Skip to main content

In situ analysis of thioarsenite complexes in neutral to alkaline arsenic sulphide solutions

Buy Article:

$13.61 plus tax (Refund Policy)


The solubility of arsenic in anoxic soil and sediment pore waters is strongly influenced by complexation with dissolved sulphide. Despite their importance in arsenic chemistry, thioarsenite complexes have not been well characterized, and considerable questions remain regarding their structure, protonation state, and relative stabilities. Here we use X-ray absorption spectroscopy to examine the type and structure of aqueous arsenic-sulphur complexes in sulphidic solutions under neutral to alkaline pH. Arsenic formed a variety of thioarsenites, including AsS(SH)(OH), As(SH)S2−2, AsS3−3 and As(SH)4 complexes. The relative fraction of each species varied strongly with the S:As ratio – with the fraction of AsS(SH)(OH) greatest at low S:As and trithioarsenites dominating As speciation when S:As ratios exceeded 3 in solution. As much as 40% of the total As also was present as AsS3S3+x(SH)−x3−x in solutions at S:As ratios of 3 or greater. Sulphide complexation was somewhat dependent on pH, with sulphide complexation generally increasing with pH. The speciation observed in these experiments is similar to, though distinct from, speciation predicted based on As2S3 solubility (inferred to contain AsS2 and AsS3S3+x(SH)−x3−x) and chromatographic separation of arsenic species (which does not identify polymeric species). Thus, these data indicate that stability constants for arsenic sulphide complexes must be reappraised.


Document Type: Research Article


Publication date: October 1, 2005

More about this publication?

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Partial Open Access Content
Partial Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more