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21.
Quality control is a crucial aspect of database management, particularly for physicochemical parameters that are widely used
in modeling environmental fate processes. Complete rechecking of original studies to verify environmental fate parameters
is time consuming and difficult. This paper evaluates an alternative, more efficient approach to identifying database errors.
The approach focuses verification efforts on a targeted subset of entries by making use of the relationship between water
solubility (S) and soil organic carbon partition coefficient (K
oc
). Two regression equations, one selected from the literature and one calculated from entries in the database, were used to
evaluate the reasonableness of (S, K
oc
) pairs among control compared to the targeted outlier group from a total of 59 pesticides. Our hypothesis was that (S, K
oc
) pairs that lay far from the regression line were more likely to be in error than those that fit the regression. Database
values were checked against original studies.
Identified errors in the database included coding mistakes, miscalculations, and incorrect chemical identification codes.
The error rate in outlier (S, K
oc
) pairs was about twice that of pairs that conformed to the regression equation; however, the error rate differential was
probably not large enough to justify the use of this quality control method. Through our close scrutiny of database entries
we were able to identify administrative practices that led to mistakes in the data base. Resolution of these problems will
significantly decrease the number of future mistakes. 相似文献
22.
XIYUN CAI ANPING ZHANG WEIPING LIU 《Journal of environmental science and health. Part. B》2013,48(7):1115-1129
Cyclodextrins (CDs) possess a hydrophilic external surface and a hydrophobic cavity. They are thus highly soluble and, in the meantime, effectively form inclusion complexes with hydrophobic organic compounds to enhance their solubilities. In this study, the complexation between modified β-CDs and the herbicide diclofop-methyl (DM), (2-(4-(2,4-dichlorophenoxy)-phenoxy) propionate), was investigated. The complexation was confirmed by the shifts in the wavelengths of maximum ultra violet (UV) absorption and fluorescence excitation/emission. The deuterium isotope effects indicate that in the presence of β-CDs the solubility of DM was lower while that of diclofop was higher in D2O than in H2O, suggesting the primary role of hydrophobic interactions in complexation. The solubility of DM was enhanced in the presence of β-CDs, the extent of which depended on the modification of β-CDs. The complexation reduced the hydrolysis of DM and hence increased its stability. The small inconsistency in the power of β-CDs between hydrolysis retardation and solubilization suggests that hydrolysis was affected by the properties of β-CDs and the configuration of DM in the complexes. Use of β-CDs may thus result in the mobilization of soil DM. Properly modified β-CDs may be utilized as formulation additives for improved delivery of DM and for enhanced environmental remediation. 相似文献
23.
G. G. D. Silva P. J. A. Sobral R. A. Carvalho P. V. A. Bergo O. Mendieta-Taboada A. M. Q. B. Habitante 《Journal of Polymers and the Environment》2008,16(4):276-285
The aim of this work was to develop biodegradable films based on blends of gelatin and poly (vinyl alcohol) (PVA), without a plasticizer. Firstly, the effect of five types of PVA with different degree of hydrolysis (DH) on the physical properties of films elaborated with blends containing 23.1% PVA was studied. One PVA type was then chosen for the study of the effect of the PVA concentration on the mechanical properties, color, opacity, gloss, and water solubility of the films. The five types of PVA studied allowed for films with different characteristics, but with no direct relationship with the DH of the PVA. Therefore, the PVA Celvol®418 with a DH = 91.8% was chosen for the second part, because they produced films with greater tensile strength. The PVA concentration affected all studied properties of films. These results could be explained by the results of the DSC and FTIR analyses, which showed that some interactions between the gelatin and the PVA occurred depending on the PVA concentration, affecting the crystallinity of the films. 相似文献
24.
水中硫化氢的溶解规律 总被引:3,自引:0,他引:3
对气体在水中的溶解机制进行了分析,并结合实验数据导出了硫化氢在水中溶解度的预测公式,该预测公式准确度较高,其平均绝对误差及平均相对误差分别为0.026g/L和0.062%. 相似文献
25.
Aim of the present study was an attempt to find a correlation between physicochemical structure of veterinary drugs and the maximum residue limit (MRL) for muscle tissue of food producing animals. Direct correlation and analysis in quintile groups for 52 physicochemical parameters were performed. An internal validation using leave-one-out cross-validation was performed. In the quintile groups, there were 11 arithmetic expressions created for the limited group of individual parameters (13 from 52 analyzed), which showed a significant linear or quadratic correlation between the number of quintile group and the mean value of MRL within the quintile. The results obtained suggest that there is no direct correlation between individual physicochemical parameters and MRL value in muscle tissue; however, such correlation can be determined for arithmetic expressions created on the basis of several physicochemical parameters, using quintile group analysis. 相似文献
26.
