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Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
Published on: February 15, 2019
Sand as a relevant fraction in geochemical studies in intertidal environments
X L Otero1, M A Huerta-Díaz, S De La Peña
1Departamento de Edafoloxía e Química Agrícola, Facultad de Bioloxía, Universidad de Santiago de Compostela, 15782, Santiago de Compostela, Spain. xl.otero@usc.es
Environmental Monitoring and Assessment
|March 26, 2013
Summary
Grain size significantly impacts trace metal retention in intertidal sediments. Fine-coarse sand fractions, often overlooked, show substantial capacity for retaining metals like lead and mercury due to mineral coatings.
Area of Science:
- Environmental Science
- Geochemistry
- Marine Geology
Background:
- Intertidal environments are susceptible to various contaminants.
- Understanding sediment's capacity to retain trace metals is crucial for environmental risk assessment.
- The role of grain size in trace metal sequestration is often underestimated.
Purpose of the Study:
- To investigate the influence of grain size on trace metal retention in contaminated intertidal sediments.
- To compare trace metal concentrations across different sediment fractions (sand, silt, clay).
- To highlight the geochemical significance of the sand fraction in metal binding.
Main Methods:
- Sediment samples were fractionated by grain size (2-0.050 mm, 0.050-0.002 mm, <0.002 mm).
- Physicochemical properties (pH, redox potential, TOC, S, Fe, Mn) and trace metals (Pb, Hg, Cr, Ni) were analyzed in bulk and fractionated samples.
- Scanning electron microscopy (SEM) was used to examine the mineralogy of sand fractions.
Main Results:
- The fine-coarse sand fraction (2-0.100 mm) exhibited high concentrations of TOC, Fe, Mn, and S.
- Trace metal concentrations in the fine-coarse sand fraction were comparable to silt and clay fractions, and higher than very fine sand.
- SEM revealed Fe oxyhydroxide and Fe sulfide coatings on sand grains, explaining enhanced metal retention.
Conclusions:
- The sand fraction plays a significant role in trace metal sequestration in intertidal sediments.
- Geochemical processes, including mineral coatings, enhance the metal-binding capacity of sand particles.
- Environmental studies should not disregard the importance of the sand fraction in sediment geochemistry.
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