Surface Water Distribution Research Articles

Positive gadolinium anomaly in surface water and ground water of the urban area Berlin, Germany

Rare-earth element (REE) distribution patterns of surface water and commonly also of ground water from industrialised and highly populated areas show anthropogenic gadolinium (Gd) anomalies. They result from the application of organic Gd compounds, such as the derivatives of the gadopentetic acid (Gd-DTPA), as a contrast medium in magnetic resonance imaging. After excretion from the human body, the Gd complex enters the surface water mostly by the effluents of sewage treatment plants. The chemical complex is very stable over at least 6 months under natural conditions. Owing to its anionic state, it is neither adsorbed onto surfaces of abundant clay mineral particles nor by particulate organic matter, both strongly contrasting with the behaviour of the free REE ions. Thus, this complex behaves like a pseudo-natural marker and provides a tool for tracing the mixing of surface and ground water with recycled water, and the infiltration of surface water into aquifers. In urban areas, where water production is commonly based on bank filtration, the anthropogenic Gd of the surface water can be followed to the water production wells. Like boron, δD and δ 18O, Gd can be used as a marker in the estimation of the recycled water fraction in ground water systems. Examples of anthropogenic Gd distribution in surface water, sewage and ground water in Berlin, Germany, are discussed. Mixing ratios of bank filtrates and ground water are estimated.

Characteristics of pCO2 in surface water of the Bering Abyssal Plain and their effects on carbon cycle in the

Characteristics of the pCO2 distribution in surface water of the Bering Abyssal Plain and their relationships with the ambient hydrological conditions were discussed using variations of the partial pressure of CO2 in surface water of the Bering Abyssal Plain and the Chukchi Sea. Data in this study are from a field investigation during the First Chinese National Arctic Research Expedition in 1999. Compared to the high productivity in the Bering Continental Shelf, much lower levels of chlorophyll a were observed in the Bering Abyssal Plain. The effect of hydrological factors on the pCO2 distribution in surface seawater of the Plain in summer has become a major driving force and dominated over biological factors. The Plain also presents a High Nutrient Low Chlorophyll (HNLC). In addition, the pCO2 distribution in the Bering Abyssal Plain has also been found to be influenced from the Bering Slope Current which would transform to the Anadyr Cur- rent when it inflows northwestward over the Plain. The Anadyr Current would bring a high nutrient water to the western Arctic Ocean where local nutrients are almost depleted in the surface water during the summer time. Resupplying nutrients would stimulate the growth of phytoplankton and enhance capacity of absorbing atmospheric CO2 in the surface water. Otherwise, in the Bering Sea the dissolved inorganic carbon brought from freshwater are not deposited down to the deep sea water but most of them would be transported into the western Arctic Ocean by the Alaska Coastal Current to form a carbon sink there. Therefore, the two carbon sinks in the western Arctic Ocean, one carried by the Anadyr Current and another by the Alaska Costal Current, will impli- cate the western Arctic Ocean in global change.

Development of a Management Model for a Surface Waterlogged and Drainage Congested Area

Inadequate drainage outlet causing surface waterlogging every year mainly during monsoon period (June through October) over a depressed land of 1062 km2 in Mokama group of tals, India, led to a loss of one crop rotation. A management model aiming at minimization of the waterlogged area under constraints of control monsoon runoffs from tributaries discharge water to the depressed land has been developed. Magnitudes of regulated flows are guided by irrigation water requirement of crops grown in commands of different tributaries joined to the depressed land. A nonlinear optimization model has been envisaged and solved setting a total of 160 constraints satisfying conditions of water requirement for crops grown in two seasons and their time-dependent storage requirement. The optimization model has been solved using the Quantitative Systems for Business (QSB) software, which considers a line search methodology for unconstrained problems, and a sequential unconstrained minimization technique (SUMT) with penalty function methodology for constrained problems. The management model provides a solution for strategic water resources development and management in a basin having problems of scarcity, surplus and non-uniform distribution of surface water.

