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1.
In many agricultural areas, hedgerows give rise to strong expectations of reducing the inputs of excess nitrate to the groundwater and rivers. This study aims to analyse the spatial and seasonal influences of a hedgerow on nitrate dynamics in the soil and groundwater. Nitrate (NO3?) and chloride (Cl?) concentrations were measured with spatially dense sampling in the unsaturated soil and in the groundwater along a transect intersecting a bottomland oak (Quercus rubor) hedgerow after the growing season and during the dormant season. We explain NO3? dynamics by using Cl? as an index of tree‐root extension and water transfer. At the end of the growing season, NO3? is entirely absorbed by the trees over a large and deep volume corresponding to the rooting zone, where, in contrast Cl? is highly concentrated due to root exclusion. However, these observed patterns in the soil have no influence on the deep groundwater composition at this season. During the dormant season, water transfer processes feeding the shallow groundwater layer are different upslope and downslope from the hedgerow in relation to the thickness of the unsaturated zone. Upslope, the shallow groundwater is fed by rainwater infiltration through the soil which favours Cl? dilution. Right under the hedge and downslope, the rapid ascent of the groundwater near the ground surface prevents rainwater input and Cl? dilution. Under the hedgerow the highest concentrations of Cl? coincide with the absence of NO3? in the shallow groundwater layer and with high concentrations of dissolved organic carbon. The absence of NO3? during the dormant season seems to be due to denitrification in the hedgerow rooting zone when it is rapidly saturated by groundwater. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
Four years of detailed ground-water monitoring at a newly installed, seasonal-use, domestic septic system located on poorly buffered (CaCO3 equivalent content ≤ 1.6 wt.%) lacustrine silt, has revealed the development of an acidic ground-water plume. Acid, generated by the partial oxidation of effluent NH4+ dissolved organic carbon (DOC), and possibly sulfide minerals present in the sediment, has resulted in a distal plume core zone with pH values in the range of 4.4 to 5.0. The acidic zone, where NH4+ does, however, persist (> 2 mg/1, as N) and where DOC remains elevated (6–13 mg/1), is associated with high average concentrations of the trace metals Fe (4.7 mg/1), Al (1.9 mg/1), and Mn (3.6 mg/1). Attenuation of nitrogen along the plume core flowpath is indicated by a decrease in the N/ Cl− ratio from an effluent value of 1.7, to a plume value of only 0.5 after 4 m of subsurface flow. Increased SO42− levels observed in the zone of N depletion suggest that attenuation can be at least partly attributed to reduction of plume NO3− by oxidation of reduced S present in the sediment. PO43− has not migrated significantly beyond the infiltration bed gravel layer, demonstrating that PO43− mobility is limited in these sediments (retardation factor > 10). 相似文献
3.
The sources and storage of soil NO3− in the western Tengger Desert, Northwest China, were explored using water chemistry analysis and stable isotope techniques. In line with the expansion and development of oases, part of the desert has been transformed into cultivated land and artificial forest land. The mean soil NO3− contents found in areas of cultivated land and artificial forest were 123.06 mg kg−1 and 1.26 mg kg−1, far higher and slightly lower than the background desert soil values, respectively. The δ15N-NO3− and δ18O-NO3− values in cultivated soils ranged from 1.00 to 11.81 ‰, and from −1.85 to 8.99 ‰, respectively, and the mean mNO3−/Cl− value in cultivated soils was 2.3. These figures would appear to demonstrate that the rapid increase in the nitrate content in soils is principally due to the use of nitrogen fertilizer. Such increases in soil NO3− storage is likely to promote the leaching of nitrogen into the groundwater where coarsely textured soils exist, the pollution of water sources used for irrigation water, and extreme precipitation events. The δ15N-NO3− and δ18O-NO3− values in groundwater ranged from 3.72 to 6.54 ‰, and from −0.19 to 12.06 ‰, respectively, mainly reflecting the nitrification of soil nitrogen. These values appeared similar to those measured in the soil water in adjacent areas of cultivated land and vegetated desert, indicating that the groundwater has been affected by both natural and artificial NO3−. Artificial afforestation of desert regions would therefore seem to be a useful way of reducing the threat posed by anthropogenic sources to the circulation of NO3−-N within arid regions, as well as promoting wind sheltering and sand fixation. This study explored the NO3− storage and groundwater quality responses to oasis development in arid areas in an attempt to provide effective information for local agricultural organizations and agricultural nitrogen management models. 相似文献
4.
