Water Chemical Conditions Research Articles

Effects of water chemistry on microfabric and micromechanical properties evolution of coastal sediment: A centrifugal model study

Water chemistry alteration induced strength weakening of natural sediment, which leads to the differential settlement of infrastructures in coastal areas, has caused numerous disasters and engineering failures. To thoroughly understand the underlying mechanisms of how water chemistry influences the microfabric and mechanical properties evolution of coastal sediments, herein, the authors adopted centrifuge test, X-ray diffraction (XRD), and atomic force microscope (AFM) to quantitatively study the structure anisotropy index (i.e., orientation index (OI)), micromorphological property (i.e., root mean square height (Sq)), and micromechanics (i.e., microscale apparent modulus) of clay sediments in different water chemistry conditions and gravity gradients. The results show that the change rule of OI is: OIsaline > OIalkaline > OIwater > OIacid, along the vertical sedimentary depth. Randomly distributed clay flocs and loose flocculated soil skeleton (mainly consisted by edge-to-face (EF) and edge-to-edge (EE) contact of the kaolinite platelets) are associated with the acidic water chemical conditions. The action of supergravity and face-to-face (FF) repulsive contact mode lead to high degree of anisotropy of kaolinite sediments in alkaline environment. Clay platelets are compacted closely under the synergetic effect of centrifugal pressure and prevailing van der Waals attraction (reduction of electric double layer repulsion) in saline environment. The change of 1/Sq is highly consistent with the change of OI at different depths in different water chemical environments. Along the sedimentary depth (i.e., transition from the normal gravity (1 g) to supergravity (8000 g)), the microscale apparent modulus of kaolinite sediment was found to be the highest in alkaline environment. As the water chemistry changes from alkaline to acidic, however, the microscale apparent modulus of kaolinite aggregate decreased, and it showed the smallest in the saline environment.

Uncertainty propagation in pore water chemical composition calculation using surrogate models

Performance assessment in deep geological nuclear waste repository systems necessitates an extended knowledge of the pore water chemical conditions prevailing in host-rock formations. In the last two decades, important progress has been made in the experimental characterization and thermodynamic modeling of pore water speciation, but the influence of experimental artifacts and uncertainties of thermodynamic input parameters are seldom evaluated. In this respect, we conducted an uncertainty propagation study in a reference geochemical model describing the pore water chemistry of the Callovian-Oxfordian clay formation. Nineteen model input parameters were perturbed, including those associated to experimental characterization (leached anions, exchanged cations, cation exchange selectivity coefficients) and those associated to generic thermodynamic databases (solubilities). A set of 13 quantities of interest were studied by the use of polynomial chaos expansions built non-intrusively with a least-squares forward stepwise regression approach. Training and validation sets of simulations were carried out using the geochemical speciation code PHREEQC. The statistical results explored the marginal distribution of each quantity of interest, their bivariate correlations as well as their global sensitivity indices. The influence of the assumed distributions for input parameters uncertainties was evaluated by considering two parametric domain sizes.

The Effects of Chemical Oxidation and High-Temperature Reduction on Surface Functional Groups and the Adsorption Performance of Biochar for Sulfamethoxazole Adsorption

Biochar is a beneficial adsorbent for the treatment of organic pollutants in the environment. The association of oxygen functional groups and adsorption behaviors has not been well investigated. In this paper, the oxidation-modified biochar (O-BC) and the reduction-modified biochar (R-BCX) were prepared by Co2+/peroxymonosulfate chemical oxidation and high-temperature reduction, respectively. The modified biochars were used to remove sulfamethoxazole (SMX) from water, and the adsorption amounts of biochar followed the order of R-BC700 (14.66 mg·L−1) > O-BC (4.91 mg·L−1) > BC (0.16 mg·L−1). Additionally, the effects of water chemical conditions (i.e., ionic strength, solution pH and humic acid (HA) concentration) on the adsorption of SMX on biochar, were further investigated. Combining physical adsorption, X-ray electron spectroscopy, and zeta potentiometer characterization techniques, the effect of functional groups on the adsorption mechanism was further explored, revealing the importance of various oxygen functional groups for SMX adsorption. The results showed that C=O and C=C, resulting in π–π interaction, were in favor of the adsorption of SMX, while C-O was not conducive to the adsorption of SMX, due to the steric hindrance and the negative surface charge. Additionally, the hydrophobic effect of the biochar was also one of the adsorption mechanisms.