Submicronic Raman and Transverse Dynamic Force Microscopy Spectroscopies to Investigate the Physical Chemistry of Surface Nanoheterogeneities

On the basis of an experimental example, this paper demonstrates the intrinsic complementary nature between the subwavelength Raman spectroscopy and the tip-sample interaction measurements, in a scanning near field optical microscope device. This paper displays a good illustration of possibilities given by this kind of device to study the interfaces in physical chemistry. The Raman spectra of the optical near field obtained on a lead sulfate sample shows that the surface of this sample is polluted by nanophases of copper sulfate. These impurities, which are not displayed by the usual backscattered far field Raman spectrum recorded in confocal Raman microspectroscopy, are localized at a subwavelength scale and are revealed by a particular behavior in transverse dynamic force (usually noted as shear force) measurements too, in comparison with those obtained over the surface of the lead sulfate sample free from impurities. These differences in probe-sample adhesion throughout a sample are caused by an inhomogeneous distribution of surface water, which is clearly explained by the chemical identification of the nanophases by Raman spectroscopy of the optical near field. The heterogeneous water adsorption at the sample/air interface under a reduced relative humidity is displayed by both the near field optical spectroscopy and the shear force microscopy measurements.

Mesozooplankton community structure in the Scotia Sea during the CCAMLR 2000 survey: January–February 2000

An analysis of mesozooplankton community structure in the Scotia Sea was carried out, based on 123 RMT1 double oblique hauls (0–200 m) taken during the CCAMLR 2000 Survey. Standardized sample data (log abundance per 1000 m3) were grouped into taxonomic categories and subjected to cluster analysis and multi-dimensional scaling. Two ordinations were performed, the first based on a reduced taxonomic dataset (31 categories out of a full 120) obtained by pooling ontogenetic stages within species and by including only those taxa that contributed at least 4% to total abundance at any one station. This disclosed two major station groups, which separated north and south, forming ‘warm’ and ‘cold’ water communities respectively, whereas four minor groups were mainly associated with stations around the Antarctic Peninsula and within the Weddell Scotia Confluence. Mean zooplankton abundance (238 000 individuals per 1000 m3) within the northerly group G1 was up to 12 times higher than in other groups. The second ordination using all taxonomic categories disclosed an additional intermediate group (G1a), which was geographically consistent with the southern part of the northern group 1 from the previous ordination. However, because of taxonomic similarities between all the major station groups it was concluded that they represented a single community, which differed only in its phenological development and the mass occurrence of patchily distributed organisms such as krill larvae. Testing the relationships of station groups with the position of water masses and frontal boundaries indicated that the Weddell Front was broadly coincident with the boundary of the northern and southern communities over much of its length. However, the presence of stations belonging to group G2, to the north of the Weddell Front, to the west of the Antarctic Peninsula, and around the South Sandwich Islands, was consistent with the distribution of ice-influenced surface water. Low zooplankton abundance and species developmental composition suggested that this ‘community’ was largely in an over-wintered state. Copepods and euphausiids dominated the mesozooplankton throughout the study area with small copepods (Oithona spp., Ctenocalanus spp. and Metridia spp.) particularly abundant.

Mesozooplankton community structure in the Scotia Sea during the CCAMLR 2000 survey: January–February 2000

Abstract An analysis of mesozooplankton community structure in the Scotia Sea was carried out, based on 123 RMT1 double oblique hauls (0–200 m) taken during the CCAMLR 2000 Survey. Standardized sample data (log abundance per 1000 m 3 ) were grouped into taxonomic categories and subjected to cluster analysis and multi-dimensional scaling. Two ordinations were performed, the first based on a reduced taxonomic dataset (31 categories out of a full 120) obtained by pooling ontogenetic stages within species and by including only those taxa that contributed at least 4% to total abundance at any one station. This disclosed two major station groups, which separated north and south, forming ‘warm’ and ‘cold’ water communities respectively, whereas four minor groups were mainly associated with stations around the Antarctic Peninsula and within the Weddell Scotia Confluence. Mean zooplankton abundance (238 000 individuals per 1000 m 3 ) within the northerly group G1 was up to 12 times higher than in other groups. The second ordination using all taxonomic categories disclosed an additional intermediate group (G1a), which was geographically consistent with the southern part of the northern group 1 from the previous ordination. However, because of taxonomic similarities between all the major station groups it was concluded that they represented a single community, which differed only in its phenological development and the mass occurrence of patchily distributed organisms such as krill larvae. Testing the relationships of station groups with the position of water masses and frontal boundaries indicated that the Weddell Front was broadly coincident with the boundary of the northern and southern communities over much of its length. However, the presence of stations belonging to group G2, to the north of the Weddell Front, to the west of the Antarctic Peninsula, and around the South Sandwich Islands, was consistent with the distribution of ice-influenced surface water. Low zooplankton abundance and species developmental composition suggested that this ‘community’ was largely in an over-wintered state. Copepods and euphausiids dominated the mesozooplankton throughout the study area with small copepods ( Oithona spp., Ctenocalanus spp. and Metridia spp.) particularly abundant.