Spatial patterns of N dynamics in soil were evaluated within two small forested watersheds in Japan. These two watersheds were characterized by steep slopes (>30°) and high stream NO−3 drainage rates (8·4 to 25·1 kg N ha−1 yr−1) that were greater than bulk precipitation N input rates (7·5 to 13·5 kg N ha−1 yr−1). Higher rates of nitrification potential at near-stream zones were reflected in greater NO−3 contents for soil at the near-stream zones compared with ridge zones. Both stream discharge rates and NO−3 concentrations in deep unsaturated soil at the near-stream zones were positively correlated to NO−3 concentrations in stream water. These relationships, together with high soil NO−3 contents at the near-stream zones, suggest that the near-stream zone was an important source of NO−3 to stream water. Nitrate flux from these near-stream zones was also related to the drainage of cations (K+, Ca2+ and Mg2+). The steep slope of the watersheds resulted in small saturated areas that contributed to the high NO−3 production (high nitrification rates) in the near-stream zone. © 1998 John Wiley & Sons, Ltd. 相似文献
5.
Xueru Guo Rui Zuo Jinsheng Wang Li Meng Yanguo Teng Rongtao Shi Xiang Gao Fei Ding 《Ground water》2019,57(3):430-442
Hydrogeochemical evolution of interactions between surface water and groundwater is crucial for guaranteeing water supply quality in a riverside water source area. This study focuses on the seasonal and spatial characteristics of hydrogeochemical evolution affected by groundwater exploitation in the Hulan water source area using hydrochemical analyses and stable isotope tracers. Results show that the concentrations of major ions and total dissolved solids (TDS) increase considerably during the dry season. A bicarbonate water type is primarily produced by the dissolution of calcite, dolomite and gypsum, as well as the cation exchange and human activities. Along the typical infiltration path, the proportions of surface water increase with proximity to the river from 8%-63% during the wet season to 11%-84% during the dry season, which are attributed to an increased hydraulic gradient by exploitation. The typical path is classified into two zones. The first is the intensive mixing zone (within 1 km) with increasing concentrations of major ions and TDS due to mixing effect. The second is the exploitation influence zone (1-3.3 km) with increased concentrations of Ca2+, Mg2+, SO42−, and HCO3− during the dry season due to two reasons of seasonal variations in evaporation, stronger water-rock interactions and mixing effects with increased surface water by exploitation. 相似文献
6.
The spatial and temporal distribution of sulphate (SO4) concentrations in peat pore water and the outlet streams of two forested swamps was related to variations in the magnitude of upland runoff, wetland water levels and flow path. The swamps were located in headwater catchments with contrasting till depths typical of the southern Canadian Shield. Inputs of SO4 from shallow hillslope tills and streams showed little seasonal variation in either source or concentration in both swamps. Sulphate dynamics at the outlet stream reflected hydrological and biogeochemical processes within the valley wetlands, which in turn were partly controlled by catchment hydrogeology. During high runoff, maximum water table elevations and peak surface flow in the swamps resulted in upland inputs largely bypassing anoxic peat. Consequently, SO4 concentrations of 8–10 mg/l at the swamp outlets were similar to stream and groundwater inputs. During periods of low flow, concentrations of SO4 at the swamp outlets declined to less than 3 mg/l. At this time lower water table elevations resulted in increased interaction of input water with anoxic peats, and therefore, SO4 reduction. Contrasts in till depth and the nature of groundwater flow between catchments resulted in differences in SO4 dynamics between years and swamps. In dry summers the absence of groundwater inputs to the swamp in the catchment with thin till resulted in a large water table drawdown and re-oxidation of accumulated S, which contributed to maximum SO4 concentrations (up to 35 mg/l) during storm runoff. Continuous groundwater input to the swamp in the catchment with deeper till was critical to maintaining saturated surfaces and efficient SO4 retention during both dry and wet summers. A conceptual model of wetland SO4 retention and export, based on catchment hydrogeology, is developed to generalize the SO4 dynamics of valley bottom wetlands at the landscape scale. © 1997 by John Wiley & Sons, Ltd. 相似文献
7.
