Fluxes of inorganic carbon from two forested catchments in the Appalachian mountains     

Fred Worrall  Wayne T. Swank  Tim Burt 《水文研究》2005,19(15):3021-3035

This study uses long‐term records of stream chemistry, discharge and air temperature from two neighbouring forested catchments in the southern Appalachians in order to calculate production of dissolved CO₂ and dissolved inorganic carbon (DIC). One of the pair of catchments was clear‐felled during the period of the study. The study shows that: (1) areal production rates of both dissolved CO₂ and DIC are similar between the two catchments even during and immediately after the period of clear‐felling; (2) flux of total inorganic carbon (dissolved CO₂+ DIC) rises dramatically in response to a catchment‐wide acidification event; (3) DIC and dissolved CO₂ are dominantly released on the old water portion of the discharge and concentrations peak in the early autumn when flows in the study catchments are at their lowest; (4) total fluvial carbon flux from the clear‐felled catchment is 11·6 t km⁻² year⁻¹ and for the control catchment is 11·4 t km⁻² year⁻¹. The total inorganic carbon flux represents 69% of the total fluvial carbon flux. The method presented in the study provides a useful way of estimating inorganic carbon flux from a catchment without detailed gas monitoring. The time series of dissolved CO₂ at emergence to the stream can also be a proxy for the soil flux of CO₂. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Characterizing and classifying urban watersheds with compositional and structural attributes     

Joseph M. Delesantro  Jonathan M. Duncan  Diego Riveros-Iregui  Joanna R. Blaszczak  Emily S. Bernhardt  Dean L. Urban  Lawrence E. Band 《水文研究》2021,35(9):e14339

Current land-use classifications used to assess urbanization effects on stream water quality date back to the 1980s when limited information was available to characterize watershed attributes that mediate non-point source pollution. With high resolution remote sensing and widely used GIS tools, there has been a vast increase in the availability and precision of geospatial data of built environments. In this study, we leverage geospatial data to expand the characterization of developed landscapes and create a typology that allows us to better understand the impact of complex developed landscapes across the rural to urban gradient. We assess the ability of the developed landscape typology to reveal patterns in stream water chemistry previously undetected by traditional land-cover based classification. We examine the distribution of land-cover, infrastructure, topography and geology across 3876 National Hydrography Dataset Plus catchments in the Piedmont region of North Carolina, USA. From this dataset, we generate metrics to evaluate the abundance, density and position of landscape features relative to streams, catchment outlets and topographic wetness metrics. While impervious surfaces are a key distinguishing feature of the urban landscape, sanitary infrastructure, population density and geology are better predictors of baseflow stream water chemistry. Unsupervised clustering was used to generate a distinct developed landscape typology based on the expanded, high-resolution landscape feature information. Using stream chemistry data from 37 developed headwater catchments, we compared the baseflow water chemistry grouped by traditional land-cover based classes of urbanization (rural, low, medium and high density) to our composition and structure-based classification (a nine-class typology). The typology based on 22 metrics of developed landscape composition and structure explained over 50% of the variation in NO₃⁻-N, TDN, DOC, Cl⁻, and Br⁻ concentration, while the ISC-based classification only significantly explained 23% of the variation in TDN. These results demonstrate the importance of infrastructure, population and geology in defining developed landscapes and improving discrete classes for water management.  相似文献   

Hydrological flow paths controlling stream chemistry in Japanese forested watersheds     

Kiyokazu Ohrui  Myron J. Mitchell 《水文研究》1999,13(6):877-888

Water sources and flow paths contributing to stream chemistry were evaluated in four Japanese forested watersheds with steep topography (slopes ≥30°). Stream chemistry during periods without rainfall and during events with less than 100 mm of precipitation was similar to seepage water chemistry, but markedly different from that of soil water which had higher concentrations of NO⁻₃ and Ca²⁺ and lower concentrations of Na⁺ and HCO⁻₃. Also, stream Cl⁻ concentrations in a Cl⁻‐treated watershed did not increase either during events with less than 100 mm of total rainfall or at baseflow conditions, even three years after the Cl⁻ treatment. These results suggest that groundwater within bedrock fissures of Paleozoic strata had a long residence time and was a major contributor to steam water under baseflow conditions and even during small precipitation events (≤100 mm). In contrast, for large precipitation events (≥100 mm), stream chemistry became more similar to soil water chemistry, especially within the steepest watershed. Also, for large precipitation events, stream Cl⁻ concentrations in the Cl⁻‐treated watershed increased markedly. These results suggest that soil water was a major contributor to stream waters only during these large events. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Influence of basin characteristics on baseflow and stormflow chemistry in the Great Smoky Mountains National Park,USA     

