Partition Coefficient Kow Research Articles

The effect of fungicides on the physiological and biochemical state of lupine plants after seed treatment

Goal. To assess the effect of fungicides on the content of chlorophyll and the activity of antioxidant enzymes (peroxidase, catalase) in lupine plants after seed treatment.
 Methods. Laboratory and vegetation studies were carried out in the laboratory of analytical chemistry of pesticides of pesticides of the Institute of Plant Protection. The seeds of yellow lupine (Lupinus luteus L., variety Obriy) were treated with combined fungicides from different chemical classes: triazoles (cyproconazole, difenoconazole, tebuconazole, prothioconazole), phenylpyrroles (fludioxonil), carboxamides (carboxin), dithiocarbamates (thiram). Determination of the content of fungicides in plants was carried out using chromatographic methods of analysis. Chlorophyll content, peroxidase and catalase activity were determined by physicochemical methods according to generally accepted methods.
 Results. Fungicides activated the antioxidant systems of plants, depending on their physicochemical properties (in particular, the octanol-water partition coefficient Kow) and their content in plants (C, mg/kg). An increase in peroxidase activity (up to 89% compared to the control) was established within 30 days, which indicates the activation of antioxidant processes aimed at maintaining oxidative homeostasis in plants. The change in catalase activity under the influence of fungicides was inversely correlated with peroxidase activity, which is explained by the formation of adaptive mechanisms of ROS homeostasis. The high activity of peroxidase, compared to catalase, testifies to the important role of this enzyme in the redox reactions of plant resistance under the influence of fungicides. The total chlorophyll content under the action of fungicides, increased by 6—20%, compared to the control.
 Conclusions. Seed treatment with fungicides affects the course of redox reactions in plants, causing changes in the activity of key enzymes. The high activity of peroxidase against the background of fluctuations in catalase activity indicates the direct effect of fungicides on the state of antioxidant systems and the important role of peroxidase in maintaining ROS homeostasis. The stimulatory effect of fungicides on the accumulation of chlorophyll at the initial stages of growth of lupine plants was established, the content of which exceeded the control indicator by 6—20% by development phase. Changes in the activity of antioxidant enzymes (catalase and peroxidase) and the content of chlorophyll can serve as criteria for determining the levels of adaptation of lupine plants to the stress effect of fungicides.

Biosorption of process-equipment-related leachables (PERLs) in biomanufacturing: A quantitative approach to study partitioning of PERLs in a cell culture system

The assessment and potential risk of process equipment-related leachables (PERLs) in the production of biopharmaceuticals and cell therapeutics using single-use (SU) equipment has been discussed previously. However, potential interactions of cells with PERLs have not yet been considered. Here, we present a quantitative adsorption study of neutral, organic small-molecule leachable compounds – known for extractables & leachables (E&L) analysis of SU equipment – in aqueous suspensions of CHO and T cells. The solid-water partition coefficient Kd was obtained for all compounds that showed adsorption. The findings implied that hydrophobic interactions are dominant; however, there was no unambiguous correlation between the derived adsorption coefficient Kd and the octanol–water partition coefficient Kow. Interestingly, a maximum affinity of both cell types to the leachable bis(2,4-di-tert-butylphenyl)phosphate, which is known to be detrimental to cell development, was observed. A comparison of both cell types revealed that they generally interact with the same compounds in most cases but to different extents. Using partition coefficients enables estimation of the concentrations of leachable compounds associated with the biomass phase and in the aqueous suspensions and could be used for risk assessment of SU systems in biopharmaceutical and cell therapy (CT) manufacturing processes.

Octanol/Air Partition Coefficient─A General-Purpose Fragment Model to Predict Log Koa from Molecular Structure.