The source and hydrochemical makeup of a stream reflects the connectivity between rainfall, groundwater, the stream, and is reflected to water quantity and quality of the catchment. However, in a semi-arid, thick, loess covered catchment, temporal variation of stream source and event associated behaviours are lesser known. Thus, the isotopic and chemical hydrographs in a widely distributed, deep loess, semi-arid catchment of the northern Chinese Loess Plateau were characterized to determine the source and hydrochemical behaviours of the stream during intra-rainfall events. Rainfall and streamflow were sampled during six hydrologic events coupled with measurements of stream baseflow and groundwater. The deuterium isotope (2H), major ions (Cl−, SO42−, NO3−, Ca2+, K+, Mg2+, and Na+) were evaluated in water samples obtained during rainfall events. Temporal variation of 2H and Cl− measured in the groundwater and stream baseflow prior to rainfall was similar; however, the isotope compositions of the streamflow fluctuated significantly and responded quickly to rainfall events, likely due to an infiltration excess, overland dominated surface runoff during torrential rainfall events. Time source separation using 2H demonstrated greater than 72% on average, the stream composition was event water during torrential rainfall events, with the proportion increasing with rainfall intensity. Solutes concentrations in the stream had loglinear relationships with stream discharge, with an outling anomaly with an example of an intra-rainfall event on Oct. 24, 2015. Stream Cl− behaved nonconservative during rainfall events, temporal variation of Cl− indicated a flush and washout at the onset of small rainfall events, a dilution but still high concentration pattern in high discharge and old water dominated in regression flow period. This study indicates rainfall intensity affects runoff responses in a semi-arid catchment, and the stored water in the thick, loess covered areas was less connected with stream runoff. Solute transport may threaten water quality in the area, requiring further analysis of the performance of the eco-restoration project. 相似文献
8.
为揭示太湖流域降雨和湖水酸根阴离子长期变化特征及环境意义,通过历史数据收集和采样分析,对太湖流域降雨和湖水中的SO42-、NO3-变化特征和来源进行了研究.结果表明：自1990s以来太湖流域降雨中SO42-呈显著下降趋势,年平均下降率为0.28 mg/（L·a）;NO3-浓度却呈显著上升趋势,年平均增长率为0.05 mg/（L·a）,降雨中氮污染呈现加重的趋势.与之相反,湖水中SO42-呈显著上升趋势,年平均增长率为1.24 mg/（L·a）;NO3-浓度却呈显著下降趋势,年平均下降率为0.02 mg/（L·a）.30年以来,太湖水体SO42-/NO3-比值不断升高,远高于降水SO42-/NO3-比值.研究认为：流域SO2排放引起的酸沉降是湖水SO42-浓度增长的最重要原因,但氮氧化物排放并未引起湖水NO3-浓度升高,说明太湖流域对大气沉降的氮氧化物有滞留作用,而太湖水体是流域大气沉降硫酸盐的重要汇.综合治理太湖流域酸性物质排放对防止太湖水体酸化和治理富营养化都具有重要意义. 相似文献
9.
The anion compositions (SO24, HCO−3 and Cl−) of runoff from the Haut Glacier d'Arolla, Switzerland and Austre Brøggerbreen, Svalbard are compared to assess whether or not variations in water chemistry with discharge are consistent with current understanding of the subglacial drainage structure of warm- and polythermal-based glaciers. These glacial catchments have very different bedrocks and the subglacial drainage structures are also believed to be different, yet the range of anion concentrations show considerable overlap for SO2−4 and HCO−3. Concentrations of Cl− are higher at Austre Brøggerbreen because of the maritime location of the glacier. Correcting SO2−4 for the snowpack component reveals that the variation in non-snowpack SO2−4 with discharge and with HCO−3 is similar to that observed at the Haut Glacier d'Arolla. Hence, if we assume that the provenance of the non-snowpack SO2−4 is the same in both glacial drainage systems, a distributed drainage system also contributes to runoff at Austre Brøggerbreen. We have no independent means of testing the assumption at present. The lower concentrations of non-snowpack SO2−4 at Austre Brøggerbreen may suggest that a smaller proportion of runoff originates from a distributed drainage system than at the Haut Glacier d'Arolla. 相似文献
10.
