Copper dinitrate

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:

Discrepance of the microbial response to elevated copper between freshly spiked and long-term contaminated soils

Author:

Oorts K, H. Bronckaers and E. Smolders

Year:

2006

Bibliographic source:

Environ Toxicol Chem., Vol. 25, No. 3, pp. 845-853, 2006

Materials and methods

Principles of method if other than guideline:

A systematic comparison of Cu toxicity thresholds was made between freshly spiked soils and soils in which elevated Cu concentrations have been present for various times.

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. The derived NOEC values were used for the PNEC derivation

Executive summary:

A systematic comparison of Cu toxicity thresholds was made between freshly spiked soils and soils in which elevated Cu concentrations have been present for various times. Three uncontaminated soils were spiked and experimentally leached or incubated outdoors for up to 18 months. Additionally, five field-contaminated soils with a 6- to 80-year-old Cu contamination were sampled, and corresponding uncontaminated soils were spiked to identical total concentrations. All soil samples were subjected to three microbial assays (nitrification potential, glucose-induced respiration, and maize residue C-mineralization). Experimental leaching or soil incubation after spiking reduced Cu toxicity (1.3- or 2.3-fold increase of dose, respectively, to inhibit process by 50% [ED50]). No significant effects of soil type, aging time (6, 12, or 18 months), or bioassay on the factor change of ED50 were found. Significant reductions of microbial activity in field-contaminated soils were only identified in 2 of the 15 series (three assays in five soils), whereas freshly spiking the corresponding control soils significantly affected these processes in 12 series. Soil solution Cu concentrations significantly decreased on leaching at corresponding total soil Cu, and smaller decreases were found during additional aging. Soil solution Cu concentrations largely explain changes in Cu toxicity on leaching and aging, although additional variation may be related to changes in the sensitivity of microbial populations. It is concluded that total Cu toxicity thresholds are lower in freshly spiked soils compared to soils in which Cu salts have equilibrated and leaching has removed excess soluble salts. The large variability of soil microbial processes creates a large uncertainty about the magnitude of the factor by which aging mitigates Cu toxicity.