The octanol/air partition coefficient Koa is important for assessing the bioconcentration of airborne xenobiotics in foliage and in air-breathing organisms. Moreover, Koa informs about compound partitioning to aerosols and indoor dust, and complements the octanol/water partition coefficient Kow and the air/water partition coefficient Kaw for multimedia fate modeling. Experimental log Koa at 25 °C has been collected from literature for 2161 compounds with molecular weights from 16 to 959 Da. The curated data set covers 18.2 log units (from -1.0 to 17.2). A newly developed fragment model for predicting log Koa from molecular structure outperforms COSMOtherm, EPI-Suite KOAWIN, OPERA, and linear solvation energy relationships (LSERs) regarding the root-mean-squared error (rms) and the maximum negative and positive errors (mne and mpe) (rms: 0.57 vs 0.86 vs 1.09 vs 1.19 vs 1.05-1.53, mne: -2.55 vs -3.95 vs -7.51 vs -7.54 vs (-5.63) - (-7.34), mpe: 2.91 vs 5.97 vs 7.54 vs 4.24 vs 6.89-10.2 log units). The prediction capability, statistical robustness, and sound mechanistic basis are demonstrated through initial separation into a training and prediction set (80:20%), mutual leave-50%-out validation, and target value scrambling in terms of temporarily wrong compound-Koa allocations. The new general-purpose model is implemented in a fully automatized form in the ChemProp software available to the public. Regarding Koa indirectly determined through Kow and Kaw, a new approach is developed to convert from wet to dry octanol, enabling higher consistency in experimental (and thus also predicted) Koa.

The applicability domain of EPI Suite™ for screening phytotoxins for potential to contaminate source water for drinking

BackgroundToxins produced by plants constitute a potential threat to water supplies in Europe, but have not been widely considered in systematic risk assessments. One way to begin to address potential risks of phytotoxins is to conduct screening-level assessments of known phytotoxins for their potential to contaminate source water for drinking due to persistence (P) and mobility (M). Chemical properties relevant for such an assessment (octanol–water partition coefficient KOW and biodegradation half-life) can be estimated from the structure of phytotoxins with quantitative structure–property relationship (QSPR) models found in the United States Environmental Protection Agency’s Estimation Program Interface (EPI Suite™) software, but predictions must be considered critically since these models have been developed using data for anthropogenic chemicals and many phytotoxins could lie outside their applicability domain.ResultsWe analyzed two EPI Suite™ models—KOWWIN and BIOWIN5—by evaluating the quality of property predictions for their validation sets as a function of Euclidean distances dE to the centroid of descriptor space of the models’ training sets. We identified model-specific applicability domain boundaries as local maxima in plots of the difference between root mean square error (∆RMSE) of modeled property values of validation set compounds within and outside applicability domain boundaries defined by a continuum of possible boundaries. And, we also evaluated four generic boundaries that have been suggested in literature. The ∆RMSE between validation set compounds outside and inside applicability domain boundaries had positive values for all but one of the possible boundaries we considered, indicating that properties of chemicals with dE inside the boundaries were better predicted. With our proposed model-specific boundaries, 21% of 1586 phytotoxins produced by plants found in Switzerland were out of domain of KOWWIN, and 46% of were out of domain of BIOWIN5.ConclusionsEstimates of Log KOW and biodegradation half-life of phytotoxins that lie outside the domain of applicability of the QSPR models should be viewed as extrapolations that are subject to unquantified and potentially large errors. Phytotoxins outside the domain of applicability of QSPR models should be prioritized for property measurements as a basis to expand the training sets of QSPR models and to support hazard identification for better management of drinking water quality in Europe.

Source, Partition and Ecological Risk of Polycyclic Aromatic Hydrocarbons in Karst Underground River Environment, Southern China