The persistence of inorganic nitrogen is assessed in a set of 21 septic system plumes located in Ontario, Canada, that were studied over a 31-year period from 1988 to 2019. In the plume zones underlying the drainfields, site mean NO3− values averaged 34 ± 27 mg N/L and exceeded the nitrate drinking water limit (DWL) of 10 mg N/L at 16 of 21 sites. In plume zones extending up to 30 m downgradient from the drainfields, site mean NO3− values averaged 24 ± 20 mg N/L and exceeded the DWL at 9 of 13 sites. Site mean total inorganic nitrogen (TIN; NH4+ + NO3− − N) removal averaged 34 ± 26% in the drainfield zones and 36 ± 44% in the downgradient plume zones, indicating that much of the removal occurred within the drainfields. Removal was much higher at nine sites where drainfield TIN included >10% NH4+ (62 ± 25% removal). TIN removal was not correlated with wastewater loading rate, system age, or sediment carbonate mineral content, but was correlated with water table depth, where shallower water table sites had generally less complete wastewater oxidation. At many of these sites, both NO3− and NH4+ were present together in the plumes and were lost concomitantly, suggesting that the anammox reaction was making an important contribution to the observed TIN loss. When groundwater nitrate contamination is a concern, considering on-site treatment system designs that lead to a lesser degree of wastewater oxidation, could be a useful approach for enhancing N removal. 相似文献
11.
The Jiangcang Basin is an important mining area of the former Qilian Mountain large coal base in Qinghai Province, and understanding the groundwater circulation mechanism is the basis for studying the hydrological effects of permafrost degradation in alpine regions. In this study, hydrogeochemical and multiple isotope tracer analysis methods are used to understand the chemical evolution and circulation mechanisms of the groundwater in the typical alpine region of the Jiangcang Basin. The diversity of the groundwater hydrochemistry in the study area reflects the complexity of the hydrogeochemical environment in which it is located. The suprapermafrost water and intrapermafrost water are recharged by modern meteoric water. The groundwater is closely hydraulically connected to the surface water with weak evaporation overall. The high δ34S value of deep groundwater is due to SO4 reduction, and SO42−-rich snow recharge with lixiviated sulfate minerals are the main controlling factor for the high SO42− concentration in groundwater. According to the multivariate water conversion relationships, it reveals that the river receives more groundwater recharge, suprapermafrost water is recharged by the proportion of meteoric water, which is closely related to the mountainous area at the edge of the basin, while intrapermafrost water is mainly recharged by the shallow groundwater. This study provides a data-driven approach to understanding groundwater recharge and evolution in alpine regions, in addition to having significant implications for water resource management and ecological environmental protection in coal bases of the Tibetan Plateau. 相似文献
12.
M. TRANTER M. J. SHARP G. H. BROWN I. C. WILLIS B. P. HUBBARD M. K. NIELSEN C. C. SMART S. GORDON M. TULLEY H. R. LAMB 《水文研究》1997,11(1):59-77
Meltwaters collected from boreholes drilled to the base of the Haut Glacier d'Arolla, Switzerland have chemical compositions that can be classified into three main groups. The first group is dilute, whereas the second group is similar to, though generally less concentrated in major ions, than contemporaneous bulk glacial runoff. The third group is more concentrated than any observed bulk runoff, including periods of flow recession. Waters of the first group are believed to represent supraglacial meltwater and ice melted during drilling. Limited solutes may be derived from interactions with debris in the borehole. The spatial pattern of borehole water levels and borehole water column stratification, combined with the chemical composition of the different groups, suggest that the second group represent samples of subglacial waters that exchange with channel water on a diurnal basis, and that the third group represent samples of water draining through a ‘distributed’ subglacial hydraulic system. High NO−3 concentrations in the third group suggest that snowmelt may provide a significant proportion of the waters and that the residence time of the waters at the bed in this particular section of the distributed system is of the order of a few months. The high NO−3 concentrations also suggest that some snowmelt is routed along different subglacial flowpaths to those used by icemelt. The average SO2−4: (HCO−3 + SO2−4) ratio of the third group of meltwaters is 0.3, suggesting that sulphide oxidation and carbonate dissolution (which gives rise to a ratio of 0.5) cannot provide all the HCO−3 to solution. Hence, carbonate hydrolysis may be occurring before sulphide oxidation, or there may be subglacial sources of CO2, perhaps arising from microbial oxidation of organic C in bedrock, air bubbles in glacier ice or pockets of air trapped in subglacial cavities. The channel marginal zone is identified as an area that may influence the composition of bulk meltwater during periods of recession flow and low diurnal discharge regimes. © 1997 by John Wiley & Sons, Ltd. 相似文献
13.
