Competitive complexation of trace metals with dissolved humic acid

Y. Cao, M. Conklin, Eric Betterton

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

In this study we investigated the effects of competing trace metals and Ca2+ on Cd(II), Pb(II), and Cu(II) complexation by humic acid extracted from groundwater in Orange County, California. Two types of titration experiments were conducted, those using a single metal and those in which the humic acid had been preequilibrated with a competing metal (either a trace metal or Ca2+. The labile metal concentration in the titration was determined by differential pulse polarography (DPP). Results show the different effects of competing trace metal ions and the effect of Ca2+. Both trace metals and Ca2+ do not compete effectively with Cd(II) complexation. While no effects of Cu(II) on Pb(II) complexation were observed, the presence of Cd(II) appeared to slightly enhance the binding between Pb(II) and humic acid. The addition of Pb(II) decreased the amount of Cu(II) complexation, but Cd(II) caused a slight increase at the lower concentrations. Calcium, however, decreased the amount of complexation for all three metals. Results indicate that the metals are not necessarily competing for the same sites. Conformational changes that occur when trace metals bind to the different sites may cause this competing or enchanced effect. Since Ca(II) is introduced at two orders of magnitude higher in concentration than the trace metals, it can outcompete the trace metal for sites where electrostatic interactions dominate. The results indicate that in groundwater situations, where more than one metal is present, the effect of other metals must be considered in predicting metal speciation.

Original languageEnglish (US)
Pages (from-to)29-32
Number of pages4
JournalEnvironmental Health Perspectives
Volume103
Issue numberSUPPL. 1
StatePublished - 1995

Fingerprint

Humic Substances
Complexation
complexation
humic acid
trace metal
Metals
metal
Titration
Groundwater
Polarographic analysis
groundwater
Trace metals
Coulomb interactions
Metal ions
effect
calcium
Polarography
Calcium
ion
Static Electricity

Keywords

  • Cadmium (II)
  • Calcium
  • Complexation
  • Copper (II)
  • Humic substances
  • Lead (II)

ASJC Scopus subject areas

  • Environmental Science(all)
  • Environmental Chemistry
  • Public Health, Environmental and Occupational Health

Cite this

Competitive complexation of trace metals with dissolved humic acid. / Cao, Y.; Conklin, M.; Betterton, Eric.

In: Environmental Health Perspectives, Vol. 103, No. SUPPL. 1, 1995, p. 29-32.

Research output: Contribution to journalArticle

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