Increasing Water Hardness Research Articles

Adhesion of smooth and rough phenotypes of Flavobacterium psychrophilum to polystyrene surfaces

Phenotypic smooth cells of the fish pathogenic bacterium Flavobacterium psychrophilum have previously been reported to be more adhesive to polystyrene surfaces than corresponding rough cells. In this study, the adhesion ability of smooth and rough cells of F.psychrophilum to polystyrene surfaces was investigated in detail with a crystal violet staining method. By treating both polystyrene surfaces with fish mucus and carbohydrates and the bacterial cells with carbohydrates, the involvement of lectins in the adhesion process was investigated. Smooth cells showed significantly higher adhesion ability to untreated polystyrene surfaces compared with corresponding rough cells and increasing water hardness had an inhibitory effect on the adhesion. Treatment of polystyrene surfaces with D-glucose, D-galactose and fish mucus increased the adhesion ability of smooth cells to polystyrene. Furthermore, treatment of the smooth cells with D-glucose, D-galactose and sialic acid decreased the adhesion ability of the cells, indicating that the adhesion is likely mediated by complementary lectins on the surface of the cells. Sodium (meta)periodate treatment of smooth cells also decreased the adhesion ability to polystyrene, suggesting that the lectins, such as the dominating sialic acid-binding lectin, are probably localized in the extracellular polysaccharides surrounding the cells.

Effects of water hardness and pH on efficacy of chlorine-based sanitizers for inactivating Escherichia coli O157:H7 and Listeria monocytogenes

The effects of hardness and pH of water used to prepare electrolyzed oxidizing (EO) water and bleach solutions on the bactericidal activity of sanitizer prepared from the water were examined. EO water and bleach solutions were prepared with hard water of 0, 50, 100, and 200 mg/l as CaCO3 at pH 5, 6, 7, and 8. Increased water hardness tended to increase free chlorine and oxidation–reduction potential (ORP) and decrease pH of EO water. Chlorine levels also increased with water pH. Water hardness and pH only had minor effect on the pH of bleach solutions. Increasing hardness to 50 mg/l increased antimicrobial effect of EO water against Escherichia coli O157:H7, but reduced when water hardness further increased to 100 mg/l or higher. Water pH had no effect on EO water produced against E. coli O157:H7. Water hardness had no significant effect on bactericidal activity of EO water against Listeria monocytogenes but elevated water pH decreased bactericidal activity of EO water produced against L. monocytogenes. Bleach solution prepared using hard water at 200 mg/l or at pH 7 or higher had significant lower efficacy in inactivating E. coli O157:H7, but had no effect on the inactivation of L. monocytogenes. Results indicate that increasing the hardness or pH of water used to prepare EO water or bleach solutions will decrease the bactericidal activity of sanitizers prepared from the water.

Water hardness reduces the accumulation and toxicity of uranium in a freshwater macrophyte (Ceratophyllum demersum)

There is a lack of good quality data and mechanistic understanding on the effects of true water hardness (calcium (Ca) and magnesium (Mg)) on the bioavailability and toxicity of uranium (U) to freshwater biota. This study determined the effect of true water hardness (20, 75, 150, 275 and 400mgCaCO3L−1) on the cell surface binding affinity (log K), accumulation and toxicity (growth inhibition) of U in a submerged, rootless, macrophyte (Ceratophyllum demersum) in a synthetic freshwater with constant alkalinity (13mgCaCO3L−1) and pH (6.2) over 7days. A 20-fold increase in water hardness resulted in a 4-fold decrease in U toxicity (median effect concentration (EC50)=134μgL−1U at 20mgCaCO3L−1 hardness, increasing to 547μgL−1 U at 400mgCaCO3L−1 hardness), cell surface binding affinity (log K=6.25 at 20mg CaCO3L−1 hardness, decreasing to log K=5.64 at 400mgCaCO3L−1 hardness) and accumulation (the concentration factor decreased from 63 at 20mgCaCO3L−1 hardness to 15 at 400mgCaCO3L−1 hardness) of U. Calcium provided a 4-fold greater protective effect against U accumulation and toxicity compared to Mg. Speciation calculations indicated negligible differences in the percentages of key U species (UO22+, UO2OH+, UO2(OH)2) over the range of water hardness tested. The inhibition of U binding at the cell surface, and subsequent uptake, by C. demersum, with increasing Ca and/or Mg concentration, may be explained in terms of (i) competition between Ca2+/Mg2+ and UO22+ (and/or UO2OH+) for physiologically active sites at the cell surface, and/or (ii) reduced negative charge (electrical potential) at the cell surface, resulting in a decrease in the activity of UO22+ (and/or UO2OH+) at the plant/water interface (boundary layer), and consequently, less U bound to physiologically active cell surface sites. In the absence of a biotic ligand model for U, the results of this study (together with previous work) reinforce the need for a more flexible, hardness-dependent, U guideline for the protection of selected freshwater biota.

