Inorganic residual from kraft or soda pulping separated from green liquor in the chemical recovery cycle.

Endpoint summary

Additional information

Data from laboratory and field toxicity tests (plants, invertebrates or microbes) in the soil compartment for Green liquor sludge are very limited. Some studies exist demonstrating GLS effects on the growth of trees or effects of GLS on nutrition of soil and soil chemical properties. Existing test results cannot be used solely as a basis for PNECsoil derivation. One reason is that the composition of GLS can vary remarkably or composition has not been given in the study reports. Calcium carbonate may comprise 20-90% (wt) of the substance as the range given for a typical GLS composition indicates. This means that the substance may be almost pure calcium carbonate or far from it.

 

In case of GLS the major constituents, Ca and Mg carbonates and Na-, K- ions are very basic and common and expected low hazard profile constituents in soil, unless salts are not intruded to the soil in highly concentrated and alkaline form.

The ecotoxicologically more relevant constituent categories are sulfides, heavy metals and organics etc., which may actually be the key constituents in the PNEC soil derivation even if the actual concentrations may be relatively low.

Quantitative read-across can be utilised for UVCBs, typically by applying data from the key/major constituents. In practice this means grouping the constituents according to their known hazard potential in combination with their concentrations in GLS.

Leaching studies with GLS have shown that there may be a temporary increase of soluble heavy metals after application. Since the heavy metals Zn, Ni and Cu are always present in GLS, these metals can be used as (surrogate) indicators of toxicity. PNEC soil values are already available (ESR ERA (EC 793/93) evaluations) for all these metals.