Dicopper chloride trihydroxide

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Already evaluated by the Competent Authorities for Biocides and Existing Substance Regulations.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Soil properties affecting the toxicity of CuCl2 and NiCl2 for soil microbial processes in freshly spiked soils

Author:

Oorts K, U. Ghesquiere, K. Swinnen and E. Smolders

Year:

2006

Bibliographic source:

Environ Toxicol Chem., Vol. 25, No. 3, pp. 836-844, 2006

Materials and methods

Principles of method if other than guideline:

A comparative study was made using three different microbial assays (nitrification potential, glucose-induced respiration, and C-mineralisation of a plant residue) in 29 soils (for Cu) or 16 (for Ni) with contrasting soil properties.

Test material

Test material information

Constituent 1

Reference substance name:

Copper chloride

EC Number:

231-842-9

EC Name:

Copper chloride

Cas Number:

7758-89-6

Molecular formula:

ClCu

IUPAC Name:

copper (I) chloride

Test organisms

Test organisms (inoculum):

soil

Results and discussion

Effect concentrations

Dose descriptor:

other: see summary

Remarks on result:

other: see summary

Applicant's summary and conclusion

Conclusions:

Good quality study. Derived NOEC values are used for the PNEC derivation.

Executive summary:

A comparative study was made using three different microbial assays (nitrification potential, glucose-induced respiration, and C-mineralisation of a plant residue) in 29 soils (for Cu) or 16 (for Ni) with contrasting soil properties. Each soil was spiked with CuCl2 or NiCl2 at seven different concentrations, and the bioassays were started after a 7d equilibrium period. The Cu and Ni toxicity thresholds varied 19- to 90 -fold among soils. The differences in both Cu and Ni toxicity among soils were neither explained by soil solution metal concentrations nor by free ion activities calculated from soil solution composition. Copper toxicity tresholds increased with increasing organic matter content or CEC and decreased with increasing pH depending on the essay. Thresholds expressed as soil solution free ion activities all significantly decreased with increasing soil solution pH (r² = 0.57 - 0.93), consistent with a decreased H+:M²+ competition at the biological membrane. That competition largely counteracts the H+:M²+ competition for sorption, effectively explaining the insignificant or weak effect of pH on total Cu toxicity tresholds. It is concluded that free metal ion activity alone does not explain variation in metal toxicity among soils.