In situ metal imaging and Zn ligand-speciation in a soil-dwelling sentinel: complementary electron microprobe and synchrotron microbeam X-ray analyses

Environ Sci Technol. 2013 Jan 15;47(2):1073-81. doi: 10.1021/es302633f. Epub 2012 Dec 27.

Abstract

Understanding the relationships between accumulated metal speciation in cells and tissues of ecologically significant taxa such as earthworms will improve risk assessments. Synchrotron-based μ-focus X-ray spectroscopy was used to detect, localize, and determine ligand-speciation of Zn and Pb in thin sections of two epigeic earthworm species collected from a Pb/Zn-mine soil. The findings indicated that Zn and Pb partition predominantly as typical hard acids (i.e., strong affinities for O-donors) within liverlike chloragocytes. Moreover, Zn speciation was very similar in the chloragog and intestinal epithelia but differed subtly in the kidneylike nephridial tubules; neither Zn nor Pb was detectable in the ventral nerve cord. High resolution X-ray mapping of high pressure-frozen, ultrathin, freeze-substituted sections in a transmission electron microscope (TEM), combined with conventional TEM structural analysis, identified a new cell type packed with highly organized rough endoplasmic reticulum and containing deposits of Cd (codistributed with S); there was no evidence that these cells are major depositories of Zn or Pb. These data may be used in a systems biology approach to assist in the interpretation of metal-evoked perturbations in whole-worm transcriptome and metabolome profiles.

MeSH terms

  • Animals
  • Cadmium / analysis*
  • Cadmium / metabolism
  • Electron Probe Microanalysis
  • Environmental Monitoring
  • Lead / analysis*
  • Lead / metabolism
  • Oligochaeta / metabolism*
  • Oligochaeta / ultrastructure*
  • Soil / analysis
  • Soil Pollutants / analysis*
  • Soil Pollutants / metabolism
  • Synchrotrons
  • X-Ray Absorption Spectroscopy
  • X-Rays
  • Zinc / analysis*
  • Zinc / metabolism

Substances

  • Soil
  • Soil Pollutants
  • Cadmium
  • Lead
  • Zinc