Category: Koc standard

Koc standard

12.11.2020 By Samuzilkree

The adsorption-desorption distribution coefficient Kd is an important parameter for understanding the mobility of a compound in the environment partitioning and its distribution between water, sludge, soil and sediment compartments OECD, b. The Kd value is used in various environmental models for estimating the extent of removal on sludge during wastewater treatment, of leaching through a soil column, and of runoff from agricultural land into adjacent waters, as examples Wauchope et al, The distribution of a chemical between water and soil, sediment or sludge compartments is dependent upon the characteristics of the chemical as well as the matrix; it may be additionally influenced by external factors such as temperature and rainfall OECD, b; Wauchope et al, Characterisation of Kd in the laboratory and extrapolation to the field can be difficult, largely because of the complexity of adsorption mechanisms that may be relevant for a given chemical and matrix; the mechanisms may be known and unknown in nature Boxall et al, ; ter Laak et al, Kd is often normalised to the organic content of the matrix, in order to obtain the organic carbon-water partition coefficient, KOC Section 2.

While this approach was initially developed for hydrophobic compounds, it is not clear whether such normalisation is appropriate for ionisable substances Chapter 4. For direct measurement of Kd values, a batch or slurry mixing experiment is usually used: a mass of soil ms g is mixed with a volume V ml of water or another medium such as aqueous 0.

Adsorption-desorption distribution (Kd) and organic carbon-water partition (KOC) coefficients

The slurry is then mixed gently in order to disturb the soil structure as little as possible for a period typically from 2 to 48 hours 24 h being a standard. Many studies have shown that the distribution of the chemical in the system approaches a pseudo-equilibrium within a few hours. The liquid phase is then analysed for the equilibrium concentration Ce of the chemical in aqueous solution.

Ideally, the soil phase should also be analysed to confirm the mass balance, but this is usually more difficult and neglected. Thus, Kd a partition coefficient is a ratio of solid phase to solute concentrations. High values of Kd of the order of or more indicate that, at any given time, the majority of the chemical is adsorbed to the soil surface and hence is less likely to move in soil, but it does not indicate the strength reversibility of that sorption.

It should be noted that this is a macroscopic measurement and provides only indirect information on the type of surface interactions taking place. Often Kd values are determined over a range of concentrations at a constant temperature. It has been hypothesised by Giles et al. When considering the shape of the isotherm, it is important to note the concentration range over which the isotherm has been produced, as different shapes may be obtained over different concentration ranges.

The C-type isotherm is proposed to indicate that the affinity of the sorbate for the adsorbent remains constant and that the number of adsorption sites is unlimited. L-type isotherms indicate that the proportion of sorbate adsorbed increases more slowly as the amount of material adsorbed increases and are the most common isotherms obtained for crop protection products.

A more complex situation is represented by the S-type isotherm. This was suggested by Giles et al. An alternative explanation was given by Sposito who suggested that other species in solution compete for the sorbate until these species are fully reacted leaving subsequent sorbate to adsorb unhindered.This page requires that javascript be enabled for some elements to function correctly.

Personal protective equipment is addressed in specific OSHA standards for general industry, maritime and construction. This section highlights OSHA standards and documents related to personal protective equipment. The notices in this list provide additional information that is not necessarily connected to a specific OSHA standard highlighted on this Safety and Health Topics page.

The directives in this list provide additional information that is not necessarily connected to a specific OSHA standard highlighted on this Safety and Health Topics page. The letters in this list provide additional information that is not necessarily connected to a specific OSHA standard highlighted on this Safety and Health Topics page. State Plans are required to have standards and enforcement programs that are at least as effective as OSHA's and may have different or more stringent requirements.

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Thank you for visiting our site. Please click the button below to continue. Standards Personal protective equipment is addressed in specific OSHA standards for general industry, maritime and construction.

Final RulesNovember 15, Stipulates that the employer must pay for required PPE, except in the limited cases specified in the standard. Safety-toe protective footwear and prescription safety glasses were excepted from the employer payment requirement, in large part because these items were considered to be very personal in nature and were often worn off the jobsite.

Final RulesJune 13, Makes corrections to the final rule on personal protective equipment for shipyard employment, which was published in the federal register on May 24, at 61 FR Final RulesMay 24, Discusses revisions of PPE standards for shipyard employment. Personal Protective Equipment for General Industry. Final RulesMay 2, Final RulesJuly 1, Corrects the final rule on personal protective equipment for general industry. Final RulesApril 6, Discusses revisions of personal protective equipment standards.

Office of Special Counsel. Directives Federal Register notices Letters of interpretation Settlement agreements. Federal Register notices Letters of interpretation Settlement agreements.

Directives Federal Register notices Letters of interpretation. Federal Register notices Letters of interpretation.We've made some changes to EPA. This memorandum announces the release of Version 2. General updates as well as model-specific updates were made to the guidance. General updates include:. Parameter descriptions were reformatted, updated to better resemble how they appear in the models, and re-ordered to reflect their order in the models.

Guidance on how to calculate the 90 th percentile of the mean was moved to an appendix. In general, any aquatic modeling that begins on or after the week of November 16, should be conducted with Version 2. Using this guidance document should improve the consistency in modeling the fate of pesticides in the environment and ultimately the overall quality of OPP's aquatic risk assessments.