Effects of incubation water hardness and salinity on egg hatch and fry survival of Nile tilapiaOreochromis niloticus(Linnaeus)

This study examined the effects of water hardness and salinity on yolk sac larvae and swim-up fry survival of Nile tilapia, Oreochromis niloticus (Chitralada strain), eggs during artificial incubation. Four experiments were conducted to evaluate the effects of hardness, salinity and the sources of saline incubation water. High water hardness treatments (500–4200 mg L−1 as CaCO3) resulted in higher yolk sac larvae and swim-up fry survival than low water hardness treatments (50.0 and 132 mg L−1 as CaCO3); although yolk sac larvae and swim-up fry survival did not differ among the high or low hardness treatments. Salinity of 4.0 g L−1 using seawater, and 4.0 and 8.0 g L−1 using unprocessed common salt resulted in the higher survival rate of yolk sac larvae and swim-up fry than other salinity treatments. Yolk sac larvae and swim-up fry survival was found to decrease with the increase in salinity and increase with the increase in water hardness. The present study demonstrated the positive effects of increased water hardness level (>132 mg L−1) on yolk sac larvae and swim-up fry survival. The study also showed that seawater salinity of 4 g L−1 was the most appropriate salinity level for incubating Nile tilapia eggs.

Ecology of rare water plant communities in lakes of north-eastern Poland

Habitat studies were conducted on three rare plant communities dominated by <em>Nuphar pumila</em>, <em>Nymphaea candida </em>and <em>Hydrilla verticillata </em>in lakes of north-eastern Poland. The comparison of habitat properties of these three types of phytocoenoses with those of <em>Nuphar lutea </em>common in the area under study was also performed. It was demonstrated that the plant communities studied were ecologically distinct. The habitats of the phytocoenoses of <em>N. pumila </em>differed most significantly from those of the other phytocoenoses. They often inhabited softer waters poor in Mg<sup>2+</sup>, dissolved SiO<sub>2</sub>, but rich in total Fe, PO<sub>4</sub><sup>3−</sup>, NO<sub>3</sub><sup>−</sup>, and were associated with acidic substrates containing lower levels of Ca2+ and Na+, but greater amounts of total Fe and NO3−. The differences in the habitats of <em>H. verticillata </em>and <em>N. candida </em>phytocoenoses were most pronounced in the case of four properties of water: Na<sup>+</sup>, K<sup>+</sup>, Cl<sup>−</sup>, and Mg<sup>+</sup>. Their values were lower in waters of the <em>H. verticillata </em>phytocoenoses. The habitats of all the three types of rare phytocoenoses differed considerably from those of <em>N. lutea</em>. The most significant differences were found between the <em>N. lutea </em>and <em>N. pumila </em>phytocoenoses and the smallest differences were between the patches of <em>N. lutea </em>and <em>N. candida</em>. The properties of water were more important in differentiating the habitats of the phytocoenoses studied than the substrate properties. Due to alkalization and increase in water hardness in the lakes studied the stands of <em>N. pumila </em>are among the most threatened. The patches of <em>N. candida </em>and <em>H. verticillata</em>, which occur in waters with a wider range of hardness and tolerating a slight increase in trophy, can still continue to persist in the lakes for a long time.

