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Description of key information

Soil toxicity is estimated using the equilibrium partitioning method, using a measured adsorption coefficient value. Due to the use pattern of Piperazine, no exposure to soil is expected.

Additional information

PNEC derivation for sediment and soil for piperazine using the EPM

The sorption/desorpion study of piperazine on soil, which was performed according to OECD 106 resulted in Kd values for three different soils. For Loam soil, sand soil and Sandy loam soil, Kd values of respectively 7.9, 15.3 and 20.1 L/kg were observed.

The mean value of 14.43 L/kg of these three observed Kd values will be used for risk assessment.

Thisvalue of the Kd will be usedfor soil and sediment. This is considered acceptable because there is besides to the organic carbon content no principal difference between soil and sediments considering the sorption properties and because of the cationic behavior of this substance, the degree of sorption is not related to the organic carbon content and should therefore also not be normalized to the OC content of the soil.

It is therefore considered justified that this value for soil is also be used for sediment. For sludge which consists mainly of organic matter the sorption data as observed for soil is not considered to be representative. In the table below the distribution constants used in this assessment is summarized:


14.4 L/kg


21.8 m3/m3


14.4 L/kg


4.5 m3/m3


14.4 L/kg


7.2 m3/m3


The distribution constants Ksoil-water, sed-water and susp-water to be used for piperazine are calculated usingEq. R.16 -7you get:

Kcomp-water=Fair*Kair-water+ Fwater comp+ Fsolidcomp* (Kdcomp/1000) * RHOsolid(Eq R16 -7)

K susp-water = 0 x 0 + 0.9 +0.1 *14.4/1000*2500 = 4.5m3/m3

K soil-water = 0.2 x 0 + 0.2 +0.6 * 14.4/1000*2500 = 21.8m3/m3


PNECsoil for Piperazine

In the absence of measured data the PNECsoil can provisionally be calculated using the equilibrium partitioning method (EPM) when a real measured sorption/desorption partitioning coefficient is used. According to the TGD this method uses the PNECaquatic and the soil/water partitioning coefficient as inputs.

The PNECsoil is calculated using the equations detailed in REACH guidance R.10 according to equation R.10 -5:

PNECsoil =   Ksoil-water* PNECaquatic * 1000 * 1 / RHOsoil


PNECaquatic dissolved            = 0.1 mg/L

Ksoil-water                              = 21.8 m3/m3

RHOsoil                                  = 1700 kg/m3(R.16 page 89)


PNECsoil-EPM = 1.28 mg/kg ww = 1.45 mg/kg dw