TY - JOUR
T1 - An investigation of mercury sources in the Puyango-Tumbes River
T2 - Using stable Hg isotopes to characterize transboundary Hg pollution
AU - Schudel, Gary
AU - Miserendino, Rebecca Adler
AU - Veiga, Marcello M.
AU - Velasquez-López, P. Colon
AU - Lees, Peter S.J.
AU - Winland-Gaetz, Sean
AU - Davée Guimarães, Jean Remy
AU - Bergquist, Bridget A.
N1 - Funding Information:
Funding for this study was provided by UNIDO , NSERC-Discovery (Bergquist RGPIN 355617-2008 ; Veiga RGPIN- 2015-04526 ), CIFAR , CNPq , and CFI-LOF . This research was also partially supported through fellowships to R. Adler Miserendino by the NSF Graduate Research Fellowship Program , the Johns Hopkins Sommer Scholarship , as well as the JSHPH EHE Student Development Fund. Thanks are also extended to Priyanaka Chandan, Wang Zheng, and Mike Gorton for assistance in the laboratory; Paul Cordy, Wilmer Niquen, Mark C. Marvin-DiPasquale for assistance with sample collection; to many at the INIGEMM for logistical support including maps, transportation, and information about the field area.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/7
Y1 - 2018/7
N2 - Mercury (Hg) concentrations and stable isotopes along with other trace metals were examined in environmental samples from Ecuador and Peru's shared Puyango-Tumbes River in order to determine the extent to which artisanal- and small-scale gold mining (ASGM) in Portovelo-Zaruma, Ecuador contributes to Hg pollution in the downstream aquatic ecosystem. Prior studies investigated the relationship between ASGM activities and downstream Hg pollution relying primarily on Hg concentration data. In this study, Hg isotopes revealed an isotopically heavy Hg signature with negligible mass independent fractionation (MIF) in downstream sediments, which was consistent with the signature observed in the ASGM source endmember. This signature was traced as far as ∼120 km downstream of Portovelo-Zaruma, demonstrating that Hg stable isotopes can be used as a tool to fingerprint and trace sources of Hg over vast distances in freshwater environments. The success of Hg isotopes as a source tracer in fresh waters is largely due to the particle-reactive nature of Hg. Furthermore, the magnitude and extent of downstream Hg, lead, copper and zinc contamination coupled with the Hg isotopes suggest that it is unlikely that the smaller artisanal-scale activities, which do not use cyanidation, are responsible for the pollution. More likely it is the scale of ores processed and the cyanide leaching, which can release other metals and enhance Hg transport, used during small-scale gold mining that is responsible. Thus, although artisanal- and small-scale gold mining occur in tandem in Portovelo-Zaruma, a distinction should be made between these two activities.
AB - Mercury (Hg) concentrations and stable isotopes along with other trace metals were examined in environmental samples from Ecuador and Peru's shared Puyango-Tumbes River in order to determine the extent to which artisanal- and small-scale gold mining (ASGM) in Portovelo-Zaruma, Ecuador contributes to Hg pollution in the downstream aquatic ecosystem. Prior studies investigated the relationship between ASGM activities and downstream Hg pollution relying primarily on Hg concentration data. In this study, Hg isotopes revealed an isotopically heavy Hg signature with negligible mass independent fractionation (MIF) in downstream sediments, which was consistent with the signature observed in the ASGM source endmember. This signature was traced as far as ∼120 km downstream of Portovelo-Zaruma, demonstrating that Hg stable isotopes can be used as a tool to fingerprint and trace sources of Hg over vast distances in freshwater environments. The success of Hg isotopes as a source tracer in fresh waters is largely due to the particle-reactive nature of Hg. Furthermore, the magnitude and extent of downstream Hg, lead, copper and zinc contamination coupled with the Hg isotopes suggest that it is unlikely that the smaller artisanal-scale activities, which do not use cyanidation, are responsible for the pollution. More likely it is the scale of ores processed and the cyanide leaching, which can release other metals and enhance Hg transport, used during small-scale gold mining that is responsible. Thus, although artisanal- and small-scale gold mining occur in tandem in Portovelo-Zaruma, a distinction should be made between these two activities.
KW - Artisanal- and small-scale gold mining
KW - Contaminant geochemistry
KW - MC-ICP-MS
KW - Mercury
KW - Mercury stable isotopes
KW - Trace metal geochemistry
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U2 - 10.1016/j.chemosphere.2018.03.081
DO - 10.1016/j.chemosphere.2018.03.081
M3 - Article
C2 - 29609178
AN - SCOPUS:85050743390
SN - 0045-6535
VL - 202
SP - 777
EP - 787
JO - Chemosphere
JF - Chemosphere
ER -