Enterococci and their ability live out activity of sanitation detergents

We evaluated the effect of temperature decrease of sanitation solutions (35 °C) in condition of organic load (1% reconstituted powdered milk) and varying hardness of the water used for solution preparation (0 °, 15 °, 30 ° and 45 °) on the ability to randomly selected strains of enterococci survive exposure to acidic and alkaline sanitation solution (0.5% concentration, contact time 15 minutes) in model experiments. Increasing water hardness also increases the number surviving enterococci. Presence of organic loads and lower temperatures decreased the sanitation effect of the test solutions. The tested strains showed different tolerances to applied sanitation solutions. We found a weaker powerful of acid sanitation solution on base phosphoric acid after its application.https://doi.org/ 10.5219/166

Effect of dietary fluoride derived from Antarctic krill (Euphausia superba) meal on growth of yellowtail (Seriola quinqueradiata)

Yellowtail (Seriola quinqueradiata) is the most important cultured marine fish in Japan. Dietary fish meal for yellowtail in aquaculture was replaced with 0.0%, 15.4% and 100.0% Antarctic krill meal (KM0, KM15, and KM100) and with 0.0%, 15.4%, and 100.0% low-fluoride krill meal (LFK0, LFK15 and LFK100). The fish was fed to duplicate fish groups for 92d (KM trial) or 75d (LFK trial), and fish growth was monitored.Dietary fluoride (F−) concentrations (mgkg−1) were 110, 160, and 580 (KM0, KM15, and KM100, respectively) and 98, 120, and 190 (LFK0, LFK15, and LFK100, respectively). The growth during the experimental period, weight gain, feed intake, specific growth rate, and feed efficiency in fish fed the KM100 diet were markedly lower than the other experimental groups, which showed no marked differences in growth performance.After the experiment, dorsal muscle fluoride concentrations in each group were below the detectable limit (1mgkg−1), but vertebral bone fluoride concentrations increased with increasing proportion of KM to 655 (KM0), 870 (KM15), and 2150 (KM100) mgkg−1. With increasing LFK in the feed, vertebral bone fluoride concentrations (mgkg−1) increased slightly from 500 (LFK0) to 655 (LFK15), and 695 (LFK100). No histopathological changes were detected in the liver tissue in any experimental group.It has been reported that the fluoride bioavailability was reduced with increasing water hardness, however, the dietary fluoride derived from KM exoskeleton accumulates in vertebral bones of marine fish with growth inhibition, as has already been shown for freshwater fish. Vertebral bone fluoride concentrations in two krill-eating Antarctic marine fish in the wild were 33000mgkg−1 (Champsocephalus gunnari) and 15000mgkg−1 (Notothenia rossii), but they did not show any adverse effect of growth. Therefore, fish bone fluoride accumulation apparently depends on fish species rather than the salinity of the habitat. Consequently, krill exoskeleton must be removed during the processing of Antarctic krill if indeed these krill are to be used as fish feed. However, LFK can completely replace dietary fish meal without apparent adverse effects.

Effect of Holding and Packing Conditions on Hemolymph Parameters of Freshwater Prawns, Macrobrachium rosenbergii, during Simulated Waterless Transport