Intensive water sampling in conjunction with hydrological observations was conducted during three different rainstorms in order to understand the effects of rainfall events on the temporal variation of streamwater chemistry in a small headwater forest catchment. Concentrations of Na+ and SO42? decreased as the discharge rate increased. Hydrograph separation of the components was made using the three‐component model based on the end‐members mixing analysis (EMMA). The three end‐members were:
- 1 the groundwater in the saturated zone that prescribes the chemistry of the baseflow;
- 2 the throughfall that dilutes the streamwater;
- 3 the groundwater in the transient saturated zone prescribed, which was dependent on the groundwater level.
14.
Diffusive equilibrium in thin films provides evidence of suppression of hyporheic exchange and large‐scale nitrate transformation in a groundwater‐fed river 
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下载免费PDF全文 P. Byrne H. Zhang S. Ullah A. Binley A.L. Heathwaite C.M. Heppell K. Lansdown M. Trimmer 《水文研究》2015,29(6):1385-1396
The hyporheic zone of riverbed sediments has the potential to attenuate nitrate from upwelling, polluted groundwater. However, the coarse‐scale (5–10 cm) measurement of nitrogen biogeochemistry in the hyporheic zone can often mask fine‐scale (<1 cm) biogeochemical patterns, especially in near‐surface sediments, leading to incomplete or inaccurate representation of the capacity of the hyporheic zone to transform upwelling NO3?. In this study, we utilised diffusive equilibrium in thin‐films samplers to capture high resolution (cm‐scale) vertical concentration profiles of NO3?, SO42?, Fe and Mn in the upper 15 cm of armoured and permeable riverbed sediments. The goal was to test whether nitrate attenuation was occurring in a sub‐reach characterised by strong vertical (upwelling) water fluxes. The vertical concentration profiles obtained from diffusive equilibrium in thin‐films samplers indicate considerable cm‐scale variability in NO3? (4.4 ± 2.9 mg N/L), SO42? (9.9 ± 3.1 mg/l) and dissolved Fe (1.6 ± 2.1 mg/l) and Mn (0.2 ± 0.2 mg/l). However, the overall trend suggests the absence of substantial net chemical transformations and surface‐subsurface water mixing in the shallow sediments of our sub‐reach under baseflow conditions. The significance of this is that upwelling NO3?‐rich groundwater does not appear to be attenuated in the riverbed sediments at <15 cm depth as might occur where hyporheic exchange flows deliver organic matter to the sediments for metabolic processes. It would appear that the chemical patterns observed in the shallow sediments of our sub‐reach are not controlled exclusively by redox processes and/or hyporheic exchange flows. Deeper‐seated groundwater fluxes and hydro‐stratigraphy may be additional important drivers of chemical patterns in the shallow sediments of our study sub‐reach. © 2015 The Authors. Hydrological Processes Published by John Wiley & Sons Ltd. 相似文献
15.
Stable isotopic and geochemical identification of groundwater evolution and recharge sources in the arid Shule River Basin of Northwestern China 总被引：5，自引：0，他引：5 下载免费PDF全文
下载免费PDF全文 Xiaoyan Guo Qi Feng Wei Liu Zongxing Li Xiaohu Wen Jianhua Si Haiyang Xi Rui Guo Bing Jia 《水文研究》2015,29(22):4703-4718
Stable isotopic (δDVSMOW and δ18OVSMOW) and geochemical signatures were employed to constrain the geochemical evolution and sources of groundwater recharge in the arid Shule River Basin, Northwestern China, where extensive groundwater extraction occurs for agricultural and domestic supply. Springs in the mountain front of the Qilian Mountains, the Yumen‐Tashi groundwater (YTG), and the Guazhou groundwater (GZG) were Ca‐HCO3, Ca‐Mg‐HCO3‐SO4 and Na‐Mg‐SO4‐Cl type waters, respectively. Total dissolved solids (TDS) and major ion (Mg2+, Na+, Ca2+, K+, SO42?, Cl? and NO3?) concentrations of groundwater gradually increase from the mountain front to the lower reaches of the Guazhou Basin. Geochemical evolution in groundwater was possibly due to a combination of mineral dissolution, mixing processes and evapotranspiration along groundwater flow paths. The isotopic and geochemical variations in melt water, springs, river water, YTG and GZG, together with the end‐member mixing analysis (EMMA) indicate that the springs in the mountain front mainly originate from precipitation, the infiltration of melt water and river in the upper reaches; the lateral groundwater from the mountain front and river water in the middle reaches are probably effective recharge sources for the YTG, while contribution of precipitation to YTG is extremely limited; the GZG is mainly recharged by lateral groundwater flow from the Yumen‐Tashi Basin and irrigation return flow. The general characteristics of groundwater in the Shule River Basin have been initially identified, and the results should facilitate integrated management of groundwater and surface water resources in the study area. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
