hildo krop - Academia.edu (original) (raw)

Papers by hildo krop

Research paper thumbnail of EU Observatory for Nanomaterials: A Constructive View on Future Regulation

SSRN Electronic Journal, 2018

Research paper thumbnail of Epigenetics and chemical risk management in the workplace

Research paper thumbnail of Independent mode sorption of perfluoroalkyl acids by single and multiple adsorbents

Environmental Science: Processes & Impacts, 2021

Based on the independent mode sorption model it is proposed that a two-step adsorption remediatio... more Based on the independent mode sorption model it is proposed that a two-step adsorption remediation technology, a hydrophobic one followed by an electrostatic one, is most efficient for short chain PFAAs.

Research paper thumbnail of Life cycle assessment of flame retardants in an electronics application

The International Journal of Life Cycle Assessment, 2015

Research paper thumbnail of Determination and Theoretical Aspects of the Equilibrium Between Dissolved Organic Matter and Hydrophobic Organic Micropollutants in Water (Kdoc)

Reviews of Environmental Contamination and Toxicology, 2001

Literature on the equilibrium constant for distribution between dissolved organic carbon (DOC) (K... more Literature on the equilibrium constant for distribution between dissolved organic carbon (DOC) (Kdoc) data of strongly hydrophobic organic contaminants were collected and critically analyzed. About 900 Kdoc entries for experimental values were retrieved and tabulated, including those factors that can influence them. In addition, quantitative structure-activity relationship (QSAR) prediction equations were retrieved and tabulated. Whether a partition or association process between the contaminant and DOC takes place could not be fully established, but indications toward an association process are strong in several cases. Equilibrium between a contaminant and DOC in solution was shown to be achieved within a minute. When the equilibrium shifts in time, this was caused by either a physical or chemical change of the DOC, affecting the lighter fractions most. Adsorption isotherms turned out to be linear in the contaminant concentration for the relevant DOC concentration up to 100 mg of C/L. Eighteen experimental methods have been developed for the determination of the pertinent distribution constant. Experimental Kdoc values revealed the expected high correlation with partition coefficients over n-octanol and water (Kow) for all experimental methods, except for the HPLC and apparent solubility (AS) method. Only fluorescence quenching (FQ) and solid-phase microextraction (SPME) methods could quantify fast equilibration. Only 21% of the experimental values had a 95% confidence interval, which was statistically significantly different from zero. Variation in Kdoc values was shown to be high, caused mainly by the large variation of DOC in water samples. Even DOC from one sample gave different equilibrium constants for different DOC fractions. Measured Kdoc values should, therefore, be regarded as average values. Kdoc was shown to increase on increasing molecular mass, indicating that the molecular mass distribution is a proper normalization function for the average Kdoc at the current state of knowledge. The weakly bound fraction could easily be desorbed when other adsorbing media, such as a SepPak column or living organism, are present. The amount that moves from the DOC to the other medium will depend, among other reasons, on the size of the labile DOC fraction and the equilibrium constant of the other medium. Variation of Kdoc with temperature turned out to be small, probably caused by a small enthalpy of transfer from water to DOC. Ionic strength turned out to be more important, leading to changes of a factor of 2-5. The direction of this effect depends on the type of ion. With respect to QSAR relationships between Kdoc and macroscopic or molecular descriptors, it was concluded that only a small number of equations are available in the literature, for apolar compounds only, and with poor statistics and predictive power. Therefore, a first requirement is the improvement of the availability and quality of experimental data. Along with this, theoretical (mechanistic) models for the relationship between DOC plus contaminant descriptors on the one side and Kdoc on the other should be further developed. Correlations between Kdoc and Kow and those between the soil-water partition constant (Koc) and Kow were significantly different only in the case of natural aquatic DOC, pointing at substantial differences between these two types of organic material and at a high correspondence for other types of commercial and natural DOC.