Preliminary market research has identified an unfulfilled market potential for live freshwater prawn, Macrobrachium rosenbergii, in urban areas of the USA and Canada. Truck transport is effective but requires shipment of large numbers of prawns to be economically feasible. Most retail markets are ill‐equipped to hold large quantities for subsequent live sales. Air‐freight of smaller quantities has potential but water weight limits its application. Shipping of live aquatic animals in waterless environments has been reported for some finfish and crustaceans. This project utilized biochemical characteristics of prawn hemolymph as measures of sublethal stress during simulated transport. Six trials were conducted to evaluate the effects of different variables involving preshipment holding conditions, acclimation prior to shipping, and conditions inside the shipping container. Trial 1 compared animals shipped in water with those in a non‐aqueous environment. Trial 2 compared three chilling rates (slow chill, fast chill, and no chill). Trial 3 evaluated different holding protocols including fed versus unfed, reduced pH, increased water hardness, and salinity. Trial 4 evaluated the addition of ammonia scavengers to the transport containers. Trial 5 evaluated the use of carbon dioxide scavengers and an anesthetic, AQUI‐S®. Trial 6 used the best results of Trials 2–5 in a combination of “Best Management Practices” (BMP) over extended time periods. Treatments had either three or four replications using Styrofoam boxes, each packed with six individually tagged prawns. Presoaked wood‐shavings and ice packs were used to keep the boxes moist and cool. The boxes were then sealed in individual oxygenated plastic bags. Trials 1–5 were conducted for 16 h and Trial 6 had separate boxes which were opened at 16, 24, and 32 h. Baseline hemolymph samples were taken prior to packing and from prawn alive at the end of all trials. Hemolymph variables included pH, pO2, pCO2, HCO3, tCO2, calcium, ammonia, osmolality, glucose, lactate, total protein, magnesium, calcium, and potassium. Percent survival and weight loss were also measured. Results of Trial 1 indicated that compared to transport in water, non‐aqueous environment significantly increased (P≤ 0.05) hemolymph levels of CO2 and ammonia, and significantly reduced levels of oxygen. In Trial 2, survival in the Slow Chill treatment was significantly higher than in the No Chill treatment, although hemolymph characteristics were not impacted. In Trial 3 prawns held in tanks with added salt (17 ppt) had the highest survival and lowest hemolymph concentration of ammonia and partial pressure of CO2. The ammonia scavengers in Trial 4 had no significant impact on survival or hemolymph variables. The CO2 scavengers and anesthetic in Trial 5 had no statistically significant impact on survival. The BMP of Trial 6 consisted of, in the following order, holding in 17 ppt marine salt mix, slow chilling, anesthetic (AQUI‐S) dip, and adding limewater (Ca(OH)2 + H2O) to the shipping box as a CO2 scavenger. In Trial 6, after 32 h of simulated “waterless” transport, prawns in the BMP treatment had significantly higher survival (96%) than prawns in the Control treatment (58%). The BMP prawns also had significantly higher partial pressures of oxygen and lower partial pressures of CO2 in the hemolymph.

Assessment of Pollution Potential of Cyanide-Bearing Tailings Dam

This study ascertained the types of chemical species that are formed in tailings material of gold leaching plants and assessed their short and long term pollution potential capabilities. The results revealed that chemical, biochemical and geochemical reactions were occurring in the tailings material; producing complexed cyanides, bicarbonates and nitrates which accumulate with depth in the tailings material while ammonium, carbonate and sulphate ions decreased with depth. Heavy metal accumulation particularly Mn, Pb, Zn Cu, Fe were also observed to increase with depth. It was concluded that the cyanide bearing tailings material has short term pollution potential of free cyanides, ammonium ions, sulphates ions and a long term risk of, complexed cyanide, nitrate and increase in water hardness due to bicarbonate ion. Heavy metal pollution and a decrease in pH are also possible.

Habitat differentiation of the Myriophyllum altemiflorum and Littorella uniflora phytocoenoses in Poland