The primary sources of input fate parameters that are used in these models include pesticide product chemistry and labeling information as well as sorption coefficients, half-lives, and rate constants from acceptable or supplemental environmental fate studies conducted or sponsored by pesticide manufacturers. More specific information about these aquatic models can be found at the Models for Pesticide Risk Assessment web site.

For specific cases, in which deviation from the guidance is appropriate, the model user should document the rationale for each deviation. If multiple aerobic soil metabolism half-life values are available, enter the 90 th percentile confidence bound on the mean half-life value see Equation 1 in Appendix A for instructions. If a single aerobic soil metabolism half-life value is available, enter 3x the half-life value see Equation 2 in Appendix A.

If no aerobic soil metabolism data are available, assume that the compound is stable to biodegradation under these conditions, i. If multiple aerobic aquatic metabolism half-life values are available, enter the 90 th percentile confidence bound on the mean half-life value for the total system water plus sediment see Equation 1 in Appendix A for instructions.

If a single aerobic aquatic metabolism half-life value is available, enter 3x the half-life value see Equation 2 in Appendix A. If no aerobic aquatic metabolism data are available and the pesticide shows insignificant hydrolysis, use 2x the aerobic soil metabolism half-life input value. If no aerobic aquatic metabolism data are available and the pesticide shows significant hydrolysis, enter zero 0.

This input parameter implies degradation by both metabolism and hydrolysis. If a positive value is entered, the model will NOT prompt for an independent hydrolysis rate see hydrolysis section. Example for the case when no aerobic aquatic data are available and the pesticide is hydrolytically stable: For a single aerobic soil metabolism half-life of 30 days, the aerobic soil metabolism half-life input value is 90 days 30 days x 3 ; thus the estimated aerobic aquatic metabolism half-life input value is days 90 days x 2.

The following guidance table is for running PRZM directly rather than through a graphical user interface GUI to estimate exposure in runoff. The main difference with using GUIs is that they typically require half-lives in values of days rather than rate constants in values of day -1 for metabolism parameters.

If multiple foliar decay half-life values are available, enter the rate constant corresponding to the upper 90 th percentile confidence bound on the mean half-life value see Equations 1 and 3 in Appendix A for instructions.

koc standard

If a single foliar decay half-life value is available, enter the rate constant corresponding to 3x the half-life value see Equations 2 and 3 in Appendix A. If no foliar decay data are available, assume that the compound does not decay on foliage, i.

If multiple aerobic soil metabolism half-life values are available, enter the rate constant corresponding to the 90 th percentile confidence bound on the mean half-life value see Equations 1 and 3 in Appendix A for instructions.

If a single aerobic soil metabolism half-life value is available, enter the rate constant corresponding to 3x the half-life value see Equations 2 and 3 in Appendix A.

koc standard

Although EFED rarely receives horizon-specific studies, separate chemical-specific inputs can be created for each horizon. The surface horizon is the most critical horizon for modeling runoff in PRZM.To browse Academia. Skip to main content.

koc standard

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KOC-P-001 Rev. 3 KOC Standard for Painting and Coating of External Metal Surfaces - (Rev.3)

Part of gualitv management coordinated activities to direct and control an organization with regard to qualijy focused on providing confidence that quality requirements will be fulfilled. I DOC.Soil adsorption coefficient Kd measures the amount of chemical substance adsorbed onto soil per amount of water.

It is also known as Freundlich solid-water distribution coefficients Kf. Values for Kd vary greatly because the organic content of soil is not considered in the equation.

Since adsorption occurs predominantly by partition into the soil organic matter, it is more useful to normalize the Kd or Kf to the organic carbon content of a soil and express the distribution coefficient in Koc or Kfoc. Koc is known as organic carbon-water partition co-efficient. Kfoc is called organic-carbon normalized Freundlich distribution coefficient. They are essentially the same thing. Koc is also frequently estimated based on octanol-water partition coefficient Kow and water solubility.

Kd or Koc measures the mobility of a substance in soil. A very high value means it is strongly adsorbed onto soil and organic matter and does not move throughout the soil. A very low value means it is highly mobile in soil. Koc is a very important input parameter for estimating environmental distribution and environmental exposure level of a chemical substance. For pesticides, higher Koc or Kd is better because such pesticides are less likely to leach or occur as surface runoff to contaminate ground water.

Additional terrestrial toxicology tests can be conducted to confirm the toxicity of a substance to soil organisms. The estimates are of higher reliability than those from QSAR calculations. However, as an estimation method it cannot fully replace batch equilibrium experiments used in the OECD Test Guideline We do not provide consultancy services.

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Louis, MO. Contact Gregory Kopp for more information.Suggest new definition. References in periodicals archive? Jamal Abki, general manager of Grandweld Shipyards, said: "Each of the delivered boats was designed to exceed the needs of KOCand similarly built in accordance with Lloyd's Register latest technology for classification standards to provide the highest operational efficiency and safety.

List of Koc Std-rp-015 Series

Kuwait Oil Company to clean 17 million m3 of oil-soaked sand. Kerala Overseas Cricketers: Strengthening camaraderie. Koc said that Bosnia and Herzegovina, with its multiethnic, multiconfessional properties, is a special country. Koc: All religious buildings are sacred and we have to protect them. Production of KOC boats begins. Commenting on the collaboration with Grandweld Shipyards, Sami Al-Sawagh, Marine Operations Manager at KOC emphasized, "This Occasion is the beginning of an extremely important contract phase which is the commencement of production work at the shipyard for building four crew boat and six pilot boats.

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