Improving nanoplastic removal by coagulation: Impact mechanism of particle size and water chemical conditions

Plastic particles may bring potential threats to the ecosystem. Coagulation, as a widely used method to remove particles, has been rarely studied for plastic particles in the nanometer range. In this work, the coagulation removal of polystyrene nanoplastic particles (PSNPs, 50–1000 nm) was conducted in a model system containing coagulants aluminum chlorohydrate (PAC) and polyacrylamide (PAM). The optimal removal efficiency (98.5%) was observed in the coagulation process at pH= 8.0, 0.4 g·L−1 PAC and 20 mg·L−1 PAM. The inhibition impact of humic acid was also noticed, due to its competitive adsorption with PSNPs onto flocs. The interaction energies between PSNPs and PAC were calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, which showed that electrical neutralization resulted in the difference of the remove efficiency in different sizes and coagulant concentrations. The formation of Al-O bond between PSNPs and PAC/PAM flocs promoted the removal of PSNPs. Excessive PAM (> 20 mg·L−1) increased clusters size and solution viscosity, which resulted in the settling of clusters being controlled by buoyancy and the reduced remove efficiency. The findings suggest that the chemical coagulation dominants the removal of NPs, and the coagulation efficiency can be optimized by choosing suitable coagulant and water chemical conditions.

Efficient adsorption of europium (III) and uranium (VI) by titanate nanorings: Insights into radioactive metal species

Radioactive wastewater containing high concentration of radionuclides poses severe threats to ecosystem and human health, so efficient removal of these toxic heavy metals is urgently needed. Titanate nanomaterials have been demonstrated good adsorbents for heavy metals due to ion exchange property. In this study, titanate nanorings (TNRs) were synthesized using the facile hydrothermal-cooling method. The TNRs were composed of sodium trititanate, with a chemical formula of Na0.66H1.34Ti3O7•0.27H2O and a Na content of 2.38 mmol/g. The TNRs demonstrated sufficient adsorption performance to radionuclides europium (Eu) and uranium (U) ions. Specifically, even at a high initial concentration of 50 mg/L, 86.5% and 92.6% of the two metal ions can be rapidly adsorbed by the TNRs within 5 min, and equilibrium was reached within 60 min at pH 5. The maximum adsorption capacity (Qmax) obtained by the Langmuir isotherm model was 115.3 mg/g for Eu(III) and 282.5 mg/g for uranium U(VI) at pH 5, respectively. The adsorption capacities of the two metals under various water chemical conditions were highly related to their species. Ion exchange between metal cations and Na+ in the TNR interlayers was the dominant adsorption mechanism, and adsorption of U(VI) was more complicated because of the co-existence of various uranyl (UO22+) and uranyl-hydroxyl species. The spent TNRs were effectively regenerated through an acid-base or ethylenediamine tetraacetic acid (EDTA) treatment and reused. Considering the large adsorption capacity and quick kinetic, TNRs are promising materials to remove radionuclides in environmental purification applications, especially emergent treatment of leaked radionuclides.

Fabrication of novel 2D Ag-TiO2/γ-Al2O3/Chitosan nano-composite photocatalyst toward enhanced photocatalytic reduction of nitrate

