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1.
The solid-phase controls on the mobility of heavy metals at the Copper Cliff tailings area, Sudbury, Ontario, Canada 总被引:3,自引:0,他引:3
R. G. McGregor D. W. Blowes J. L. Jambor W. D. Robertson 《Journal of contaminant hydrology》1998,33(3-4)
The Copper Cliff Tailings Disposal Area, located near Sudbury, Ontario, covers an area of approximately 2200 ha and constitutes more than 10% of the total area of all mine tailings in Canada. The area has been utilized since 1936, receiving sulphide-containing tailings from the Inco Sudbury operations. Field measurements of pore-gas oxygen and carbon dioxide in the vadose zone indicate that sulphide oxidation has progressed to depths of 1.6 m to 1.7 m within the tailings. The oxidation of sulphide minerals within the vadose zone, and the accompanying dissolution of carbonate and aluminosilicate minerals within these tailings releases SO4, Fe(II) and other metals to the pore water. In the vadose and saturated zones, concentrations of Fe and Ni exceed 10100 mg/l and 2210 mg/l, respectively. These high concentrations of dissolved metals are attenuated by a series of precipitation, coprecipitation and adsorption reactions. The precipitation of secondary sulphate and hydroxide phases also create hardpan layers at or near the oxidation front. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary-phase precipitation is occurring at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of jarosite, gypsum and goethite within the shallow tailings, suggesting that these phases are controlling the dissolved concentrations of Fe, SO4 and Ca. Extraction experiments conducted on the tailings solids indicate that the constituents contained in the water-soluble fraction of the shallow, weathered tailings are derived from the original pore water and the dissolution of highly soluble phases such as gypsum. The acid-leachable fraction of the weathered tailings accounts for up to 25% of the heavy metals, and the reducible fraction may contain up to 100% of the heavy metals within the shallow, weathered tailings. Based on the pore water profiles and the geochemistry of the tailings solids, a relative mobility scale of Fe=Mn=Ni=Co>Cd Zn>Cr=Pb>Cu can be determined. 相似文献
2.
Synthetic musk fragrances (SMFs) have been shown to be micropollutants in various aquatic and groundwater systems, often occurring at microgram per liter concentrations. Studies have shown that the most commonly detected SMFs in water are nitro musks and polycyclic musks. The SMFs are typically introduced into the environment in continuous streams such as from wastewater and land application of wastewater or sludge generated during wastewater treatment. Various studies for the treatment of SMFs have been undertaken for wastewater but studies for the treatment of SMFs in groundwater are limited, especially for in situ treatment. A pilot‐scale test was conducted to determine if the use of colloidal activated carbon (CAC) could effectively reduce dissolved concentrations of nitro and polycyclic synthetic musk compounds including musk xylene, musk ketone, galaxolide, and tonalide. The pilot test was carried out downgradient of a septic system in Central Canada where a series of nitrification and denitrification reactions are occurring in an unconfined aquifer. A 10‐weight percent CAC solution was injected into a series of temporary direct push injection points to target the synthetic musk plume. The plume contained galaxolide and tonalide concentrations up to 687 and 187 nanograms per liter (ng/L), respectively, while the concentrations of musk ketone and musk xylene were below the method detection limit (20 ng/L). A total of 13,950 liters of CAC solution was injected during one injection event. The pilot test results indicated that the CAC was effectively delivered to the target injection zone resulting in an increase in total organic carbon concentrations within the saturated soil greater than two orders of magnitude compared to the background concentrations. Analyses of the groundwater chemistry before and post‐injection indicated that the CAC had no detrimental impact on the groundwater quality while reducing the concentration of dissolved galaxolide and tonalide within the plume to below the method detection limits within 51 days of injection with the exception of two of the 14 wells monitored which had galaxolide and tonalide concentrations up to 78 and 35 ng/L. Within 6 months of application, the concentrations of galaxolide and tonalide had decreased to below the method detection limits. Subsequent monitoring of the groundwater quality over a one‐year period failed to detect galaxolide and tonalide, suggesting that the CAC was effective in attenuating the galaxolide and tonalide. 相似文献
3.
