Water effect ratio

HMBC test is based on the U.S. EPA concept of Water Effect Ratio (WER), except that a bacterial response (MetPLATE) is used to determine metal bioavailability. Briefly, the methodology consists of spiking samples of both laboratory water (moderately hard water) and site water with a given metal and the mixtures are shaken for 60 min at 25°C. Afterwards, both mixtures are assayed for metal toxicity using MetPLATE. HMBC is determined as the ratio of IC50 of the metal in site water over IC50 of the metal in laboratory water. 

The U.S. EPA has proposed the concept of Water Effect Ratio (WER) to take into account the effect of the above mentioned factors on heavy metal bioavailability/toxicity in environmental samples (U.S. EPA, 1982, 1984, 1994). EPA water quality criteria for metals have often ignored the local water quality conditions. Thus, WER is the ratio of the LC50 derived from testing the toxicity of a metal to fish or invertebrates in site water to the LC50 derived from testing the toxicity of the same metal to the same test organism (fish or invertebrate) in laboratory water. 

Table 1. A comparison between the 1994 interim procedure and the streamlined procedure for the determination of the water effect ratio (WER) in aquatic environments1.

We have addressed the topic of metal bioavailability and metal toxicity in environmental samples. Traditionally, metal availability is investigated using a chemical approach. Afterwards, the concept of Water Effect Ratio (WER) was proposed by the U.S. EPA and employed bioassays (e.g., fish and invertebrate tests) to assess metal bioavailability and toxicity. In the HMBC approach discussed in this review, we have made use of a bacterial assay that is specific for metal toxicity to achieve this goal. This is only a preliminary survey of the potential applications of the HMBC concept. Some preliminary results on the use of MetPLATE for the fractionation of HMBC to obtain information on the factor(s) that control metal bioavailability in environmental samples were also presented. Using MetPLATE eliminates or diminishes the confounding factor represented by the presence of organic toxicants in a given sample. Further work is needed to refine the fractionation scheme. 

Diamond, J.M., Koplish, D.E., McMahon III, J. and Rost, R. (1997a) Evaluation of the water-effect ratio procedure for metals in a riverine system, Environmental Toxicology and Chemistry 16, 509-520. 

Diamond, J.M., Gerardi, C., Leppo, E. and Miorelli, I. (1997b) Using a water-effect ratio approach to establish effects of an effluent-influenced stream on copper toxicity to the fathead minnow, Environmental Toxicology and Chemistry 16, 1480-1487. 

U.S. EPA (U.S. Environmental Protection Agency) (1994) Interim Guidance on determination and use of water-effect ratios for metals. EPA-823-B-94-001, Washington, DC. 

A diagnosis of possible damage should be made before beginning repairs with other construction measures [48,49]. There should be a checklist [48] of the important corrosion parameters and the types of corrosion effects to be expected. Of special importance are investigations of the quality of the concrete (strength, type of cement, water/cement ratio, cement content), the depth of carbonization, concentration profile of chloride ions, moisture distribution, and the situation regarding cracks and displacements. The extent of corrosion attack is determined visually. Later the likelihood of corrosion can be assessed using the above data. 

We have studied the effect of monomer concentration in the dispersion polymerization of styrene carried out in alcohol-water mixtures as the dispersion media. We used AIBN and poly(acrylic acid) as the initiator and the stabilizer, respectively, and we tried isopropanol, 1-butanol, and 2-butanol as the alcohols [89]. The largest average particle size values were obtained with the highest monomer-dispersion medium volumetric ratios in 1-butanol-water medium having the alcohol-water volumetric ratio of 90 10. The SEM micrographs of these particles are given in Fig. 15. As seen here, a certain size distribution by the formation of small particles, possibly with a secondary nucleation, was observed in the poly-... 

In the production of crude oil, the greatest part of the crude oil occurs as a water-in-oil emulsion. The composition of the continuous phase depends on the water/oil ratio, the natural emulsifier systems contained in the oil, and the origin of the emulsion. The natural emulsifiers contained in crude oils have a complex chemical structure, so that, to overcome their effect, petroleum-emulsion demulsifiers must be selectively developed. As new oil fields are developed, and as the production conditions change at older fields, there is a constant need for demulsifiers that lead to a rapid separation into water and oil, as well as minimal-residual water and salt mixtures. 

Water-silane ratio, effect siloxane, 241 Wettability, specialty polymers, 256... 

A strain P. delafeildii R-8 was reported to desulfurize DBT giving 2-HBP as the end product [92], This strain was isolated from sewage pool of Shanghai oil field. The report described the effect of cell density, oil/water phase ratio, which was very similar to that of IGTS8. These parameters will be discussed in Section 2.2.10. A Michaelis-Menten model was used to describe the kinetics and the Vmax and Km were reported for DBT to be 13mmol/kg dcw/h and 1.3 mM, respectively. 

Table 1 Reversible water effects on an unsupported Co catalyst ratios of wet/dry results (from1 ). Reprinted from Journal of Catalysis, Vol. 210, C. J. Bertole, C. A. Mims and G. Kiss, The effect of water on the cobalt-catalyzed Fischer-Tropsch synthesis, pp. 84-96, Copyright (2002), with permission from Elsevier... 