The Azores Front since the Last Glacial Maximum

The spatial distribution of warm surface water in the Atlantic Ocean reflects the state of the thermohaline circulation. The Azores Current/Front, which is a recirculation of the Gulf Stream, marks the northeastern boundary of the North Atlantic subtropical gyre. Its position is therefore diagnostic of the width of the Atlantic warm water sphere. Here we report high resolution stable isotope and faunal abundance records of planktonic foraminifera in a sediment core from the Gulf of Cadiz (southwest Spain) which reflects shifting of the Azores Front since the Last Glacial Maximum (LGM). Today, the Azores Front does not penetrate into the Gulf of Cadiz, even though the front resides at the same latitude as the Gulf of Cadiz in the Atlantic. Our results indicate that the Azores Front is a robust feature of the Atlantic surface circulation, and that is present both in interglacial times and during the LGM at roughly the same latitude. However, during the LGM prior to 16 ka BP and during the Younger Dryas, the Azores Front did penetrate eastward into the Gulf of Cadiz.

The Azores Front since the Last Glacial Maximum

The spatial distribution of warm surface water in the Atlantic Ocean reflects the state of the thermohaline circulation. The Azores Current/Front, which is a recirculation of the Gulf Stream, marks the northeastern boundary of the North Atlantic subtropical gyre. Its position is therefore diagnostic of the width of the Atlantic warm water sphere. Here we report high resolution stable isotope and faunal abundance records of planktonic foraminifera in a sediment core from the Gulf of Cadiz (southwest Spain) which reflects shifting of the Azores Front since the Last Glacial Maximum (LGM). Today, the Azores Front does not penetrate into the Gulf of Cadiz, even though the front resides at the same latitude as the Gulf of Cadiz in the Atlantic. Our results indicate that the Azores Front is a robust feature of the Atlantic surface circulation, and that is present both in interglacial times and during the LGM at roughly the same latitude. However, during the LGM prior to 16 ka BP and during the Younger Dryas, the Azores Front did penetrate eastward into the Gulf of Cadiz.

Fate of Brine Applied to Unpaved Roads at a Radioactive Waste Subsurface Disposal Area

Between 1984 and 1993, MgCl2 brine was used to suppress dust on unpaved roads at a radioactive waste subsurface disposal area. Because Cl− might enhance corrosion of buried metals in the waste, we investigated the distribution and fate of Cl− in the vadose zone using pore water samples collected from suction lysimeters and soluble salt concentrations extracted from sediment samples. The Cl/Br mass ratio and the total dissolved Cl− concentration of pore water show that brine contamination occurs primarily within 13 m of treated roads, but can extend as much as 30 m laterally in near-surface sedimentary deposits. Within the deep vadose zone, which consists of interlayered basalt lava flows and sedimentary interbeds, brine has moved up to 110 m laterally. This lateral migration suggests formation of perched water and horizontal transport during periods of high recharge. In a few locations, brine migrated to depths of 67 m within 3 to 5 yr. Elevated Cl− concentrations were found to depths of 2 m in roadbed material. In drainage ditches along roads, where runoff accumulates and recharge of surface water is high, Cl− was flushed from the sediments in 3 to 4 yr. In areas of lower recharge, Cl− remained in the sediments after 5 yr. Vertical brine movement is directly related to surface recharge through sediments. The distribution of Cl− in pore water and sediments is consistent with estimates of vadose zone residence times and spatial distribution of surface water recharge from other investigations at the subsurface disposal area.