The presence of excess nitrate in groundwater limits it use as a drinking water supply and its removal is critical to balance the nitrogen cycle in aquatic systems. In this study, ultra-thin 2-dimensional Ag-TiO2/γ-Al2O3/Chitosan (Ag-TiO2/Al2O3/CS) nano-composite was synthesized for the fast reduction of nitrate under UVA irradiation from aqueous solutions. As-synthesized nano-composite was well characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, Fourier-transform infrared spectroscopy and UV–vis diffuse reflectance spectroscopy. Experimental variables including pH, nitrate concentration, photocatalyst dose and contact time were considered to demonstrate their effect on the rate of nitrate reduction. Formic acid was used as a radical scavenger at optimal concentration of 2:1 (formic acid:nitrate). The results showed that upon UVA irradiation, the synthesized nano-composite exhibited fast nitrate reduction in broad pH range (about 74% removal at pH 11 in 5 min reaction time) in diverse water chemical conditions. The Ag-doped and hybrid heterostructures can effectively utilize UV–visible-light to remove nitrate and degrade formic acid. For the 3 cycles the photocatalyst efficiency remained same and after the third cycle, its efficacy decreased gradually. This work suggests 2D Ag-TiO2/Al2O3/CS nano-composite for the fast removal of nitrate in drinking water treatment.

Photocatalytic removal of hexavalent chromium by newly designed and highly reductive TiO2 nanocrystals

Hexavalent chromium Cr(VI), a highly toxic oxyanion, widely occurs in drinking water supplies. This study designed and synthesized a new type of highly reductive TiO2 nanocrystals for photochemical Cr(VI) removal, via the thermal hydrolysis of TiCl4 in the presence of diethylene glycol (DEG). Surface analyses and hydroxyl radical measurements suggested that DEG was chemically bonded on TiO2 surface that resulted in an internal hole-scavenging effect and a high electron-releasing capacity, making it advantageous to conventional TiO2 materials. Upon UV irradiation, the synthesized TiO2 photocatalyst exhibited fast Cr(VI) reduction kinetics in diverse water chemical conditions. Fast elimination of Cr(VI) was achieved on a time scale of seconds in drinking water matrices. The removal of Cr(VI) by reductive TiO2 exhibited a three-stage kinetic behavior: an initial fast-reaction phase, a lag phase resulting from surface precipitation of Cr(OH)3(s), and a final reaction phase due to surface regeneration from oxidation-reduction induced ripening process. The lag phase disappeared in acidic conditions that prevented the formation of Cr(OH)3(s). The catalyst exhibited extremely high electron-releasing capacity that can be reused for multiple cycles of Cr(VI) removal in drinking water treatment.

The effects of wildfire on mercury and stable isotopes (δ(15)N, δ(13)C) in water and biota of small boreal, acidic lakes in southern Norway.

Effects of wildfire on main water chemistry and mercury (Hg) in water and biota were studied during the first 4 post-fire years. After severe water chemical conditions during hydrological events a few months following the wildfire, the major water chemical parameters were close to pre-fire conditions 4 years after the fire. Concentrations of total Hg and methyl Hg in the surface water 4 years after the fire ranged between 1.17-2.63 ng L(-1) and 0.053-0.188 ng L(-1), respectively. Both variables were positive and strongly correlated with total organic carbon (TOC), TOC-related variables (color, UV absorbance), total phosphorous, and total iron. In addition, MeHg was positively correlated with total nitrogen and chlorophyll-a. The concurrence of increased concentrations of nutrients and chlorophyll-a in the lakes, the more enriched δ(15)N-signatures and higher Hg levels in fish 2 years after the fire, might be a result of the wildfire. However, natural factors as year-to-year variations in thermocline depth and suboxic status in the lakes make it difficult to draw any strong conclusions about wildfire effects on Hg in the biota from our investigated lakes.

