Chemical speciation of Hg(II) with environmental inorganic ligands

• Complex formation between Hg(II) and the common environmental ligands Cl-, OH-, CO32-, SO42-, and PO43- can have profound effects on Hg(II) speciation in naturalwaters with low concentrations of organic matter. Hg(II) is labile, so its distribution among these inorganic ligands can be estimated by numerical modelling if reliable values for the relevant stability constants are available. A summary of critically reviewed constants and related thermodynamic data is presented. Recommended values of log(10) beta(p,q,r)(o) and the associated reaction enthalpies, Delta(r)H(m)(o), valid at I-m = 0 mol kg(-1) and 25degreesC, along with the equations and specific ion interaction coefficients required to calculate log(10) beta(p,q,r) values at higher ionic strengths and other temperatures are also presented. Under typical environmental conditions Hg(II) speciation is dominated by the reactions Hg2+ + 2Cl(-) reversible arrow HgCl2(aq) (log(10) beta(2)(o) = 14.00 +/- 0.07), Hg2+ + Cl- + H2O reversible arrow Hg(OH) Cl(aq) + H+ (log(10) beta(o) = 4.27 +/- 0.35), and Hg2+ + 2H(2)O reversible arrow Hg(OH)(2(aq)) + 2H(+) (log(10)* beta(2)(o) =- 5.98 +/- 0.06).

Nyckelord

STABILITY-CONSTANTS

METAL-IONS

COMPLEXES

CHLORIDE

ACIDS

HYDROLYSIS

PROTONS

MEDIA

CL

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)