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Susana Bernal - One of the best experts on this subject based on the ideXlab platform.

  • decoupling of dissolved organic matter patterns between stream and riparian groundwater in a headwater Forested Catchment
    Hydrology and Earth System Sciences, 2017
    Co-Authors: Susana Bernal, Anna Lupon, Nuria Catalan, Sara Castelar, Eugenia Marti
    Abstract:

    Abstract. Streams are important sources of carbon to the atmosphere, though knowing whether they merely outgas terrestrially derived carbon dioxide or mineralize terrestrial inputs of dissolved organic matter (DOM) is still a big challenge in ecology. The objective of this study was to investigate the influence of riparian groundwater (GW) and in-stream processes on the temporal pattern of stream DOM concentrations and quality in a Forested headwater stream, and whether this influence differed between the leaf litter fall (LLF) period and the remaining part of the year (non-LLF). The spectroscopic indexes (fluorescence index, biological index, humification index, and parallel factor analysis components) indicated that DOM had an eminently protein-like character and was most likely originated from microbial sources and recent biological activity in both stream water and riparian GW. However, paired samples of stream water and riparian GW showed that dissolved organic carbon (DOC) and nitrogen (DON) concentrations as well as the spectroscopic character of DOM differed between the two compartments throughout the year. A simple mass balance approach indicated that in-stream processes along the reach contributed to reducing DOC and DON fluxes by 50 and 30 %, respectively. Further, in-stream DOC and DON uptakes were unrelated to each other, suggesting that these two compounds underwent different biogeochemical pathways. During the LLF period, stream DOC and DOC : DON ratios were higher than during the non-LLF period, and spectroscopic indexes suggested a major influence of terrestrial vegetation on stream DOM. Our study highlights that stream DOM is not merely a reflection of riparian GW entering the stream and that headwater streams have the capacity to internally produce, transform, and consume DOM.

  • modelling the inorganic nitrogen behaviour in a small mediterranean Forested Catchment fuirosos catalonia
    Hydrology and Earth System Sciences, 2010
    Co-Authors: Chiara Medici, Andrea Butturini, Susana Bernal, Francesc Sabater, Miguel Martin, A J Wade, Felix Frances
    Abstract:

    The aim of this work was to couple a nitrogen (N) sub-model to already existent hydrological lumped (LU4-N) and semi-distributed (LU4-R-N and SD4-R-N) conceptual models, to improve our understanding of the factors and processes controlling nitrogen cycling and losses in Mediterranean Catchments. The N model adopted provides a simplified conceptualization of the soil nitrogen cycle considering mineralization, nitrification, immobilization, denitrification, plant uptake, and ammonium adsorption/desorption. It also includes nitrification and denitrification in the shallow perched aquifer. We included a soil moisture threshold for all the considered soil biological processes. The results suggested that all the nitrogen processes were highly influenced by the rain episodes and that soil microbial processes occurred in pulses stimulated by soil moisture increasing after rain. Our simulation highlighted the riparian zone as a possible source of nitrate, especially after the summer drought period, but it can also act as an important sink of nitrate due to denitrification, in particular during the wettest period of the year. The riparian zone was a key element to simulate the Catchment nitrate behaviour. The lumped LU4-N model (which does not include the riparian zone) could not be validated, while both the semi-distributed LU4-R-N and SD4-R-N model (which include the riparian zone) gave satisfactory results for the calibration process and acceptable results for the temporal validation process.

  • modelling the non linear hydrological behaviour of a small mediterranean Forested Catchment
    Hydrological Processes, 2008
    Co-Authors: Chiara Medici, Andrea Butturini, Susana Bernal, Eusebi Vazquez, Francesc Sabater, Jaime I Velez, Felix Frances
    Abstract:

    A progressive perceptual understanding approach was used to identify a model structure able to represent the non-linear behaviour of the hydrological cycle in a small intermittent Mediterranean stream. The initial lumped model structure consisting of a series of four connected water tanks (LU3) progressed to a model with five tanks (LU4), and finally to a semidistributed model structure (SD4) in which spatial variability of the evapotranspiration according to the vegetation cover and to the local aspect was considered. In the final model structure, which gave the best fit (Nash–Sutcliffe efficiency index = 0·78), an additional tank representing the riparian zone was included (SD4-R). Results showed that the abrupt changes of the riparian water table during summer and the formation of a perched water table during the transition from dry to wet conditions were the main mechanisms leading to the non-linear hydrological behaviour. The transpiration process from the saturated zone and the spatial variability of evapotranspiration resulted in key factors successfully representing the annual water balance. The spatial and temporal validations carried out for each of the four model structures considered in this study supported the hypothesis adopted during the calibration process. Copyright © 2008 John Wiley & Sons, Ltd.

  • Variability of DOC and nitrate responses to storms in a small Mediterranean Forested Catchment
    Hydrology and Earth System Sciences Discussions, 2002
    Co-Authors: Susana Bernal, Andrea Butturini, Francesc Sabater
    Abstract:

    Severe drought periods followed by intense rainfall often leads to major floods in Mediterranean Catchments. The resulting hydrology is complex and the response of solutes in the streams is often unpredictable. This study aimed to identify the most relevant factors controlling the hydrological responses to storms of an intermittent Mediterranean stream and to link those factors with dissolved organic carbon (DOC) and nitrate during storm events. Measurements of climate, hydrology, DOC and nitrate concentrations during 26 storm events over three hydrological years were analysed. The contribution of the storm events to the total DOC and nitrate annual export was also calculated. Nitrate was mainly mobilised during high flow, while most of the DOC export occurred during baseflow. Solute concentrations peaked after drought periods and the solute export was maximal during the largest rainfalls (i.e. > 100 L m-2). One single large storm contributed some 22% of the total annual export of DOC, and about 80% of that of nitrate. Discharge was a good predictor of neither DOC nor nitrate responses, so variables other than discharge were considered. Factor Analysis was used to identify the main factors controlling the biogeochemical responses. Antecedent moisture conditions and the magnitude of the storm event were the most relevant factors and accounted for 63% of the total variance. Solute responses during high flow were highly variable. However, solute concentration changes showed a significant and moderate relationship with the factors controlling the hydrological responses (i.e. ? DOC v. the antecedent moisture conditions and ? NO3-N v. the magnitude of the storm event). Keywords: dissolved organic carbon, nitrate, Mediterranean, drought, Fuirosos Catchment, storms

Richard F Wright - One of the best experts on this subject based on the ideXlab platform.

  • nitrogen leaching and acidification during 19 years of nh4no3 additions to a coniferous Forested Catchment at gardsjon sweden nitrex
    Environmental Pollution, 2011
    Co-Authors: Filip Moldan, Richard F Wright
    Abstract:

    The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-Catchment experiment with N addition at Gardsjon, Sweden, to investigate the risk of N saturation. We have added 41 kg N ha(-1) yr(-1) as NH(4)NO(3) to the ambient 9 kg N ha(-1) yr(-1) in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO(3) in runoff partially offset the decreasing concentrations of SO(4) and slowed ecosystem recovery from acid deposition. From 1990-2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42-59 g g(-1).

  • increased nitrogen in runoff and soil following 13 years of experimentally increased nitrogen deposition to a coniferous Forested Catchment at gardsjon sweden
    Environmental Pollution, 2006
    Co-Authors: Filip Moldan, O J Kjonaas, A O Stuanes, Richard F Wright
    Abstract:

    Abstract Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-Forested Catchment G2 NITREX at Gardsjon, Sweden, to investigate the consequences of chronic elevated N deposition. We have added 40 kg N ha −1  yr −1 in fortnightly doses of NH 4 NO 3 to the ambient 15 kg N ha −1  yr −1 by means of a sprinkling system. NO 3 concentrations in runoff increased during 13 years from  −1 , and in 2004 comprised about 10% of N input. Inhibition of NO 3 immobilisation due to increased availability of NH 4 might explain the increased leaching of NO 3 . C and N pools in the forest floor increased but C/N ratio has not changed. The increase in NO 3 leaching thus occurred independently of change in C/N ratio. The results from Gardsjon demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales.