Dissolution Mitigation of Alloy 690 By Electrochemical Surface Modification

Metal oxide particles and metal ions are released from the inside surface of steam generator (SG) tubes in operating nuclear power plants. These corrosion products are transported into the core, forming a crud on fuel cladding. The composition of the fuel crud consists mainly of nickel ferrite, and it indicates that the primary source is the nickel element in SG tube materials. A higher crud buildup might cause an increase in radiation dose rate and axial offset anomaly (AOA). The metal ion release property is affected by water chemical conditions, and metal surface states such as the roughness and residual stress (work hardening). In this work, the metal surface modification technique for reducing the metal ion release is investigated using an electrochemical polishing method and is evaluated with micro hardening on the surface layer.The corrosion tests were performed using commercial alloy 690, which was heat processed by two steps, mill annealed, and thermal treated. The electro-polishing (EP) process was applied by ElectoMet® 4 (Buehler Co, IL). The specimen used a tube shape of 19.05 mm outside diameter, and was electro-polished on the inside surface. After the EP process, the surface morphology and roughness was investigated by field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM).The corrosion test environment simulated the primary water chemistry in PWRs. The temperature and pressure were maintained at 330oC and 150 bars during the experiments. The condition of the test solution was 2 ppm lithium (LiOH) and boron 1,200 ppm (H3BO4), 35 cc/kg (STP) dissolved hydrogen and 10 ppb dissolved oxygen.The metal ion release rate was evaluated using a gravimetric analysis method using a two-step alkaline permanganate-ammonium citrate (AP/AC) descaling process.The change in the surface morphologies of the corrosion products is not remarkable, while the release rate is lower by a factor of two when the surface was modified using the appropriate electrochemical polishing method. The metal ion release rate is mainly dependent on the surface roughness as the function of EP time and electrolyte composition. The specimen which had EP time for 8 minutes showed most improvement of metal ion release rate.

The effects of stream substratum composition on the emergence of salmonid fry

Sternecker K, Geist J. The effects of stream substratum composition on the emergence of salmonid fry. Ecology of Freshwater Fish 2010: 19: 537–544. © 2010 John Wiley & Sons A/SAbstract – Salmonid fishes are target species for the conservation of freshwater habitats, but their natural reproduction is often insufficient. The emergence of fry is a crucial phase in the life cycle of salmonids and the stream substratum is the key habitat which regulates the emergence success. In this study, brown trout (Salmo trutta) and Danube salmon (Hucho hucho) eggs were exposed to different sediment textures and the emergence and the postemergence survival and growth were observed under constant water chemical conditions in the laboratory. In both species, textural effects on emergence rate, chronology of emergence, survival rate after emergence and growth after emergence were detected. Fine‐textured substratum (5–8 mm) formed a physical barrier to the posthatch migration of salmonids from the interstitial zone to the open water. The time period between the first and the last emerged fish was shorter in treatments with fine texture compared with coarse substratum. The survival rate was higher in treatments of coarser sediment. The effects of different textures on the growth of fry after emergence differed between brown trout and Danube salmon, which can be explained by different life history strategies. These results suggest that physical characteristics of substratum texture can have strong effects on salmonid emergence, and ultimately on the persistence of salmonid populations. They also suggest that biodiversity conservation in stream ecosystems can greatly benefit from an inclusion of the physical characteristics of the stream bed into catchment‐based management plans.

Test and application of a general process-based dynamic coastal mass-balance model for contaminants using data for radionuclides in the Dnieper-Bug estuary

In this work a general, process-based mass-balance model for water contaminants for coastal areas at the ecosystem scale (CoastMab) is presented and for the first time tested for radionuclides. The model is dynamic, based on ordinary differential equations and gives monthly predictions. Connected to the core model there is also a sub-model for contaminant concentrations in fish. CoastMab calculates sedimentation, resuspension, diffusion, mixing, burial and retention of the given contaminant. The model contains both general algorithms, which apply to all contaminants, and substance-specific parts (such as algorithms for the particulate fraction, diffusion, biouptake and biological half-life). CoastMab and the sub-model for fish are simple to apply in practice since all driving variables may be readily accessed from maps or regular monitoring programs. The separation between the surface-water layer and the deep-water layer is not done as in most traditional models from water temperature data but from sedimentological criteria. Previous versions of the models for phosphorus and suspended particulate matter (in the Baltic Sea) have been validated and shown to predict well. This work presents modifications of the model and tests using two tracers, radiocesium and radiostrontium (from the Chernobyl fallout) in the Dnieper-Bug estuary (the Black Sea). Good correlations are shown between modeled and empirical data, except for the month directly after the fallout. We have, e.g., shown that: 1. The conditions in the sea outside the bay are important for the concentrations of the substances in water, sediments and fish within the bay, 2. We have demonstrated “biological,” “chemical” and “water” dilution, 3. That the water chemical conditions in the bay influence biouptake and concentrations in fish of the radionuclides and 4. That the feeding behaviour of the coastal fish is very important for the biouptake of the radionuclides.