The present study showed the ecological differentiation of phytocoenoses dominated either by <em>Myriophyllum alterniflorum</em> or by <em>Littorella uniflora</em>, which in Poland are classified within the Myriophylletum alterniflori or Myriophyllo-Littorelletum association. The properties which best differentiated the waters of the above types of phytocoenoses were calcium and factors associated with the carbonate complex (pH, electrolytic conductivity, total and carbonate hardness), and pH in the case of substrates. The most distinct differences in the habitats were found between the phytocoenoses dominated by <em>L. uniflora </em>from the Pomeranian <em>Lobelia </em>lakes and those dominated by <em>M. alterniflorum </em>from the Łęczna-Włodawa Lake District, in which other species from the Littorelletea uniflorae class were absent. The <em>L. uniflora </em>phytocoenoses are associated with soft waters poor in Ca<sup>2+</sup> and with the lowest values of pH, electrolytic conductivity, dissolved organic matter (COD-KMnO<sub>4</sub>) and dissolved SiO<sub>2</sub>. The substrates they inhabit are mineral and more acidic. By contrast, the values of the above-mentioned properties are considerably higher in the case of the phytocoenoses from the Łęczna-Włodawa Lake District. The habitats of the <em>M. alterniflorum </em>phytocoenoses from the Pomeranian <em>Lobelia </em>lakes occupy an intermediate position and are more similar to those of <em>M. alterniflorum </em>from the Łęczna-Włodawa Lake District. The results obtained in this study suggest that the phytocoenoses of <em>L. uniflora </em>and <em>M. alterniflorum </em>should not be included in the same association. Further studies are, therefore, necessary to resolve this problem. The comparative analysis of the present ecological findings and data obtained from other regions of Europe show that in Poland the phytocoenoses dominated either by <em>L. uniflora </em>or by <em>M. alterniflorum</em>, in which the contribution of Littorelletea uniflorae species is appreciable, are clearly associated with soft waters and their habitats are representative of the Littorelletea uniflorae class. The massive development of the phytocoenoses with both <em>L. uniflora </em>and <em>M. alterniflorum </em>in the <em>Lobelia </em>lakes is not always indicative of the increase in water hardness and euthrophication of waters typical of the communities of the Littorelletea uniflorae class. The <em>M. alterniflorum </em>dominated phytocoenoses without other Littorelletea species could be good indicators of the above processes taking place in such water ecosystems.

Effects of Water Hardness on Egg Hatchability and Larval Survival of Aquarium Fish, <I>Danio rerio</I>

Studies were conducted to determine the effects of water hardness on egg hatchability and larval survival of aquarium fish Danio rerio. The fertilized eggs were incubated at 27 °C at six levels of water hardness: 5, 32, 63, 127, 220 and 315 mg 1-1 CaCO3. Incubation period of eggs increased with increase in water hardness. The mean hatching rate was found increased in 5 to 63 mg 1-1 hardness. However, above the hardness of 63 mg 1-1 the mean hatching rate fluctuated. The larval survival rate of 12.62% was observed in 5 mg 1-1 hardness, which showed an increasing trend with increase in water hardness level up to 63 mg 1-1 CaCO3. However, survival rate decreased with hardness level beyond 63 mg 1-1. The results showed that larval survival was significantly influenced by water hardness. Very soft water (5 to 32 mg 1-1) and very hard water (315 mg 1-1 and above) were not found suitable for larval rearing. A water hardness of 63 mg 1-1 CaCO3 was thus found to be the suitable concentration for hatching and larval survival of D. rerio.

Influence of water hardness on acute toxicity of copper and zinc on fish

The aim of this study was to utilize static test for examining the acute toxicity of two essential elements, Cu and Zn, to a native fish, Capoeta fusca, by static bioassay. The acute toxicity of two heavy metals to C. fusca was determined in the soft, hard and very hard water (40, 150 and 380 mg/L as CaCO(3)). Results showed that toxicity of Cu and Zn decreased with increasing water hardness, so that water hardness had a significant effect on Cu and Zn toxicity on fish. Copper and Zn were more toxic in the soft water than in the hard water. The 96-hour lethal concentration for 50% (LC(50)) values for C. fusca were lower in the soft water compared with the hard and very hard water. The 96-hour LC(50) for Cu at the soft, hard and very hard water was found to be 1.1, 5.4 and 7.5 mg/L, respectively, while the 96-hour LC(50) for Zn at the soft, hard and very hard water was found to be 13.7, 74.4 and 102.9 mg/L, respectively.