Keil J. Neff  John S. Schwartz  Stephen E. Moore  Matt A. Kulp 《水文研究》2013,27(14):2061-2074

Relationships between stream chemistry and elevation, area, Anakeesta geology, soil properties, and dominant vegetation were evaluated to identify the influence of basin characteristics on baseflow and stormflow chemistry in eight streams of the Great Smoky Mountains National Park. Statistical analyses were employed to determine differences between baseflow and stormflow chemistry, and relate basin‐scale factors governing local chemical processes to stream chemistry. Following precipitation events, stream pH was reduced and aluminium concentrations increased, while the response of acid neutralizing capacity (ANC), nitrate, sulfate, and base cations varied. Several basin characteristics were highly correlated with each other, demonstrating the interrelatedness of topographical, geological, soil, and vegetative parameters. These interrelated basin factors uniquely influenced acidification response in these streams. Streams in higher‐elevation basins (>975 m) had significantly lower pH, ANC, sodium, and silicon and higher nitrate concentrations (p < 0.05). Streams in smaller basins (<10 km²) had significantly lower nitrate, sodium, magnesium, silicon, and base cation concentrations. In stormflow, streams in basins with Anakeesta geology (>10%) had significantly lower pH and sodium concentrations, and higher aluminium concentrations. Chemical and physical soil characteristics and dominant overstory vegetation in basins were more strongly correlated with baseflow and stormflow chemical constituents than topographical and geological basin factors. Saturated hydraulic conductivity, of all the soil parameters, was most related to concentrations of stormflow constituents. Basins with higher average hydraulic conductivities were associated with lower stream pH, ANC, and base cation concentrations, and higher nitrate and sulfate concentrations. These results emphasize the importance of soil and geological properties influencing stream chemistry and promote the prioritization of management strategies for aquatic resources. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Seasonal mixing from intermittent flow drives concentration-discharge behaviour in a stream affected by coal mine drainage     

Meaghan Shaw  Lindsey Yazbek  David Singer  Elizabeth Herndon 《水文研究》2020,34(17):3669-3682

Abandoned mining operations continue to severely degrade many ecosystems worldwide by releasing acidic water and/or heavy metals into surface and groundwater. Contaminant concentrations in affected streams vary with discharge in patterns that reflect both geochemical reactions and variable mixing of contaminated and non-contaminated waters. However, controls on concentration-discharge (C-Q) patterns remain unclear, particularly for constituents that experience changing solubility across redox and pH gradients. Understanding the C-Q behaviour of contaminants aids in predicting both downstream transport and effects on aquatic life under variable flow. Here, we examined the C-Q behaviours of non-reactive (Na, K, Ca, Mg, Cl⁻) and reactive (Fe, Mn, Al, H⁺, SO₄²⁻) solutes in a stream contaminated with acid mine drainage in northeastern Ohio, USA. Concentration-discharge patterns at the watershed outlet primarily reflected mixing of contaminated baseflow with intermittent inputs of high pH water draining from a passive limestone treatment system into the stream. The treatment system acted as an ephemeral tributary that mitigated contamination in the stream by diluting solutes, raising pH, and driving metal precipitation, but only when flow was present during wet seasons. Consequently, AMD-derived reactive solutes (H⁺, Fe, Mn, Al) decreased with increasing stream discharge while relatively conservative solutes (e.g., Ca, Mg, K, Na) decreased only slightly or were chemostatic. This study highlights both the unique C-Q patterns of reactive solutes when compared to those of non-reactive solutes and the potential for intermittent streams to control C-Q behaviour in headwater catchments.  相似文献   