Turnover mechanisms of organic conformation on turbidity in drinking water

The turbidity variation in artificial water and samples from a water plant was investigated in the presence of organics with different relative molecular mass. The results show that recessive turbidity existed when water chemical conditions were changing. The formation of turbidity depended on organic relative molecular mass and their conformations on particles. At higher pH and lower ionic strength, the organic chains with a more extended conformation resulted in rising turbidity of the suspension. At lower pH, the reconformation of organics took place due to charge neutralization by the proton, resulting in a decline in turbidity. The addition of NaCl and MgCl2 at pH 7.00 also resulted in a decrease of turbidity in the suspension. It is believed that the occurrence of recessive turbidity has a significant influence on the stability of water supply quality.

SEASONAL VARIATIONS IN SEDIMENT AND BOTTOM WATER CHEMISTRY OF WESTERN LONG ISLAND SOUND: IMPLICATIONS FOR LOBSTER MORTALITY

In the fall of 1999 the lobster population of western Long Island Sound (WLIS) experienced a massive die-off (LoBue et al. 2003). In fact, the lobster populations in WLIS still have not recovered as of this writing (Benway et al. 2004). Factors suspected of playing roles in this mortality event include water temperature, hypoxia and a neoparameoba. The overall objective of this study is to obtain an understanding of bottom water chemical conditions in WLIS, and their potential influence on benthic community structure and lobster health. Beginning in May 2002, water samples were collected within 5.0 cm and at 1.0 m above the bottom at 12 selected stations in WLIS and analyzed for dissolved NH4, H2S and O2. Grab samples for benthic community determination and sediment-profile images were simultaneously obtained with the water samples at 6 of the 12 stations. The data collected provide an accurate field record of the apparent levels of dissolved oxygen in the sediments of western Long Island Sound, as reflected in apparent redox depths (as recorded in sediment-profile images) and the amount of ammonia, hydrogen sulfide and oxygen present in the bottom waters, over a period critical to the LIS lobster fishery. Levels of dissolved oxygen in actual (within 5 cm) bottom waters of WLIS remain low throughout the summer and fall, despite the increase in dissolved oxygen recorded in the fall in waters 1 m above the bottom. Dissolved sulfide and ammonia concentrations in bottom waters of WLIS increased during spring and fall. These chemicals have been shown by other researchers to be physiologic stressors on lobsters and other marine life that live within benthic environments (Knezovich et al. 1996, Lianso 1991, McMahon & Wilkens 1975, Shumway & Scott 1983, Theede et al. 1969, Vargo & Sastry 1978, Vismann 1990, Wang & Widdows 1991). Given that the lobster die-off of 1999 began in late summer to early fall, it is hypothesized that ammonia and sulfide released from the sediments during that time may have played a role in weakening the lobsters. A comparison of water quality and temperature data from this study with that collected by the CT DEP at certain stations in WLIS during 1999 revealed some similarities and further strengthens the argument that environmental stressors played a role in the lobster mortality event of 1999.

Association of Cryptosporidium parvum with Suspended Particles: Impact on Oocyst Sedimentation

The association of Cryptosporidium parvum oocysts with suspended particles can alter the oocysts' effective physical properties and influence their transport in aquatic systems. To assess this behavior, C. parvum oocysts were mixed with various suspended sediments under a variety of water chemical conditions, and the resulting settling of the oocysts was observed. Direct microscopic observations showed that oocysts attached to suspended sediments. Settling column and batch experiments demonstrated that oocysts are removed from suspension at a much higher rate when associated with sediments. The rate of oocyst sedimentation depended primarily on the type of sediment with which the oocysts were mixed. Changes in background water conditions had a relatively small impact on the extent of oocyst-particle association and the resulting oocyst deposition. We believe that the ubiquitous association of C. parvum oocysts with suspended particles enhances the sedimentation of oocysts in natural waters and that this interaction should generally be considered when predicting the migration of pathogens in the environment.