Research paper thumbnail of Determination of environmentally relevant physical‐chemical properties of some fatty acid esters

Journal of the American Oil Chemists' Society, 1997

Fat models frequently use input parameters that are defined at environmental conditions. In a rec... more Fat models frequently use input parameters that are defined at environmental conditions. In a recently developed gas‐liquid chromatography method (GC‐VAP), vapor pressures, heats of vaporization, and heat capacity differences (gas‐liquid) of fatty acid esters are determined over a large temperature range that includes environmental temperatures. This method also allows an accurate determination of the normal boiling point temperature of a substance. Literature values of vapor pressure, boiling point temperature, and heat of vaporization at 298.15 K for the chosen esters are all in excellent agreement with those determined with the developed method. Correlations between carbon number and heat of vaporization are high.

Research paper thumbnail of n-Octanol-water partition coefficients, aqueous solubilities and Henry's law constants of fatty acid esters

Research paper thumbnail of Partition constants of chlorinated dibenzofurans and dibenzo-p-dioxins

Chemosphere, 1998

Vapour pressure, aqueous solubility, Henry law constant, n-octanol-and sediment-water partition c... more Vapour pressure, aqueous solubility, Henry law constant, n-octanol-and sediment-water partition coefficient and bioconcentration factor of all chlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD), in addition to those of the parent compounds DF and DD, were calculated via the SOFA (SOlubility parameters for Fate Analysis)-model. The derivation of these 1272 values was based on 120 experimental data. Mean deviation of calculated values from experimental data amounted to 0.39,0.25, 0.3 1, 0.19, 0.34 and 0.18 log units for the properties mentioned. The values of all compounds were tabulated. Variation of values within isomer groups turned out to be the highest for vapour pressure of the tetra substituted group, but were below 1.40 orders of magnitude. Variation in the complete series amounted to 7.78 orders at a maximum, again for vapour pressure. Accurate, almost linear, relationships were established between the n-octanol-water partition coefficient and aqueous solubility and sediment-water partition coefficient, whereas a parabolic relationship turned out to hold with the bioconcentration factor.

Research paper thumbnail of Sorption of surfactants onto sediment at environmentally relevant concentrations:independent-mode as unifying concept

Environmental Science: Processes & Impacts, 2020

The Independent-Mode model explains observed sorption phenomena of surfactants at low concentrati... more The Independent-Mode model explains observed sorption phenomena of surfactants at low concentrations (Cs→0,Cw→0) to complex sediments better than the Dual-Mode model.

Research paper thumbnail of EU Observatory for Nanomaterials: A Constructive View on Future Regulation

SSRN Electronic Journal, 2018

Research paper thumbnail of Epigenetics and chemical risk management in the workplace

Research paper thumbnail of Independent mode sorption of perfluoroalkyl acids by single and multiple adsorbents

Environmental Science: Processes & Impacts, 2021

Based on the independent mode sorption model it is proposed that a two-step adsorption remediatio... more Based on the independent mode sorption model it is proposed that a two-step adsorption remediation technology, a hydrophobic one followed by an electrostatic one, is most efficient for short chain PFAAs.

Research paper thumbnail of Life cycle assessment of flame retardants in an electronics application

The International Journal of Life Cycle Assessment, 2015

Research paper thumbnail of Determination and Theoretical Aspects of the Equilibrium Between Dissolved Organic Matter and Hydrophobic Organic Micropollutants in Water (Kdoc)