The controls on boreal peatland surface water chemistry in Northern Alberta,Canada     

Colin J. Whitfield  Julian Aherne  John J. Gibson  Tim A. Seabert  Shaun A. Watmough 《水文研究》2010,24(15):2143-2155

Spatial and temporal variability in surface water chemistry, organic soil chemistry and hydrologic indicators were investigated at three poor‐fen complexes in two boreal catchments in Northern Alberta to provide insight into the dominant controls on surface water chemistry. Improved understanding of these controls is required to enable prediction of runoff chemistry in the region under changing atmospheric deposition conditions. Surface water chemistry exhibited considerable variability; within each fen conductivity, dissolved organic carbon (DOC), and Cl⁻ tended to decrease and pH tended to increase with increasing distance from the lake edge. Variations in evaporative isotopic enrichment in ²H and ¹⁸O, expressed as deuterium excess, were used to distinguish between throughflow waters and those that were more evaporatively enriched. Throughflow surface waters were more acidic primarily due to higher concentrations of DOC and NO₃⁻. Exchangeable base saturation and pH of organic soils were strongly related to surface water chemistry at two of the fen complexes, demonstrating the capacity for cation exchange to influence surface water chemistry. Fen surface water concentrations of most elements and DOC increased during the summer period (between June and August), while pH of water decreased. Evaporative concentration of the surface waters was a dominant driver, with surface water temperature increasing at both catchments. Localized groundwater discharge was an important contributor of base cations to the fens, while the organic soils are sinks for atmospherically deposited SO₄²⁻, N and Cl⁻. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Controls on surface water chemistry in two lake‐watersheds in the Adirondack region of New York: differences in nitrogen solute sources and sinks     

Mari Ito  Myron J. Mitchell  Charles T. Driscoll  Robert M. Newton  Chris E. Johnson  Karen M. Roy 《水文研究》2007,21(10):1249-1264

The southwestern Adirondack region of New York receives among the highest rates of atmospheric nitrogen (N) deposition in the USA. Atmospheric N deposition to sensitive ecosystems, like the Adirondacks, may increase the acidification of soils through losses of exchangeable nutrient cations, and the acidification of surface waters associated with enhanced mobility of nitrate (NO₃^?). However, watershed attributes, including surficial terrestrial characteristics, in‐lake processing, and geological settings, have been found to complicate the relationships between atmospheric N deposition and N drainage losses. We studied two lake‐watersheds in the southwestern Adirondacks, Grass Pond and Constable Pond, which are located in close proximity (～26 km) and receive similarly high N deposition, but have contrasting watershed attributes (e.g. wetland area, geological settings). Since the difference in the influence of N deposition was minimal, we were able to examine both within‐ and between‐watershed influences of land cover, the contribution of glacial till groundwater inputs, and in‐lake processes on surface water chemistry with particular emphasis on N solutes and dissolved organic carbon (DOC). Monthly samples at seven inlets and one outlet of each lake were collected from May to October in 1999 and 2000. The concentrations of NO₃^? were high at the Grass Pond inlets, especially at two inlets, and NO₃^? was the major N solute at the Grass Pond inlets. The concentrations of likely weathering products (i.e. dissolved Si, Ca²⁺, Mg²⁺, Na⁺) as well as acid neutralizing capacity and pH values, were also particularly high at those two Grass Pond inlets, suggesting a large contribution of groundwater inputs. Dissolved organic N (DON) was the major N solute at the Constable Pond inlets. The higher concentrations of DON and DOC at the Constable Pond inlets were attributed to a large wetland area in the watershed. The DOC/DON ratios were also higher at the Constable Pond inlets, possibly due to a larger proportion of coniferous forest area. Although DON and DOC were strongly related, the stronger relationship of the proportion of wetland area with DOC suggests that additional factors regulate DON. The aggregated representation of watershed physical features (i.e. elevation, watershed area, mean topographic index, hypsometric‐analysis index) was not clearly related to the lake N and DOC chemistry. Despite distinctive differences in inlet N chemistry, NO₃^? and DON concentrations at the outlets of the two lakes were similar. The lower DOC/DON ratios at the lake outlets and at the inlets having upstream ponds suggest the importance of N processing and organic N sources within the lakes. Although an inverse relationship between NO₃^? and DOC/DON has been suggested to be indicative of a N deposition gradient, the existence of this relationship for sites that receive similar atmospheric N deposition suggest that the relationship between NO₃^? and the DOC/DON ratio is derived from environmental and physical factors. Our results suggest that, despite similar wet N deposition at the two watershed sites, N solutes entering lakes were strongly affected by hydrology associated with groundwater contribution and the presence of wetlands, whereas N solutes leaving lakes were strongly influenced by in‐lake processing. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Water age in stormwater management ponds and stormwater management pond-treated catchments     