As the main source of drinking water in the karst areas of southern China, underground rivers play an important supporting role in local economic and social development. However, due to the special aquifer structure in the karst areas of southern China, polycyclic aromatic hydrocarbons (PAHs) can easily enter the water environment of underground rivers and cause serious pollution, which will affect the water quality safety. In this study, Qing-shui Spring underground river in Nanning city was selected as a representative of the typical underground river in southern China, and the pollution characteristics, source analysis, ecological risk assessment and diffusion law of PAHs were studied. The results showed that the total concentration of PAHs in groundwater and surface sediments was in the range of 282.42–464.88 ng/L and 400.14–1194.69 ng/g, respectively, and the overall concentrations of PAHs were below the moderate pollution level. Pollutant discharge and physical and chemical properties of PAHs caused the concentrations of PAHs to decrease gradually from upstream to downstream, but the proportion of high-cyclic PAHs increased gradually. According to the source analysis results of the ratio method, PAHs sources in groundwater were mainly biomass combustion sources in the upstream, oil sources in the middle and mixed sources in the downstream. Sediment and groundwater had some differences. The middle and upper reaches were the source of biomass combustion, while the middle and lower reaches were the mixed source. The ecological risk assessment results showed that the ecological risk of groundwater was at a moderate level, while the ecological risk of sediment was at a low level. Benzo[a]anthracene (BaA) and benzo[b]fluoranthene (BbF) in groundwater and acenaphthylene (Acy) and fluoranthene (Flu) in sediment should be monitored intensively. Appropriate control measures should be put in place to prevent further pollution. Partition coefficients varied from 0.73 to 3.85 L/g in the sediment–water interface, increasing with the rise of PAH compounds. All of the organic carbon partition coefficients (Koc) in the sediment–water interface were higher than predicate values based on the typical model of equilibrium distribution; this indicated that PAHs were strongly adsorbed in the sediment. The linear free energy relationship coefficient between the Koc value and the n-octanol-water partition coefficient (Kow) was 0.85 but the slope was lower than 1, indicating that sediment in the Qing-shui Spring underground river had weak lipophilic characteristics and adsorption ability for PAHs. The results can provide a reference for the risk assessment and pollution control of PAHs in the karst underground rivers in South China.

Bioaccumulation Kinetics and Bio Concentration Factors of Few Polychlorinated Biphenyls: A Study on Freshwater Fish Puntius ticto

The present work aims to understand the bioaccumulation kinetics and bioconcentration factors (BCF) of the Polychlorinated Biphenyls (PCBs) PCB 126 and PCB 169 in tissues of fish Puntius ticto. A continuous fed system was used to carry out the study. Bioconcentration in the tissues of the fish has been summarised using a first order uptake model. Fish were exposed to the PCBs continuously for a period of 30 days and this exposure has been used to calculate the steady state of BCF. The gill tissue of P. ticto showed a maximum rate of bioaccumulation of 30.61 μg g-1 wet weight for PCB 169 and 19.91 μg g-1 wet weight for PCB 126 respectively. In this study, the regression coefficients (R2), were found to vary between 0.736 and 0.97. This is indicative of a good to high correlation between the PCB concentration and exposure time. Prediction of the Octanol water partition coefficient (Kow) has been carried out to demonstrate the hydrophobic property of PCB compounds and their attraction towards lipid. The actual calculated BCF values have been used to predict the Kow values. Results indicate that it is possible to correlate the Kow values with both the lipid content of the tissue and the exposure time, in case of either PCB, and that the burden of PCB differs from one tissue to another.

How are Humans Exposed to Organic Chemicals Released to Indoor Air?

Humans are exposed to organic chemicals released to indoor air through near-field exposure routes such as air inhalation and nondietary dust ingestion as well as far-field exposure routes such as consumption of food. Here, we explore the relative importance of near- and far-field exposure routes and its variability between chemicals, age groups, and subpopulations, by modeling aggregate human exposure to indoor-released chemicals with diverse partitioning behavior and degradability. Our model results indicate that if chemicals are assumed to be perfectly persistent, dietary and nondietary ingestion dominates human exposure to hydrophobic chemicals of relatively low volatility (with an octanol-air partition coefficient KOA > 106.5 and an octanol-water partition coefficient KOW < 1011), whereas inhalation of indoor air dominates human exposure to volatile chemicals. Other exposure routes, for example, dermal absorption and drinking water, make a relatively small contribution to human exposure. Reduced chemical persistence in environmental media and biota lowers the contribution of dietary ingestion. For most chemicals other than those with a KOA between 109 and 1012 and a KOW between 106 and 109 (e.g., polybrominated diphenyl ethers), the relative importance of near- and far-field exposure routes is primarily governed by chemical partitioning and degradability rather than age- and population-dependent human exposure factors.