Yin Long Tianming Huang Fen Zhang Zhenbin Li Baoqiang Ma Yiman Li Zhonghe Pang 《水文研究》2021,35(4):e14166
The use of the sulphate mass balance (SMB) between precipitation and soil water as a supplementary method to estimate the diffuse recharge rate assumes that the sulphate in soil water originated entirely from atmospheric deposition; however, the origin of sulphate in soil and groundwater is often unclear, especially in loess aquifers. This study analysed the sulphur (δ34S-SO4) and oxygen (δ18O-SO4) isotopes of sulphate in precipitation, water-extractable soil water, and shallow groundwater samples and used these data along with hydrochemical data to determine the sources of sulphate in the thick unsaturated zone and groundwater of a loess aquifer. The results suggest that sulphate in groundwater mainly originated from old precipitation. When precipitation percolates through the unsaturated zone to recharge groundwater, sulphates were rarely dissolved due to the formation of CaCO3 film on the surface of sulphate minerals. The water-extractable sulphate in the deep unsaturated zone (>10 m) was mainly derived from the dissolution of evaporite minerals and there was no oxidation of sulphide minerals during the extraction of soil water by elutriating soil samples with deionized water. The water-extractable concentration of SO4 was not representative of the actual SO4 concentration in mobile soil water. Therefore, the recharge rate cannot be estimated by the SMB method using the water-extractable concentration of SO4 in the loess areas. This study is important for identifying sulphate sources and clarifying the proper method for estimating the recharge rate in loess aquifers. 相似文献
17.
Hydrogeological and hydrogeochemical control of groundwater salinity in an arid inland basin: Dunhuang Basin,northwestern China 总被引：2，自引：0，他引：2 下载免费PDF全文
下载免费PDF全文 High groundwater salinity has become a major concern in the arid alluvial plain of the Dunhuang Basin in northwestern China because it poses a significant challenge to water resource management. Isotopic and geochemical analyses were conducted on 55 water samples from springs, boreholes and surface water to identify potential sources of groundwater salinity and analyse the processes that control increasing salinity. The total dissolved solid (TDS) content in the groundwater ranged from 400 to 41 000 mg/l, and high TDS values were commonly associated with shallow water tables and flow‐through and discharge zones in unconfined aquifers. Various groundwater contributions from rainwater, agricultural irrigation, river water infiltration and lateral inflows from mountains were identified by major ions and δD and δ18O. In general, HCO3? and SO42? were the dominant anions in groundwater with a salinity of <2500 mg/l, whereas Cl? and SO42? were the dominant anions in groundwater with a salinity of >2500 mg/l. The major ion concentrations indicated that mineral weathering, including carbonate and evaporite dissolution, primarily affected groundwater salinity in recharge areas. Evapotranspiration controlled the major ion concentration evolution and salinity distribution in the unconfined groundwaters in the flow‐through and discharge areas, although it had a limited effect on groundwater in the recharge areas and confined aquifers. Agricultural irrigation increased the water table and enhanced evapotranspiration in the oasis areas of the basin. TDS and Cl became more concentrated, but H and O isotopes were not enriched in the irrigation district, indicating that transpiration dominated the increasing salinity. For other places in the basin, as indicated by TDS, Cl, δD and δ18O characteristics, evaporation, transpiration and water–rock interactions dominated at different hydrogeological zones, depending on the plant coverage and hydrogeological conditions. Groundwater ages of 3H, and δD and δ18O compositions and distributions suggest that most of the groundwaters in Dunhuang Basin have a paleometeoric origin and experienced a long residence time. These results can contribute to groundwater management and future water allocation programmes in the Dunhuang Basin. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
Slimane Merouani Aissa Dehane Aouattef Belghit Oualid Hamdaoui Yasser A. Tobba Chouaib Lahlou Maulin P. Shah 《洁净——土壤、空气、水》2023,51(3):2100304