Element Concentrations and Enrichment Ratios in the Aquatic MossRhynchostegium riparioidesalong the River Iregua (La Rioja, Northern Spain)

The concentrations of seven elements (N, P, K, Ca, Mg, Fe, and Na), five of which are macroelements, were measured in 3-cm apices of 17 populations of the euryecious aquatic moss Rhynchostegium riparioides (Hedw.) Card. located along the course of the Iregua River (La Rioja, northern Spain). A principal components analysis (PCA) revealed two key factors ordinating the sampling sites on the basis of their physicochemical data 1) substrate lithology, since the river's upper course is predominantly siliceous whereas the middle and lower courses are influenced by CaCO3 and 2) human impact, especially observed in the irrigation channels of the lower course. The element concentrations in the tissues of R. riparioides, generally comparable to those cited for other aquatic bryophytes, were strongly and significantly correlated with the respective element concentrations in the surrounding water. Therefore, the PCA ordinating the moss populations on the basis of their element concentrations was highly coincident with the physicochemical PCA: the headwater populations had the lowest element concentrations, the middle course populations were notably Ca-enriched, and the lower course populations showed the highest concentrations of N, P, K and Na. The significant correlations between the element concentrations differentiated two groups of elements: mainly intracellular ones (N, P, and K), and mainly exchangeable ones (Ca and Mg). This dichotomy was also noticed in other respects 1) the relationship between the water and the tissue element concentrations was linear for N, P, and K, but similar to a Michaelis-Menten saturation-type curve in the case of Ca and Mg; 2) the quotients between the concentration of a given element in moss and in water (enrichment ratios, ER) were much higher for N, P, and K than for Ca and Mg; 3) only the tissue concentrations of Ca and Mg were correlated–negatively–with their respective ERs. Na showed somewhat peculiar characteristics, probably reflecting weak uptake efficiency and metabolic irrelevancy. ERs were strongly dependent on the respective element concentrations in water through hyperbolic relationships, suggesting that the uptake efficiency may be higher when elements are more diluted in water and decreases as the moss becomes saturated. This plasticity, to be expected in such an euryecious species as R. riparioides, would permit the acclimation of the different populations to changing water chemical conditions in order to avoid nutrient deficiencies.

Spatial differences in macroinvertebrate community structure in springs in southeastern Ontario in relation to their chemical and physical environments

This study examined the benthic macroinvertebrate communities of 20 springs in southeastern Ontario in relation to major water chemical variables and temperature. Significant differences were evident among the spring communities, and a TWINSPAN classification showed three major groups, which were associated with different levels of urbanization and water chemical conditions. Canonical correspondence analysis (CCA) ordinations indicated that the major environmental gradient was related to temperature and NH4 and to two springs adjacent to a landfill site. CCA ordination of a sub-data set excluding these latter two sites together with 3 closely related variables better illustrated the response of spring communities to different levels of urbanization. The strongest relationship to emerge was that between taxon occurrences and chloride, a major contaminant in groundwater in the study area and believed to be derived from road salt. Several taxa were closely associated with high chloride levels (e.g., Tipulidae and Ceratopogonidae), whereas others occurred only in springs with low chloride levels (e.g., Gammarus pseudolimnaeus and Turbellaria). The possibility of using spring macroinvertebrates as biological indicators of chloride contamination of groundwater is discussed.

CHEMICAL ANALYSIS OF CO2 REMOVAL IN TRAY AERATORS1

ABSTRACT: This paper presents a discussion of the chemistry of CO2 removal in tray aerators, and different sets of equations that are applicable to several initial water chemical conditions are proposed. These chemical equations and a statistical model to predict the kinetic constant were tested with field data observed by other researchers in pilot units and in a full scale plant. The water temperature in their experiments was around 15°C.