Accumulation and Elimination Kinetics of 2-Methylisoborneol in Crucian Carp (Carassius carassius)

2-methylisoborneol (2-MIB) is a common, earthy-smelling compound that causes taste and odor issues in aquaculture. To quantify the distribution, absorption, and depuration of 2-MIB in crucian carp (Carassius carassius), we detected and measured 2-MIB it via microwave, headspace solid-phase microextraction (HS-SPME), and gas chromatography before and after exposing fish to two different concentrations of 2-MIB (200 ng/L and 500 ng/L). The results showed that during the exposure time, the fish absorbed 2-MIB rapidly within 4 h. After exposure to 2-MIB for 120 h, the 2-MIB in gill and liver were rapidly removed. The processes of accumulation and elimination of 2-MIB in fish were investigated using the one-compartment kinetic model. The modeling results showed that the range of the uptake rate constant (k1) was 0.49-6.91. The range of the elimination rate constant (k2) was 0.05-0.27 and uptake rates were higher than elimination rates. The bioconcentration factor (BCF) was estimated according to the physicochemical properties of 2-MIB, and the bioaccumulation of 2-MIB in fish had a close correlation with the octanol/water partition coefficient (Kow).

Phase Ratio and Equilibrium Constant in RP-HPLC Obtained from Octanol/Water Partition Constant Through Solvophobic Theory

The experimentally known dependence in RP-HPLC of the retention factor k′ on octanol/water partition coefficient (K ow) has been examined based on solvophobic theory. The result showed that the dependence provides a means for the evaluation of phase ratio (Φ) of RP-HPLC columns, and of the equilibrium constant for a given compound and mobile phase. Using this theory, the phase ratio was evaluated for a set of seven different C18 columns (five having fully porous particles and two core–shell particles), and the equilibrium constants were calculated for four homologous series of compounds in two mobile phase systems. One mobile phase was methanol/aqueous solution of 0.1% H3PO4, and the other was acetonitrile/aqueous solution of 0.1% H3PO4. Besides providing the values for Φ for the evaluated columns, the results of the study indicated that for a specific composition of the mobile phase and for a given compound displaying only hydrophobic interactions, the equilibrium constant K(X) for different C-18 columns is basically the same. The data were further used to provide guidance in the selection of a chromatographic column for a specific separation based on K ow values and chemical structure of the analytes. The study indicated that the separation of compounds with identical polar groups (or no polar groups) and with very close values for the K ow cannot be achieved based only on hydrophobic interactions that dominate the separation on RP-type columns. Only column that displays polar interactions may provide a solution to such separations. For hydrocarbons with close K ow values, the separation cannot be achieved even on columns with some polarity. On the other hand, even compounds with equal K ow values, but with different functionalities can be separated on RP-HPLC columns without involving polar interactions. The compounds with different K ow values are expected to be easily separated on RP-HPLC columns.

Development of a general baseline toxicity QSAR model for the fish embryo acute toxicity test

Fish embryos have become a popular model in ecotoxicology and toxicology. The fish embryo acute toxicity test (FET) with the zebrafish embryo was recently adopted by the OECD as technical guideline TG 236 and a large database of concentrations causing 50% lethality (LC50) is available in the literature. Quantitative Structure-Activity Relationships (QSARs) of baseline toxicity (also called narcosis) are helpful to estimate the minimum toxicity of chemicals to be tested and to identify excess toxicity in existing data sets. Here, we analyzed an existing fish embryo toxicity database and established a QSAR for fish embryo LC50 using chemicals that were independently classified to act according to the non-specific mode of action of baseline toxicity. The octanol-water partition coefficient Kow is commonly applied to discriminate between non-polar and polar narcotics. Replacing the Kow by the liposome-water partition coefficient Klipw yielded a common QSAR for polar and non-polar baseline toxicants. This developed baseline toxicity QSAR was applied to compare the final mode of action (MOA) assignment of 132 chemicals. Further, we included the analysis of internal lethal concentration (ILC50) and chemical activity (La50) as complementary approaches to evaluate the robustness of the FET baseline toxicity. The analysis of the FET dataset revealed that specifically acting and reactive chemicals converged towards the baseline toxicity QSAR with increasing hydrophobicity. The developed FET baseline toxicity QSAR can be used to identify specifically acting or reactive compounds by determination of the toxic ratio and in combination with appropriate endpoints to infer the MOA for chemicals.