Fate of Brine Applied to Unpaved Roads at a Radioactive Waste Subsurface Disposal Area

Between 1984 and 1993, MgCl2 brine was used to suppress dust on unpaved roads at a radioactive waste subsurface disposal area. Because Cl− might enhance corrosion of buried metals in the waste, we investigated the distribution and fate of Cl− in the vadose zone using pore water samples collected from suction lysimeters and soluble salt concentrations extracted from sediment samples. The Cl/Br mass ratio and the total dissolved Cl− concentration of pore water show that brine contamination occurs primarily within 13 m of treated roads, but can extend as much as 30 m laterally in near‐surface sedimentary deposits. Within the deep vadose zone, which consists of interlayered basalt lava flows and sedimentary interbeds, brine has moved up to 110 m laterally. This lateral migration suggests formation of perched water and horizontal transport during periods of high recharge. In a few locations, brine migrated to depths of 67 m within 3 to 5 yr. Elevated Cl− concentrations were found to depths of 2 m in roadbed material. In drainage ditches along roads, where runoff accumulates and recharge of surface water is high, Cl− was flushed from the sediments in 3 to 4 yr. In areas of lower recharge, Cl− remained in the sediments after 5 yr. Vertical brine movement is directly related to surface recharge through sediments. The distribution of Cl− in pore water and sediments is consistent with estimates of vadose zone residence times and spatial distribution of surface water recharge from other investigations at the subsurface disposal area.

Ultraplankton distribution in surface waters of the Mozambique Channel-flow cytometry and satellite imagery

The composition of ultraplankton (UP) in near-surface samples collected underway every 1 to 6 h from a ship sailing from Durban to the Seychelles was determined by flow cytometry, using both autofluorescence pigments and fluorescence DNA staining. Prochlorococcus (Pro) (17 to 160 x 103 cells ml-1) numerically dominated the ultraphytoplankton (UPP), followed by Synechococcus (Syn) (4.5 to 57 x 103 cells ml-1) and eukaryotic algae (EA) (0.6 to 4.2 x 103 cells ml-1). The abundance of heterotrophic bacterioplankton (HB) was 0.4 to 1.3 x 106 cells ml-1. A strong correlation (r = 0.8 to 0.97) was observed between sea-viewing wide field of view sensor (SeaWiFS) satellite estimates of total chlorophyll a (chl a) concentration and chl a concentration, abundance and biomass of EA as well as abundance and biomass of HB. This shows the potential for deducing spatial distributions of these 2 groups for ecosystem modelling using satellite data. Although the correlation between satellite chl a estimates and Syn chl a concentration was strong (r = 0.83 to 0.88), the correlation with its abundance and biomass was poor (r < 0.6) due to high variability (factor of 12) in cellular chl a content and to a lesser extent to diurnal cycles. The relationships were similar when either only daytime or all UP measurements were compared with the satellite data. No relationship was found between satellite data and Pro chl a concentration, abundance or biomass, even after correction for a pronounced diel cycle, suggesting that the SeaWiFS instrument might not detect Pro chl a.

Ligand exchange rate of metal-NOM complexes by EDTA.

Metal complexation by natural ligands is important for metal transport and distribution in surface and ground water. The goal of the work was to study the ligand exchange rate for two important metal ions in natural aquatic systems (Al, Fe) was determined using EDTA and natural organic matter (NOM) of humic type as ligands. After adding EDTA to a solution containing metal-NOM complexes, these complexes dissociated and metal-EDTA complexes were formed. Metal-NOM complexes were separated from metal-EDTA complexes with the help of size-exclusion chromatography and detected by on-line inductively coupled plasma-mass spectrometry (ICP-MS). Injecting the samples into the system over time after addition of EDTA allowed us to measure the rate of the exchange of NOM by EDTA. The experiments could be well described with a first-order rate law assuming that the dissociation of the metal-NOM complexes is the rate-determining step. The exchange rate of Fe was found to be faster than that of Al. This corresponds well with the exchange rate of water molecules from the coordination sphere of the metal ions, which is also faster for Fe than for Al. Furthermore, the UV and the fluorescence signal of the chromatograms were measured. The results indicate that no disaggregation of NOM molecules took place, although about 75-85% of the aggregate-forming metal ions exchanged NOM by EDTA in their coordination sphere. This suggests clearly the fundamental role of NOM in colloidal transport of metals and in their bioavailability.