A pilot‐scale test was conducted in a saline aquifer to determine if a petroleum hydrocarbon (PHC) plume containing benzene (B), toluene (T), ethylbenzene (E), xylenes (X), methyl tert‐butyl ether (MTBE), and tert‐butyl alcohol (TBA) could be treated effectively using a sequential treatment approach that employed in situ chemical oxidation (ISCO) and enhanced bioremediation (EBR). Chemical oxidants, such as persulfate, have been shown to be effective in reducing dissolved concentrations of BTEX (B + T + E + X) and additives such as MTBE and TBA in a variety of geochemical environments including saline aquifers. However, the lifespan of the oxidants in saline environments tends to be short‐lived (i.e., hours to days) with their effectiveness being limited by poor delivery, inefficient consumption by nontargeted species, and back‐diffusion processes. Similarly, the addition of electron acceptors has also been shown to be effective at reducing BTEX and associated additives in saline groundwater through EBR, however EBR can be limited by various factors similar to ISCO. To minimize the limitations of both approaches, a pilot test was carried out in a saline unconfined PHC‐impacted aquifer to evaluate the performance of an engineered, combined remedy that employed both approaches in a sequence. The PHC plume had total BTEX, MTBE, and TBA concentrations of up to 4,584; 55,182; and 1,880 μg/L, respectively. The pilot test involved injecting 13,826 L of unactivated persulfate solution (19.4 weight percent (wt.%) sodium persulfate (Na2S2O8) solution into a series of injection wells installed within the PHC plume. Parameters monitored over a 700‐day period included BTEX, MTBE, TBA, sulfate, and sulfate isotope concentrations in the groundwater, and carbon and hydrogen isotopes in benzene and MTBE in the groundwater. The pilot test data indicated that the BTEX, MTBE, and TBA within the PHC plume were treated over time by both chemical oxidation and sulfate reduction. The injection of the unactivated persulfate resulted in short‐term decreases in the concentrations of the BTEX compounds, MTBE, and TBA. The mean total BTEX concentration from the three monitoring wells within the pilot‐test area decreased by up to 91%, whereas MTBE and TBA mean concentrations decreased by up to 39 and 58%, respectively, over the first 50 days postinjection in which detectable concentrations of persulfate remained in groundwater. Concentrations of the BTEX compounds, MTBE, and TBA rebounded at the Day 61 marker, which corresponded to no persulfate being detected in the groundwater. Subsequent monitoring of the groundwater revealed that the concentrations of BTEX continued to decrease with time suggesting that EBR was occurring within the plume. Between Days 51 and 487, BTEX concentrations decreased an additional 84% from the concentration measured on Day 61. Mean concentrations of MTBE showed a reduction during the EBR phase of remediation of 33% while the TBA concentration appeared to decrease initially but then increased as the sulfate concentration decreased as a result of MTBE degradation. Isotope analyses of dissolved sulfate (34S and 18O), and compound‐specific isotope analysis (CSIA) of benzene and MTBE (13C and 2H) supported the conclusions that ISCO and EBR processes were occurring at different stages and locations within the plume over time. 相似文献
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5.
Chlorinated ethenes such as trichloroethene (TCE), cis‐1,2‐dichloroethene (cis‐1,2‐DCE), and vinyl chloride along with per‐ and polyfluoroalkyl substances (PFAS) have been identified as chemicals of concern in groundwater; with many of the compounds being confirmed as being carcinogens or suspected carcinogens. While there are a variety of demonstrated in‐situ technologies for the treatment of chlorinated ethenes, there are limited technologies available to treat PFAS in groundwater. At a former industrial site shallow groundwater was impacted with TCE, cis‐1,2‐DCE, and vinyl chloride at concentrations up to 985, 258, and 54 µg/L, respectively. The groundwater also contained maximum concentrations of the following PFAS: 12,800 ng/L of perfluoropentanoic acid, 3,240 ng/L of perfluorohexanoic acid, 795 ng/L of perfluorobutanoic acid, 950 ng/L of perfluorooctanoic acid, and 2,140 ng/L of perfluorooctanesulfonic acid. Using a combination of adsorption, biotic, and abiotic degradation in situ remedial approaches, the chemicals of concern were targeted for removal from the groundwater with adsorption being utilized for PFAS whereas adsorption, chemical reduction, and anaerobic biodegradation were used for the chlorinated ethenes. Sampling of the groundwater over a 24‐month period indicated that the detected PFAS were treated to either their detection, or below the analytical detection limit over the monitoring period. Postinjection results for TCE, cis‐1,2‐DCE, and vinyl chloride indicated that the concentrations of the three compounds decreased by an order of magnitude within 4 months of injection, with TCE decreasing to below the analytical detection limit over the 24‐month monitoring period. Cis‐1,2‐DCE, and vinyl chloride concentrations decreased by over 99% within 8 months of injections, remaining at or below these concentrations during the 24‐month monitoring period. Analyses of Dehalococcoides, ethene, and acetylene over time suggest that microbiological and reductive dechlorination were occurring in conjunction with adsorption to attenuate the chlorinated ethenes and PFAS within the aquifer. Analysis of soil cores collected pre‐ and post‐injection, indicated that the distribution of the colloidal activated carbon was influenced by small scale heterogeneities within the aquifer. However, all aquifer samples collected within the targeted injection zone contained total organic carbon at concentrations at least one order of magnitude greater than the preinjection total organic carbon concentrations. 相似文献
6.
