April 2010, page 18 —We should have stated that by 2007, mass-independent fractionation of mercury isotopes had been independently observed by several groups. 1  

1.
See, for example,
T. A.
Jackson
 et al,
Appl. Geochem.
23
,
547
(
2008
)
L.
Laffont
 et al,
Environ. Sci. Technol.
43
,
8985
(
2009
);
B. A.
Bergquist
,
J. D.
Blum
,
Elements
5
,
353
(
2009
) and references therein.