A Critical Evaluation on the Performance of COSMO-SAC Models for Vapor–Liquid and Liquid–Liquid Equilibrium Predictions Based on Different Quantum Chemical Calculations

The performance of two versions of the COSMO-SAC activity coefficient model is carefully examined based on eight sets of quantum chemical computations [VWN-BP/DNP, b3lyp/6-31G(d,p), b3lyp/6-31G(2d,p), b3lyp/6-31+G(d,p), b3lyp/6-311G(d,p), wb97xd/6-31G(d,p), wb97xd/6-31G(2d,p), and wb97xd/6-31+G(d,p)] and one semiempirical calculation (PM6). Furthermore, the effect of the molecular geometry is examined based on equilibrium structures determined both in a vacuum, representing a nonpolar environment, and in a conductor, representing a highly polar environment. The model parameters are reoptimized for each quantum chemical calculation method, and the performance is evaluated using a large set of databases covering the vapor–liquid equilibrium, liquid–liquid equilibrium, infinite-dilution activity coefficient of binary mixtures, and octanol–water partition coefficient (Kow; containing over 22000 data points). It is found that the original COSMO-SAC model is sensitive to the quantum chemical method used, wherea...

Evaluation of acute-to-chronic ratios of fish and Daphnia to predict acceptable no-effect levels.

BackgroundAcute-to-chronic extrapolation is an important approach to predict acceptable no-effect levels from acute data which has some uncertainties, but is valuable for risk assessment of chemical substances. With regard to the still limited and heterogenic data of chronic fish tests, conclusions on aquatic hazard estimation need to be checked and the question arises whether the chronic toxicity to fish can be adequately derived from acute data. A comprehensive dataset including ecotoxicological studies of 203 substances was used to investigate acute-to-chronic ratios (ACR) for both fish and Daphnia. To address potential uncertainty parameters of the approach, the influence of the octanol–water partition coefficient Kow, the mode of action, and the acute toxicity levels on the ACR was evaluated.ResultsFor industrial chemicals, median ACRs of 12.0 for fish and 8.8 for Daphnia and 90th percentiles of 68.0 and 50.2, respectively, were determined. The ACR for the most sensitive aquatic trophic level (ACRaqu) is derived by comparing the lowest acute and chronic effect value of Daphnia and fish. The median ACRaqu was 9.9, and the 90th percentile was determined to 58.5. The influence of the Kow on the ACR value was analysed and a correlation could not be confirmed. Non-polar narcosis was associated with a lower ACR, whereas polar narcosis was associated with an increased ACR.ConclusionsThe result suggests that an acute-to-chronic extrapolation factor of 100 is protective for more than 90 % of the chemicals. Polar narcosis may represent a predictor for an increased ACR and an increased uncertainty of the approach. The result further suggests that a high Kow is probably not associated with increased ACRs and does not necessarily represent a determinant for chronic toxicity testing within this context.

