥的反硝化同时吸磷能力及动力学。实验结果表明:NO2-质量浓度在31.25 mg/L以下时,反硝化聚磷菌可以利用NO2-为电子受体完成反硝化吸磷;在高于37.50 mg/L时,NO2-对缺氧吸磷有明显的抑制作用。但是反硝化聚磷菌经过驯化之后,即使NO2-质量浓度达到很高(75.00 mg/L),仍然可以利用NO2-作为电子受体完成反硝化吸磷,而没有发现抑制吸磷的现象,而且NO2-的浓度对吸磷速率没有明显影响。以NO2-为电子受体平均吸磷速率为3.16 mg P/(gMLVSS.h),平均反硝化速率为5.14mg NO2--N/(gMLVSS.h),吸磷速率小于以氧和NO3-为电子受体时的速率。  相似文献   

反硝化菌的耐砷驯化及其对水铁矿吸附态砷迁移转化的影响   总被引：2，自引：0，他引：2  

郭华明  陈思  任燕 《地学前缘》2008,15(5):317

采集缺氧活性污泥进行室内微生物驯化,培养耐砷反硝化菌。把耐砷反硝化菌、营养液和吸附As(V)的水铁矿在厌氧条件下培养,研究反硝化菌代谢作用下,系统中Fe、Mn、NO3-和As形态的动态变化。结果表明,缺氧活性污泥中的反硝化菌具有一定的耐砷能力。在砷含量500μg/L以内,其反硝化强度基本不受砷的影响。在吸附有砷的水铁矿体系中,反硝化菌所产生的反硝化作用可导致溶液中NO3-含量的降低、Fe含量的升高、As含量降低,且As(III)所占比例增加。这说明,体系中水铁矿的还原性溶解和As(V)的还原性解吸已经发生。As含量降低的原因是,在培养体系中水铁矿的含量高,Fe的释放量只占很小比例,表层水铁矿被还原后,在次表层形成新的水铁矿吸附位,这种新吸附位不仅可以吸附溶液中已经存在的As,而且能够再吸附由于还原性溶解和解吸所释放出的As。  相似文献   

Observations of nitric acid perturbations in the winter Arctic stratosphere: Evidence for PSC sedimentation     

Frank Arnold  Veit Bürger  Klaus Gollinger  Michael Roncossek  Johannes Schneider  Stefan Spreng 《Journal of Atmospheric Chemistry》1998,30(1):49-59

Gaseous nitric acid (HNO3) and hydrogene fluoride (HF) have been measured in the winter Arctic stratosphere using balloon- and aircraft-based Ion Molecule Reaction Mass Spectrometry (IMRMS) instruments. Strong HNO3 perturbations were found in 1993 and 1995 which may indicate nitrification around 11-13 km and denitrification around 20 km altitude. Most likely these perturbations were caused by sedimentation of HNO3 containing aerosols followed by aerosol evaporation at lower altitudes.  相似文献   

N₂O Production, Nitrification and Denitrification in an Estuarine Sediment   总被引：1，自引：0，他引：1  

T. Usui  I. Koike  N. Ogura 《Estuarine, Coastal and Shelf Science》2001,52(6):769

The mechanisms regulating N₂O production in an estuarine sediment (Tama Estuary, Japan) were studied by comparing the change in N₂O production with those in nitrification and denitrification using an experimental continuous-flow sediment–water system with¹⁵N tracer (¹⁵N-NO−3 addition). From Feburary to May, both nitrification and denitrification in the sediment increased (246 to 716 μmol N m⁻² h⁻¹and 214 to 1260 μmol N m⁻² h⁻¹, respectively), while benthic N₂O evolution decreased slightly (1560 to 1250 nmol N m⁻² h⁻¹). Apparent diffusion coefficients of inorganic nitrogen compounds and O₂at the sediment–water interface, calculated from the respective concentration gradients and benthic fluxes, were close to the molecular diffusion coefficients (0·68–2·0 times) in February. However, they increased to 8·8–52 times in May except for that of NO−2, suggesting that the enhanced NO−3 and O₂supply from the overlying water by benthic irrigation likely stimulated nitrification and denitrification. Since the progress of anoxic condition by the rise of temperature from February to May (9 to 16 °C) presumably accelerated N₂O production through nitrification, the observed decrease in sedimentary N₂O production seems to be attributed to the decrease in N₂O production/occurrence of its consumption by denitrification. In addition to the activities of both nitrification and denitrification, the change in N₂O metabolism during denitrification by the balance between total demand of the electron acceptor and supply of NO−3+NO−2 can be an important factor regulating N₂O production in nearshore sediments.  相似文献   

The nitrogen cycle of an East Coast, U.K. saltmarsh: II. Nitrogen fixation, nitrification, denitrification, tidal exchange     

S. Azni b Abd. Aziz  D. B. Nedwell 《Estuarine, Coastal and Shelf Science》1986,22(6)

Measurements of nitrogen fixation (acetylene reduction) showed greatest rates in the saltmarsh pans with a benthic layer of cyanobacteria present. The smallest amount of nitrogen fixation occurred on the marsh surface where a Puccinellia maritima/Halimione portulacoides plant association shaded the underlying sediment. Phototrophic nitrogen fixation was always greater than dark, chemotrophic, bacterial fixation.Only a small proportion of the total amount of ammonium, which was formed during detrital breakdown, was nitrified to nitrate. Although there is a high capacity for bacterial nitrate reduction in these sediments, the process is limited by low nitrate availability and most nitrate upon reduction is converted to ammonium rather than being denitrified to gaseous products. Denitrification does not, therefore, result in any great loss of nitrogen from the saltmarsh.There was little net import or export of nitrogen on an annual basis, although nitrate and organic-N in small particulate material was removed from tidal water by the marsh, and there was net annual export of ammonium, dissolved organic-N and organic-N in large particulate material. Losses of nitrogen by the small net tidal export and by denitrification were approximately balanced by nitrogen fixation. It was concluded that the nitrogen cycle of the Colne Point saltmarsh was balanced on an annual basis, with most nitrogen being recycled within the marsh. The saltmarsh did not apparently act as a net source of nitrogen for the adjacent estuary, although it may act as an important processor of nitrogen, removing some forms of nitrogen such as nitrate from tidal water while exporting other forms of nitrogen such as dissolved organic-N.  相似文献   

Nitrite-induced enhancement of toxicity of phenanthrene in fish and its implications for coastal waters     

M. S. Shailaja  A. Rodrigues 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1107-1110

Coastal areas are prone to varying degrees of anthropogenic chemical contamination. In many coastal environments experiencing reducing conditions in the water column, nitrite is produced as a result of denitrification. With a view to determining the effect of a natural stress such as the presence of nitrite in water on the xenobiotic metabolism in fish, the euryhaline cichlid Oreochromis mossambicus was exposed for up to 9 days to environmentally relevant concentrations of water-borne nitrite and phenanthrene, a polycyclic aromatic hydrocarbon.Analyses of different biomarkers in the treated fish indicated significant increase in the metabolism of phenanthrene as a result of exposure to nitrite. For example, the activity of the biotransformation enzyme measured as 7-ethoxyresorufin-O-deethylase activity was, in the presence of 1 μM nitrite, nearly twice that produced by phenanthrene alone. Similarly, biliary fixed fluorescence values reflecting phenanthrene and its metabolites were rendered 1.7 times higher when exposed simultaneously to nitrite. Contact with nitrite and phenanthrene together also led to severe hepatic damage with possible cell death as inferred from the large enhancement in sorbitol dehydrogenase activity in the serum and reduced liver somatic index.  相似文献