27.
Henry’s law constants for 12 chlorinated volatile organic compounds (CVOCs) were measured as a function of temperature ranging from 8 to 93 °C, using the modified equilibrium partitioning in closed system (EPICS) method. The chlorinated compounds include tetrachloroethylene, trichloroethylene, cis-1,2-dichloroethylene, vinyl chloride, 1,1,1-trichloroethane, 1,1-dichloroethane, 1,2-dichloroethane, chloroethane, carbon tetrachloride, chloroform, dichloromethane, and chloromethane. The variation in Henry’s constants for these compounds as a function of temperature ranged from around 3-fold (chloroethane) to 30-fold (1,2-dichloroethane). Aqueous solubilities of the pure compounds were measured over the temperature range of 8-75 °C. The temperature dependence of Henry’s constant was predicted using the ratio of pure vapor pressure to aqueous solubility, both of which are functions of temperature. The calculated Henry’s constants are in a reasonable agreement with the measured results. With the improved data on Henry’s law constants at high temperatures measured in this study, it will be possible to more accurately model subsurface remediation processes that operate near the boiling point of water. 相似文献
28.
Magnus E. Skold Geoffrey D. Thyne John W. Drexler John E. McCray 《Journal of contaminant hydrology》2009,107(3-4):108-113
Carboxymethyl-β-cyclodextrin (CMCD) has been suggested as a complexing agent for remediation of sites co-contaminated with metals and organic pollutants. As part of an attempt to construct a geochemical complexation model for metal-CMCD interactions, conditional formation constants for the complexes between CMCD and 7 metal ions (Ba, Ca, Cd, Ni, Pb, Sr, and Zn) are estimated from experimental data. Stable metal concentrations were reached after approximately 1 day and estimated logarithmic conditional formation constants range from − 3.2 to − 5.1 with confidence intervals within ± 0.08 log units. Experiments performed at 10 °C and 25 °C show that temperature affects the solubility of the metal salts but the strength of CMCD-metal complexes are not affected by this temperature variation. The conditional stability constants and complexation model presented in this work can be used to screen CMCD as a potential remediation agent for clean-up of contaminated soil and groundwater. 相似文献
29.
The solubility data for a series of non‐hydrogen bonding, monosubstituted benzenes in binary mixtures of water and non‐hydrogen bonding cosolvents is presented. Good correlation between log solubility and fraction cosolvent is obtained, therefore the estimation of solubility in mixed solvents by a log‐linear relationship can be attained. Slight positive or negative deviations from predicted solubility values are seen at high volume fractions of cosolvents. These deviations are attributed to the cosolvent‐water interactions. 相似文献
30.
Antimony (Sb) distribution, solubility and mobility onto natural soils of China were studied in lysimeter and batch experiments as a function of physicochemical properties of the soil. An outdoor lysimeter experiment investigated the leaching and migration of Sb in the soils with Sb-polluted topsoil and unpolluted subsoil over a 5 month period. Soil solutions were collected by suction cups installed at different depth of lysimeters, and leachates were regularly collected and analyzed for Sb concentrations. The majority of the added Sb was retained in the topsoil layers, but small portions were moved to the sub-layers. Sb concentrations in the soil solutions and leachates ranged from 0–755.5 (6.38 ± 54 on average) μg l−1 and 0–0.45 (smaller than the detection limit) μg l−1 respectively, indicating the low solubility of Sb in the soils. Batch experiments were performed in order to determine the sorption capacity and the partition coefficient (Kd). Freundlich isotherm described properly the equilibrium experimental data and results show that the Kd values for Primosol, Isohumosol, Ferrosol equal to 22.5, 87.8, 704 L kg−1, respectively. These results showed the strong capacity of the soils to retain Sb, and prevent it being leached down the profile. The mobilizable Sb was in the order: Primosol > Isohumosol > Ferrosol. Sb migration in the soils was mainly associated with the exchangeable, carbonate-bound, and metal–organic complex-bound fractions. Health risk assessment indicates that Sb leaching from Ferrosol will not harm to human health through groundwater under the test conditions, while it has certain health risks from the Isohumosol and Primosol. 相似文献