TY - JOUR
T1 - Arsenic sequestration in gold mine wastes under changing pH and experimental rewetting cycles
AU - Hoagland, Beth
AU - Mosley, Luke
AU - Russo, Tess
AU - Kirby, Jason
AU - Cullen, Cecilia
AU - Fantle, Matthew S.
AU - Raven, Mark
AU - Fisher, Joshua
N1 - Funding Information:
This study was part of a broader human rights investigation and advocacy project led by Sarah Knuckey at the Columbia Law School Human Rights Clinic. The larger study was focused on the human right to water and the impacts of gold mining operations in Porgera. Findings were published in 2019 (Red Water: Mining and the Right to Water in Porgera, Papua New Guinea, https://www.law.columbia.edu/human-rights-institute/about/press-releases/Press-Release-Red-Water ). Financial support for this portion of the study was primarily provided by the National Science Foundation Graduate Research Fellowship Program [grant no. DGE1255832 ] and Graduate Research Opportunities Worldwide [NSF 16–012]. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation . Financial support was also provided by Columbia University through the Cross Cutting Initiative Grant, the Columbia Water Center, the Columbia Law School Human Rights Clinic, and the Advanced Consortium on Cooperation, Conflict, and Complexity. Additional monetary support for sample analyses was provided by CSIRO – Waite Campus, Urrbrae. Special thanks to Benjamin Hoffman at the Columbia Law School Human Rights Clinic, Claire Wright at CSIRO, as well as Matthew Gonzales, Nathaniel Warner, and Laura Liermann at The Pennsylvania State University for laboratory assistance with water analyses and mineralogical characterization. Further thanks to Susan Brantley for thoughtful discussions and feedback during the editing stages, and two anonymous reviewers for their thorough and constructive comments.
Funding Information:
This study was part of a broader human rights investigation and advocacy project led by Sarah Knuckey at the Columbia Law School Human Rights Clinic. The larger study was focused on the human right to water and the impacts of gold mining operations in Porgera. Findings were published in 2019 (Red Water: Mining and the Right to Water in Porgera, Papua New Guinea, https://www.law.columbia.edu/human-rights-institute/about/press-releases/Press-Release-Red-Water). Financial support for this portion of the study was primarily provided by the National Science Foundation Graduate Research Fellowship Program [grant no. DGE1255832] and Graduate Research Opportunities Worldwide [NSF 16?012]. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Financial support was also provided by Columbia University through the Cross Cutting Initiative Grant, the Columbia Water Center, the Columbia Law School Human Rights Clinic, and the Advanced Consortium on Cooperation, Conflict, and Complexity. Additional monetary support for sample analyses was provided by CSIRO ? Waite Campus, Urrbrae. Special thanks to Benjamin Hoffman at the Columbia Law School Human Rights Clinic, Claire Wright at CSIRO, as well as Matthew Gonzales, Nathaniel Warner, and Laura Liermann at The Pennsylvania State University for laboratory assistance with water analyses and mineralogical characterization. Further thanks to Susan Brantley for thoughtful discussions and feedback during the editing stages, and two anonymous reviewers for their thorough and constructive comments.
Publisher Copyright:
© 2020 The Authors
PY - 2021/1
Y1 - 2021/1
N2 - Arsenic (As) release related to gold mining activity can alter surface water and sediment chemistry. However, the toxicity of As in mine wastes, which is controlled by the speciation, concentration, and bioavailability of As, depends on the geochemical conditions of the impacted environment (e.g., pH, Eh, climate, mineralogy, etc). This study investigates the mechanisms of As partitioning into, or out of, streambed sediments downstream of the Porgera Gold Mine in Papua New Guinea. Mine tailings at this site are treated with lime and discharged directly into the watershed, thus making them susceptible to interaction with rain water, reducing groundwaters, or acid rock drainage if it were to develop post mine-closure. Although lime treatment increases pH and effectively triggers the precipitation of most mining-derived trace metals from wastewaters, As can become more soluble at elevated pH. We conducted batch reactor experiments to simulate the effects of changing pH (4–10) and wetting/drying cycles on As interactions with lime-treated tailings and to understand potential As behavior following mine closure. Across the pH range investigated, lime-treated waste sediments and streambed sediments located downstream of the open pit mine effectively scavenged As from the water column. Specifically, the lime-treated tailings buffered the pH and enhanced interactions between dissolved As and sediment surfaces via surface complexation reactions on amorphous iron oxides, as suggested by surface complexation modeling and batch reactor experimental results. This As scavenging mechanism further counteracted the increased solubility of As at high pH. Based on wetting/drying cycle experiments, we inferred that lime-treated tailings subjected to repeated wetting/drying cycles rapidly desorbed As during the onset of rewetting, but sorbed As via an aluminum-bridging mechanism in subsequent wetting/drying cycles. These results highlight the importance of continued lime treatment to reduce As mobility in mine wastes following mine closure, particularly for mine sites where wastes are released directly into watersheds with no containment infrastructure.
AB - Arsenic (As) release related to gold mining activity can alter surface water and sediment chemistry. However, the toxicity of As in mine wastes, which is controlled by the speciation, concentration, and bioavailability of As, depends on the geochemical conditions of the impacted environment (e.g., pH, Eh, climate, mineralogy, etc). This study investigates the mechanisms of As partitioning into, or out of, streambed sediments downstream of the Porgera Gold Mine in Papua New Guinea. Mine tailings at this site are treated with lime and discharged directly into the watershed, thus making them susceptible to interaction with rain water, reducing groundwaters, or acid rock drainage if it were to develop post mine-closure. Although lime treatment increases pH and effectively triggers the precipitation of most mining-derived trace metals from wastewaters, As can become more soluble at elevated pH. We conducted batch reactor experiments to simulate the effects of changing pH (4–10) and wetting/drying cycles on As interactions with lime-treated tailings and to understand potential As behavior following mine closure. Across the pH range investigated, lime-treated waste sediments and streambed sediments located downstream of the open pit mine effectively scavenged As from the water column. Specifically, the lime-treated tailings buffered the pH and enhanced interactions between dissolved As and sediment surfaces via surface complexation reactions on amorphous iron oxides, as suggested by surface complexation modeling and batch reactor experimental results. This As scavenging mechanism further counteracted the increased solubility of As at high pH. Based on wetting/drying cycle experiments, we inferred that lime-treated tailings subjected to repeated wetting/drying cycles rapidly desorbed As during the onset of rewetting, but sorbed As via an aluminum-bridging mechanism in subsequent wetting/drying cycles. These results highlight the importance of continued lime treatment to reduce As mobility in mine wastes following mine closure, particularly for mine sites where wastes are released directly into watersheds with no containment infrastructure.
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U2 - 10.1016/j.apgeochem.2020.104789
DO - 10.1016/j.apgeochem.2020.104789
M3 - Article
AN - SCOPUS:85097464682
VL - 124
JO - Applied Geochemistry
JF - Applied Geochemistry
SN - 0883-2927
M1 - 104789
ER -