Reviews of Environmental Contamination and Toxicology, 2001

Literature on the equilibrium constant for distribution between dissolved organic carbon (DOC) (K... more Literature on the equilibrium constant for distribution between dissolved organic carbon (DOC) (Kdoc) data of strongly hydrophobic organic contaminants were collected and critically analyzed. About 900 Kdoc entries for experimental values were retrieved and tabulated, including those factors that can influence them. In addition, quantitative structure-activity relationship (QSAR) prediction equations were retrieved and tabulated. Whether a partition or association process between the contaminant and DOC takes place could not be fully established, but indications toward an association process are strong in several cases. Equilibrium between a contaminant and DOC in solution was shown to be achieved within a minute. When the equilibrium shifts in time, this was caused by either a physical or chemical change of the DOC, affecting the lighter fractions most. Adsorption isotherms turned out to be linear in the contaminant concentration for the relevant DOC concentration up to 100 mg of C/L. Eighteen experimental methods have been developed for the determination of the pertinent distribution constant. Experimental Kdoc values revealed the expected high correlation with partition coefficients over n-octanol and water (Kow) for all experimental methods, except for the HPLC and apparent solubility (AS) method. Only fluorescence quenching (FQ) and solid-phase microextraction (SPME) methods could quantify fast equilibration. Only 21% of the experimental values had a 95% confidence interval, which was statistically significantly different from zero. Variation in Kdoc values was shown to be high, caused mainly by the large variation of DOC in water samples. Even DOC from one sample gave different equilibrium constants for different DOC fractions. Measured Kdoc values should, therefore, be regarded as average values. Kdoc was shown to increase on increasing molecular mass, indicating that the molecular mass distribution is a proper normalization function for the average Kdoc at the current state of knowledge. The weakly bound fraction could easily be desorbed when other adsorbing media, such as a SepPak column or living organism, are present. The amount that moves from the DOC to the other medium will depend, among other reasons, on the size of the labile DOC fraction and the equilibrium constant of the other medium. Variation of Kdoc with temperature turned out to be small, probably caused by a small enthalpy of transfer from water to DOC. Ionic strength turned out to be more important, leading to changes of a factor of 2-5. The direction of this effect depends on the type of ion. With respect to QSAR relationships between Kdoc and macroscopic or molecular descriptors, it was concluded that only a small number of equations are available in the literature, for apolar compounds only, and with poor statistics and predictive power. Therefore, a first requirement is the improvement of the availability and quality of experimental data. Along with this, theoretical (mechanistic) models for the relationship between DOC plus contaminant descriptors on the one side and Kdoc on the other should be further developed. Correlations between Kdoc and Kow and those between the soil-water partition constant (Koc) and Kow were significantly different only in the case of natural aquatic DOC, pointing at substantial differences between these two types of organic material and at a high correspondence for other types of commercial and natural DOC.

Research paper thumbnail of Determination of environmentally relevant physical‐chemical properties of some fatty acid esters

Journal of the American Oil Chemists' Society, 1997

Fat models frequently use input parameters that are defined at environmental conditions. In a rec... more Fat models frequently use input parameters that are defined at environmental conditions. In a recently developed gas‐liquid chromatography method (GC‐VAP), vapor pressures, heats of vaporization, and heat capacity differences (gas‐liquid) of fatty acid esters are determined over a large temperature range that includes environmental temperatures. This method also allows an accurate determination of the normal boiling point temperature of a substance. Literature values of vapor pressure, boiling point temperature, and heat of vaporization at 298.15 K for the chosen esters are all in excellent agreement with those determined with the developed method. Correlations between carbon number and heat of vaporization are high.

Research paper thumbnail of n-Octanol-water partition coefficients, aqueous solubilities and Henry's law constants of fatty acid esters

Research paper thumbnail of Partition constants of chlorinated dibenzofurans and dibenzo-p-dioxins

Chemosphere, 1998

Vapour pressure, aqueous solubility, Henry law constant, n-octanol-and sediment-water partition c... more Vapour pressure, aqueous solubility, Henry law constant, n-octanol-and sediment-water partition coefficient and bioconcentration factor of all chlorinated dibenzofurans (PCDF) and dibenzo-p-dioxins (PCDD), in addition to those of the parent compounds DF and DD, were calculated via the SOFA (SOlubility parameters for Fate Analysis)-model. The derivation of these 1272 values was based on 120 experimental data. Mean deviation of calculated values from experimental data amounted to 0.39,0.25, 0.3 1, 0.19, 0.34 and 0.18 log units for the properties mentioned. The values of all compounds were tabulated. Variation of values within isomer groups turned out to be the highest for vapour pressure of the tetra substituted group, but were below 1.40 orders of magnitude. Variation in the complete series amounted to 7.78 orders at a maximum, again for vapour pressure. Accurate, almost linear, relationships were established between the n-octanol-water partition coefficient and aqueous solubility and sediment-water partition coefficient, whereas a parabolic relationship turned out to hold with the bioconcentration factor.

Research paper thumbnail of Sorption of surfactants onto sediment at environmentally relevant concentrations:independent-mode as unifying concept

Environmental Science: Processes & Impacts, 2020

The Independent-Mode model explains observed sorption phenomena of surfactants at low concentrati... more The Independent-Mode model explains observed sorption phenomena of surfactants at low concentrations (Cs→0,Cw→0) to complex sediments better than the Dual-Mode model.