Microemulsion Formation and Detergency with Oily Soil: V. Effects of Water Hardness and Builder

AbstractIn this study, the impact of water hardness and builder on the phase diagrams of motor oil microemulsions and the detergency of oil removal from a polyester/cotton blend was investigated. Water hardness and builder were found to have insignificant effects on the microemulsion phase diagram with motor oil. A mixed surfactant system of two parts C14–15(PO)3SO4Na, and 98 parts C12–14H25–29O(EO)5H of the total actives at 4% salinity was used to study the effect of water hardness and builders sodium tripolyphosphate (STPP) or ethylenediaminetetraacetic acid (EDTA) on detergency at 30 °C at a total active concentration of 0.3%. This formulation is in the Winsor Type III microemulsion regime. The microemulsion‐based formulation resulted in better detergency than a leading commercial liquid laundry detergent at all concentrations up to 0.5% actives. The microemulsion‐based formulation showed a plateau in detergency at >80% oil removal above 0.1% actives. The total oil removal decreased with increasing water hardness while the interfacial tension increased. When hard water was used in laundering, the total oil removal improved with increasing concentrations of STPP or EDTA up to stoichiometric levels, with STPP being slightly more effective than EDTA on a molar basis. Even high builder concentration could not improve hard water detergency to that of soft water. A significant fraction of oil removal occurred in the rinse steps vs. the wash step. Increasing water hardness reduced this fractional oil removal in the rinse steps, but it was still over half of total oil removal at 1,000 ppm water hardness.

A single bioavailability model can accurately predict Ni toxicity to green microalgae in soft and hard surface waters

The major research questions addressed in this study were (i) whether green microalgae living in soft water (operationally defined water hardness <10 mg CaCO 3/L) are intrinsically more sensitive to Ni than green microalgae living in hard water (operationally defined water hardness >25 mg CaCO 3/L), and (ii) whether a single bioavailability model can be used to predict the effect of water hardness on the toxicity of Ni to green microalgae in both soft and hard water. Algal growth inhibition tests were conducted with clones of 10 different species collected in soft and hard water lakes in Sweden. Soft water algae were tested in a ‘soft’ and a ‘moderately hard’ test medium (nominal water hardness = 6.25 and 16.3 mg CaCO 3/L, respectively), whereas hard water algae were tested in a ‘moderately hard’ and a ‘hard’ test medium (nominal water hardness = 16.3 and 43.4 mg CaCO 3/L, respectively). The results from the growth inhibition tests in the ‘moderately hard’ test medium revealed no significant sensitivity differences between the soft and the hard water algae used in this study. Increasing water hardness significantly reduced Ni toxicity to both soft and hard water algae. Because it has previously been demonstrated that Ca does not significantly protect the unicellular green alga Pseudokirchneriella subcapitata against Ni toxicity, it was assumed that the protective effect of water hardness can be ascribed to Mg alone. The log K MgBL (= 5.5) was calculated to be identical for the soft and the hard water algae used in this study. A single bioavailability model can therefore be used to predict Ni toxicity to green microalgae in soft and hard surface waters as a function of water hardness.

Hydrochemical variation in the springs water between Jerusalem–Ramallah Mountains and Jericho Fault, Palestine

The spatial and temporal changes of the composition of the groundwater from the springs along the Wadi Qilt stream running from the Jerusalem–Ramallah Mountains towards the Jericho Plain is studied during the hydrological year 2006/2007. The residence time and the intensity of recharge play an important role in controlling the chemical composition of spring water which mainly depends on distance from the main recharge area. A very important factor is the oxidation of organics derived from sewage and garbage resulting in variable dissolved CO2 and associated HCO3− concentration. High CO2 yields lower pH values and thus under-saturation with respect to calcite and dolomite. Low CO2 concentrations result in over-saturation. Only at the beginning and at the end of the rainy season calcite saturation is achieved. The degradation of dissolved organic matter is a major source for increasing water hardness. Besides dissolution of carbonates dissolved species such as nitrate, chloride, and sulfate are leached from soil and aquifer rocks together with only small amounts of Mg. Mg not only originates from carbonates but also from Mg–Cl waters are leached from aquifer rocks. Leaching of Mg–Cl brines is particularly high at the beginning of the winter season and lowest at its end. Two zones of recharge are distinguishable. Zone 1 represented by Ein Fara and Ein Qilt is fed directly through the infiltration of meteoric water and surface runoff from the mountains along the eastern mountain slopes with little groundwater residence time and high flow rate. The second zone is near the western border of Jericho at the foothills, which is mainly fed by the under-groundwater flow from the eastern slopes with low surface infiltration rate. This zone shows higher groundwater residence time and slower flow rate than zone 1. Groundwater residence time and the flow rate within the aquifer systems are controlled by the geological structure of the aquifer, the amount of active recharge to the aquifer, and the recharge mechanism. The results of this study may be useful in increasing the efficiency of freshwater exploitation in the region. Some precautions, however, should be taken in future plans of artificial recharge of the aquifers or surface-water harvesting in the Wadi. Because of evaporation and associated groundwater deterioration, the runoff water should be artificially infiltrated in zones of Wadis with high storage capacity of aquifers. Natural infiltration along the Wadis lead to evaporation losses and less quality of groundwater.