Bioaccumulation of PAHs in marine zooplankton: an experimental study in the copepod Pseudodiaptomus marinus

Fil: Arias, Andres Hugo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Instituto Argentino de Oceanografia. Universidad Nacional del Sur. Instituto Argentino de Oceanografia; Argentina. Universidad Nacional del Sur; Argentina

Ion Chromatography of Tri-Substituted Imidazolium Ionic Liquid Cations: Method and Application for Octanol–Water Partition Coefficient (KOW) Determination

A method was developed for simultaneous determination of four trisubstituted imidazolium ionic liquid cations (1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl-2,3-dimethylimidazolium) by ion chromatography using a carboxylic acid cation exchanger bonded to a silica-based column and direct (nonsuppressed) conductivity detection. The effects of the type of eluents, organic acid concentration, acetonitrile volume fraction, and column temperature on the cations retention were investigated. The optimal conditions for the method were 5 mmol L−1 methanesulfonic acid +10% acetonitrile as an eluent, 1.0 mL min−1 flow rate, and a column temperature of 30°C. The detection limit (S/N = 3) were 0.82–2.39 mg L−1 for the cations. The method was validated, accurate, and reproducible. This method was successfully applied to determine trisubstituted imidazolium ionic liquid cations in spiked tap water. The octanol–water partition coefficients (Kow) of these four trisubstituted imidazole substances were also reported in this study.

Determination of Retardation Factor of Perchloroethylene in Low Organic Carbon Aquifer

The retardation factor (R) expression was deduced for amended double-mode sorption isotherm of perchloroethylene (PCE) in low organic carbon content (0.080~0.090%) aquifer. The retardation effect varied with the solute concentration, the higher the concentration was, the lower the retardation factor. The values of R were determined and compared with the estimation values based on octanol-water partition coefficient (Kow), solubility data of a particular compound and Linear Free-Energy Relationships (LFER). It indicated that there were obvious discrepancy of R among the determinations and estimations. Although how to determine the exact value of R is still questioned, it may be advisable and feasible to understand the retardation effect using batch sorption tests in studying the transport of pollutant in aquifer, especially in mathematical simulation study.

Soil sorption and leaching of active ingredients of Lumax® under mineral or organic fertilization

The study describes the soil sorption of the herbicide Lumax®, composed of S-metolachlor (MTC), terbuthylazine (TBZ), and mesotrione (MST), as influenced by mineral and organic fertilizers. The investigation was performed on a sandy soil of an agricultural area designated as a Nitrate Vulnerable Zone, where mineral and organic fertilizers were applied for many years. Two organic fertilizers, cattle manure and slurry, respectively, and a mineral fertilizer with a nitrification inhibitor, Entec®, were compared. According to the experiments, performed with a batch method, the sorption conformed to Freundlich model. The extent of sorption of Lumax® ingredients was closely related to their octanol–water partition coefficient Kow. The respective desorption was hysteretic. Leaching trials were carried out by using water or solutions of DOM or Entec® as the eluants. Only the elution with the mineral fertilizer promoted the leaching of Lumax® active ingredients.

Octanol/water partition coefficients Kow: A critical examination of the value of the methylene group contribution to log Kow for homologous series of organic compounds

The literature data for the values of the octanol/water partition coefficient KOW are examined critically, specifically in relation to the methylene group increment in logKOW – here called the lipicity L – for homologous series. With simply substituted alkanes, the plots of L versus the methylene group number m are linear, following the form: L=α+βm (Collander equation). The slope parameter β represents the methylene group increment, which widely is expected to be constant on the simplest theoretical grounds, and assumed to be so in most practical applications. The Collander equation behaviour for some 84 homologous series and subseries, ranging in complexity from the alkanes up to the alkyladenines and alkyl galactosides, is presented graphically. Compounds with α,ω-disubstituted alkyl chains give nonlinear Collander plots. The remaining series give linear Collander plots, but the methylene group increment β is not constant, the variation being statistically significant, with the distribution essentially normal (Gaussian) and with the mean value β¯=0.52 and standard deviation σ(β)=0.06. The literature data from other solvent/water systems – ethoxyethane (diethyl ether), and the two alkanes heptane and hexadecane – show similar behaviour. Most significantly, the fact that the methylene group increment β is not constant casts doubts on the applicability of the linear free energy approach, and of the “fragmental methods” that are widely used in interpreting and predicting partition coefficients. More generally, the graphical approach used is essential in a proper treatment of correlations of this kind; the graphs form an atlas that shows at a glance the partition coefficient behaviour for these series, revealing anomalies in the literature data that need to be rectified, and gaps that need to be filled.