  • effect of increased carbon dioxide and temperature on runoff chemistry at a Forested Catchment in southern norway climex project
    Ecosystems, 1998
    Co-Authors: Richard F Wright
    Abstract:

    CLIMEX (Climate Change Experiment) is an integrated, whole-ecosystem research project that focuses on the response of forest ecosystems at the Catchment scale to increased CO2 and temperature. KIM Catchment (860 m2) is completely enclosed by a transparent greenhouse, receives deacidifed “clean” rain, and has elevated CO2 (560 ppmv) and elevated air temperature (3°–5°C above ambient). The uppermost 20% of the Catchment is partitioned off, is not subject to changed CO2 or temperature, and serves as an untreated control. Fluxes of nitrate and ammonium in runoff from KIM Catchment increased from 2 mmol m− 2 y− 1 each in the 3 years before treatment to 6 and 3 mmol m− 2 y− 1, respectively, in the 3 years after treatment (May 1994–April 1997), despite a 15 mmol m− 2 y− 1 decrease in N dry deposition due to the sealing of the walls to the enclosure. N flux in runoff from three reference Catchments and the control section did not change. The net loss of inorganic N was thus about 20 mmol m− 2 treated soil y− 1. There were no changes in organic N or total organic carbon in runoff. The ecosystem switched from a net sink to a net source of inorganic nitrogen (N). The increased loss of N may be due to accelerated decomposition of soil organic matter induced by higher temperature. Due to many decades of N deposition from long-range transported pollutants, the ecosystem prior to treatment was N saturated. If global change induces persistent losses of inorganic N on a regional scale, the result may be a significant increase in nitrate concentrations in fresh waters and N loading to coastal marine ecosystems. In regions with acid sensitive waters, such as southern Norway, the increased nitrate release caused by global change may offset improvements achieved by reduced sulfur and N deposition.

Peter J Dillon - One of the best experts on this subject based on the ideXlab platform.

  • metal pools fluxes and budgets in an acidified Forested Catchment on the precambrian shield central ontario canada
    Water Air and Soil Pollution, 2010
    Co-Authors: Amanda L Landre, Shaun A Watmough, Peter J Dillon
    Abstract:

    Atmospheric emissions of metals have decreased in North America; yet, metals remain an environmental concern due to their environmental persistence and toxicity to biota. In this study, pools and mass budgets were calculated for 15 metals in an acidified Forested Catchment in Central Ontario. Metals that were enriched in bulk deposition over background average values (As, Cd, Pb, Zn) were generally enriched in the forest floor and upper lake sediment. While the metal pool in vegetation is small compared with the soil pool, internal cycling of metals via litterfall is comparable to atmospheric deposition, soil water, and stream fluxes. Partitioning coefficients calculated from metal concentrations in soil water and bulk soil suggest that Cd, Mn, Ni, and Zn are the most mobile. The mineral soil and lake sediments were sinks for most metals, while the wetland was a source of metals during the study year, which was a drought year. Overall, lithogenic metals (Al, Ba, Co, Fe, Mn, Rb, Sr, Zn) primarily from a weathering source generally exhibited net export from the Catchment, while metals contained in atmospheric pollution (As, Cd, Cr, Cu, Ni, Pb, V) exhibited net retention. Despite the acidified nature of the Catchment, it functions to retain many pollutant metals.

  • the effects of dissolved organic carbon acidity and seasonality on metal geochemistry within a Forested Catchment on the precambrian shield central ontario canada
    Biogeochemistry, 2009
    Co-Authors: Amanda L Landre, Shaun A Watmough, Peter J Dillon
    Abstract:

    Metal pollution, in combination with other environmental stressors such as acid deposition and climate change, may disturb metal biogeochemical cycles. To investigate the influence of dissolved organic carbon, acidity and seasonality on metal geochemistry, this study has described concentrations of 19 metals as they pass through an acidified Forested Catchment on the Precambrian Shield in south-central Ontario, Canada. Metal, dissolved organic carbon (DOC) and sulphate (SO4 2−) concentrations fluctuate throughout the Catchment compartments as the water passes through and interacts with vegetation, soils and bedrock. Relationships among metals, DOC and SO4 2− are most pronounced in compartments where DOC and SO4 2− exhibit high variability, namely in the throughfall, organic horizon soil water, and wetland-draining stream. Metal, DOC and SO4 2− concentrations varied seasonally in the streams, and temporal coherence occurred among metal, DOC and SO4 2− concentrations in the organic horizon soil water and the wetland-draining stream (PC1). In the wetland-draining stream, the highest DOC, Cr, Cu, Fe, Pb, and V concentrations occur in the summer, whereas concentrations of SO4 2− and most other metals peak in the fall after a period of drought. Despite the rural location, provincial water quality objectives for surface water were exceeded for many metals when the peak fall values occurred.

Egbert Matzner - One of the best experts on this subject based on the ideXlab platform.

  • concentrations and fluxes of dissolved organic carbon in runoff from a Forested Catchment insights from high frequency measurements
    Biogeosciences, 2013
    Co-Authors: Stefan Strohmeier, Klausholger Knorr, Martin Reichert, Sven Frei, Jan H Fleckenstein, Stefan Peiffer, Egbert Matzner
    Abstract:

    Concentrations of dissolved organic carbon (DOC) in runoff from Catchments are often subject to substantial short-term variations. The aim of this study was to identify the compartmental sources of DOC in a Forested Catchment and the causes for short-term variations in runoff. Furthermore, we investigated the implication of short-term variations for the calculation of annual runoff fluxes. High frequency measurements (30 min intervals) of DOC in runoff, of discharge and groundwater table were conducted for one year in the 4.2 km 2 Forested Lehstenbach Catchment, Germany. Riparian wetland soils represent about 30% of the Catchment area. The quality of DOC was investigated by three dimensional fluorescence excitation-emission matrices in samples taken from runoff, deep groundwater and shallow groundwater from the riparian wetland soils. The concentrations of DOC in runoff were highly variable at an hourly to daily time scale, ranging from 2.6 mg L −1 to 34 mg L −1 with an annual average of 9.2 mg L −1 . The concentrations were positively related to discharge, with a counter clockwise hysteresis. Relations of DOC to discharge were steeper and the degree of hysteresis larger in the summer/fall than in the winter/spring period. Dynamics of groundwater table, discharge, DOC concentrations and DOC quality parameters indicated that DOC in runoff originated mainly from the riparian wetland soils, both under low and high flow conditions. The annual export of DOC from the Catchment was 84 kg C ha −1 yr −1 when calculated from the high frequency measurements. If the annual export was calculated by simulated samplings of >2 days intervals substantial deviations resulted. Predicted changes in precipitation and discharge patterns as well as generally increasing temperatures likely will cause raising DOC exports from this Catchment.

  • fluxes and budgets of cd zn cu cr and ni in a remote Forested Catchment in germany
    Biogeochemistry, 2011
    Co-Authors: Jenhow Huang, Gunter Ilgen, Egbert Matzner
    Abstract:

    The input of heavy metals by atmospheric deposition to Forested watersheds substantially decreased during the last decades in many areas. The goal of our study was to identify the present sinks and sources of metals and factors influencing metal mobility at the Catchment and soil profile scale. We determined concentrations and fluxes of Cd, Zn, Cu, Cr and Ni in precipitation, litterfall, soil solutions (Oi, Oe, Oa horizon percolates, 20 and 90 cm soil depth) and runoff in a forest ecosystem in NE-Bavaria, Germany for 1 year. The metal concentrations in solutions were mostly <10 μg l−1 beside Zn (<1200 μg l−1). The present total deposition was estimated at 1.0, 560, 30, 1.2 and 10.4 g ha−1 year−1 for Cd, Zn, Cu, Cr and Ni, respectively. The mass balance (total deposition minus runoff) at the Catchment scale indicated actual retention of Zn, Cu and Ni, but an almost balanced budget for Cr and Cd. Considering the soil profile scale, the Oi horizon still acted as a sink, whereas the Oe and Oa horizons were presently sources for all metals. The solid–solution partitioning coefficients indicated higher mobility of Cd and Zn than of Cu, Cr and Ni in forest soils. In the mineral soil horizons, Kd values derived from field measurements were substantially larger than those predicted with empirical regression equations from Sauve et al. (Environ Sci Technol 34:1125–1131, 2000; Environ Sci Technol 37:5191–5196, 2003). The mineral soil acted as a sink for all metals beside Cd. Dissolved organic C and pH influenced the metal mobility, as indicated by significant correlations to metal concentrations in Oa percolates and runoff. The solid–solution partitioning coefficients indicated higher mobility of Cd and Zn than of Cu, Cr and Ni in forest soils. Overall, the decreased deposition rates have obviously induced a source function of the Oe and Oa horizon for metals. Consequently, mobilization of metals from forest floor during heavy rain events and near surface flow conditions may lead to elevated concentrations in runoff.

