Glutaral

Adsorption / desorption

Description of key information

Glutaraldehyde is mobile to moderately mobile soils. Furthermore, the substance is readily biodegradable.

Key value for chemical safety assessment

Koc at 20 °C:

326

Additional information

The first study on adsorption/ desorption in soil (Shepler 1994) was conducted according to EPA FIFRA Subdivision N Pesticide Guideline 163-1 (Batch Equilibrium Method). The adsorption phase was carried out at 25 °C for appr. 24 hours with four different soils (sandy loam, silty clay loam, silt loam, loamy sand) and one sediment. Desorption was performed by resuspending each of the soil pellets with fresh 0.01 M CaCl2 solution following by an incubation for additional 24 hours. After 24 hours adsorption phase glutaraldehyde formed 11.8 – 69.2% and glutaric acid 10.2 – 59.4% of radioactivity in the four soils and sediment. At least eight other unknown metabolites were formed but they accounted less than 10% of radioactivity apart from one metabolite which accounted 10.5% in one soil. Due to rapid degradation desorption isotherms could not be determined. The rapid degradation of glutaraldehyde that was observed during the desorption phase of the study indicates that the compound will not persistent in the soil environment and thus, Freundlich K values for desorption could not be calculated. Potential movement/leaching of glutaraldehyde in soil (e.g. as a result of a spill), will be minimized by rapid degradation of the compound. The adsorption constants for glutaraldehyde were determined to be 210 for sandy loam, 500 for silty clay loam, 340 for silt loam, 460 for loamy sand and 120 for sediment. The arithmetric mean Koc value was 326. Thus, glutaraldehyde is mobile to moderately mobility in soil.

Adsorption / desorption was investigated according to EPA Guideline 163-1 (ABC Lab 2734). After an incubation period of 30 days at 25 °C the adsorption/desorption constants were determined for 14C-glutaraldehyde incorporated into four different soil types. The adsorption constant values are different and indicate that only the loamy sand showed an increased potential of adsorption to solid soil particles (log Koc 3.32) whereas for the remaining soil types the adsorption potential was low to moderate (loam: log Koc 1.35; silt loam: log Koc 1.28; clay loam: log Koc 0.76). For loamy sand an aerobic soil metabolism study was conducted, which resulted in a DT50 of 1.7 days for glutaraldehyde. The DT50 value indicates that glutaraldehyde was rapidly degraded in soil by microbial biotransformation. However, the stability of glutaraldehyde in the test conditions was not determined. Due to rapid transformation of glutaraldehyde (half-life in soil 1.7 days) and a long incubation period (30 days) it is unlikely that any significant amount of the parent compound was present in the soils in the start of the experiment. No specific analytical method was applied after the liquid scintillation counting in order to analyse what substances the radioactivity represented. Therefore, the results of this study was not considered further.

A third study (Gonsior 2001) on adsorption of glutaraldehyde to activated sludge according to ISO/CD 18749 Batch Adsorption Test was conducted for 24 hours with a concentration of 3 mg/L. An overall removal corresponded to a half-life ofappr. 0.14 hours and overall disappearance rate of 4.95 h-1 for Glutaraldehyde was observed in viable reaction mixtures, and 0.66 hours in activated sludge sparged with argon to minimize biological activity. The degradation rate and half-life are converted to 15 °C which is the default temperature for the STP with the equation F_T= 1.072^(T-Tref). T is the default temperature (15 °C) and Tref related to biodegradation rate is assumed to be 22.5 °C. The converted values are 2.9 h^-1and half-life 0.2 h. Glutaraldehyde is rapidly removed in activated sludge by a combination of biodegradation and irreversible binding (e.g. covalent binding) to the activated sludge.

Another study on adsorption in soil was published in a review paper by Leung (2001). The C14-labelled glutaraldehyde was tested at following concentrations: 0.51, 1, 2.5, 5 and 10.3 mg/l. The adsorption phase was conducted in teflon centrifuge tubes containing 30 ml test solution and either 10 g of sandy loam, 5 g of silty clay loam, 5 g of silt loam, 20 g of loamy sand or 20 g of sediment held in a shaking water bath at 25 °C. The estimated log Koc ranged between 2.1 and 2.7. Based on the results, glutaraldeyhde is predicted to have moderate mobility in each of the tested soil but with a high motility in sediment.

In addition, EpiWin calculations resulted in a log Koc value of -0.83 (i.e. Koc = 1.0; KocWin v2.00 calculation); the log Koc value being < 1, an adsorption of the test substance to the solid soil phase is not expected.

In conclusion, glutaraldehyde shows a low to moderate potential of adsorption to solid soil particles. As glutaraldehyde showed a rapid degradation in loamy sand by microbial biotransformation in the first study and the second study determined a moderate mobility in all four soils as well in loamy sand, a persistence of glutaraldehyde in soil is unlikely. In addition, the low potential of persistence was underlined by the rapidly removal of glutaraldehyde in activated sludge by a combination of biodegradation and irreversible binding (e.g. covalent binding) to the activated sludge. For the sediment the Koc values for glutaraldehyde falls into the high moblity range. 

[LogKoc: 2.5]