Dunlop JE Horrigan N McGregor G Kefford BJ Choy S Prasad R 《Environmental pollution (Barking, Essex : 1987)》2008,151(3):621-630
Salinisation of freshwater has been identified as a serious environmental issue in Australia and around the world. Protective concentrations (trigger values) for salinity can be used to manage salinity impacts, though require locally relevant salinity tolerance information. 72-h acute salinity tolerance values were determined for 102 macroinvertebrates collected from 11 locations in four biologically distinct freshwater bio-regions in Northeast Australia and compared with sensitivities observed in Southeast Australia. The salinity tolerance of individual taxa was consistent across Northeast Australia and between Northeast and Southeast Australia. However, two distinct communities were identified in Northeast Australia using distributions of the acute tolerance values and a calculated index of salinity sensitivity. Salinity trigger values should therefore be representative of local or regionally relevant communities and may be adequately calculated using sensitivity values from throughout Eastern Australia. The results presented provide a basis for assessing salinity risk and determining trigger values for salinity in freshwater ecosystems at local and regional scales in Eastern Australia. 相似文献
7.
Sue L.T. McGregor 《Journal of Cleaner Production》2010,18(7):696-697
8.
This paper provides an overview of the emerging role of Aboriginal people in Sustainable Forest Management (SFM) in Canada over the past decade. The 1996 Royal Commission on Aboriginal Peoples (RCAP) provided guidance and recommendations for improving Aboriginal peoples' position in Canadian society, beginning with strengthening understanding and building relationships between Aboriginal and non-Aboriginal parties. This paper explores the extent to which advances in Aboriginal/non-Aboriginal relationships and Aboriginal forestry have been made as a result of RCAP's call for renewed relationships based on co-existence among nations. Such changes have begun to alter the context in which Aboriginal/non-Aboriginal relationships exist with respect to SFM. While governments themselves have generally not demonstrated the leadership called for by RCAP in taking up these challenges, industry and other partners are demonstrating some improvements. A degree of progress has been achieved in terms of lands and resources, particularly with co-management-type arrangements, but a fundamental re-structuring needed to reflect nation-to-nation relationships has not yet occurred. Other factors related to increasing Aboriginal participation in SFM, such as the recognition of Aboriginal and treaty rights, are also highlighted, along with suggestions for moving Aboriginal peoples' SFM agenda forward in the coming years. 相似文献
9.
Rick McGregor 《补救:环境净化治理成本、技术与工艺杂志》2018,28(3):33-41
Poly‐ and perfluoroalkyl substances (PFASs) have been identified by many regulatory agencies as contaminants of concern within the environment. In recent years, regulatory authorities have established a number of health‐based regulatory and evaluation criteria with groundwater PFAS concentrations typically being less than 50 nanograms per liter (ng/L). Subsurface studies suggest that PFAS compounds are recalcitrant and widespread in the environment. Traditionally, impacted groundwater is extracted and treated on the surface using media such as activated carbon and exchange resins. These treatment technologies are generally expensive, inefficient, and can take decades to reach treatment objectives. The application of in situ remedial technologies is common for a wide variety of contaminants of concern such as petroleum hydrocarbons and volatile organic compounds; however, for PFASs, the technology is currently emerging. This study involved the application of colloidal activated carbon at a site in Canada where the PFASs perfluorooctanoate (PFOA) and perfluorooctane sulfonic acid (PFOS) were detected in groundwater at concentrations up to 3,260 ng/L and 1,450 ng/L, respectively. The shallow silty‐sand aquifer was anaerobic with an average linear groundwater velocity of approximately 2.6 meters per day. The colloidal activated carbon was applied using direct‐push technology and PFOA and PFOS concentrations below 30 ng/L were subsequently measured in groundwater samples over an 18‐month period. With the exception of perfluoroundecanoic acid, which was detected at 20 ng/L and perfluorooctanesulfonate which was detected at 40 ng/L after 18 months, all PFASs were below their respective method detection limits in all postinjection samples. Colloidal activated carbon was successfully distributed within the target zone of the impacted aquifer with the activated carbon being measured in cores up to 5 meters from the injection point. This case study suggests that colloidal activated carbon can be successfully applied to address low to moderate concentrations of PFASs within similar shallow anaerobic aquifers. 相似文献
10.
Kent M. McGregor Glen A. Marotz Donald O. Whittemore 《Journal of the American Water Resources Association》1988,24(1):43-48
ABSTRACT: Drought affects the quality of ground water in certain aquifers used by municipalities in Kansas. Water quality changes occur as a function of the amount of water available for recharge and hence to dilute more mineralized ground waters. Several measures of meteorological drought, including the Palmer Index and Eagleman Aridity Index, were correlated with water quality data to determine the degree of association. Several locations showed sharp delinces in water quality as the drought progressed. These relationships can be used to predict possible variations in present and future well-water supplies in locations subject to drought induced water quality deterioration. 相似文献