Kayla Morales  Claire Oswald 《水文研究》2020,34(8):1854-1867

Expansion of impervious surface cover results in “flashy” hydrologic response, elevated flood risk, and degraded water quality in urban watersheds. Stormwater management ponds (SWMPs) are often engineered into stream networks to mitigate these issues. A clearer understanding of how water is stored and released from SWMPs and SWMP-treated catchments is required to better represent these engineered systems in hydrological and water quality models of urban and urbanizing watersheds. Stable water isotopes were used to compare water age in SWMPs and SWMP-treated catchments in an urbanizing watershed. We sampled water biweekly from two SWMPs and five stream sites with varying land cover and stormwater control in their catchments. Two inverse transit time proxies (damping ratio and young water fraction) were computed along with the mean transit time (MTT) by sine–wave fitting for each SWMP and stream site using the δ¹⁸O and δ²H data. Water entering the SWMPs was consistently older (224 and 177 days) than water in or exiting the ponds (ranging from 46 to 91 days and 39 to 67 days, respectively). This finding is likely due to a combination of groundwater infiltration into broken sewer pipes that transport water into the ponds and a bias toward baseflow sampling. At the catchment scale, detention provided by SWMPs was not found to be more significant than the interactive effects of impervious cover, surficial geology, land use proportions, and catchment size in determining MTT. Overall, surficial geology explained the most variation in MTT among the seven sites. This study illustrates the potential for isotope-based approaches of water age to provide information on individual SWMP functioning and the influence of SWMPs on catchment-scale water movement.  相似文献   

Comparison of nitrate export patterns in forested catchments in Japan and the Northeastern United States: A meta‐analysis     

Nobuhito Ohte  Masanori Katsuyama 《水文研究》2019,33(25):3184-3194

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Reconstructing long‐term records of dissolved CO2     

Fred Worrall  Tim Burt 《水文研究》2005,19(9):1791-1806

The dissolved CO₂ concentration of stream waters is an important component of the terrestrial carbon cycle. This study reconstructs long‐term records of dissolved CO₂ concentration for the outlets of two large catchments (818 and 586 km²) in northern England. The study shows that:

• 1. The flux of dissolved CO₂ from the catchments (as carbon per catchment area), when adjusted for that which would be carried by the river water at equilibrium with the atmosphere, is between 0 and 0·39 t km⁻² year⁻¹ for the River Tees and between 0 and 0·65 t km⁻² year⁻¹ for the River Coquet.
• 2. The flux of dissolved CO₂ is closely correlated with dissolved organic carbon (DOC) export and is unrelated to dissolved CO₂ export from the headwaters of the study catchments.
• 3. The evasion rate of CO₂ from the rivers (as carbon per stream area) is between 0·0 and 1·49 kg m⁻² year⁻¹, and calculated in‐stream productions of CO₂ are estimated as between 0·5 and 2·5% of the stream evasion rate.
• 4. By mass balance, it is estimated that 8% of the annual flux of DOC is lost within the streams of the catchment.