Negrin MA, Espino-Mesa M, Hernandez-Moreno JM. Effect of water soil ratio on phosphate release P, aluminium and fulvic acid associations in water extracts from Andisols and Andie soils. Eur. J. Soil Sci. 1996 47 385-393. 

From the theoretical viewpoint, acetonitrile is the most suitable solvent to study the correlation of retention times and log P values of analytes, since the dipole moment (2.44) is nearly equal to that of water (2.55) (Figure 4.4). The electron donor effect can therefore be eliminated, and the elution order is not changed on modification of the acetonitrile-water mixture ratio. The first choice of an eluent should therefore be an acetonitrile-water mixture for non-ionic compounds in reversed-phase liquid chromatography. Methanol, acetone, THF, or DMF can then be added to improve the resolution. 

Primary minerals with low surface area (e.g., sihca minerals) and low reactivity mainly affect the physical transport of water, dissolved chemicals, colloids, immiscible (in water) liqnids, and vapors. Secondary minerals generally have high surface area (e.g., clay minerals) and high reactivity that affect the transport of chemicals, their retention and release onto and from the solid phase, and their surface-induced transformations. The sohd phase also can indirectly induce the degradation of chemical compounds, through its effects on the water-air ratio in the system and, thus, on microbiological activity. 

Figure 5A shows experimentally derived profiles of pH vs rate for reactions in H2O and D2O [30, 50, 71]. The magnitude of the apparent isotope effect (ratio of rate constants in H2O and D2O) is 4.4 and the profiles appear to support the possibility that a proton is transferred from (Mg -bound) water molecules. However, careful analysis led us to conclude that a metal ion binds directly to the 5 -oxygen. Since the concentration of the deproto-nated 2 -oxygen in H2O should be higher than that in D2O at a fixed pH, we must take into account this difference in pKa, namely ApKa (=pKa °-pKa ), when we analyze the solvent isotope effect of D2O [30, 50, 68, 71]. We can estimate the pKa in D2O from the pKa in H2O using the linear relationship shown in Fig. 5B [30, 68, 73-75]. If the pKa for a Mg -bound water molecule in H2O is 11.4, the ApKa is calculated to be 0.65 (solid line in Fig. 5B). Then, the pKa in D2O should be 12.0. Demonstrating the absence of an intrinsic isotope effect (kH2o/kD20=l)> the resultant theoretical curves closely fit the experimental data, with an approximate 4-fold difference in...

The effect of adding a surfactant, (NaDDS), was also investigated. One such case only is shown in Fig. 6 where BE is replaced by a 5 1 mixture of BE-NaDDS. The main effect of NaDDS is to increase the miscibility range of the oil in water. Various ratios of BE-NaDDS were used and, as a first approximation, the change in the phase diagram is directly proportional to the concentration of NaDDS. The addition of a surfactant probably stabilizes the microstructures which were already present in the ternary system BE-DEC-H O and decreases the quantity of BE needed to solubilize DEC. Therefore the presence of a surfactant is useful but not essential to the stability of microemulsions. 

Fig. 1.14 The effect of water-reducing admixtures on paste viscosity at various water- cement ratios. 

When a normal, accelerating, or retarding water-reducing admixture is utilized to increase the workability of a concrete mix by direct addition, it would be reasonable to assume that the extent of the effect would be markedly affected by changes in mix design parameters such as cement content, aggregate size, shape and grading, and the water-cement ratio. A study of many hundreds of results, however, indicates that this is not the case and Fig. 

The most widely used application of water-reducing admixtures is to allow reductions in the water-cement ratio whilst maintaining the initial workability in comparison to a similar concrete containing no admixture. This, in turn, allows the attainment of a required strength at lower cement content to effect economies in mix design. 

In the case of lignosulfonate water-reducing agents, the effectiveness in reducing the water-cement ratio diminishes with an increase in either the the C3A or alkali content. In a comparative experiment with three... 

Products based on hydroxycarboxylic acid salts are more effective than lignosulfonates in reducing the water-cement ratio as illustrated in Table 1.15 [75],... 

Economies in mix design are effected by reducing the cement content whilst maintaining the same water-cement ratio. In view of the reduction of paste volume, conflicting recommendation are made of how this should be compensated for. The following is a guide [84] ... 

Air-entraining water-reducing admixtures require special consideration the presence of entrained air leads to a reduction in compressive strength, whilst the water reduction results in a compensatory increase in strength. The effect can be quantified, however, by considering the amount of entrained air in terms of an equivalent volume of water to calculate the (air and water)-cement ratio. This new factor can be used to estimate the expected strength from Fig. 1.37. 

Direct measurement of the effect of aggressive reagents on concrete durability appears to be confined to sea water and sulfate attack, where in both areas it is recognized that the lower the water-cement ratio, the greater will be the resistance to attack and the use of a water-reducing admixture will be obviously helpful. This is confirmed by work carried out in Holland [95] and Japan [84] and a general conclusion is that a reduction in the water- cement ratio from 0.5 to 0.40, would allow a reduction in thickness of cover of the reinforcement by about 50%. 

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