Registration Dossier

Administrative data

Endpoint:
field studies
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles

Data source

Reference
Reference Type:
publication
Title:
Phosphate-induced lead immobilization from different lead minerals in soils under varying pH conditions
Author:
Cao X, Ma LQ, Singh SP, Zhou Q
Year:
2008
Bibliographic source:
Environ Pollut. 2008 Mar;152(1):184-92

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Four soils were used, including one Pb-contaminated soil (NC-soil) and 3 soils psiked with litharge (PbO), cerrusite (PbCO3) or anglesite (PbSO4).
Adequate P and KCl were added to the soils to facilitate the transformation of soil amount of Pb to insoluble chloropyromorphite. Samples of slurry were collected at different times.
For comparison of Pb solubility, Visual MINTEQ Program was applied to model dissolution-precipitation process of different Pb minerals and activities of Pb vs pH. Soil cation exchange capacity was determined using the method of Rhoades
GLP compliance:
not specified
Type of measurement:
Soil cation exchange: method of Rhoades (1982)
Organic matter: method of Walkley-Black procedure (Nelson and Sommers, 1982)
Lead concentrations: flame atomic absorption spectrometry of graphite furnace atomic absorption spectrometry
Mineralogical analysis: X-ray diffraction
Media:
2 soils sampled from the upper 20 cm surface at an abandoned battery-recycling site in Jacksonville, Florida, USA:
- a clean soil collected at 5-10 m away from the contaminated site
- a contaminated soil collected at the site where the total Pb concentration was 5550 mg/kg

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Any other information on results incl. tables

At low pH (3 and 5) Pb solubility followed PbO-soil > PbCO3 -soil > PbSO4 -soil; while at pH=7, it was PbSO4 -soil > PbO-soil > PbCO3 -soil.

Phosphate decreased Pb dissolution time from > 180 to < 60 min and reduced Pb solubility by 67-100 %

Applicant's summary and conclusion

Conclusions:
P addition can effectively transform various Pb minerals into insoluble chloropyromorphite in soils. This transformation was more significant at acidic conditions.
PbSO4 was the most effectively immobilized by P, followed by PbO and PbCO3..
This study clearly demonstrates the importance of the form of Pb contamination and soil pH in determining the effectiveness of Pb immoblization in soils.