The study shows that the loss of CO₂ from the streams of the Tees catchment is between 3·1 and 7·5 kt year⁻¹ (as carbon) for the River Tees, which is the same order as annual CH₄ flux from peats within the catchment and approximately 50% of the net CO₂ exchange to the peats of the catchment. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Manganese in runoff from upland catchments: temporal patterns and controls on mobilization / Teneur en manganèse de l'écoulement en bassins versants d'altitude: variations temporelles et contrôles de la mobilisation     

K. V. HEAL  P. E. KNEALE  A. T. McDONALD 《水文科学杂志》2013,58(5):769-780

Abstract

Knowledge of the hydrochemical dynamics of the trace metal manganese (Mn) in upland catchments is required for water quality management. Stream water Mn and other solutes and flow were monitored in two upland catchments in northern England with different soils: one dominated by peat (HS7), the other by mineral soils (HS4). Maximum Mn concentrations occurred at different times in the two catchments: in summer baseflow at HS4 and during late summer storm events at HS7. A two-component chemical mixing model was used to identify the hydrological processes controlling Mn concentrations in stream water. This approach was more successful for HS4 than HS7, probably because of different processes of Mn release in the two catchments and also difficulties in selecting conservative solutes. Factor analysis of the stream water chemistry data set for each catchment was more useful in identifying the controls on Mn release into runoff. The factors indicate that the main source of Mn at HS4 is the hydrological pathway supplying summer baseflow, whereas at HS7 Mn is released during the rewetting of dried peat soils. Manganese concentrations in stream water in upland catchments appear to depend on soil type and antecedent moisture conditions. This has implications for the design of sampling strategies in upland catchments and also for managing the quality of water supplies from such areas.  相似文献   

CONTROLS ON SURFACE WATER CHEMISTRY IN THE UPPER MERCED RIVER BASIN,YOSEMITE NATIONAL PARK,CALIFORNIA     

DAVID W. CLOW  M. ALISA MAST  DONALD H. CAMPBELL 《水文研究》1996,10(5):727-746

Surface water draining granitic bedrock in Yosemite National Park exhibits considerable variability in chemical composition, despite the relative homogeneity of bedrock chemistry. Other geological factors, including the jointing and distribution of glacial till, appear to exert strong controls on water composition. Chemical data from three surface water surveys in the upper Merced River basin conducted in August 1981, June 1988 and August 1991 were analysed and compared with mapped geological, hydrological and topographic features to identify the solute sources and processes that control water chemistry within the basin during baseflow. Water at most of the sampling sites was dilute, with alkalinities ranging from 26 to 77 μequiv. l⁻¹. Alkalinity was much higher in two subcatchments, however, ranging from 51 to 302 μequiv. l⁻¹. Base cations and silica were also significantly higher in these two catchments than in the rest of the watershed. Concentrations of weathering products in surface water were correlated to the fraction of each subcatchment underlain by surficial material, which is mostly glacial till. Silicate mineral weathering is the dominant control on concentrations of alkalinity, silica and base cations, and ratios of these constituents in surface water reflect the composition of local bedrock. Chloride concentrations in surface water samples varied widely, ranging from <1 to 96 μequiv. l⁻¹. The annual volume-weighted mean chloride concentration in the Merced River at the Happy Isles gauge from 1968 to 1990 was 26 μequiv. l⁻¹, which was five times higher than in atmospheric deposition (4–5 μequiv. l⁻¹), suggesting that a source of chloride exists within the watershed. Saline groundwater springs, whose locations are probably controlled by vertical jointing in the bedrock, are the most likely source of the chloride. Sulphate concentrations varied much less than most other solutes, ranging from 3 to 14 μequiv. l⁻¹. Concentrations of sulphate in quarterly samples collected at the watershed outlet also showed relatively little variation, suggesting that sulphate may be regulated to some extent by a within-watershed process, such as sulphate adsorption.  相似文献   

Chemistry of streams draining grassland and forest catchments at Plynlimon,mid-Wales     

