Phosphonic acid, magnesium salt (2:1)

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

In the assessment of magnesium dihydrogenphosphite (Mg(H2PO3)2, CAS 13598-61-3), a read-across approach is followed based on the information available for potassium phosphonate (KH2PO3/K2HPO3 EC 915-179-9). This read-across strategy is based on the hypothesis that the phosphite anion is the driver for the ecotoxicological and toxicological effects of both salts.The read-across hypothesis is justified by the immediate dissociation of magnesium dihydrogenphosphate and potassium phosphonate upon dissolution in aqueous media. Both phosphite salts are highly soluble (>800 g/L) and are only present in their dissociated form in solution, i.e. the magnesium or potassium cation and the phosphite anion. The transformation of the salts into the ions is rapid and complete in relevant environmental and physiological media and therefore no systemic exposure to the salts as such occurs. Exposure to the non-common cations (Mg2+ and K+) does not influence the prediction of the (eco)-toxicity because both elements are abundantly present in natural environments and emissions from these salts do not significantly increase the exposure concentration for magnesium and potassium. Moreover, magnesium and potassium are major essential element for living organisms.Further information is included as attachment in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Sample No.:

#1

Type:

Kd

Value:

50 L/kg

pH:

6.2

Temp.:

20 °C

Matrix:

Vertic Cambisol (Eurosoil 1)

% Org. carbon:

3.27

Sample No.:

#2

Type:

Kd

Value:

15 L/kg

pH:

8.1

Temp.:

20 °C

Matrix:

Rendzina (Euroil 2)

% Org. carbon:

3.72

Sample No.:

#3

Type:

Kd

Value:

14 L/kg

pH:

6.2

Temp.:

20 °C

Matrix:

Dystric Cambisol (Eurosoil 3)

% Org. carbon:

3.01

Sample No.:

#4

Type:

Kd

Value:

19 L/kg

pH:

7.5

Temp.:

20 °C

Matrix:

Orthic Luvisol (Eurosoil 4)

% Org. carbon:

1.31

Sample No.:

#5

Type:

Kd

Value:

3 L/kg

pH:

4.1

Temp.:

20 °C

Matrix:

Orthic Podzol (Eurosoil 5)

% Org. carbon:

5.96

Validity criteria fulfilled:

yes

Conclusions:

Kd values for Magnesium dihydrogenphosphite (Mg(H2PO3)2) in soil, based on the analysis of P in solution, vary between 3 and 50 L/kg across 5 different soils.

Description of key information

Kd values for magnesium dihydrogenphosphite (Mg(H2PO3)2) in soil, based on the analysis of P in solution, vary between 3 and 50 L/kg across 5 different soils, with an average Kd value of 20 L/kg (Log Kd = 1.3 L/kg).

Key value for chemical safety assessment

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

1.3

at the temperature of:

20 °C