This research aims at optimizing the effects of processing conditions, salts, natural organic materials, and water matrices quality on the effectiveness of the Fe(II)/K2S2O8/hydroxylamine process in the degradation of pararosaniline. Assisting the Fe(II)/KPS (potassium persulfate) treatment with protonated hydroxylamine (H3NOH+) increases the degradation rate of pararosaniline by more than 100%. Radical scavenger experiments show that the SO4●− radical dominates pararosaniline degradation in the Fe(II)/KPS system, whereas ●OH is the dominant reactive species in the presence of H3NOH+. The disparity in pararosaniline removal effectiveness upon the Fe(II)/KPS/H3NOH+ and Fe(II)/KPS systems gets more significant with increasing reactants doses (i.e., H3NOH+, H2O2, Fe(II)) and solution pH (2–7). Interestingly, H3NOH+ increased the working pH to 6 instead of pH 4 for the Fe(II)/KPS process. Moreover, mineral anions such as Cl−, NO3−, NO2−, and SO4− (up to 10 × 10−3 m ) do not affect the efficiency of the Fe(II)/KPS/H3NOH+ process. In contrast, acid humic decreases the performance of the process by ≈20%. In natural mineral water, treated wastewater, and river water samples, the Fe(II)/KPS/H3NOH+ process maintains higher degradation performance (≈95%), whereas the process efficiency is greatly amortized in seawater. The efficiency of the Fe(II)/KPS process was drastically decreased in the various water matrices. 相似文献
19.
Isotopic and hydrochemistry spatial variation of sulfate for groundwater characterization in karstic aquifers 下载免费PDF全文
下载免费PDF全文 Antonio González‐Ramón Manuel López‐Chicano Fernando Gázquez Juan José Durán‐Valsero Antonio Pedrera Ana Ruiz‐Constán Elena González‐Egea 《水文研究》2017,31(18):3242-3254
The Sierra Gorda aquifer is one of the most extensive of southern Spain. The main groundwater discharge is produced at its northern boundary through several high‐flow springs. In this study, stable isotopes of dissolved sulfate (δ34S and δ18O) and groundwater chemistry were used to determine the origin of the sulfate and to characterize the groundwater flow. We sampled the main springs, as well as other minor outlets related to perched water tables, in order to determine the different sources of SO42? (e.g., dissolution of evaporites and atmospheric deposition). The substantial difference in the amount of dissolved SO42? between the springs located in its northwestern part (≈25 mg/L) and those elsewhere in the northern part (≈60 mg/L) suggests zones with separate groundwater flow systems. A third group of springs, far from the northeastern boundary of the permeable outcrops, shows higher SO42? content than the rest (≈125 mg/L). The isotopic range of sulfate (?0.3‰ to 14.82‰ V‐CTD) points to several sources, including dissolution of Triassic or Miocene evaporites, atmospheric deposition, and decomposition of organic material in the soil. Among these, the dissolution of Triassic gypsum—which overlies the saturated zone as a consequence of the folds and faults that deform the aquifer—is the main source of SO42? (range from 12.79‰ to 14.82‰ V‐CTD). This range is typical for Triassic gypsum. The higher karstification in the western sector, together with important differences in the saturated thickness between the western and eastern sectors, would also be due to the tectonic structure and could explain the difference in SO42? contents in the water. This singular arrangement may cause a higher residence time of groundwater in the eastern sector; thus, a higher contact time with Triassic evaporitic rocks is inferred. Accordingly, the stable isotopes of SO42? are found to be a valuable tool for identifying areas with different flow systems in the saturated zone of karstic aquifers, as well as for evaluating aspects such as the degree of karstification . 相似文献
20.
Materials of long-term studies of the concentration and distribution of N forms (NH4+, NO3−, NO2−, Norg) in precipitation, surface water and groundwater are generalized. Precipitation was found to be the main source of N compounds
input into these waters. The effect of anthropogenic factors is local and does not influence the concentration and distribution
of N forms in most water bodies that serve as wastewater recipients. The N forms dominating in precipitation are NO3− and N H4+; Norg dominates in most surface water bodies, and NO3− dominates in groundwater. The median concentrations of Ntot in clear surface and subsurface waters are similar. The obtained characteristics of the concentrations and distribution of
N forms in natural waters of Karelia can be used for other water bodies in the humid zone. 相似文献