B. REYNOLDS  M. HORNUNG  S. HUGHES 《水文科学杂志》2013,58(6):667-686

Abstract

The chemistry of streamwater, bulk precipitation, throughfall and soil waters has been studied for three years in two plantation forest and two moorland catchments in mid-Wales. Na and CI are the major ions in streamwater reflecting the maritime influence on atmospheric inputs. In all streams, baseflow is characterised by high pH waters enriched in Ca, Mg, Si and HCO³. Differences in baseflow chemistry between streams reflect the varying extent of calcite and base metal sulphide mineralization within the catchments. Except for K, mean stream solute concentrations are higher in the unmineralized and mineralized forest catchments compared with their respective grassland counterparts. In the forest streams, storm flow concentrations of H⁺ are approximately 1.5 times and Al four times higher than in the moorland streams. Annual catchment losses of Na, Cl, SO⁴, NO³, Al and Si are greatest in the forest streams. In both grassland and forest systems, variations in stream chemistry be explained by mixing waters from different parts of the catchment, although NO³ concentrations may additionally be controlled by N transformations occurring between soils and streams. Differences in stream chemistry and solute budgets between forest and moorland catchments are related to greater atmospheric scavenging by the trees and changes in catchment hydrology consequent on afforestation. Mineral veins within the catchment bedrock can significantly modify the stream chemical response to afforestation.  相似文献   

The GEOMON network of Czech catchments provides long-term insights into altered forest biogeochemistry: From acid atmospheric deposition to climate change     

Filip Oulehle  Milan Fischer  Jakub Hruška  Tomáš Chuman  Pavel Krám  Tomáš Navrátil  Miroslav Tesař  Miroslav Trnka 《水文研究》2021,35(5):e14204

In 1994, a network of small catchments (GEOMON) was established in the Czech Republic to determine input–output element fluxes in semi-natural forest ecosystems recovering from anthropogenic acidification. The network consists from 16 catchments and the primary observations of elements fluxes were complemented by monitoring of biomass stock, element pools in soil and vegetation, and the main water balance components. Over last three decades, reductions of SO₂, NO_x and NH₃ emissions were followed by sulphur (S) and nitrogen (N) deposition reductions of 75% and 30%, respectively. Steeper declines of strong acid anion concentrations compared to cations (Ca, Mg, Na, K, NH₄) in precipitation resulted in precipitation pH increase from 4.5 to 5.2 in bulk precipitation and from 4.0 to 5.1 in spruce throughfall. Stream chemistry responded to changes in deposition: S leaching declined. However at majority of catchments soils acted as a net source of S to runoff, delaying recovery. Stream pH increased at acidic streams (pH < 6) and aluminium concentration decreased. Stream nitrate (NO₃) concentration declined by 60%, considerably more than N deposition. Stream NO₃ concentration was tightly positively related to stream total dissolved nitrogen to total phosphorus (P) ratio, suggesting the role of P availability on N retention. Trends in dissolved organic carbon fluxes responded to both acidification recovery and to runoff temporal variation. An exceptional drought occurred between 2014 and 2019. Over this recent period, streamflow decreased by ≈ 40% on average compared to 1990s, due to the increases of soil evaporation and vegetation transpiration by ≈ 30% and declines in precipitation by ≈ 15% on average across the elevational gradient. Sharp decreases of stream runoff at catchments <650 m a.s.l. corresponded to areas of recent forest decline caused by bark beetle infestation on drought stressed spruce forests. Understanding of the interactions among legacies of acidification and eutrophication, drought effects on the water cycle and forest disturbance dynamics is requisite for effective management of forested ecosystems under anthropogenic influence.  相似文献   

Alkalinity and dissolved inorganic carbon exports from tropical and subtropical river catchments discharging to the Great Barrier Reef,Australia     

Judith A. Rosentreter  Bradley D. Eyre 《水文研究》2020,34(7):1530-1544

Dissolved inorganic carbon (DIC) transport by rivers is an important control on the pH and carbonate chemistry of the coastal ocean. Here, we combine DIC and total alkalinity (TAlk) concentrations from four tropical rivers of the Great Barrier Reef region in Australia with daily river discharge to quantify annual river loads and export rates. DIC in the four rivers ranged from 284 to 2,639 μmol kg⁻¹ and TAlk ranged from 220 to 2,612 μmol kg⁻¹. DIC:TAlk ratios were mostly greater than one suggesting elevated exports of free [CO₂*]. This was pronounced in the Johnstone and Herbert rivers of the tropical wet north. The largest annual loads were transported in the two large river catchments of the southern Great Barrier Reef region, the Fitzroy and Burdekin rivers. The carbon stable isotopic composition of DIC suggests that carbonate weathering was the dominant source of DIC in the southern rivers, and silicate weathering was likely a source of DIC in the northern Wet Tropics rivers. Annual loads and export rates were strongly driven by precipitation and discharge patterns, the occurrence of tropical cyclones, and associated flooding events, as well as distinct seasonal dry and wet periods. As such, short-lived hydrological events and long-term (seasonal and inter-annual) variation of DIC and TAlk that are pronounced in rivers of the tropical and subtropical wet and dry climate zone should be accounted for when assessing inorganic carbon loads to the coastal ocean and the potential to buffer against or accelerate ocean acidification.  相似文献   

