TY - JOUR
T1 - A chromate-contaminated site in southern Switzerland - Part 1
T2 - Site characterization and the use of Cr isotopes to delineate fate and transport
AU - Wanner, Christoph
AU - Eggenberger, Urs
AU - Kurz, Daniel
AU - Zink, Sonja
AU - Mäder, Urs
PY - 2012/3
Y1 - 2012/3
N2 - The risk of groundwater contamination by chromate at a former chromite ore processing industrial site in Rivera (Switzerland) was assessed by determining subsoil Cr(VI) concentrations and tracking naturally occurring Cr(VI) reduction with Cr isotopes. Using a hot alkaline extraction procedure, a total Cr(VI) contamination of several 1000kg was estimated. Jarosite, KFe 3((SO 4) x(CrO 4) 1-x) 2(OH) 6, and chromatite (CaCrO 4) were identified as Cr(VI) bearing mineral phases using XRD, both limiting groundwater Cr(VI) concentrations. To track assumed Cr(VI) reduction at field scale δ 53Cr values of contaminated subsoil samples in addition to groundwater δ 53Cr data are used for the first time. The measurements showed a fractionation of groundwater δ 53Cr values towards positive values and subsoil δ 53Cr towards negative values confirming reduction of soluble Cr(VI) to insoluble Cr(III). Using a Rayleigh fractionation model, a current Cr(VI) reduction efficiency of approximately 31% along a 120m long flow path was estimated at an average linear groundwater velocity of 3.3m/d. Groundwater and subsoil δ 53Cr values were compared with a site specific Rayleigh fractionation model proposing that subsoil δ 53Cr values can possibly be used to track previous higher Cr(VI) reduction efficiency during the period of industrial activity. The findings strongly favor monitored natural attenuation to be part of the required site remediation measures.
AB - The risk of groundwater contamination by chromate at a former chromite ore processing industrial site in Rivera (Switzerland) was assessed by determining subsoil Cr(VI) concentrations and tracking naturally occurring Cr(VI) reduction with Cr isotopes. Using a hot alkaline extraction procedure, a total Cr(VI) contamination of several 1000kg was estimated. Jarosite, KFe 3((SO 4) x(CrO 4) 1-x) 2(OH) 6, and chromatite (CaCrO 4) were identified as Cr(VI) bearing mineral phases using XRD, both limiting groundwater Cr(VI) concentrations. To track assumed Cr(VI) reduction at field scale δ 53Cr values of contaminated subsoil samples in addition to groundwater δ 53Cr data are used for the first time. The measurements showed a fractionation of groundwater δ 53Cr values towards positive values and subsoil δ 53Cr towards negative values confirming reduction of soluble Cr(VI) to insoluble Cr(III). Using a Rayleigh fractionation model, a current Cr(VI) reduction efficiency of approximately 31% along a 120m long flow path was estimated at an average linear groundwater velocity of 3.3m/d. Groundwater and subsoil δ 53Cr values were compared with a site specific Rayleigh fractionation model proposing that subsoil δ 53Cr values can possibly be used to track previous higher Cr(VI) reduction efficiency during the period of industrial activity. The findings strongly favor monitored natural attenuation to be part of the required site remediation measures.
UR - http://www.scopus.com/inward/record.url?scp=84856623573&partnerID=8YFLogxK
U2 - 10.1016/j.apgeochem.2011.11.009
DO - 10.1016/j.apgeochem.2011.11.009
M3 - Article
SN - 0883-2927
VL - 27
SP - 644
EP - 654
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 3
ER -