  • biogeochemistry of organic and inorganic arsenic species in a Forested Catchment in germany
    Environmental Science & Technology, 2007
    Co-Authors: Jenhow Huang, Egbert Matzner
    Abstract:

    Little is known about the fate and behavior of diffuse inputs of arsenic (As) species in Forested Catchments which often are the sources of drinking water. The objective of this study was to investigate the mobility and transformation of different As species in forest ecosystems to assess the environmental risk related to the diffuse pollution of As. We determined concentrations and fluxes in precipitation, litterfall, soil solutions (Oa horizon and 20- and 90-cm depth), and runoff of organic and inorganic As species and Astotal in a forest ecosystem in NE-Bavaria, Germany. The concentrations of Astotal were mostly <1 microg As L(-1) in aqueous samples and were highest in forestfloor percolates (7.6 microg As L(-1)). In litterfall, the concentrations of As species never exceeded 0.1 microg As g(-1). Arsenate and arsenite were the prevalent As species in all samples. Organic As species, comprising monomethylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, arsenobetaine, and three unidentified organic As species, were mostly found in throughfall reaching up to 45% of Astotal. The total deposition of Astotal (calculated as throughfall + litterfall) was 5.6 g As ha(-1) yr(-1) with 16% contribution of litterfall. The annual Astotal fluxes were 30 g As ha(-1) yr(-1) for forest floor percolates, 8.0 g As ha(-1) yr(-1) at 20-cm soil depth, and 1.4 g As ha(-1) yr(-1) at 90-cm soil depth. The annual runoff of Astotal from the Catchment amounted to 3.8 g As ha(-1) yr(-1). The annual fluxes of total organic As species was highest in total deposition (1.1 g As ha(-1) yr(-1)) and decreased largely with depth in the soil profile. The annual runoff of total organic As species was only 0.08 g As ha(-1) yr(-1). Significant correlations in soil solutions and runoff were found between Astotal and dissolved organic C and Fe. Correlations between Astotal concentrations in runoff and water fluxes were seasonally dependent and with a steeper slope in the growing season than in the dormant season. The elevated concentrations of organic As species in throughfall indicate microbial methylation of As in the phyllosphere, but no evidence for methylation in the soil was found. The mass balance of the Catchment points out the strong retention and probable degradation or oxidation of organic As species and arsenite but also to mobilizable pools of Astotal and arsenate. The forest floor is presently a source, whereas the mineral soil is a sink for Astotal and arsenate. The As concentrations in runoff seem to be controlled by As mobilization from forest floor and riparian wetland soils during heavy rain events and superficial flow. The risk for excessment of the drinking water threshold concentrations of As in runoff and soil solutions is considered low at our site.

Francesc Sabater - One of the best experts on this subject based on the ideXlab platform.