From on high: Geochemistry of alpine springs,Niwot Ridge,Colorado Front Range,USA     

Jordan F. Fields  David P. Dethier 《水文研究》2019,33(12):1756-1774

Snowmelt‐fed springs and small (0.5 km²) upland catchments in alpine areas of the western United States contribute significantly to the quantity and inorganic chemistry of water delivered to downstream basins but have not been studied extensively. Mineral weathering, transit time, and hydrologic mixing control the solute chemistry of waters that drain the upland zone of Niwot Ridge, Colorado Front Range, and adjacent areas in the granitic core of the Southern Rocky Mountains. Water in 37 springs sampled in this study flows in generally short steep paths (~0.3 km) through shallow regolith with mean transit times (MTT) of weeks to months, producing solutions dominated by Si, Ca²⁺, Na⁺, and HCO₃^?, locally SO₄^2?. Rock type is a significant control on spring, surface, and shallow groundwater chemistry, and plagioclase (oligoclase) is the major source of dissolved Na⁺ and Si. Concentrations of Ca²⁺ exceed stoichiometric predictions of oligoclase weathering by ~3.5×; excess Ca²⁺ likely represents weathering of aeolian material, vein calcite, or trace minerals. Concentrations of base cations and Si increase slowly with estimated MTT of 0.2 years for Niwot Ridge spring waters, and several years for shallow groundwater sampled by wells. Chemical weathering of silicate minerals is slow with estimated rates of ~2.0 and 0.2 pmol·m^?2·s^?1 for oligoclase and microcline, respectively; the most mineralized spring waters are saturated only with respect to kaolinite and montmorillonite. More than 50% of the dissolved base cations + Si measured in Boulder Creek at Orodell (~25 km downstream) accumulate before water emerges from alpine springs on Niwot Ridge. Warming global temperatures are shifting more high‐elevation precipitation to rain, potentially changing run‐off patterns, transit time, and solute loads. Acquisition of solutes by alpine waters thus has implications far beyond small upland catchments.  相似文献   

Spatial patterns of soil nitrate in Japanese forested watersheds: importance of the near-stream zone as a source of nitrate in stream water     

Kiyokazu Ohrui  Myron J. Mitchell 《水文研究》1998,12(9):1433-1445

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   

Solute provenance,transport and denudation in a high arctic glacierized catchment     

R. Hodgkins  M. Tranter  J. A. Dowdeswell 《水文研究》1997,11(14):1813-1832

Recent understanding of chemical weathering in glacierized catchments has been focused on mid-latitude, Alpine catchments; comparable studies from the high latitudes are currently lacking. This paper attempts to address this deficiency by examining solute provenance, transport and denudation in a glacierized catchment at 78°N in the Svalbard High Arctic archipelago. Representative samples of snow, glacier ice, winter proglacial icing and glacier meltwater were obtained from the catchment during spring and summer 1993 and analysed for major ion chemistry. Seasonal variations in the composition of glacier meltwater occur and are influenced by proglacial solute acquisition from the icing at the very start of the melt season, and subsequently by a period of discharge of concentrated snowmelt caused by snowpack elution; weathering within the ice-marginal channels that drain the glacier, particularly carbonation reactions, continues to furnish solute to meltwater when suspended sediment concentrations increase later in the melt season. Partitioning the solute flux into its various components (sea-salt, crustal, aerosol and atmospheric sources) shows that c. 25% of the total flux is sea salt derived, consistent with the maritime location of the glacier, and c. 71% is crustally derived. Estimated chemical denudation, 160 meq m⁻² a⁻¹ sea salt-corrected cation equivalent weathering rate, is somewhat low compared with other studied glacierized catchments (estimates in the range 450–1000 meq m⁻² a⁻¹), which is probably attributable to the relatively short melt season and low specific runoff in the High Arctic. A positive relationship was identified between discharge and CO₂ drawdown owing to carbonation reactions in turbid meltwater. © 1997 John Wiley & Sons, Ltd.  相似文献   