The residues, distribution, and partition of organochlorine pesticides in the water, suspended solids, and sediments from a large Chinese lake (Lake Chaohu) during the high water level period

The levels of organochlorine pesticides (OCPs) in the water, suspended solids, and sediments from Lake Chaohu during the high water level period were measured by a solid-phase extraction gas chromatograph-electron capture detector. The spatial distributions of the three phases and the water/suspended solids and sediment/water partition coefficients were analyzed. The results showed the following: (1) The mean contents of OCPs in the water, suspended solids, and sediments were 132.4 ± 432.1 ng/L, 188.1 ± 286.7 ng/g dry weight (dw), and 13.7 ± 9.8 ng/g dw, respectively. The dominant OCP components were isodrin (85.1%) for the water, DDTs (64.4%) for the suspended solids, and both isodrin (48.5%) and DDTs (31.8%) for the sediments. (2) β-HCH was the primary isomer of HCHs in the water and sediments, and the proportions were 61.7 and 41.3%; γ-HCH was the primary isomer in the suspended solids, accounting for 49.3%; p,p'-DDT was the dominant content of DDTs in the water and suspended solids, whereas p,p'-DDD was the main metabolite of DDTs in the sediments. (3) The concentrations of contaminants in the water from the western lake were greater than those from the eastern lake, but the concentrations in the suspended solids from the western lake were less than those from the eastern lake. (4) There was no significant correlation between the water-suspended solids partition coefficient Kd and the n-octanol-water partition coefficient Kow, and between the sediment-water organic-C weighted sorption coefficients Koc and Kow.

Removal of Atrazine, Metribuzin, Metolachlor and Alachlor by Granular Carbon

Adsorption-desorption of atrazine, metribuzin, alachlor and metolachlor on granular carbon were studied in a batch study. All herbicides were highly sorbed on the granular carbon (93.8-100%). Adsorption data were subjected to the Langmuir and the Freundlich adsorption isotherms, and fitted well to the Freundlich adsorption isotherm (r2>0.96). Except alachlor, where the isotherm was nearly linear, 1/n values for atrazine, metribuzin and metolachlor isotherms were <1, suggesting a decrease in herbicide adsorption with increasing concentration in the aqueous phase. The Freundlich adsorption parameter [Kf(1/n)] values were 6813.6, 2981.8, 1420.7 and 5661.4 for atrazine, metribuzin, metolachlor and alachlor, respectively. Thus, granular carbon showed the highest adsorption capacity for atrazine followed by alachlor, metribuzin and metolachlor. However, a desorption study suggests that, except alachlor (<3%), none of the herbicides were desorbed during three desorption cycles. Although alachlor adsorption coefficients were higher than those of metribuzin and metolachlor, it was desorbed. The Freundlich constant Kf showed a positive correlation with solubility (S) while no correlation was observed with the octanol-water partition coefficient (Kow). Results of three sequential adsorption studies suggest that the order of herbicide adsorption was: atrazine>metribuzin>metolachlor>alachlor. This is in agreement with the desorption results, which suggested that granular carbon had poor retention capacity for alachlor. Among the herbicides used in this study, granular carbon has maximum retention capacity for atrazine.

Estimating Octanol / Water Partition Coefficients by Order Preserving Mappings

Douglas Jay Klein and other researchers have seen that there is a great potential in applying par- tial order in the field of QSAR. The basic idea is to deduce from order relations among chemicals, proper- ties of the ordered chemicals. Despite the satisfactory results found by Klein's methods, we think it is worth exploring another feature of the poset of chemicals used in Klein's approaches, namely the average posetic height, hav, of each chemical. In the current paper we explore some methods to calculate these heights and use them as independent variables for modelling a chemical property that is also modelled by Klein's approaches, namely octanol / water partition coefficient KOW. It turned out that the application of average heights, hav, as predictors of a linear log KOW estimation leads to reasonable results in the applica- tion example of chlorophenols. (doi: 10.5562/cca2296)