Related Experiment Video
Updated: Jun 11, 2026
08:21
Determination of Inorganic Arsenic in a Wide Range of Food Matrices using Hydride Generation - Atomic Absorption Spectrometry.
Published on: September 1, 2017
Geochemical changes in individual sediment grains during sequential arsenic extractions.
Elisabeth Eiche1, Utz Kramar, Michael Berg
1Institute of Mineralogy & Geochemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany. elisabeth.eiche@kit.edu
Water Research
|June 29, 2010
Summary
Arsenic (As) in sediments is complex, not just determined by total amount but mineral partitioning. Micro-XRF reveals As is often bound to iron coatings, with phosphate leaching releasing significant amounts.
Area of Science:
- Environmental Science
- Geochemistry
- Analytical Chemistry
Background:
- High arsenic (As) concentrations in groundwater are a global issue.
- Dissolved As is influenced by mineral partitioning and fixation, not just total sediment content.
- Traditional sequential extraction methods lack micro-scale detail on As binding and geochemical alterations.
Purpose of the Study:
- To investigate the micro-scale distribution and binding forms of arsenic (As) in single sediment grains.
- To understand the geochemical alterations within grains during sequential extraction.
- To identify elemental associations and mineral phases involved in As fixation.
Main Methods:
- Micro-synchrotron X-ray fluorescence (μ-XRF) analysis was employed to study the micro-scale distribution of As and other elements in individual sediment grains.
- Sequential extraction techniques were simulated and analyzed at the micro-scale.
- Elemental correlations and ratios (e.g., Fe/As) were analyzed before and after leaching steps.
Main Results:
- Arsenic (As) was primarily enriched in iron (Fe) oxy-hydroxide coatings, showing strong correlations with other heavy metals.
- Phosphate leaching released 34-66% of As, accompanied by a loss of As-Fe correlation and an increased Fe/As ratio.
- Fe-leaching dissolved coatings, reducing As and Fe concentrations, with As-Fe correlation preserved only in K-associated silicate structures, indicating complex dissolution and re-precipitation.
Conclusions:
- Micro-scale analysis reveals As is predominantly associated with Fe oxy-hydroxide coatings in sediments.
- Sequential extraction can induce significant geochemical alterations, including dissolution of unintended phases and re-precipitation, affecting results.
- Understanding micro-scale As distribution and mineral associations is crucial for accurate environmental risk assessment and remediation strategies.
Related Concept Videos
00:56Extraction: Advanced Methods
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...
01:19Acid Mine Drainage
Mining activities that disturb sulfide-rich rocks, particularly those containing pyrite (FeS₂), initiate a cascade of geochemical and microbiological processes with serious environmental implications. When exposed to air and water, pyrite undergoes oxidation, releasing sulfate, ultimately forming sulfuric acid and mobilizing heavy metals into surrounding water systems. This phenomenon, known as acid mine drainage (AMD), results in low pH waters laden with toxic elements that threaten aquatic...
01:17Precipitation and Co-precipitation
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
01:21Atomic Absorption Spectroscopy: Lab
For AAS measurements, samples must be introduced as clear solutions, often requiring extensive preliminary treatment to dissolve materials like soils, animal tissues, and minerals. Common methods for sample preparation include treatment with hot mineral acids, wet ashing, combustion in closed containers, high-temperature ashing, or fusion with reagents.
Solutions containing organic solvents, such as low-molecular-mass alcohols, esters, or ketones, enhance absorbances by increasing nebulizer...
Solutions containing organic solvents, such as low-molecular-mass alcohols, esters, or ketones, enhance absorbances by increasing nebulizer...
03:46Qualitative Analysis
For solutions containing mixtures of different cations, the identity of each cation can be determined by qualitative analysis. This technique involves a series of selective precipitations with different chemical reagents, each reaction producing a characteristic precipitate for a specific group of cations. Metal ions within a group are further separated by varying the pH, heating the mixture to redissolve a precipitate, or adding other reagents to form complex ions.
For instance, group IV...
For instance, group IV...