Factors controlling the acid‐neutralizing capacity of Japanese cedar forest watersheds in stands of various ages and topographic characteristics     

Keitaro Fukushima  Naoko Tokuchi 《水文研究》2009,23(2):259-271

Acid‐neutralizing capacity (ANC) is an important index for streamwater acidification caused by external factors (i.e. chronic acid deposition) and internal factors such as soil acidification due to nitrification. In this study, the influence of forest clear‐cutting and subsequent regrowth on internal acidification was investigated in central Japan, where stream pH (near 7·0) and ANC (above 0·1 meq L^?1) are high. pH, the concentrations of major cations (Na⁺, K⁺, Mg²⁺ and Ca²⁺), major anions (NO₃^?, Cl^? and SO₄^2?) and dissolved silica (Si), and ANC were measured in 33 watersheds of various stand ages, during 2002 to 2004. Only NO₃^? concentration decreased with stand age, whereas pH, ANC, and concentrations of the sum of base cations (BC) and Si were negatively correlated with the minimum elevation of the watershed. The correlation between the BC/Si ratio and minimum elevation suggested that factors contributing to acid neutralization changed at 1100 m above sea level. In watersheds at lower elevations (?1100 m), the relatively high contribution of soil water with longer soil contact times should result in higher ANC, and cation exchange reactions should be the dominant process for acid neutralization due to deposition of colluvial soils on the lower slope. In contrast, in higher‐elevation watersheds (≥1100 m), weathered residual soils are thin and the small contribution of deeper groundwater results in lower ANC. These results suggest that the local acid sensitivity is determined by the hydrological and geomorphologic factors generated by steep topography. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

The seasonal variation of streamwater chemistry in three forested Mediterranean catchments     

Josep Pi  ol  Anna   vila  Ferran Rod 《Journal of Hydrology》1992,140(1-4):119-141

Streamwater chemistry is described for three streams draining undisturbed, evergreen broad-leaved forested catchments on phyllites in NE Spain: two streams with no or negligible flow in summer are located in the Prades massif, and one perennial stream is in the wetter Montseny mountains. Weekly data for a study period of 2–4 years are provided to (1) describe the seasonal variations in streamwater chemistry, (2) analyse the relationship between stream discharge and solute concentrations using a two-component mixing model and (3) search for patterns of temporal variation in stream solute concentrations after discounting the effects of discharge. At Prades, concentrations of all analysed ions, except NO⁻₃, showed marked seasonal variations in stream water, whereas at Montseny only ions related to mineral weathering (HCO⁻₃, Na⁺, Ca²⁺ and Mg²⁺) showed strong seasonality. Ion concentrations were more closely dependent on instantaneous discharge at Montseny than at Prades. The residuals of the relationship between solute concentrations and discharge retained a strong seasonality at Prades, but not at Montseny. These differences are related to the major hydrochemical processes that determine the streamwater chemistry at each site. The same processes are probably operative in the three catchments, but are of varying relative importance. At Montseny, the mixing of waters of different chemical composition seems to be the major process controlling streamwater chemistry, although the soilwater end-member composition predicted by the mixing model applied did not match the measured soilwater chemistry. In the drier Prades catchments, the two major hydrochemical processes determining the seasonal variation of streamwater chemistry are (1) the restart of flow after the summer drought, which flushes out the solutes accumulated during the dry period, and (2) the seasonal changes in groundwater chemistry that result from the interplay of water residence time, temperature and CO₂ partial pressure. In Mediterranean catchments with relatively high precipitation, such as Montseny, the seasonal variation in the streamwater chemistry is largely determined by the same processes as at humid-temperate sites, whereas in drier Mediterranean catchments, such as Prades, the major hydrochemical processes are clearly distinct.  相似文献