Water and energy linkages for groundwater exploitation: a case study of Gujarat State, India

Water and energy, two important resources for human development, have inextricable interlinkages between them. Their complementarity, a blessing otherwise, causes a vicious cycle in a complex situation like the present case study of Gujarat State, India. This paper analyses the demand-supply situation of both sectors for a State that is primarily agrarian but also with a high industrial growth rate. Due to inequitable distribution of surface water, recurrent droughts and ever increasing demand trend, groundwater (a major source in the State) has been overexploited in many parts, leading to 'water mining' with worsening water quality. With more than 40% energy consumed for extracting groundwater, this has had a serious impact on the energy balance. The paper discusses the energy requirements to satisfy the water needs and the water requirements for generation of energy. Finally, the feasible options available to meet the crisis, ranging from development of mega projects like Sardar Sarovar and Kalpasar to micro water harvesting structures, water pricing, consumer training etc., are reviewed.

Water and Energy Linkages for Groundwater Exploitation: A Case Study of Gujarat State, India

Water and energy, two important resources for human development, have inextricable inter-linkages between them. Their complementarity, a blessing otherwise, causes a vicious circle in a complex situation like the present case study of Gujarat state, India. This paper analyses the supply-demand situation of both sectors for a state that is primarily agrarian but also with a high industrial growth rate. Due to inequitable distribution of surface water, recurrent droughts and an ever-increasing demand trend, groundwater (a major source in the state) has been over-exploited in many parts, leading to 'water mining' with worsening water quality. With more than 40% energy consumed for extracting groundwater, this has had a serious impact on the energy balance. The paper brings forth the energy requirements to satisfy the water needs and the water requirements for the generation of energy. Finally, the feasible options available to meet the crisis, ranging from the development of mega projects like Sardar Sarovar and Kalpasar to micro water harvesting structures, water pricing and consumer training, etc., are reviewed.

DOC dynamics in the northwestern Mediterranean Sea (DYFAMED site)

Abstract Dissolved organic carbon (DOC) distribution and dynamics are investigated at the DYFAMED site (central Ligurian Sea, NW Mediterranean) in relation to hydrological and biological contexts, using a 4-year time-series dataset (1991–1994). The DYFAMED site is regarded as a one-dimensional station where simple hydrological mechanisms prevail and where the ecosystem is quite well understood. An average vertical profile of DOC concentration ([DOC]) indicates that maximal concentrations and variability are concentrated in the surface layers. For depths >800 m, the annual variations are on average similar to the analytical standard deviation (∼2 μM). The “composite” [DOC] distribution (average distribution over a typical year, integrating about 40 monthly profiles) for surface waters (0–200 m) is closely related to hydrological and phytoplanktonic forcings. It exhibits summer DOC accumulation in surface waters, due to spring–summer stratification and successive phytoplanktonic events such as spring and summer blooms, and winter DOC removal to deeper waters, due to intense vertical mixing. The analysis of vertical [DOC] gradient at 100-m depth as a function of the integrated DOC content in the 0–100-m layer makes it possible to objectively distinguish three specific periods: the winter vertical mixing period, the period of stratification and spring phytoplankton bloom, and the period of stratification re-inforcement and summer–fall phytoplankton bloom. We recalculate the vertical DOC fluxes to deep waters using a larger original dataset, after the first direct calculation (Deep-Sea Res. 40 (10) (1993) 1963, 1972) that was reproduced for other oceanic areas. The seasonal variations of the “composite” [DOC] distribution in surface waters are significantly correlated to the apparent oxygen utilization distribution, but the biogeochemical significance of such a correlation is still under examination. The global significance of our local findings is presented and the role of the oceanic DOC in the global carbon cycle is emphasized, especially with respect to several current issues, such as the oceanic “missing sink” and the equivalence between new production and exported production.

