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Adsorption / desorption

Based on the Weight of evidence approach of adsorption endpoint for the target substance Pyrazolone T (Cas no. 118-47-8) studies are summarized as fallowed:

From EPI suite version 4.1 the adsorption capacity of the test chemical in soil was estimated using KOCWIN Program (v2.00) The koc was estimated using MCI method. KOC may be sensitive to pH.

First Order Molecular Connectivity Index = 8.787

Non-Corrected Log Koc (0.5213 MCI + 0.60) = 5.1803

Fragment Correction(s):

1 Nitrogen to non-fused aromatic ring = -0.5225

1 N-CO-C (aliphatic carbon) = -1.0277

* Organic Acid (-CO-OH) = -1.6249

1 Sulfonic acid (-S(=O)-OH) = -2.0000

Corrected Log Koc = 0.0052

Over Correction Adjustment to Lower Limit Log Koc = 1.0000

Estimated Koc = 10 L/kg

The estimated koc value for the test chemical is 10 L/kg

The test chemical has a log Koc of 1. Based on the classification criterion for PBT, the test chemical has negligible sorption to soil and sediment, rapid migration to ground water.

Other two predicted studies for target chemical from Scifinder and chemspider predicted database indicate that the adsorption coefficient (Koc) of test substance Pyrazolone T was found to be 10.

This Koc value suggests that Pyrazolone T is expected to have negligible sorption to soil and sediment.

While read across substance Tartrazine (Cas no. 1934-21-0) study from peer reviewed journal U.P.B. Sci. Bull., Series B, Vol. 78, Iss. 1, 2016 P.137-148 indicate that Soil adsorption test was conducted for test chemical tartrazine by using sorption floatation method.

Initial concentration of test chemical was 5-500 mg/L with pH range of 7-9 at temperature 20 deg C were selected to study tartrazine removal efficiency.

The removal efficiency of chemical tartrazine was found to be 9% using soil as adsorbent in sorption floatation technique.

Another peer reviewed study (Caliman Florentina Anca et al; Afinidad 66, no. 544 (2009)) for same read across i.e Tartrazine (Cas no. 1934-21-0) indicate that experiments were performed by using a natural soil sampled from the depth of 0-15 cm in the industrial area of the city of Iasi during the summer time (July 2008) that was previously dried and further screened to achieve soil particles size of above 2 mm, equilibration being carried-out with solution of CaCl2. For the equilibrium study, 50 ml Acid Yellow 23 of different concentrations were mixed with a dose of 12 g/L soil, the mixture being subjected to stirring at the room temperature as long it was needed to reach the equilibrium.The Freundlich, Langmuir and linear isotherm models were applied to describe the process and the parameters of these equations were calculated.

The sorption equilibrium revealed that the soil with particles higher than 2 mm may uptake 0.25 mg/g.

The sorption process is best represented by the Langmuir isotherm. The results reveal that the sorption of Acid Yellow 23 onto particles of soils follows a pseudo second order kinetics, suggesting that the chemisorption is the rate controlling mechanism.

The organic carbon normalized sorption coefficient KOC = 151.46 L/Kg. The very low value of KOC shows that the dye tend to remain in solution indicating also its very high mobility, since it is considered that sorption coefficients less than 500 indicate a considerable potential for losses through leaching. The low value of the organic carbon normalized sorption coefficient KOC suggests a high potential of leaching that could result in contamination of the groundwater.

Thus based on the above available predicted data for target and peer reviewed studies for resd across studies concluded that the test substance Pyrazolone T (Cas no. 118-47-8) expected to have negligible sorption to soil and sediment and may have potential to migrate towards groundwater.