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The effects of simulated dredging and flooding on the trace-element rich sediments in Lake Coeur d'Alene and the Coeur d'Alene River, Idaho Item Info

Lake Coeur d' Alene (Lake CDA) and both Main Stem (MSCDR) and South Fork of the Coeur d'Alene River (SFCDR) are contaminated with heavy metals from numerous years of mining. Possible environmental management plans in the region may include dredging and bank stability projects. Two different studies were initiated to look at potential contaminant release from proposed dredging of Lake CDA and from natural flooding events in the MSCDR and SFCDR. In the first study, an ex-situ experiment was conducted to determine how dredging releases heavy metals from contaminated lake sediments. The procedure used is as follows: 1) pore water total metal concentration, 2) total metal abundance in the organic, amorphous, crystalline and sulfidic fractions of the solid phase, 3) simulated dredging while measuring pH, Eh, and contaminant release over time, and 4) comparison of experimental data with results predicted from the MINTEQA2 speciation program. To simulate dredging operations, cores taken by gravity drilling were placed into a reaction vessel and mixed while being oxygenated for 800 hours. During the 800 h, solution As and Pb concentrations were found to be higher (0.0838 and 0.57 ppm, respectively) than the maximum contaminant levels allowed for drinking water and therefore would be detrimental to water quality within the lake. Zinc contaminant levels are of concern because they remain consistently high throughout the dredging simulation (8.3 ppm). The sediments remaining from the two dredging trials were also analyzed by selective dissolution analysis; partitioning of contaminants after dredging shifted from the organic fraction to the amorphous and crystalline metal-oxide fraction. The results suggest that management efforts that include dredging could have short-term impact on water quality in the Coeur d'Alene Basin. An environmental remediation plan is necessary to control the release of heavy metals as flooding occurs in this region. In order to address the environmental ramifications of flooding, water quality in the river system was assessed, contaminates in the riverbank sediments were geochemically phase partitioned, and their release were measured under simulated laboratory flooding experiments. To simulate flooding experiments, 18 columns were constructed allowing the sediment-water interface to be monitored for pH, Eh and dissolved concentrations of As, Fe, Mn, Pb, and Zn. These columns were subjected to two flooding events. The first event involved the addition of N2(g) and 0 2(g> purged river water to the columns and the second event also had a nutrient source (D-glucose) added to the solution in the columns. During the first event Zn was released at an average concentration of 10.41 mg/L into solution from sediment taken along the MSCDR at Cataldo, ID. For the second event, nutrient loading stimulated microbial activity which in turn increased contaminant levels drastically at all three sites; mean values of trace element contaminants from the three sites are As= 1.54, Pb = 7.57, and Zn = 79.29 mg/L. The release of contaminates due to flooding is degrading water quality in the river system and proving to be extremely detrimental to the aquatic biota. Results indicate that sediments currently situated in the riverbanks are releasing contaminants into the river system as flooding occurs and a remediation plan is necessary to eliminate this problem. In particular, extreme precaution must be used in the region to limit nutrient additions into the river system.

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Title:
The effects of simulated dredging and flooding on the trace-element rich sediments in Lake Coeur d'Alene and the Coeur d'Alene River, Idaho
Authors:
La Force, Matthew J.
Date Created (ISO Standard):
1996-12
Description:
Lake Coeur d' Alene (Lake CDA) and both Main Stem (MSCDR) and South Fork of the Coeur d'Alene River (SFCDR) are contaminated with heavy metals from numerous years of mining. Possible environmental management plans in the region may include dredging and bank stability projects. Two different studies were initiated to look at potential contaminant release from proposed dredging of Lake CDA and from natural flooding events in the MSCDR and SFCDR. In the first study, an ex-situ experiment was conducted to determine how dredging releases heavy metals from contaminated lake sediments. The procedure used is as follows: 1) pore water total metal concentration, 2) total metal abundance in the organic, amorphous, crystalline and sulfidic fractions of the solid phase, 3) simulated dredging while measuring pH, Eh, and contaminant release over time, and 4) comparison of experimental data with results predicted from the MINTEQA2 speciation program. To simulate dredging operations, cores taken by gravity drilling were placed into a reaction vessel and mixed while being oxygenated for 800 hours. During the 800 h, solution As and Pb concentrations were found to be higher (0.0838 and 0.57 ppm, respectively) than the maximum contaminant levels allowed for drinking water and therefore would be detrimental to water quality within the lake. Zinc contaminant levels are of concern because they remain consistently high throughout the dredging simulation (8.3 ppm). The sediments remaining from the two dredging trials were also analyzed by selective dissolution analysis; partitioning of contaminants after dredging shifted from the organic fraction to the amorphous and crystalline metal-oxide fraction. The results suggest that management efforts that include dredging could have short-term impact on water quality in the Coeur d'Alene Basin. An environmental remediation plan is necessary to control the release of heavy metals as flooding occurs in this region. In order to address the environmental ramifications of flooding, water quality in the river system was assessed, contaminates in the riverbank sediments were geochemically phase partitioned, and their release were measured under simulated laboratory flooding experiments. To simulate flooding experiments, 18 columns were constructed allowing the sediment-water interface to be monitored for pH, Eh and dissolved concentrations of As, Fe, Mn, Pb, and Zn. These columns were subjected to two flooding events. The first event involved the addition of N2(g) and 0 2(g> purged river water to the columns and the second event also had a nutrient source (D-glucose) added to the solution in the columns. During the first event Zn was released at an average concentration of 10.41 mg/L into solution from sediment taken along the MSCDR at Cataldo, ID. For the second event, nutrient loading stimulated microbial activity which in turn increased contaminant levels drastically at all three sites; mean values of trace element contaminants from the three sites are As= 1.54, Pb = 7.57, and Zn = 79.29 mg/L. The release of contaminates due to flooding is degrading water quality in the river system and proving to be extremely detrimental to the aquatic biota. Results indicate that sediments currently situated in the riverbanks are releasing contaminants into the river system as flooding occurs and a remediation plan is necessary to eliminate this problem. In particular, extreme precaution must be used in the region to limit nutrient additions into the river system.
Subjects:
dredging sediment heavy metals water pollution treatment
Location:
Lake Coeur d'Alene; Coeur d'Alene River
Latitude:
47.54
Longitude:
-116.82
Additional Lat-Long:
47.51, -116.15
Collection:
Coeur d'Alene Basin
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
Publisher:
University of Idaho
Contributing Institution:
University of Idaho
Type:
Text
Format:
application/pdf
Cataloger:
wbv
Date Digitized:
2012

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Preferred Citation:
"The effects of simulated dredging and flooding on the trace-element rich sediments in Lake Coeur d'Alene and the Coeur d'Alene River, Idaho", Idaho Waters Digital Library, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/iwdl/items/iwdl-cda_laforce_1996.html
Rights
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
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