Surface water distribution of pico- and nanophytoplankton in relation to two distinctive water masses in the North Water, northern Baffin Bay, during fall

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 23:205-212 (2001) - doi:10.3354/ame023205 Surface water distribution of pico- and nanophytoplankton in relation to two distinctive water masses in the North Water, northern Baffin Bay, during fall Behzad Mostajir1,*, Michel Gosselin1, Yves Gratton2, Beatrice Booth3, Christophe Vasseur1, Marie-Ève Garneau1, Éric Fouilland1, Francesca Vidussi1, Serge Demers1 1Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 2Institut National de la Recherche Scientifique (INRS-Eau), 2800 rue Einstein, CP 7500, Sainte-Foy, Québec G1V 4C7, Canada 3School of Oceanography, University of Washington, Seattle, Washington 98195, USA *Present address: CNRS, ERS 2011 ŒEcosystèmes Lagunaires¹, Université Montpellier II, CP 093, Place E. Bataillon, 34095 Montpellier Cedex 5, France. E-mail: bmostajir@crit.univ-montp2.fr ABSTRACT: Distribution of pico- and nanophytoplankton in surface waters was investigated in relation to environmental factors at 10 stations in the North Water (NOW), northern Baffin Bay, and at 4 more southerly stations in Baffin Bay in fall 1999. Water temperature (T), salinity (S), dissolved inorganic nitrogen (DIN), phosphate concentrations and pico- and nanophytoplankton abundances were measured in the surface waters in the studied area. A clustering analysis was performed on these data and allows 2 major ecological regions to be distinguished. An eastern region was characterized by warmer, more saline, surface waters (T > -0.04°C, 31.1 < S < 32.7) where the picophytoplankton (eukaryotic flagellates, prasinophyte) were more abundant (700 to 4000 cells ml-1). The distribution of picophytoplankton in the NOW was directly correlated with the surface water T and S. Another region, the northwestern, was characterized by colder, less saline, surface waters (T < -1.2°C, 29.3<S<31.0), can be divided into northern and western sub-regions. Nanophytoplankton (mostly diatoms) were more abundant (>3000 cells ml-1) in the northern sub-region and their distributions followed the change in DIN concentrations. DIN and phosphate concentrations were higher in the northern sub-region than in the eastern region and the western sub-region, although DIN and phosphate concentrations were low in the NOW, with values ranging from 0.1 to 1.0 and 0.09 to 0.69 μM, respectively. Based on these ecological results, it is hypothesized that a surface current flows northward along the western coast of Greenland in fall, bringing warm, more saline water to the eastern part of the NOW. In contrast, surface Arctic water (colder, less saline) coming from the Kane Basin flows southward along the western part of the NOW. These 2 distinct water masses, with their different physical and chemical characteristics, govern pico- and nanophytoplankton distributions in the NOW during the fall. KEY WORDS: Picophytoplankton·Nanophytoplankton·Arctic· Polynya · Water temperature · Dissolved inorganic nitrogen Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 23, No. 2. Online publication date: January 31, 2001 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2001 Inter-Research.

The role of dust deposition in determining surface water distributions of Al and Fe in the South West Atlantic

Abstract Underway dissolved Al and Fe determinations were made on surface-water samples collected between 34°S and 8°N in the southern and tropical Atlantic Ocean using a towed surface-water sampler. The general distribution of dissolved Al, which ranged from ∼8 nM in the sub-tropical gyre to ∼61 nM under the Intertropical Convergence Zone (ITCZ) north of the Equator, corresponds clearly with atmospheric dust deposition patterns. A striking correlation between Al and surface-water salinities between 28°S and 8°N further indicates that wet deposition is the predominant mechanism of delivery of this atmospheric source. Iron concentrations, in contrast, were more uniform varying between 0.6 and 0.8 nM south of the equator. Highest Fe values (up to 1.4 nM) also were found associated with the maximum dust inputs at the ITCZ, indicating an atmospheric source for this element whose input appears to be limited by the solubility of Fe in sea water. The lowest Fe values (∼0.4 nM) also were observed in the equatorial region and are assumed to result from the biological removal of Fe from nutrient-rich water masses originating in the nearby equatorial and coastal upwelling regions. The high-frequency data acquisition of the towed sampler revealed significant variations (up to 50%) in both Al and Fe concentrations over short distances, most notably along the interface between the South Equatorial and Canary Currents. The high variability of a biologically important trace element such as Fe in these dynamic regions is indicative of the interplay between chemical and biological patchiness in surface waters.