Monitoring fish stocks in relation to acidification in Norwegian watersheds

The Norwegian Monitoring Programme for Long-Range Transported Air Pollutants started in 1980. The biological part of this programme includes besides invertebrate studies in streams, (i) fish community status in lakes by means of interviews, test-fishing in lakes by using standard gill-net series, recruitment studies of brown trout in inland streams, and juvenile stock assess and monitoring of fish kills in salmon rivers. Damaged fish stocks are recognized within a land area of 51,500 km2 in southern Norway and 30 km2 in northern Norway. At least 6,000 lake-dwelling fish stocks have either been lost or are at various stages of reduction. Brown trout (Salmo trutta) is the most widespread and abundant species of fish in Norwegian watersheds, and is also most severe affected by acidification. More recently, there are some indications of an increase in the abundance of brown trout in some areas. However, analysis of age structure in lakes, and fry densities in streams in such areas revealed large annual variations in recruitment rate, which indicates unstable water chemical conditions. Atlantic salmon (Salmo salar) is virtually extinct in 25 rivers in southernmost, southwestern and western Norway.

Problems of chemical-analytical monitoring in nuclear power

Further increase of the reliability and efficiency of the operation of nuclear power plants depends on the comprehensive solution of many problems, of which the problem of optimization and increase of the informativeness of chemicotechnological monitoring is gaining in importance. There is a clear rift between the level of scientific ideas and technical solutions on which nuclear power plants are based and the existing approach to the organization of chemical monitoring. Everyone understands the necessity of chemical monitoring, but many people do not regard it as a necessary element for ensuring normal operation of a nuclear power plant. The lack of standard requirements and a standard methodical base markedly lowers the reliability of the results of analyses, and behind this lies possible breakdowns of the water-chemical conditions. How can this situation be explained? The consequences of deviations of water-chemical conditions from regulation standards are by no means manifested immediately. Apparent wellbeing at any given time creates the impression that the requirements of the chemical laws can be ignored with impunity. But there is also another reason for the disdainful attitude toward chemical monitoring. Chemical-technological monitoring at a nuclear power plant reduces to the determination of ~20 water-quality indicators for the basic and auxiliary systems. Considering the number of existing points at which samples are extracted in each block of a nuclear power plant and the frequency with which the analyses are performed, it is not difficult to imagine the impressive number of the overall volume of data obtained. Thus the total number of analyses per month for one block of a nuclear power plant with RBMK-1000 approaches 15,000 [i]. In addition, as a rule, these are single measurements, whose error it is virtually impossible to estimate exactly. Moreover, regardless of how conscientious the chemists-analysts at the technological laboratories are, in the monotony of repeating values it is difficult to escape big blunders in the case of unforeseen deviations of the parameters in the water-chemical conditions. Under these conditions there is no hope of obtaining reliable information for each of the measurements, making sense of the observational results, and drawing correct conclusions. We arrive at a p~r~dox, By increasing the number of parameters monitored and the number of points at which samples are extracted we strive to increase the information content of chemical monitoring, but we actually achieve the opposite result. At the present time, when nuclear power has transformed from a unique source of energy to one of the most important elements of the power production in the country, it is essential to reexamine the concepts forming the basis for the implementation of chemical-analytical monitoring at nuclear power plants. At the first nuclear power plants the research and technological functions of analytical monitoring were balanced, and preference was often given to obtaining research information. For serially produced nuclear power plants research programs are a rare episode. It is evident that the main reason for this situation is hidden in the existing standards and requirements imposed on the chemical monitoring system at nuclear power plants. At the first stages of development of nuclear power the striving toward performing as much analysis as possible and over the entire technolgocial loop was justified, whereas at the present time, as experience in operating nuclear power plants in this country and abroad shows, the time has come to search for new approaches to the problem of analytical monitoring of the quality of water heat carriers. The successful solution of the problem of analytical monitoring is often linked primarily with the instrumentation. But the number of methodical and instrumentation developments continues to increase, and the chemical-technological monitoring remains as before one of the laborious and unreliable elements in the overall chain of operational monitoring of nuclear power plants. Fundamental restructuring of the overall scheme of such monitoring is possible only based on automatic or, at least, automated means of chemical analysis.