A multicentre randomized controlled trial of ion-exchange water softeners for the treatment of eczema in children: protocol for the Softened Water Eczema Trial (SWET) (ISRCTN: 71423189)

There is epidemiological evidence linking increased water hardness with increased eczema prevalence. A number of plausible mechanisms can be forwarded to suggest why hard water could exacerbate eczema. The most likely explanation is increased soap usage in hard water areas, the deposits of which can cause skin irritation in individuals with eczema. To assess the cost and cost-effectiveness of ion-exchange water softeners for the treatment of eczema in children. Three hundred and ten children aged 6 months to 16 years, with moderate to severe eczema. The children must live in hard water areas (>or= 200 mg L(-1) of calcium carbonate) and have a home that is suitable for the installation of a water softener. This is a single-blind, parallel-group, randomized controlled trial of 12 weeks duration followed by a 4-week cross-over period. RESULTS/ANALYSIS PLAN: difference in the mean change in disease severity (Six Area, Six Sign Atopic Dermatitis score) at 12 weeks compared with baseline. (i) proportion of time spent moving during the night; (ii) self-reported global changes in eczema severity; (iii) amount of topical treatment used; (iv) Patient Oriented Eczema Measure; (v) number of totally controlled and well controlled weeks; (vi) impact on health-related quality of life for the child (EQ-5D) and the family (Dermatitis Family Impact questionnaire); and (vii) cost-effectiveness. It is planned that recruitment will be completed by the end of 2008 and results will be available towards the end of 2009.

Sensitivity of the glochidia (larvae) of freshwater mussels to copper: Assessing the effect of water hardness and dissolved organic carbon on the sensitivity of endangered species

The assessment of the potential impact of waterborne contaminants on imperilled freshwater mussels is needed. Acute copper toxicity was assessed in a standardized soft water (hardness 40–48 mg CaCO 3 equivalents L −1) using the larvae (glochidia) from three common and six (Canadian) endangered mussel species. The resulting 24 h EC50s ranged from 7 to 36 μg Cu L −1, with the EC50s of two endangered species <10 μg Cu L −1. Acute copper sensitivity was also determined in Ptychobranchus fasciolaris, a species that employs conglutinates (packets of glochidia) in its reproductive strategy. Conglutinates were found to provide significant protection from acute copper exposure as the EC50 of the encased glochidia was more than four-fold higher than freed glochidia (72.6 μg Cu L −1 vs. 16.3 μg Cu L −1). The glochidia from two endangered species, Epioblasma triquetra and Lampsilis fasciola, were used to examine the influence of water hardness and dissolved organic carbon (DOC) on copper sensitivity. Exposures in moderately-hard water (165 mg CaCO 3 L −1) demonstrated that an increase in water hardness resulted in a significant reduction in copper sensitivity. For example, in L. fasciola the 24 h EC50s were 17.6 (14.2–22.6) μg Cu L −1 and 50.4 (43.5–60.0) μg Cu L −1 in soft water and moderately-hard water, respectively. The addition of DOC (as Aldrich Humic Acid) also resulted in a significant decrease in Cu sensitivity, such that a 10-fold increase in the EC50 of E. triquetra was observed when the reconstituted soft water was augmented with 1.6 mg DOC L −1. To determine if current water quality regulations for copper would protect all glochidia, the USEPA's Biotic Ligand Model (BLM) was used to derive water quality criteria for these exposures. While BLM-derived criteria for the soft water exposures indicate that protection would be marginal for the sensitive endangered species, the criteria derived for the DOC exposures suggest that the natural complexity of most natural waters in Southern Ontario (Canada) will provide glochidia with protection from acute copper exposure.