Interpretation of Contrast in Tapping Mode AFM and Shear Force Microscopy. A Study of Nafion

The origin of phase contrast in tapping-mode atomic force microscopy has been investigated using two complementary scanning probe microscopy techniques, atomic force microscopy and shear force microscopy, which can be classified as a transverse dynamic force microscopy. The sample chosen for this study was Nafion, and specifically the membrane in different hydration states by virtue of its cation form. Differences in probe−sample adhesion throughout a sample, caused by an inhomogeneous distribution of surface water, were an important phase-contrast mechanism. A new variant in three-dimensional force imaging, phase-volume imaging has been a useful tool in the interpretation of phase contrast. With the use of transverse dynamic force microscopy, approach curves were obtained while the frequency spectrum around resonance was measured. This enabled the damping of the probe oscillation amplitude and the shift in its resonant frequency to be decoupled. Knowing the true oscillation amplitude of the probe, it was...

Drainage-basin-scale geomorphic analysis to determine reference conditions for ecologic restoration--Kissimmee River, Florida

Major controls on the retention, distribution, and discharge of surface water in the historic (precanal) Kissimmee drainage basin and river were investigated to determine reference conditions for ecosystem restoration. Precanal Kissimmee drainage-basin hydrology was largely controlled by landforms derived from relict, coastal ridge, lagoon, and shallow-shelf features; widespread carbonate solution depressions; and a poorly developed fluvial drainage network. Prior to channelization for flood control, the Kissimmee River was a very low gradient, moderately meandering river that flowed from Lake Kissimmee to Lake Okeechobee through the lower drainage basin. We infer that during normal wet seasons, river discharge rapidly exceeded Lake Okeechobee outflow capacity, and excess surface water backed up into the low-gradient Kissimmee River. This backwater effect induced bankfull and peak discharge early in the flood cycle and transformed the flood plain into a shallow aquatic system with both lacustrine and riverine characteristics. The large volumes of surface water retained in the lakes and wetlands of the upper basin maintained overbank flow conditions for several months after peak discharge. Analysis indicates that most of the geomorphic work on the channel and flood plain occurred during the frequently recurring extended periods of overbank discharge and that discharge volume may have been significant in determining channel dimensions. Comparison of hydrogeomorphic relationships with other river systems identified links between geomorphology and hydrology of the precanal Kissimmee River. However, drainage-basin and hydraulic geometry models derived solely from general populations of river systems may produce spurious reference conditions for restoration design criteria.

Calibrating airborne vegetation data for hydrological applications under dry conditions

Accurate spatial vegetation data are essential for hydrological modelling since vegetation processes directly influence biomass production and affect the distribution of surface water. Spatially distributed vegetation data are difficult and expensive to collect on the ground. Ground-collected data rarely provide complete spatial coverage at a single time. Remotely sensed data provide spatially extended maps of the surface cover in catchments, but require calibration. In this study, values of the airborne Normalized Difference Vegetation Index (NDVI), obtained with the Compact Airborne Spectrographic Imager (CASI), were calibrated with ground biomass samples in a 27km2 catchment consisting of 65% partially grazed pastures and grasses and 35% open and medium density woodland. Linear, quadratic and exponential regressions were applied to six waveband combinations of CASI NDVI and the best result was an exponential correlation of r2=0.62. This suggests that CASI NDVI has an exponential relationship with biomass. Calibration was affected by vegetation type and height, grazing, possible saturation of the near-infrared (NIR) bands and the narrow swathe width of aircraft data. Ground validation between Leaf Area Index (LAI) and biomass gave an r2=0.80. No statistically significant correlation was found between LAI and airborne NDVI. Significant fractions of non-green biomass at some sites, due to dry conditions, were seen as a contributing factor.