  • modelling the inorganic nitrogen behaviour in a small mediterranean Forested Catchment fuirosos catalonia
    Hydrology and Earth System Sciences, 2010
    Co-Authors: Chiara Medici, Andrea Butturini, Susana Bernal, Francesc Sabater, Miguel Martin, A J Wade, Felix Frances
    Abstract:

    The aim of this work was to couple a nitrogen (N) sub-model to already existent hydrological lumped (LU4-N) and semi-distributed (LU4-R-N and SD4-R-N) conceptual models, to improve our understanding of the factors and processes controlling nitrogen cycling and losses in Mediterranean Catchments. The N model adopted provides a simplified conceptualization of the soil nitrogen cycle considering mineralization, nitrification, immobilization, denitrification, plant uptake, and ammonium adsorption/desorption. It also includes nitrification and denitrification in the shallow perched aquifer. We included a soil moisture threshold for all the considered soil biological processes. The results suggested that all the nitrogen processes were highly influenced by the rain episodes and that soil microbial processes occurred in pulses stimulated by soil moisture increasing after rain. Our simulation highlighted the riparian zone as a possible source of nitrate, especially after the summer drought period, but it can also act as an important sink of nitrate due to denitrification, in particular during the wettest period of the year. The riparian zone was a key element to simulate the Catchment nitrate behaviour. The lumped LU4-N model (which does not include the riparian zone) could not be validated, while both the semi-distributed LU4-R-N and SD4-R-N model (which include the riparian zone) gave satisfactory results for the calibration process and acceptable results for the temporal validation process.

  • modelling the non linear hydrological behaviour of a small mediterranean Forested Catchment
    Hydrological Processes, 2008
    Co-Authors: Chiara Medici, Andrea Butturini, Susana Bernal, Eusebi Vazquez, Francesc Sabater, Jaime I Velez, Felix Frances
    Abstract:

    A progressive perceptual understanding approach was used to identify a model structure able to represent the non-linear behaviour of the hydrological cycle in a small intermittent Mediterranean stream. The initial lumped model structure consisting of a series of four connected water tanks (LU3) progressed to a model with five tanks (LU4), and finally to a semidistributed model structure (SD4) in which spatial variability of the evapotranspiration according to the vegetation cover and to the local aspect was considered. In the final model structure, which gave the best fit (Nash–Sutcliffe efficiency index = 0·78), an additional tank representing the riparian zone was included (SD4-R). Results showed that the abrupt changes of the riparian water table during summer and the formation of a perched water table during the transition from dry to wet conditions were the main mechanisms leading to the non-linear hydrological behaviour. The transpiration process from the saturated zone and the spatial variability of evapotranspiration resulted in key factors successfully representing the annual water balance. The spatial and temporal validations carried out for each of the four model structures considered in this study supported the hypothesis adopted during the calibration process. Copyright © 2008 John Wiley & Sons, Ltd.

  • Variability of DOC and nitrate responses to storms in a small Mediterranean Forested Catchment
    Hydrology and Earth System Sciences Discussions, 2002
    Co-Authors: Susana Bernal, Andrea Butturini, Francesc Sabater
    Abstract:

    Severe drought periods followed by intense rainfall often leads to major floods in Mediterranean Catchments. The resulting hydrology is complex and the response of solutes in the streams is often unpredictable. This study aimed to identify the most relevant factors controlling the hydrological responses to storms of an intermittent Mediterranean stream and to link those factors with dissolved organic carbon (DOC) and nitrate during storm events. Measurements of climate, hydrology, DOC and nitrate concentrations during 26 storm events over three hydrological years were analysed. The contribution of the storm events to the total DOC and nitrate annual export was also calculated. Nitrate was mainly mobilised during high flow, while most of the DOC export occurred during baseflow. Solute concentrations peaked after drought periods and the solute export was maximal during the largest rainfalls (i.e. > 100 L m-2). One single large storm contributed some 22% of the total annual export of DOC, and about 80% of that of nitrate. Discharge was a good predictor of neither DOC nor nitrate responses, so variables other than discharge were considered. Factor Analysis was used to identify the main factors controlling the biogeochemical responses. Antecedent moisture conditions and the magnitude of the storm event were the most relevant factors and accounted for 63% of the total variance. Solute responses during high flow were highly variable. However, solute concentration changes showed a significant and moderate relationship with the factors controlling the hydrological responses (i.e. ? DOC v. the antecedent moisture conditions and ? NO3-N v. the magnitude of the storm event). Keywords: dissolved organic carbon, nitrate, Mediterranean, drought, Fuirosos Catchment, storms