Chemosensory Deprivation in Juvenile Coho Salmon Exposed to Dissolved Copper under Varying Water Chemistry Conditions

Dissolved copper is an important nonpoint source pollutant in aquatic ecosystems worldwide. Copper is neurotoxic to fish and is specifically known to interfere with the normal function of the peripheral olfactory nervous system. However,the influence of water chemistry on the bioavailability and toxicity of copper to olfactory sensory neurons is not well understood. Here we used electrophysiological recordings from the olfactory epithelium of juvenile coho salmon (Oncorhynchus kisutch) to investigate the impacts of copper in freshwaters with different chemical properties. In low ionic strength artificial fresh water, a short-term (30 min) exposure to 20 microg/L dissolved copper reduced the olfactory response to a natural odorant (10(-5) M L-serine) by 82%. Increasing water hardness (0.2-1.6 mM Ca) or alkalinity (0.2-3.2 mM HCO3-) only slightly diminished the inhibitory effects of copper. Moreover, the loss of olfactory function was not affected by a change in pH from 8.6 to 7.6. By contrast, olfactory capacity was partially restored by increasing dissolved organic carbon (DOC; 0.1-6.0 mg/L). Given the range of natural water quality conditions in the western United States, water hardness and alkalinity are unlikelyto protect threatened or endangered salmon from the sensory neurotoxicity of copper. However, the olfactory toxicity of copper may be partially reduced in surface waters that have a high DOC content.

Release of elements to natural water from sediments of Lake Roosevelt, Washington, USA

Reservoir sediments from Lake Roosevelt (WA, USA) that were contaminated with smelter waste discharged into the Columbia River (BC, Canada) were examined using three measures of elemental release reflecting varying degrees of physical mixing and time scales. Aqueous concentrations of Cd, Cu, Pb, and Zn in the interstitial water of reservoir sediments, in the gently stirred overlying waters of incubated sediment cores, and in supernatants of aggressively tumbled slurries of reservoir sediments generally were higher than the concentrations from a reference site. When compared to chronic water-quality criteria, all three measures of release suggest that slag-contaminated sediments near the U.S.-Canadian border are potentially toxic as a result of Cu release and Pb release in two of the three measures. All three measures of Cd release suggest potential toxicity for one site farther down the reservoir, probably contaminated as a result of transport and adsorption of Cd from smelter liquid waste. Releases of Zn and As did not appear to be potentially toxic. Carbonate geochemistry indirectly affects the potential toxicity by increasing water hardness.

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) at multiple water hardnesses

Toxicity of cadmium to early life stages of brown trout (Salmo trutta) was determined at multiple water hardnesses. Increasing water hardness decreased cadmium toxicity. Postswimup fry were much more sensitive than embryos and larvae. Chronic values from early life stage tests initiated with eyed embryos were 3.52, 6.36, and 13.6 microg Cd/L at water hardnesses of 30.6, 71.3, and 149 mg/L, respectively. In tests initiated with 30-d postswimup fry, chronic values were 1.02, 1.83, and 6.54 microg Cd/L at water hardnesses of 29.2, 67.6, and 151 mg/L, respectively. Higher chronic values from the early life stage tests compared to tests initiated with swimup fry likely are caused by acclimation during cadmium-tolerant embryo and larval stages. Growth was not affected by cadmium in the early life stage tests but was negatively affected in tests initiated with fry at water hardnesses of 29.2 and 67.6 mg/L. Concentrations of cadmium that reduced growth were higher than those that increased mortality. Median lethal concentrations for swimup fry after 96 h were 1.23, 3.90, and 10.1 microg Cd/L at water hardnesses of 29.2, 67.6, and 151 mg/L, respectively. Test results enable prediction of acute mortality of brown trout swimup fry based on cadmium concentration and water hardness.