The Role of Environmental Heterogeneity in the Regulation of Duck Populations

Behavioral spacing of breeding pairs and the availability of energy resources have been proposed as major factors that regulate duck populations. To compare the relative importance and interaction of the two mechanisms, the seasonal distribution of duck populations was determined in an edaphically heterogeneous system of beaver (Castor canadensis) ponds west of Ottawa, Ontario, near a boundary of the Ottawa-St. Lawrence Lowland and the Precambrian Shield. Ponds were selected in a number of geological substrates, so that within a relatively small geographical area a variety of water chemical conditions was represented. The seasonal production of submerged vegetation was a function of water hardness and formed the basis of the assumption that water chemistry could be employed quantitatively as a measure of pond fertility. Numbers of breeding pairs of ducks were dependent only on the amount of surface water available, indicating that the major population regulatory mechanism was behavioral spacing. Fledged ducks, on the other hand, selected fertile wetlands regardless of pond size, indicating that populations were regulated by the availability of energy resources. Habitat requirements of broods were intermediate, because both behavioral escape cover and food availability were important. It is postulated that the different environmental requirements of the three life history stages are an evolutionary adaptation to a temporarily unpredictable environment. The adaptations allow duck populations to maintain equilibrium in a temporarily unpredictable environment, and to attain high population size in a spatially heterogeneous environment. J. WILDL. MANAGE. 40(1):22-32 Behavioral spacing mechanisms and the availability of food resources are two factors considered to be of major significance in the regulation of duck populations (Evans and Black 1956, Moyle 1956, Hawkins 1964, Jahn and Hunt 1964:16, Dzubin 1969, Dzubin and Gollop 1972). Although there is a considerable body of knowledge concerning duck population dynamics and the regulatory effects of specific environmental factors, there is a lack of consensus on the relative importance, or relationships, of the various factors known to regulate population size. The question of what overall environmental factors regulate duck populations was asked repeatedly by contributors to the Saskatoon Wetlands Seminar published in 1969. In summarizing the seminar, Jahn (1969:177) stated that for progress to be made in waterfowl research Seasonal needs of the birds must be related to the physical, chemical and biotic features of the ecosystem. Recent developments in theoretical ecology have stressed the importance of the abiotic environment in determining many basic biotic properties (Loucks 1970, Sanders 1969, Slobodkin and Sanders 1969, Smith 1970, Wiegert and Owen 1971). Such fundamental biological phenomena as niche differentiation and mechanisms of population regulation may evolve in response to environmental characteristics. The theoretical evidence that mechanisms of ecosystem organization and population regulation can respond to environmental characteristics provided the conceptual basis for this study. Research emphasis was placed on determining environmental parameters that would quantitatively indicate the seasonal requirements of breeding ducks. To this end, a study area was selected that provided a continuum of wetlands ranging from biologically productive hardwater ponds to less productive soft water ponds, yet was small enough to avoid geographical influences on populations. The presence of numerous beaver ponds J. Wildl. Manage. 40 (1):1976 22 REGULATION OF DUCK POPULATIONS * Patterson overlying a variety of geological substrates provided a natural outdoor laboratory. Ponds of specific chemical regimes and sizes could be selected to provide the treatments necessary for field experiments to determine the environmental requirements of ducks. This work is from a Ph.D. thesis submitted to Carleton University. Financial support was provided by research contracts and graduate scholarships from the Canadian Wildlife Service and Ontario Graduate Fellowships. I thank L. P. Lefkovitch, Director, Statistical Research Service, Agriculture Canada, for performing the statistical analyses and A. T. Prince, Director, Inland Waters Branch, Environment Canada, whose laboratory conducted the water chemical analyses. E. Grinnell's hard work and enthusiasm as my field assistant are greatly appreciated. I also thank H. G. Merriam and J. D. H. Lambert, Department of Biology, Carleton University, and N. G. Perrett and H. Boyd, Canadian Wildlife Service, for advice during the study. H. G. Merriam, H. Boyd, L. P. Lefkovitch, and W. J. D. Stephen critically reviewed the